Speed change device

Abstract

A transmission device (21) is provided with an input shaft (22), an output shaft (23), a planetary continuously variable transmission mechanism (24), a direct coupling mechanism (27), an idler element (28), a multi-speed transmission mechanism (26), and a controller (25). A controller (25) controls the rotational speed of a first transmission member (33) of the planetary continuously variable transmission mechanism (24) and the engagement and disengagement of a first clutch (27C) of the direct coupling mechanism (27). The controller (25) can switch the transmission device (21) to three transmission states, namely a first transmission state (stepless speed change), a second transmission state (internal lock) and a third transmission state (external lock). The controller (25) switches between a second transmission state (internal lock) and a third transmission state (external lock) in accordance with the rotational speed of the output shaft (23).

Description

Technical Field

[0001] This disclosure relates to a transmission device mounted on vehicles such as wheel loaders. Background Technology

[0002] For example, Patent Document 1 describes an engineering machine that uses a planetary continuously variable transmission (CVT) mechanism, which combines a planetary gear mechanism with an electric motor, to transmit power. The engineering machine using Patent Document 1 considers that by using a planetary CVT mechanism, sudden changes in engine rotational speed can be reduced, thereby suppressing sudden changes in the operating speed of the loading and unloading machine. Existing technical documents Patent documents

[0003] Patent Document 1: Japanese Patent Application Publication No. 2008–247269 (Japanese Patent No. 5095252) Summary of the Invention

[0004] Alternatively, a transmission device could be constructed using a planetary continuously variable transmission (CVT) and a multi-stage transmission connected to the planetary CVT. In this case, the transmission device could be configured with the following modes: a mode in which the planetary CVT continuously shifts gears while transmitting power to the multi-stage transmission; a mode in which the planetary CVT is internally locked while transmitting power to the multi-stage transmission; and a mode in which power is transmitted to the multi-stage transmission using an external locking mechanism that does not pass through the planetary CVT. However, in these modes, when switching between internal and external locking, a high load is applied to the power source, which could cause a rapid decrease in vehicle speed.

[0005] One of the objectives of this invention is to provide a speed change device that can smoothly switch between internal locking and external locking.

[0006] Preferably, the transmission device of the present invention comprises: an input shaft that rotates using a power source mounted on a vehicle; an output shaft that outputs rotation to the vehicle's driving mechanism; a planetary continuously variable transmission (CVT) mechanism disposed between the input shaft and the output shaft, which transmits rotational speed changes from the input shaft side to the output shaft side; a direct-connection mechanism that allows rotational speed changes from the input shaft side to the input shaft side, bypassing the planetary CVT mechanism; an idler gear element that mechanically connects the output side of the planetary CVT mechanism and the output side of the direct-connection mechanism; and a multi-stage transmission mechanism that, by switching the transmission path of gear meshing, enables the output side of the planetary CVT mechanism to... The rotational speed is changed in stages. The direct connection mechanism includes a direct connection clutch disposed between the input shaft and the idler gear element. The planetary continuously variable transmission mechanism includes: a planetary mechanism having three components: a first component connected to the input shaft side, a second component serving as the output side, and a third component connected to the idler gear element and serving as the output side other than the second component; a first transmission component consisting of a hydraulic rotary mechanism that performs pump or motor operation, with its rotary shaft connected to the second component of the planetary mechanism; and a second transmission component consisting of a hydraulic rotary mechanism that performs pump or motor operation, capable of being connected to the first transmission component via a pair of main pipelines for fluid flow. The transmission mechanism includes a controller that controls the rotational speed of the first transmission component and the engagement and disengagement of the direct-drive clutch. The controller can switch between three transmission states: a first transmission state, a second transmission state, and a third transmission state. In the first transmission state, the direct-drive clutch is disengaged, changing the rotational speed of the first transmission component, thereby changing the rotational speed of the second component. This allows for two degrees of freedom of rotational movement between the first component and the second and third components, transmitting power from the power source to the planetary continuously variable transmission (CVT) to the multi-stage transmission mechanism. In the second transmission state, the direct-connection clutch is disengaged, stopping the rotation of the first transmission component, thereby stopping the rotation of the second component. A rotational movement of one degree of freedom occurs between the first component, the second component, and the third component, transmitting power from the power source to the planetary continuously variable transmission mechanism to the multi-stage transmission mechanism. In the third transmission state, the direct-connection clutch is engaged, bypassing the planetary continuously variable transmission mechanism to transmit power from the power source to the direct-connection mechanism to the multi-stage transmission mechanism. The controller switches between the second and third transmission states based on the rotational speed of the output shaft.

[0007] Using this invention, the switching between internal locking (second transmission state) and external locking (third transmission state) can be performed smoothly. Attached Figure Description

[0008] Figure 1 This is a left view of a wheel loader equipped with a transmission device according to the embodiment. Figure 2 It means Figure 1 A partially cut-out side view of the transmission device. Figure 3 This is a structural diagram showing the transmission device according to the first embodiment. Figure 4 It is Figure 3 The diagram shows the internal structure of the transmission mechanism and the planetary mechanism together. Figure 5 yes Figure 4 An enlarged view of part (A) in the image. Figure 6 yes Figure 4 Enlarged view of part (B) in the image. Figure 7 This indicates the use of hydraulic equipment to construct Figure 3 A structural diagram of an example of a planetary continuously variable transmission (CVT) including the first transmission component, the second transmission component, and the power absorption device. Figure 8 From the perspective of the power source Figure 4 An explanatory diagram of the planetary structure in the image. Figure 9 It means Figure 4 Characteristic curves showing the relationship between the rotational speeds of the components of a planetary mechanism. Figure 10 It is a drive force diagram that shows the ideal relationship between the speed and traction of a wheel loader. Figure 11 This is a driving force diagram showing an example of the relationship between the speed and traction of a wheel loader (the driving force diagram of the structure in Table 1 described later). Figure 12 This is another example of a drive force diagram showing the relationship between the speed and traction of a wheel loader (the drive force diagram of the structure in Table 2 described later). Figure 13 This refers to the first variation (a structure that uses a brake for internal locking) and... Figure 3 The same structural diagram. Figure 14 This refers to the second variation (the structure where the input shaft is connected to the first solar member and the first transmission component is connected to the planetary carrier) and... Figure 4 The same structural diagram. Figure 15This refers to the third variation (the structure where the input shaft is connected to the first solar member and the first transmission component is connected to the second solar member) and... Figure 4 The same structural diagram. Figure 16 This refers to the fourth variation (the structure where the second transmission component is connected to the output shaft) and... Figure 4 The same structural diagram. Figure 17 This indicates the fifth variation (constructed using hydraulic equipment). Figure 3 Another example of the situation involving the first transmission component, the second transmission component, and the power absorption device in a planetary continuously variable transmission (CVT). Figure 7 The same structural diagram. Figure 18 This is a characteristic curve diagram illustrating the time-varying rotational speed and pressure during the switching from internal to external locking. Figure 19 This is a characteristic graph illustrating the time-varying rotational speed and pressure when switching from internal to external locking using a structure equipped with a braking mechanism. Figure 20 This is a characteristic curve diagram showing the time-varying rotational speed and pressure during the switching from external locking to internal locking. Figure 21 This is a characteristic graph illustrating the time-varying rotational speed and pressure when switching from external to internal locking using a structure equipped with a braking mechanism. Figure 22 This is a characteristic curve diagram showing the time changes in rotational speed, pressure, and reduction ratio during the transition from continuously variable transmission (CVT) to internal lock-up. Figure 23 This is a characteristic graph illustrating the time-varying rotational speed, pressure, and reduction ratio when switching from continuously variable transmission to internal lockout using a structure equipped with a braking mechanism. Figure 24 This is a characteristic curve diagram that shows the time changes in rotational speed, pressure, and reduction ratio when switching from internal lock-up to continuously variable transmission. Figure 25 This is a characteristic graph illustrating the time-varying rotational speed, pressure, and reduction ratio when switching from internal locking to continuously variable transmission using a structure equipped with a braking mechanism. Figure 26 This is a characteristic curve diagram that shows an example of the pressure change over time when switching speed stages in a multi-stage transmission mechanism. Figure 27 This is a characteristic graph illustrating the time-varying changes in pressure and rotational speed as the multi-stage transmission mechanism switches from internal locking to external locking. Figure 28 This is a characteristic graph illustrating the time-varying changes in pressure and rotational speed when switching from internal to external locking using a structure with a braking mechanism and changing the speed levels of a multi-stage transmission mechanism. Figure 29 This is a characteristic graph illustrating the time-varying changes in pressure and rotational speed as the multi-stage transmission mechanism switches from external locking to internal locking. Figure 30 This is a characteristic graph illustrating the time-varying changes in pressure and rotational speed when switching from external locking to internal locking using a structure with a braking mechanism and switching the speed levels of a multi-stage transmission mechanism. Figure 31 This is a characteristic graph showing an example of the time change of the reduction ratio when switching from internal locking to external locking and switching the speed stages of a multi-stage transmission mechanism. Figure 32 This is a characteristic graph showing an example of the time change in the reduction ratio when switching from external locking to internal locking and changing the speed level of a multi-stage transmission mechanism. Figure 33 This is a characteristic curve diagram showing an example of the time-varying reduction ratio and pressure changes when switching from continuously variable transmission (CVT) to external lock-up and switching the speed stages of a multi-stage transmission mechanism. Figure 34 This is a characteristic graph illustrating the time-varying reduction ratio and pressure when switching from external locking to continuously variable transmission and switching the speed stages of a multi-stage transmission mechanism. Figure 35 It is a characteristic curve diagram that shows the relationship between the rotation direction of the transmission component and the direction of torque (load). Figure 36 This refers to the second embodiment. Figure 4 The same structural diagram. Figure 37 yes Figure 36 Enlarged view of part (C) in the image. Figure 38 From the perspective of the power source Figure 36 An explanatory diagram of the planetary structure in the image. Figure 39 It means Figure 36 Characteristic curves showing the relationship between the rotational speeds of the three components of a planetary mechanism. Figure 40 This refers to the sixth variation (the structure where the input shaft is connected to the gear ring member and the first transmission component is connected to the planetary carrier) and... Figure 36 The same structural diagram. Figure 41 This refers to the seventh variation (the structure where the input shaft is connected to the planetary carrier and the first transmission component is connected to the gear ring component) and... Figure 36 The same structural diagram. Detailed Implementation

[0009] The following is a detailed description, taking the application of the transmission device (gearbox) according to the embodiments and variations to a vehicle (wheel loader) as an example, with reference to the accompanying drawings.

[0010] Figures 1 to 9 This refers to the first embodiment. In Figure 1 In this example, the wheel loader 1 is a representative vehicle (operating vehicle). The wheel loader 1 is configured as an articulated operating vehicle, with a front body 3 equipped with left and right front wheels 2 and a rear body 5 equipped with left and right rear wheels 4 connected in a folding manner in the left-right direction. That is, the front body 3 and the rear body 5 constitute the body of the wheel loader 1. A central hinge 6 and a steering cylinder (not shown) are provided between the front body 3 and the rear body 5. By extending or retracting the steering cylinder, the front body 3 and the rear body 5 fold in the left-right direction around the central hinge 6. Thus, the wheel loader 1 can steer while driving.

[0011] The loading / unloading machine 7, also known as a working device, is mounted on the front body 3 of the wheel loader 1 and is capable of pitching. The loading / unloading machine 7 includes a loading hopper 7A. On the other hand, the rear body 5 of the wheel loader 1 includes a cab 8 (which serves as the driver's cab), an engine 9, a hydraulic pump 10, and a transmission device 21 (which serves as a gearbox). Inside the cab 8 are an accelerator pedal 8A, which is an operating component for accelerating the vehicle; and a forward / reverse shift lever 8B (hereinafter referred to as the FNR lever 8B), which switches between forward, reverse, and gear shifting stages of the vehicle. In addition, although not shown in the figure, the cab 8 includes a driver's seat, a steering wheel, a brake pedal, and a parking brake switch.

[0012] An operation quantity detector 8C is installed on the accelerator pedal 8A to detect the operation quantity θ1 of the accelerator pedal 8A. The operator operates the FNR lever 8B to switch the wheel loader 1 between forward and reverse, and to switch the transmission levels. To move the wheel loader 1 forward, the operator switches the FNR lever 8B to the forward position (F). To move the wheel loader 1 backward, the operator switches the FNR lever 8B to the reverse position (R). To keep the wheel loader 1 stationary, or to stop the wheel loader 1 while it is in motion, the operator switches the FNR lever 8B to the neutral position (N). When switching transmission levels, the operator rotates the FNR lever 8B around its axis.

[0013] Engine 9 is the power source (prime mover) of wheel loader 1. The power source can be composed solely of engine 9, which is an internal combustion engine, or, for example, of an engine and an electric motor, or solely of an electric motor. Hydraulic pump 10 is connected to engine 9. Hydraulic pump 10 is the hydraulic source used to operate the loading / unloading machine 7. (As described later...) Figure 3 As shown, the hydraulic pump 10 is connected to the engine 9 via gears 10A and 10B.

[0014] A front axle 12 extending in a left-right direction is provided on the lower side of the front body 3. Left and right front wheels 2 are installed on both ends of the front axle 12. On the other hand, a rear axle 13 extending in a left-right direction is provided on the lower side of the rear body 5. Left and right rear wheels 4 are installed on both ends of the rear axle 13.

[0015] The front axle 12 is connected to the transmission 21 via the front driveshaft 14. The rear axle 13 is connected to the transmission 21 via the rear driveshaft 15. The transmission 21 transmits the rotational speed (increases and / or decreases) of the engine 9 to the front driveshaft 14 and the rear driveshaft 15 in a variable manner. That is, the power from the engine 9 is transmitted to the transmission 21 connected to the engine 9.

[0016] The power from engine 9, after its speed and direction of rotation are adjusted by transmission 21, is transmitted from the output shafts 23A and 23B of transmission 21 to the front axle 12 and rear axle 13 via front drive shaft 14 and rear drive shaft 15. That is, as... Figure 2 As shown, the transmission device 21 includes an input shaft 22 connected to the engine 9, a front output shaft 23A connected to the front drive shaft 14, and a rear output shaft 23B connected to the rear drive shaft 15. The transmission device 21 switches the transmission path within the transmission device 21, thereby changing speed between the input shaft 22 and the output shafts 23A and 23B, as well as switching between forward and reverse rotation.

[0017] Here, Figure 10 This diagram shows the ideal drive force lines of the wheel loader 1. Figure 10 In the middle, the ideal driving force line L represents the direction of forward movement. f The ideal driving force line L in the backward direction (reverse direction) r When moving forward, it seeks high traction for digging and high speed (0 km / h to 40 km / h) for returning. Furthermore, the wheel loader 1 needs to climb slopes of varying gradients, such as those found in quarries. Therefore, for example, at speeds above 3 km / h, it is best to maintain a constant horsepower traction regardless of the speed.

[0018] Figure 10The range A in the text represents the range of traction required for excavation, that is, the range A of the driving force line during excavation. Figure 10 The range B in the equation represents the range within which a constant horsepower traction force is sought regardless of vehicle speed; that is, the range B of the constant horsepower driving force line in the forward direction. Figure 10 In this context, range C represents the range of traction force that aims for constant horsepower regardless of vehicle speed, i.e., the range C of the constant horsepower driving force line in the backward direction.

[0019] like Figure 3 as well as Figure 4 As shown, the transmission device 21 according to the first embodiment includes a planetary continuously variable transmission (CVT) mechanism 24, a direct connection mechanism 27, and a multi-stage transmission mechanism 26. In this case, the transmission device 21 has a mode in which power is transmitted to the multi-stage transmission mechanism 26 while the planetary CVT mechanism 24 performs continuously variable transmission, a mode in which power is transmitted to the multi-stage transmission mechanism 26 with the planetary CVT mechanism 24 locked internally, and a mode in which power is transmitted to the multi-stage transmission mechanism 26 without passing through the external locking mechanism (direct connection mechanism 27) of the planetary CVT mechanism 24. Power transmission by internal locking is performed by stopping the rotation of the component (e.g., the first sun gear 29B) of the three components (e.g., the planet carrier 29A, the first sun gear 29B, and the second sun gear 29C) of the planetary gear mechanism 29 constituting the planetary CVT mechanism 24 that is connected to the first transmission member 33.

[0020] On the other hand, power transmission via external locking is performed through an external locking mechanism (direct connection mechanism 27) mounted outside the planetary continuously variable transmission 24. In this case, power transmission via external locking is performed while power transmission by the planetary continuously variable transmission 24 has stopped. This stop is achieved by disengaging the component (e.g., the first sun gear 29B) connected to the first transmission component 33 from the three components of the planetary gear mechanism 29 (e.g., the planet carrier 29A, the first sun gear 29B, and the second sun gear 29C) (or by reducing torque).

[0021] Furthermore, according to the first embodiment, such as Figure 4 , Figure 5 as well as Figure 8 As shown, the planetary gear mechanism 29 of the planetary continuously variable transmission 24 includes two sun gears 29B and 29C, a planet gear 29D, a balance gear 29E, and a planet carrier 29A. The planet gears 29D and the balance gear 29E are positioned around the central axis S of the two sun gears 29B and 29C. Figure 8The planet carrier 29A revolves around the sun gears 29B and 29C while rotating on its own axis. The planet carrier 29A supports the planet gears 29D and 29E so that they can rotate, and rotates on its own axis around the central axis S of the two sun gears 29B and 29C.

[0022] The transmission device 21 according to the first embodiment will now be described in detail. Furthermore, in Figure 3 In the diagram, a square box (rectangular frame) represents the planetary gear mechanism 29 of the transmission device 21. In contrast, in... Figure 4 The interior of the planetary gear mechanism 29 is also shown, specifically the gear arrangement of the planetary gear mechanism 29. Furthermore, in Figure 3 as well as Figure 4 In order to avoid complicating the diagram, the output shaft 23 of the transmission device 21 is simplified as a shared output shaft 23 (=output shafts 23A, 23B) that transmits power to both the front axle 12 and the rear axle 13. That is, in Figure 3 as well as Figure 4 The structure that distributes power to the front output shaft 23A and the rear output shaft 23B via a central differential mechanism is omitted. (The following will be discussed...) Figure 7 The same applies. Additionally, in Figure 7 The hydraulic pump 10 and gears 10A and 10B are also omitted.

[0023] Figure 3 as well as Figure 4 This is a structural diagram of a transmission device 21 according to the first embodiment, and more specifically, a transmission device 21 having both internal and external locking mechanisms. The transmission device 21 includes an input shaft 22 as an input member, an output shaft 23 as an output member, a planetary continuously variable transmission (CVT) mechanism 24 as a continuously variable transmission (CVT) mechanism (main transmission mechanism), and a controller 25. Furthermore, the transmission device 21 includes a multi-stage transmission mechanism 26 as a stepped transmission mechanism (secondary transmission mechanism) and a direct-connection mechanism 27 as an external locking mechanism. The direct-connection mechanism 27 includes a first clutch 27C that connects during power transmission via the direct-connection mechanism 27.

[0024] Furthermore, the transmission device 21 includes idler gear elements 28 (idler shaft 28A, first idler gear 28B, and second idler gear 28C) that mechanically connect the planetary continuously variable transmission mechanism 24, the multi-stage transmission mechanism 26, and the direct connection mechanism 27. Additionally, as described later... Figure 7 As shown, the transmission device 21 includes a first speed detector 49, a second speed detector 50, a first pressure detector 51, a second pressure detector 52, and a third pressure detector 53.

[0025] The input shaft 22 of the transmission 21 is rotated by the engine 9, which serves as the power source (prime mover) mounted on the vehicle (wheel loader 1). That is, the input shaft 22 is connected to the drive shaft of the engine 9. A gear 10B for transmitting power to the hydraulic pump 10 is provided on the input shaft 22. Additionally, an input gear 27A of a direct-connection mechanism 27 is provided on the input shaft 22. The input shaft 22 is connected to the planetary continuously variable transmission mechanism 24 (more specifically, the planetary gear mechanism 29) via a first connecting member 30. On the other hand, power is output from the output shaft 23 of the transmission 21. The output shaft 23 of the transmission 21 also serves as the output shaft 77 of the multi-stage transmission mechanism 26, described later. The output shaft 23 outputs rotation to the front wheels 2 and / or the rear wheels 4 via the front axle 12 and / or the rear axle 13 of the wheel loader 1.

[0026] The power input from the input shaft 22 to the transmission device 21 is transmitted to the idler gear element 28 via the planetary continuously variable transmission mechanism 24 or the direct connection mechanism 27. The power transmitted to the idler gear element 28 is output from the output shaft 23 via the multi-stage transmission mechanism 26. The planetary continuously variable transmission mechanism 24 is disposed between the input shaft 22 and the output shaft 23 (specifically, between the input shaft 22 and the multi-stage transmission mechanism 26, and more specifically, between the input shaft 22 and the idler gear element 28). The planetary continuously variable transmission mechanism 24 changes the rotational speed on the input shaft 22 side and transmits it to the output shaft 23 side. The input side of the planetary continuously variable transmission mechanism 24 is connected to the input shaft 22, which is equipped with the input gear 27A of the direct connection mechanism 27. The output side of the planetary continuously variable transmission mechanism 24 is connected to the idler gear shaft 28A of the idler gear element 28.

[0027] Furthermore, the planetary continuously variable transmission 24 achieves an internally locked state by stopping the second connecting member 31 that connects the planetary gear mechanism 29 (e.g., the first sun gear 29B) and the first transmission component 33. This internal locking state is achieved, for example, by stopping the second connecting member 31 through a braking operation of the first transmission component 33. The braking operation of the first transmission component 33 will be described later. When the planetary continuously variable transmission 24 is internally locked, the power input from the input shaft 22 is transmitted to the idler gear element 28 (first idler gear 28B) via the "first connecting member 30 that connects the planetary gear mechanism 29 (e.g., the planet carrier 29A) and the input shaft 22", the "planetary gear mechanism 29", and the "third connecting member 32 that connects the planetary gear mechanism 29 (e.g., the second sun gear 29C) and the idler gear element 28".

[0028] In the first embodiment, as the transmission path for transmitting power from the engine 9 to the input shaft 22 to the multi-stage transmission mechanism 26, the transmission device 21 can arbitrarily select from the following three paths (A), (B), and (C). (A) When the planetary continuously variable transmission 24 is continuously variable, the power input from the engine 9 to the input shaft 22 is transmitted to the continuously variable transmission path (first transmission path) of the multi-stage transmission mechanism 26. At this time, the first clutch 27C, which is a direct-connection clutch, is disengaged, and the second clutch 36 and the third clutch 37 of the planetary continuously variable transmission 24 are engaged. The state of transmitting power through the continuously variable transmission path is defined as the first transmission state. (B) With the planetary continuously variable transmission 24 internally locked, the power input from the engine 9 to the input shaft 22 is transmitted to the internal lock-up path (second transmission path) of the multi-stage transmission 26. At this time, the first clutch 27C, which is a direct-connection clutch, disengages, and the second clutch 36 of the planetary continuously variable transmission 24 engages. The third clutch 37 is engaged as needed. The state of transmitting power via the internal lock-up path is designated as the second transmission state. (C) Power input from engine 9 to input shaft 22 is transmitted via direct coupling mechanism 27 to the external lock-up path (third transmission path) of multi-stage transmission mechanism 26. This external lock-up path is the transmission path via direct coupling mechanism 27 without passing through planetary continuously variable transmission mechanism 24. At this time, the first clutch 27C, which becomes the direct coupling clutch, is engaged (connected), and the second clutch 36 and the third clutch 37 of planetary continuously variable transmission mechanism 24 are disengaged as needed. The state of transmitting power via the external lock-up path is defined as the third transmission state.

[0029] In this embodiment, when it is suitable for the planetary continuously variable transmission (CVT) 24 to perform continuously variable transmission, the planetary CVT 24 is used for power transmission through continuously variable transmission. When it is suitable for the planetary CVT 24 to be internally locked, the planetary CVT 24 is internally locked for power transmission. When it is suitable for power transmission via the direct connection mechanism 27, power transmission is performed via the direct connection mechanism 27.

[0030] Table 1 below shows the combinations of transmission paths for the transmission device 21, which has both internal and external locking. In this case, the multi-stage transmission mechanism 26 has three forward gears and one backward gear. That is, the multi-stage transmission mechanism 26 can select one forward gear, two forward gears, three forward gears, and one backward gear.

[0031] [Table 1]

[0032] As shown in Table 1, when driving forward, the transmission settings at lower vehicle speeds follow the sequence of "forward 1st gear continuously variable transmission (CVT)," "forward 1st gear internal lock," "forward 1st gear external lock," "forward 2nd gear internal lock," "forward 2nd gear external lock," "forward 3rd gear internal lock," and "forward 3rd gear external lock." When driving backward, the transmission settings follow the sequence of "rear gear continuously variable transmission (CVT)," "rear gear internal lock," and "rear gear external lock."

[0033] Figure 11 A diagram showing the driving force lines of the transmission device 21 with the transmission states shown in Table 1. (See diagram for example.) Figure 11 As shown, the forward gear can be shifted to 1st gear via a continuously variable transmission (CVT) L. f1 1. Forward 1st gear internal lock L f2 1. Forward 1st gear external lock L f3 2nd gear forward, internal lock-up L f4 2nd gear forward, external lock L f5 3rd gear forward, internal lock-up L f6 3rd gear forward with external lock L f7 The speed is changed in 7 stages.

[0034] On the other hand, the rear-mounted gear can be moved to 1st gear continuously variable transmission (CVT). r1 1st gear internal lock L r2 1st gear with external lock-up L r3 The transmission device 21, which has the transmission states shown in Table 1, can obtain high traction when starting in the backward direction, can obtain high vehicle speed (0 km / h to 16 km / h) when transporting and returning, and can stably climb slopes with varying gradients.

[0035] Alternatively, when the speed level of the multi-speed transmission mechanism 26 is forward 2nd gear and / or forward 3rd gear, a continuously variable transmission (CVT) operation can be set. For example, a combination of transmission paths as shown in Table 2 below can also be used.

[0036] [Table 2]

[0037] As shown in Table 2, when driving forward, the transmission state can be set from a lower speed state in the following sequence: "Forward 1st Gear CVT", "Forward 1st Gear Internal Lock", "Forward 1st Gear External Lock", "Forward 2nd Gear CVT", "Forward 2nd Gear Internal Lock", "Forward 2nd Gear External Lock", "Forward 3rd Gear CVT", "Forward 3rd Gear Internal Lock", and "Forward 3rd Gear External Lock". The same applies when driving forward in subsequent gears.

[0038] Figure 12This is a diagram showing the driving force lines of the transmission device 21 with the transmission states shown in Table 2. (See diagram for example.) Figure 12 As shown, the forward gear can be shifted to 1st gear via a continuously variable transmission (CVT) L. f1 1. Forward 1st gear internal lock L f2 1. Forward 1st gear external lock L f3 2-speed continuously variable transmission (CVT) f4 2nd gear forward, internal lock-up L f5 2nd gear forward, external lock L f6 3-speed continuously variable transmission (CVT) L f7 3rd gear forward, internal lock-up L f8 3rd gear forward with external lock L f9 These 9 stages involve speed changes.

[0039] Set forward 2-speed continuously variable transmission (CVT) L f4 And forward 3-speed continuously variable transmission (CVT L) f7 The advantage lies in changing the transmission state from forward 2 gears to continuously variable transmission (CVT L). f4 Change to forward 1st gear with external lock-up (L) f3 At that time, and when changing the transmission state from forward 3rd gear continuously variable transmission (CVT L) f7 Change to forward 2nd gear with external lock L f6 At that time, the transmission device 21 transmits the same speed as... Figure 12 The L shown f To save fuel, when the traction force is above 70% of the corresponding vehicle speed, wheel loader 1 preferably does not use the forward 2nd gear continuously variable transmission (CVT). f4 and forward 3-speed continuously variable transmission (CVT L) f7 This is because, in continuously variable transmission (CVT) mode, the transmission efficiency of the transmission device 21 is worse than in the internal or external lock-up modes.

[0040] On the other hand, the transmission device 21 transmits the same speed as L. f When the traction force is below 40% of the corresponding vehicle speed, it is preferable to use the forward 2nd gear continuously variable transmission (CVT) L to save fuel. f4 and forward 3-speed continuously variable transmission (CVT L) f7 This is because, although the transmission efficiency of the transmission 21 is worse in continuously variable transmission (CVT) mode than in internal or external lock-up mode, the efficiency of the engine 9, as the power source, decreases further. In this case, by reducing the rotational speed of the engine 9 to increase its efficiency, the overall efficiency of the transmission 21 and the engine 9 can be improved. Specifically, when the transmission 21 transmits power in a speed range of 0 km / h to 16 km / h, the efficiency of the transmission 9 is further reduced. f When the traction force is less than 40% of the corresponding vehicle speed, a 3-speed continuously variable transmission (CVT) can save fuel. When the vehicle speed is between 0 km / h and 9 km / h, the transmission 21 transmits the same torque as L. fWhen the traction force is less than 40% of the corresponding vehicle speed, using a continuously variable transmission (CVT) in second gear can save fuel.

[0041] Next, refer to Figure 3 The planetary continuously variable transmission (CVT) 24 is described below. The planetary CVT 24 includes a planetary gear mechanism 29 (which is a planetary mechanism), a first transmission component 33, a second transmission component 34, a transmission element 35, a second clutch 36, and a third clutch 37. The planetary gear mechanism 29 is connected to the input side (engine 9 side) via a first connecting member 30. The planetary gear mechanism 29 is connected to the first output side (first transmission component 33 side) via a second connecting member 31. The planetary gear mechanism 29 is connected to the second output side (idler element 28 side) via a third connecting member 32.

[0042] The first transmission unit 33 and the second transmission unit 34 are composed of an electric motor and a generator (electric motor, electric generator) or a hydraulic pump and a motor (hydraulic pump, hydraulic motor). Specifically, when the first transmission unit 33 is composed of an electric motor (electric generator), the second transmission unit 34 is composed of an electric generator (electric motor). When the first transmission unit 33 is composed of a hydraulic pump (hydraulic motor), the second transmission unit 34 is composed of a hydraulic motor (hydraulic pump). As will be described later. Figure 7 As shown, in the embodiment, the first speed change unit 33 and the second speed change unit 34 are constructed using a hydraulic pump motor (a hydraulic rotary machine that performs pump or motor operation, more specifically a hydraulic rotary machine).

[0043] The first transmission unit 33 (hereinafter also referred to as the first hydraulic pump motor 33) and the second transmission unit 34 (hereinafter also referred to as the second hydraulic pump motor 34) are configured to enable stepless speed change and power transmission between the two when the rotational speed of the first transmission unit 33 differs from that of the second transmission unit 34. For this purpose, a transmission element 35 for transmitting power between the first transmission unit 33 and the second transmission unit 34 is provided. The transmission element 35 is, for example, constituted by electrical wiring or hydraulic piping. Figure 7 As shown, in the embodiment, a transmission element 35 is constructed using a pair of main lines 35A and 35B (first main line 35A and second main line 35B).

[0044] A power absorption device 38 is provided midway through the transmission element 35. The power absorption device 38 is a device for absorbing (processing or storing) power. The power absorption device 38 absorbs (processes or stores) the power from the first transmission unit 33 that exceeds the power that the second transmission unit 34 can fully handle. In addition, the power absorption device 38 absorbs (processes or stores) the power from the second transmission unit 34 that exceeds the power that the first transmission unit 33 can fully handle.

[0045] The power absorption device 38, for example, as a power storage device (power storage device), can be composed of an accumulator or a storage device (battery). Alternatively, the power absorption device 38, for example, as a power processing device (power processing device), can be composed of a connecting valve (overflow valve, on / off valve) or a resistive device (resistor). Figure 7 As shown, in this embodiment, the power absorption device 38 is constructed using variable relief valves 38A and 38B (the first variable relief valve 38A and the second variable relief valve 38B). Furthermore, the functions of the first transmission component 33, the second transmission component 34, and the transmission element 35 can also be provided by an infinitely variable transmission (IVT). Additionally, if the first transmission component 33 and the second transmission component 34 are electric motor generators, they can be configured to include an inverter and a converter, as needed.

[0046] A second clutch 36 is provided between the planetary gear mechanism 29 and the first transmission component 33, that is, between the second connecting member 31 and the first transmission component 33. The second clutch 36 is, for example, a clutch (friction plate) obtained through frictional engagement, a claw clutch, or a claw clutch with a synchronizing engagement. The second clutch 36 performs the mechanical engagement and disengagement of the second connecting member 31 and the first transmission component 33. In other words, the second clutch 36 switches the transmission and disengagement of power between the planetary gear mechanism 29 and the first transmission component 33.

[0047] The controller 25 is configured, for example, as a microcomputer including an arithmetic circuit (CPU) and memory. The controller 25 controls the engagement and disengagement of the first clutch 27C, the second clutch 36, and the third clutch 37. The controller 25 controls the rotational speed of the first transmission unit 33. The controller 25 controls the rotational speed of the second transmission unit 34. The controller 25 controls the power absorption device 38 (variable relief valves 38A and 38B). The controller 25 controls the braking mechanism 55 (described later) as needed. Figure 13 In addition, the controller 25 controls the engagement and disengagement of the forward 1st gear clutch 69, the backward 1st gear clutch 70, the forward 2nd gear clutch 75, and the forward 3rd gear clutch 76 of the multi-stage transmission mechanism 26, which will be described later.

[0048] Here, the controller 25 controls the engagement and disengagement of the second clutch 36. For example, when power transmission via the planetary continuously variable transmission 24 is not required, the controller 25 outputs a signal to disengage the second clutch 36, thereby disengaging the second clutch 36. As a result, the rotation of the first transmission component 33 can be stopped (or lowered), reducing power loss caused by the rotation of the first transmission component 33.

[0049] The second transmission component 34 is connected to the idler gear element 28 via the third clutch 37. The third clutch 37 switches the transmission and disengagement of power between the second transmission component 34 and the idler gear element 28. That is, the third clutch 37 is located between the second transmission component 34 and the idler gear element 28. The idler gear element 28 includes an idler shaft 28A and a first idler gear 28B and a second idler gear 28C disposed on the idler shaft 28A. The idler shaft 28A is connected to the locking gear 27B (more specifically, the rotating shaft 27B1 of the locking gear 27B) of the direct connection mechanism 27 via the first clutch 27C.

[0050] Furthermore, the idler shaft 28A is connected to the second transmission component 34 via the transmission 39 and the third clutch 37. The first idler gear 28B meshes with the third connecting member 32 and is connected to the planetary gear mechanism 29 via the third connecting member 32. Additionally, the first idler gear 28B meshes with the countershaft gear 64 (rear forward 1st gear 67) and the forward 3rd gear 73 of the multi-stage transmission mechanism 26. Furthermore, the second idler gear 28C meshes with the forward 1st gear 66 and the forward 2nd gear 72 of the multi-stage transmission mechanism 26. Thus, the first idler gear 28B and the second idler gear 28C are connected to the multi-stage transmission mechanism 26.

[0051] A gearbox 39 is provided between the second gearbox 34 and the idler element 28 (idler shaft 28A) to change speeds between the two. This gearbox 39 may be omitted. In this case, a third clutch 37 can be provided between the idler shaft 28A of the idler element 28 and the rotating shaft (second rotating shaft 43) of the second gearbox 34, and the third clutch 37 is used to engage (connect) and disengage the idler shaft 28A from the rotating shaft of the second gearbox 34.

[0052] The third clutch 37 is, for example, a clutch (friction plate) formed by frictional engagement, a claw clutch, or a claw clutch with a synchronizing engagement. The third clutch 37 mechanically engages and disengages the second transmission component 34 and the idler wheel element 28. The controller 25 controls the engagement and disengagement of the third clutch 37. For example, when power transmission through the second transmission component 34 is not required, the controller 25 outputs a signal to disengage the third clutch 37, thereby disengaging it. This stops (or lowers) the rotation of the second transmission component 34, reducing power loss caused by its rotation. It should be noted that disengaging the third clutch 37 is not always necessary under the aforementioned conditions.

[0053] The power transmitted from engine 9 to the first connecting structure 30 is distributed by planetary gear mechanism 29 to the second connecting structure 31 connected to the first transmission component 33 and the third connecting structure 32 connected to the idler gear element 28. The power distributed to the second connecting structure 31 is transmitted to the idler gear element 28 via the second clutch 36, the first transmission component 33, the transmission element 35, the second transmission component 34, the third clutch 37, and the transmission 39. The power distributed to the third connecting structure 32 is also transmitted to the idler gear element 28. The torque distribution ratio between the second connecting structure 31 and the third connecting structure 32 remains constant, depending on the form of planetary gear mechanism 29 and the meshing radius of the gears.

[0054] It should be noted that since the torque distribution ratio between the second and third connecting components 31 and 32 is fixed, power is not always transmitted from the first transmission component 33 to the second transmission component 34; sometimes power is transmitted from the second transmission component 34 to the first transmission component 33. The power loss transmitted from the third connecting component 32 to the idler gear element 28 is less than the power loss transmitted from the second connecting component 31 via the first and second transmission components 33 and 34. Therefore, compared to a continuously variable transmission (CVT) that only uses transmission components for power transmission, the planetary CVT 24, which combines transmission components 33 and 34 with the planetary gear mechanism 29, has higher transmission efficiency.

[0055] Figure 7 This describes the specific structure of the first transmission component 33, the second transmission component 34, the transmission element 35, and the power absorption device 38. For example... Figure 7 As shown, the planetary continuously variable transmission (CVT) 24 includes a planetary gear mechanism 29, a hydrostatic CVT 41, a second clutch 36, and a third clutch 37. The hydrostatic CVT 41 includes a first rotating shaft 42, a first hydraulic pump motor 33 corresponding to the first transmission component 33, a pair of main pipelines 35A and 35B (first main pipeline 35A and second main pipeline 35B) corresponding to the transmission element 35, a second hydraulic pump motor 34 corresponding to the second transmission component 34, a second rotating shaft 43, variable relief valves 38A and 38B (first variable relief valve 38A and second variable relief valve 38B) corresponding to the power absorption device 38, a connecting pipeline 44, bypass pipelines 45 and 46, and check valves 47 and 48.

[0056] The first rotating shaft 42 corresponds to the input shaft of the hydrostatic continuously variable transmission (CVT) 41. The first rotating shaft 42 also corresponds to the rotating shaft of the first hydraulic pump motor 33. The second rotating shaft 43 corresponds to the output shaft of the hydrostatic CVT 41. The second rotating shaft 43 also corresponds to the rotating shaft of the second hydraulic pump motor 34. The first hydraulic pump motor 33 is connected to the output side of the planetary gear mechanism 29 via the second clutch 36. The first hydraulic pump motor 33 drives the rotation of the first rotating shaft 42, causing pressurized oil to flow within a pair of main pipelines 35A and 35B.

[0057] The first hydraulic pump motor 33 is, for example, a variable capacity type hydraulic pump motor (hydraulic rotary machine) of swashplate or swashplate type. The first hydraulic pump motor 33 functions as a hydraulic pump when power is input from the first rotating shaft 42, and as a hydraulic motor when power is output to the first rotating shaft 42. The first hydraulic pump motor 33 has a regulator 33A for adjusting the capacity (pump capacity and motor capacity). The regulator 33A is based on commands (command signal W) from the controller 25. P It can be controlled in a variable manner.

[0058] A pair of main pipelines 35A and 35B connect a pair of inlet / outlet ports of the first hydraulic pump motor 33 to a pair of inlet / outlet ports of the second hydraulic pump motor 34. The second hydraulic pump motor 34 is connected to the first hydraulic pump motor 33 via a pair of main pipelines 35A and 35B (first main pipeline 35A and second main pipeline 35B). The second hydraulic pump motor 34 is rotated by pressurized oil supplied from the first hydraulic pump motor 33. The second hydraulic pump motor 34 is connected to the idler element 28 (idler shaft 28A) via a third clutch 37 and a gearbox 39. The second hydraulic pump motor 34 drives the rotation of the second rotating shaft 43, causing pressurized oil to flow within the pair of main pipelines 35A and 35B.

[0059] The second hydraulic pump motor 34 is, for example, a variable capacity type hydraulic pump motor (hydraulic rotary machine) that is either swashplate type or swashplate type. The second hydraulic pump motor 34 functions as a hydraulic motor when outputting power to the second rotating shaft 43, and as a hydraulic pump when inputting power from the second rotating shaft 43. The second hydraulic pump motor 34 has a regulator 34A for adjusting the capacity (motor capacity and pump capacity). The regulator 34A is based on commands (command signal W) from the controller 25. M It can be controlled in a variable manner.

[0060] The hydrostatic continuously variable transmission (CVT) 41 includes: variable relief valves 38A and 38B capable of changing the set pressure (overflow set pressure and overflow start pressure); and check valves 47 and 48 that allow the flow of pressurized oil in one direction and prevent the flow of pressurized oil in the opposite direction. Specifically, the first main pipeline 35A and the second main pipeline 35B of the hydrostatic CVT 41 are connected by a connecting pipeline 44. Power is transmitted between the first hydraulic pump motor 33 and the second hydraulic pump motor 34 by allowing working oil to flow between them via a pair of main pipelines 35A and 35B. For example, when the rotational speed is changed on the input shaft 22 side and transmitted to the output shaft 23 side, the pressure in the first main pipeline 35A becomes higher than that in the second main pipeline 35B. Similarly, for example, when the rotational speed is changed on the output shaft 23 side and transmitted to the input shaft 22 side, the pressure in the second main pipeline 35B becomes higher than that in the first main pipeline 35A. A pair of check valves 47 and 48 are installed in the connecting pipe 44 between the first main pipe 35A and the second main pipe 35B.

[0061] A check valve 47 (hereinafter also referred to as the first check valve 47) allows pressurized oil to flow from the second main pipeline 35B side to the first main pipeline 35A side, and prevents pressurized oil from flowing in the opposite direction. That is, the first check valve 47 enables the flow of working oil from the second main pipeline 35B to the first main pipeline 35A, and cuts off the flow of working oil from the first main pipeline 35A to the second main pipeline 35B. Another check valve 48 (hereinafter also referred to as the second check valve 48) allows pressurized oil to flow from the first main pipeline 35A side to the second main pipeline 35B side, and prevents pressurized oil from flowing in the opposite direction. That is, the second check valve 48 enables the flow of working oil from the first main pipeline 35A to the second main pipeline 35B, and cuts off the flow of working oil from the second main pipeline 35B to the first main pipeline 35A.

[0062] Bypass lines 45 and 46, bypassing each check valve 47 and 48, connect to the connecting line 44. The first bypass line 45 branches off from the connecting line 44 and bypasses the first check valve 47 before connecting to the connecting line 44. The second bypass line 46 branches off from the connecting line 44 and bypasses the second check valve 48 before connecting to the connecting line 44. Variable relief valves 38A and 38B are located midway through the bypass lines 45 and 46.

[0063] Specifically, the first variable relief valve 38A is located midway through the first bypass line 45. When the pressure in the first main line 35A is below a predetermined pressure, the first variable relief valve 38A cuts off the flow of working oil from the first main line 35A to the second main line 35B. When the pressure in the first main line 35A exceeds the predetermined pressure, the first variable relief valve 38A opens the flow of working oil from the first main line 35A to the second main line 35B. On the other hand, the second variable relief valve 38B is located midway through the second bypass line 46. When the pressure in the second main line 35B is below a predetermined pressure, the second variable relief valve 38B cuts off the flow of working oil from the second main line 35B to the first main line 35A. When the pressure in the second main line 35B exceeds the predetermined pressure, the second variable relief valve 38B opens the flow of working oil from the second main line 35B to the first main line 35A. Variable relief valves 38A and 38B are controlled by a command signal (command signal W) from controller 25. A W B This is a electrically operated relief valve (e.g., a solenoid relief valve) that changes the opening pressure (relief pressure). It is based on a command signal (command signal W) from the controller 25. A W B ), change the set pressure (overflow set pressure, i.e., overflow start pressure) of variable relief valves 38A and 38B.

[0064] A first speed detector 49 is installed on the input shaft 22 of the transmission 21. The first speed detector 49 is a rotational sensor that detects the rotational speed and direction of the input shaft 22. The rotational speed of the input shaft 22 corresponds to the rotational speed of the engine 9 (hereinafter referred to as engine rotational speed Vin). The first speed detector 49 outputs a detection signal corresponding to the engine rotational speed Vin to the controller 25. A second speed detector 50 is installed on the output shaft 23 of the transmission 21. The second speed detector 50 is a rotational sensor that detects the rotational speed of the output shaft 23 (hereinafter referred to as output rotational speed Vout) and the direction of rotation. The output rotational speed Vout corresponds to the vehicle speed. The second speed detector 50 outputs a detection signal corresponding to the output rotational speed Vout and the direction of rotation to the controller 25.

[0065] The first pressure detector 51 is installed in the first main pipeline 35A. The first pressure detector 51 is a pressure sensor that detects the hydraulic pressure of the first main pipeline 35A. The first pressure detector 51 outputs the hydraulic pressure P of the first main pipeline 35A to the controller 25. AThe corresponding detection signal. The second pressure detector 52 is located on the second main pipeline 35B. The second pressure detector 52 is a pressure sensor that detects the hydraulic pressure of the second main pipeline 35B. The second pressure detector 52 outputs the hydraulic pressure P of the second main pipeline 35B to the controller 25. B The corresponding detection signal.

[0066] The third pressure detector 53 is installed on the first clutch 27C. The third pressure detector 53 is a pressure sensor that detects the clutch pressure (pressure) of the first clutch 27C. The third pressure detector 53 outputs the clutch pressure P of the first clutch 27C to the controller 25. C The corresponding detection signal. Operation quantity detector 8C (reference) Figure 1 The accelerator pedal 8A is equipped with an operation quantity detector 8C, which is an operation quantity detection sensor that detects the operation quantity θ1 of the accelerator pedal 8A. The operation quantity detector 8C outputs a detection signal corresponding to the operation quantity θ1 of the accelerator pedal 8A to the controller 25. In addition, the output value (capacity θ2) of the capacity sensor (not shown) of the first hydraulic pump motor 33 and the output value (capacity θ3) of the capacity sensor (not shown) of the second hydraulic pump motor 34 are input to the controller 25.

[0067] like Figure 7 As shown, a command (command signal C1) from controller 25 is input to the first clutch 27C. Based on the command (command signal C1) from controller 25, the engagement and disengagement of the first clutch 27C are controlled. A command (command signal C2) from controller 25 is input to the second clutch 36. Based on the command (command signal C2) from controller 25, the engagement and disengagement of the second clutch 36 are controlled. A command (command signal C3) from controller 25 is input to the third clutch 37. Based on the command (command signal C3) from controller 25, the engagement and disengagement of the third clutch 37 are controlled.

[0068] Next, the planetary gear mechanism 29 will be described. Figure 3 as well as Figure 7 In the diagram, the planetary gear mechanism 29 is represented by a box (rectangular frame). The planetary gear mechanism 29 has three rotating components: a first component connected to the engine 9, which serves as a power source; a second component connected to the first transmission component 33; and a third component connected to the idler gear element 28, which forms the output shaft 23 side. In the first embodiment, the planetary gear mechanism 29 is composed of a planet carrier and two sun gears (a first sun gear and a second sun gear). Table 3 below shows the combination of the constituent elements (planet carrier, first sun gear, and second sun gear) of the planetary gear mechanism 29.

[0069] [Table 3]

[0070] like Figure 4 , Figure 5 as well as Figure 8 As shown, in the first embodiment (i.e., No. 1–A in Table 3), the planetary gear mechanism 29 includes a planet carrier 29A corresponding to the first member, a first sun gear 29B corresponding to the second member, a second sun gear 29C corresponding to the third member, planet gears 29D, and a balance gear 29E. Furthermore, the first sun gear 29B, the second sun gear 29C, the planet gears 29D, and the balance gear 29E can transmit power without gear meshing; for example, power can be transmitted through friction of rollers (outer peripheral surfaces).

[0071] Engine 9 is connected to planet carrier 29A via first connecting structural member 30. First sun gear 29B is connected to first transmission component 33 via second connecting structural member 31. Second sun gear 29C is connected to idler gear element 28 (first idler gear 28B) via third connecting structural member 32. First sun gear 29B meshes with planet gear 29D. Second sun gear 29C meshes with balance gear 29E. Balance gear 29E meshes with planet gear 29D.

[0072] The rotation axis S of planetary gear 29D p ( Figure 8 ) and the rotation shaft S of the balance gear 29E b ( Figure 8 The planetary gear 29D and the balance gear 29E are supported on the planetary carrier 29A. Therefore, the planetary gear 29D and the balance gear 29E are positioned around the central axis S of the planetary gear mechanism 29. Figure 8 It revolves around the sun gear 29B while rotating on its own axis. The planetary gear 29D has a gear section 29D1 that meshes with the first sun gear 29B and a gear section 29D2 that meshes with the balance gear 29E.

[0073] Alternatively, in the first embodiment, the balancing gear 29E is disposed between the second sun gear 29C and the planet gear 29D, but it can also be disposed between the first sun gear 29B and the planet gear 29D. Furthermore, the balancing gear 29E can be disposed between both the second sun gear 29C and the planet gear 29D and between the first sun gear 29B and the planet gear 29D, or it can be disposed between neither.

[0074] Figure 8This is a cross-sectional view of the planetary gear mechanism 29 from the power source side. The planet carrier 29A, the first sun gear 29B, and the second sun gear 29C are arranged concentrically. That is, the central axis S (rotation axis) of the planet carrier 29A, the first sun gear 29B, and the second sun gear 29C is aligned. The first sun gear 29B meshes with the gear portion 29D1 of the planet gear 29D. The second sun gear 29C meshes with the balance gear 29E. The balance gear 29E meshes with the gear portion 29D2 of the planet gear 29D. The planet carrier 29A allows the balance gear 29E and the planet gear 29D to rotate freely in their own rotation direction, and constrains them in their revolution direction relative to the central axis S, so that the meshing of the gears of the balance gear 29E and the planet gear 29D is established. Therefore, the planet gear 29D rotates about its central axis S. P It rotates on its own axis and revolves around the central axis S of the planet carrier 29A. Therefore, the central axis of planet gear 29D (rotation axis S) P The trajectory C p It forms a circle centered on the central axis S of the planet carrier 29A. The balancing gear 29E rotates around its central axis, i.e., its rotation axis S. b It rotates on its own axis and revolves around the central axis S of the planet carrier 29A. Therefore, the central axis of the balance gear 29E (rotation axis S) b The trajectory C b It becomes a circle centered on the central axis S of planetary carrier 29A.

[0075] The meshing radius r of the first sun gear 29B s1 This is the meshing radius on the side of the first sun gear 29B when the first sun gear 29B meshes with the planet gear 29D. The meshing radius r of the gear portion 29D1 of the planet gear 29D is... p1 This is the meshing radius on the gear section 29D1 side when the first sun gear 29B meshes with the planet gear 29D. The meshing radius r of the second sun gear 29C... s2 This is the meshing radius on the side of the second sun gear 29C when the second sun gear 29C meshes with the balance gear 29E. The meshing radius r of the gear portion 29D2 of the planet gear 29D is... p2 It is the meshing radius on the planetary gear 29D side when the balance gear 29E meshes with the planetary gear 29D.

[0076] In the first embodiment (No. 1–A of Table 3), the planetary carrier 29A is connected to the first connecting structural member 30, which is connected to the engine 9. Therefore, the torque T of the planetary carrier 29A is... c This refers to the torque that engine 9 can produce. The first sun gear 29B is connected to the component (terminal) connected to the first transmission component 33, namely the second connecting structural member 31. Therefore, the torque T of the first sun gear 29B... s1This refers to the torque generated by the first transmission component 33. The second sun gear 29C is connected to the component (terminal) connected to the idler gear element 28, namely the third connecting component 32. Therefore, the torque T of the second sun gear 29C is... s2 It is the torque reaction force received by the idler gear 28B.

[0077] During the power transmission period of the planetary continuously variable transmission 24, the torque T of the first sun gear 29B is... s1 The torque T of the second sun gear 29C s2 And the torque T of planetary carrier 29A c The ratio remains constant. Based on this rule, controller 25 outputs a signal to control the first transmission component 33, controlling the torque of the second connecting member 31 (e.g., the first sun gear 29B) connected to the first transmission component 33. That is, controller 25 controls the torque of the second connecting member 31 (e.g., the first sun gear 29B) by controlling the first transmission component 33. Thus, controller 25 indirectly controls the torque of the first connecting member 30 (e.g., the planetary carrier 29A) connected to the engine 9 and the torque of the third connecting member 32 (e.g., the second sun gear 29C) connected to the idler gear element 28. As a result, torque transmission can be controlled between the first connecting member 30 (e.g., the planetary carrier 29A) connected to the engine 9 and the third connecting member 32 (e.g., the second sun gear 29C) connected to the idler gear element 28.

[0078] Figure 9 This describes the relationship between the rotational speeds of the planetary gear mechanism 29. Assume the rotational speed of the planet carrier 29A is constant. In this case, when the rotational speed of the second sun gear 29C is increased, the rotational speed of the first sun gear 29B decreases. Conversely, when the rotational speed of the second sun gear 29C is decreased, the rotational speed of the first sun gear 29B increases. Based on this rule, the controller 25 outputs a signal to control the first transmission component 33, controlling the rotational speed of the second connecting component 31 (e.g., the first sun gear 29B) connected to the first transmission component 33. That is, the controller 25 controls the rotational speed of the second connecting component 31 (e.g., the first sun gear 29B) by controlling the first transmission component 33. Thus, the controller 25 indirectly controls the rotational speed of the first connecting component 30 (e.g., the planet carrier 29A) connected to the engine 9 and the rotational speed of the third connecting component 32 (e.g., the second sun gear 29C) connected to the idler gear element 28. As a result, the gear ratio can be controlled between the first structural member 30 (e.g., planetary carrier 29A) connected to the engine 9 and the third structural member 32 (e.g., second sun gear 29C) connected to the idler gear element 28.

[0079] When the ratio of the rotational speed of the second sun gear to the rotational speed of the planet carrier is 0, the second sun gear 29C rotates at zero. Since the second sun gear 29C is connected to the output shaft 23 via the third connecting component 32, the idler gear element 28, and the multi-stage transmission mechanism 26, the second sun gear 29C rotates at 0 min. –1 In this case, the vehicle speed is 0 km / h. This means that the gear ratio of the planetary continuously variable transmission (CVT) 24 is infinitely large. Alternatively, it can be like... Figure 14 As shown in the second variation (i.e., No. 1–B in Table 3), the planetary gear mechanism 29 connects the first sun gear 29B to the component connected to the engine 9, i.e., the first connecting member 30; connects the planet carrier 29A to the component connected to the first transmission component 33, i.e., the second connecting member 31; and connects the second sun gear 29C to the component connected to the idler gear element 28, i.e., the third connecting member 32. Alternatively, it can be as follows... Figure 15 As shown in the third variation (i.e., No. 1–C in Table 3), the planetary gear mechanism 29 connects the first sun gear 29B to the first connecting member 30, the second sun gear 29C to the second connecting member 31, and the planet carrier 29A to the third connecting member 32.

[0080] Next, the internal locking action of the planetary continuously variable transmission (CVT) 24 will be explained. The power transmission efficiency between the planetary gear mechanism 29 and the idler gear element 28 is higher via the transmission path through the third connecting member 32 than via the transmission path through the second connecting member 31, the first transmission component 33, the transmission element 35, the second transmission component 34, the third clutch 37, and the transmission 39. Therefore, to improve transmission efficiency, the rotation of the second connecting member 31 connected to the first transmission component 33 is stopped, and no power transmission occurs between the first transmission component 33 and the second transmission component 34. In this case, the power supplied from the engine 9 to the planetary gear mechanism 29 via the first connecting member 30 is not distributed to the second connecting member 31 connected to the first transmission component 33, but is entirely transmitted to the third connecting member 32 connected to the idler gear element 28.

[0081] To set the planetary continuously variable transmission 24 to an internally locked state, the rotation of the second connecting member 31, which is connected to the first transmission component 33, among the three connecting members 30, 31, and 32 connected to the planetary gear mechanism 29, must be stopped. When both the first transmission component 33 and the second transmission component 34 are hydraulic pump motors, the controller 25 maintains the volume of the hydraulic pump motor of the first transmission component 33 at a specified level or higher (preferably at least 10% of the maximum volume) and controls the volume of the hydraulic pump motor of the second transmission component 34 to zero.

[0082] Alternatively, an internal locking state can be achieved by fixing the rotating shaft of the first transmission component 33 to the non-rotating part and stopping the rotation of the first transmission component 33. For example, it can also be done as follows: Figure 13 As shown in the first variation, the second connecting member 31 is fixed to a non-rotating part (e.g., the housing of the transmission 21) by means of a braking mechanism 55, thereby achieving an internal locking state. The braking mechanism 55 can be structured such that the second connecting member 31, connected to the first transmission component 33, is fixed to the non-rotating part by friction or mechanical engagement. In particular, when the first transmission component 33 is a generator, from the viewpoint of power loss, it is preferable to use the braking mechanism 55 to fix the second connecting member 31 to the non-rotating part.

[0083] In the case of a transmission device 21 capable of both internal and external locking of the planetary continuously variable transmission (CVT) mechanism 24, power transmission is achieved by continuously shifting the planetary CVT mechanism 24 during start-up and excavation. During transport and return, power transmission is achieved by internal locking of the planetary CVT mechanism 24 or through an external locking mechanism (direct connection mechanism 27). Therefore, during start-up and excavation (e.g., 0 km / h to 7 km / h) when continuously shifting is required, transmission efficiency can be improved by continuously shifting the planetary CVT mechanism 24. On the other hand, during transport and return (e.g., 7 km / h and above) when continuously shifting is not required, transmission efficiency can be further improved than continuously variable transmission by internally locking the planetary CVT mechanism 24 or by using an external locking mechanism (direct connection mechanism 27) for power transmission.

[0084] Next, refer to Figure 3 as well as Figure 4 The direct connection mechanism 27, which serves as an external locking mechanism, is described below. Instead of via the planetary continuously variable transmission 24, the direct connection mechanism 27 transmits power supplied from the engine 9 to the idler gear element 28 through the meshing of gears. The direct connection mechanism 27 includes an input gear 27A mounted on the input shaft 22, a locking gear 27B meshing with the input gear 27A, and a first clutch 27C. The rotating shaft 27B1, on which the locking gear 27B is mounted, is connected to the idler shaft 28A of the idler gear element 28 via the first clutch 27C.

[0085] The first clutch 27C is disposed between the input shaft 22 (more specifically, the rotating shaft 27B1) and the idler shaft 28A. The first clutch 27C is, for example, a clutch (friction plate) formed by frictional engagement, a claw clutch, or a claw clutch with a synchronizing engagement. The first clutch 27C performs the mechanical engagement and disengagement between the locking gear 27B (rotating shaft 27B1) and the idler element 28 (idler shaft 28A). By disengaging the second clutch 36 and engaging the first clutch 27C, the power input from the input shaft 22 is transmitted to the idler element 28 (first idler gear 28B and second idler gear 28C) via the input gear 27A, the locking gear 27B, and the first clutch 27C. Thus, the power supplied from the engine 9 can be transmitted to the first idler gear 28B and the second idler gear 28C via the direct connection mechanism 27, which serves as an external locking mechanism, instead of via the planetary continuously variable transmission 24.

[0086] Here, the external locking rotation speed ratio Ir is defined as in Equation 1 below. In this case, the number of teeth of the input gear 27A is set to "N27A", and the number of teeth of the locking gear 27B is set to "N27B".

[0087] (Equation 1) Ir=N27A / N27B

[0088] In the case of a transmission device 21 that has an external locking mechanism (direct connection mechanism 27) and performs an internal locking operation, the external locking rotational speed ratio Ir is preferably set to be greater than or equal to the internal locking output gear ratio Ip. Preferably, in order to utilize the gear ratios of the planetary continuously variable transmission 24 more broadly and effectively, the external locking rotational speed ratio Ir is made greater than the internal locking output gear ratio Ip. This allows for a more broad and effective use of the speed increase range of the planetary continuously variable transmission 24. The internal locking output gear ratio Ip is defined by the following formula 2. In this case, the number of teeth of the third connecting member 32 connected to the first idler gear 28B is set to "N32", the number of teeth of the first idler gear 28B is set to "N28B", and the internal locking gear ratio is set to "In".

[0089] (Equation 2) Ip = In × (N32 / N28B)

[0090] The transmission device 21, equipped with an external locking mechanism (direct connection mechanism 27) and an internal locking action, can transmit power as follows: During continuously variable transmission (CVT) starting and digging (vehicle speed 0 km / h to 7 km / h), power is transmitted while CVT is performed via planetary CVT mechanism 24. During transport and return (vehicle speed 7 km / h and above), power is transmitted while the internal locking mechanism 24 is activated. During transport and return (vehicle speed 10 km / h and above), power is transmitted via the external locking mechanism (direct connection mechanism 27). Thus, the transmission device 21 can select the transmission path with the highest transmission efficiency during all operations, including digging, starting, transporting, and returning.

[0091] Next, the multi-stage transmission mechanism 26 will be described. The multi-stage transmission mechanism 26 is a transmission mechanism that changes speed through gear engagement, clutch switching, and brake switching. The multi-stage transmission mechanism 26 is, for example, equivalent to a planetary transmission, a countershaft type transmission, a manual transmission, a semi-automatic transmission, or a dual-clutch transmission. In the first embodiment, the multi-stage transmission mechanism 26 is composed of a countershaft type transmission with three forward gears and one backward gear.

[0092] Reference Figure 6 This describes a multi-stage transmission mechanism 26, which is a counterspindle type transmission. The multi-stage transmission mechanism 26 includes a low-gear shaft unit 61, a high-gear shaft unit 62, an output shaft unit 63, and a counterspindle gear 64. The low-gear shaft unit 61 is configured to include a low-gear shaft 65, a forward 1st gear gear 66, a backward 1st gear gear 67, a low-gear gear 68, a forward 1st gear clutch 69, and a backward 1st gear clutch 70. The high-gear shaft unit 62 is configured to include a high-gear shaft 71, a forward 2nd gear gear 72, a forward 3rd gear gear 73, a high-gear gear 74, a forward 2nd gear clutch 75, and a forward 3rd gear clutch 76. The counterspindle gear 64 is a gear used to reverse the rotation direction of the output shaft 77 of the output shaft unit 63. The output shaft unit 63 is configured to include an output shaft 77, a low-gear output gear 78, and a high-gear output gear 79. The output shaft 77 of the output shaft unit 63 (i.e., the output shaft 77 of the multi-stage speed change mechanism 26) corresponds to the output shaft 23 of the speed change device 21.

[0093] The first forward gear 67 is always meshed with the first idler gear 28B via the countershaft gear 64 and rotates together with the first idler gear 28B. The third forward gear 73 is always meshed with the first idler gear 28B and rotates together with the first idler gear 28B. The first forward gear 66 is always meshed with the second idler gear 28C and rotates together with the second idler gear 28C. The second forward gear 72 is always meshed with the second idler gear 28C and rotates together with the second idler gear 28C.

[0094] The first-gear clutch 70 engages and disengages the first-gear gear 67 from the low-gear shaft 65. By engaging the first-gear gear 67 with the low-gear shaft 65 using the first-gear clutch 70, power transmission is possible between the first idler gear 28B and the low-gear shaft 65. The first-gear clutch 69 engages and disengages the first-gear gear 66 from the low-gear shaft 65 using the first-gear clutch 69. By engaging the first-gear gear 66 with the low-gear shaft 65 using the first-gear clutch 69, power transmission is possible between the second idler gear 28C and the low-gear shaft 65.

[0095] The forward 2nd gear clutch 75 engages and disengages the forward 2nd gear 72 from the high gear shaft 71. By engaging the forward 2nd gear 72 with the high gear shaft 71 using the forward 2nd gear clutch 75, power transmission is possible between the second idler gear 28C and the high gear shaft 71. The forward 3rd gear clutch 76 engages and disengages the forward 3rd gear 73 from the high gear shaft 71 using the forward 3rd gear clutch 76. By engaging the forward 3rd gear 73 with the high gear shaft 71 using the forward 3rd gear clutch 76, power transmission is possible between the first idler gear 28B and the high gear shaft 71.

[0096] The low-gear gear 68 of the low-gear shaft unit 61 is always meshed with the low-gear output gear 78 of the output shaft unit 63, and the low-gear shaft 65 and the output shaft 77 rotate as a unit. In addition, the high-gear gear 74 of the high-gear shaft unit 62 is always meshed with the high-gear output gear 79 of the output shaft unit 63, and the high-gear shaft 71 and the output shaft 77 rotate as a unit.

[0097] That is, when the first gear 67 is engaged with the low gear shaft 65 using the first gear clutch 70, the first idler gear 28B, the countershaft gear 64, the first gear 67, the first gear clutch 70, the low gear shaft 65, the low gear 68, the low gear output gear 78, and the output shaft 77 rotate as a whole. Thus, the power transmitted to the idler element 28 (idler shaft 28A and first idler gear 28B) via the planetary continuously variable transmission mechanism 24 or the direct connection mechanism 27 can be transmitted to the output shaft 77.

[0098] When the first gear gear 66 is engaged with the low gear shaft 65 using the first gear clutch 69, the second idler gear 28C, the first gear gear 66, the first gear clutch 69, the low gear shaft 65, the low gear gear 68, the low gear output gear 78, and the output shaft 77 rotate as a whole. This allows the power transmitted via the planetary continuously variable transmission mechanism 24 or the direct connection mechanism 27 to the idler element 28 (idler shaft 28A and the second idler gear 28C) and then to the output shaft 77.

[0099] When the forward second gear 72 is engaged with the high gear shaft 71 using the forward second gear clutch 75, the second idler gear 28C, the forward second gear 72, the forward second gear clutch 75, the high gear shaft 71, the high gear 74, the high gear output gear 79, and the output shaft 77 rotate as a whole. This allows the power transmitted via the planetary continuously variable transmission mechanism 24 or the direct connection mechanism 27 to the idler element 28 (idler shaft 28A and the second idler gear 28C) and then to the output shaft 77.

[0100] When the forward 3rd gear 73 is engaged with the high gear shaft 71 using the forward 3rd gear clutch 76, the first idler gear 28B, the forward 3rd gear 73, the forward 3rd gear clutch 76, the high gear shaft 71, the high gear 74, the high gear output gear 79, and the output shaft 77 rotate as a whole. This allows the power transmitted via the planetary continuously variable transmission mechanism 24 or the direct connection mechanism 27 to the idler element 28 (idler shaft 28A and the first idler gear 28B) and then to the output shaft 77. Table 4 below shows the operation (engagement and disengagement) of the various clutches 69, 70, 75, and 76 of the multi-stage transmission mechanism 26.

[0101] [Table 4]

[0102] In 1st gear, the 1st gear clutch 70 engages, and the forward 1st gear clutch 69, forward 2nd gear clutch 75, and forward 3rd gear clutch 76 disengage. In 1st gear, the forward 1st gear clutch 69 engages, and the 1st gear rear clutch 70, forward 2nd gear clutch 75, and forward 3rd gear clutch 76 disengage. In 2nd gear, the forward 2nd gear clutch 75 engages, and the forward 1st gear clutch 69, the 1st gear rear clutch 70, and forward 3rd gear clutch 76 disengage. In 3rd gear, the forward 3rd gear clutch 76 engages, and the forward 1st gear clutch 69, the 1st gear rear clutch 70, and forward 2nd gear clutch 75 disengage.

[0103] Additionally, in one embodiment, the second transmission component 34 is connected to the idler gear element 28 (idler shaft 28A) via the third clutch 37 and the transmission 39. Alternatively, it can be as follows... Figure 16 As shown in the fourth variation, the second transmission component 34 is connected to the output shaft 77 of the multi-stage transmission mechanism 26 (output shaft 23 of the transmission device 21) via the third clutch 37 and the transmission 39.

[0104] Furthermore, consider the case of a transmission device capable of 6 speed changes. In this case, if the structure does not switch between internal and external locking, a 6-speed auxiliary transmission mechanism (multi-stage transmission mechanism) is required. In contrast, if the structure switches between internal and external locking, a 3-speed auxiliary transmission mechanism (multi-stage transmission mechanism) can be used to achieve 6 speed changes (2×3=6). Therefore, by setting the structure to switch between internal and external locking, the number of speed stages in the auxiliary transmission mechanism (multi-stage transmission mechanism) can be reduced, making the auxiliary transmission mechanism (multi-stage transmission mechanism) smaller and lower in cost. However, in this case, as shown in Tables 1 and 2 above, the speed change (switching) of the auxiliary transmission mechanism (multi-stage transmission mechanism) needs to be performed simultaneously with switching between internal and external locking, making the switching of the transmission path very difficult.

[0105] That is, consider the state where power transmission occurs simultaneously via internal locking and external locking when switching between internal and external locking. In this case, the power generated by the engine 9, which is the power source, is to be transmitted to the idler gear element 28 via the external locking mechanism, i.e., the direct connection mechanism 27, and then returned from the idler gear element 28 to the engine 9 via the planetary continuously variable transmission mechanism 24. However, the reduction ratio from the engine 9 to the idler gear element 28 in the internal locking state is different from that in the external locking state, so a high load is directly applied to the engine 9. As a result, the engine 9 stops, and the rotation of the idler gear element 28 stops abruptly, which may cause the vehicle speed to drop rapidly.

[0106] Therefore, switching between internal and external locking, and simultaneously changing the gears of the secondary transmission mechanism (multi-stage transmission mechanism), can easily lead to vehicle stalling and sudden stops, posing significant problems. In this implementation, the switching between internal and external locking can be performed smoothly, and the gear changes of the secondary transmission mechanism (multi-stage transmission mechanism) can be performed smoothly simultaneously. Furthermore, this allows for a compact and low-cost construction of the multi-stage transmission mechanism. These points will be explained in detail below.

[0107] like Figure 7 As shown, the planetary continuously variable transmission (CVT) 24 includes a planetary gear mechanism 29 and a hydrostatic CVT 41. A pair of main pipelines 35A and 35B of the hydrostatic CVT 41 are connected by a connecting pipeline 44. A first variable relief valve 38A, a second variable relief valve 38B, a first check valve 47, and a second check valve 48 are provided on the connecting pipeline 44. Based on a command signal (command signal W) from the controller 25... A W BThe variable relief valves 38A and 38B control the set pressure (relief set pressure, i.e., relief start pressure) of the variable relief valves 38A and 38B. The variable relief valves 38A and 38B correspond to the connecting valves that can switch the pair of main lines 35A and 35B between the connected state and the disconnected state.

[0108] The controller 25 can set the variable relief valves 38A and 38B to a cut-off state by increasing their set pressure, that is, to a cut-off state that disconnects the pair of main pipelines 35A and 35B. The controller 25 can also set the variable relief valves 38A and 38B to a connected state by decreasing their set pressure, that is, to a connected state that connects the pair of main pipelines 35A and 35B.

[0109] The overflow pressure of the variable relief valves 38A and 38B is typically set to a specified value on the high-pressure side (e.g., 35MPa to 50MPa). That is, when power is transmitted via the planetary continuously variable transmission mechanism 24, the controller 25 sets the overflow pressure of the variable relief valves 38A and 38B to a specified value on the high-pressure side (e.g., 35MPa to 50MPa). At this time, the working fluid from the first hydraulic pump motor 33 to the second hydraulic pump motor 34 via the first main pipe 35A, the working fluid from the first hydraulic pump motor 33 to the second hydraulic pump motor 34 via the second main pipe 35B, the working fluid from the second hydraulic pump motor 34 to the first hydraulic pump motor 33 via the first main pipe 35A, and the working fluid from the second hydraulic pump motor 34 to the first hydraulic pump motor 33 via the second main pipe 35B can be transported without bypassing the connection pipe 44. Thus, power can be transmitted between the first hydraulic pump motor 33 and the second hydraulic pump motor 34.

[0110] Furthermore, for example, when the pressure of the first main pipeline 35A becomes high pressure (e.g., 40 MPa or higher) and exceeds the overflow pressure of the first variable relief valve 38A (the specified value on the high-pressure side), the working fluid of the first main pipeline 35A flows to the second main pipeline 35B through the connecting pipeline 44, the first variable relief valve 38A, and the second check valve 48. When the pressure of the second main pipeline 35B becomes high pressure (e.g., 40 MPa or higher) and exceeds the overflow pressure of the second variable relief valve 38B (the specified value on the high-pressure side), the working fluid of the second main pipeline 35B flows to the first main pipeline 35A through the connecting pipeline 44, the second variable relief valve 38B, and the first check valve 47. Thus, it is possible to suppress the situation where the working fluid pressure becomes excessively high, causing damage to the first hydraulic pump motor 33 and the second hydraulic pump motor 34.

[0111] On the other hand, the controller 25 can cut off the power transmission from the hydraulic pressure within the hydrostatic continuously variable transmission 41 by setting the variable relief valves 38A and 38B to the connected state (i.e., connecting the pair of main lines 35A and 35B). For example, by reducing the relief pressure of the first variable relief valve 38A, the controller 25 can allow the working fluid of the first main line 35A to flow to the second main line 35B through the connecting line 44, the first bypass line 45, the first variable relief valve 38A, the connecting line 44, and the second check valve 48. As a result, the working fluid delivered from the first hydraulic pump motor 33 to the first main line 35A bypasses the second hydraulic pump motor 34 and returns to the first hydraulic pump motor 33. Consequently, the first hydraulic pump motor 33 can no longer transmit power to the second hydraulic pump motor 34 via the first main line 35A. Similarly, the working fluid sent from the second hydraulic pump motor 34 to the first main pipeline 35A bypasses the first hydraulic pump motor 33 and returns to the second hydraulic pump motor 34. As a result, the second hydraulic pump motor 34 can no longer transmit power to the first hydraulic pump motor 33 via the first main pipeline 35A.

[0112] Additionally, for example, by reducing the overflow pressure of the second variable relief valve 38B, the controller 25 can allow the working fluid of the second main pipeline 35B to flow to the first main pipeline 35A via the connecting line 44, the second bypass line 46, the second variable relief valve 38B, the connecting line 44, and the first check valve 47. As a result, the working fluid from the first hydraulic pump motor 33 to the second main pipeline 35B bypasses the second hydraulic pump motor 34 and returns to the first hydraulic pump motor 33. Consequently, the first hydraulic pump motor 33 can no longer transmit power to the second hydraulic pump motor 34 via the second main pipeline 35B. Similarly, the working fluid from the second hydraulic pump motor 34 to the second main pipeline 35B bypasses the first hydraulic pump motor 33 and returns to the second hydraulic pump motor 34. Consequently, the second hydraulic pump motor 34 can no longer transmit power to the first hydraulic pump motor 33 via the second main pipeline 35B.

[0113] Furthermore, for example, by reducing the overflow pressure of both the first variable relief valve 38A and the second variable relief valve 38B, the controller 25 can allow the working fluid to bypass the first main pipeline 35A and the second main pipeline 35B in both directions. In this case, power can no longer be transmitted in both directions between the first hydraulic pump motor 33 and the second hydraulic pump motor 34. Additionally, it is not necessary to have both the first variable relief valve 38A and the second variable relief valve 38B; only one may be installed, omitting the other. Furthermore, it is not necessary to have both the first variable relief valve 38A and the second variable relief valve 38B as electromagnetic relief valves; one may be an electromagnetic relief valve, and the other a relief valve with a fixed overflow pressure (fixed relief valve).

[0114] Figure 7The hydrostatic continuously variable transmission (CVT) 41 shown uses variable relief valves 38A and 38B as components to cut off the power transmission from the oil pressure within the CVT 41. Alternatively, it can be as follows... Figure 17 As shown in the fifth variation, a first on / off valve 81A is provided in parallel with the first variable relief valve 38A, and a second on / off valve 81B is provided in parallel with the second variable relief valve 38B. The first on / off valve 81A and the second on / off valve 81B switch the pair of main pipelines 35A and 35B between a connected state and a disconnected state. That is, in Figure 17 In the fifth variation, a first on-off valve 81A and a second on-off valve 81B are provided between a pair of main pipelines 35A and 35B to switch the pair of main pipelines 35A and 35B between a connected state and a disconnected state. The on-off valves 81A and 81B correspond to connecting valves that can switch the pair of main pipelines 35A and 35B between a connected state and a disconnected state.

[0115] That is, the first on / off valve 81A and the second on / off valve 81B can be switched to an open position corresponding to the connected state and a closed position corresponding to the disconnected state. The switching of the first on / off valve 81A and the second on / off valve 81B is controlled based on commands (command signal Wc, command signal Wd) from the controller 25. Specifically, the on / off valves 81A and 81B are electrically operated on / off valves (e.g., solenoid valves) that open and close based on command signals (command signals Wc, Wd) from the controller 25. In this configuration, by opening the first on / off valve 81A, the overflow setting pressure of the first variable relief valve 38A can be set to a low pressure, thus connecting the pair of main pipelines 35A and 35B. Similarly, by opening the second on / off valve 81B, the overflow setting pressure of the second variable relief valve 38B can be set to a low pressure, thus connecting the pair of main pipelines 35A and 35B.

[0116] That is, in Figure 17 In the fifth variation shown, by opening the first on / off valve 81A and the second on / off valve 81B, the pair of main pipelines 35A and 35B are connected, thereby cutting off the power transmission from the oil pressure within the hydrostatic continuously variable transmission mechanism 41. Alternatively, when both the first on / off valve 81A and the second on / off valve 81B are provided, the first variable relief valve 38A and the second variable relief valve 38B can be changed to relief valves with fixed relief pressure (fixed relief valves). Furthermore, it is not necessary to provide both the first on / off valve 81A and the second on / off valve 81B; only one may be provided.

[0117] Here, in the internally locked state, power is transmitted from the engine 9 to the output shaft 23 via the planetary continuously variable transmission 24 and the multi-stage transmission 26. For the transmission of power from the engine 9 to the planetary gear mechanism 29 via the first connecting member 30 to the third connecting member 32, the second connecting member 31 generates torque to maintain the rotation of the planetary gear mechanism 29 in one degree of freedom. To stop the rotation of the second connecting member 31, the torque of the first hydraulic pump motor 33 needs to be generated during internal locking, or the braking mechanism 55 (which acts as the locking mechanism) needs to be activated. Figure 13 (to perform the action.)

[0118] exist Figure 9 In this case, one degree of freedom is determined by the gear ratio at the intersection of the Y1 line and the horizontal axis (rotational speed of the first sun gear / rotational speed of the planet carrier) or the gear ratio at the intersection of the Y1 line and the vertical axis (rotational speed of the second sun gear / rotational speed of the planet carrier). Similarly, in the following description... Figure 39 In this case, one degree of freedom is the gear ratio of the planetary gear mechanism 29 fixed by the gear ratio at the intersection of the Y2 line and the horizontal axis (rotation speed of the sun gear / rotation speed of the planet carrier) or the gear ratio at the intersection of the Y2 line and the vertical axis (rotation speed of the gear ring / rotation speed of the planet carrier).

[0119] When internal locking is achieved using the torque of the first hydraulic pump motor 33, the controller 25 outputs a command signal W. P So that the volume of the first hydraulic pump motor 33 is 10–100%, and the output command signal W is made. M This is to reduce the volume of the second hydraulic pump motor 34 to zero. The working fluid generated by the rotation of the first hydraulic pump motor 33 ceases to flow in the first main pipeline 35A and the second main pipeline 35B because the second hydraulic pump motor 34 is not rotating. On the other hand, as... Figure 13 As shown in the first variant, when internal locking is performed using the braking mechanism 55, which serves as a locking mechanism, the controller 25 engages the braking mechanism 55 and stops the rotation of the second connecting member 31.

[0120] Next, it will be explained that when the set pressure of the variable relief valves 38A and 38B is high, that is, when the variable relief valves 38A and 38B are in the off state.

[0121] First, let's explain the case where the engine 9 (power source) rotates clockwise towards the output shaft 23 (axle), applying a clockwise torque to the first connecting member 30. In this case, the clockwise torque acts on the second connecting member 31, causing the first hydraulic pump motor 33 to rotate clockwise. Let's call this "one direction". At this time, the working fluid flows from the first hydraulic pump motor 33 sequentially through the first main pipe 35A, the second hydraulic pump motor 34, and the second main pipe 35B, intending to return to the first hydraulic pump motor 33. However, since the volume of the second hydraulic pump motor 34 is zero, the flow rate through the second hydraulic pump motor 34 is very small. Therefore, in fact, the flow rate of the working fluid through the first main pipe 35A and the second main pipe 35B is zero. Thus, even if the first hydraulic pump motor 33 does not rotate, a counterclockwise torque can be applied to the second connecting member 31.

[0122] On the other hand, let's explain the case where the engine 9 (power source) rotates clockwise towards the output shaft 23 (axle), applying a counter-clockwise torque to the first connecting member 30. In this case, the counter-clockwise torque acts on the second connecting member 31, causing the first hydraulic pump motor 33 to rotate counter-clockwise. Let's call this the "opposite direction". At this time, the working fluid flows from the first hydraulic pump motor 33 sequentially through the second main line 35B, the second hydraulic pump motor 34, and the first main line 35A, intending to return to the first hydraulic pump motor 33. However, since the volume of the second hydraulic pump motor 34 is zero, the flow rate through the second hydraulic pump motor 34 is very small. Therefore, in fact, the flow rate of the working fluid through the second main line 35B and the first main line 35A is zero. Thus, even if the first hydraulic pump motor 33 does not rotate, a clockwise torque can be applied to the second connecting member 31.

[0123] In this way, by setting both the first variable relief valve 38A and the second variable relief valve 38B to the off state, the controller 25 can set the operating state of the first hydraulic pump motor 33 to a state where torque (load) acts in both directions. In this case, internally locked power transmission can be achieved in both the "one direction" and the "opposite direction".

[0124] Next, the case where the set pressure of the first variable relief valve 38A is high and the set pressure of the second variable relief valve 38B is low, that is, the first variable relief valve 38A is in the off state and the second variable relief valve 38B is in the connected state, will be explained.

[0125] First, let's explain the case where the engine 9 (power source) rotates clockwise towards the output shaft 23 (axle), applying a clockwise torque to the first connecting member 30. In this case, the clockwise torque acts on the second connecting member 31, causing the first hydraulic pump motor 33 to rotate clockwise (in one direction). At this time, the working fluid flows from the first hydraulic pump motor 33 sequentially through the first main pipe 35A, the second hydraulic pump motor 34, and the second main pipe 35B, intending to return to the first hydraulic pump motor 33. However, since the volume of the second hydraulic pump motor 34 is zero, the flow rate through the second hydraulic pump motor 34 is very small. Therefore, in fact, the flow rate of the working fluid through the first main pipe 35A and the second main pipe 35B is zero. Thus, even if the first hydraulic pump motor 33 does not rotate, a counterclockwise torque can be applied to the second connecting member 31. That is, internally locked power transmission is possible.

[0126] On the other hand, let's explain the case where the engine 9 (power source) rotates clockwise towards the output shaft 23 (axle), applying a counterclockwise torque to the first connecting member 30. In this case, the counterclockwise torque acts on the second connecting member 31, causing the first hydraulic pump motor 33 to rotate counterclockwise (in the opposite direction). At this time, the working fluid flows from the first hydraulic pump motor 33 through the second main line 35B, connecting line 44, second variable overflow valve 38B, and first check valve 47 to the first main line 35A, and returns to the first hydraulic pump motor 33. As a result, no clockwise torque is generated in the second connecting member 31. That is, the internally locked power transmission is cut off.

[0127] In this way, by setting the first variable relief valve 38A to the off state and the second variable relief valve 38B to the on state, the controller 25 can set the operating state of the first hydraulic pump motor 33 to a state where torque (load) is applied in one direction and no torque (load) is applied in the opposite direction. In this case, the internal locking power transmission in the "opposite direction" is cut off, and the internal locking power transmission in the "one direction" can be performed.

[0128] Here, in the internally locked state, power is transmitted from engine 9 to output shaft 23 via planetary continuously variable transmission 24, idler gear element 28, and multi-stage transmission mechanism 26. In the externally locked state, power is transmitted from engine 9 to output shaft 23 via external locking mechanism (direct connection mechanism 27), idler gear element 28, and multi-stage transmission mechanism 26. Comparing the reduction ratio from engine 9 to idler gear element 28 in the internally locked state with the reduction ratio from engine 9 to idler gear element 28 in the externally locked state, the reduction ratio in the internally locked state is set to be larger. For example, in… Figure 11 In the case of the structure shown (the structure in Table 1 above), if we compare the internal locking L of forward 1st gear...f2 and forward 1st gear external lock L f3 Then, move forward in 1st gear and lock the external L. f3 That would increase the rotational speed of the output shaft 23 relative to the rotational speed of the engine 9.

[0129] That is, when the internal and external locking mechanisms are activated simultaneously, the power generated by engine 9 is intended to be transmitted to idler wheel element 28 via the external locking mechanism (direct connection mechanism 27), and then returned from idler wheel element 28 to engine 9 via planetary continuously variable transmission mechanism 24. However, since the reduction ratio from engine 9 to idler wheel element 28 in the internal locking state is different from that in the external locking state, a high load is directly applied to engine 9. As a result, engine 9 stops, and the idler wheel element 28 stops rotating abruptly, causing the speed of wheel loader 1 (vehicle) to drop rapidly. Therefore, the switching between internal and external locking presents a significant problem.

[0130] To solve this problem, it is necessary to cut off the internally locked transmission state in the "opposite direction" and enable the internally locked transmission state in the "one direction". Figure 18 This is a characteristic graph (time graph) showing the time changes in the rotational speed of engine 9 (power source), the rotational speed of the second connecting component 31, the pressure of the first clutch 27C, and the pressure of the second clutch 36 when switching from "internal lock-up" to "external lock-up". The first clutch 27C is the clutch of the external lock-up mechanism (direct connection mechanism 27) (direct connection clutch, external lock-up clutch). The second clutch 36 is the clutch connecting the planetary gear mechanism 29 and the first hydraulic pump motor 33.

[0131] from Figure 18 From time B to time E, controller 25 controls variable relief valves 38A and 38B to set the operating state of the first hydraulic pump motor 33 so that rotation in one direction stops and rotation in the opposite direction is freely possible. That is, controller 25 sets the first variable relief valve 38A to the off state and the second variable relief valve 38B to the on state, thereby setting the operating state of the first hydraulic pump motor 33 to a state where torque (load) acts in one direction and no torque (load) acts in the opposite direction. In this state, from... Figure 18 From time C to time E, controller 25 engages (pressurizes) the first clutch 27C. This allows for internal and external locking to prevent interference with power transmission. Figure 18 During the transition from time C to time D, the rotational speed of engine 9 (power source) decreases (an instruction to reduce the rotational speed is input to engine 9).

[0132] On the other hand, in such Figure 13In the case of internal locking using the braking mechanism 55 as shown in the first modified example, such as Figure 19 As shown, from time E to time F, the controller 25 releases (depressurizes) the braking mechanism 55. In this case, from Figure 19 From time D to time I, controller 25 controls variable relief valves 38A and 38B to set the operating state of the first hydraulic pump motor 33 to stop rotating in one direction and freely rotate in the opposite direction. That is, controller 25 sets the first variable relief valve 38A to the off state and the second variable relief valve 38B to the on state, thereby setting the operating state of the first hydraulic pump motor 33 to a state where torque (load) acts in one direction and no torque (load) acts in the opposite direction. In this state, from... Figure 19 From time G to time I, controller 25 engages the first clutch 27C (boosts pressure).

[0133] on the other hand, Figure 20 This is a characteristic graph (time graph) showing the time changes in the rotational speed of engine 9 (power source), the rotational speed of the second connecting component 31, the pressure of the first clutch 27C, and the pressure of the second clutch 36 when switching from "external lock-up" to "internal lock-up". From Figure 20 From time B to time F, controller 25 controls variable relief valves 38A and 38B to set the operating state of the first hydraulic pump motor 33 to stop rotating in one direction and freely rotate in the opposite direction. That is, controller 25 sets the first variable relief valve 38A to the off state and the second variable relief valve 38B to the on state, thereby setting the operating state of the first hydraulic pump motor 33 to a state where torque (load) acts in one direction and no torque (load) acts in the opposite direction. In this state, from... Figure 20 During time D to time F, controller 25 disengages (reduces pressure) the first clutch 27C. This allows for both internal and external locking to prevent interference with power transmission. Figure 20 During the transition from time E to time F, the rotational speed of engine 9 (power source) increases (an instruction to increase the rotational speed is input to engine 9).

[0134] On the other hand, in such Figure 13 In the case of internal locking using the braking mechanism 55 as shown in the first modified example, such as Figure 21As shown, from time B to time F, controller 25 controls variable relief valves 38A and 38B to set the operating state of the first hydraulic pump motor 33 to stop rotating in one direction and freely rotate in the opposite direction. That is, controller 25 sets the first variable relief valve 38A to the off state and the second variable relief valve 38B to the on state, thereby setting the operating state of the first hydraulic pump motor 33 to a state where torque (load) acts in one direction and no torque (load) acts in the opposite direction. In this state, from... Figure 21 During time D to time F, controller 25 disengages the first clutch 27C (depressurizes). Then, from time G to time H, controller 25 engages the braking mechanism 55 (increases pressure), fully transitioning to the internal lock-up state.

[0135] Next, the case where the set pressure of the first variable relief valve 38A is low and the set pressure of the second variable relief valve 38B is high, that is, the first variable relief valve 38A is in the connected state and the second variable relief valve 38B is in the cut-off state, will be explained.

[0136] First, let's explain the case where the engine 9 (power source) rotates clockwise towards the output shaft 23 (axle), applying a clockwise torque to the first connecting member 30. In this case, the clockwise torque acts on the second connecting member 31, causing the first hydraulic pump motor 33 to rotate clockwise (in one direction). At this time, the working fluid flows from the first hydraulic pump motor 33 through the first main pipe 35A, connecting pipe 44, first variable overflow valve 38A, and second check valve 48 to the second main pipe 35B, and returns to the first hydraulic pump motor 33. As a result, no counterclockwise torque is generated in the second connecting member 31, allowing it to rotate freely. That is, the internally locked power transmission is cut off.

[0137] On the other hand, let's explain the case where the engine 9 (power source) rotates clockwise towards the output shaft 23 (axle), applying a counterclockwise torque to the first connecting member 30. In this case, the counterclockwise torque acts on the second connecting member 31, causing the first hydraulic pump motor 33 to rotate counterclockwise (in the opposite direction). At this time, the working fluid flows from the first hydraulic pump motor 33 sequentially through the second main line 35B, the second hydraulic pump motor 34, and the first main line 35A, aiming to return to the first hydraulic pump motor 33. However, since the volume of the second hydraulic pump motor 34 is zero, the flow rate through the second hydraulic pump motor 34 is very small. Therefore, in fact, the flow rate of the working fluid through the first main line 35A and the second main line 35B is zero. Thus, even if the first hydraulic pump motor 33 does not rotate, a counterclockwise torque can be applied to the second connecting member 31. That is, internally locked power transmission is possible. In this way, by setting the first variable relief valve 38A to the connected state and the second variable relief valve 38B to the disconnected state, the controller 25 can set the operating state of the first hydraulic pump motor 33 to a state where torque (load) is applied in the opposite direction and no torque (load) is applied in one direction. In this case, internal locking power transmission in the "opposite direction" can be performed, and internal locking power transmission in the "one direction" is cut off.

[0138] It should be noted that switching between internal and external locking requires cutting off the internal locking operation in the "opposite direction" while maintaining the internal locking operation in one direction. Therefore, switching between internal and external locking requires the overflow pressure of the first variable relief valve 38A to be variable, while the overflow pressure of the second variable relief valve 38B can be fixed.

[0139] Next, it will be explained when the set pressure of both the first variable relief valve 38A and the second variable relief valve 38B is low, that is, when both the first variable relief valve 38A and the second variable relief valve 38B are in a connected state.

[0140] In this situation, it is impossible to generate both clockwise and counterclockwise torque in the second connecting structure 31. That is, by setting both the first variable relief valve 38A and the second variable relief valve 38B to the connected state, the controller 25 can set the operating state of the first hydraulic pump motor 33 to a state where no torque (load) is applied in either direction. In this case, the internal lock-up state is released in both the "one direction" and the "opposite direction".

[0141] Next, refer to Figure 22 This describes the situation where the transmission state of the planetary continuously variable transmission mechanism 24 is switched from "continuously variable transmission" to "internal lock-up".

[0142] In the structure described in Table 1 above, with the speed levels of the multi-speed transmission mechanism 26 being forward 1st gear and backward 1st gear, a switch from continuously variable transmission (CVT) to internal lock-up is envisioned. Furthermore, in the structure described in Table 2 above, with the speed levels of the multi-speed transmission mechanism 26 being forward 1st gear, forward 2nd gear, forward 3rd gear, and backward 1st gear, a switch from CVT to internal lock-up is envisioned. Figure 22 This is a characteristic graph (time graph) showing an example of the time changes in the rotational speed of the engine 9 (power source), the rotational speed of the second connecting component 31, the pressure of the third clutch 37, and the reduction ratio of the planetary continuously variable transmission mechanism 24 when switching from "continuously variable transmission" to "internal lock-up". The third clutch 37 is a clutch located between the second hydraulic pump motor 34 and the idler wheel element 28.

[0143] exist Figure 22 During the continuously variable transmission (CVT) state from time A to time B, controller 25 engages the second clutch 36 and the third clutch 37, and disengages the first clutch 27C. In this state, controller 25 adjusts the rotational speed of the first hydraulic pump motor 33, and adjusts the rotation of the second linkage member 31 to achieve the target reduction ratio. Furthermore, to switch from CVT to internal lock-up, from... Figure 22 From time B to time C, controller 25 reduces the rotational speed of the first hydraulic pump motor 33, stopping its rotation. This, in turn, stops the rotation of the second connecting member 31. Furthermore, in... Figure 22 After time C, the reduction ratio of the planetary continuously variable transmission (CVT) 24 remains fixed, and the transmission gradually locks inward. To reduce power loss, the third clutch 37 disengages after time C. For example, from... Figure 22 From time E to time F, controller 25 disengages the third clutch 37. Figure 22 During the transition from time B to time C, the rotational speed of engine 9 (power source) decreases (an instruction to reduce the rotational speed is input to engine 9).

[0144] On the other hand, refer to Figure 23 , indicating Figure 13 As shown in the first modified example, the transmission state of the planetary continuously variable transmission 24 is switched from "continuously variable transmission" to "internal lock-up" by using the braking mechanism 55 for internal locking.

[0145] exist Figure 23During the continuously variable transmission (CVT) state from time A to time B, controller 25 engages the second clutch 36 and the third clutch 37, disengaging the first clutch 27C and the braking mechanism 55 (pressure reduction). In this state, controller 25 adjusts the rotational speed of the first hydraulic pump motor 33 and adjusts the rotation of the second linkage member 31 to achieve the target reduction ratio. Furthermore, to switch from CVT to internal lock-up, from... Figure 23 From time B to time C, controller 25 reduces the rotational speed of the first hydraulic pump motor 33, stopping its rotation. This, in turn, stops the rotation of the second connecting member 31. Braking mechanism 55... Figure 23 Engagement (boosting) begins after time C, and the system is fully locked internally. For example, from... Figure 23 From time D to time E, controller 25 engages braking mechanism 55 (increases pressure). Figure 23 After time C, the reduction ratio of the planetary continuously variable transmission 24 is fixed, and it switches from continuously variable transmission to internal locking.

[0146] Next, refer to Figure 24 This explains the situation where the transmission state of the planetary continuously variable transmission (CVT) 24 switches from "internal lock-up" to "continuously variable transmission". For example, in the structure described in Table 1 above, with the speed stages of the multi-stage transmission 26 being forward 1st gear and backward 1st gear, the switching from internal lock-up to CVT is envisioned. Furthermore, in the structure described in Table 2 above, with the speed stages of the multi-stage transmission 26 being forward 1st gear, forward 2nd gear, forward 3rd gear, and backward 1st gear, the switching from internal lock-up to CVT is envisioned.

[0147] exist Figure 24 During the internal lock-up state from time A to time D, controller 25 engages the second clutch 36, stopping the rotation of the first hydraulic pump motor 33 and thus stopping the rotation of the second connecting member 31. This disengages the first clutch 27C. In the internal lock-up state, the third clutch 37 can be either disengaged or engaged. With the third clutch 37 disengaged, in order to switch from internal lock-up to continuously variable transmission (CVT), controller 25 engages the third clutch 37... Figure 24 The engagement is completed before time B in the middle. Then, from Figure 24 From time D to time E, controller 25 adjusts the rotational speed of the first hydraulic pump motor 33, and adjusts the rotation of the second connecting component 31 to achieve the target reduction ratio. Thus, in Figure 24 After time D, the reduction ratio of the planetary continuously variable transmission (CVT) 24 can change steplessly, shifting from internal locking to stepless speed change. Figure 24 During the transition from time D to time E, the rotational speed of engine 9 (power source) increases (an instruction to increase the rotational speed is input to engine 9).

[0148] On the other hand, refer to Figure 25 , indicating Figure 13 As shown in the first modified example, the transmission state of the planetary continuously variable transmission 24 is switched from "internal lock" to "continuously variable transmission" by using a structure that uses the braking mechanism 55 for internal locking.

[0149] exist Figure 25 During the internal lock-up state from time A to time D, controller 25 engages the second clutch 36, engages the braking mechanism 55 (increases pressure), stops the rotation of the first hydraulic pump motor 33, and stops the rotation of the second connecting member 31. The first clutch 27C disengages. In the internal lock-up state, the third clutch 37 can be either disengaged or engaged. With the third clutch 37 disengaged, in order to switch from internal lock-up to continuously variable transmission (CVT), controller 25 engages the third clutch 37... Figure 25 Engagement is completed before time B. Controller 25 is in Figure 25 During the period from time B to time C, the braking mechanism 55 is disengaged (pressure reduced). Then, from Figure 25 From time D to time E, controller 25 adjusts the rotational speed of the first hydraulic pump motor 33, and adjusts the rotation of the second connecting component 31 to achieve the target reduction ratio. Thus, in Figure 25 After time D, the reduction ratio of the planetary continuously variable transmission 24 can be changed steplessly, from internal locking to stepless speed change.

[0150] Next, refer to Figure 18 This explains the situation where the transmission state of the planetary continuously variable transmission mechanism 24 is switched from "internal lock-up" to "external lock-up".

[0151] In structures such as those in Tables 1 and 2 above, when the speed levels of the multi-stage transmission mechanism 26 are forward 1st gear, forward 2nd gear, forward 3rd gear, and backward 1st gear, a switching from internal lock-up to external lock-up is envisioned. Figure 18 During the internal lock-up state from time A to time B, controller 25 engages the second clutch 36 and disengages the first clutch 27C. Furthermore, controller 25 sets the control state of the first hydraulic pump motor 33 to either "a state where rotation is stopped in both directions (a state where torque is applied in both directions)" or "a state where rotation is stopped in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)". For example, controller 25 sets the first variable relief valve 38A to the off state and the second variable relief valve 38B to either the off state or the on state. This stops the second linkage member 31. In the internal lock-up state, the third clutch 37 can either disengage or engage, but disengagement is preferred to reduce power loss.

[0152] In order to switch from internal locking to external locking, controller 25... Figure 18 Starting at time B, the control state of the first hydraulic pump motor 33 is set to "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)". For example, the controller 25 sets the first variable relief valve 38A to the off state and the second variable relief valve 38B to the on state. "One direction" refers to the rotational direction of the second connecting structure 31, which is given to transmit the power from the engine 9 through the first connecting structure 30 to the planetary gear mechanism 29, to the third connecting structure 32. Figure 18 Taking the rotational speed characteristic line of the second connecting structural member 31 as an example, it represents a state where rotation in the negative direction is allowed while rotation in the positive direction is prevented. "One direction" corresponds, for example, to the rotational direction of the engine 9. Furthermore, Figure 18 Time B can be the time before switching from internal lockout to external lockout, or it can be that there is no time between time A and time B and the control state of the first hydraulic pump motor 33 is always set to "the state in which rotation stops in one direction and can rotate freely in the opposite direction (the state in which torque is applied in one direction and no torque is applied in the opposite direction)".

[0153] It should be noted that the wheel loader 1 often travels on uneven roads. Therefore, changes in acceleration and deceleration from the road surface are transmitted from the output shaft 23 to the engine 9, resulting in the engine 9 braking and the vehicle speed decreasing. Therefore, even in the internally locked state, the following control is preferable: When the operator depresses the accelerator pedal 8A and power is transmitted in the direction of acceleration of the wheel loader 1, the control state of the first hydraulic pump motor 33 is always set to "a state where rotation stops in one direction and can rotate freely in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)". On the other hand, when the operator releases the accelerator pedal 8A and the engine 9 brakes, requiring the wheel loader 1 to decelerate, the control state of the first hydraulic pump motor 33 is set to "a state where rotation stops in the opposite direction and can rotate freely in one direction (a state where torque is applied in the opposite direction and no torque is applied in one direction)".

[0154] Controller 25 from Figure 18 Starting at time C, the first clutch 27C begins to engage, and engagement is completed at time E. Therefore, after time E, the system enters an externally locked state. Controller 25... Figure 18After time E, the control state of the first hydraulic pump motor 33 is maintained as "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)", or switched to "a state where rotation is free in both directions (a state where no torque is applied in both directions)". For example, the controller 25 sets the first variable relief valve 38A to a cut-off state or a connected state, and sets the second variable relief valve 38B to a connected state. The controller 25 in Figure 18 After time G, the control state of the first hydraulic pump motor 33 is set to "a state in which it can rotate freely in both directions (a state in which no torque is applied in either direction)" or "a state in which it can rotate freely in one direction and stop rotating in the opposite direction (a state in which no torque is applied in one direction but torque is applied in the opposite direction)". For example, the controller 25 sets the first variable relief valve 38A to the connected state and the second variable relief valve 38B to the disconnected state or the connected state. The second clutch 36 can... Figure 18 The clutch disengages after time E. In the externally locked state, the second clutch 36 can be either disengaged or engaged, but disengagement is preferred to reduce power loss.

[0155] On the other hand, refer to Figure 19 , indicating Figure 13 As shown in the first modified example, the transmission state of the planetary continuously variable transmission 24 is switched from "internal lock" to "external lock" by using the structure of internal locking with the braking mechanism 55.

[0156] exist Figure 19 During the internal lock-up state from time A to time B, controller 25 stops the rotation of the second linkage member 31 by engaging (pressurizing) braking mechanism 55. The first clutch 27C disengages. In the internal lock-up state, the third clutch 37 can either disengage or engage, but disengagement is preferred to reduce power loss. The second clutch 36 can be in either disengaged or engaged state. To switch from internal lock-up to external lock-up, controller 25... Figure 19 The second clutch 36 begins to engage at time B and completes engagement at time C. This action is unnecessary if the second clutch 36 is already engaged before time A.

[0157] Controller 25 from Figure 19 Starting at time D, the control state of the first hydraulic pump motor 33 is set to "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)". Then, the controller 25... Figure 19 During the period from time E to time F, the braking mechanism 55 is disengaged (pressure reduced). The controller 25 then... Figure 19At time G, the first clutch 27C begins to engage, and engagement is completed at time I. Therefore, after time I, the clutch becomes externally locked.

[0158] exist Figure 19 After time I, the second clutch 36 can be disengaged. In the externally locked state, the second clutch 36 can be either disengaged or engaged, but disengagement is preferred to reduce power loss. Figure 19 During the transition from time J to time K, the second clutch 36 is disengaged (pressure reduced). The controller 25... Figure 19 After time I, the control state of the first hydraulic pump motor 33 is maintained as "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)", or switched to "a state where rotation is free in both directions (a state where no torque is applied in both directions)". Figure 19 After time K, the control state of the first hydraulic pump motor 33 is set to "a state in which it can rotate freely in one direction and stop rotating in the opposite direction (a state in which no torque is applied in one direction but torque is applied in the opposite direction)" or "a state in which it can rotate freely in both directions (a state in which no torque is applied in both directions)".

[0159] Next, refer to Figure 20 This explains the situation where the transmission state of the planetary continuously variable transmission mechanism 24 switches from "external lock-up" to "internal lock-up".

[0160] In structures such as those in Tables 1 and 2 above, when the speed levels of the multi-stage transmission mechanism 26 are forward 1st gear, forward 2nd gear, forward 3rd gear, and backward 1st gear, a switching from external lock-up to internal lock-up is envisioned. Figure 20 During the external lock-up state from time A to time B, controller 25 engages the first clutch 27C and disengages the second clutch 36. Additionally, controller 25 sets the control state of the first hydraulic pump motor 33 to "a state where it can rotate freely in both directions (a state where no torque is applied in either direction)". In the external lock-up state, the second clutch 36 and the third clutch 37 can either disengage or engage, but disengagement is preferred to reduce power loss.

[0161] In order to switch from external locking to internal locking, controller 25... Figure 20 From time B to time F, the control state of the first hydraulic pump motor 33 is set to "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)". That is, if... Figure 20For example, the rotational speed characteristic curve of the second connecting structure 31 is such that it allows rotation in the negative direction and prevents rotation in the positive direction. The controller 25 causes the second clutch 36 to engage during the period from time B to time C. Therefore, the second connecting structure 31 rotates integrally with the first hydraulic pump motor 33. Furthermore, Figure 20 The second clutch 36 is always engaged, either before the switch from external locking to internal locking occurs or during the absence of time A to time C.

[0162] Controller 25 from Figure 20 Starting at time D, the first clutch 27C begins to disengage, and disengagement is completed at time F. This completes the switch from external lock-up to internal lock-up. Controller 25... Figure 20 After time F, the control state of the first hydraulic pump motor 33 is maintained as "the rotation stops in one direction and can rotate freely in the opposite direction (the torque is applied in one direction and no torque is applied in the opposite direction)", or switched to "the rotation stops in both directions (the torque is applied in both directions)".

[0163] On the other hand, refer to Figure 21 , indicating Figure 13 As shown in the first modified example, the transmission state of the planetary continuously variable transmission 24 is switched from "external lock" to "internal lock" by using the braking mechanism 55 for internal locking.

[0164] exist Figure 21 During the external lock-up state from time A to time B, controller 25 engages the first clutch 27C, disengages the second clutch 36, and disengages the braking mechanism 55 (pressure reduction). Additionally, controller 25 sets the control state of the first hydraulic pump motor 33 to "a state where it can rotate freely in both directions (a state where no torque is applied in either direction)". In the external lock-up state, the second clutch 36 and the third clutch 37 can either disengage or engage, but disengagement is preferred to reduce power loss.

[0165] In order to switch from external locking to internal locking, controller 25... Figure 21 From time B to time F, the control state of the first hydraulic pump motor 33 is set to "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)". That is, if... Figure 21For example, the rotational speed characteristic curve of the second connecting structure 31 is such that it allows rotation in the negative direction and prevents rotation in the positive direction. The controller 25 causes the second clutch 36 to engage during the period from time B to time C. Therefore, the second connecting structure 31 rotates integrally with the first hydraulic pump motor 33. Furthermore, Figure 21 The second clutch 36 is always engaged, either before the switch from external locking to internal locking occurs or during the absence of time A to time C.

[0166] Controller 25 from Figure 21 Starting at time D, the first clutch 27C begins to disengage, and disengagement is completed at time F. Controller 25... Figure 21 During time F, the control state of the first hydraulic pump motor 33 is maintained as "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)", or switched to "a state where rotation stops in both directions (a state where torque is applied in both directions)". The controller 25 then... Figure 21 During time G to time H, the braking mechanism 55 engages (increases pressure), completely stopping the rotation of the second connecting structural member 31. This completes the switch from the external locking state to the internal locking state. Figure 21 After time H, the control state of the first hydraulic pump motor 33 can be either "the state in which rotation is stopped in both directions (the state in which torque is applied in both directions)" or "the state in which rotation can be freely performed in both directions (the state in which no torque is applied in both directions)". For example, the controller 25 sets the first variable relief valve 38A and the second variable relief valve 38B to the cut-off state or the connected state.

[0167] in addition, Figures 18 to 25 The following Figure 33 as well as Figure 34 This example illustrates gear shifting while maintaining a constant vehicle speed, but the invention is not limited to this. Gear shifting can also be performed while decelerating or accelerating.

[0168] Next, the gear shifting (switching) performed by the multi-stage transmission mechanism 26 will be explained. As shown in Table 4 above, the multi-stage transmission mechanism 26 can shift (switch) to forward 1st gear, forward 2nd gear, forward 3rd gear, and backward 1st gear.

[0169] Imagine shifting gears using the following combinations: forward 1st gear to forward 2nd gear, forward 1st gear to forward 3rd gear, forward 1st gear to reverse 1st gear, forward 2nd gear to forward 1st gear, forward 2nd gear to forward 3rd gear, forward 2nd gear to reverse 1st gear, forward 3rd gear to forward 2nd gear, forward 3rd gear to forward 1st gear, forward 3rd gear to reverse 1st gear, reverse 1st gear to forward 1st gear, reverse 1st gear to forward 2nd gear, and reverse 1st gear to forward 3rd gear. As the forward 1st gear clutch 69, reverse 1st gear clutch 70, forward 2nd gear clutch 75, and forward 3rd gear clutch 76 (as shown in Table 4) engage and disengage, the multi-stage transmission mechanism 26 performs gear shifting, i.e., speed level switching.

[0170] Figure 26 This is a characteristic graph (time graph) showing an example of the time-varying pressure of the primary clutch (clutch that switches from engagement to disengagement), the secondary clutch (clutch that switches from disengagement to engagement), and the non-interrelated clutch (clutch that remains disengaged) during speed changes (speed level switching) of the multi-stage transmission mechanism 26. Furthermore, during speed changes in the multi-stage transmission mechanism 26, the clutch engaged before the speed change is designated as the primary clutch, the clutch engaged after the speed change is designated as the secondary clutch, and the clutch disengaged both before and after the speed change is designated as the non-interrelated clutch.

[0171] For example, when shifting from 1st gear to 2nd gear, the 1st gear clutch 69 becomes a disengagement clutch, the 2nd gear clutch 75 becomes a receptive clutch, and the 1st gear clutch 70 and the 3rd gear clutch 76 become unrelated clutches. Figure 26 During the period from time A to time B (i.e., before shifting gears), the disengagement clutch engages, and the retraction clutch disengages. Controller 25 from Figure 26 At time B, the pressure of the retraction clutch begins to decrease. Controller 25, via... Figure 26 During time D, the pressure of the release clutch is fully reduced, completing the disengagement of the release clutch. Controller 25 from Figure 26 At time C, the pressure of the receiving clutch begins to rise. Controller 25, via... Figure 26 The time E during which the pressure of the engaging clutch fully increases, completing the disengagement of the disengaging clutch. Therefore, in Figure 26 The multi-stage transmission mechanism 26 completes its speed change within time E. The unrelated clutch remains disengaged before and after the speed change.

[0172] Next, the simultaneous switching between the planetary continuously variable transmission (CVT) 24 and the multi-stage transmission 26 will be explained. First, refer to... Figure 27This describes the situation where the planetary continuously variable transmission 24 switches from "internal lock-up" to "external lock-up" and the multi-stage transmission 26 also changes speed (switches).

[0173] In the structures of Tables 1 and 2 above, for example, imagine that the gear shift (switching) occurs between forward 1st gear internal lock-up and forward 2nd gear external lock-up, forward 1st gear internal lock-up and forward 3rd gear external lock-up, forward 2nd gear internal lock-up and forward 3rd gear external lock-up, forward 2nd gear internal lock-up and forward 1st gear external lock-up, forward 3rd gear internal lock-up and forward 2nd gear external lock-up, and forward 3rd gear internal lock-up and forward 1st gear external lock-up. That is, the gear shift (switching) does not switch the transmission states shown in Tables 1 and 2 in the order of the tables, but corresponds to the case of skipping a part of the gear shift (skipping gear shifting). Figure 27 This is a characteristic graph (time graph) showing an example of the time variation of the pressure of the first clutch 27C of the planetary continuously variable transmission 24, the pressure of the second clutch 36, the pressure of the disengagement clutch (clutch switching from engagement to disengagement) of the multi-stage transmission 26, the pressure of the receiving clutch (clutch switching from disengagement to engagement) of the multi-stage transmission 26, and the rotational speed of the second connecting member 31 during the speed change (switching).

[0174] exist Figure 27 During the internal lock-up state from time A to time B, controller 25 engages the second clutch 36, disengages the first clutch 27C, engages the retraction clutch, and disengages the receptive clutch. Furthermore, controller 25 sets the control state of the first hydraulic pump motor 33 to either "a state where rotation is stopped in both directions (a state where torque is applied in both directions)" or "a state where rotation is stopped in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)." This stops the second linkage member 31. In the internal lock-up state, the third clutch 37 can either disengage or engage, but disengagement is preferred to reduce power loss.

[0175] In order to switch from internal locking to external locking, controller 25... Figure 27 Starting at time B, the control state of the first hydraulic pump motor 33 is set to "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)". The controller 25 then... Figure 27 Starting at time C, the first clutch 27C begins to engage, and engagement is completed at time G. Consequently, the second clutch member 31 begins to rotate in the opposite direction, and after time G, it enters an externally locked state. Meanwhile, the controller 25... Figure 27Starting at time D, the release clutch begins to disengage, and disengagement is completed at time F. That is, controller 25 causes the release clutch to depressurize from time D until depressurization is complete at time F. Additionally, controller 25... Figure 27 The receiving clutch begins to engage at time E and completes engagement at time H. That is, the controller 25 causes the receiving clutch to pressurize from time E to time H.

[0176] Then, controller 25 from Figure 27 The controller 25 causes the second clutch 36 to disengage during time I to time J. That is, the controller 25 causes the pressure of the second clutch 36 to decrease during time I to time J. Figure 27 After time H, the control state of the first hydraulic pump motor 33 is switched to either "a state where it can rotate freely in one direction and stop rotating in the opposite direction (a state where no torque is applied in one direction but torque is applied in the opposite direction)" or "a state where it can rotate freely in both directions (a state where no torque is applied in both directions)". The second clutch 36 can... Figure 27 The clutch will disengage after time H. The second clutch 36 can be either disengaged or engaged, but disengagement is preferred to reduce power loss.

[0177] Furthermore, although not illustrated, the pressure of the unrelated clutches (i.e., clutches other than the disengagement clutch and the receptive clutch) of the multi-stage transmission mechanism 26 is always reduced to 0 before and after the gear shift (switching) (the unrelated clutches are disengaged beforehand). Thus, when the planetary continuously variable transmission mechanism 24 is switched from "internal lock-up" to "external lock-up" and the multi-stage transmission mechanism 26 is also shifting (switching), the planetary continuously variable transmission mechanism 24 is switched from "internal lock-up" to "external lock-up" first, and then the multi-stage transmission mechanism 26 shifts (switches). That is, the first clutch 27C is started to increase pressure (engage) before the disengagement clutch depressurizes (disengages) and the receptive clutch increases pressure (engages).

[0178] On the other hand, refer to Figure 28 , indicating Figure 13 As shown in the first modified example, the structure of internal locking using the braking mechanism 55 allows the transmission state of the planetary continuously variable transmission 24 to switch from "internal locking" to "external locking", and the multi-stage transmission mechanism 26 also changes speed (switches).

[0179] exist Figure 28During the internal lock-up state from time A to time B, controller 25 engages (pressurizes) braking mechanism 55, thereby stopping the rotation of the second linkage member 31. The first clutch 27C disengages. In the internal lock-up state, the third clutch 37 can either disengage or engage, but disengagement is preferred to reduce power loss. The second clutch 36 can be in either disengaged or engaged state. The control state of the first hydraulic pump motor 33 can be either "a state that stops rotation in both directions (a state with torque acting in both directions)" or "a state that allows free rotation in both directions (a state without torque acting in both directions)".

[0180] In order to switch from internal locking to external locking, controller 25... Figure 28 Starting at time B, the second clutch 36 begins to engage (pressurize), and engagement (pressurization) is completed at time C. Then, the controller 25... Figure 28 Starting at time D, the control state of the first hydraulic pump motor 33 is switched to "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)". The controller 25 then... Figure 28 From time E to time F, the braking mechanism 55 disengages (pressure is reduced). The controller 25 then... Figure 28 Starting at time G, the first clutch 27C begins to engage, and engagement is completed at time J. Consequently, the second clutch member 31 begins to rotate in the opposite direction, and after time J, it enters an externally locked state. Meanwhile, the controller 25... Figure 28 Starting at time H, the retraction clutch begins to disengage, and disengagement is completed at time K. That is, controller 25 causes the retraction clutch to depressurize from time H to time K. Additionally, controller 25... Figure 28 Starting at time I, the receiving clutch begins to engage, and engagement is completed at time L. That is, the controller 25 causes the receiving clutch to pressurize from time I to time L.

[0181] Controller 25 Figure 28 After time L, the control state of the first hydraulic pump motor 33 is switched to either "a state in which it can rotate freely in one direction and stop rotating in the opposite direction (a state in which no torque is applied in one direction but torque is applied in the opposite direction)" or "a state in which it can rotate freely in both directions (a state in which no torque is applied in both directions)". The second clutch 36 can... Figure 28 Separation occurs after time L. Figure 28 During the transition from time M to time N, the second clutch 36 is disengaged. Specifically, the controller 25 reduces the pressure on the second clutch 36 from time M to time N. The second clutch 36 can be either disengaged or engaged, but disengagement is preferred to minimize power loss.

[0182] Furthermore, although the illustration is omitted, the pressure of the unrelated clutches (i.e., clutches other than the disengagement clutch and the receptive clutch) of the multi-stage transmission mechanism 26 always drops to 0 before and after the gear shift (switching) (the unrelated clutches disengage beforehand). Thus, when the planetary continuously variable transmission mechanism 24 is switched from "internal lock-up" to "external lock-up" and the multi-stage transmission mechanism 26 also shifts (switches), the switching of the planetary continuously variable transmission mechanism 24 from "internal lock-up" to "external lock-up" begins first, followed by the gear shift (switching) of the multi-stage transmission mechanism 26. That is, the first clutch 27C begins to increase pressure (engage) before the disengagement clutch depressurizes (disengages) and the receptive clutch increases pressure (engages).

[0183] Next, refer to Figure 29 This describes the situation where the planetary continuously variable transmission 24 switches from "external lock-up" to "internal lock-up" and the multi-stage transmission 26 also changes speed (switches).

[0184] In the structures of Tables 1 and 2 above, for example, imagine shifting gears by using the following gear shifts: forward 1st gear external lock to forward 2nd gear internal lock, forward 1st gear external lock to forward 3rd gear internal lock, forward 2nd gear external lock to forward 3rd gear internal lock, forward 2nd gear external lock to forward 1st gear internal lock, forward 3rd gear external lock to forward 2nd gear internal lock, and forward 3rd gear external lock to forward 1st gear internal lock.

[0185] From Figure 29 During the external lock-up state from time A to time B, controller 25 engages the first clutch 27C, disengages the second clutch 36, engages the retraction clutch, and disengages the receptive clutch. Furthermore, controller 25 sets the control state of the first hydraulic pump motor 33 to either "a state where it can rotate freely in one direction and stops rotating in the opposite direction (a state where no torque is applied in one direction but torque is applied in the opposite direction)" or "a state where it can rotate freely in both directions (a state where no torque is applied in both directions)". In the external lock-up state, the second clutch 36 and the third clutch 37 can either disengage or engage, but disengagement is preferred to reduce power loss.

[0186] In order to switch from external locking to internal locking, controller 25... Figure 29During time B to time C, the control state of the first hydraulic pump motor 33 is set to "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)". During time B to time C, the controller 25 engages the second clutch 36. As a result, the second coupling member 31 rotates integrally with the first hydraulic pump motor 33. Furthermore, Figure 29 The time B in the text can be the period before switching from external locking to internal locking, or it can be the period between time A and time C, during which the second clutch 36 is always engaged.

[0187] On the other hand, controller 25 from Figure 29 During the time interval D to time F, the pressure of the retraction clutch decreases, causing the retraction clutch to disengage. Additionally, controller 25... Figure 29 During time E to time H, the pressure of the receiving clutch increases, causing the receiving clutch to engage. Clutch 27C from... Figure 29 Separation begins at time G and is completed at time I. Therefore, the rotation of the second connecting structural member 31 stops. The controller 25 then... Figure 29 Starting at time I, the control state of the first hydraulic pump motor 33 is set to either "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)" or "a state where rotation stops in both directions (a state where torque is applied in both directions)". This completes the speed change (switching).

[0188] Furthermore, although the illustration is omitted, the pressure of the unrelated clutches (i.e., clutches other than the disengagement clutch and the receptive clutch) of the multi-stage transmission mechanism 26 always drops to 0 before and after the gear shift (switching) (the unrelated clutches disengage beforehand). Thus, when the planetary continuously variable transmission mechanism 24 is switched from "external lock-up" to "internal lock-up" and the multi-stage transmission mechanism 26 is also shifting (switching), the gear shift (switching) of the multi-stage transmission mechanism 26 begins first, followed by the shift of the planetary continuously variable transmission mechanism 24 from "external lock-up" to "internal lock-up". That is, before the first clutch 27C begins to depressurize (disengage), the depressurization (disengagement) of the disengagement clutch and the engagement (engagement) of the receptive clutch begin.

[0189] On the other hand, refer to Figure 30 , indicating Figure 13 As shown in the first modified example, the structure of internal locking using the braking mechanism 55 allows the transmission state of the planetary continuously variable transmission 24 to switch from "external locking" to "internal locking", and the multi-stage transmission mechanism 26 also changes speed (switches).

[0190] exist Figure 30During the external lock-up state from time A to time B, controller 25 engages the first clutch 27C, disengages the second clutch 36, disengages the braking mechanism 55, engages the retraction clutch, and disengages the receiving clutch. Furthermore, controller 25 sets the control state of the first hydraulic pump motor 33 to either "a state where it can rotate freely in one direction and stops rotating in the opposite direction (a state where no torque is applied in one direction but torque is applied in the opposite direction)" or "a state where it can rotate freely in both directions (a state where no torque is applied in both directions)". In the external lock-up state, the second clutch 36 and the third clutch 37 can either disengage or engage, but disengagement is preferred to reduce power loss.

[0191] In order to switch from external locking to internal locking, controller 25... Figure 30 During time B to time C, the control state of the first hydraulic pump motor 33 is set to "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)". During time B to time C, the controller 25 engages the second clutch 36. As a result, the second coupling member 31 rotates integrally with the first hydraulic pump motor 33. Furthermore, Figure 30 The time B in the text can be the period before switching from external locking to internal locking, or it can be the period between time A and time C, during which the second clutch 36 is always engaged.

[0192] On the other hand, controller 25 from Figure 30 During the time interval D to time F, the pressure of the retraction clutch decreases, causing the retraction clutch to disengage. Additionally, controller 25... Figure 30 During time E to time H, the pressure of the receiving clutch increases, causing the receiving clutch to engage. Clutch 27C from... Figure 30 Separation begins at time G and is completed at time I. Therefore, the rotation of the second connecting structural member 31 stops. The controller 25 then... Figure 30 Starting at time I, the control state of the first hydraulic pump motor 33 is set to either "a state where rotation stops in one direction and rotation is free in the opposite direction (a state where torque is applied in one direction and no torque is applied in the opposite direction)" or "a state where rotation stops in both directions (a state where torque is applied in both directions)". This completes the speed change (switching). Then, the controller 25... Figure 30 During the time interval J to time K, the pressure of the braking mechanism 55 increases, causing the braking mechanism 55 to engage. Figure 30 After time K, the control state of the first hydraulic pump motor 33 can be either "the state of stopping rotation in both directions (the state of torque acting in both directions)" or "the state of being able to rotate freely in both directions (the state of no torque acting in both directions)".

[0193] Furthermore, although the illustration is omitted, the pressure of the unrelated clutches (i.e., clutches other than the disengagement clutch and the receptive clutch) of the multi-stage transmission mechanism 26 is always reduced to 0 before and after the gear shift (switching) (the unrelated clutches are disengaged beforehand). Thus, when the planetary continuously variable transmission mechanism 24 is switched from "external lock-up" to "internal lock-up" and the multi-stage transmission mechanism 26 is also shifting (switching), the gear shift (switching) of the multi-stage transmission mechanism 26 begins first, followed by the shift of the planetary continuously variable transmission mechanism 24 from "external lock-up" to "internal lock-up". That is, before the first clutch 27C begins to depressurize (disengage), the depressurization (disengagement) of the disengagement clutch and the pressurization (engagement) of the receptive clutch begin.

[0194] Next, refer to Figure 31 This explains why, when the planetary continuously variable transmission 24 is switched from "internal lock" to "external lock" and the multi-stage transmission 26 is also shifting (switching), the switching of the planetary continuously variable transmission 24 is started first, followed by the shifting (switching) of the multi-stage transmission 26.

[0195] Figure 31 The vertical axis corresponds to the reduction ratio from the engine 9, which becomes the power source, to the output shaft 23, and the horizontal axis corresponds to time. Additionally, Figure 31 The characteristic lines A, B, C, and D in the diagram represent the four gear ratio changes resulting from the different timing of switching from internal locking to external locking and the different timing of the multi-stage gear mechanism 26 shifting (switching). Figure 31 Characteristic line A in the diagram represents the situation where the multi-stage transmission mechanism 26 downshifts in the internal lock-up state, and then switches from internal lock-up to external lock-up. In this case, the reduction ratio increases at one point and then decreases. Such a transmission is unsuitable because it can easily lead to a greater interruption in power transmission from the engine 9, which serves as the power source, to the output shaft 23.

[0196] Figure 31 Characteristic line B in the diagram represents the case where the shift from internal lock-up to external lock-up occurs, followed by downshifting of the multi-stage transmission mechanism 26. In this case, the reduction ratio decreases initially and then increases. This type of shift minimizes the interruption in power transmission from the engine 9, which serves as the power source, to the output shaft 23, and is therefore suitable. That is, although characteristic lines A and B ultimately result in the same reduction ratio, the degree of power interruption differs significantly. Therefore, when shifting from internal lock-up to external lock-up and the multi-stage transmission mechanism 26 also shifts (switches), it is important to initiate the shift from internal lock-up to external lock-up first, followed by the shifting (switching) of the multi-stage transmission mechanism 26.

[0197] Figure 31Characteristic line C in the diagram represents the switching from internal lock-up to external lock-up, followed by upshifting of the multi-stage transmission mechanism 26. In this case, the reduction ratio decreases continuously. Such transmission minimizes interruptions in power transmission from the engine 9, which serves as the power source, to the output shaft 23, making it suitable. Figure 31 Characteristic line D in the diagram represents the situation where the multi-stage transmission mechanism 26 upshifts in the internal lock-up state and then switches from internal lock-up to external lock-up. In this case, the reduction ratio also decreases continuously. This type of transmission minimizes the interruption of power transmission from the engine 9, which serves as the power source, to the output shaft 23, making it suitable. Furthermore, characteristic lines C and D ultimately achieve the same reduction ratio, so they can be chosen arbitrarily.

[0198] Next, refer to Figure 32 This explains why, when the planetary continuously variable transmission 24 is switched from "external lock" to "internal lock" and the multi-stage transmission 26 is also shifting (switching), the shifting (switching) of the multi-stage transmission 26 is started first, and then the switching of the planetary continuously variable transmission 24 is performed.

[0199] Figure 32 The vertical axis corresponds to the reduction ratio from the engine 9, which becomes the power source, to the output shaft 23, and the horizontal axis corresponds to time. Additionally, Figure 32 The characteristic lines A, B, C, and D in the diagram represent the four gear ratio changes resulting from the different timing of switching from external locking to internal locking and the different timing of the multi-stage gear mechanism 26 shifting (switching). Figure 32 Characteristic line A in the diagram represents the situation where the multi-stage transmission mechanism 26 downshifts under external lock-up conditions, and then switches from external lock-up to internal lock-up. In this case, the reduction ratio increases in stages. Although such a transmission is prone to increasing the interruption of power transmission from the engine 9, which serves as the power source, to the output shaft 23, there is no way to avoid it, so it is suitable.

[0200] Figure 32 Characteristic line B in the diagram represents the transition from external lock-up to internal lock-up, followed by downshifting of the multi-stage transmission mechanism 26. In this case, the reduction ratio increases in stages. Although such a shift can easily lead to greater interruptions in power transmission from the engine 9, which serves as the power source, to the output shaft 23, there is no way to avoid this, so it is suitable. Furthermore, characteristic lines A and B ultimately result in the same reduction ratio, so they can be chosen arbitrarily. Figure 32 Characteristic line C in the diagram represents the switching from external lock-up to internal lock-up, followed by upshifting of the multi-stage transmission mechanism 26. In this case, the reduction ratio initially increases and then decreases. Such a transmission is unsuitable because it can easily lead to greater interruptions in power transmission from the engine 9, which serves as the power source, to the output shaft 23.

[0201] Figure 32Characteristic line D in the diagram represents the case where the multi-stage transmission mechanism 26 upshifts in the external lock-up state, and then switches from external lock-up to internal lock-up. In this case, the reduction ratio decreases and then increases. This type of gear shifting minimizes the interruption of power transmission from the engine 9, which becomes the power source, to the output shaft 23, which is appropriate. That is, although characteristic lines C and D ultimately shift to the same reduction ratio, the degree of power interruption is quite different. Therefore, when switching from external lock-up to internal lock-up and upshifting the multi-stage transmission mechanism 26, it is important to start the gear shifting (switching) of the multi-stage transmission mechanism 26 first, and then switch from internal lock-up to external lock-up.

[0202] Next, refer to Figure 33 This describes the situation where the planetary continuously variable transmission mechanism 24 switches from "continuously variable transmission" to "external lock-up" and the multi-stage transmission mechanism 26 also changes speed (switches).

[0203] Based on the structure in Table 2 above, it is conceivable that this gear shift (switching) is performed using a 3rd gear continuously variable transmission (CVT) to a 2nd gear external lock-up, a 3rd gear CVT to a 1st gear external lock-up, and a 2nd gear CVT to a 1st gear external lock-up. Figure 33 This is a characteristic graph (time graph) showing an example of the time variation of the reduction ratio from the engine 9, which becomes the power source, to the output shaft 23, the pressure of the first clutch 27C (lock-up clutch) of the planetary continuously variable transmission 24, the pressure of the second clutch 36, the pressure of the disengagement clutch (clutch that switches from engagement to disengagement) of the multi-stage transmission 26, and the pressure of the receiving clutch (clutch that switches from disengagement to engagement) of the multi-stage transmission 26 during the gear change.

[0204] exist Figure 33 In the continuously variable transmission (CVT) state between time A and time B, controller 25 engages the second clutch 36 and the third clutch 37, disengaging the first clutch 27C. In this state, controller 25 adjusts the rotational speed of the first hydraulic pump motor 33 and adjusts the rotation of the second connecting member 31 to achieve the target reduction ratio. To switch from this CVT state, controller 25 adjusts the reduction ratio from engine 9 to output shaft 23 via planetary CVT mechanism 24 by adjusting the rotational speed of the first hydraulic pump motor 33. In this case, the reduction ratio from engine 9 to output shaft 23 via planetary CVT mechanism 24 in the state before switching of multi-stage transmission mechanism 26 is made close to the reduction ratio from engine 9 to output shaft 23 via direct connection mechanism 27 in the state after switching of multi-stage transmission mechanism 26. At this time, it is not necessary for the reduction ratios to be exactly the same, just close. Conversely, a reduction ratio that exceeds the target is undesirable. Figure 33 During the period from time B to time C, an action is performed to bring the deceleration ratio closer to the given value.

[0205] in addition, Figure 33 The solid line S in the diagram represents the reduction ratio from engine 9 to output shaft 23 via direct connection mechanism 27 in the state after switching of multi-stage transmission mechanism 26, compared to the reduction ratio from engine 9 to output shaft 23 via planetary continuously variable transmission mechanism 24 in the state before switching of multi-stage transmission mechanism 26. However, this reduction ratio can sometimes be quite large. Figure 33 The dashed line B in the text indicates the reduction ratio from engine 9 to output shaft 23 via direct connection mechanism 27 in the state after switching of multi-stage transmission mechanism 26, and the reduction ratio from engine 9 to output shaft 23 via planetary continuously variable transmission mechanism 24 in the state before switching of multi-stage transmission mechanism 26 is larger.

[0206] Controller 25 from Figure 33 Starting at time D, the control state of the first hydraulic pump motor 33 is set to "a state where torque is applied in one direction and no torque is applied in the opposite direction". Thus, preparation for switching from continuously variable transmission (CVT) to external lock-up is completed simply by increasing the pressure of the first clutch 27C. The controller 25 then... Figure 33 Starting at time D, the pressure of the first clutch 27C increases, and at time H, the first clutch 27C is fully engaged. Controller 25... Figure 33 Starting at time E, the pressure of the retraction clutch decreases, and at time G, the retraction clutch completely disengages. Additionally, controller 25... Figure 33 At time F, the pressure of the receiving clutch increases, and at time I, the receiving clutch completes engagement. Figure 33 After time I, the second clutch 36 and the third clutch 37 can be disengaged. Figure 33 In the middle, starting from time J, the pressure of the second clutch 36 (and the third clutch 37) is reduced, and at time K, the second clutch 36 (and the third clutch 37) is disengaged.

[0207] exist Figure 33After time K, the control state of the first hydraulic pump motor 33 can be either "a state in which it can rotate freely in both directions (a state in which no torque is applied in either direction)" or "a state in which torque is applied in one direction and no torque is applied in the opposite direction". Thus, when the planetary continuously variable transmission 24 switches from "continuously variable transmission" to "externally locked" and the multi-stage transmission 26 also changes speed (switches), the gear ratio of the planetary continuously variable transmission 24 is first changed to be close to the reduction ratio after the multi-stage transmission 26 has completed its gear change. Then, after the planetary continuously variable transmission 24 starts switching from "continuously variable transmission" to "externally locked", the multi-stage transmission 26 begins its gear change (switching). That is, after the first clutch 27C starts increasing pressure (engaging), the disengaging clutch decreases pressure (disengaging) and the engaging clutch increases pressure (engaging).

[0208] In addition, Figure 33 During the period from time D to time K, the controller 25 sets the control state of the first hydraulic pump motor 33 to "a state where a torque load acts in one direction and no torque load acts in the opposite direction". That is, regardless of the rotation direction of the first hydraulic pump motor 33, the controller 25 controls it according to the direction of the torque. Figure 35 As shown, the first hydraulic pump motor 33 has four states: a state in which it rotates in one direction and transmits torque in one direction, a state in which it rotates in one direction and transmits torque in the opposite direction, a state in which it rotates in the opposite direction and transmits torque in one direction, and a state in which it rotates in the opposite direction and transmits torque in the opposite direction.

[0209] exist Figure 33 During the time interval D to K, the first hydraulic pump motor 33 rotates in one direction and transmits torque in that direction. Regarding this speed change, since the change in the rotational speed of the engine 9, which serves as the power source, is minimal during the switching of the clutches (first clutch 27C, second clutch 36, disengagement clutch, and receptive clutch), this speed change can shorten the time required for clutch switching and reduce the variation in output torque from the output shaft 23. Therefore, the operability of the wheel loader 1 can be improved, and passenger comfort can be enhanced.

[0210] Next, refer to Figure 34 This describes the situation where the planetary continuously variable transmission mechanism 24 switches from "external lock" to "continuously variable transmission" and the multi-stage transmission mechanism 26 also changes speed (switches).

[0211] Based on the structure in Table 2 above, imagine performing this gear shift (switching) with the following gear shifts: forward 1st gear external lock to forward 2nd gear CVT, forward 1st gear external lock to forward 3rd gear CVT, forward 1st gear external lock to rear 1st gear CVT, forward 2nd gear external lock to forward 3rd gear CVT, forward 2nd gear external lock to forward 1st gear CVT, forward 2nd gear external lock to rear 1st gear CVT, forward 3rd gear external lock to forward 2nd gear CVT, forward 3rd gear external lock to forward 1st gear CVT, and forward 3rd gear external lock to rear 1st gear CVT.

[0212] exist Figure 34 During the external lock-up state from time A to time B, controller 25 engages the first clutch 27C and disengages the second clutch 36. Furthermore, controller 25 sets the control state of the first hydraulic pump motor 33 to either "a state where it can rotate freely in both directions (a state where no torque is applied in either direction)" or "a state where torque is applied in one direction and no torque is applied in the opposite direction." In the external lock-up state, the second clutch 36 and the third clutch 37 can either disengage or engage, but disengagement is preferred to reduce power loss.

[0213] During time intervals B and C, controller 25 engages the second clutch 36 and the third clutch 37. This causes the second coupling member 31 and the first hydraulic pump motor 33 to rotate integrally, enabling power transmission between the second hydraulic pump motor 34 and the idler wheel element 28 (idler wheel shaft 28A). Controller 25 adjusts the reduction ratio from engine 9 to output shaft 23 via planetary continuously variable transmission (CVT) 24 by adjusting the rotational speed of the first hydraulic pump motor 33. In this case, the reduction ratio from engine 9 to output shaft 23 via CVT 24 in the state after switching of multi-stage transmission 26 is made close to the reduction ratio from engine 9 to output shaft 23 via direct connection mechanism 27 in the state before switching of multi-stage transmission 26. At this time, it is not necessary for the reduction ratios to be exactly the same, just close. Conversely, a reduction ratio that exceeds the limit is undesirable. Figure 34 During the period from time D to time K, an action is performed to bring the deceleration ratio closer to the given value.

[0214] Controller 25 Figure 34 During the period from time D to time K, the control state of the first hydraulic pump motor 33 is set to "a state where torque is applied in one direction and no torque is applied in the opposite direction". Thus, preparation for switching from external lock-up to continuously variable transmission is completed simply by reducing the pressure of the first clutch 27C. The controller 25 then... Figure 34Starting at time F, the pressure of the retraction clutch decreases, and at time I, the retraction clutch is fully disengaged. Additionally, controller 25... Figure 34 At time G, the pressure of the receiving clutch increases, and at time K, the receiving clutch completes engagement.

[0215] Controller 25 from Figure 34 At time H, the pressure of the first clutch 27C decreases, and at time J, the first clutch 27C disengages. Figure 34 After time K, the control state of the first hydraulic pump motor 33 becomes a state in which the reduction ratio of the planetary continuously variable transmission mechanism 24 is adjusted by adjusting the rotational speed. That is, the controller 25 adjusts the rotational speed of the first hydraulic pump motor 33, and in order to achieve the target reduction ratio, adjusts the rotation of the second connecting component 31.

[0216] Thus, when the planetary continuously variable transmission (CVT) 24 switches from "external lock-up" to "CVT" and the multi-stage transmission 26 also shifts (switches), the gear ratio of the planetary CVT 24 is first changed to be close to the reduction ratio of the multi-stage transmission 26 after the shift is completed. Then, after the multi-stage transmission 26 begins shifting (switching), the planetary CVT 24 begins switching from "external lock-up" to "CVT". That is, after the disengagement clutch begins depressurization (disengagement) and the engagement clutch begins depressurization (engagement), the first clutch 27C begins depressurization (disengagement).

[0217] Because the change in the rotational speed of the engine 9, which serves as the power source, is minimal during the switching of the clutches (first clutch 27C, second clutch 36, disengagement clutch, and receptive clutch), the aforementioned gear shifting can shorten the time required for clutch switching and reduce the variation in output torque from the output shaft 23. This improves the operability of the wheel loader 1 and enhances passenger comfort.

[0218] Next, refer to Figure 7 The relationship between the connected and disconnected states of the variable relief valves 38A and 38B and the rotation direction and torque load direction of the first hydraulic pump motor 33 is explained in further detail.

[0219] First, let's explain the situation when the set pressure of both the first variable relief valve 38A and the second variable relief valve 38B is high, that is, when both the first variable relief valve 38A and the second variable relief valve 38B are in the off state.

[0220] First, let's explain the case where the engine 9 (power source) rotates clockwise towards the output shaft 23 (axle), applying a clockwise torque to the first connecting member 30, while the second connecting member 31 rotates clockwise (in one direction). In this case, the clockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a clockwise (in one direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the first main pipe 35A, the second hydraulic pump motor 34, and the second main pipe 35B, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the second hydraulic pump motor 34 is reduced relative to the discharge flow rate of the first hydraulic pump motor 33. Therefore, the first main pipeline 35A becomes high pressure relative to the second main pipeline 35B, enabling a torque load in one direction to be applied to the first hydraulic pump motor 33. That is, the first hydraulic pump motor 33 can be configured to rotate in one direction and be subjected to a torque load in that direction.

[0221] This describes a scenario where, from the direction of the engine 9 (power source) towards the output shaft 23 (axle), the engine 9 rotates clockwise, applying a counterclockwise torque to the first connecting member 30, while the second connecting member 31 rotates clockwise (in one direction). In this case, the counterclockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a counterclockwise (opposite direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the first main pipeline 35A, the second hydraulic pump motor 34, and the second main pipeline 35B, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the first hydraulic pump motor 33 is reduced relative to the discharge flow rate of the second hydraulic pump motor 34. As a result, the second main pipeline 35B becomes high pressure relative to the first main pipeline 35A, allowing the opposite direction torque load to act on the first hydraulic pump motor 33. That is, the first hydraulic pump motor 33 can be configured to rotate in one direction and act with a torque load in the opposite direction.

[0222] This describes a scenario where, from the direction of the engine 9 (power source) towards the output shaft 23 (axle), the engine 9 rotates clockwise, applying a clockwise torque to the first connecting member 30, while the second connecting member 31 rotates counterclockwise (in the opposite direction). In this case, the clockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a clockwise (one direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the second main line 35B, the second hydraulic pump motor 34, and the first main line 35A, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the second hydraulic pump motor 34 is reduced relative to the discharge flow rate of the first hydraulic pump motor 33. As a result, the first main line 35A becomes high pressure relative to the second main line 35B, allowing a one-way torque load to act on the first hydraulic pump motor 33. That is, the first hydraulic pump motor 33 can be configured to rotate in the opposite direction while being subjected to a torque load in one direction.

[0223] This describes a scenario where, from the direction of the engine 9 (power source) towards the output shaft 23 (axle), the engine 9 rotates clockwise, applying a counterclockwise torque to the first connecting member 30, while the second connecting member 31 rotates counterclockwise (in the opposite direction). In this case, the counterclockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a counterclockwise (opposite direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the second main line 35B, the second hydraulic pump motor 34, and the first main line 35A, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the first hydraulic pump motor 33 is reduced relative to the discharge flow rate of the second hydraulic pump motor 34. As a result, the second main line 35B becomes high pressure relative to the first main line 35A, allowing the opposite direction torque load to act on the first hydraulic pump motor 33. That is, the first hydraulic pump motor 33 can be configured to rotate in the opposite direction and act with a torque load in the opposite direction.

[0224] Next, the case where the set pressure of the first variable relief valve 38A is low and the set pressure of the second variable relief valve 38B is high, that is, the first variable relief valve 38A is in the connected state and the second variable relief valve 38B is in the cut-off state, will be explained.

[0225] First, let's explain the case where the engine 9 (power source) rotates clockwise towards the output shaft 23 (axle), applying a clockwise torque to the first connecting member 30, while the second connecting member 31 rotates clockwise (in one direction). In this case, the clockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a clockwise (in one direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the first main pipe 35A, the second hydraulic pump motor 34, and the second main pipe 35B, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the second hydraulic pump motor 34 is reduced relative to the discharge flow rate of the first hydraulic pump motor 33. Therefore, the first main pipeline 35A becomes high pressure relative to the second main pipeline 35B, aiming to apply a torque load in one direction to the first hydraulic pump motor 33. However, since the first variable relief valve 38A is in the open state, the working fluid flows sequentially through the first main pipeline 35A, connecting line 44, first bypass line 45, first variable relief valve 38A, and second check valve 48 to the second main pipeline 35B. Therefore, the first main pipeline 35A does not become high pressure relative to the second main pipeline 35B. That is, the first hydraulic pump motor 33 can be set to a state where it rotates in one direction but is not subjected to a torque load in that direction.

[0226] This describes a scenario where, from the direction of engine 9 (power source) towards output shaft 23 (axle), engine 9 rotates clockwise, applying a counterclockwise torque to the first connecting member 30, while the second connecting member 31 rotates clockwise (in one direction). In this case, the counterclockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a counterclockwise (opposite direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the first main pipeline 35A, the second hydraulic pump motor 34, and the second main pipeline 35B, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the first hydraulic pump motor 33 is reduced relative to the discharge flow rate of the second hydraulic pump motor 34. Therefore, the second main pipeline 35B becomes high pressure relative to the first main pipeline 35A, enabling a torque load in the opposite direction to be applied to the first hydraulic pump motor 33. That is, the first hydraulic pump motor 33 can be configured to rotate in one direction while being subjected to a torque load in the opposite direction.

[0227] This describes a scenario where, from the direction of the engine 9 (power source) toward the output shaft 23 (axle), the engine 9 rotates clockwise, applying a clockwise torque to the first connecting member 30, while the second connecting member 31 rotates counterclockwise (in the opposite direction). In this case, the clockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a clockwise (one direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the second main line 35B, the second hydraulic pump motor 34, and the first main line 35A, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the second hydraulic pump motor 34 is reduced relative to the discharge flow rate of the first hydraulic pump motor 33. Therefore, the first main pipeline 35A becomes high pressure relative to the second main pipeline 35B, aiming to apply a torque load in one direction to the first hydraulic pump motor 33. However, since the first variable relief valve 38A is in the open state, the working fluid flows sequentially through the first main pipeline 35A, connecting line 44, first bypass line 45, first variable relief valve 38A, and second check valve 48 towards the second main pipeline 35B. Therefore, the first main pipeline 35A does not become high pressure relative to the second main pipeline 35B. That is, the first hydraulic pump motor 33 can be configured to rotate in the opposite direction without applying a torque load in one direction.

[0228] This describes a scenario where, from the direction of engine 9 (power source) towards output shaft 23 (axle), engine 9 rotates clockwise, applying a counterclockwise torque to the first connecting member 30, while the second connecting member 31 rotates counterclockwise (in the opposite direction). In this case, the counterclockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a counterclockwise (opposite direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the second main line 35B, the second hydraulic pump motor 34, and the first main line 35A, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the first hydraulic pump motor 33 is reduced relative to the discharge flow rate of the second hydraulic pump motor 34. Therefore, the second main pipeline 35B becomes high pressure relative to the first main pipeline 35A, enabling a torque load in the opposite direction to be applied to the first hydraulic pump motor 33. That is, the first hydraulic pump motor 33 can be configured to rotate in the opposite direction and be subjected to a torque load in the opposite direction.

[0229] Next, the case where the set pressure of the first variable relief valve 38A is high and the set pressure of the second variable relief valve 38B is low, that is, the first variable relief valve 38A is in the off state and the second variable relief valve 38B is in the connected state, will be explained.

[0230] First, let's explain the case where the engine 9 (power source) rotates clockwise towards the output shaft 23 (axle), applying a clockwise torque to the first connecting member 30, while the second connecting member 31 rotates clockwise (in one direction). In this case, the clockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a clockwise (in one direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the first main pipeline 35A, the second hydraulic pump motor 34, and the second main pipeline 35B, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the second hydraulic pump motor 34 is reduced relative to the discharge flow rate of the first hydraulic pump motor 33. Therefore, the first main pipeline 35A becomes high pressure relative to the second main pipeline 35B, enabling a torque load in one direction to be applied to the first hydraulic pump motor 33. That is, the first hydraulic pump motor 33 can be configured to rotate in one direction and be subjected to a torque load in that direction.

[0231] This describes a scenario where, from the direction of engine 9 (power source) towards output shaft 23 (axle), engine 9 rotates clockwise, applying a counterclockwise torque to the first connecting member 30, while the second connecting member 31 rotates clockwise (in one direction). In this case, the counterclockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a counterclockwise (opposite direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the first main pipeline 35A, the second hydraulic pump motor 34, and the second main pipeline 35B, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the first hydraulic pump motor 33 is reduced relative to the discharge flow rate of the second hydraulic pump motor 34. Therefore, the second main pipeline 35B becomes high pressure relative to the first main pipeline 35A, aiming to apply a torque load in the opposite direction to the first hydraulic pump motor 33. However, since the second variable relief valve 38B is in the open state, the working fluid flows sequentially through the second main pipeline 35B, connecting line 44, second bypass line 46, second variable relief valve 38B, and first check valve 47 towards the first main pipeline 35A. Therefore, the second main pipeline 35B does not become high pressure relative to the first main pipeline 35A. That is, the first hydraulic pump motor 33 can be configured to rotate in one direction but not be subjected to a torque load in the opposite direction.

[0232] This describes a scenario where, from the direction of the engine 9 (power source) toward the output shaft 23 (axle), the engine 9 rotates clockwise, applying a clockwise torque to the first connecting member 30, while the second connecting member 31 rotates counterclockwise (in the opposite direction). In this case, the clockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a clockwise (one direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the second main line 35B, the second hydraulic pump motor 34, and the first main line 35A, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the second hydraulic pump motor 34 is reduced relative to the discharge flow rate of the first hydraulic pump motor 33. Therefore, the first main pipeline 35A becomes high pressure relative to the second main pipeline 35B, enabling a torque load in one direction to be applied to the first hydraulic pump motor 33. That is, the first hydraulic pump motor 33 can be configured to rotate in the opposite direction while being subjected to a torque load in one direction.

[0233] This describes a scenario where, from the direction of engine 9 (power source) towards output shaft 23 (axle), engine 9 rotates clockwise, applying a counterclockwise torque to the first connecting member 30, while the second connecting member 31 rotates counterclockwise (in the opposite direction). In this case, the counterclockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a counterclockwise (opposite direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the second main line 35B, the second hydraulic pump motor 34, and the first main line 35A, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the first hydraulic pump motor 33 is reduced relative to the discharge flow rate of the second hydraulic pump motor 34. Therefore, the second main pipeline 35B becomes high pressure relative to the first main pipeline 35A, aiming to apply a torque load in the opposite direction to the first hydraulic pump motor 33. However, since the second variable relief valve 38B is in the open state, the working fluid flows sequentially through the second main pipeline 35B, connecting line 44, second bypass line 46, second variable relief valve 38B, and first check valve 47 towards the first main pipeline 35A. Therefore, the second main pipeline 35B does not become high pressure relative to the first main pipeline 35A. That is, the first hydraulic pump motor 33 can be configured to rotate in the opposite direction without applying a torque load in the opposite direction.

[0234] Next, we will explain the situation when the set pressures of both the first variable relief valve 38A and the second variable relief valve 38B are low, that is, when both the first variable relief valve 38A and the second variable relief valve 38B are in a connected state.

[0235] First, let's explain the case where the engine 9 (power source) rotates clockwise towards the output shaft 23 (axle), applying a clockwise torque to the first connecting member 30, while the second connecting member 31 rotates clockwise (in one direction). In this case, the clockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a clockwise (in one direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the first main pipeline 35A, the second hydraulic pump motor 34, and the second main pipeline 35B, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the second hydraulic pump motor 34 is reduced relative to the discharge flow rate of the first hydraulic pump motor 33. Therefore, the first main pipeline 35A becomes high pressure relative to the second main pipeline 35B, aiming to apply a torque load in one direction to the first hydraulic pump motor 33. However, since the first variable relief valve 38A is in the open state, the working fluid flows sequentially through the first main pipeline 35A, connecting line 44, first bypass line 45, first variable relief valve 38A, and second check valve 48 to the second main pipeline 35B. Therefore, the first main pipeline 35A does not become high pressure relative to the second main pipeline 35B. That is, the first hydraulic pump motor 33 can be set to a state where it rotates in one direction but is not subjected to a torque load in that direction.

[0236] This describes a scenario where, from the direction of engine 9 (power source) towards output shaft 23 (axle), engine 9 rotates clockwise, applying a counterclockwise torque to the first connecting member 30, while the second connecting member 31 rotates clockwise (in one direction). In this case, the counterclockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a counterclockwise (opposite direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the first main pipeline 35A, the second hydraulic pump motor 34, and the second main pipeline 35B, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the first hydraulic pump motor 33 is reduced relative to the discharge flow rate of the second hydraulic pump motor 34. Therefore, the second main pipeline 35B becomes high pressure relative to the first main pipeline 35A, aiming to apply a torque load in the opposite direction to the first hydraulic pump motor 33. However, since the second variable relief valve 38B is in the open state, the working fluid flows sequentially through the second main pipeline 35B, connecting line 44, second bypass line 46, second variable relief valve 38B, and first check valve 47 towards the first main pipeline 35A. Therefore, the second main pipeline 35B does not become high pressure relative to the first main pipeline 35A. That is, the first hydraulic pump motor 33 can be configured to rotate in one direction but not be subjected to a torque load in the opposite direction.

[0237] This describes a scenario where, from the direction of the engine 9 (power source) toward the output shaft 23 (axle), the engine 9 rotates clockwise, applying a clockwise torque to the first connecting member 30, while the second connecting member 31 rotates counterclockwise (in the opposite direction). In this case, the clockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a clockwise (one direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the second main line 35B, the second hydraulic pump motor 34, and the first main line 35A, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the second hydraulic pump motor 34 is reduced relative to the discharge flow rate of the first hydraulic pump motor 33. Therefore, the first main pipeline 35A becomes high pressure relative to the second main pipeline 35B, aiming to apply a torque load in one direction to the first hydraulic pump motor 33. However, since the first variable relief valve 38A is in the open state, the working fluid flows sequentially through the first main pipeline 35A, connecting line 44, first bypass line 45, first variable relief valve 38A, and second check valve 48 towards the second main pipeline 35B. Therefore, the first main pipeline 35A does not become high pressure relative to the second main pipeline 35B. That is, the first hydraulic pump motor 33 can be configured to rotate in the opposite direction without applying a torque load in one direction.

[0238] This describes a scenario where, from the direction of engine 9 (power source) towards output shaft 23 (axle), engine 9 rotates clockwise, applying a counterclockwise torque to the first connecting member 30, while the second connecting member 31 rotates counterclockwise (in the opposite direction). In this case, the counterclockwise torque acts on the second connecting member 31, and the first hydraulic pump motor 33 generates a counterclockwise (opposite direction) torque load. At this time, the working fluid wants to flow from the first hydraulic pump motor 33 sequentially through the second main line 35B, the second hydraulic pump motor 34, and the first main line 35A, and return to the first hydraulic pump motor 33. In this case, by adjusting the discharge volume per revolution of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the discharge flow rate of the first hydraulic pump motor 33 is reduced relative to the discharge flow rate of the second hydraulic pump motor 34. Therefore, the second main pipeline 35B becomes high pressure relative to the first main pipeline 35A, aiming to apply a torque load in the opposite direction to the first hydraulic pump motor 33. However, since the second variable relief valve 38B is in the open state, the working fluid flows sequentially through the second main pipeline 35B, connecting line 44, second bypass line 46, second variable relief valve 38B, and first check valve 47 towards the first main pipeline 35A. Therefore, the second main pipeline 35B does not become high pressure relative to the first main pipeline 35A. That is, the first hydraulic pump motor 33 can be configured to rotate in the opposite direction without applying a torque load in the opposite direction.

[0239] As described above, in the first embodiment, the transmission device 21 includes an input shaft 22 (input member), an output shaft 23 (output member), a planetary continuously variable transmission (CVT) 24, a direct connection mechanism 27, an idler gear element 28, and a multi-stage transmission mechanism 26. The input shaft 22 is rotated using a power source (engine 9) mounted on the vehicle (wheel loader 1). The output shaft 23 outputs rotation to the vehicle's running gear (front axle 12 and / or rear axle 13). The planetary CVT 24 is disposed between the input shaft 22 and the output shaft 23. The planetary CVT 24 changes the speed of rotation on the input shaft 22 side and transmits it to the output shaft 23 side. The direct connection mechanism 27 transmits the rotation on the input shaft 22 side to the output shaft 23 side, bypassing the planetary CVT 24. The idler gear element 28 mechanically connects the output side of the planetary CVT 24 and the output side of the direct connection mechanism 27. The multi-stage speed change mechanism 26 changes the rotation speed of the output side of the planetary continuously variable transmission mechanism 24 in stages by switching the transmission path of the meshing gears.

[0240] The direct-connection mechanism 27 includes a first clutch 27C (direct-connection clutch) disposed between the input shaft 22 and the idler element 28. The planetary continuously variable transmission 24 includes a planetary gear mechanism 29 (planetary mechanism), a first transmission component 33 (first hydraulic pump motor 33), and a second transmission component 34 (second hydraulic pump motor 34). The planetary gear mechanism 29 is, for example, as shown in... Figure 4 as well as Figure 5 As shown, the system comprises three components: a planetary carrier 29A (first component) connected to the input shaft 22, a first sun gear 29B (second component) serving as the output side, and a second sun gear 29C (third component) connected to the idler gear element 28 and serving as the output side other than the first sun gear 29B. In this configuration, the planetary carrier 29A (first component) is connected to the input shaft 22 via a first connecting member 30. The first sun gear 29B (second component) is connected to the first transmission unit 33 via a second connecting member 31 and a second clutch 36. The second sun gear 29C (third component) is connected to the idler gear element 28 (first idler gear 28B) via a third connecting member 32.

[0241] The first transmission component 33 is connected to the first sun gear 29B of the planetary gear mechanism 29. In this case, as... Figure 7As shown, the first transmission unit 33 is composed of a pump motor that performs pumping or motoring actions as a hydraulic rotary machine (oil pressure rotary machine). Furthermore, the first rotating shaft 42 of the first transmission unit 33 is connected to the first sun gear 29B of the planetary gear mechanism 29. The second transmission unit 34 can transmit power between itself and the first transmission unit 33. In this case, the second transmission unit 34 is composed of a pump motor that performs pumping or motoring actions as a hydraulic rotary machine (oil pressure rotary machine). Furthermore, the second transmission unit 34 can transmit power between itself and the first transmission unit 33 via a pair of main pipelines 35A and 35B for the flow of liquid (working oil). Additionally, the transmission device 21 includes a controller 25. The controller 25 controls the rotational speed of the first transmission unit 33 and the engagement and disengagement of the first clutch 27C.

[0242] The controller 25 can switch the transmission 21 to three transmission states: the first transmission state, the second transmission state, and the third transmission state. In the first transmission state, the first clutch 27C is disengaged, and the rotational speed of the first transmission component 33 is changed, thereby changing the rotational speed of the first sun gear 29B. This first transmission state involves two degrees of freedom of rotational motion between the planetary carrier 29A and the first sun gear 29B and the second sun gear 29C, transmitting power from the engine 9 to the planetary continuously variable transmission 24 to the multi-stage transmission 26 (CVT).

[0243] The second transmission state disengages the first clutch 27C and stops the rotation of the first transmission component 33, thereby stopping the rotation of the first sun gear 29B. This second transmission state involves one degree of rotational freedom between the planetary carrier 29A and the first sun gear 29B and the second sun gear 29C, transmitting power from the engine 9 to the planetary continuously variable transmission 24 to the multi-stage transmission 26 (internal lock-up). The third transmission state engages the first clutch 27C. This third transmission state transmits power from the engine 9 to the direct-connection mechanism 27, bypassing the planetary continuously variable transmission 24, to the multi-stage transmission 26 (external lock-up).

[0244] The controller 25 switches between the second transmission state (internal lock) and the third transmission state (external lock) based on the rotational speed of the output shaft 23. That is, the controller 25 is connected to a second speed detector 50 that detects the rotational speed (output rotational speed Vout) and direction of rotation of the output shaft 23. The rotational speed (output rotational speed Vout) of the output shaft 23 corresponds to the vehicle speed of the wheel loader 1. Figure 11 and Table 1 or Figure 12As shown in Table 2, the controller 25 can switch between the second transmission state (internal lock-up) and the third transmission state (external lock-up) based on the rotational speed of the output shaft 23 (output rotational speed Vout). Therefore, the switching between the second transmission state (internal lock-up) and the third transmission state (external lock-up) can be performed smoothly. Furthermore, since the switching between the second transmission state (internal lock-up) and the third transmission state (external lock-up) is possible, the number of speed stages (gear shifting stages) of the multi-stage transmission mechanism 26 can be reduced compared to structures that cannot perform this switching (e.g., structures with only internal lock-up). This allows the multi-stage transmission mechanism 26 to be compact and low-cost. In addition, since the power loss of the multi-stage transmission mechanism 26 can be reduced, the overall transmission efficiency of the transmission device 21 can be improved.

[0245] In the first embodiment, a first check valve 47 and a second variable relief valve 38B are connected in series between a pair of main pipelines 35A and 35B. The first check valve 47 is a check valve that allows pressurized oil to flow from the second main pipeline 35B (which is one main pipeline) to the first main pipeline 35A (which is another main pipeline) and prevents pressurized oil from flowing in the opposite direction. The second variable relief valve 38B is a connecting valve that switches the pair of main pipelines 35A and 35B between a connected state and a disconnected state. The controller 25 sets the state of the second variable relief valve 38B to the connected state by reducing the set pressure of the second variable relief valve 38B, that is, to a connected state that connects the pair of main pipelines 35A and 35B. Thus, by setting the second variable relief valve 38B to the connected state, the controller 25 can set the pair of main pipelines 35A and 35B to a state where they are connected in one direction and disconnected in the opposite direction by the first check valve 47.

[0246] That is, by setting the first variable relief valve 38A to the off state and the second variable relief valve 38B to the open state, the controller 25 can be configured to allow pressurized oil to flow from the second main pipeline 35B to the first main pipeline 35A and to prevent pressurized oil from flowing from the first main pipeline 35A to the second main pipeline 35B using the first check valve 47. Therefore, when switching the transmission state of the planetary continuously variable transmission mechanism 24, and / or when switching the speed levels of the multi-stage transmission mechanism 26, the controller 25 can be configured to allow pressurized oil to flow from the second main pipeline 35B to the first main pipeline 35A and to prevent pressurized oil from flowing from the first main pipeline 35A to the second main pipeline 35B.

[0247] Therefore, the transmission states of the planetary continuously variable transmission 24 and / or the speed levels of the multi-stage transmission 26 can be switched smoothly. Furthermore, depending on the setting of the rotation direction (forward direction) of the input shaft 22, the second variable relief valve 38B can be set to the off state and the first variable relief valve 38A to the open state, allowing pressurized oil to flow from the first main pipeline 35A (which is one main pipeline) to the second main pipeline 35B (which is another main pipeline), while the second check valve 48 prevents pressurized oil from flowing from the second main pipeline 35B to the first main pipeline 35A. Additionally, in Figure 17 In the case of the fifth variation shown, the first on / off valve 81A or the second on / off valve 81B can be set to the connected state (open position) instead of the first variable relief valve 38A or the second variable relief valve 38B being set to the connected state (reducing the set pressure).

[0248] In the first embodiment, by setting the second variable relief valve 38B to the connected state, the controller 25 can simultaneously achieve a state where power generated by the rotation of the first transmission component 33 in one direction of the planetary continuously variable transmission 24 is transmitted to the second transmission component 34, and a state where the transmission of power generated by the rotation of the first transmission component 33 in the opposite direction is cut off to the second transmission component 34. That is, by setting the first variable relief valve 38A to the cut-off state and the second variable relief valve 38B to the connected state, the controller 25 can set the operating state of the first transmission component 33 to a state where torque (load) acts in one direction and no torque (load) acts in the opposite direction. In other words, by setting the first variable relief valve 38A to the cut-off state and the second variable relief valve 38B to the connected state, the controller 25 can restrict the rotation of the first transmission component 33 in one direction, and can freely rotate in the opposite direction. Therefore, when the controller 25 switches the transmission state of the planetary continuously variable transmission 24 and / or switches the speed levels of the multi-stage transmission 26, by setting the second variable relief valve 38B to the connected state, the first transmission component 33 can be restricted to rotate in one direction, while being able to rotate freely in the opposite direction. This allows for smooth switching of the transmission state of the planetary continuously variable transmission 24 and / or switching of the speed levels of the multi-stage transmission 26.

[0249] In the first embodiment, the controller 25 switches from a first transmission state (continuously variable transmission) or a second transmission state (internal lock-up) to a third transmission state (external lock-up) by setting the second variable relief valve 38B to an engaged state and switching the first clutch 27C from a disengaged state to an engaged state. The first transmission state (continuously variable transmission) is a transmission state in which the rotation of the input shaft 22 is transmitted to the multi-stage transmission mechanism 26 via the planetary continuously variable transmission mechanism 24. The second transmission state (internal lock-up) is also a transmission state in which the rotation of the input shaft 22 is transmitted to the multi-stage transmission mechanism 26 via the planetary continuously variable transmission mechanism 24. The third transmission state (external lock-up) is a transmission state in which the rotation of the input shaft 22 is transmitted to the multi-stage transmission mechanism 26 bypassing the planetary continuously variable transmission mechanism 24. When the controller 25 switches the first clutch 27C from disengagement to engagement, it can smoothly switch from the first drive state (continuously variable transmission) or the second drive state (internal lock-up) to the third drive state (external lock-up) because the second variable relief valve 38B is set to the connected state.

[0250] In the first embodiment, the controller 25 sets the second variable relief valve 38B to the connected state and switches the first clutch 27C from the engaged state to the disengaged state, switching from the third transmission state (external lock-up) to the first transmission state (continuously variable transmission) or the second transmission state (internal lock-up). That is, when the controller 25 switches the first clutch 27C from engagement to disengagement, since the second variable relief valve 38B is set to the connected state, the switching from the third transmission state (external lock-up) to the first transmission state (continuously variable transmission) or the second transmission state (internal lock-up) can be performed smoothly.

[0251] In the first embodiment, the second variable relief valve 38B, which serves as a connecting valve, is an electromagnetic relief valve capable of changing the relief setting pressure. Furthermore, the controller 25 sets the second variable relief valve 38B to a cut-off state by increasing the relief setting pressure and sets it to a connected state by decreasing the relief setting pressure. Therefore, the controller 25 can set the second variable relief valve 38B to a connected state when switching the transmission state of the planetary continuously variable transmission mechanism 24, and / or when switching the speed levels of the multi-stage transmission mechanism 26.

[0252] In the first embodiment, the multi-stage transmission mechanism 26 is provided with multiple transmission paths having different reduction ratios. For example, the multi-stage transmission mechanism 26 includes: a low-gear shaft unit 61 that serves as the first output transmission path (forward 1st gear transmission path); and a high-gear shaft unit 62 that serves as the second output transmission path (forward 2nd gear transmission path) and the third output transmission path (forward 3rd gear transmission path). Furthermore, the rotational speed ratio of each transmission path that transmits the rotation of the idler gear element 28 to the output shaft 23 is different. For example, the rotational speed ratios of the first output transmission path (forward 1st gear) of the low-gear shaft unit 61, the second output transmission path (forward 2nd gear), and the third output transmission path (forward 3rd gear) of the high-gear shaft unit 62 are different.

[0253] Based on this, when switching from the second transmission state (internal lock-up) to the third transmission state (external lock-up) and switching the transmission path of the multi-stage transmission mechanism 26, the controller 25 sets the second variable relief valve 38B to the connected state. As a result, the first transmission component 33 is restricted from rotating in one direction, but can freely rotate in the opposite direction. That is, the controller 25 sets the first variable relief valve 38A to the disconnected state, sets the second variable relief valve 38B to the connected state, and switches the first clutch 27C from the disengaged state to the engaged state, thereby switching from the second transmission state (internal lock-up) to the third transmission state (external lock-up) and switching the transmission path of the multi-stage transmission mechanism 26. Therefore, these switching operations can be performed smoothly when switching from the second transmission state (internal lock-up) to the third transmission state (external lock-up) and switching the transmission path of the multi-stage transmission mechanism 26.

[0254] In the first embodiment, when switching from the third transmission state (external lock-up) to the second transmission state (internal lock-up) and switching the transmission path of the multi-stage transmission mechanism 26, the controller 25 sets the second variable relief valve 38B to the connected state. As a result, the first transmission component 33 is restricted from rotating in one direction, but can freely rotate in the opposite direction. That is, the controller 25 sets the first variable relief valve 38A to the disconnected state, sets the second variable relief valve 38B to the connected state, and switches the first clutch 27C from the engaged state to the disengaged state, thereby switching from the third transmission state (external lock-up) to the second transmission state (internal lock-up) and switching the transmission path of the multi-stage transmission mechanism 26. Therefore, these switching operations can be performed smoothly when switching from the third transmission state (external lock-up) to the second transmission state (internal lock-up) and switching the transmission path of the multi-stage transmission mechanism 26.

[0255] In the first embodiment, when switching from the first transmission state (continuously variable transmission) to the third transmission state (external lock-up) and switching the transmission path of the multi-stage transmission mechanism 26, the controller 25 sets the second variable relief valve 38B to the connected state. This restricts the first transmission component 33 from rotating in one direction, while allowing free rotation in the opposite direction. Specifically, the controller 25 sets the first variable relief valve 38A to the disconnected state, sets the second variable relief valve 38B to the connected state, and switches the first clutch 27C from the disengaged state to the engaged state, thereby switching from the first transmission state (continuously variable transmission) to the third transmission state (external lock-up) and switching the transmission path of the multi-stage transmission mechanism 26. Therefore, these switching operations can be performed smoothly when switching from the first transmission state (continuously variable transmission) to the third transmission state (external lock-up) and switching the transmission path of the multi-stage transmission mechanism 26.

[0256] In the first embodiment, when switching from the third transmission state (external lock-up) to the first transmission state (continuously variable transmission) and switching the transmission path of the multi-stage transmission mechanism 26, the controller 25 sets the second variable relief valve 38B to the connected state. As a result, the first transmission component 33 is restricted from rotating in one direction, but can freely rotate in the opposite direction. That is, the controller 25 sets the first variable relief valve 38A to the disconnected state, sets the second variable relief valve 38B to the connected state, and switches the first clutch 27C from the engaged state to the disengaged state, thereby switching from the third transmission state (external lock-up) to the first transmission state (continuously variable transmission) and switching the transmission path of the multi-stage transmission mechanism 26. Therefore, these switching operations can be performed smoothly when switching from the third transmission state (external lock-up) to the first transmission state (continuously variable transmission) and switching the transmission path of the multi-stage transmission mechanism 26.

[0257] In the first embodiment, the transmission device 21 provides a multi-stage transmission mechanism 26 between the third member of the planetary gear mechanism 29 (i.e., the member connected to the idler gear element 28 via the third connecting member 32, for example, the second sun gear 29C) and the output shaft 23 (output member). The multi-stage transmission mechanism 26 includes a forward 1st gear transmission path (low gear shaft unit 61) that serves as the first output transmission path, a forward 2nd gear transmission path (high gear shaft unit 62) that serves as the second output transmission path, and a forward 3rd gear transmission path (high gear shaft unit 62) that serves as the third output transmission path. The first to third output transmission paths are forward rotation paths in which the number of gear meshes between the idler gear element 28 and the output shaft 23 is the same (e.g., an odd number of times). Furthermore, the multi-stage transmission mechanism 26 has a reverse gear transmission path (low gear shaft unit 61) where the number of gear engagements between the idler gear element 28 and the output shaft 23 is different from the forward path (e.g., 0 times or an even number of times). When the rear first gear 67 is engaged with the low gear shaft 65 using the rear first gear clutch 70, the first idler gear 28B, the countershaft gear 64, the rear first gear 67, the low gear shaft 65, the low gear 68, the low gear output gear 78, and the output shaft 77 (output shaft 23) rotate as a whole. When the rear first gear clutch 70 is engaged, the number of gear engagements is an even number when power is transmitted to the idler gear element 28 via the planetary continuously variable transmission mechanism 24 or the direct connection mechanism 27 to the output shaft 77 (output shaft 23).

[0258] In contrast, when the first gear forward gear 66 is engaged with the low gear shaft 65 using the first gear forward clutch 69, the second idler gear 28C, the first gear forward gear 66, the low gear shaft 65, the low gear 68, the low gear output gear 78, and the output shaft 77 (output shaft 23) rotate as a whole. When the first gear forward clutch 69 is engaged, the number of gear engagements is odd when power is transmitted to the idler element 28 via the planetary continuously variable transmission mechanism 24 or the direct coupling mechanism 27 to the output shaft 77 (output shaft 23). Furthermore, when the second gear forward gear 72 is engaged with the high gear shaft 71 using the second gear forward clutch 75, the second idler gear 28C, the second gear forward gear 72, the high gear shaft 71, the high gear 74, the high gear output gear 79, and the output shaft 77 (output shaft 23) rotate as a whole. When the forward 2nd gear clutch 75 is engaged, the number of gear engagements is odd when power is transmitted to the output shaft 77 (output shaft 23) from the planetary continuously variable transmission mechanism 24 or the direct connection mechanism 27 to the idler gear element 28.

[0259] Furthermore, when the forward 3rd gear clutch 76 engages the forward 3rd gear 73 with the high gear shaft 71, the first idler gear 28B, the forward 3rd gear 73, the high gear shaft 71, the high gear 74, the high gear output gear 79, and the output shaft 77 (output shaft 23) rotate as a whole. When the forward 3rd gear clutch 76 is engaged, the number of gear engagements is odd when power is transmitted to the idler element 28 via the planetary continuously variable transmission mechanism 24 or the direct connection mechanism 27 to the output shaft 77 (output shaft 23). That is, the multi-stage transmission mechanism 26 can reverse the direction of travel of the wheel loader 1 (vehicle) by switching between the reverse mode (reverse mode) that engages the backward 1st gear clutch 70 and the forward mode (forward mode) that engages the forward 1st gear clutch 69, the forward 2nd gear clutch 75, or the forward 3rd gear clutch 76. Therefore, the transmission device 21 can reverse the rotation direction of the load (output shaft 23).

[0260] In addition, Figure 13 In the first modification shown, a braking mechanism 55 (brake) is provided on the second connecting member 31 connected to the first transmission member 33. Thus, in the first modification, the braking mechanism 55 (brake) is connected to the second member of the planetary gear mechanism 29 (i.e., the member connected to the first transmission member 33 via the second connecting member 31, for example, the first sun gear 29B). The controller 25 maintains the second transmission state (internal locking) by engaging the braking mechanism 55 (brake). Therefore, even without using the first transmission member 33 to maintain the rotational speed of the second connecting member 31 (and thus the second member of the planetary gear mechanism 29) at 0, the braking mechanism 55 can maintain the rotational speed of the second connecting member 31 (and thus the second member of the planetary gear mechanism 29) at 0. Thus, for example, if the first transmission member 33 is an electric motor, the rotational speed can be maintained at 0 even without continuously supplying power to the first transmission member 33. As a result, losses can be reduced during the second transmission state (internal lock-up).

[0261] then, Figures 36 to 39 This indicates the second embodiment. The second embodiment is characterized by using a planet carrier, a sun gear, and a ring gear to construct a planetary gear mechanism. Furthermore, in the second embodiment, the same reference numerals are used for the same components as in the first embodiment, and their descriptions are omitted.

[0262] In the first embodiment, the case of a planetary gear mechanism 29 comprising a planetary carrier and two sun gears constituting a planetary continuously variable transmission (CVT) 24 was described as an example. In contrast, in the second embodiment, a planetary gear mechanism 91 comprising a planetary carrier 91A, a sun gear 91B, and a ring gear 91C constitutes the planetary CVT 24. Table 5 below shows the combinations of the constituent elements (planetary carrier, sun gear, and ring gear) of the planetary gear mechanism 91. Power transmission can be performed in either case. From the perspective of improving the transmission efficiency of the planetary CVT 24, reducing the maximum absorbed torque of the first transmission component 33, and enabling a compact and lightweight overall configuration of the planetary CVT 24, "No. 2-A" in Table 5 is optimal.

[0263] [Table 5]

[0264] like Figure 36 as well as Figure 37 As shown, in the second embodiment (i.e., No. 2–A in Table 5), the planetary gear mechanism 91 includes a planet carrier 91A corresponding to the first member, a sun gear 91B corresponding to the second member, a ring gear 91C corresponding to the third member, and planet gears 91D. Furthermore, the power transmission of the sun gear 91B, ring gear 91C, and planet gears 91D may not be achieved through gear meshing; for example, it may be achieved through friction of rollers (outer peripheral surfaces).

[0265] Engine 9 (input shaft 22) is connected to planet carrier 91A via first connecting member 30. Sun gear 91B is connected to first transmission component 33 via second connecting member 31. Ring gear 91C is connected to idler element 28 (first idler gear 28B) via third connecting member 32. Sun gear 91B meshes with planet gear 91D. Additionally, planet gear 91D meshes with ring gear 91C. The rotation axis S of planet gear 91D... p ( Figure 38 The planetary gear 91D is supported on the planet carrier 91A. Therefore, the planetary gear 91D is positioned with respect to the central axis S of the planetary gear mechanism 91. Figure 38 It revolves around the center and rotates on its own axis.

[0266] Next, the operation of the planetary gear mechanism 91, consisting of planet carrier 91A, sun gear 91B, and ring gear 91C, will be explained. The following applies under all the conditions specified in Table 5: “No.2–A”, “No.2–B”, “No.2–C”, “No.2–D”, “No.2–E”, and “No.2–F”.

[0267] First, the torque distribution of the three components (planet carrier 91A, sun gear 91B, and ring gear 91C) of the planetary gear mechanism 91 will be explained. Figure 38This is a cross-sectional view of the planetary gear mechanism 91 viewed from the power source side. The planet carrier 91A, sun gear 91B, and ring gear 91C are concentrically arranged. That is, the central axis S (rotational axis) of the planet carrier 91A, sun gear 91B, and ring gear 91C coincides. The planet gear 91D is configured to contact the outer circumference of the sun gear 91B and the inner circumference of the ring gear 91C. The planet gear 91D meshes with the sun gear 91B and the ring gear 91C. The planet carrier 91A, sun gear 91B, and ring gear 91C are supported by the housing of the planetary continuously variable transmission 24 in a manner that allows them to rotate about the central axis S and cannot move in other directions, thus enabling the meshing of their respective gears. The planet gear 91D rotates about the central axis S, which serves as the central axis of the planet gear 91D. p The planetary gear 91D is supported by the planet carrier 91A in a manner that allows it to rotate around its own axis and cannot move in other directions. The planetary gear 91D revolves around the central axis S of the planet carrier 91A while simultaneously revolving around its own central axis S. p It rotates around the center.

[0268] like Figure 38 As shown, the constraint of the planetary gear mechanism 91 is that the sun gear 91B needs to mesh with the ring gear 91C and the planet gear 91D. Furthermore, to ensure gear strength, the diameter of the planet gear 91D needs to be increased. That is, the constraint of the planetary gear mechanism 91 is that the meshing radius r of the sun gear 91B... s The meshing radius r of gear ring 91C r Much smaller. The structure of “No.2–A” in Table 5 is that the planetary carrier 91A is connected to the first structural member 30, which is connected to the engine 9 (power source). Therefore, the torque T of the planetary carrier 91A... c This is the torque that engine 9 can produce. The sun gear 91B is connected to the second connecting member 31, which is connected to the first transmission component 33. Therefore, the torque T of the sun gear 91B... s This is the torque that the first transmission component 33 can generate. The gear ring 91C is connected to the third connecting structure 32, which is connected to the idler gear element 28. Therefore, the torque T of the gear ring 91C... r It is the torque reaction force received from the first idler gear 28B.

[0269] During the power transmission period of the planetary continuously variable transmission 24, the torque T of the sun gear 91B is... s Torque T of gear ring 91C r And the torque T of the planetary carrier 91A cThe ratio remains constant. Based on this rule, the controller 25 outputs a signal to control the first transmission component 33, controlling the torque of the second connecting component 31 (e.g., sun gear 91B) connected to the first transmission component 33. That is, the controller 25 controls the torque of the second connecting component 31 (e.g., sun gear 91B) by controlling the first transmission component 33. Thus, the controller 25 indirectly controls the torque of the first connecting component 30 (e.g., planet carrier 91A) connected to the engine 9 and the torque of the third connecting component 32 (e.g., ring gear 91C) connected to the idler gear element 28. As a result, the torque transmission can be controlled between the first connecting component 30 (e.g., planet carrier 91A) connected to the engine 9 and the third connecting component 32 (e.g., ring gear 91C) connected to the idler gear element 28.

[0270] Figure 39 This describes the relationship between the rotational speeds of the planetary gear mechanism 91. Assume the rotational speed of the planet carrier 91A is constant. In this case, when the rotational speed of the ring gear 91C is increased, the rotational speed of the sun gear 91B decreases. Conversely, when the rotational speed of the ring gear 91C is decreased, the rotational speed of the sun gear 91B increases. Based on this rule, the controller 25 outputs a signal to control the first transmission component 33, controlling the rotational speed of the second connecting component 31 (e.g., the sun gear 91B) connected to the first transmission component 33. That is, the controller 25 controls the rotational speed of the second connecting component 31 (e.g., the sun gear 91B) by controlling the first transmission component 33. Thus, the controller 25 indirectly controls the rotational speed of the first connecting component 30 (e.g., the planet carrier 91A) connected to the engine 9, and the rotational speed of the third connecting component 32 (e.g., the ring gear 91C) connected to the idler gear element 28. As a result, the gear ratio can be controlled between the first structural member 30 (e.g., planetary carrier 91A) connected to the engine 9 and the third structural member 32 (e.g., gear ring 91C) connected to the idler gear element 28.

[0271] Alternatively, it can be like Figure 40 As shown in the sixth variation (No. 2–B of Table 5), the planetary gear mechanism 91 connects the ring gear 91C to the component connected to the engine 9, i.e., the first connecting structural member 30; connects the planet carrier 91A to the component connected to the first transmission component 33, i.e., the second connecting structural member 31; and connects the sun gear 91B to the component connected to the idler gear element 28, i.e., the third connecting structural member 32. Alternatively, it can be as follows... Figure 41As shown in the seventh variation (No. 2–C of Table 5), the planetary gear mechanism 91 connects the planet carrier 91A to the first connecting member 30, the ring gear 91C to the second connecting member 31, and the sun gear 91B to the third connecting member 32. Furthermore, although the illustration is omitted, the planetary gear mechanism 91 can also connect the planet carrier 91A, the sun gear 91B, and the ring gear 91C to the first connecting member 30, the second connecting member 31, and the third connecting member 32, as shown in “No. 2–D,” “No. 2–E,” or “No. 2–F” of Table 5.

[0272] The second embodiment includes a planetary gear mechanism 91 as described above, and its basic function is not significantly different from that of the first embodiment described above. That is, the second embodiment, like the first embodiment, switches between the second transmission state (internal lock) and the third transmission state (external lock) according to the rotational speed of the output shaft 23. Therefore, the switching between the second transmission state (internal lock) and the third transmission state (external lock) can be performed smoothly.

[0273] In addition, in the first embodiment, the second transmission component 34 is connected to an idler element 28 (specifically, an idler shaft 28A that becomes a rotating element) disposed between the planetary gear mechanism 29 and the multi-stage transmission mechanism 26. In contrast, although the figures are omitted, the second transmission component 34 may also be configured to be connected to a rotating element disposed between the input shaft 22 (input member) and the power source (engine 9), a rotating element constituting the multi-stage transmission mechanism 26, a rotating element disposed between the multi-stage transmission mechanism 26 and the output shaft 23 (output member), or a rotating element disposed between the output shaft 23 (output member) or the output shaft 23 and the travel device (front axle 12 and rear axle 13).

[0274] That is, in the first embodiment, the second transmission component 34 is configured to be connected to a position closer to the output shaft 23 (output member) than the planetary gear mechanism 29; in other words, the second transmission component 34 is configured to be connected between the planetary gear mechanism 29 and the output shaft 23. Alternatively, the second transmission component 34 may be connected to the input gear 27A of the direct connection mechanism 27 provided on the input shaft 22 (input member). That is, the second transmission component 34 may also be connected between the planetary gear mechanism 29 and the input shaft 22 (input member). Thus, the second transmission component 34 may also be configured to be connected to a position closer to the engine 9 (power source) than the planetary gear mechanism 29. Furthermore, the second transmission component 34 may be connected to the locking gear 27B of the direct connection mechanism 27. For example, the second transmission component 34 may be connected to the third connecting member 32. For example, the second transmission component 34 may be connected to the first idler gear 28B of the idler element 28. The second transmission component 34 can also be connected to the second idler gear 28C of the idler element 28.

[0275] For example, the second transmission component 34 can also be connected to the high gear 74 of the multi-stage transmission mechanism 26. For example, the second transmission component 34 can also be connected to the low gear 68 of the multi-stage transmission mechanism 26. For example, the second transmission component 34 can also be connected to the high output gear 79 of the multi-stage transmission mechanism 26. For example, the second transmission component 34 can also be connected to the low output gear 78 of the multi-stage transmission mechanism 26. For example, the second transmission component 34 can also be connected to the output shaft 77 of the multi-stage transmission mechanism 26 (output shaft 23 of the transmission device 21). For example, the second transmission component 34 can also be connected to a position closer to the load side (front axle 12 side and rear axle 13 side) than the output shaft 23 of the transmission device 21. For example, the second transmission component 34 can also be connected to the front axle 12, rear axle 13, front drive shaft 14, or rear drive shaft 15. These are also the same for the second embodiment and its variations.

[0276] In the first embodiment, the planetary mechanism constituting the planetary continuously variable transmission 24 is described using a planetary gear mechanism 29 as an example. That is, in the first embodiment, the case where the planetary component of the planetary mechanism is constituted by a planetary gear is described as an example. However, it is not limited to this, and the planetary component of the planetary mechanism may also be constituted by a component other than a gear, such as a planetary roller. This is also the case for the second embodiment and its variations.

[0277] In the first embodiment, a transmission device 21 having a multi-stage transmission mechanism 26 and a direct connection mechanism 27 was described as an example. However, it is not limited to this, and the transmission device 21 may omit the multi-stage transmission mechanism 26 and / or the direct connection mechanism 27 as needed. This is also the case for the second embodiment and its variations.

[0278] In the first embodiment, the case of mounting the transmission device 21 on a wheel loader 1 was described as an example. However, it is not limited to this; the transmission device 21 can also be mounted on other work vehicles (construction machinery) such as hydraulic excavators, hydraulic cranes, dump trucks, and forklifts. Furthermore, it is not limited to work vehicles, but can be widely used as a transmission device installed in various vehicles such as automobiles and railway vehicles, or in various industrial and general machinery. The same applies to the second embodiment and its variations.

[0279] Furthermore, the above-described embodiments and variations are examples, and of course, partial substitutions or combinations of the structures shown in different embodiments and variations can be adopted. Explanation of reference numerals in the attached figures

[0280] 1. Wheel loader (vehicle); 9. Engine (power source); 12. Front axle (travel device); 13. Rear axle (travel device); 21. Transmission; 22. Input shaft (input component); 23, 23A, 23B, 77. Output shaft (output component); 24. Planetary continuously variable transmission (CVT); 25. Controller; 26. Multi-stage transmission (secondary transmission); 27. Direct connection mechanism (external locking mechanism); 27C. First clutch (direct connection clutch); 28. Idler gear element; 29. ​​Planetary gear mechanism (planetary mechanism); 29A. Planet carrier (first, second, or third component); 29B. First sun gear (first, second, or third component); 29C. Second sun gear (first, second, or third component); 33. First oil... 34. Hydraulic pump motor (first transmission component); 35A. First main pipeline (main pipeline); 35B. Second main pipeline (main pipeline); 36. Second clutch; 37. Third clutch; 38B. Second variable relief valve (connecting valve); 47. First check valve (check valve); 61. Low gear shaft unit (first output transmission path, transmission path); 62. High gear shaft unit (second output transmission path, third output transmission path, transmission path); 81B. Second on / off valve (connecting valve); 91. Planetary gear mechanism (planetary mechanism); 91A. Planetary carrier (first component, second component, or third component); 91B. Sun gear (first component, second component, or third component); 91C. Ring gear (first component, second component, or third component).

Claims

1. A speed-changing device, the speed-changing device comprising: The input shaft rotates using a power source mounted on the vehicle; An output shaft that outputs rotation to the vehicle's driving mechanism; A planetary continuously variable transmission mechanism is disposed between the input shaft and the output shaft to change the rotational speed on the input shaft side and transmit it to the output shaft side; A direct connection mechanism that allows rotation on the input shaft side to be transmitted to the output shaft side bypassing the planetary continuously variable transmission mechanism; An idler gear element that mechanically connects the output side of the planetary continuously variable transmission and the output side of the direct-drive mechanism; and The multi-stage speed change mechanism, by switching the transmission path of the meshing gears, enables the rotation of the output side of the planetary continuously variable transmission mechanism to change speed in stages. The direct connection mechanism includes a direct connection clutch disposed between the input shaft and the idler gear element. The planetary continuously variable transmission mechanism has the following features: A planetary mechanism having three components: a first component connected to the input shaft side, a second component serving as the output side, and a third component connected to the idler wheel element and serving as the output side other than the second component; The first transmission component comprises a hydraulic rotary mechanism that performs pump or motor actuation, and its rotary shaft is connected to the second component of the planetary mechanism; and The second transmission unit, which consists of a hydraulic rotary mechanism that performs pump or motor operation, can transmit power between itself and the first transmission unit via a pair of main pipelines for fluid flow. The speed change device is characterized in that... The transmission device includes a controller that controls the rotational speed of the first transmission component and the engagement and disengagement of the direct-drive clutch. The controller can switch between three transmission states: the first transmission state, the second transmission state, and the third transmission state. In the first transmission state, the direct-connection clutch is disengaged, changing the rotational speed of the first transmission component, thereby changing the rotational speed of the second component. Two degrees of freedom of rotational motion occur between the first component and the second and third components, transmitting the power from the power source to the planetary continuously variable transmission mechanism to the multi-stage transmission mechanism. In the second transmission state, the direct-connection clutch is disengaged, stopping the rotation of the first transmission component, thereby stopping the rotation of the second component. A one-degree-of-freedom rotational motion is then performed between the first component, the second component, and the third component, transmitting the power from the power source to the planetary continuously variable transmission mechanism to the multi-stage transmission mechanism. In the third transmission state, the direct-drive clutch is engaged, thereby bypassing the planetary continuously variable transmission mechanism to transmit power from the power source to the direct-drive mechanism to the multi-stage transmission mechanism. The controller switches between the second transmission state and the third transmission state according to the rotational speed of the output shaft.

2. The speed change device according to claim 1, characterized in that, A check valve and a connecting valve are connected in series between the pair of main pipelines. The check valve allows pressurized oil to flow from one main pipeline to the other and prevents pressurized oil from flowing in the opposite direction. The connecting valve switches the pair of main pipelines between a connected state and a disconnected state. The controller sets the connecting valve to the connected state, thereby setting the pair of main pipelines to a state where they are connected in one direction and cut off by the check valve in the opposite direction.

3. The speed change device according to claim 2, characterized in that, The controller sets the connecting valve to the connected state, thereby simultaneously transmitting power to the second transmission component generated by the rotation of the first transmission component in one direction, and cutting off the transmission of power to the second transmission component generated by the rotation of the first transmission component in the opposite direction. This restricts the rotation of the first transmission component in one direction, while allowing the first transmission component to rotate freely in the opposite direction.

4. The speed change device according to claim 2, characterized in that, The controller switches the direct-connection clutch from a disengaged state to an engaged state by setting the connecting valve to an engaged state, thus switching the transmission of the input shaft's rotation to the multi-stage transmission mechanism from the first or second transmission state via the planetary continuously variable transmission mechanism to the third transmission state that bypasses the planetary continuously variable transmission mechanism.

5. The speed change device according to claim 2, characterized in that, The controller switches from the third transmission state of transmitting the rotation of the input shaft to the multi-stage transmission mechanism via the planetary continuously variable transmission mechanism to the first or second transmission state of transmitting the rotation of the input shaft to the multi-stage transmission mechanism via the planetary continuously variable transmission mechanism by setting the connecting valve to the connected state and switching the direct-connection clutch from the engaged state to the disengaged state.

6. The speed change device according to claim 2, characterized in that, The connecting valve is an electromagnetic relief valve capable of changing the relief set pressure. The controller sets the connecting valve to the shut-off state by increasing the overflow set pressure. The controller sets the connecting valve to the connected state by reducing the overflow set pressure.

7. The speed change device according to claim 2, characterized in that, The multi-stage speed change mechanism has multiple transmission paths with different reduction ratios. When the controller switches from the second transmission state to the third transmission state and switches the transmission path of the multi-stage transmission mechanism, it sets the connecting valve to the connected state, thereby restricting the rotation of the first transmission component in one direction and allowing the first transmission component to rotate freely in the opposite direction.

8. The speed change device according to claim 2, characterized in that, The multi-stage speed change mechanism has multiple transmission paths with different reduction ratios. When the controller switches from the third transmission state to the second transmission state and switches the transmission path of the multi-stage transmission mechanism, it sets the connecting valve to the connected state, thereby restricting the rotation of the first transmission component in one direction and allowing the first transmission component to rotate freely in the opposite direction.

9. The speed change device according to claim 7, characterized in that, The controller sets the connecting valve to the connected state and switches the direct-connection clutch from the disengaged state to the engaged state, thereby switching from the second transmission state to the third transmission state and switching the transmission path of the multi-stage transmission mechanism.

10. The speed change device according to claim 8, characterized in that, The controller sets the connecting valve to the connected state and switches the direct-connection clutch from the engaged state to the disengaged state, thereby switching from the third transmission state to the second transmission state and switching the transmission path of the multi-stage transmission mechanism.

11. The speed change device according to claim 2, characterized in that, The multi-stage speed change mechanism has multiple transmission paths with different reduction ratios. When the controller switches from the first transmission state to the third transmission state and switches the transmission path of the multi-stage transmission mechanism, it sets the connecting valve to the connected state, thereby restricting the rotation of the first transmission component in one direction and allowing the first transmission component to rotate freely in the opposite direction.

12. The speed change device according to claim 2, characterized in that, The multi-stage speed change mechanism has multiple transmission paths with different reduction ratios. When the controller switches from the third transmission state to the first transmission state and switches the transmission path of the multi-stage transmission mechanism, it sets the connecting valve to the connected state, thereby restricting the rotation of the first transmission component in one direction and allowing the first transmission component to rotate freely in the opposite direction.

13. The speed change device according to claim 11, characterized in that, The controller sets the connecting valve to the connected state and switches the direct connection clutch from the disengaged state to the engaged state, thereby switching from the first transmission state to the third transmission state and switching the transmission path of the multi-stage transmission mechanism.

14. The speed change device according to claim 12, characterized in that, The controller sets the connecting valve to the connected state and switches the direct connection clutch from the self-engaged state to the disengaged state, thereby switching from the third transmission state to the first transmission state and switching the transmission path of the multi-stage speed change mechanism.

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