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 multi-stage transmission mechanism (26); and a controller (25). The multi-stage transmission mechanism (26) has a forward rotation mode in which the forward one-speed clutch (69) is connected, and a reverse rotation mode in which the reverse one-speed clutch (70) is connected. When switching from the forward rotation mode to the reverse rotation mode, the controller (25) starts switching of the forward first-speed clutch (69) from the engaged state to the released state and starts switching of the reverse first-speed clutch (70) from the released state to the engaged state in a state in which the rotation of the output shaft (23) is forward (forward state).

Description

Technical Field

[0001] This invention 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 transmits power using a planetary continuously variable transmission (CVT) mechanism composed of a planetary gear mechanism and an electric motor. It is believed that the engineering machine according to Patent Document 1, by using a planetary CVT mechanism, can reduce abrupt changes in engine rotation speed and suppress abrupt changes in the operating speed of the cargo 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] The technology described in Patent Document 1 has the potential to make it impossible to smoothly switch between forward and reverse rotation of the output shaft (ultimately, the switching between forward and reverse movement of the vehicle).

[0005] One of the objectives of this invention is to provide a transmission device that can smoothly switch between forward and reverse rotation of the output shaft (ultimately, the switching between forward and backward movement of the vehicle).

[0006] Preferably, the transmission device of the present invention comprises: an input shaft that rotates via 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 the rotational speed change on the input shaft side to the output shaft side; and a multi-stage transmission mechanism that, by switching the transmission path of gear meshing, progressively changes the rotational speed on the output side of the planetary CVT mechanism, wherein the planetary CVT mechanism comprises: a planetary mechanism having three components: a first component connected to the input shaft side, a second component becoming the output side, and a third component becoming an output side different from the second component; a first gearbox connected to the second component of the planetary mechanism; and a second gearbox capable of transmitting power between the first gearbox and the second gearbox; and the multi-stage transmission mechanism comprising: a first output clutch disposed between the input shaft and the output shaft; and a second gearbox connected to the input shaft side; the input shaft rotating via a power source mounted on a power source mounted on a vehicle; the output shaft rotating via a power source mounted on a power source mounted on a vehicle; the output shaft rotating via a power source mounted on the input shaft side ... The transmission device includes a first output transmission path where the gear between the output side of the planetary continuously variable transmission mechanism and the output shaft engages an odd number of times, switching the power transmission and release of the first output transmission path; and a second output clutch, which is located on a second output transmission path where the gear between the output side of the planetary continuously variable transmission mechanism and the output shaft engages zero or an even number of times, switching the power transmission and release of the second output transmission path. The transmission device has a controller for controlling the engagement and disengagement of the first output clutch and the second output clutch. The controller can reverse the vehicle's direction of travel by switching between a forward rotation mode and a reverse rotation mode. In the forward rotation mode, the first output clutch is engaged and the second output clutch is disengaged; in the reverse rotation mode, the first output clutch is disengaged and the second output clutch is engaged. Furthermore, when switching from the forward rotation mode to the reverse rotation mode, the controller, while the output shaft is rotating forward, initiates the switching of the first output clutch from the engaged state to the released state, and initiates the switching of the second output clutch from the released state to the engaged state. The rotational direction of the third component is reversed by changing the rotational speed of the first transmission. Alternatively, when switching from the reverse rotation mode to the forward rotation mode, the controller, while the output shaft is rotating in reverse, initiates the switching of the second output clutch from the engaged state to the released state, and initiates the switching of the first output clutch from the released state to the engaged state. The rotational direction of the third component is reversed by changing the rotational speed of the first transmission.

[0007] According to the present invention, the forward and reverse rotation of the output shaft can be smoothly switched (ultimately, the forward and backward switching of the vehicle). Attached Figure Description

[0008] Figure 1This is a left-side view of a wheel loader equipped with a transmission device based on the implementation method. Figure 2 It means Figure 1 A partial sectional side view of the transmission device. Figure 3 This is a configuration diagram showing the transmission device based on the first embodiment. Figure 4 It is Figure 3 The diagram shows the internal structure of the transmission mechanism and the planetary mechanism. Figure 5 yes Figure 4 Enlarged view of part (A) in the image. Figure 6 yes Figure 4 Enlarged view of part (B) in the image. Figure 7 It indicates that it is composed of hydraulic equipment. Figure 3 A diagram illustrating an example of the configuration of a planetary continuously variable transmission (CVT) including the first gearbox, the second gearbox, 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 represents the ideal relationship between the speed and traction of a wheel loader. Figure 11 This is an example of a drive force diagram showing the relationship between the speed and traction of a wheel loader (the drive force diagrams in Table 1 described later). Figure 12 These are other examples of drive force diagrams showing the relationship between the speed and traction of a wheel loader (the drive force diagrams constructed in Table 2 described later). Figure 13 This refers to the first modified example (the configuration that achieves internal locking through braking) and... Figure 3 The same composition diagram. Figure 14 This refers to the second variation (the configuration where the input shaft is connected to the first solar component and the first gearbox is connected to the gear carrier) and... Figure 4 The same composition diagram. Figure 15 This refers to the third variation (a configuration where the input shaft is connected to the first solar component and the first gearbox is connected to the second solar component) and... Figure 4 The same composition diagram. Figure 16This refers to the fourth variation (the configuration where the second transmission is connected to the output shaft) and... Figure 4 The same composition diagram. Figure 17 This indicates the fifth variation (composed of hydraulic equipment). Figure 3 Other examples of planetary continuously variable transmissions (CVTs) including the first gearbox, second gearbox, power absorption device, etc. Figure 7 The same composition diagram. Figure 18 This is a characteristic curve diagram that represents an example of the time changes of various state quantities when switching from forward mode (forward mode) to reverse mode (backward mode). Figure 19 This is a characteristic curve diagram that shows an example of the time changes of various state quantities when switching from reverse mode (backward mode) to forward mode (forward mode). Figure 20 This refers to the second embodiment. Figure 4 The same composition diagram. Figure 21 yes Figure 20 Enlarged view of part (C) in the image. Figure 22 From the perspective of the power source Figure 20 An explanatory diagram of the planetary structure in the image. Figure 23 It means Figure 20 A characteristic curve diagram showing the relationship between the rotational speeds of the three components of a planetary mechanism. Figure 24 This refers to the sixth variation (the configuration where the input shaft is connected to the annular component and the first transmission is connected to the gear carrier) and... Figure 20 The same composition diagram. Figure 25 This refers to the seventh variation (a configuration where the input shaft is connected to the gear carrier and the first transmission is connected to the annular component) and... Figure 20 The same composition diagram. Detailed Implementation

[0009] Hereinafter, taking the case of a vehicle (wheel loader) as an example, the transmission device (gearbox) based on the implementation method and its variations will be described in detail with reference to the accompanying drawings.

[0010] Figures 1 to 9 This indicates the first implementation method. Figure 1In this example, the wheel loader 1 is a representative vehicle (operating vehicle). The wheel loader 1 is configured as an articulated operating vehicle that allows the front body 3 and the rear body 5 to bend and connect in the left-right direction. The front body 3 has left and right front wheels 2, and the rear body 5 has left and right rear wheels 4. In other words, 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. The front body 3 and the rear body 5 bend left and right around the central hinge 6 by extending or retracting the steering cylinder. Thus, the wheel loader 1 can be steered while driving.

[0011] At the front of the wheel loader 1, on the vehicle body 3, is a cargo loading / unloading machine 7, which is capable of pitching motion. The cargo loading / unloading machine 7 has a loading bucket 7A. Meanwhile, at the rear of the wheel loader 1, on the vehicle body 5, is a compartment 8 (which serves as the driver's cab), an engine 9, a hydraulic pump 10, and a transmission device 21 (which acts as a gearbox, power transmission device). Inside the compartment 8, there is 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. Additionally, although not shown in the illustrations, the compartment 8 contains a driver's seat, a steering wheel, a brake pedal, and a parking brake switch.

[0012] An operation amount detector 8C is provided on the accelerator pedal 8A to detect the operation amount θ1 of the accelerator pedal 8A. The FNR lever 8B is operated by the operator to switch the wheel loader 1 to forward and reverse, and to change the gear. When the wheel loader 1 moves forward, the operator switches the FNR lever 8B to the forward position (F). When the wheel loader 1 moves backward, the operator switches the FNR lever 8B to the reverse position (R). When the wheel loader 1 is stationary or when the operator wants to stop while moving, the operator switches the FNR lever 8B to the neutral position (N). When changing the gear, 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 consist of a single internal combustion engine (engine 9), or, for example, a combination of an engine and an electric motor, or a single electric motor. Hydraulic pump 10 is connected to engine 9. Hydraulic pump 10 is the hydraulic source used to operate the cargo 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 changes the speed (increases and / or decreases) of the rotation of the engine 9 and transmits the power to the front driveshaft 14 and the rear driveshaft 15. In other words, 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 front and rear 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. In other words, as... Figure 2 As shown, the transmission 21 has 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 21 performs speed changes and forward / reverse rotation between the input shaft 22 and the output shafts 23A and 23B by switching the power transmission path within the transmission 21.

[0017] Here, Figure 10 The ideal driving force line diagram of wheel loader 1 is shown. Figure 10 The diagram shows the ideal drive force line Lf in the forward direction and the ideal drive force line Lr in the reverse direction. When moving forward, high traction is required for digging, and high speed (0–40 km / h) is required for returning. Furthermore, the wheel loader 1 needs to stably climb uphill slopes with varying gradients, such as those found in quarries. Therefore, for example, at speeds above 3 km / h, a constant horsepower traction force independent of speed is desired.

[0018] Figure 10 The range A in the diagram represents the range where high traction is required for excavation; in other words, it represents the range A of the driving force line during excavation. Figure 10 The range B in the equation is the range of traction force requiring constant horsepower regardless of vehicle speed; in other words, it represents the range B of the driving force line with constant horsepower in the forward direction. Figure 10 In this context, range C represents the range of traction forces requiring constant horsepower regardless of vehicle speed; that is, it represents the range C of the driving force line with constant horsepower in the reverse direction.

[0019] like Figure 3 as well as Figure 4As shown, the transmission device 21 based on the first embodiment includes a planetary continuously variable transmission (CVT) 24, a direct-drive mechanism 27, and a multi-stage transmission mechanism 26. In this case, the transmission device 21 has the following modes: transmitting power to the multi-stage transmission mechanism 26 while continuously shifting the planetary CVT 24; internally locking the planetary CVT 24 and transmitting power to the multi-stage transmission mechanism 26; and transmitting power to the multi-stage transmission mechanism 26 without via the external locking mechanism (direct-drive mechanism 27) of the planetary CVT 24. Power transmission based on internal locking is performed by stopping the rotation of the component (e.g., the first sun gear 29B) connected to the first transmission 33 among the three components (e.g., the gear carrier 29A, the first sun gear 29B, and the second sun gear 29C) of the planetary gear mechanism 29 constituting the planetary CVT 24.

[0020] On the other hand, power transmission based on external locking is performed via an external locking mechanism (direct coupling mechanism 27) mounted outside the planetary continuously variable transmission 24. In this case, power transmission based on external locking is performed in a state where power transmission based on the planetary continuously variable transmission 24 is stopped. This stopping is performed by releasing (or reducing torque) the component (e.g., the first sun gear 29B) connected to the first transmission 33 among the three components of the planetary gear mechanism 29 (e.g., gear carrier 29A, first sun gear 29B, and second sun gear 29C).

[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 has: two sun gears 29B and 29C; and a central axis S of these two sun gears 29B and 29C. Figure 8 Planetary gear 29D and balancing gear 29E revolve around the sun gears 29B and 29C and rotate on their own axis; a gear carrier 29A rotatably supports planetary gear 29D and balancing gear 29E and rotates on its own axis around the central axis S of the two sun gears 29B and 29C.

[0022] The transmission device 21 based on the first embodiment will be described in detail below. Furthermore, Figure 3 In the diagram, the planetary gear mechanism 29 of the transmission device 21 is shown within a box (rectangle). In contrast, Figure 4 The image shows the interior of the planetary gear mechanism 29, that is, the specific gear arrangement of the planetary gear mechanism 29. Additionally, Figure 3 as well as Figure 4In order to avoid complicating the accompanying drawings, the output shaft 23 of the transmission device 21 is simplified as a common output shaft 23 (=output shafts 23A, 23B) that transmits power to both the front axle 12 and the rear axle 13. That is to say, Figure 3 as well as Figure 4 In this text, the configuration that distributes power between the output shaft 23A on the front side and the output shaft 23B on the rear side via, for example, a central differential mechanism, is omitted. (This will be discussed later.) Figure 7 The same applies. Additionally, Figure 7 The hydraulic pump 10 and gears 10A and 10B are also omitted in the text.

[0023] Figure 3 as well as Figure 4 This is a structural diagram of the transmission device 21 based on the first embodiment, and more specifically, a structural diagram of the transmission device 21 having both internal and external locking mechanisms. The transmission device 21 includes an input shaft 22 as an input component, an output shaft 23 as an output component, 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-drive mechanism 27 as an external locking mechanism. The direct-drive mechanism 27 includes a first clutch 27C connected when power is transmitted through the direct-drive mechanism 27.

[0024] Furthermore, the transmission device 21 has an inertial element 28 (inertial shaft 28A, first inertial gear 28B, and second inertial gear 28C) that mechanically connects the planetary continuously variable transmission mechanism 24, the multi-stage transmission mechanism 26, and the direct-drive mechanism 27. Moreover, as described later... Figure 7 As shown, the transmission device 21 has 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 rotates via the engine 9, which serves as the power source (prime mover) of the vehicle (wheel loader 1). In other words, 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-drive mechanism 27 is provided on the input shaft 22. The input shaft 22 is connected to a planetary continuously variable transmission mechanism 24 (more specifically, a planetary gear mechanism 29) via a first connecting member 30. 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 a 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] Power input from input shaft 22 to transmission device 21 is transmitted to inertial element 28 via planetary continuously variable transmission mechanism 24 or direct drive mechanism 27. Power transmitted to inertial element 28 is output from output shaft 23 via multi-stage transmission mechanism 26. Planetary continuously variable transmission mechanism 24 is located between input shaft 22 and output shaft 23 (specifically, between input shaft 22 and multi-stage transmission mechanism 26, more specifically, between input shaft 22 and inertial element 28). Planetary continuously variable transmission mechanism 24 shifts the rotational speed on input shaft 22 and transmits it to output shaft 23. The input side of planetary continuously variable transmission mechanism 24 is connected to the input shaft 22 of direct drive mechanism 27, which has an input gear 27A. The output side of planetary continuously variable transmission mechanism 24 is connected to inertial shaft 28A of inertial 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 33. This internally locked state is achieved, for example, by stopping the second connecting member 31 by performing a braking operation on the first transmission 33. The braking operation of the first transmission 33 will be described next. In the internally locked state of the planetary continuously variable transmission 24, the power input from the input shaft 22 is transmitted to the inertial element 28 (first inertial gear 28B) through the "first connecting member 30 that connects the planetary gear mechanism 29 (e.g., the gear carrier 29A) to 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) to the inertial element 28".

[0028] In the first embodiment, the transmission device 21, as the power transmission path that transmits the power input from the engine 9 to the input shaft 22 to the multi-stage transmission mechanism 26, can be arbitrarily selected from the following three paths (A), (B), and (C). (A) is the continuously variable transmission path (first power transmission path) through which the power input from the engine 9 to the input shaft 22 is transmitted to the multi-stage transmission mechanism 26 while the planetary continuously variable transmission mechanism 24 is continuously variable. At this time, the first clutch 27C, which is a direct-drive clutch, is released, and the second clutch 36 and the third clutch 37 of the planetary continuously variable transmission mechanism 24 are engaged. The state of transmitting power via the continuously variable transmission path is called the first power transmission state. (B) is the internal lock-up path (second power transmission path) through which power input from engine 9 to input shaft 22 is transmitted to multi-stage transmission 26 while the planetary continuously variable transmission 24 is internally locked. At this time, the first clutch 27C, which is a direct-drive clutch, is released, and the second clutch 36 of the planetary continuously variable transmission 24 is engaged. The third clutch 37 is engaged as needed. The state of transmitting power via the internal lock-up path is referred to as the second power transmission state. (C) is the external lock-up path (third power transmission path) through which power input from engine 9 to input shaft 22 is transmitted to multi-stage transmission mechanism 26 via direct coupling mechanism 27. This external lock-up path is a power transmission path via direct coupling mechanism 27, bypassing planetary continuously variable transmission mechanism 24. At this time, the first clutch 27C, which is a direct coupling clutch, is engaged, and the second clutch 36 and the third clutch 37 of planetary continuously variable transmission mechanism 24 are released as needed. The state of transmitting power via the external lock-up path is called the third power 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 continuously variable and power is transmitted. When it is suitable for the planetary CVT 24 to be internally locked, the planetary CVT 24 is internally locked and power is transmitted. When it is suitable for power transmission via the direct coupling mechanism 27, power is transmitted via the direct coupling mechanism 27.

[0030] Table 1 below shows the combination of power transmission paths for the transmission device 21 with both internal and external locking. In this case, the multi-stage transmission mechanism 26 has three forward gears and one reverse gear. That is, the multi-stage transmission mechanism 26 can select forward 1st speed, forward 2nd speed, forward 3rd speed, and reverse 1st speed.

[0031] [Table 1]

[0032] As shown in Table 1, when traveling forward, the power transmission state is set from a low speed state in the following sequence: "Forward 1st speed continuously variable transmission", "Forward 1st speed internal lock", "Forward 1st speed external lock", "Forward 2nd speed internal lock", "Forward 2nd speed external lock", "Forward 3rd speed internal lock", and "Forward 3rd speed external lock". When traveling backward, the power transmission state is set from a low speed state in the following sequence: "Reverse 1st speed continuously variable transmission", "Reverse 1st speed internal lock", and "Reverse 1st speed external lock".

[0033] Figure 11 A diagram showing the driving force lines of the transmission device 21 with the power transmission states shown in Table 1. (See diagram for reference.) Figure 11 As shown, the forward gear can be shifted in seven gears: forward 1st speed continuously variable transmission (CVT) Lf1, forward 1st speed internal lock-up Lf2, forward 1st speed external lock-up Lf3, forward 2nd speed internal lock-up Lf4, forward 2nd speed external lock-up Lf5, forward 3rd speed internal lock-up Lf6, and forward 3rd speed external lock-up Lf7.

[0034] On the other hand, the reverse direction can be shifted through three gears: reverse 1st speed continuously variable transmission Lr1, reverse 1st speed internal lock Lr2, and reverse 1st speed external lock Lr3. The transmission device 21 with the power transmission states shown in Table 1 can obtain high traction when moving in the reverse direction, can obtain high vehicle speed (0-16 km / h) during transport and return, and can stably climb uphill roads with a variety of slopes.

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

[0036] [Table 2]

[0037] As shown in Table 2, when traveling forward, the power transmission state can be set from a low speed state according to the sequence of "Forward 1st speed CVT", "Forward 1st speed internal lock", "Forward 1st speed external lock", "Forward 2nd speed CVT", "Forward 2nd speed internal lock", "Forward 2nd speed external lock", "Forward 3rd speed CVT", "Forward 3rd speed internal lock", and "Forward 3rd speed external lock". The same applies when traveling backward.

[0038] Figure 12 A diagram showing the driving force lines of the transmission device 21 with the power transmission states shown in Table 2. (See diagram for reference.) Figure 12 As shown, the forward gear can be shifted in nine gears: forward 1st speed continuously variable transmission (CVT) Lf1, forward 1st speed internal lock-up Lf2, forward 1st speed external lock-up Lf3, forward 2nd speed CVT Lf4, forward 2nd speed internal lock-up Lf5, forward 2nd speed external lock-up Lf6, forward 3rd speed CVT Lf7, forward 3rd speed internal lock-up Lf8, and forward 3rd speed external lock-up Lf9.

[0039] The advantage of having both a 2-speed forward CVT (Lf4) and a 3-speed forward CVT (Lf7) lies in the power transmission state changes when shifting from the 2-speed forward CVT (Lf4) to the 1-speed forward external lock-up (Lf3), and when shifting from the 3-speed forward CVT (Lf7) to the 2-speed forward external lock-up (Lf6). This is achieved through the transmission mechanism 21 transmitting power to... Figure 12When the Lf line shown in the diagram corresponds to a traction force of more than 70% of the vehicle speed, the wheel loader 1 preferably does not use the forward 2-speed CVT Lf4 or the forward 3-speed CVT Lf7 in order to save fuel consumption. This is because the power transmission efficiency of the transmission device 21 is worse than that of internal lock-up or external lock-up in CVT mode.

[0040] On the other hand, when the transmission 21 transmits traction force at or below 40% of the vehicle speed corresponding to the Lf line, it is preferable to use a 2-speed continuously variable transmission (CVT) Lf4 or a 3-speed CVT Lf7 to save fuel. This is because, although the power transmission efficiency of the transmission 21 is worse than that of internal or external lock-up in CVT mode, the efficiency of the engine 9, as the power source, will not decrease further. In this case, by reducing the rotational speed of the engine 9 and increasing its efficiency, the combined efficiency of the transmission 21 and the engine 9 can be improved. Specifically, when the transmission 21 transmits traction force at or below 40% of the vehicle speed corresponding to the Lf line within the range of 0 to 16 km / h, the 3-speed CVT can save fuel. When the transmission 21 transmits traction force at or below 40% of the vehicle speed corresponding to the Lf line within the range of 0 to 9 km / h, the 2-speed CVT 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 gearbox 33, a second gearbox 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 gearbox 33 side) via a second connecting member 31. The planetary gear mechanism 29 is connected to the second output side (inertial element 28 side) via a third connecting member 32.

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

[0043] The first transmission 33 (hereinafter also referred to as the first hydraulic pump motor 33) and the second transmission 34 (hereinafter also referred to as the second hydraulic pump motor 34) are configured such that, even when the rotational speeds of the first transmission 33 and the second transmission 34 are different, power can be transmitted between them while continuously variable transmission (CVT) is performed. For this purpose, a transmission element 35 for transmitting power between the first transmission 33 and the second transmission 34 is provided. The transmission element 35 is, for example, constituted by electrical wiring or hydraulic piping. Figure 7 As shown, in the embodiment, the transmission element 35 is constituted by 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) power from the first transmission 33 that exceeds the power acceptable to the second transmission 34. Additionally, the power absorption device 38 absorbs (processes or stores) power from the second transmission 34 that exceeds the power acceptable to the first transmission 33.

[0045] The power absorption device 38 can be configured as a power storage device (power storage device) and may be composed of a hydraulic accumulator or an electric storage device (battery). Alternatively, the power absorption device 38 can be configured as a power processing device (power processing device) and may be composed of a connecting valve (relief valve, on / off valve) or a resistance device (resistor). Figure 7 As shown, in the embodiment, the power absorption device 38 is constituted by variable relief valves 38A and 38B (first variable relief valve 38A and second variable relief valve 38B). Furthermore, the functions of the first transmission 33, the second transmission 34, and the transmission element 35 can also be constituted by an infinitely large ratio transmission (IVT). Additionally, if the first transmission 33 and the second transmission 34 are electric motors and generators, they can be configured to include inverters and converters as needed.

[0046] A second clutch 36 is provided between the planetary gear mechanism 29 and the first transmission 33, that is, between the second connecting member 31 and the first transmission 33. The second clutch 36 is, for example, a friction-based clutch (friction disc), a dog clutch, or a dog clutch with synchronizing gears. The second clutch 36 performs the mechanical engagement and disengagement between the second connecting member 31 and the first transmission 33. In other words, the second clutch 36 switches the transmission and release of power between the planetary gear mechanism 29 and the first transmission 33.

[0047] The controller 25 is configured, for example, as a microcomputer with an arithmetic circuit (CPU), memory, etc. 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 33. The controller 25 controls the rotational speed of the second transmission 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 Furthermore, the controller 25 controls the engagement and disengagement of the forward 1st speed clutch 69, the reverse 1st speed clutch 70, the forward 2nd speed clutch 75, and the forward 3rd speed 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 based on 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 33 can be stopped (or reduced), and the power loss caused by the rotation of the first transmission 33 can be reduced.

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

[0050] Furthermore, the idler shaft 28A is connected to the second transmission 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 reverse gear 64 (reverse 1st speed gear 67) and the forward 3rd speed gear 73 of the multi-stage transmission mechanism 26. Furthermore, the second idler gear 28C meshes with the forward 1st speed gear 66 and the forward 2nd speed 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 transmission mechanism 39 is provided between the second transmission 34 and the inertial element 28 (inertial shaft 28A) to change speeds between the second transmission 34 and the inertial element 28. This transmission mechanism 39 may also be omitted. In this case, a third clutch 37 can be provided between the inertial shaft 28A of the inertial element 28 and the rotating shaft (second rotating shaft 43) of the second transmission 34, through which the connection and release between the inertial shaft 28A and the rotating shaft of the second transmission 34 are performed.

[0052] The third clutch 37 is, for example, a friction-based clutch (friction disc), a dog clutch, or a dog clutch with synchronized gears. The third clutch 37 mechanically engages and disengages the second transmission 34 and the inertial element 28. The controller 25 controls the engagement and disengagement of the third clutch 37. For example, when power transmission based on the second transmission 34 is not required, the controller 25 outputs a signal to disengage the third clutch 37, thus disengaging it. This stops (or reduces) the rotation of the second transmission 34, reducing power loss caused by its rotation. However, under these conditions, it may not be necessary to disengage the third clutch 37.

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

[0054] However, since the torque distribution ratio between the second connecting member 31 and the third connecting member 32 is fixed, power is not always transmitted from the first transmission 33 to the second transmission 34; there are instances where power is transmitted from the second transmission 34 to the first transmission 33. The power transmitted from the third connecting member 32 to the inertial element 28 is less lost compared to the power transmitted from the second connecting member 31 via the first transmission 33 and the second transmission 34. Therefore, the planetary continuously variable transmission (CVT) 24, composed of the transmissions 33 and 34 and the planetary gear mechanism 29, has higher power transmission efficiency than a CVT that transmits power solely through the transmissions.

[0055] Figure 7 The specific configuration of the first transmission 33, the second transmission 34, the transmission element 35, and the power absorption device 38 is shown. 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 33, a pair of main lines 35A and 35B (first main line 35A and second main line 35B) corresponding to the transmission element 35, a second hydraulic pump motor 34 corresponding to the second transmission 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 line 44, bypass lines 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 first rotating shaft 42 by rotation, thereby causing hydraulic oil to circulate within a pair of main pipelines 35A and 35B.

[0057] The first hydraulic pump motor 33 is, for example, a variable displacement type swashplate or swashplate type hydraulic pump motor (hydraulic rotary machine). The first hydraulic pump motor 33 is a hydraulic device (hydraulic pump or hydraulic motor) that 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 an adjuster 33A for adjusting the volume (pump volume, motor volume). The adjuster 33A is based on commands (command signal W) from the controller 25. P (and thus subject to variable control.)

[0058] A pair of main lines 35A and 35B connects a pair of feed ports of the first hydraulic pump motor 33 to a pair of feed ports of the second hydraulic pump motor 34. The second hydraulic pump motor 34 is connected to the first hydraulic pump motor 33 via the pair of main lines 35A and 35B (the first main line 35A and the second main line 35B). The second hydraulic pump motor 34 rotates by hydraulic oil supplied from the first hydraulic pump motor 33. The second hydraulic pump motor 34 is connected to the inertial element 28 (inertial shaft 28A) via a third clutch 37 and a gearbox 39. The second hydraulic pump motor 34 drives the second rotating shaft 43 by rotation, thereby allowing hydraulic oil to circulate within the pair of main lines 35A and 35B.

[0059] The second hydraulic pump motor 34 is, for example, a variable displacement type swashplate or swashplate type hydraulic pump motor (hydraulic rotary machine). The second hydraulic pump motor 34 is a hydraulic device (hydraulic motor or hydraulic pump) that 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 an adjuster 34A for adjusting the volume (motor volume, pump volume). The adjuster 34A is variablely controlled based on commands (command signal WM) from the controller 25.

[0060] The hydrostatic continuously variable transmission (CVT) 41 includes: variable relief valves 38A and 38B capable of changing the set pressure (overflow set pressure, overflow start pressure); and check valves 47 and 48 that allow unidirectional flow of hydraulic oil and prevent reverse flow of hydraulic oil. Specifically, the first main pipeline 35A and the second main pipeline 35B of the hydrostatic CVT 41 are connected by a connecting pipeline 44. The first hydraulic pump motor 33 and the second hydraulic pump motor 34 transmit power 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 from the input shaft 22 side to the output shaft 23 side, the pressure in the first main pipeline 35A is higher than that in the second main pipeline 35B. Furthermore, for example, when the rotational speed is changed from the output shaft 23 side to the input shaft 22 side, the pressure in the second main pipeline 35B is higher than that in the first main pipeline 35A. A pair of check valves 47 and 48 are provided on the connecting pipe 44 that connects 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 hydraulic oil to flow from the second main line 35B side to the first main line 35A side, preventing hydraulic oil from flowing in the reverse direction. That is, the first check valve 47 enables the flow of working oil from the second main line 35B to the first main line 35A and cuts off the flow of working oil from the first main line 35A to the second main line 35B. Another check valve 48 (hereinafter also referred to as the second check valve 48) allows hydraulic oil to flow from the first main line 35A side to the second main line 35B side, preventing hydraulic oil from flowing in the reverse direction. That is, the second check valve 48 enables the flow of working oil from the first main line 35A to the second main line 35B and cuts off the flow of working oil from the second main line 35B to the first main line 35A.

[0062] On the connecting line 44, there are bypass lines 45 and 46 that bypass the check valves 47 and 48. 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] In other words, 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 specified 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, and opens the line when the pressure exceeds the specified pressure. 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 specified 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, and opens the line when the pressure exceeds the specified pressure. The variable relief valves 38A and 38B are controlled by a command signal (command signal W) from the controller 25. A W B This is achieved by an electrically operated relief valve (e.g., a solenoid relief valve) that changes the opening pressure (relief pressure). The change of the set pressure (relief set pressure, i.e., the relief start pressure) of the variable relief valves 38A and 38B is based on a command signal (command signal W) from the controller 25. A W B And so it is carried out.

[0064] A first speed detector 49 is located 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 located 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 located on 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 is connected to the hydraulic pressure P of the first main pipeline 35A. A The corresponding detection signal is output to the controller 25. 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 will be connected to the hydraulic pressure P of the second main pipeline 35B. B The corresponding detection signal is output to the controller 25.

[0066] The third pressure detector 53 is located at 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 will be compared with the clutch pressure P of the first clutch 27C. C The corresponding detection signal is output to controller 25. Operational 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 controller 25 receives the output value (volume θ2) of the volume sensor (not shown) of the first hydraulic pump motor 33 and the output value (volume θ3) of the volume sensor (not shown) of the second hydraulic pump motor 34.

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

[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 shown by a box (rectangle). The planetary gear mechanism 29 has three parts (rotating parts): a first part connected to the engine 9, which serves as a power source; a second part connected to the first transmission 33; and a third part connected to the inertial element 28 on the output shaft 23 side. In the first embodiment, the planetary gear mechanism 29 is composed of a gear carrier and two sun gears (first sun gear and second sun gear). Table 3 below shows the combination of the constituent elements (gear 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 8As shown, in the first embodiment (that is, No. 1-A in Table 3), the planetary gear mechanism 29 has a gear carrier 29A corresponding to the first component, a first sun gear 29B corresponding to the second component, a second sun gear 29C corresponding to the third component, a planetary gear 29D, and a balance gear 29E. Furthermore, the power transmission of the first sun gear 29B, the second sun gear 29C, the planetary gear 29D, and the balance gear 29E may not be based on gear meshing; for example, it may be based on friction of a roller (outer peripheral surface).

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

[0072] The spin axis Sp of planetary gear 29D Figure 8 ) and the rotation shaft Sb of the balance gear 29E ( Figure 8 The planetary gear 29D and the balance gear 29E are supported on the gear 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 The planetary gear 29D revolves around the sun gear 29B and rotates 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] Furthermore, according to the first embodiment, the balancing gear 29E is disposed between the second sun gear 29 and the planetary gear 29D, but it may also be disposed between the first sun gear 29B and the planetary gear 29D. Alternatively, the balancing gear 29E may be disposed on both sides of the locations "between the second sun gear 29C and the planetary gear 29D" and "between the first sun gear 29B and the planetary gear 29D", or it may not be disposed on either side.

[0074] Figure 8This is a cross-sectional view of the planetary gear mechanism 29 from the power source side. The gear carrier 29A, the first sun gear 29B, and the second sun gear 29C are arranged concentrically. That is, the central axis S (rotation center axis) of the gear 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 planetary 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 planetary gear 29D. The balance gear 29E and the planetary gear 29D rotate freely in their rotational direction via the gear carrier 29A in a manner that enables the meshing of each gear, and are restricted to the revolution direction relative to the central axis S. Therefore, the planetary gear 29D rotates around its rotation axis Sp, which serves as the central axis of the planetary gear 29D, and revolves around the central axis S of the gear carrier 29A. Therefore, the trajectory Cp of the central axis (rotation axis Sp) of planetary gear 29D becomes a circle centered on the central axis S of gear carrier 29A. Balancing gear 29E rotates around its rotation axis Sb, which serves as its central axis, and revolves around the central axis S of gear carrier 29A. Therefore, the trajectory Cb of the central axis (rotation axis Sb) of balancing gear 29E becomes a circle centered on the central axis S of gear carrier 29A.

[0075] The meshing radius rs1 of the first sun gear 29B is the meshing radius on the side of the first sun gear 29B when the first sun gear 29B meshes with the planetary gear 29D. The meshing radius rp1 of the gear portion 29D1 of the planetary gear 29D is the meshing radius on the side of the gear portion 29D1 when the first sun gear 29B meshes with the planetary gear 29D. The meshing radius rs2 of the second sun gear 29C 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 rp2 of the gear portion 29D2 of the planetary gear 29D is the meshing radius on the side of the planetary gear 29D when the balance gear 29E meshes with the planetary gear 29D.

[0076] In the first embodiment (Table 3, No. 1-A), the gear carrier 29A is connected to the component (terminal) connected to the engine 9, namely the first connecting component 30, whereby the torque Tc of the gear carrier 29A is the torque that the engine 9 can generate. The first sun gear 29B is connected to the component (terminal) connected to the first transmission 33, namely the second connecting component 31, whereby the torque Ts1 of the first sun gear 29B is the torque that the first transmission 33 can generate. The second sun gear 29C is connected to the component (terminal) connected to the inertial element 28, namely the third connecting component 32, whereby the torque Ts2 of the second sun gear 29C is the torque reaction force received from the inertial gear 28B.

[0077] The ratio of the torque Ts1 of the first sun gear 29B, the torque Ts2 of the second sun gear 29C, and the torque Tc of the gear carrier 29A remains constant during power transmission by the planetary continuously variable transmission 24. Based on this rule, the controller 25 outputs a signal to control the first transmission 33, thereby controlling the torque of the second connecting member 31 (e.g., the first sun gear 29B) connected to the first transmission 33. In other words, the controller 25 controls the torque of the second connecting member 31 (e.g., the first sun gear 29B) by controlling the first transmission 33. Thus, the controller 25 indirectly controls the torque of the first connecting member 30 (e.g., the gear 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 inertial element 28. The result is that the transmitted torque can be controlled between the first connecting member 30 (e.g., gear carrier 29A) connected to the engine 9 and the third connecting member 32 (e.g., the second sun gear 29C) connected to the inertial 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 gear carrier 29A is constant. In this case, if the rotational speed of the second sun gear 29C increases, the rotational speed of the first sun gear 29B decreases. Conversely, if the rotational speed of the second sun gear 29C decreases, 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 33, controlling the rotational speed of the second connecting member 31 (e.g., the first sun gear 29B) connected to the first transmission 33. In other words, the controller 25 controls the rotational speed of the second connecting member 31 (e.g., the first sun gear 29B) by controlling the first transmission 33. Thus, the controller 25 indirectly controls the rotational speeds of the first connecting member 30 (e.g., the gear carrier 29A) connected to the engine 9 and the third connecting member 32 (e.g., the second sun gear 29C) connected to the inertial element 28. The result is that the gear ratio can be controlled between the first connecting member 30 (e.g., gear carrier 29A) connected to the engine 9 and the third connecting member 32 (e.g., the second sun gear 29C) connected to the inertial element 28.

[0079] When the ratio of the rotational speed of the second sun gear to the rotational speed of the gear carrier is 0, the rotation of the second sun gear 29C is 0. The second sun gear 29C is connected to the output shaft 23 via the third connecting member 32, the inertial element 28, and the multi-stage transmission mechanism 26. Therefore, when the rotational speed of the second sun gear 29C is 0 min... -1 In this case, the vehicle speed is 0 km / h. That is, the gear ratio of the planetary continuously variable transmission 24 is infinite. Furthermore, as... Figure 14As shown in the second variation (that is, No. 1-B in Table 3), the planetary gear mechanism 29 can also be configured such that the first sun gear 29B is connected to the first connecting member 30, which is a component connected to the engine 9; the gear carrier 29A is connected to the second connecting member 31, which is a component connected to the first transmission 33; and the second sun gear 29C is connected to the third connecting member 32, which is a component connected to the inertial element 28. Furthermore, as... Figure 15 As shown in the third variation (that is, No. 1-C in Table 3), the planetary gear mechanism 29 can also be configured such that the first sun gear 29B is connected to the first connecting member 30, the second sun gear 29C is connected to the second connecting member 31, and the gear carrier 29A is connected to the third connecting member 32.

[0080] Next, the internal locking action of the planetary continuously variable transmission (CVT) 24 will be explained. Regarding the power transmission efficiency between the planetary gear mechanism 29 and the inertial element 28, the power transmission path via the third connecting member 32 is higher than the power transmission path through the second connecting member 31, the first transmission 33, the transmission element 35, the second transmission 34, the third clutch 37, and the transmission 39. Therefore, to improve transmission efficiency, it is sufficient to stop the rotation of the second connecting member 31 connected to the first transmission 33, thus preventing power transmission between the first transmission 33 and the second transmission 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 33, but is entirely transmitted to the third connecting member 32 connected to the inertial element 28.

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

[0082] Alternatively, the internal locking state can also be achieved by fixing the rotating shaft of the first transmission 33 to the non-rotating part, thus preventing the rotation of the first transmission 33. For example, as... Figure 13As shown in the first variation, the internal locking state can also be achieved by fixing the second connecting member 31 to a non-rotating part (e.g., the housing of the transmission 21) via the braking mechanism 55. The braking mechanism 55 can be configured to fix the second connecting member 31, which is connected to the first transmission 33, to the non-rotating part via friction or mechanical engagement. In particular, when the first transmission 33 is a generator, it is preferable, from the viewpoint of power loss, that the second connecting member 31 is fixed to the non-rotating part via the braking mechanism 55.

[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 startup and excavation. During transport and return, power transmission is achieved by internally locking the planetary CVT mechanism 24 or by using an external locking mechanism (direct coupling mechanism 27). Thus, during startup and excavation (e.g., 0–7 km / h) when continuously shifting is required, power transmission efficiency can be improved through continuously shifting based on 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, power transmission is achieved by internally locking the planetary CVT mechanism 24 or by using an external locking mechanism (direct coupling mechanism 27), thereby further improving transmission efficiency compared to continuously variable transmission.

[0084] Next, refer to Figure 3 as well as Figure 4 The direct-drive mechanism 27 serves as an external locking mechanism. Direct-drive mechanism 27 transmits power supplied from engine 9 to inertial element 28 via gear meshing, bypassing planetary continuously variable transmission 24. Direct-drive mechanism 27 includes an input gear 27A located on input shaft 22, a locking gear 27B meshing with input gear 27A, and a first clutch 27C. Rotating shaft 27B1, equipped with locking gear 27B, is connected to inertial shaft 28A of inertial element 28 via the first clutch 27C.

[0085] The first clutch 27C is located between the input shaft 22 (more specifically, the rotating shaft 27B1) and the idler shaft 28A. The first clutch 27C is, for example, a friction-based clutch (friction disc), a dog clutch, or a dog clutch with a synchronizing gear. The first clutch 27C performs mechanical engagement and disengagement between the locking gear 27B (rotating shaft 27B1) and the idler element 28 (idler shaft 28A). When the second clutch 36 is released and the first clutch 27C is engaged, the power input from the input shaft 22 is transmitted from the input gear 27A, the locking gear 27B, and the first clutch 27C to the idler element 28 (the first idler gear 28B and the second idler gear 28C). 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 coupling mechanism 27, which serves as an external locking mechanism, without passing through the planetary continuously variable transmission mechanism 24.

[0086] Here, the external locking rotational 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] [Formula 1] Ir=N27A / N27B

[0088] In the case of a transmission device 21 having an external locking mechanism (direct connection mechanism 27) and performing 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 effectively utilize the gear ratio of the planetary continuously variable transmission 24 over a wider range, the external locking rotational speed ratio Ir is greater than the internal locking output gear ratio Ip. As a result, the speed increase range of the planetary continuously variable transmission 24 can be effectively utilized over a wider range. 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] [Formula 2] Ip = In × (N32 / N28B)

[0090] The transmission device 21, which has an external locking mechanism (direct coupling mechanism 27) and performs an internal locking action, can transmit power as follows: During operation and excavation (vehicle speed 0-7 km / h), power is transmitted while continuously variable transmission (CVT) is performed via planetary CVT 24. During transport and retrieval (vehicle speed 7 km / h and above), power is transmitted while the internal locking mechanism 24 is engaged. During transport and retrieval (vehicle speed 10 km / h and above), power is transmitted via the external locking mechanism (direct coupling mechanism 27). Thus, the transmission device 21 can select the most efficient power transmission path during all operations, including excavation, operation, transport, and retrieval.

[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 braking switching. The multi-stage transmission mechanism 26 is, for example, equivalent to a planetary transmission, an intermediate shaft transmission, a manual transmission, an automatic-manual transmission, or a dual-clutch transmission. In the first embodiment, the multi-stage transmission mechanism 26 is composed of an intermediate shaft transmission with three forward gears and one reverse gear.

[0092] Reference Figure 6 The multi-stage transmission mechanism 26, which is an intermediate shaft type transmission, is described below. 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 reversing gear 64. The low-gear shaft unit 61 comprises a low-gear shaft 65, a forward 1st speed gear 66, a reverse 1st speed gear 67, a low-gear gear 68, a forward 1st speed clutch 69, and a reverse 1st speed clutch 70. The high-gear shaft unit 62 comprises a high-gear shaft 71, a forward 2nd speed gear 72, a forward 3rd speed gear 73, a high-gear gear 74, a forward 2nd speed clutch 75, and a forward 3rd speed clutch 76. The reversing gear 64 is used to reverse the rotation direction of the output shaft 77 of the output shaft unit 63. The output shaft unit 63 comprises 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 (that is, 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 reverse 1st speed gear 67 is always meshed with the first idler gear 28B via the reverse gear 64 and rotates together with the first idler gear 28B. The forward 3rd speed gear 73 is always meshed with the first idler gear 28B and rotates together with the first idler gear 28B. The forward 1st speed gear 66 is always meshed with the second idler gear 28C and rotates together with the second idler gear 28C. The forward 2nd speed gear 72 is always meshed with the second idler gear 28C and rotates together with the second idler gear 28C.

[0094] The reverse 1st speed clutch 70 engages and disengages the reverse 1st speed gear 67 with the low gear shaft 65. By engaging the reverse 1st speed gear 67 with the low gear shaft 65, power transmission is possible between the first idler gear 28B and the low gear shaft 65. The forward 1st speed clutch 69 engages and disengages the forward 1st speed gear 66 with the low gear shaft 65. By engaging the forward 1st speed gear 66 with the low gear shaft 65, power transmission is possible between the second idler gear 28C and the low gear shaft 65.

[0095] The forward 2-speed clutch 75 engages and disengages the forward 2-speed gear 72 with the high-gear shaft 71. By engaging the forward 2-speed gear 72 with the high-gear shaft 71, power transmission is possible between the second idler gear 28C and the high-gear shaft 71. The forward 3-speed clutch 76 engages and disengages the forward 3-speed gear 73 with the high-gear shaft 71. By engaging the forward 3-speed gear 73 with the high-gear shaft 71, 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] In other words, when the reverse 1st speed clutch 70 engages (connects) the reverse 1st speed gear 67 and the low gear shaft 65, the first idler gear 28B, the reverse gear 64, the reverse 1st speed gear 67, the reverse 1st speed 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, power transmitted from the planetary continuously variable transmission mechanism 24 or the direct-drive mechanism 27 to the idler element 28 (idler shaft 28A, first idler gear 28B) can be transmitted to the output shaft 77.

[0098] When the forward 1st speed clutch 69 engages (connects) the forward 1st speed gear 66 and the low gear shaft 65, the second idler gear 28C, the forward 1st speed gear 66, the forward 1st speed clutch 69, the low gear shaft 65, the low gear 68, the low gear output gear 78, and the output shaft 77 rotate as a whole. This allows power transmitted from the planetary continuously variable transmission mechanism 24 or the direct-drive mechanism 27 to the idler element 28 (idler shaft 28A, second idler gear 28C) and then to the output shaft 77.

[0099] When the forward 2nd speed clutch 75 engages (connects) the forward 2nd speed gear 72 and the high gear shaft 71, the second idler gear 28C, the forward 2nd speed gear 72, the forward 2nd speed clutch 75, the high gear shaft 71, the high gear gear 74, the high gear output gear 79, and the output shaft 77 rotate as a whole. This allows power transmitted from the planetary continuously variable transmission mechanism 24 or the direct-drive mechanism 27 to the idler element 28 (idler shaft 28A, second idler gear 28C) and then to the output shaft 77.

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

[0101] [Table 4]

[0102] In reverse 1st speed mode, reverse 1st speed clutch 70 is engaged, and forward 1st speed clutch 69, forward 2nd speed clutch 75, and forward 3rd speed clutch 76 are disengaged. In forward 1st speed mode, forward 1st speed clutch 69 is engaged, and reverse 1st speed clutch 70, forward 2nd speed clutch 75, and forward 3rd speed clutch 76 are disengaged. In forward 2nd speed mode, forward 2nd speed clutch 75 is engaged, and forward 1st speed clutch 69, reverse 1st speed clutch 70, and forward 3rd speed clutch 76 are disengaged. In forward 3rd speed mode, forward 3rd speed clutch 76 is engaged, and forward 1st speed clutch 69, reverse 1st speed clutch 70, and forward 2nd speed clutch 75 are disengaged.

[0103] Furthermore, in this embodiment, the second transmission 34 is connected to the inertial element 28 (inertial shaft 28A) via the third clutch 37 and the transmission 39. In contrast, as... Figure 16 As shown in the fourth variation, the second transmission 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) via the third clutch 37 and the transmission 39.

[0104] However, consider the case where an internal combustion engine is used as the power source for the vehicle. In this case, the engine's rotating shaft can reverse. Therefore, in order to enable the vehicle to move forward and backward, a mechanism is needed in the gearbox to switch the rotation of the input shaft between forward and reverse. Since wheel loaders operate frequently in both forward and reverse directions, it is preferable to include a function in the gearbox to reverse the rotation direction.

[0105] As a function to reverse the direction of rotation, it can be achieved by switching the forward and reverse power transmission paths through a clutch. However, when switching the output shaft of the gearbox between forward and reverse rotation, there will inevitably be a state where the rotation of the output shaft becomes zero. But it is difficult to switch the forward and reverse power transmission paths through the engagement and disengagement of the clutch at the instant that zero rotation is reached.

[0106] Therefore, in this embodiment, by using a planetary continuously variable transmission (CVT), the switching between forward and reverse power transmission paths can be performed smoothly. In other words, in this embodiment, the forward and reverse switching of the output shaft 23 of the transmission 21 (gearbox) can be performed smoothly, as can the forward and reverse switching of the wheel loader 1 (vehicle) be performed smoothly. 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. On the connecting pipeline 44, there are a first variable relief valve 38A, a second variable relief valve 38B, a first check valve 47, and a second check valve 48. The set pressure (relief set pressure, i.e., the relief start pressure) of the variable relief valves 38A and 38B is based on a command signal (command signal W) from the controller 25. A W B Control. Variable relief valves 38A and 38B correspond to connecting valves that can switch between the connected and disconnected states of a pair of main lines 35A and 35B.

[0108] The controller 25 can set the variable relief valves 38A and 38B to a cut-off state by increasing the set pressure of the variable relief valves 38A and 38B, that is, to a cut-off state that cuts off the connection between the pair of main pipes 35A and 35B. The controller 25 can also set the variable relief valves 38A and 38B to a connected state by decreasing the set pressure of the variable relief valves 38A and 38B, that is, to a connected state that connects the pair of main pipes 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., 35 MPa to 50 MPa). That is, when power is transmitted via the planetary continuously variable transmission 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., 35 MPa to 50 MPa). At this time, the working fluid flowing from the first hydraulic pump motor 33 to the second hydraulic pump motor 34 via the first main line 35A, from the first hydraulic pump motor 33 to the second hydraulic pump motor 34 via the second main line 35B, from the second hydraulic pump motor 34 to the first hydraulic pump motor 33 via the first main line 35A, and from the second hydraulic pump motor 34 to the first hydraulic pump motor 33 via the second main line 35B can be transported without detouring through the connecting pipe 44. Thus, power transmission between the first hydraulic pump motor 33 and the second hydraulic pump motor 34 is possible.

[0110] Furthermore, for example, if the pressure of the first main pipeline 35A becomes high (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 through the connecting pipe 44, the first variable relief valve 38A, and the second check valve 48 to the second main pipeline 35B. If the pressure of the second main pipeline 35B becomes high (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 through the connecting pipe 44, the second variable relief valve 38B, and the first check valve 47 to the first main pipeline 35A. Thus, by preventing the working fluid pressure from becoming excessively high, damage to the first hydraulic pump motor 33 and the second hydraulic pump motor 34 can be suppressed.

[0111] On the other hand, the controller 25 can cut off the power transmission based on the hydraulic pressure within the hydrostatic continuously variable transmission 41 by setting the variable relief valves 38A and 38B to the connected state (that is, by connecting a pair of main lines 35A and 35B). For example, by lowering 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 from 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 to the second main line 35B. 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. As a result, 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 supplied 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 becomes unable to transmit power to the first hydraulic pump motor 33 via the first main pipeline 35A.

[0112] Additionally, for example, by lowering the overflow pressure of the second variable relief valve 38B, the controller 25 allows the working fluid of the second main pipeline 35B to flow from 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 to the first main pipeline 35A. As a result, the working fluid supplied 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 becomes unable to transmit power to the second hydraulic pump motor 34 via the second main pipeline 35B. Similarly, the working fluid supplied 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 becomes unable to transmit power to the first hydraulic pump motor 33 via the second main pipeline 35B.

[0113] Additionally, for example, by lowering both the overflow pressure of the first variable relief valve 38A and the overflow pressure of 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 cannot be transmitted in both directions between the first hydraulic pump motor 33 and the second hydraulic pump motor 34. Furthermore, it is not necessary to provide both the first variable relief valve 38A and the second variable relief valve 38B; only one needs to be provided, and the other can be omitted. Also, it is not necessary to make both the first variable relief valve 38A and the second variable relief valve 38B electromagnetic relief valves; one can be an electromagnetic relief valve, and the other a relief valve with a fixed overflow pressure (fixed relief valve).

[0114] Figure 7 The hydrostatic continuously variable transmission (CVT) 41 shown uses variable relief valves 38A and 38B as a mechanism to cut off power transmission based on hydraulic pressure within the CVT 41. In contrast, as... Figure 17 As shown in the fifth variation, the first on / off valve 81A can also be arranged alongside the first variable relief valve 38A, and the second on / off valve 81B can be arranged alongside 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 between a connected state and a cut-off state. The on-off valves 81A and 81B correspond to connecting valves capable of switching between a pair of main pipelines 35A and 35B to a connected state and a cut-off state.

[0115] In other words, 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 cut-off 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. That is, the on / off valves 81A and 81B are electrically operated on / off valves (e.g., electromagnetic on / off 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 set 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. In addition, by opening the second on / off valve 81B, the overflow set 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] In other words, Figure 17 In the fifth variation shown, the opening of the first on / off valve 81A and the second on / off valve 81B establishes a connection between the pair of main pipelines 35A and 35B, thereby cutting off the power transmission based on the hydraulic pressure within the hydrostatic continuously variable transmission mechanism 41. Furthermore, 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 replaced with relief valves with fixed relief pressure (fixed relief valves). Alternatively, if both the first on / off valve 81A and the second on / off valve 81B are not required, only one can be provided.

[0117] Here, as Figure 3 as well as Figure 4As shown, when the controller 25 switches the transmission 21 from forward mode to reverse mode, it switches the forward 1st speed clutch 69 (which acts as the first output clutch) from the engaged state to the disengaged state, and switches the reverse 1st speed clutch 70 (which acts as the second output clutch) from the disengaged state to the engaged state. At this time, with the output shaft 23 rotating in the forward direction (forward direction), the controller 25 begins switching the forward 1st speed clutch 69 and the reverse 1st speed clutch 70. In other words, with the output shaft 23 rotating in the forward direction, the controller 25 begins switching the forward 1st speed clutch 69 from the engaged state to the disengaged state and the reverse 1st speed clutch 70 from the disengaged state to the engaged state.

[0118] Furthermore, when the controller 25 switches the transmission 21 from reverse mode (reverse mode) to forward mode (forward mode), it switches the reverse 1st speed clutch 70 from engaged to disengaged, and switches the forward 1st speed clutch 69 from disengaged to engaged. At this time, with the output shaft 23 rotating in the reverse direction (reverse direction), the controller 25 begins switching the reverse 1st speed clutch 70 and the forward 1st speed clutch 69. In other words, with the output shaft 23 rotating in the reverse direction, the controller 25 begins switching the reverse 1st speed clutch 70 from engaged to disengaged, and the forward 1st speed clutch 69 from disengaged to engaged.

[0119] When switching from forward mode to reverse mode, and from reverse mode to forward mode, the rotation of the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component and the third connecting component 32) is temporarily reversed. The following explains the switching from forward mode to reverse mode and the switching from reverse mode to forward mode.

[0120] First, refer to Figure 18 This indicates a switch from forward rotation mode to reverse rotation mode. Figure 18 This diagram illustrates an example of the pressure (clutch pressure) of the forward 1st speed clutch 69 and the reverse 1st speed clutch 70, the rotational speed of the first hydraulic pump motor 33 (first gearbox), the second hydraulic pump motor 34 (second gearbox), and the output shaft 23 when switching from forward mode to reverse mode, the pressure of the main pipelines 35A and 35B, the set pressure of the variable relief valves 38A and 38B, the flow rate of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the torque (output torque) of the output shaft 23, and the time variation of the volume of the first hydraulic pump motor 33 and the second hydraulic pump motor 34 when switching from forward mode to reverse mode. Figure 18During time A, the vehicle, i.e., the wheel loader 1, is traveling with a forward 1-speed continuously variable transmission (CVT). Additionally, the controller 25 will switch from a forward 1-speed CVT to a reverse 1-speed CVT. From... Figure 18 During the period from time A to time B, in order to reduce the speed of the wheel loader 1, power is transmitted from the output shaft 23 to the engine 9, which is the power source. At this time, the controller 25 engages the forward 1st speed clutch 69.

[0121] Furthermore, controller 25 controls the volume of the second hydraulic pump motor 34 (the hydraulic motor) to its maximum and controls the volume of the first hydraulic pump motor 33 (the hydraulic pump) so that the flow rate of the first hydraulic pump motor 33 is slightly less than the discharge flow rate of the second hydraulic pump motor 34. As a result, power flows from the second hydraulic pump motor 34 to the first hydraulic pump motor 33. That is, the fluid (working oil) discharged from the second hydraulic pump motor 34 flows through the second main pipeline 35B towards the first hydraulic pump motor 33, and then returns to the second hydraulic pump motor 34 through the first main pipeline 35A. At this time, the pressure in the second main pipeline 35B is higher than the pressure in the first main pipeline 35A.

[0122] During the period from time B to time G, controller 25 reduces the overflow pressure (overflow set pressure) of the first variable relief valve 38A from a pressure of 30-45 MPa to a pressure of 2.5-15 MPa. This ensures that even if the rotation directions of the first hydraulic pump motor 33 and the second hydraulic pump motor 34 are reversed, the occurrence of surge pressure in the first main pipeline 35A will be suppressed.

[0123] During the period from time C to time G, controller 25 reduces the overflow pressure of the second variable relief valve 38B from a pressure of 10-35 MPa to a pressure of 2.5-15 MPa. This limits the torque of the first hydraulic pump motor 33, thus limiting the volume of torque capable of transmitting power from the inertial element 28 to the engine 9. Meanwhile, during the period from time D to time F, controller 25 reduces the pressure of the forward 1st speed clutch 69. This reduces the volume of torque that the forward 1st speed clutch 69 can transmit. When the volume of torque that the forward 1st speed clutch 69 can transmit is higher than the volume of torque that the inertial element 28 can transmit power to the engine 9, the second variable relief valve 38B performs an overflow operation. Figure 18 (between C1 and C2).

[0124] The reason for reducing the overflow pressure of the second variable relief valve 38B is to prevent surge pressure and sudden changes in transmitted torque. The pressure of the forward 1st speed clutch 69 decreases from time D to 0 at time F. After time F, the forward 1st speed clutch 69 is fully disengaged. In contrast, the pressure of the reverse 1st speed clutch 70 increases during the period from time E to time I. At time G, which is in the middle of the period from time E to time I, the rotation direction of the second hydraulic pump motor 34 reverses. On the other hand, the rotation speed of the output shaft 23 remains in the forward direction. That is, during the period from time G to time H, the reverse 1st speed clutch 70 transmits power while slipping between the input side (reverse 1st speed gear 67) and the output side (low gear shaft 65) of the reverse 1st speed clutch 70 in different rotation directions.

[0125] The slippage decreases as the pressure of the reverse 1st speed clutch 70 increases, and disappears at time H. At time G, when the rotational direction of the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component, the third connecting component 32, and the second hydraulic pump motor 34) reverses, surge pressure is easily generated in the first main pipeline 35A. The variable relief valves 38A and 38B respond slowly to severe surge pressure, thereby suppressing surge pressure by pre-lowering the relief pressure of the first variable relief valve 38A. Figure 18 In the diagram, the double-dotted line 101 represents an example of surge pressure. During time G, the overflow pressure of the first variable relief valve 38A decreases, thereby suppressing surge pressure. Furthermore, during the period from time G to time H, the overflow pressure of the first variable relief valve 38A gradually increases. As a result, the torque transmitted in the direction of rotation of the planetary continuously variable transmission 24 increases from the counter-clockwise direction to the clockwise direction, enabling the wheel loader 1 traveling in the forward direction to decelerate. During the period from time G to time K, the first variable relief valve 38A performs an overflow operation. As a result, power is absorbed by the hydrostatic continuously variable transmission 41, enabling the wheel loader 1 traveling in the forward direction to decelerate.

[0126] During the period from time G to time J, the rotation direction of the planetary continuously variable transmission (CVT) 24 reverses. In the first embodiment, this corresponds to the planetary CVT 24 in... Figure 9 The state of operation along the Y1 line within the lower right quadrant (fourth quadrant) or upper left quadrant (second quadrant) of the four quadrants. Similarly, in the second embodiment, it corresponds to the planetary continuously variable transmission 24 operating along the Y1 line. Figure 23The state of operation along the Y2 line within the lower right quadrant (fourth quadrant) or upper left quadrant (second quadrant) of the four quadrants. That is, during the period from time G to time J, the output of the planetary continuously variable transmission 24 reverses, thereby causing the output shaft 23 to rotate in the forward direction, independent of the engagement of the reverse 1st speed clutch 70. After time J, the rotation direction of the planetary continuously variable transmission 24 returns to forward, and the output shaft 23 begins to rotate in the reverse direction.

[0127] During the period from time G to time L, torque fluctuations in the output shaft 23 are prone to occur, and the swaying of the wheel loader 1 is likely to increase. Therefore, it is preferable to maintain the overflow pressure of the second variable overflow valve 38B at a low pressure of 2.5 to 15 MPa. After time L following the end of the speed change, the overflow pressure of the second variable overflow valve 38B is maintained at a high pressure of 10 to 50 MPa. That is, the overflow pressure of the second variable overflow valve 38B rises to a pressure of 40 to 50 MPa during the period from time L to time M. Thus, the speed change from forward mode to reverse mode ends.

[0128] During this speed change from forward to reverse mode, the volume of the second hydraulic pump motor 34 is always controlled to its maximum, while the volume of the first hydraulic pump motor 33 needs to be changed. That is, during the period from time A to time G, the volume of the first hydraulic pump motor 33 is controlled such that the flow rate of the first hydraulic pump motor 33 is slightly less than the discharge flow rate of the second hydraulic pump motor 34. Thus, power flows from the second hydraulic pump motor 34 to the first hydraulic pump motor 33. In other words, the fluid discharged by the forward rotation of the first hydraulic pump motor 33 flows through the first main pipe 35A and towards the second hydraulic pump motor 34, and after the second hydraulic pump motor 34 rotates forward, it returns to the first hydraulic pump motor 33 through the second main pipe 35B. At this time, the second main pipe 35B becomes high pressure relative to the first main pipe 35A.

[0129] During the period from time G to time J, the maximum discharge volume of the first hydraulic pump motor 33 is controlled between 0% and 10%. The second hydraulic pump motor 34 rotates in reverse, supplying fluid (working oil) to the first main pipeline 35A. The first hydraulic pump motor 33 rotates in the forward direction, supplying fluid (working oil) to the first main pipeline 35A. The fluid supplied to the first main pipeline 35A flows through the first main pipeline 35A, connecting pipeline 44, first variable relief valve 38A, and second check valve 48 to the second main pipeline 35B, supplying fluid to the first hydraulic pump motor 33 and the second hydraulic pump motor 34. At this time, the flow rate flowing to the second check valve 48 is... Figure 18 The flow rate of the first hydraulic pump motor 33 (first gearbox) and the flow rate of the second hydraulic pump motor 34 (second gearbox) shown are combined. Furthermore, Figure 18The flow rate is set to positive (+) when both the first hydraulic pump motor 33 and the second hydraulic pump motor 34 are rotating in the forward direction, and to negative (-) when both are rotating in the reverse direction.

[0130] After time J, the volume of the first hydraulic pump motor 33 is controlled such that the flow rate of the first hydraulic pump motor 33 is slightly greater than the discharge flow rate of the second hydraulic pump motor 34. As a result, power flows from the first hydraulic pump motor 33 towards the second hydraulic pump motor 34. That is, the fluid discharged by the forward rotation of the first hydraulic pump motor 33 flows through the first main pipe 35A and towards the second hydraulic pump motor 34, and after the second hydraulic pump motor 34 is made to rotate forward, it returns to the first hydraulic pump motor 33 through the second main pipe 35B. At this time, the first main pipe 35A becomes high pressure relative to the second main pipe 35B.

[0131] Next, Figure 19 This represents an example of the pressure (clutch pressure) of the reverse 1st speed clutch 70 and the forward 1st speed clutch 69 when switching from reverse mode to forward mode, the rotational speed of the first hydraulic pump motor 33 (first gearbox), the second hydraulic pump motor 34 (second gearbox), and the output shaft 23, the pressure of the main pipelines 35A and 35B, the set pressure of the variable relief valves 38A and 38B, the flow rate of the first hydraulic pump motor 33 and the second hydraulic pump motor 34, the torque (output torque) of the output shaft 23, and the time change of the volume of the first hydraulic pump motor 33 and the second hydraulic pump motor 34. Figure 19 During time A, the vehicle, i.e., the wheel loader 1, is traveling in reverse 1-speed continuously variable transmission (CVT). Additionally, the controller 25 will switch from reverse 1-speed CVT to forward 1-speed CVT. Figure 19 During the period from time A to time B, in order to reduce the speed of the wheel loader 1, power is transmitted from the output shaft 23 to the engine 9, which is the power source. At this time, the controller 25 engages the reverse 1-speed clutch 70.

[0132] Furthermore, controller 25 maximizes the volume of the second hydraulic pump motor 34 (hydraulic motor) and controls the volume of the first hydraulic pump motor 33 (hydraulic pump) so that the flow rate of the first hydraulic pump motor 33 is slightly less than the discharge flow rate of the second hydraulic pump motor 34. As a result, power flows from the second hydraulic pump motor 34 to the first hydraulic pump motor 33. That is, the fluid (working oil) discharged from the second hydraulic pump motor 34 flows through the second main pipeline 35B to the first hydraulic pump motor 33, and then returns to the second hydraulic pump motor 34 through the first main pipeline 35A. At this time, the pressure in the second main pipeline 35B becomes higher than the pressure in the first main pipeline 35A.

[0133] During the period from time B to time G, controller 25 reduces the overflow pressure (overflow set pressure) of the first variable relief valve 38A from a pressure of 30-45 MPa to a pressure of 2.5-15 MPa. This ensures that even if the rotation directions of the first hydraulic pump motor 33 and the second hydraulic pump motor 34 are reversed, the occurrence of surge pressure in the first main pipeline 35A will be suppressed.

[0134] During the period from time C to time G, controller 25 reduces the overflow pressure of the second variable relief valve 38B from a pressure of 10-35 MPa to a pressure of 2.5-15 MPa. This limits the torque of the first hydraulic pump motor 33, thus limiting the volume of torque capable of transmitting power from the inertial element 28 to the engine 9. At this time, during the period from time D to time F, controller 25 reduces the pressure of the reverse 1st speed clutch 70. This reduces the volume of torque that the reverse 1st speed clutch 70 can transmit. When the volume of torque that the reverse 1st speed clutch 70 can transmit is higher than the volume of torque that the inertial element 28 can transmit power to the engine 9, the second variable relief valve 38B performs an overflow operation. Figure 19 (between C1 and C2).

[0135] The reason for reducing the overflow pressure of the second variable relief valve 38B is to prevent surge pressure and sudden changes in transmitted torque. The pressure of the reverse 1st speed clutch 70 decreases from time D to 0 at time F. After time F, the reverse 1st speed clutch 70 is fully released. In contrast, the pressure of the forward 1st speed clutch 69 increases during the period from time E to time I. At time G, which is in the middle of the period from time E to time I, the rotation direction of the second hydraulic pump motor 34 reverses. On the other hand, the rotation speed of the output shaft 23 remains in the reverse direction. That is, during the period from time G to time H, the forward 1st speed clutch 69 transmits power while slipping between the input side (forward 1st speed gear 66) and the output side (low gear shaft 65) of the forward 1st speed clutch 69 in different rotation directions.

[0136] The slippage decreases as the pressure of the forward 1st speed clutch 69 increases, and disappears at time H. At time G, when the rotation direction of the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component, the third connecting component 32, and the second hydraulic pump motor 34) reverses, surge pressure is easily generated in the first main pipeline 35A. The variable relief valves 38A and 38B respond slowly to severe surge pressure, thereby suppressing surge pressure by pre-lowering the relief pressure of the first variable relief valve 38A. Figure 19In the diagram, the double-dotted line 101 represents an example of surge pressure. During time G, the overflow pressure of the first variable relief valve 38A decreases, thereby suppressing surge pressure. Furthermore, during the period from time G to time H, the overflow pressure of the first variable relief valve 38A gradually increases. As a result, the torque transmitted in the direction of rotation of the planetary continuously variable transmission 24 increases from the reverse direction to the forward direction, enabling the wheel loader 1 traveling in the reverse direction to decelerate. During the period from time G to time K, the first variable relief valve 38A performs an overflow operation. As a result, power is absorbed by the hydrostatic continuously variable transmission 41, enabling the wheel loader 1 traveling in the reverse direction to decelerate.

[0137] During the period from time G to time J, the rotation direction of the planetary continuously variable transmission (CVT) 24 reverses. In the first embodiment, this corresponds to the planetary CVT 24 in... Figure 9 The state of operation along the Y1 line within the lower right quadrant (fourth quadrant) or upper left quadrant (second quadrant) of the four quadrants. Similarly, in the second embodiment, it corresponds to the planetary continuously variable transmission 24 operating along the Y1 line. Figure 23 The state of operation along the Y2 line is located in either the lower right quadrant (fourth quadrant) or the upper left quadrant (second quadrant) of the four quadrants. That is, during the period from time G to time J, the output of the planetary continuously variable transmission 24 is reversed, thereby causing the output shaft 23 to rotate in the reverse direction, independent of the engagement of the forward 1st speed clutch 69. After time J, the rotation direction of the planetary continuously variable transmission 24 returns to forward, and the output shaft 23 begins to rotate in the forward direction.

[0138] During the period from time G to time L, torque fluctuations in the output shaft 23 are likely to occur, and the swaying of the wheel loader 1 is likely to increase. Therefore, the overflow pressure of the second variable overflow valve 38B is preferably maintained at a low pressure of 2.5 to 15 MPa. After time L following the end of the speed change, the overflow pressure of the second variable overflow valve 38B remains at a high pressure of 10 to 50 MPa. That is, the overflow pressure of the second variable overflow valve 38B rises to a pressure of 40 to 50 MPa during the period from time L to time M. Thus, the speed change from reverse mode to forward mode ends.

[0139] During this speed change from reverse mode to forward mode, the volume of the second hydraulic pump motor 34 is always controlled to its maximum, while the volume of the first hydraulic pump motor 33 needs to be changed. That is, during the period from time A to time G, the volume of the first hydraulic pump motor 33 is controlled such that the flow rate of the first hydraulic pump motor 33 is slightly less than the discharge flow rate of the second hydraulic pump motor 34. Thus, power flows from the second hydraulic pump motor 34 to the first hydraulic pump motor 33. In other words, the fluid discharged by the forward rotation of the first hydraulic pump motor 33 flows through the first main pipe 35A and towards the second hydraulic pump motor 34, and after the second hydraulic pump motor 34 rotates forward, it returns to the first hydraulic pump motor 33 through the second main pipe 35B. At this time, the second main pipe 35B is at high pressure relative to the first main pipe 35A.

[0140] During the period from time G to time J, the maximum discharge volume of the first hydraulic pump motor 33 is controlled between 0% and 10%. The first hydraulic pump motor 33 rotates clockwise, supplying fluid (working oil) to the first main pipeline 35A. The second hydraulic pump motor 34 rotates counterclockwise, supplying fluid (working oil) to the first main pipeline 35A. The fluid supplied to the first main pipeline 35A flows through the first main pipeline 35A, connecting pipe 44, first variable relief valve 38A, and second check valve 48 to the second main pipeline 35B, supplying fluid to the first hydraulic pump motor 33 and the second hydraulic pump motor 34. At this time, the flow rate flowing to the second check valve 48 is... Figure 19 The combined flow rate of the first hydraulic pump motor 33 (first gearbox) and the second hydraulic pump motor 34 (second gearbox) shown. Furthermore, Figure 19 The flow rate is positive (+) when both the first hydraulic pump motor 33 and the second hydraulic pump motor 34 are rotating in the forward direction, and negative (-) when rotating in the reverse direction.

[0141] After time J, the volume of the first hydraulic pump motor 33 is controlled such that the flow rate of the first hydraulic pump motor 33 is slightly greater than the discharge flow rate of the second hydraulic pump motor 34. As a result, power flows from the first hydraulic pump motor 33 towards the second hydraulic pump motor 34. That is, the fluid discharged by the forward rotation of the first hydraulic pump motor 33 flows from the first main pipe 35A to the second hydraulic pump motor 34, and after the second hydraulic pump motor 34 is made to rotate forward, it returns to the first hydraulic pump motor 33 through the second main pipe 35B. At this time, the first main pipe 35A is at high pressure relative to the second main pipe 35B.

[0142] Next, the reason for preferably switching the forward 1st speed clutch 69 and the reverse 1st speed clutch 70 before the rotational speed of the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component and the third connecting component 32) reaches 0 will be explained. When switching between the forward and reverse modes, the following conditions are considered when the switching of the forward 1st speed clutch 69 and the reverse 1st speed clutch 70 begins: (A), (B), and (C). (A) Start when the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component and the third connecting component 32) is rotating in the forward direction. (B) The rotation of the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component and the third connecting component 32) changes from forward to reverse. (C) The rotation of the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component and the third connecting component 32) becomes zero at the point when the rotation becomes zero.

[0143] Regarding (C) above, if the responsiveness of the clutch control is not sufficiently improved, pulsations will occur in the torque of the output shaft 23 of the transmission 21, causing discomfort to the occupants, which is therefore undesirable. Thus, it is not preferable to begin switching between the forward 1st speed clutch 69 and the reverse 1st speed clutch 70 while the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component and the third connecting component 32) is rotating in the forward direction.

[0144] Here, in order to increase the permissible rotational speed of the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component and the third connecting component 32) in the reverse state, it is necessary to increase the permissible rotational speed of the first hydraulic pump motor 33. In this case, it is necessary to correct the relationship between the rotational speed ratios of the input shaft 22, the first hydraulic pump motor 33, and the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component and the third connecting component 32) to change the gear ratio of the planetary gear mechanism 29 so that the first hydraulic pump motor 33 does not exceed the permissible rotational speed. That is, to change... Figure 9 Y1 line, Figure 23 The inclination of the Y2 line. When the gear ratio of the planetary gear mechanism 29 is set in the direction that causes the first hydraulic pump motor 33 to rotate upward, the torque transmitted from the input shaft 22 to the planetary gear mechanism 29 is greater than the torque transmitted from the first hydraulic pump motor 33 (the first sun gear 29B of the second component) to the output side of the planetary continuously variable transmission mechanism 24 (the second sun gear 29C of the third component, the third connecting component 32). As a result, the first hydraulic pump motor 33 can be made smaller.

[0145] Furthermore, the transmission efficiency ratio between the first hydraulic pump motor 33 and the second hydraulic pump motor 34 is the difference in transmission efficiency from the output side of the planetary continuously variable transmission mechanism 24 (the second sun gear 29C of the third component and the third connecting component 32) to the output shaft 23 of the transmission device 21. To improve the transmission efficiency of the planetary continuously variable transmission mechanism 24, the gear ratio of the planetary gear mechanism 29 is set in the direction that increases the rotational speed of the first hydraulic pump motor 33, within the allowable range of the rotational speed of the first hydraulic pump motor 33. Therefore, in order to increase the allowable rotational speed of the output side of the planetary continuously variable transmission mechanism 24 (the second sun gear 29C of the third component and the third connecting component 32) in the reverse rotation state, there exists a so-called trade-off relationship where the transmission efficiency on the forward rotation side must be sacrificed.

[0146] Consider the case where switching between the forward 1st speed clutch 69 and the reverse 1st speed clutch 70 begins after the rotation of the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component and the third connecting component 32) changes from forward to reverse. In this case, compared to the case where switching begins when the rotation of the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component and the third connecting component 32) is in the forward direction, the permissible rotational speed in the reverse direction must be increased. Therefore, it is preferable to begin switching between the forward 1st speed clutch 69 and the reverse 1st speed clutch 70 when the rotation of the output side of the planetary continuously variable transmission 24 (the second sun gear 29C of the third component and the third connecting component 32) is in the forward direction.

[0147] Furthermore, the first hydraulic pump motor 33, serving as the first transmission, and the second hydraulic pump motor 34, serving as the second transmission, can also replace the hydraulic pump motor (hydraulic pump, hydraulic motor) of the hydraulic rotary machine, and be composed of an electric motor (electric motor) or a generator (generator motor). That is, the first transmission and the second transmission can also be composed of electric equipment instead of hydraulic equipment. When the first transmission 33 and the second transmission 34 are composed of electric equipment, the switching between forward and reverse modes is preferably initiated when the output side of the planetary continuously variable transmission mechanism 24 (the second sun gear 29C of the third component and the third connecting component 32) is rotating in the forward direction, switching between the forward 1st speed clutch 69 and the reverse 1st speed clutch 70.

[0148] As described above, according to the first embodiment, the transmission device 21 includes an input shaft 22 (input component), an output shaft 23 (output component), a planetary continuously variable transmission (CVT) 24, and a multi-stage transmission mechanism 26. Additionally, the transmission device 21 includes an inertial element 28. The input shaft 22 rotates via a power source (engine 9) mounted on the vehicle (wheel loader 1). The output shaft 23 outputs rotational speed 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 rotational speed on the input shaft 22 side and transmits it to the output shaft 23 side. The multi-stage transmission mechanism 26 changes the rotational speed on the output side of the planetary CVT 24 in stages by switching the transmission path of the meshing gears. The inertial element 28 connects the output side of the planetary CVT 24 and the multi-stage transmission mechanism 26.

[0149] The planetary continuously variable transmission 24 includes a planetary gear mechanism 29 (planetary mechanism), a first transmission 33 (first hydraulic pump motor 33), and a second transmission 34 (second hydraulic pump motor 34). For example Figure 4 as well as Figure 5 As shown, the planetary gear mechanism 29 has three components: a gear carrier 29A (first component) connected to the input shaft 22 side, a first sun gear 29B (second component) for the output side, and a second sun gear 29C (third component) for an output side different from the first sun gear 29B. In this case, the gear 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 33 via a second connecting member 31 and a second clutch 36. The second sun gear 29C (third component) is connected to an inertial element 28. That is, the second sun gear 29C (third component) is connected to the inertial element 28 (first inertial gear 28B) via a third connecting member 32. The first transmission 33 is connected to the first sun gear 29B of the planetary gear mechanism 29. The second transmission 34 is capable of transmitting power between itself and the first transmission 33.

[0150] The multi-stage transmission mechanism 26 has a forward 1st speed transmission path (forward transmission path, forward rotation transmission path) as the first output transmission path, and a reverse 1st speed transmission path (reverse transmission path, reverse rotation transmission path) as the second output transmission path. Additionally, the multi-stage transmission mechanism 26 has a forward 1st speed clutch 69 as the first output clutch and a reverse 1st speed clutch 70 as the second output clutch. The forward 1st speed transmission path is an output transmission path in which the number of gear engagements between the inertial element 28 (second inertial gear 28C) and the output shaft 23 is an odd number of times. Specifically, the forward 1st speed transmission path corresponds to the low-gear shaft unit 61 in the state where the forward 1st speed clutch 69 is connected. When the forward 1st speed gear 66 and the low-gear shaft 65 are engaged (connected) via the forward 1st speed clutch 69, the second inertial gear 28C, the forward 1st speed gear 66, the low-gear shaft 65, the low-gear gear 68, the low-gear output gear 78, and the output shaft 77 (output shaft 23) rotate as a single unit. When the forward 1st speed clutch 69 is engaged, the number of gear engagements is odd when the power transmitted to the inertial element 28 via the planetary continuously variable transmission mechanism 24 or the direct drive mechanism 27 is transmitted to the output shaft 77 (output shaft 23).

[0151] The reverse 1st speed transmission path is an output transmission path in which the number of gear engagements between the inertial element 28 (first inertial gear 28B) and the output shaft 23 is zero or an even number. Specifically, the reverse 1st speed transmission path corresponds to the low gear shaft unit 61 in the state of being connected with the reverse 1st speed clutch 70. When the reverse 1st speed gear 67 and the low gear shaft 65 are engaged (connected) by the reverse 1st speed clutch 70, the first inertial gear 28B, the reverse gear 64, the reverse 1st speed 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 reverse 1st speed clutch 70 is engaged, the number of gear engagements is an even number when transmitting power from the planetary continuously variable transmission mechanism 24 or the direct coupling mechanism 27 to the inertial element 28 to the output shaft 77 (output shaft 23).

[0152] In other words, the reversing 1st speed transmission path has a reversing gear 64, thus the forward 1st speed transmission path differs at the points where the number of gear engagements is "odd" and "zero or even". Therefore, the rotation direction of the output shaft 23 is reversed through the forward and reversing 1st speed transmission paths. Furthermore, the relationship between "odd" and "zero or even" can also be reversed in the forward and reversing 1st speed transmission paths. That is, it is also possible to designate the first output transmission path with an "odd" number of gear engagements as the reversing 1st speed transmission path (reversing transmission path, reversing transmission path), and the second output transmission path with a "zero or even" number of gear engagements as the forward 1st speed transmission path (forward transmission path, forward rotation transmission path).

[0153] A forward 1st speed clutch 69 is located in the forward 1st speed transmission path (lower gear shaft unit 61). The forward 1st speed clutch 69 switches the transmission and release of power in the forward 1st speed transmission path. That is, the forward 1st speed clutch 69 switches the engagement (connection) and disengagement of the forward 1st speed gear 66 and the lower gear shaft 65. A reverse 1st speed clutch 70 is located in the reverse 1st speed transmission path (lower gear shaft unit 61). The reverse 1st speed clutch 70 switches the transmission and release of power in the reverse 1st speed transmission path. That is, the reverse 1st speed clutch 70 switches the engagement (connection) and disengagement of the reverse 1st speed gear 67 and the lower gear shaft 65.

[0154] Additionally, the transmission 21 includes a controller 25. The controller 25 controls the engagement and disengagement of the forward 1st speed clutch 69. Furthermore, the controller 25 controls the engagement and disengagement of the reverse 1st speed clutch 70. The controller 25 can reverse the direction of travel of the vehicle, i.e., the wheel loader 1, by switching between a forward rotation mode (forward 1st speed continuously variable transmission state) and a reverse rotation mode (reverse 1st speed continuously variable transmission state). The controller 25 is set to forward rotation mode (forward 1st speed continuously variable transmission state) by engaging the forward 1st speed clutch 69 and disengaging the reverse 1st speed clutch 70. The controller 25 is set to reverse rotation mode (reverse 1st speed continuously variable transmission state) by disengaging the forward 1st speed clutch 69 and engaging the reverse 1st speed clutch 70.

[0155] When switching from forward rotation mode to reverse rotation mode, with the output shaft 23 rotating in the forward direction (forward state), the controller 25 initiates the switching of the forward 1st speed clutch 69 from the engaged state to the released state, and also initiates the switching of the reverse 1st speed clutch 70 from the released state to the engaged state. In other words, when switching from forward rotation mode to reverse rotation mode, with the output shaft 23 rotating in the forward direction (forward state), the controller 25 switches the forward 1st speed clutch 69 from the engaged state to the released state, and switches the reverse 1st speed clutch 70 from the released state to the engaged state. At this time, after starting the release of the forward 1st speed clutch 69 (pressure decrease), the controller 25 begins the engagement of the reverse 1st speed clutch 70 (pressure increase). Therefore, when switching from forward rotation mode to reverse rotation mode, the switching of the output shaft 23 from forward to reverse rotation can be performed smoothly, thus enabling smooth switching of the wheel loader 1 from forward to reverse.

[0156] Furthermore, when switching from reverse mode to forward mode, with the output shaft 23 rotating in reverse (reverse state), the controller 25 begins switching the reverse 1st speed clutch 70 from engaged to disengaged, and simultaneously begins switching the forward 1st speed clutch 69 from disengaged to engaged. In other words, when switching from reverse mode to forward mode, with the output shaft 23 rotating in reverse (reverse state), the controller 25 switches the reverse 1st speed clutch 70 from engaged to disengaged, and the forward 1st speed clutch 69 from disengaged to engaged. At this time, after releasing the reverse 1st speed clutch 70 (pressure decrease), the controller 25 begins engaging the forward 1st speed clutch 69 (pressure increase). Therefore, when switching from reverse mode to forward mode, the switching of the output shaft 23 from reverse to forward rotation is smooth, thus enabling a smooth switching of the wheel loader 1 from reverse to forward rotation.

[0157] like Figure 18 As shown, when switching from forward mode to reverse mode, the controller 25 reverses the output side of the planetary continuously variable transmission 24 by changing the rotational speed of the first gearbox 33 (first hydraulic pump motor 33), that is, it reverses the second sun gear 29C (the third component), thus reversing the rotation direction of the third connecting component 32. Therefore, when switching from forward mode to reverse mode, the reverse rotation of the output side of the planetary continuously variable transmission 24 can be performed smoothly. Furthermore, as... Figure 19 As shown, when switching from reverse mode to forward mode, the controller 25 reverses the output side of the planetary continuously variable transmission 24 by changing the rotational speed of the first gearbox 33 (first hydraulic pump motor 33). That is, it reverses the second sun gear 29C (the third component), thus reversing the rotational direction of the third connecting component 32. Therefore, when switching from reverse mode to forward mode, the reversal of the output side of the planetary continuously variable transmission 24 can be performed smoothly.

[0158] like Figure 7As shown, according to the first embodiment, the first transmission 33 is composed of a pump motor that functions as a hydraulic rotary machine (oil pressure rotary machine) performing pump operation or motor operation. That is, the first transmission 33 is a first hydraulic pump motor 33 for a hydraulic pump (oil pressure pump). Similarly, the second transmission 34 is composed of a pump motor that functions as a hydraulic rotary machine (oil pressure rotary machine) performing pump operation or motor operation. That is, the second transmission 34 is a second hydraulic pump motor 34 for a hydraulic motor (oil pressure motor). The first hydraulic pump motor 33 and the second hydraulic pump motor 34 are connected by a pair of main lines 35A and 35B. The pair of main lines 35A and 35B allow fluid (working oil) to flow. The pair of main lines 35A and 35B enables power transmission between the first hydraulic pump motor 33 and the second hydraulic pump motor 34. Between a pair of main pipelines 35A and 35B, there are relief valves, namely a first variable relief valve 38A and a second variable relief valve 38B, for controlling the connection and disconnection states between the main pipelines 35A and 35B. The controller 25 can change the connection start pressure (relief pressure) of the first variable relief valve 38A and the second variable relief valve 38B.

[0159] Based on this, when switching from forward mode to reverse mode, the controller 25 lowers the set value of the engagement start pressure of the first variable relief valve 38A before the start of switching of the forward 1st speed clutch 69 and the reverse 1st speed clutch 70. In other words, the controller 25 lowers the relief pressure of the first variable relief valve 38A before the start of switching of the forward 1st speed clutch 69 from the engaged state to the released state. That is to say, as Figure 18 As shown, the controller 25 reduces the overflow pressure of the first variable relief valve 38A at time B. Therefore, it is possible to suppress the occurrence of surge pressure in the first main pipeline 35A. Consequently, a smooth switching from forward to reverse mode is also possible.

[0160] Furthermore, when switching from reverse mode to forward mode, the controller 25 lowers the set value of the engagement start pressure of the first variable relief valve 38A before the start of switching of the reverse 1st speed clutch 70 and the forward 1st speed clutch 69. In other words, the controller 25 lowers the relief pressure of the first variable relief valve 38A before the start of switching of the reverse 1st speed clutch 70 from the engaged state to the released state. That is to say, as Figure 19 As shown, the controller 25 reduces the overflow pressure of the first variable relief valve 38A at time B. Therefore, it can suppress the occurrence of surge pressure in the first main pipeline 35A. This also allows for a smooth switching from reverse mode to forward mode.

[0161] Furthermore, when switching from forward to reverse mode, the controller 25 increases the set value of the connection start pressure of the first variable relief valve 38A during the switching process of the forward 1st speed clutch 69 from the engaged state to the released state and the reverse 1st speed clutch 70 from the released state to the engaged state. In other words, the controller 25 increases the relief pressure of the first variable relief valve 38A after starting the switching of the forward 1st speed clutch 69 from the engaged state to the released state and before the switching of the reverse 1st speed clutch 70 from the released state to the engaged state is completed. That is to say, as Figure 18 As shown, the controller 25 causes the overflow pressure of the first variable overflow valve 38A to rise during the period from time G to time H. As a result, the torque transmitted in the direction of rotation of the planetary continuously variable transmission 24 increases from the reverse direction to the forward direction, which enables the wheel loader 1 traveling in the forward direction to decelerate.

[0162] Furthermore, when switching from reverse mode to forward mode, the controller 25 increases the set value of the connection start pressure of the first variable relief valve 38A during the switching process of the reverse 1st speed clutch 70 from the engaged state to the released state and the forward 1st speed clutch 69 from the released state to the engaged state. In other words, the controller 25 increases the relief pressure of the first variable relief valve 38A after starting the switching of the reverse 1st speed clutch 70 from the engaged state to the released state and before the switching of the forward 1st speed clutch 69 from the released state to the engaged state is completed. That is to say, as Figure 19 As shown, the controller 25 causes the overflow pressure of the first variable overflow valve 38A to rise during the period from time G to time H. As a result, the torque transmitted in the direction of rotation of the planetary continuously variable transmission 24 increases from the reverse direction to the forward direction, which enables the wheel loader 1 traveling in the reverse direction to decelerate.

[0163] When switching from forward to reverse mode, the controller 25 sets the first variable relief valve 38A to be in operation during the period when the rotational direction of the output side (third component) of the planetary continuously variable transmission 24 is reversed by changing the rotational speed of the first transmission 33 (first hydraulic pump motor 33). That is, as... Figure 18 As shown, during the period from time G to time J, the pressure (dashed line) of the first main pipeline 35A increases relative to the set pressure (solid line) of the first variable relief valve 38A, causing the first variable relief valve 38A to perform an overflow operation. This allows power to be absorbed by the hydrostatic continuously variable transmission 41. Therefore, in this respect, a smooth switching from forward to reverse rotation mode is also possible.

[0164] When switching from reverse mode to forward mode, the controller 25 sets the first variable relief valve 38A to be in operation during the period when the rotational direction of the output side (third component) of the planetary continuously variable transmission 24 is reversed by changing the rotational speed of the first transmission 33 (first hydraulic pump motor 33). That is, as... Figure 19 As shown, during the period from time G to time J, the pressure (dashed line) of the first main pipeline 35A increases relative to the set pressure (solid line) of the first variable relief valve 38A, causing the first variable relief valve 38A to perform an overflow operation. This allows power to be absorbed by the hydrostatic continuously variable transmission 41. Therefore, in this respect, a smooth switching from reverse mode to forward mode is also possible.

[0165] Furthermore, in the first embodiment, the first transmission is constituted by the first hydraulic pump motor 33, and the second transmission is constituted by the second hydraulic pump motor 34, with these transmissions connected by a pair of main lines 35A and 35B. Alternatively, the first and second transmissions can each be constituted by an electric motor (electric motor and generator, electric motor, electric generator). In this case, the first and second transmissions are connected by an electrical circuit. An electric motor control device is provided in the circuit. The electric motor control device, for example, controls the power of the circuit. Thus, the first and second transmissions can transmit power via the circuit. In this case, when switching from the forward mode to the reverse mode, the switching of the forward 1st speed clutch 69 (first output clutch) and the reverse 1st speed clutch 70 (second output clutch) also begins when the output shaft 23 is rotating in the forward direction (forward state). Furthermore, when switching from reverse mode to forward mode, the output shaft 23 rotates in reverse (reverse mode), and the switching between the reverse 1st speed clutch 70 (second output clutch) and the forward 1st speed clutch 69 (first output clutch) begins. This allows for smooth switching between forward and reverse rotation of the output shaft 23, and thus smooth switching between forward and reverse rotation of the wheel loader 1.

[0166] In the first embodiment, during both "switching from forward mode to reverse mode" and "switching from reverse mode to forward mode," the switching of the forward 1st gear clutch 69 and the reverse 1st gear clutch 70 begins before the rotation on the output side of the planetary continuously variable transmission 24 (ultimately, the rotation of the output shaft 23) reverses. However, it is not necessary to perform this switching during both "switching from forward mode to reverse mode" and "switching from reverse mode to forward mode." That is, it is also possible to start the switching of the forward 1st gear clutch 69 and the reverse 1st gear clutch 70 before the rotation on the output side of the planetary continuously variable transmission 24 (ultimately, the rotation of the output shaft 23) reverses during either "switching from forward mode to reverse mode" or "switching from reverse mode to forward mode."

[0167] Next, Figures 20 to 23 This indicates the second embodiment. The second embodiment is characterized by a planetary gear mechanism consisting of a gear carrier, a sun gear, and a ring gear. Furthermore, in the second embodiment, the same reference numerals are used to denote the same constituent elements as in the first embodiment, and their descriptions are omitted.

[0168] In the first embodiment, the planetary gear mechanism 29 of the planetary continuously variable transmission 24 is described as an example, consisting of a gear carrier and two sun gears. In contrast, in the second embodiment, the planetary gear mechanism 91 of the planetary continuously variable transmission 24 can also be composed of a gear carrier 91A, a sun gear 91B, and a ring gear 91C. Table 5 below shows the combinations of the constituent elements (gear carrier, sun gear, and ring gear) of the planetary gear mechanism 91. Power transmission is possible in any case. "No. 2-A" in Table 5 improves the transmission efficiency of the planetary continuously variable transmission 24, reduces the maximum absorbed torque of the first transmission 33, and allows the planetary continuously variable transmission 24 to be constructed in a small and lightweight manner, therefore it is the most preferred option.

[0169] [Table 5]

[0170] like Figure 20 as well as Figure 21 As shown, in the second embodiment (that is, No. 2-A in Table 5), the planetary gear mechanism 91 has a gear carrier 91A corresponding to the first component, a sun gear 91B corresponding to the second component, a ring gear 91C corresponding to the third component, and a planetary gear 91D. Furthermore, the power transmission of the sun gear 91B, ring gear 91C, and planetary gear 91D may not be based on gear meshing; for example, it may be based on friction of a roller (outer peripheral surface).

[0171] Engine 9 (input shaft 22) is connected to gear carrier 91A via first connecting member 30. Sun gear 91B is connected to first transmission 33 via second connecting member 31. Ring gear 91C is connected to inertial element 28 (first inertial 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 Sp of planet gear 91D... Figure 22 The planetary gear 91D is supported on the gear carrier 91A. Therefore, the planetary gear 91D is positioned with respect to the central axis S of the planetary gear mechanism 91. Figure 22 It revolves around the sun while rotating on its own axis.

[0172] Next, the operation of the planetary gear mechanism 91, consisting of gear carrier 91A, sun gear 91B, and ring gear 91C, will be explained. The following applies under all conditions specified in Table 5: “No.2-A”, “No.2-B”, “No.2-C”, “No.2-D”, “No.2-E”, and “No.2-F”.

[0173] First, the torque distribution of the three components of the planetary gear mechanism 91 (gear carrier 91A, sun gear 91B, and ring gear 91C) will be explained. Figure 22 This is a cross-sectional view of the planetary gear mechanism 91 viewed from the power source side. The gear carrier 91A, sun gear 91B, and ring gear 91C are concentrically arranged. That is, the central axis S (rotation axis) of the gear carrier 91A, sun gear 91B, and ring gear 91C coincides. The planetary gear 91D is configured to engage with the outer circumference of the sun gear 91B and the inner circumference of the ring gear 91C. The planetary gear 91D meshes with the sun gear 91B and the ring gear 91C. The gear carrier 91A, sun gear 91B, and ring gear 91C are supported by the housing of the planetary continuously variable transmission 24 in such a manner that the meshing of each gear is established, allowing them to rotate about the central axis S and preventing movement in other directions. The planetary gear 91D is supported by the gear carrier 91A, allowing it to rotate about its central axis Sp, and preventing movement in other directions. Planetary gear 91D revolves around the central axis S of gear carrier 91A while rotating on its own axis Sp.

[0174] like Figure 22 As shown, the planetary gear mechanism 91 is constrained by the meshing of the sun gear 91B, ring gear 91C, and planetary gear 91D. Furthermore, to ensure gear strength, the diameter of planetary gear 91D needs to be increased. In other words, the planetary gear mechanism 91 is constrained by the meshing radius rs of the sun gear 91B being significantly smaller than the meshing radius rr of the ring gear 91C. In Table 5, “No. 2-A”, the gear carrier 91A is connected to the first connecting member 30, which is connected to the engine 9 (power source). Therefore, the torque Tc of the gear carrier 91A is the torque that the engine 9 can generate. The sun gear 91B is connected to the second connecting member 31, which is connected to the first transmission 33. Therefore, the torque Ts of the sun gear 91B is the torque that the first transmission 33 can generate. The ring gear 91C is connected to the third connecting member 32, which is connected to the inertial element 28. Therefore, the torque Tr of the ring gear 91C is the torque reaction force received from the first inertial gear 28B.

[0175] The ratio of the torque Ts of the sun gear 91B, the torque Tr of the ring gear 91C, and the torque Tc of the gear carrier 91A remains constant during power transmission in the planetary continuously variable transmission 24. Based on this rule, the controller 25 outputs a signal to control the first transmission 33, thereby controlling the torque of the second connecting member 31 (e.g., the sun gear 91B) connected to the first transmission 33. In other words, the controller 25 controls the torque of the second connecting member 31 (e.g., the sun gear 91B) by controlling the first transmission 33. Thus, the controller 25 indirectly controls the torque of the first connecting member 30 (e.g., the gear carrier 91A) connected to the engine 9 and the torque of the third connecting member 32 (e.g., the ring gear 91C) connected to the inertial element 28. As a result, it is possible to control the transmitted torque between the first connecting member 30 (e.g., the gear carrier 91A) connected to the engine 9 and the third connecting member 32 (e.g., the ring gear 91C) connected to the inertial element 28.

[0176] Figure 23 This describes the relationship between the rotational speeds of the planetary gear mechanism 91. Assume the rotational speed of the gear carrier 91A is constant. In this case, if the rotational speed of the ring gear 91C increases, the rotational speed of the sun gear 91B decreases. Conversely, if the rotational speed of the ring gear 91C decreases, the rotational speed of the sun gear 91B increases. Based on this rule, the controller 25 outputs a signal to control the first transmission 33, controlling the rotational speed of the second connecting member 31 (e.g., the sun gear 91B) connected to the first transmission 33. In other words, the controller 25 controls the rotational speed of the second connecting member 31 (e.g., the sun gear 91B) by controlling the first transmission 33. Thus, the controller 25 indirectly controls the rotational speeds of the first connecting member 30 (e.g., the gear carrier 91A) connected to the engine 9 and the third connecting member 32 (e.g., the ring gear 91C) connected to the inertial element 28. The result is that the gear ratio can be controlled between the first connecting member 30 (e.g., gear carrier 91A) connected to the engine 9 and the third connecting member 32 (e.g., ring gear 91C) connected to the inertial element 28.

[0177] In addition, such as Figure 24 As shown in the sixth variation (No. 2-B of Table 5), the planetary gear mechanism 91 can also be configured such that the ring gear 91C is connected to the first connecting member 30, which is connected to the engine 9; the gear carrier 91A is connected to the second connecting member 31, which is connected to the first transmission 33; and the sun gear 91B is connected to the third connecting member 32, which is connected to the inertial element 28. Additionally, as... Figure 25As shown in the seventh variation (No. 2-C of Table 5), the planetary gear mechanism 91 can also be configured such that the gear carrier 91A is connected to the first connecting member 30, the ring gear 91C is connected to the second connecting member 31, and the sun gear 91B is connected to the third connecting member 32. Furthermore, although the illustration is omitted, the planetary gear mechanism 91 can also be configured such that the gear carrier 91A, the sun gear 91B, and the ring gear 91C are connected 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.

[0178] The second embodiment includes a planetary gear mechanism 91 as described above, and its basic function is not significantly different from that described in the first embodiment. That is, similarly to the first embodiment, when switching from forward rotation mode to reverse rotation mode, with the output shaft 23 rotating in the forward direction (forward state), the switching between the forward 1st speed clutch 69 (first output clutch) and the reverse 1st speed clutch 70 (second output clutch) begins. Conversely, when switching from reverse rotation mode to forward rotation mode, with the output shaft 23 rotating in the reverse direction (reverse state), the switching between the reverse 1st speed clutch 70 (second output clutch) and the forward 1st speed clutch 69 (first output clutch) begins. Therefore, the switching between forward and reverse rotation of the output shaft 23 can be performed smoothly, and thus, the forward and reverse switching of the wheel loader 1 can be performed smoothly.

[0179] Furthermore, in the first embodiment, the second transmission 34 is connected to an inertial element 28 (specifically, an inertial shaft 28A of a rotating element) located between the planetary gear mechanism 29 and the multi-stage transmission mechanism 26. In contrast, although not shown in the figures, the second transmission 34 may also be configured to connect to a rotating element located between the input shaft 22 (input component) and the power source (engine 9), a rotating element constituting the multi-stage transmission mechanism 26, a rotating element located between the multi-stage transmission mechanism 26 and the output shaft 23 (output component), the output shaft 23 (output component), or a rotating element located between the output shaft 23 and the driving device (front axle 12, rear axle 13).

[0180] In other words, in the first embodiment, the second transmission 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 34 is configured to be connected between the planetary gear mechanism 29 and the output shaft 23. Alternatively, for example, the second transmission 34 may be connected to the input gear 27A of the direct coupling mechanism 27 provided on the input shaft 22 (input member). That is, the second transmission 34 may also be connected between the planetary gear mechanism 29 and the input shaft 22 (input member). Thus, the second transmission 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, for example, the second transmission 34 may also be connected to the locking gear 27B of the direct coupling mechanism 27. For example, the second transmission 34 may be connected to the third connecting member 32. For example, the second transmission 34 may be connected to the first idler gear 28B of the idler element 28. The second transmission 34 may be connected to the second idler gear 28C of the idler element 28.

[0181] For example, the second transmission 34 can be connected to the high gear 74 of the multi-stage transmission mechanism 26. For example, the second transmission 34 can be connected to the low gear 68 of the multi-stage transmission mechanism 26. For example, the second transmission 34 can be connected to the high output gear 79 of the multi-stage transmission mechanism 26. For example, the second transmission 34 can be connected to the low output gear 78 of the multi-stage transmission mechanism 26. For example, the second transmission 34 can 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 34 can be connected to a position closer to the load side (front axle 12 side, rear axle 13 side) than the output shaft 23 of the transmission device 21. For example, the second transmission 34 can be connected to the front axle 12, rear axle 13, front drive shaft 14, or rear drive shaft 15. These conditions also apply to the second embodiment and its variations.

[0182] In the first embodiment, a planetary gear mechanism 29 is described as an example of the planetary mechanism constituting the planetary continuously variable transmission 24. That is, in the first embodiment, the case where the planetary component of the planetary mechanism is composed of planetary gears is described as an example. However, it is not limited to this, and the planetary component of the planetary mechanism may also be composed of components other than gears, such as planetary rollers. This is also the case for the second embodiment and various modifications.

[0183] In the first embodiment, a transmission device 21 having a multi-stage transmission mechanism 26 and a direct-drive mechanism 27 is described as an example. However, it is not limited to this; the multi-stage transmission mechanism 26 and / or the direct-drive mechanism 27 may be omitted from the transmission device 21 as needed. Furthermore, in the first embodiment, an inertial element 28 is provided on the output side of the planetary continuously variable transmission mechanism 24; that is, the output side of the planetary continuously variable transmission mechanism 24 is the inertial element 28. However, the inertial element 28 may be omitted. That is, the output side of the planetary continuously variable transmission mechanism (e.g., the third component of the planetary mechanism, or the third connecting component) may be connected to the multi-stage transmission mechanism without via an inertial element. In any case, the multi-stage transmission mechanism is connected to the output side of the planetary continuously variable transmission mechanism (e.g., the third component of the planetary mechanism, the third connecting component, or the inertial element). Furthermore, the first output clutch of the multi-stage transmission mechanism is located in the first output transmission path where the gear between the output side of the planetary continuously variable transmission mechanism and the output shaft (the output shaft of the multi-stage transmission mechanism) engages an odd number of times. Additionally, the second output clutch of the multi-stage transmission mechanism is located in the second output transmission path where the gear between the output side of the planetary continuously variable transmission mechanism and the output shaft (the output shaft of the multi-stage transmission mechanism) engages zero or an even number of times. These conditions apply to both the second embodiment and its variations.

[0184] In the first embodiment, the case where the transmission device 21 is mounted on a wheel loader 1 is described as an example. However, it is not limited to this; the transmission device 21 can also be mounted on work vehicles (construction machinery) other than wheel loaders, such as hydraulic excavators, hydraulic cranes, dump trucks, and forklifts. Furthermore, it is not limited to work vehicles and can be widely used as a transmission device for various vehicles such as automobiles and rail vehicles, or various industrial and general machinery. This also applies to the second embodiment and its variations.

[0185] Furthermore, the above-described embodiments and modifications are illustrative, and of course, partial substitutions or combinations of the structures shown in different embodiments and modifications are also possible. Explanation of reference numerals in the attached figures

[0186] 1. Wheel loader (vehicle) 9. Engine (Power Source) 12. Front axle (running mechanism) 13. Rear axle (running device) 21. Speed ​​Transmission 22 Input axis (input component) Output shafts (output components) 23, 23A, 23B, and 77 24. Planetary continuously variable transmission (CVT) 25 Controllers 26. Multi-stage transmission mechanism (secondary transmission mechanism) 28 Inert elements 29. Planetary gear mechanism (planetary mechanism) 29A Gear Carrier (Part 1, Part 2, or Part 3) 29B First Sun Gear (Part 1, Part 2, or Part 3) 29C Second Sun Gear (Part 1, Part 2, or Part 3) 33. First hydraulic pump motor (first gearbox) 34. Second hydraulic pump motor (second gearbox) 35A Main Road No. 1 (Main Road) 35B Main Road 2 (Main Road) 38A First Variable Relief Valve (Relief Valve) 69 Forward 1st Speed ​​Clutch (First Output Clutch) 70 Reverse 1st speed clutch (2nd output clutch) 91 Planetary gear mechanism (planetary mechanism) 91A Gear Carrier (Part 1, Part 2, or Part 3) 91B Sun Gear (Part 1, Part 2, or Part 3) 91C Ring Gear (Part 1, Part 2, or Part 3).

Claims

1. A variable speed device having: an input shaft that rotates by a power source mounted on a vehicle; an output shaft that outputs rotation to a traveling device of the vehicle; a planetary continuously variable transmission mechanism provided between the input shaft and the output shaft, which steps up rotation on the input shaft side and transmits to the output shaft side; and a multi-stage transmission mechanism that steps up rotation on the output side of the planetary continuously variable transmission mechanism by switching transmission paths of meshing of gears, the planetary continuously variable transmission mechanism having: a planetary mechanism having three members of a first member connected to the input shaft side, a second member that becomes an output side, and a third member that becomes another output side different from the second member; a first transmission connected to the second member of the planetary mechanism; and a second transmission capable of power transmission between the first transmission, the multi-stage transmission mechanism having: a first output clutch provided in a first output transmission path in which the number of meshing of gears between the output side of the planetary continuously variable transmission mechanism and the output shaft is odd, which switches transmission and release of power of the first output transmission path; and a second output clutch provided in a second output transmission path in which the number of meshing of gears between the output side of the planetary continuously variable transmission mechanism and the output shaft is zero or even, which switches transmission and release of power of the second output transmission path, the variable speed device characterized by: a controller that controls engagement and release of the first output clutch and engagement and release of the second output clutch, the controller being capable of reversing a traveling direction of the vehicle by switching a forward rotation mode in which the first output clutch is engaged and the second output clutch is released, and a reverse rotation mode in which the first output clutch is released and the second output clutch is engaged, the controller starting switching of the first output clutch from an engaged state to a released state and starting switching of the second output clutch from a released state to an engaged state in a state in which rotation of the output shaft is forward rotation, and reversing a rotation direction of the third member by changing a rotation speed of the first transmission when switching from the forward rotation mode to the reverse rotation mode.

2. A variable speed device having: an input shaft that rotates by a power source mounted on a vehicle; an output shaft that outputs rotation to a traveling device of the vehicle; a planetary continuously variable transmission mechanism provided between the input shaft and the output shaft, which steps up rotation on the input shaft side and transmits to the output shaft side; and a multi-stage transmission mechanism that steps up rotation on the output side of the planetary continuously variable transmission mechanism by switching transmission paths of meshing of gears, the planetary continuously variable transmission mechanism having: a planetary mechanism having three members of a first member connected to the input shaft side, a second member that becomes an output side, and a third member that becomes another output side different from the second member; a first transmission connected to the second member of the planetary mechanism; and a second transmission capable of power transmission between the first transmission, the multi-stage transmission mechanism having: a first output clutch provided in a first output transmission path in which the number of meshing of gears between the output side of the planetary continuously variable transmission mechanism and the output shaft is odd, which switches transmission and release of power of the first output transmission path; and a second output clutch provided in a second output transmission path in which the number of meshing of gears between the output side of the planetary continuously variable transmission mechanism and the output shaft is zero or even, which switches transmission and release of power of the second output transmission path, the variable speed device characterized by: a controller that controls engagement and release of the first output clutch and engagement and release of the second output clutch, the controller being capable of reversing a traveling direction of the vehicle by switching a forward rotation mode in which the first output clutch is engaged and the second output clutch is released, and a reverse rotation mode in which the first output clutch is released and the second output clutch is engaged, the controller starting switching of the first output clutch from an engaged state to a released state and starting switching of the second output clutch from a released state to an engaged state in a state in which rotation of the output shaft is forward rotation, and reversing a rotation direction of the third member by changing a rotation speed of the first transmission when switching from the forward rotation mode to the reverse rotation mode. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ a second transmission capable of power transmission between the first transmission and the first output clutch, the multi-stage transmission mechanism has: a first output clutch provided in a first output transmission path in which the number of meshing of gears between the output side of the planetary continuously variable transmission mechanism and the output shaft is an odd number, and switching power transmission and release of the first output transmission path; and a second output clutch provided in a second output transmission path in which the number of meshing of gears between the output side of the planetary continuously variable transmission mechanism and the output shaft is zero or an even number, and switching power transmission and release of the second output transmission path, the transmission device is characterized by having a controller that controls engagement and release of the first output clutch and engagement and release of the second output clutch, the controller is capable of reversing the traveling direction of the vehicle by switching a forward rotation mode in which the first output clutch is engaged and the second output clutch is released, and a reverse rotation mode in which the first output clutch is released and the second output clutch is engaged, at the time of switching from the reverse rotation mode to the forward rotation mode, the controller starts switching of the second output clutch from the engaged state to the released state, and starts switching of the first output clutch from the released state to the engaged state, in a state in which the rotation of the output shaft is reversed, and reverses the rotation direction of the third member by changing the rotation speed of the first transmission.

3. The transmission device according to claim 1, characterized in that the first transmission is a hydraulic pump, the second transmission is a hydraulic motor, the hydraulic pump and the hydraulic motor are connected by a pair of main lines, the pair of main lines enables power transmission between the hydraulic pump and the hydraulic motor, between the pair of main lines, a relief valve for controlling the main lines to be in a communication state and a cutoff state is provided, the controller is capable of changing the communication start pressure of the relief valve, at the time of switching from the forward rotation mode to the reverse rotation mode, the controller decreases the set value of the communication start pressure of the relief valve before the start of switching of the first output clutch and the start of switching of the second output clutch.

4. The transmission device according to claim 2, characterized in that the first transmission is a hydraulic pump, the second transmission is a hydraulic motor, the hydraulic pump and the hydraulic motor are connected by a pair of main lines, the pair of main lines enables power transmission between the hydraulic pump and the hydraulic motor, between the pair of main lines, a relief valve for controlling the main lines to be in a communication state and a cutoff state is provided, the controller is capable of changing the communication start pressure of the relief valve, at the time of switching from the reverse rotation mode to the forward rotation mode, the controller decreases the set value of the communication start pressure of the relief valve before the start of switching of the second output clutch and the start of switching of the first output clutch.

5. The transmission device according to claim 1, characterized in that, The first transmission is a hydraulic pump, The second transmission is a hydraulic motor, The hydraulic pump and the hydraulic motor are connected by a pair of main pipes, The pair of main pipes enables power transmission between the hydraulic pump and the hydraulic motor, Between the pair of main pipes, there is an overflow valve for controlling the pair of main pipes to be in communication or cutoff, The controller can change the communication start pressure of the overflow valve, When switching from the forward rotation mode to the reverse rotation mode, The controller increases the set value of the communication start pressure of the overflow valve while the first output clutch is being switched from the engaged state to the released state and the second output clutch is being switched from the released state to the engaged state.

6. The transmission device according to claim 2, wherein The first transmission is a hydraulic pump, The second transmission is a hydraulic motor, The hydraulic pump and the hydraulic motor are connected by a pair of main pipes, The pair of main pipes enables power transmission between the hydraulic pump and the hydraulic motor, Between the pair of main pipes, there is an overflow valve for controlling the pair of main pipes to be in communication or cutoff, The controller can change the communication start pressure of the overflow valve, When switching from the reverse rotation mode to the forward rotation mode, The controller increases the set value of the communication start pressure of the overflow valve while the second output clutch is being switched from the engaged state to the released state and the first output clutch is being switched from the released state to the engaged state.

7. The transmission device according to claim 1, wherein The first transmission is a hydraulic pump, The second transmission is a hydraulic motor, The hydraulic pump and the hydraulic motor are connected by a pair of main pipes, The pair of main pipes enables power transmission between the hydraulic pump and the hydraulic motor, Between the pair of main pipes, there is an overflow valve for controlling the pair of main pipes to be in communication or cutoff, The controller can change the communication start pressure of the overflow valve, When switching from the forward rotation mode to the reverse rotation mode, The controller sets a time during which the overflow valve is in communication by changing the rotational speed of the first transmission to reverse the rotational direction of the third member.

8. The transmission device according to claim 2, wherein The first transmission is a hydraulic pump, The second transmission is a hydraulic motor, The hydraulic pump and the hydraulic motor are connected by a pair of main pipes, The pair of main pipes enables power transmission between the hydraulic pump and the hydraulic motor, Between the pair of main pipes, there is an overflow valve for controlling the pair of main pipes to be in communication or cutoff, The controller can change the communication start pressure of the overflow valve, When switching from the reverse rotation mode to the forward rotation mode, The controller sets a time during which the overflow valve is in communication by changing the rotational speed of the first transmission to reverse the rotational direction of the third member.

9. The transmission device according to claim 1, wherein the first transmission and the second transmission are each an electric motor, the first transmission and the second transmission are connected by an electric circuit, a motor control device is provided in the electric circuit, the first transmission and the second transmission are capable of power transmission via the electric circuit.

10. The transmission device according to claim 2, wherein the first transmission and the second transmission are each an electric motor, the first transmission and the second transmission are connected by an electric circuit, a motor control device is provided in the electric circuit, the first transmission and the second transmission are capable of power transmission via the electric circuit. ​ ​

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