Gearbox

Abstract

A transmission device (21) comprises an input shaft (22), an output shaft (23), a planetary gear mechanism (29), a first variator (33), a second variator (34), and a controller (25). The second variator (34) transfers, to the output shaft (23), power transferred from the first variator (33). A power absorption device (38) is provided between the second variator (34) and the first variator (33). When the controller (25) changes the absorption torque of the first variator (33) and generates an amount of power greater than or equal to that which can be absorbed by the second variator (34), the power absorption device (38) absorbs power and thereby increases the torque of the output shaft (23).

Description

[Technical field]

[0001] The present disclosure relates to a transmission device mounted on a vehicle such as a wheel loader or a wheeled hydraulic excavator. [Background technology]

[0002] For example, Patent Document 1 describes a power split transmission in which power generated by a prime mover (1) serving as a power source is transmitted to a compound planetary gear mechanism (13) via a floating gear (11), and the compound planetary gear mechanism (13) distributes (splits) the power in two directions. One of the powers split by the compound planetary gear mechanism (13) is transmitted to a drive section (23) serving as an output shaft or to the compound planetary gear mechanism (13) via a first stepless adjustment unit (18) and a second stepless adjustment unit (21). The other of the powers split by the compound planetary gear mechanism (13) is transmitted to the drive section (23) by the meshing of the gears. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2010-540866 Summary of the Invention

[0004] In the case of the technology described in Patent Document 1, in order to ensure a sufficient output torque of the drive part (23) serving as the output shaft, it is considered necessary to employ a second stepless adjustment unit (21) having a large maximum output torque and to compensate for the insufficient torque of the drive part (23). In this case, however, in addition to making the second stepless adjustment unit (21) expensive, there is a possibility that the second stepless adjustment unit (21) will become large in size.

[0005] An object of the present invention is to provide a transmission that can output sufficient torque even if it uses a small, inexpensive second continuously variable adjustment unit (second variator) with a small maximum output torque.

[0006] A continuously variable transmission according to an embodiment of the present invention includes an input member connected to a power source, an output member connected to a load, a planetary mechanism provided between the input member and the output member, and a planetary mechanism connected to the planetary mechanism. Consists of a hydraulic pump A first variator and a second variator provided separately from the first variator. Consists of a hydraulic motor A second variator; a pair of main lines connecting the first variator and the second variator to each other; and a controller for changing the rotation speed of the first variator, the planetary mechanism including a carrier, a first sun member that rotates about a rotational axis of the carrier, and a second sun member that rotates about a rotational axis of the carrier, a first member of the members constituting the planetary mechanism is connected to the input member directly or via another member, a second member different from the first member of the members constituting the planetary mechanism is connected to the first variator directly or via another member, and a third member different from the first member and the second member of the members constituting the planetary mechanism is connected to the output member directly or via another member. The planetary mechanism is connected to the first sun member and the second sun member through a member, and a planet member and a balance member that transmit power while revolving around the rotational center axis of the carrier and rotating with the first sun member and the second sun member are supported on the carrier of the planetary mechanism, and the planetary mechanism is configured to be able to distribute torque transmitted from the power source to the planetary mechanism to the second member and the third member, and the second variator is configured to transmit the power transmitted from the first variator to the load or the power source, or to transmit the power transmitted from the load or the power source to the first variator, and absorbs power between the second variator and the first variator. It consists of two accumulators A power absorption device is provided, The two accumulators include a first accumulator that absorbs power and a second accumulator that supplies hydraulic oil to the first accumulator, and the first accumulator and the second accumulator are connected to the pair of main lines via a switching valve that communicates with or blocks communication with the pair of main lines; The controller changes the rotation speed of the first variator to change the rotation speed of the output member relative to the rotation speed of the input member, and changes the absorption torque of the first variator. When power greater than or equal to that which can be absorbed by the second variator is generated, the power absorbing device The pressure accumulation in the first accumulator is By absorbing the power by the torque converter, the torque of the output member is increased.

[0007] A continuously variable transmission according to an embodiment of the present invention includes an input member connected to a power source, an output member connected to a load, a planetary mechanism provided between the input member and the output member, and a gear mechanism connected to the planetary mechanism. Consists of a hydraulic pump A first variator and a second variator provided separately from the first variator. Consists of a hydraulic motor A second variator; a pair of main lines connecting the first variator and the second variator to each other; and a controller that changes the rotation speed of the first variator, the planetary mechanism including three members: a carrier, a sun member that rotates about a rotational axis of the carrier, and a ring member that is located radially outward of the sun member and rotates about the rotational axis of the carrier, a first member of the three members of the planetary mechanism is connected to the input member directly or via another member, a second member different from the first member of the three members of the planetary mechanism is connected to the first variator directly or via another member, and is different from the first member and the second member of the three members of the planetary mechanism. a third member connected directly to the output member or via another member; a planet member that transmits power while revolving around the central axis of rotation of the carrier and rotating with the sun member and the ring member is supported on the carrier of the planetary mechanism; the planetary mechanism is configured to be able to distribute torque transmitted from the power source to the second member and the third member; the second variator is configured to transmit the power transmitted from the first variator to the load or the power source, or to transmit the power transmitted from the load or the power source to the first variator, and absorbs power between the second variator and the first variator. It consists of two accumulators A power absorption device is provided, The two accumulators include a first accumulator that absorbs power and a second accumulator that supplies hydraulic oil to the first accumulator, and the first accumulator and the second accumulator are connected to the pair of main lines via a switching valve that communicates with or blocks communication with the pair of main lines; The controller changes the rotation speed of the first variator to change the rotation speed of the output member relative to the rotation speed of the input member, and changes the absorption torque of the first variator. When power greater than or equal to that which can be absorbed by the second variator is generated, the power absorbing device The pressure accumulation in the first accumulator is By absorbing the power by the torque converter, the torque of the output member is increased.

[0008] According to one embodiment of the present invention, even a small, inexpensive second variator with a small maximum output torque can output sufficient torque. [Brief description of the drawings]

[0009] [Figure 1] 1 is a left side view showing a wheel loader equipped with a transmission according to a first embodiment. [Diagram 2] 2 is a partially cutaway side view showing the transmission in FIG. 1. [Diagram 3] FIG. 1 is a configuration diagram showing a transmission according to a first embodiment. [Figure 4] FIG. 4 is a configuration diagram showing the transmission in FIG. 3 together with the inside of the planetary mechanism. [Diagram 5] FIG. 5 is an enlarged view of part (A) in FIG. [Figure 6] 5 is an explanatory diagram of the planetary mechanism in FIG. 4 as viewed from the power source side. [Figure 7] FIG. 5 is a characteristic diagram showing the relationship between the rotation speeds of the members of the planetary mechanism ("No. 1-A" in Table 4 described later) in FIG. [Figure 8] This is a characteristic diagram showing the relationship between the rotational speeds of each member of the planetary mechanism of "No. 1-B" in Table 4 described later. [Figure 9] This is a characteristic diagram showing the relationship between the rotational speeds of each member of the planetary mechanism of "No1-C" in Table 4 described later. [Figure 10] FIG. 4 is a characteristic diagram showing the relationship between speed ratio and torque. [Figure 11] FIG. 2 is a configuration diagram showing an example of a power absorption device in which the variator is an electric motor / generator. [Figure 12] FIG. 1 is a configuration diagram showing an example of a power absorption device in which a variator is a hydraulic pump / motor. [Figure 13] 4 is a characteristic diagram showing an example of changes in pressure and volume over time when the relief start pressure of the relief valve is fixed. [Figure 14] 5 is a characteristic diagram showing an example of changes in pressure and volume over time in a case where the relief start pressure of the relief valve is variable. FIG. [Figure 15]FIG. 11 is a configuration diagram showing another example of a power absorption device in which the variator is a hydraulic pump / motor. [Figure 16] FIG. 5 is an enlarged view of part (B) in FIG. [Figure 17] FIG. 4 is a driving force diagram showing an ideal relationship between vehicle speed and tractive force of a wheel loader. [Figure 18] FIG. 3 is a driving force diagram showing the relationship between vehicle speed and tractive force of the wheel loader according to the first embodiment. [Figure 19] FIG. 4 is a configuration diagram similar to FIG. 3, showing a first modified example (configuration without external lockup). [Figure 20] FIG. 4 is a configuration diagram similar to FIG. 3, but showing a second modified example (configuration in which internal lockup is performed by braking). [Figure 21] FIG. 5 is a diagram similar to FIG. 3, but showing a third modified example (a configuration in which internal lockup is performed by a brake and no idler member is used). [Figure 22] FIG. 4 is a driving force diagram showing the relationship between vehicle speed and tractive force of a wheel loader equipped with a transmission without external lockup. [Diagram 23] FIG. 1 is a driving force diagram showing the relationship between vehicle speed and tractive force of a wheel loader equipped with a transmission without internal lockup. [Figure 24] FIG. 5 is a configuration diagram similar to FIG. 4, but showing a fourth modified example (a configuration in which the input member is connected to the first sun member, and the first variator is connected to the carrier). [Diagram 25] FIG. 5 is a configuration diagram similar to FIG. 4, showing a fifth modified example (configuration in which the input member is connected to the first sun member, and the first variator is connected to the second sun member). [Figure 26] FIG. 5 is a configuration diagram similar to FIG. 4, showing a sixth modified example (configuration in which the second variator is connected to the output member). [Figure 27] FIG. 5 is a configuration diagram similar to FIG. 4 showing the second embodiment. [Figure 28] FIG. 28 is an enlarged view of part (C) in FIG. [Figure 29] FIG. 28 is an explanatory diagram of the planetary mechanism in FIG. 27 as viewed from the power source side. [Diagram 30]FIG. 28 is a characteristic diagram showing the relationship between the rotation speeds of three members of the planetary mechanism in FIG. 27 ("No. 2-A" in Table 6 described later). [Diagram 31] This is a characteristic diagram showing the relationship between the rotational speeds of each member of the planetary mechanism of "No. 2-B" in Table 6 described later. [Diagram 32] This is a characteristic diagram showing the relationship between the rotational speeds of each member of the planetary mechanism of "No2-C" in Table 6 described later. [Diagram 33] This is a characteristic diagram showing the relationship between the rotational speeds of each member of the planetary mechanism of "No2-D" in Table 6 described later. [Diagram 34] This is a characteristic diagram showing the relationship between the rotational speeds of each member of the planetary mechanism of "No. 2-E" in Table 6 described later. [Diagram 35] This is a characteristic diagram showing the relationship between the rotational speeds of each member of the planetary mechanism of "No2-F" in Table 6 described later. [Diagram 36] FIG. 28 is a configuration diagram similar to FIG. 27, showing a seventh modified example (a configuration in which the input member is connected to the ring member, and the first variator is connected to the carrier). [Figure 37] FIG. 28 is a configuration diagram similar to FIG. 27, showing an eighth modified example (a configuration in which the input member is connected to the carrier, and the first variator is connected to the ring member). [Figure 38] FIG. 28 is a configuration diagram similar to FIG. 27, showing a ninth modified example (a configuration in which the input member is connected to the ring member, and the first variator is connected to the sun member). [Figure 39] FIG. 28 is a configuration diagram similar to FIG. 27, showing a tenth modified example (a configuration in which the input member is connected to the sun member, and the first variator is connected to the ring member). [Diagram 40] FIG. 28 is a configuration diagram similar to FIG. 27, showing an eleventh modified example (a configuration in which the input member is connected to the sun member, and the first variator is connected to the carrier). [Diagram 41] FIG. 16 is a configuration diagram similar to FIG. 3, showing a twelfth modified example (a configuration in which a second variator is connected to an input member). [Diagram 42] FIG. 14 is a configuration diagram similar to FIG. 3, but showing a thirteenth modified example (a configuration in which the second variator is connected to a third connecting member that is linked to an idler element). [Diagram 43]FIG. 23 is a configuration diagram similar to FIG. 3, but showing a fourteenth modified example (a configuration in which the second variator is connected to odd-numbered gears of a multi-speed mechanism). [Diagram 44] FIG. 15 is a configuration diagram similar to FIG. 3, but showing a fifteenth modified example (configuration in which the second variator is connected to a first forward gear of the multi-speed mechanism). [Diagram 45] FIG. 17 is a configuration diagram similar to FIG. 3, but showing a sixteenth modified example (a configuration in which the second variator is connected to a third forward gear of a multi-speed mechanism). [Diagram 46] FIG. 17 is a configuration diagram similar to FIG. 3, but showing a seventeenth modified example (a configuration in which the second variator is connected to a second forward gear of a multi-speed mechanism). [Figure 47] FIG. 19 is a configuration diagram similar to FIG. 3, but showing an eighteenth modified example (a configuration in which the second variator is connected to a fourth forward gear of a multi-speed mechanism). [Figure 48] FIG. 19 is a configuration diagram similar to FIG. 3, but showing a nineteenth modified example (a configuration in which the second variator is connected to a first reverse gear of a multi-speed mechanism). [Figure 49] FIG. 13 is a configuration diagram similar to FIG. 3, showing a twentieth modified example (configuration in which the second variator is connected to the output member). [Figure 50] FIG. 13 is a diagram similar to FIG. 3, showing a twenty-first modified example (a configuration in which the second variator is connected closer to the load side than the output member of the transmission). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A speed change device (transmission) according to an embodiment will be described in detail below with reference to the accompanying drawings, taking as an example a case in which the speed change device (transmission) is applied to a wheel loader.

[0011] FIG. 1 to FIG. 18 show a first embodiment. In FIG. 1, a wheel loader 1 is a representative example of a vehicle (work vehicle). The wheel loader 1 is configured as an articulated work vehicle in which a front body 3 provided with left and right front wheels 2 and a rear body 5 provided with left and right rear wheels 4 are connected so as to be able to bend left and right. That is, the front body 3 and the rear body 5 configure the body of the wheel loader 1. A center 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 center hinge 6 by extending and retracting the steering cylinder. This allows the wheel loader 1 to be steered when traveling.

[0012] A loading / unloading machine 7, also called a working device, is provided on the front body 3 of the wheel loader 1 so as to be capable of lifting and lowering. The loading / unloading machine 7 is equipped with a loader bucket 7A. Meanwhile, a cab 8 with a driver's cab inside, an engine 9, a hydraulic pump 10, a speed change device 21 which is a transmission (power transmission device), and the like are provided on the rear body 5 of the wheel loader 1. The engine 9 is the power source (prime mover) of the wheel loader 1. The power source can be constituted by the engine 9 alone which is an internal combustion engine, or may be constituted by, for example, an engine and an electric motor, or an electric motor alone. The hydraulic pump 10 is connected to the engine 9. The hydraulic pump 10 is a hydraulic pressure source for operating the loading / unloading machine 7. As shown in FIG. 3 etc. described later, the hydraulic pump 10 is connected to the engine 9 via gears 10A and 10B.

[0013] A front axle 12 extending left and right is provided below the front vehicle body 3. Left and right front wheels 2 are attached to both ends of the front axle 12. Meanwhile, a rear axle 13 extending left and right is provided below the rear vehicle body 5. Left and right rear wheels 4 are attached to both ends of the rear axle 13.

[0014] The front axle 12 is connected to the transmission 21 via a front propeller shaft 14. The rear axle 13 is connected to the transmission 21 via a rear propeller shaft 15. The transmission 21 accelerates and decelerates the rotation of the engine 9 and transmits it to the front propeller shaft 14 and the rear propeller shaft 15. That is, the power from the engine 9 is transmitted to the transmission 21 coupled to the engine 9.

[0015] Power from the engine 9 has its rotation speed and direction adjusted by the transmission 21, and is then transmitted from front and rear output shafts 23A, 23B of the transmission 21 to the front axle 12 and the rear axle 13 via the front propeller shaft 14 and the rear propeller shaft 15. That is, as shown in Fig. 2, the transmission 21 includes an input shaft 22 connected to the engine 9, a front output shaft 23A connected to the front propeller shaft 14, and a rear output shaft 23B connected to the rear propeller shaft 15. The transmission 21 changes speed and switches between forward and reverse rotation between the input shaft 22 and the output shafts 23A, 23B by switching the power transmission path within the transmission 21.

[0016] Next, the operation of the wheel loader 1 will be described. The wheel loader 1 repeats operation patterns such as a V-cycle, which is mainly used for dump loading work, and a load & carry, which directly dumps the material into a hopper, etc. The V-cycle is an operation pattern in which after starting, soil and sand are excavated and loaded into a dump truck. The load & carry is an operation pattern in which after starting, soil and sand are excavated, transported (high load traveling), unloaded into a dump truck, and then sent off (low load traveling). The wheel loader 1 needs to frequently switch the transmission 21 to obtain optimal travel speed and driving force for various work conditions such as starting, excavation, transport, loading, and sending off.

[0017] During excavation and starting, the transmission 21 is required to provide high traction force. For this reason, the transmission 21 needs to increase the reduction ratio to increase the output torque of the output shafts 23A, 23B. Furthermore, even when the vehicle speed of the wheel loader 1 is 0 km / h (the rotational speed of the output shafts 23A, 23B is 0), the rotational speed of the input shaft 22 needs to be kept at a predetermined value or higher so that the engine 9, which is the power source, does not stop, and the transmission 21 needs to be structured so that the speed ratio is infinite. The vehicle speed of the wheel loader 1 during excavation is, for example, 0 to 4 km / h.

[0018] During transportation, the transmission 21 needs to transmit power from the input shaft 22 to the output shafts 23A, 23B with high transmission efficiency to save fuel. The vehicle speed during transportation is, for example, 0 to 13 km / h. On the other hand, when discharging soil to a dump truck, the wheel loader 1 raises the loading and unloading machine 7 while transporting the vehicle. Therefore, if the lifting speed of the loading and unloading machine 7 suddenly slows down, there is a possibility that the loading and unloading machine 7 will collide with the dump truck. Therefore, when approaching the dump truck, it is desirable to be able to suppress a sudden change in the discharge flow rate of the hydraulic pump 10. And, for this purpose, it is necessary to control the transmission 21 so that the rotation speed of the engine 9 does not change suddenly. When discharging soil to the dump truck, the vehicle speed for approaching the dump truck is, for example, 0 to 7 km / h. At this vehicle speed, it is desirable to be able to suppress a sudden change in the rotation speed of the engine 9.

[0019] When the vehicle is traveling unladen on a general road or within a work site, the transmission 21 needs to transmit power from the input shaft 22 to the output shafts 23A, 23B with high transmission efficiency in order to save fuel. The vehicle speed during transportation is, for example, 0 to 40 km / h. When the vehicle is being transported, high operability of the loading and unloading machine 7 is not required. For this reason, a sudden change in the rotation speed of the engine 9 is acceptable. However, in order to save fuel, it is necessary to transmit power from the input shaft 22 to the output shafts 23A, 23B with a higher transmission efficiency than during transportation.

[0020] FIG. 17 shows an ideal driving force diagram for the wheel loader 1. FIG. 17 shows an ideal driving force line Lf in the forward direction and an ideal driving force line Lr in the reverse direction (reverse direction). When moving forward, high traction force is required for excavation, and high vehicle speed (0 to 40 km / h) is required for driving. The wheel loader 1 also needs to be able to stably climb uphill slopes with various gradients that are provided in quarries and the like. For this reason, for example, at speeds of 3 km / h or more, it is desirable for the traction force to be equal in horsepower regardless of vehicle speed.

[0021] Range A in Fig. 17 indicates the range where high tractive force is required for excavation, i.e., range A of the driving force line during excavation. Range B in Fig. 17 indicates the range where a constant horsepower tractive force is required regardless of the vehicle speed, i.e., range B of the driving force line of constant horsepower in the forward direction. Range C in Fig. 17 indicates the range where a constant horsepower tractive force is required regardless of the vehicle speed, i.e., range C of the driving force line of constant horsepower in the reverse direction. The following formula 1 holds for range B of the driving force line of constant horsepower in the forward direction and range C of the driving force line of constant horsepower in the reverse direction.

[0022]

number

[0023] It should be noted that the wheel loader 1 does not excavate in the reverse direction. For this reason, the maximum traction force of the ideal driving force line Lr in the reverse direction is lower than that during forward travel.

[0024] Incidentally, it is preferable that the transmission 21 used in a work vehicle such as the wheel loader 1 is capable of switching between power transmission by a continuously variable transmission mechanism and power transmission by a lock-up mechanism. In this case, it is preferable that the transmission 21 can effectively use the speed-change range of the continuously variable transmission mechanism for speed increase. In addition, it is preferable that the change in acceleration / deceleration of the vehicle can be reduced when switching from power transmission by the continuously variable transmission mechanism to power transmission by the lock-up mechanism. Also, when the upper limit of the rotational speed of the variator and the upper limit of the torque that can be generated (absorbed) are limited, it is preferable to provide an arrangement (gear arrangement) that optimizes the speed ratio (gear ratio) of the planetary mechanism (planetary gear mechanism) and improve the transmission efficiency of the continuously variable transmission mechanism.

[0025] Furthermore, the aforementioned Patent Document 1 describes a power split transmission in which power generated by a prime mover (1) serving as a power source is transmitted to a compound planetary gear mechanism (13) via a floating gear (11), and the compound planetary gear mechanism (13) distributes (splits) the power in two directions. One of the powers split by the compound planetary gear mechanism (13) is transmitted to a drive section (23) serving as an output shaft or to the compound planetary gear mechanism (13) via a first stepless adjustment unit (18) and a second stepless adjustment unit (21). The other of the powers split by the compound planetary gear mechanism (13) is transmitted to the drive section (23) by the meshing of the gears.

[0026] In the transmission of Patent Document 1, in the first driving range, either the clutch (4) or the clutch (8) is engaged and the other is released, while the clutch (26) is engaged and the clutch (29) is released. The first driving range is a power transmission connection state from when the vehicle starts to when it accelerates, and corresponds to a range of about 0 to 20 km / h in forward and reverse driving. According to Patent Document 1, in this state, the power generated by the prime mover (1) serving as the power source is divided to the first stepless adjustment unit (18) and the ring gear (15) via the compound planetary gear mechanism (13). The power transmitted to the first stepless adjustment unit (18) is transmitted to the drive section (23) serving as the output shaft via the second stepless adjustment unit (21), and is transmitted to the drive section (23) by the meshing of the gears transmitted to the ring gear (15). The first stepless adjustment unit (18) and the second stepless adjustment unit (21) are hydraulic pump-motors, and can transmit power between them while varying the speed steplessly.

[0027] In the first driving region, the torque generated by the prime mover (1) is transmitted at a constant ratio to the first infinitely variable adjustment unit (18) and the ring gear (15) by the compound planetary gear mechanism (13). The torque transmission ratio is determined by the gear tooth ratio of the first sun gear (16) and the ring gear (15) of the compound planetary gear mechanism (13) and the double planetary gear mechanism (14). As a result, the following formulas 2, 3, and 4 are established.

[0028]

number

[0029]

number

[0030]

number

[0031] Therefore, in order to increase the output torque of the drive part (23), it is necessary to increase the torque of the ring gear (15) by increasing the load torque of the first stepless adjustment unit (18). However, the first stepless adjustment unit (18) cannot transmit more power than the second stepless adjustment unit (21) can withstand, so the load torque of the first stepless adjustment unit (18) is limited. This causes a problem that the torque of the drive part (23), which serves as the output shaft, decreases as the torque of the ring gear (15) decreases. This problem occurs when the vehicle is traveling at a low vehicle speed, where the second stepless adjustment unit (21) can only withstand a small amount of power due to its slow rotation speed.

[0032] Here, since a wheel loader is a vehicle that performs excavation and loading, it is necessary to increase the torque of the drive unit (23) that serves as the output shaft when the vehicle speed is low. For this reason, if the transmission of Patent Document 1 is used in a wheel loader, there is a risk that the output torque of the drive unit (23) that serves as the output shaft will be insufficient during excavation. In order to solve this problem, for example, it is conceivable to employ a second stepless adjustment unit (21) that has a large maximum output torque to compensate for the torque deficiency of the drive unit (23) that serves as the output shaft. However, in this case, in addition to the second stepless adjustment unit (21) becoming expensive, the second stepless adjustment unit (21) may also become large in size.

[0033] 3 and 4, the transmission 21 according to the embodiment includes a planetary type continuously variable transmission mechanism 24. The planetary type continuously variable transmission mechanism 24 includes a planetary gear mechanism 29, a first variator 33, and a second variator 34. The first variator 33 absorbs more power than the second variator 34 can withstand, thereby increasing the torque of the terminal (first connecting member 30) connected to the first variator 33 and increasing the torque of the terminal (third connecting member 32) connected to the idler gear 28B, thereby increasing the torque of the output shaft 23 (23A, 23B). In this case, a power absorbing device 38 that absorbs power is provided between the first variator 33 and the second variator 34.

[0034] The power absorbing device 38 is a device that disposes of power (power disposal device) and / or a device that saves (stores) power (power saving device, power storage device, power storage source). The power absorbing device 38 absorbs (disposes of or stores) the power generated by the first variator 33 that is greater than the power that the second variator 34 can absorb. Hereinafter, control for absorbing (disposing of or storing) such power is referred to as torque boost control. In the embodiment, by enabling such torque boost control, even the second variator 34 that is small, inexpensive, and has a small maximum output torque can output sufficient torque from the output shaft 23 (23A, 23B) when traveling at a low vehicle speed. As a result, the tractive force required for excavation by the wheel loader 1 can be sufficiently increased, and excavation can be performed efficiently.

[0035] 3 and 4, the transmission 21 according to the first embodiment has a mode in which power is transmitted while the planetary continuously variable transmission mechanism 24 is continuously variable, a mode in which power is transmitted by internally locking up the planetary continuously variable transmission mechanism 24, and a mode in which power is transmitted by an external lockup mechanism (direct coupling mechanism 27) without passing through the planetary gear mechanism 29. Power transmission by internal lockup is performed by stopping the rotation of a rotating member (e.g., the first sun gear) connected to the first variator 33 among the three rotating members (e.g., the carrier, the first sun gear, and the second sun gear) of the planetary gear mechanism 29. This allows the speed-up range of the planetary continuously variable transmission mechanism 24 to be used effectively.

[0036] On the other hand, power transmission by external lockup is performed via an external lockup mechanism (direct drive mechanism 27) attached to the outside of planetary continuously variable transmission mechanism 24. In this case, power transmission by external lockup is performed in a state where power transmission by planetary continuously variable transmission mechanism 24 is stopped. This is performed by releasing (or reducing the torque of) a rotating member (e.g., the first sun gear) connected to first variator 33 out of three rotating members (e.g., the carrier, the first sun gear, and the second sun gear) of planetary gear mechanism 29. This makes it possible to transmit power with higher transmission efficiency than internal lockup, and also makes it possible to transmit power by further increasing the speed-up range of the planetary continuously variable transmission mechanism 24.

[0037] Furthermore, according to the first embodiment, as shown in Fig. 4 to Fig. 6, the planetary gear mechanism 29 includes two sun gears 29B, 29C, a planet gear 29D and a balance gear 29E that rotate but do not revolve around the central axis S (Fig. 6) of the two sun gears 29B, 29C, and one carrier 29A that rotatably supports the planet gear 29D and the balance gear 29E and rotates around the central axis S of the two sun gears 29B, 29C. This allows the planetary gear mechanism 29 to have a gear arrangement that optimizes the gear ratio. In other words, by using the planetary gear mechanism 29 with this arrangement, the transmission efficiency of the planetary type continuously variable transmission mechanism 24 can be improved even when using an inexpensive and small-sized first variator 33 with limited upper limits on the rotational speed and the torque that can be generated (absorbed).

[0038] The transmission 21 according to the first embodiment will be described in detail below. In FIG. 3, the planetary gear mechanism 29 of the transmission 21 is shown as a box, whereas FIG. 4 shows the inside of the planetary gear mechanism 29, i.e., the specific gear arrangement of the planetary gear mechanism 29. In addition, in FIG. 3 and FIG. 4, in order to avoid complicating the drawings, the output shaft 23 of the transmission 21 is simply shown as a common output shaft 23 (=output shafts 23A, 23B) that transmits power to both the front axle 12 and the rear axle 13. In other words, in FIG. 3 and FIG. 4, a configuration for splitting power to the front output shaft 23A and the rear output shaft 23B via, for example, a center differential mechanism or the like is omitted.

[0039] 3 and 4 are mechanical diagrams of a transmission 21 according to a first embodiment, more specifically, a transmission 21 having both an internal lockup and an external lockup. The transmission 21 includes an input shaft 22 as an input member, an output shaft 23 as an output member, a planetary continuously variable transmission mechanism 24 as a continuously variable transmission mechanism (main transmission mechanism), and a controller 25. More preferably, the transmission 21 includes a multi-stage transmission mechanism 26 as a stepped transmission mechanism (auxiliary transmission mechanism), and a direct-coupled mechanism 27 as an external lockup mechanism. The direct-coupled mechanism 27 includes a first clutch 27C that is connected when transmitting power through the direct-coupled mechanism 27. The transmission 21 also includes an idler element 28 (idler shaft 28A, idler gear 28B) that mechanically couples the planetary continuously variable transmission mechanism 24, the multi-stage transmission mechanism 26, and the direct-coupled mechanism 27. The planetary type continuously variable transmission mechanism 24 constitutes a first power transmission path. The direct drive mechanism 27 constitutes a second power transmission path.

[0040] An engine 9 is connected to an input shaft 22 of the transmission 21. A gear 10B for transmitting power to the hydraulic pump 10 is provided on the input shaft 22. An input gear 27A of a direct drive mechanism 27 is also provided on the input shaft 22. The input shaft 22 is connected to a planetary type continuously variable transmission mechanism 24 (more specifically, a planetary gear mechanism 29) via a second connecting member 31 described later. On the other hand, power is output from an output shaft 23 of the transmission 21. The output shaft 23 of the transmission 21 also serves as an output shaft 53 of a multi-stage transmission mechanism 26 described later. The power input from the input shaft 22 is transmitted to an idler element 28 via the planetary type continuously variable transmission mechanism 24 or the direct drive mechanism 27. The power transmitted to the idler element 28 is output from the output shaft 23 through the multi-stage transmission mechanism 26.

[0041] The planetary continuously variable transmission mechanism 24 is put into an internal lockup state by stopping the first connecting member 30 connecting the planetary gear mechanism 29 (for example, the first sun gear 29B) and the first variator 33. This internal lockup state is created, for example, by braking the first variator 33 to stop the first connecting member 30. When the planetary continuously variable transmission mechanism 24 is in an internal lockup state, the power input from the input shaft 22 is transmitted to the idler element 28 through the "second connecting member 31 connecting the planetary gear mechanism 29 (for example, the carrier 29A) and the input shaft 22," the "planetary gear mechanism 29," and the "third connecting member 32 connecting the planetary gear mechanism 29 (for example, the second sun gear 29C) and the idler element 28." Such internal lockup will be described later.

[0042] In the first embodiment, the power transmission path for transmitting the power input from the engine 9 to the input shaft 22 to the multi-speed mechanism 26 can be arbitrarily selected from the following three paths: (A), (B), or (C). (A) An infinitely variable transmission path (first power transmission path via the planetary type continuously variable transmission mechanism 24) that transmits the power input from the engine 9 to the input shaft 22 to the multi-speed transmission mechanism 26 while the planetary type continuously variable transmission mechanism 24 is being infinitely variable. At this time, the first clutch 27C is released, and the second clutch 36 and the third clutch 37 are connected (engaged). (B) An internal lockup path (a first power transmission path passing through the planetary type continuously variable transmission mechanism 24) that transmits the power input from the engine 9 to the input shaft 22 to the multi-stage transmission mechanism 26 with the planetary type continuously variable transmission mechanism 24 in an internal lockup state. At this time, the first clutch 27C is released and the second clutch 36 is connected (engaged). The third clutch 37 is connected (engaged) as necessary. (C) An external lockup path (a second power transmission path that passes through the direct drive mechanism 27 without passing through the planetary type continuously variable transmission mechanism 24) that transmits the power input from the engine 9 to the input shaft 22 to the multi-stage transmission mechanism 26 via the direct drive mechanism 27. At this time, the first clutch 27C is connected (engaged), and the second clutch 36 and the third clutch 37 are released as necessary.

[0043] As a result, when it is appropriate to infinitely change the speed of the planetary continuously variable transmission mechanism 24, power can be transmitted by infinitely changing the speed of the planetary continuously variable transmission mechanism 24. When it is appropriate to internally lock up the planetary continuously variable transmission mechanism 24, power can be transmitted by internally locking up the planetary continuously variable transmission mechanism 24. When it is appropriate to transmit power via the direct drive mechanism 27, power can be transmitted via the direct drive mechanism 27.

[0044] The times when it is appropriate to transmit power by continuously changing the speed of the planetary type continuously variable transmission mechanism 24 are during excavation and transportation, and when the vehicle speed is in the range of 0 to 7 km / h. The reasons for this are as follows (a) to (c). (a) High transmission efficiency when the vehicle starts and when digging. (b) The gear ratio can be made infinitely large. In other words, even if the engine 9 is rotating, it is possible to transmit torque to the output shaft 23 while stopping the rotation of the output shaft 23. This makes it suitable for excavation work. (c) It is possible to control the torque of the power generated by the engine 9 that is transmitted to the output shaft 23 through the transmission 21. In other words, power can be distributed between the hydraulic pump 10 that drives the loading and unloading machine 7 and the transmission 21.

[0045] The times when it is appropriate to transmit power by internally locking up the planetary continuously variable transmission mechanism 24 are when the vehicle is being transported or driven and when the vehicle speed is in the range of 7 to 9 km / h. The reasons for this are as follows (d) to (e). (d) When the vehicle speed increases, power transmission efficiency is higher when the planetary continuously variable transmission mechanism 24 is internally locked up to transmit power, rather than when the planetary continuously variable transmission mechanism 24 is caused to change speed continuously. (e) It is mechanically possible to switch from infinitely variable speed to internal lockup. Therefore, when switching from infinitely variable speed to internal lockup, sudden fluctuations in rotation of the engine 9 can be suppressed. This makes it possible to suppress sudden fluctuations in the discharge flow rate of the hydraulic pump 10, improving the operability of the loading and unloading machine 7. At the same time, it is possible to reduce fluctuations in the torque of the output shaft 23 when switching, improving the ride comfort of the wheel loader 1.

[0046] When it is appropriate to transmit the power via the direct drive mechanism 27, the vehicle speed is in the range of 9 to 13 km / h during transportation. Also, when the vehicle is being sent out, the vehicle speed is in the range of 9 to 40 km / h. The reason is as follows. That is, the external lockup, which transmits the power via the direct drive mechanism 27, has the highest power transmission efficiency. That is, the external lockup transmits the power by meshing between a pair of gears 27A, 27B, and therefore has a higher transmission efficiency than the internal lockup, which transmits the power via the planetary gear mechanism 29. Note that when the vehicle speed is 9 km / h or less, excavation may suddenly start during the sending out or transportation. On the other hand, when the power transmission path is switched from the direct drive mechanism 27 (external lockup) to the planetary type continuously variable transmission mechanism 24, this switching may take time. For this reason, it is preferable not to use the direct drive mechanism 27 when the vehicle speed is 9 km / h or less.

[0047] Table 1 below shows combinations of power transmission paths for transmission 21 equipped with both internal lockup and external lockup. In this case, multi-speed mechanism 26 is equipped with four forward gears and one reverse gear. Therefore, when power is transmitted via direct drive mechanism 27 (external lockup mechanism), multi-speed mechanism 26 can select from the following gears: first forward gear, second forward gear, third forward gear, fourth forward gear, and first reverse gear.

[0048] [Table 1]

[0049] Even if the speed stage of the multi-speed transmission mechanism 26 is either the second forward speed, the third forward speed, or the fourth forward speed, the power may be transmitted via the planetary continuously variable transmission mechanism 24 without passing through the direct drive mechanism 27. The operation of the planetary continuously variable transmission mechanism 24 at this time may be a continuously variable speed operation or may be in an internal lockup state. However, when the planetary continuously variable transmission mechanism 24 is operated continuously variable speed, the transmission efficiency is lower than that of the internal lockup and external lockup. This reduces the transmission efficiency of the transmission device 21, so it is preferable to select the combination of power transmission paths shown in Table 1 above.

[0050] FIG. 18 shows a driving force diagram of the transmission 21 in which both the internal lockup and the external lockup exist. As shown in FIG. 18, the forward direction can be shifted in six stages, namely, forward 1st speed infinitely variable speed Lf1, forward 1st speed internal lockup Lf2, forward 1st speed external lockup Lf3, forward 2nd speed external lockup Lf4, forward 3rd speed external lockup Lf5, and forward 4th speed external lockup Lf6. This allows the forward direction to approach the ideal driving force line Lf as much as possible. However, the forward 1st speed infinitely variable speed Lf1 reduces the tractive force when the vehicle speed is 0 to 4 km / h, and there is a possibility that the tractive force required for excavation cannot be sufficiently secured. In the embodiment, when traveling at the forward 1st speed infinitely variable speed Lf1 in order to secure the tractive force, the torque boost control described later is performed, thereby allowing the forward direction to approach the ideal driving force line Lf as much as possible.

[0051] On the other hand, the reverse direction can be changed to three stages: reverse 1-speed infinitely variable speed Lr1, reverse 1-speed internal lockup Lr2, and reverse 1-speed external lockup Lr3. This allows the vehicle to approach the ideal driving force line Lr in the reverse direction as much as possible. This allows the vehicle to obtain high traction force during excavation, high vehicle speed (0 to 40 km / h) during transportation, and stable climbing of uphill slopes with various gradients. However, the reverse 1-speed infinitely variable speed Lr1 reduces traction force when the vehicle speed is 0 to 5 km / h, and there is a possibility that the vehicle cannot obtain sufficient traction force to get out of a state in which the wheels 2, 4 have fallen into a depression in the road surface. In the embodiment, when the vehicle is traveling at the reverse 1-speed infinitely variable speed Lr1 in order to obtain traction force, the vehicle can approach the ideal driving force line Lr as much as possible by performing torque boost control described later.

[0052] In order to achieve a wide gear ratio range, a configuration having both "internal lockup of planetary continuously variable transmission mechanism 24" and "external lockup by direct drive mechanism 27" is preferable. However, in order to achieve "effectively using the speed increase range of planetary continuously variable transmission mechanism 24 while suppressing changes in the acceleration / deceleration of the vehicle when power transmission is switched from the continuously variable transmission state to the lockup state," a configuration having only either the internal lockup or the external lockup may be used.

[0053] 19 shows a first modified transmission 21A that has only an internal lockup of the planetary continuously variable transmission mechanism 24 as a means for achieving lockup. This first modified transmission 21A is capable of performing an internal lockup operation of the planetary continuously variable transmission mechanism 24, but does not have an external lockup mechanism (direct drive mechanism 27). Table 2 below shows combinations of power transmission paths for the transmission 21A that has only an internal lockup.

[0054] [Table 2]

[0055] In the first modified example, the number of gears by the direct drive mechanism 27 (external lockup) is reduced by one. Therefore, in order to obtain a gear ratio equivalent to that of the transmission 21 in which both the internal lockup and the external lockup exist, in the first modified example, the multi-speed mechanism 26A is provided with five forward gears and two reverse gears. In addition, in the first modified example, a block mechanism 40 is provided for realizing the internal lockup as described later. The block mechanism 40 may be configured to also function as the power absorbing device 38 described later, or may be provided separately from the power absorbing device 38. Note that FIG. 20 shows a transmission 21B according to a second modified example. The transmission 21B according to the second modified example also omits the external lockup mechanism as in the first modified example. In addition, in the second modified example, a brake mechanism 41 is provided for realizing the internal lockup as described later. Furthermore, FIG. 21 shows a transmission 21C according to a third modified example. Transmission device 21C according to the third modified example omits the external lockup mechanism, and in addition to being equipped with brake mechanism 41, omits idler element 28. That is, in the case of a configuration in which direct-coupled mechanism 27 (external lockup) is omitted, idler element 28 can also be omitted.

[0056] Fig. 22 shows a driving force diagram of the transmissions 21A, 21B, 21C (Figs. 19, 20, 21) that are equipped with the planetary type continuously variable transmission mechanism 24 (internal lockup) but not the direct drive mechanism 27 (external lockup). As shown in Fig. 22, the forward speed can be changed to six stages: forward 1st speed infinitely variable Lf1, forward 1st speed internal lockup Lf2, forward 2nd speed internal lockup Lf3, forward 3rd speed internal lockup Lf4, forward 4th speed internal lockup Lf5, and forward 5th speed internal lockup Lf6. On the other hand, the reverse speed can be changed to three stages: reverse 1st speed infinitely variable Lr1, reverse 1st speed internal lockup Lr2, and reverse 2nd speed internal lockup Lr3.

[0057] In contrast, a configuration with only external lockup can be achieved, for example, by not performing internal lockup operation in transmission 21 of the first embodiment (FIGS. 3 and 4). Table 3 below shows combinations of power transmission paths for transmission 21 that has an external lockup (direct drive mechanism 27) but does not perform internal lockup operation.

[0058] [Table 3]

[0059] Fig. 23 shows a driving force diagram of the transmission 21 that does not perform an internal lockup operation. As shown in Fig. 23, forward speed can be changed in five stages: forward 1st speed infinitely variable Lf1, forward 1st speed external lockup Lf2, forward 2nd speed external lockup Lf3, forward 3rd speed external lockup Lf4, and forward 4th speed external lockup Lf5. On the other hand, reverse speed can be changed in two stages: reverse 1st speed infinitely variable Lr1 and reverse 1st speed external lockup Lr2.

[0060] Next, the planetary type continuously variable transmission mechanism 24 will be described with reference to Fig. 3. The planetary type continuously variable transmission mechanism 24 includes a planetary gear mechanism 29, a first variator 33, a second variator 34, a transmission element 35, a second clutch 36, and a third clutch 37. The planetary gear mechanism 29 is connected to a first output side (first variator 33 side) via a first connecting member 30. The planetary gear mechanism 29 is connected to an input side (engine 9 side) via a second connecting member 31. The planetary gear mechanism 29 is connected to a second output side (idler element 28 side) via a third connecting member 32.

[0061] The first variator 33 and the second variator 34 are configured by an electric motor generator (electric motor, electric generator) or a hydraulic pump motor (hydraulic pump, hydraulic motor). Specifically, when the first variator 33 is configured by an electric motor, the second variator 34 is configured by an electric generator, and when the first variator 33 is configured by a hydraulic pump, the second variator 34 is configured by a hydraulic motor. The first variator 33 and the second variator 34 are configured to be capable of transmitting power between the first variator 33 and the second variator 34 while performing stepless speed change when the rotation speed of the first variator 33 and the rotation speed of the second variator 34 are different. For this purpose, a transmission element 35 for transmitting power between the first variator 33 and the second variator 34 is provided between the first variator 33 and the second variator 34. The transmission element 35 is configured by, for example, electric wiring or hydraulic piping. A power absorbing device 38 configured as a power storage source (power storage device) is attached midway through the transmission element 35. The power absorbing device 38 can be configured, for example, by a hydraulic accumulator or a storage battery. The power absorbing device 38 will be described later. The functions of the first variator 33, the second variator 34 and the transmission element 35 may be realized by an infinitely variable transmission (IVT).

[0062] A second clutch 36 is provided between the planetary gear mechanism 29 and the first variator 33, i.e., between the first connecting member 30 and the first variator 33. The second clutch 36 is configured, for example, by a friction-connected clutch (friction plate), a dog clutch, or a dog clutch with synchromesh. The second clutch 36 mechanically couples (connects) and releases the first connecting member 30 and the first variator 33 between them. That is, the second clutch 36 switches between the transmission and release of power between the planetary gear mechanism 29 and the first variator 33.

[0063] The controller 25 includes, for example, a microcomputer equipped with a calculation circuit (CPU), a memory, and the like. The controller 25 controls the engagement and release of the first clutch 27C, the engagement and release of the second clutch 36, and the engagement and release of the third clutch 37. The controller 25 controls the rotation speed of the first variator 33. The controller 25 controls the rotation speed of the second variator 34 as necessary. The controller 25 controls the transmission element 35 and the power absorbing device 38 as necessary. The controller 25 controls the block mechanism 40 (FIG. 19) and the brake mechanism 41 (FIGS. 20 and 21) as necessary. Furthermore, the controller 25 controls the engagement and release of the clutches 58, 59, 60, 66, 67, 68, and 69 of the multi-speed mechanism 26 as described below.

[0064] Here, the controller 25 controls the engagement and disengagement of the second clutch 36. For example, when power transmission by the planetary continuously variable transmission mechanism 24 is not required, the controller 25 outputs a signal to disengage the second clutch 36, thereby disengaging the second clutch 36. This makes it possible to stop (or reduce) the rotation of the first variator 33, and reduce power loss due to the rotation of the first variator 33.

[0065] The second variator 34 is connected to the idler element 28 via a third clutch 37. The third clutch 37 switches between transmission and release of power between the second variator 34 and the idler element 28. That is, the third clutch 37 is provided between the second variator 34 and the idler element 28. The idler element 28 includes an idler shaft 28A and an idler gear 28B provided on the idler shaft 28A. The idler shaft 28A is connected to a lockup gear 27B (more specifically, a rotating shaft 27B1 of the lockup gear 27B) of the direct drive mechanism 27 via a first clutch 27C.

[0066] Moreover, the idler shaft 28A is connected to the second variator 34 via a transmission 39 and a third clutch 37. The 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. A transmission 39 that changes gears between the second variator 34 and the idler element 28 is provided between the second variator 34 and the idler element 28. This transmission 39 may be omitted. In this case, a third clutch 37 is provided between the idler shaft 28A of the idler element 28 and the rotating shaft of the second variator 34, and the third clutch 37 can connect (connect) and release the idler shaft 28A and the rotating shaft of the second variator 34.

[0067] The third clutch 37 is, for example, a friction-connected clutch (friction plate), a dog clutch, or a dog clutch with synchromesh. The third clutch 37 mechanically couples (connects) and releases the second variator 34 and the idler element 28. The controller 25 controls the engagement and release of the third clutch 37. For example, when power transmission by the second variator 34 is not required, the controller 25 outputs a signal to release the third clutch 37, and releases the third clutch 37. This makes it possible to stop (or reduce) the rotation of the second variator 34, and to reduce power loss due to the rotation of the second variator 34. However, under these conditions, it is not necessarily necessary to release the third clutch 37.

[0068] Note that when power transmission by the second variator 34 is not required, and when power transmission by the planetary continuously variable transmission mechanism 24 is not required, the following conditions (f) to (i) are assumed, for example. However, it is not always necessary to release the second clutch 36 or the third clutch 37 under these conditions (f) to (i). (f) When the power input from the input shaft 22 is transmitted to the idler element 28 via the direct-coupled mechanism 27. (g) When the rotation of the first connecting member 30 is fixed by means other than the first variator 33 (for example, the brake mechanism 41), causing the planetary type continuously variable transmission mechanism 24 to be in an internal lockup state. (h) When the vehicle is stationary. (i) When the vehicle is gliding (coasting).

[0069] The power transmitted from the engine 9 to the second connecting member 31 is distributed by the planetary gear mechanism 29 to the first connecting member 30 connected to the first variator 33 and the third connecting member 32 connected to the idler element 28. The power distributed to the first connecting member 30 is transmitted to the idler element 28 via the second clutch 36, the first variator 33, the transmission element 35, the second variator 34, the third clutch 37, and the transmission 39. The power distributed to the third connecting member 32 is transmitted to the idler element 28. The torque distribution ratio between the first connecting member 30 and the third connecting member 32 is always constant and depends on the type of the planetary gear mechanism 29 and the meshing radius of the gears.

[0070] However, the torque distribution ratio between the first connecting member 30 and the third connecting member 32 is constant. For this reason, power is not always transmitted from the first variator 33 to the second variator 34, but may be transmitted from the second variator 34 to the first variator 33. The power transmitted from the third connecting member 32 to the idler element 28 has a smaller loss than the power transmitted from the first connecting member 30 through the first variator 33 and the second variator 34. For this reason, the planetary type continuously variable transmission mechanism 24, which combines the variators 33, 34 and the planetary gear mechanism 29, has a higher power transmission efficiency than a continuously variable transmission that transmits power using only a variator.

[0071] Next, the planetary gear mechanism 29 will be described. In FIG. 3, the planetary gear mechanism 29 is shown by a square (block). Here, the planetary gear mechanism 29 has three members (rotating members): a first member connected to the engine 9, which is the power source, a second member connected to the first variator 33, and a third member connected to the idler element 28 on the output shaft 23 side. Here, in the first embodiment, the planetary gear mechanism 29 is composed of a carrier and two sun gears (a first sun gear and a second sun gear). Table 4 below shows the combination of the components (carrier, a first sun gear, a second sun gear) of the planetary gear mechanism 29. "No. 1-A" in Table 4 is most suitable in terms of improving the transmission efficiency of the planetary type continuously variable transmission mechanism 24 while configuring the planetary gear mechanism 29 to be small and lightweight.

[0072] [Table 4]

[0073] 4 to 6, in the first embodiment (i.e., No. 1-A in Table 4), planetary gear mechanism 29 includes carrier 29A corresponding to the first member, first sun gear 29B corresponding to the second member, second sun gear 29C corresponding to the third member, planet gear 29D, and balance gear 29E. Note that first sun gear 29B, second sun gear 29C, planet gear 29D, and balance gear 29E do not necessarily need to transmit power by meshing of gears (gears), and may transmit power by friction of rollers (outer circumferential surfaces), for example.

[0074] The engine 9 is coupled to the carrier 29A via a second connecting member 31. The first sun gear 29B is connected to a first variator 33 via a first connecting member 30. The second sun gear 29C is connected to an idler element 28 (idler gear 28B) via a third connecting member 32. The first sun gear 29B meshes with a planet gear 29D. The second sun gear 29C meshes with a balance gear 29E. The balance gear 29E meshes with the planet gear 29D.

[0075] The rotation axis Sp of the planet gear 29D (FIG. 6) and the rotation axis Sb of the balance gear 29E (FIG. 6) are supported by the carrier 29A. Therefore, the planet gear 29D and the balance gear 29E rotate while revolving around the central axis S of the planetary gear mechanism 29 (FIG. 6). The planet gear 29D has a gear portion 29D1 that meshes with the first sun gear 29B, and a gear portion 29D2 that meshes with the balance gear 29E. The constraint condition for the establishment of the planetary gear mechanism 29 is that the distance between the central axis S of the first sun gear 29B and the rotation axis Sp of the planet gear 29D coincides with the distance between the central axis S of the second sun gear 29C and the rotation axis Sp of the planet gear 29D. For this reason, it is necessary to adjust the number of teeth, gear module, gear shift, and rotation center position of the balance gear 29E of each of the first sun gear 29B, planet gear 29D, gear portion 29D1 meshing with the first sun gear 29B, second sun gear 29C, balance gear 29E, and gear portion 29D2 meshing with the balance gear 29E, and to match the distance. That is, it is sufficient to match the distance, and for example, it is possible to reduce the difference in the number of teeth between the first sun gear 29B and the second sun gear 29C, or to make them the same number of teeth. For this reason, the reduction ratio of the planetary gear mechanism 29 can be freely set.

[0076] According to the first embodiment, the balance gear 29E is provided between the second sun gear 29C and the planet gear 29D, but it may be provided between the first sun gear 29B and the planet gear 29D. However, power transmission is possible when the balance gear 29E is provided both between "the second sun gear 29C and the planet gear 29D" and between "the first sun gear 29B and the planet gear 29D", or even when the balance gear 29E is not provided on either side. However, it is preferable to provide a balance gear on either side.

[0077] Next, the operation of the planetary gear mechanism 29 composed of the carrier 29A and the two sun gears 29B, 29C will be described. The following applies under all conditions of “No1-A”, “No1-B”, and “No1-C” in Table 4.

[0078] First, the distribution of torque among the three members of the planetary gear mechanism 29 (the carrier 29A and the two sun gears 29B, 29C) will be described. FIG. 6 is a cross-sectional view of the planetary gear mechanism 29 viewed from the power source side. The carrier 29A, the first sun gear 29B, and the second sun gear 29C are arranged concentrically. That is, the central axes S (central axes of rotation) of the carrier 29A, the first sun gear 29B, and the second sun gear 29C coincide with each other. The first sun gear 29B meshes with a gear portion 29D1 of the planet gear 29D. The second sun gear 29C meshes with a balance gear 29E. The balance gear 29E meshes with a gear portion 29D2 of the planet gear 29D. The balance gear 29E and the planet gear 29D rotate freely in the direction of rotation by the carrier 29A so that the gears mesh with each other, and are constrained in the direction of revolution about the central axis S. Therefore, the planet gear 29D rotates about the rotation axis Sp, which is the central axis of the planet gear 29D, and revolves about the central axis S of the carrier 29A. Therefore, the locus Cp of the central axis (spinning axis Sp) of the planet gear 29D forms a circle centered on the central axis S of the carrier 29A. The balance gear 29E rotates about the spin axis Sb, which is the central axis of the balance gear 29E, and revolves about the central axis S of the carrier 29A. Therefore, the locus Cb of the central axis (spinning axis Sb) of the balance gear 29E forms a circle centered on the central axis S of the carrier 29A.

[0079] The meshing radius rs1 of the first sun gear 29B is the meshing radius on the first sun gear 29B side when the first sun gear 29B and the planet gear 29D mesh. The meshing radius rp1 of the gear portion 29D1 of the planet gear 29D is the meshing radius on the gear portion 29D1 side when the first sun gear 29B and the planet gear 29D mesh. The meshing radius rs2 of the second sun gear 29C is the meshing radius on the second sun gear 29C side when the second sun gear 29C and the balance gear 29E mesh. The meshing radius rp2 of the gear portion 29D2 of the planet gear 29D is the meshing radius on the planet gear 29D side when the balance gear 29E and the planet gear 29D mesh.

[0080] In the first embodiment (No. 1-A in Table 4), carrier 29A is connected to a member (terminal) connected to engine 9, i.e., second connecting member 31, so that torque Tc of carrier 29A is a torque that can be generated by engine 9. First sun gear 29B is connected to a member (terminal) connected to first variator 33, i.e., first connecting member 30, so that torque Ts1 of first sun gear 29B is a torque that can be generated by first variator 33. Second sun gear 29C is connected to a member (terminal) connected to idler element 28, i.e., third connecting member 32, so that torque Ts2 of second sun gear 29C is a torque reaction force received from idler gear 28B.

[0081] In transmission 21D of a fourth modified example (i.e., No. 1-B in Table 4) shown in FIG. 24, first sun gear 29B is connected to a member connected to engine 9, i.e., second connecting member 31, so that torque Ts1 of first sun gear 29B is a torque that can be generated by engine 9. Carrier 29A is connected to a member connected to first variator 33, i.e., first connecting member 30, so that torque Tc of carrier 29A is a torque that can be generated by first variator 33. Second sun gear 29C is connected to a member connected to idler element 28, i.e., third connecting member 32, so that torque Ts2 of second sun gear 29C is a torque reaction force received from idler gear 28B.

[0082] In transmission 21E of a fifth modified example (i.e., No. 1-C in Table 4) shown in FIG. 25, first sun gear 29B is connected to a member connected to engine 9, i.e., second connecting member 31, so that torque Ts1 of first sun gear 29B is a torque that can be generated by engine 9. Second sun gear 29C is connected to a member connected to first variator 33, i.e., first connecting member 30, so that torque Ts2 of second sun gear 29C is a torque that can be generated by first variator 33. Carrier 29A is connected to a member connected to idler element 28, i.e., third connecting member 32, so that torque Tc of carrier 29A is a torque reaction force received from idler gear 28B.

[0083] Next, the relationship between torque Ts1 of first sun gear 29B, torque Ts2 of second sun gear 29C, and torque Tc of carrier 29A will be described. First, first sun gear 29B and second sun gear 29C mesh with each other via planet gear 29D and balance gear 29E. Balance gear 29E and planet gear 29D rotate freely in the rotation direction by carrier 29A, and are constrained in the revolution direction with respect to central axis S of carrier 29A. From these, the action-reaction relationship can be obtained as the following formulas 5, 6, and 7.

[0084]

number

[0085]

number

[0086]

number

[0087] From these formulas, torque Ts1 of first sun gear 29B, torque Ts2 of second sun gear 29C, and torque Tc of carrier 29A can be calculated from meshing radius rp2 of gear portion 29D2, meshing radius rs2 of second sun gear 29C, meshing radius rp1 of gear portion 29D1, and meshing radius rs1 of first sun gear 29B. Meshing radius rp2 of gear portion 29D2, meshing radius rs2 of second sun gear 29C, meshing radius rp1 of gear portion 29D1, and meshing radius rs1 of first sun gear 29B are determined by the meshing radius of each gear, and therefore cannot be changed while planetary type continuously variable transmission mechanism 24 is transmitting power. Therefore, the ratio between torque Ts1 of first sun gear 29B, torque Ts2 of second sun gear 29C, and torque Tc of carrier 29A remains unchanged while planetary type continuously variable transmission mechanism 24 is transmitting power.

[0088] Based on this law, the controller 25 outputs a signal to control the first variator 33, and controls the torque of the first connecting member 30 (for example, the first sun gear 29B) connected to the first variator 33. That is, the controller 25 controls the torque of the first connecting member 30 (for example, the first sun gear 29B) by controlling the first variator 33. As a result, the controller 25 indirectly controls the torque of the second connecting member 31 (for example, the carrier 29A) connected to the engine 9 and the torque of the third connecting member 32 (for example, the second sun gear 29C) connected to the idler element 28. As a result, it is possible to control the transmission torque between the second connecting member 31 (for example, the carrier 29A) connected to the engine 9 and the third connecting member 32 (for example, the second sun gear 29C) connected to the idler element 28.

[0089] Next, the relationship between the rotation speed of the first sun gear 29B, the rotation speed of the second sun gear 29C, and the rotation speed of the carrier 29A will be described. First, the first sun gear 29B and the second sun gear 29C are meshed with each other via the planet gear 29D and the balance gear 29E. The balance gear 29E and the planet gear 29D rotate freely in the rotation direction by the carrier 29A, and are constrained in the revolution direction with respect to the central axis S of the carrier 29A. From these, the relationship between the rotation speeds is obtained as shown in the following formula 8. Note that "Ka" in formula 8 is as shown in formula 9. Note that the rotation speed of the carrier 29A is "Vc", the rotation speed of the first sun gear 29B is "Vs1", and the rotation speed of the second sun gear 29C is "Vs2".

[0090]

number

[0091]

number

[0092] FIG. 7 shows the relationship of the rotation speed of the planetary gear mechanism 29. The speed relationship line Y1 in FIG. 7 is a diagram of the formula 8. It is assumed that the rotation speed of the carrier 29A is constant. In this case, if the rotation speed of the second sun gear 29C is increased, the rotation speed of the first sun gear 29B is decreased. Conversely, if the rotation speed of the second sun gear 29C is decreased, the rotation speed of the first sun gear 29B is increased. Based on this law, the controller 25 outputs a signal to control the first variator 33, and controls the rotation speed of the first connecting member 30 (for example, the first sun gear 29B) connected to the first variator 33. That is, the controller 25 controls the rotation speed of the first connecting member 30 (for example, the first sun gear 29B) by controlling the first variator 33. Thereby, the controller 25 indirectly controls the rotation speed of the second connecting member 31 (e.g., carrier 29A) connected to the engine 9 and the rotation speed of the third connecting member 32 (e.g., second sun gear 29C) connected to the idler element 28. As a result, it is possible to control the gear ratio between the second connecting member 31 (e.g., carrier 29A) connected to the engine 9 and the third connecting member 32 (e.g., second sun gear 29C) connected to the idler element 28.

[0093] As described above, in planetary gear mechanism 29, the distance between central axis S of first sun gear 29B and rotation axis Sp of planet gear 29D must match the distance between central axis S of second sun gear 29C and rotation axis Sp of planet gear 29D. That is, it is only necessary to match these distances, and for example, meshing radius rs1 of first sun gear 29B, meshing radius rp1 of gear portion 29D1, meshing radius rs2 of second sun gear 29C, and meshing radius rp2 of gear portion 29D2 can be freely set. Therefore, planetary gear mechanism 29 adjusts meshing radius rs1 of first sun gear 29B, meshing radius rp1 of gear portion 29D1, meshing radius rs2 of second sun gear 29C, and meshing radius rp2 of gear portion 29D2 in accordance with the torque that can be absorbed by first variator 33 and the maximum allowable rotation speed, based on the relational expressions (Equation 5, Equation 6, Equation 7) between torques Tc, Ts1, and Ts2 and the relational expressions (Equation 8 and Equation 9) between rotational speeds Vs1, Vs2, and Vc. As a result, by setting the value of Ka in Equation 9 to an ideal value and setting the gradient of speed relation line Y1 shown in Fig. 7 to an ideal value, it becomes possible to match the torque and rotation speed of planetary gear mechanism 29 to both the torque that can be absorbed by first variator 33 and the maximum allowable rotation speed. As a result, a small and inexpensive first variator 33 can be used, and the transmission efficiency of the planetary type continuously variable transmission mechanism 24 can be improved.

[0094] The size and price of the first variator 33 are proportional to the magnitude of the torque that the first variator 33 can absorb. For this reason, it is desirable that the torque absorbed by the first variator 33 is small. A specific example will be described in the first embodiment (i.e., No. 1-A in Table 4). First, it is desirable to make the value of Ka in the formula 9 small. Furthermore, the power transmission efficiency between the planetary gear mechanism 29 and the idler element 28 will be considered. In this case, the transmission efficiency of the power transmission path via the first connecting member 30, the first variator 33, the transmission element 35, the second variator 34, the transmission 39, and the third clutch 37 is about 70 to 80%. On the other hand, the transmission efficiency of the power transmission path via the third connecting member 32 is about 99%. For this reason, the smaller the torque distributed to the first variator 33, the more the transmission efficiency of the planetary continuously variable transmission mechanism 24 can be improved. For this reason, it is advantageous for the planetary continuously variable transmission mechanism 24 to make the value of Ka in the formula (9) small.

[0095] On the other hand, from the speed relationship line Y1 shown in FIG. 7, when the value of Ka is reduced, the "rotational speed of the first sun gear / rotational speed of the carrier (horizontal axis)" increases when the "rotational speed of the second sun gear / rotational speed of the carrier (vertical axis)" is small. Since the second sun gear 29C is connected to the output shaft 23 via the idler element 28 and the multi-stage transmission mechanism 26, when the "rotational speed of the second sun gear / rotational speed of the carrier" is small, the power source (engine 9) is rotating and the vehicle speed is low. In other words, when the rotational speed of the carrier 29A (rotational speed of the power source) is constant, if Ka is reduced, the rotational speed of the first variator 33 increases when the vehicle is running at a low speed. As a specific example, when the "rotational speed of the second sun gear / rotational speed of the carrier" is 0, the second sun gear 29C rotates at 0. Since the second sun gear 29C is connected to the output shaft 23 via the idler element 28 and the multi-stage transmission mechanism 26, the second sun gear 29C is -1 In this case, the vehicle speed is 0 km / h. In other words, the speed ratio of the planetary type continuously variable transmission mechanism 24 is infinite. The rotation speed of the first sun gear 29B is limited to 6000 min -1 If the power source (Engine 9) is a diesel engine, the rotation speed limit of Carrier 29A is 2000 min-1 Since the rotation speed of the first sun gear / the rotation speed of the carrier is about 3.0, the "rotation speed of the first sun gear / the rotation speed of the carrier" is 3.0. When "rotation speed of the second sun gear / the rotation speed of the carrier=0" and "rotation speed of the first sun gear / the rotation speed of the carrier=3" are substituted into the formula 8, Ka=0.5. In other words, the lower limit value of Ka is about Ka=0.5. As described above, it is desirable to make the value of Ka small within a range that does not exceed the allowable maximum rotation speed of the first variator 33. And, the planetary gear mechanism 29 composed of the carrier and two sun gears can freely set the meshing radius rs1 of the first sun gear 29B, the meshing radius rp1 of the gear portion 29D1, the meshing radius rs2 of the second sun gear 29C, and the meshing radius rp2 of the gear portion 29D2, and therefore the value of Ka can be freely determined. Therefore, the first variator 33 can be operated up to the allowable maximum rotation speed. This makes it possible to use a small and inexpensive first variator 33, and also improves the transmission efficiency of the planetary continuously variable transmission mechanism 24 to 80 to 93%.

[0096] For this reason, it is desirable to increase the value of Ka within a range that does not exceed the maximum allowable rotation speed of the first variator 33. And, because the value of Ka can be freely determined as described above, it is possible to operate the first variator 33 up to its maximum allowable rotation speed. This makes it possible to use a small and inexpensive first variator 33, and to improve the transmission efficiency of the planetary continuously variable transmission mechanism 24 to 80 to 93%.

[0097] Since the value of Ka can be freely determined as described above, it is possible to operate the first variator 33 up to the maximum allowable rotation speed of the first connecting member 30 connected to the first variator 33. This reduces the transmission torque of the first variator 33, allowing the use of a small, inexpensive first variator 33.

[0098] In the first embodiment (No. 1-A in Table 4) shown in FIG. 4, the terminal (also referred to as the first connecting member 30, the terminal 30) connected to the first variator 33 is connected to the first sun gear 29B. From the above formulas 5, 6, and 7, it is possible to increase the torque of the first sun gear 29B and the carrier 29A by increasing the absorption torque of the first variator 33, and to increase the torque of the terminal (also referred to as the third connecting member 32, the terminal 32) connected to the idler gear 28B connected to the second sun gear 29C. The terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-stage transmission mechanism 26, and therefore the torque of the output shaft 23 can be increased. Meanwhile, the relationship between the above formulas 8 and 9 is shown in FIG. 7. When the rotation speed of the carrier 29A is constant, when the rotation speed of the second sun gear 29C is low (i.e., when the vehicle speed is low), the rotation speed (rotation speed) of the first sun gear 29B becomes high. When the vehicle speed is low, the rotation speed of the second variator 34 is low, so if the absorption torque of the first variator 33 is increased, the first variator 33 will send to the transmission element 35 more power than the second variator 34 can receive. For this reason, when the vehicle speed is below a predetermined value, the power absorption device 38 installed on the transmission element 35 absorbs (disposes of or stores) the surplus power. This allows the transmission 21 to increase the output torque when the vehicle speed is 0 to 5 km / h, and the traction force of the wheel loader 1 increases.

[0099] In a fourth modified example (No. 1-B in Table 4) shown in FIG. 24, terminal 30 connected to first variator 33 is connected to carrier 29A. From formulas 5, 6, and 7, by increasing the absorption torque of first variator 33, the torque of first sun gear 29B and second sun gear 29C can be increased, and the torque of terminal 32 connected to idler gear 28B connected to second sun gear 29C can be increased. Terminal 32 connected to idler gear 28B is connected to output shaft 23 via idler gear 28B and multi-speed mechanism 26, so that the torque of output shaft 23 can be increased. Meanwhile, by transforming formula 8, formula 10 below is obtained.

[0100]

number

[0101] Moreover, according to Equation 9, Ka>0, so the intercept of Equation 10 is negative. This relationship is shown in FIG. 8. When the rotation speed of first sun gear 29B is constant, the rotation speed of carrier 29A is proportional to the rotation speed of second sun gear 29C. For example, when the vehicle speed is 0 (when the rotation speed of second sun gear 29C is 0), carrier 29A rotates, so that first variator 33 rotates, whereas the rotation speed of second variator 34 is 0. When the vehicle speed is 0, if the absorption torque of first variator 33 is increased, first variator 33 sends to transmission element 35 more power than second variator 34 can receive. Therefore, when the vehicle speed is equal to or lower than a predetermined value, power absorbing device 38 installed on transmission element 35 absorbs (disposes of or stores) the surplus power. As a result, the transmission 21D can increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0102] In a fifth modified example (No. 1-C in Table 4) shown in FIG. 25, the terminal 30 connected to the first variator 33 is connected to the second sun gear 29C. From the above-mentioned formulas 5, 6, and 7, by increasing the absorption torque of the first variator 33, the torque of the second sun gear 29C and the carrier 29A can be increased, and the torque of the terminal 32 connected to the idler gear 28B connected to the carrier 29A can be increased. Since the terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, the torque of the output shaft 23 can be increased. On the other hand, by transforming the above-mentioned formula 8, the following formula 11 is obtained.

[0103]

number

[0104] Moreover, according to Equation 9, Ka>0, so the intercept of Equation 11 is positive. This relationship is shown in FIG. 9. When the rotation speed of first sun gear 29B is constant, when the rotation speed of carrier 29A is low (i.e., when the vehicle speed is low), the rotation speed of carrier 29A is proportional to the rotation speed of second sun gear 29C. For example, when the vehicle speed of the vehicle is 0 (when the rotation speed of carrier 29A is 0), second sun gear 29C is rotating, so that first variator 33 is rotating, whereas the rotation speed of second variator 34 is 0. When the vehicle speed of the vehicle is 0, if the absorption torque of first variator 33 is increased, first variator 33 will send more power to transmission element 35 than second variator 34 can receive. For this reason, when the vehicle speed is below a predetermined level, the power absorbing device 38 installed on the transmission element 35 absorbs (disposes of or stores) the surplus power. This enables the transmission 21E to increase the output torque when the vehicle speed is 0 to 5 km / h, increasing the tractive force of the wheel loader 1. For this reason, even if an inexpensive second variator 34 with a small output torque is used, a wheel loader 1 with high tractive force and high excavation performance can be provided.

[0105] Next, the effect of the torque boost will be described in more detail using the torque diagram shown in FIG. 10. This is common to "No1-A" to "No1-C" in Table 4 and "No2-A" to "No2-F" in Table 6 described later. The horizontal axis in FIG. 10 is the speed ratio of the planetary continuously variable transmission mechanism 24, and the vertical axis is the torque of the rotating element connected to the planetary gear mechanism 29 (the torque of the idler gear 28B). The speed ratio Ip of the planetary continuously variable transmission mechanism 24 is expressed by the following formula 12, where the rotation speed of the terminal 32 connected to the idler gear 28B is "Va" and the rotation speed of the power source (engine 9) is "Vb".

[0106]

number

[0107] The torque Ti of the idler gear 28B is expressed by the following equation (13), where the torque of the second variator 34 is "Tv", the gear ratio of the transmission 39 is "Ia", the torque of the terminal 32 connected to the idler gear 28B is "Ta", and the reduction ratio between the terminal 30 connected to the first variator 33 and the terminal 32 connected to the idler gear 28B is "Ra".

[0108]

number

[0109] The "gear ratio Ia of the transmission 39" and the "reduction ratio Ra between the terminal 30 connected to the first variator 33 and the terminal 32 connected to the idler gear 28B" are reduction ratios in power transmission by gear meshing or the like. By combining the above-mentioned formulas 5, 6, and 7, and Table 4, the torque Ta of the terminal 32 connected to the idler gear 28B is proportional to the torque of the terminal 30 connected to the first variator 33. Therefore, if the torque of the terminal 30 connected to the first variator 33 is increased, the torque Ta of the terminal 32 connected to the idler gear 28B can be increased. However, the first variator 33 and the second variator 34 transmit power to each other. Therefore, when the torque boost control described later is not performed, the "power sent from one to the other" and the "power received by the other from the one" need to be the same. The rotation speed of the second variator 34 is synchronized at the reduction ratio between the terminal 32 connected to the idler gear 28B and the terminal 30 connected to the first variator 33, and when the gear ratio is low, the rotation speed of the second variator 34 also decreases. For this reason, when the gear ratio is low (less than 0.5), if the second variator 34 is controlled to supply the power that it can fully receive as the power generated by the first variator 33, the torque of the first variator 33 decreases, as shown by characteristic line 101 in Fig. 10. The characteristic line 101 corresponds to the torque of the first variator 33 when torque boost is not performed.

[0110] When the torque of the first variator 33 (characteristic line 101) decreases, the torque of the terminal 32 connected to the idler gear 28B (characteristic line 104) also decreases according to the combination of the above-mentioned formulas 5, 6, and 7, and Table 4. The characteristic line 104 corresponds to the torque of the terminal 32 connected to the idler gear 28B when torque boost is not performed. When the torque of the terminal 32 connected to the idler gear 28B (characteristic line 104) decreases, the torque of the idler gear 28B (characteristic line 105) also decreases according to the above-mentioned formula 13. The characteristic line 105 corresponds to the torque of the idler gear 28B when torque boost is not performed. Due to the above-mentioned actions, when the gear ratio is low (less than 0.5), the torque of the idler gear 28B decreases. The terminal 32 coupled to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, so the torque of the output shaft 23 decreases. As a result, if torque boost is not performed, the output torque of the transmission 21 when the vehicle speed is 0 to 5 km / h decreases, and the traction force and excavation capacity of the wheel loader 1 decrease.

[0111] On the other hand, when torque boost control is performed, since the power absorbing device 38 is provided between the first variator 33 and the second variator 34, it is not necessary that the "power sent by one to the other" and the "power received by the other from the one" are the same. The rotation speed of the second variator 34 is synchronized at the reduction ratio between the terminal 32 connected to the idler gear 28B and the terminal 30 connected to the first variator 33, and when the gear ratio is low, the rotation speed of the second variator 34 also decreases. When the gear ratio is low (less than 0.5), even if the power generated by the first variator 33 is supplied as more power than the second variator 34 can receive, the power absorbing device 38 is provided, so that the decrease in the torque of the first variator 33 can be suppressed as shown by the characteristic line 103 in FIG. 10. The characteristic line 103 corresponds to the torque of the first variator 33 during torque boost.

[0112] Since the decrease in the torque (characteristic line 103) of the first variator 33 can be suppressed, the decrease in the torque (characteristic line 106) of the terminal 32 connected to the idler gear 28B can also be suppressed by combining the above-mentioned formulas 5, 6, and 7, and Table 4. The characteristic line 106 corresponds to the torque of the terminal 32 connected to the idler gear 28B during torque boost. Since the decrease in the torque (characteristic line 106) of the terminal 32 connected to the idler gear 28B can be suppressed, the decrease in the torque (characteristic line 107) of the idler gear 28B can also be suppressed according to the above-mentioned formula 13. The characteristic line 107 corresponds to the torque of the idler gear 28B during torque boost. Due to the above-mentioned action, even when the gear ratio is low (less than 0.5), the decrease in the torque of the idler gear 28B can be suppressed by performing the torque boost control. Terminal 32 coupled to idler gear 28B is connected to output shaft 23 via idler gear 28B and multi-speed mechanism 26, thereby preventing a decrease in torque of output shaft 23. As a result, transmission 21 can prevent a decrease in the tractive force of wheel loader 1 even when the vehicle speed is 0 to 5 km / h, thereby improving excavation capacity.

[0113] 10, when the gear ratio is 0.5 or more, the torque of the first variator 33 is a constant value. This is because the torque of the first variator 33 is limited, or the torque supplied from the power source (engine 9) is limited. The torque that the power source can supply varies depending on the rotation speed of the power source and the load for moving the loading machine 7, so the torque of the first variator 33 does not necessarily have to be constant.

[0114] The gear ratio at which the torque boost control intervenes occurs when the second variator 34 cannot fully receive the power generated by the first variator 33, and varies depending on the first variator 33 and the torque capacity of the first variator 33, the gear speed ratio of the planetary gear mechanism 29, the reduction ratio between the terminal 30 connected to the first variator 33 and the terminal 32 connected to the idler gear 28B, and the gear ratio of the transmission 39. In other words, the gear ratio is not limited to 0.5, but falls within the range of 0.1 to 2.0.

[0115] In the first embodiment (No. 1-A in Table 4) shown in FIG. 4, when the torque of the first variator 33 is increased, the torque of the terminal 30 connected to the first variator 33 increases, and the torque of the first sun gear 29B increases. In proportion to the torque of the first sun gear 29B, the torque of the second sun gear 29C (terminal 32 connected to the idler gear 28B) and the torque of the carrier 29A (second connecting member 31 connected to the engine 9, also called terminal 31 connected to the power source) increase. For example, when the gear ratio is 0.5 (corresponding to a vehicle speed of 2 to 5 km / h), the power absorbing device 38 is configured in consideration of the power that the second variator 34 can receive when the first variator 33 is relative to the second variator 34.

[0116] When the torque of the first variator 33 is increased to a predetermined value or more at a speed ratio of less than 0.5, the output torque of the second variator 34 is at a maximum value, so that the second variator 34 cannot absorb all of the power output by the first variator 33. For this reason, a power absorbing device 38 is provided between the first variator 33 and the second variator 34, and the capacity and specifications of the power absorbing device 38 are set in consideration of the amount of power absorption so that the torque of the first variator 33 can be increased, so that the torque of the second sun gear 29C (terminal 32 connected to the idler gear 28B) can be increased. As a result, according to the above formula (13), the torque of the idler gear 28B at a speed ratio of less than 0.5 (corresponding to a vehicle speed of 2 to 5 km / h) can be increased. The terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-stage transmission mechanism 26, so that the torque of the output shaft 23 can be increased. As a result, the transmission 21 can increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 can be increased.

[0117] In a fourth modified example (No. 1-B in Table 4) shown in FIG. 24, when the torque of the first variator 33 is increased, the torque of the terminal 30 connected to the first variator 33 increases, and the torque of the carrier 29A increases. In proportion to the torque of the carrier 29A, the torque of the second sun gear 29C (terminal 32 connected to the idler gear 28B) and the torque of the first sun gear 29B (terminal 31 connected to the engine 9) increase. For example, at a gear ratio of 0.5 (corresponding to a vehicle speed of 2 to 5 km / h), the torque of either the first variator 33 or the second variator 34 constitutes the power absorbing device 38 based on the maximum value that can be absorbed or output.

[0118] When the speed ratio is less than 0.5, the torque of the first variator 33 or the second variator 34 is at a maximum value, and therefore the torque of the first variator 33 cannot be increased any more. For this reason, the power absorbing device 38 is provided between the first variator 33 and the second variator 34, and the torque of the first variator 33 can be increased, thereby increasing the torque of the second sun gear 29C (the terminal 32 connected to the idler gear 28B). As a result, according to the above formula (13), the torque of the idler gear 28B can be increased when the speed ratio is less than 0.5 (corresponding to a vehicle speed of 2 to 5 km / h). The terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-stage transmission mechanism 26, and therefore the torque of the output shaft 23 can be increased. As a result, the transmission 21 can increase the output torque when the vehicle speed is 0 to 5 km / h, and the traction force of the wheel loader 1 increases.

[0119] In a fifth modified example (No. 1-C in Table 4) shown in FIG. 25, when the torque of first variator 33 is increased, the torque of terminal 30 connected to first variator 33 increases, and the torque of second sun gear 29C increases. In proportion to the torque of second sun gear 29C, the torque of carrier 29A (terminal 32 connected to idler gear 28B) and the torque of first sun gear 29B (terminal 31 connected to engine 9) increase. For example, when the gear ratio is 0.5 (corresponding to a vehicle speed of 2 to 5 km / h), power absorbing device 38 is configured taking into consideration the power that the second variator 34 can receive when first variator 33 is relative to second variator 34.

[0120] When the torque of the first variator 33 is increased to a predetermined value or more at a speed ratio of less than 0.5, the output torque of the second variator 34 is at a maximum value, so that the second variator 34 cannot receive all of the power sent by the first variator 33. Therefore, the torque of the carrier 29A (terminal 32 connected to the idler gear 28B) can be increased by increasing the torque of the first variator 33 by the power absorbing device 38 between the first variator 33 and the second variator 34. As a result, according to the above formula 13, the torque of the idler gear 28B can be increased at a speed ratio of less than 0.5 (corresponding to a vehicle speed of 2 to 5 km / h). The terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, so that the torque of the output shaft 23 can be increased. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0121] Next, the power absorption device 38, which serves as a power storage source (power storage device) and / or a power disposal device, will be described. This is common to "No1-A", "No1-B", and "No1-C" in Table 4, and "No2-A", "No2-B", "No2-C", "No2-D", "No2-E", and "No2-F" in Table 6, which will be described later. In other words, the configuration of the power absorption device 38 is the same in the second embodiment and each modified example, which will be described later.

[0122] When the first variator 33 and the second variator 34 are electric motor-generators (electric motors, electric generators), the power absorption device 38 can be configured by a power storage device and a power control device. FIG. 11 shows an overview thereof. The first variator 33 and the second variator 34 are connected by a transmission element 35 that is an electric wiring. The power absorption device 38 is provided between the first variator 33 and the second variator 34. The power absorption device 38 includes a power control device 38A and a power storage device 38B. The power control device 38A transmits power in both directions between the first variator 33 and the second variator 34. When the power sent from the first variator 33 to the power control device 38A is larger than the power that the second variator 34 can absorb, the power control device 38A supplies a part of the power to the power storage device 38B. The power absorption device 38 may be configured to include a resistance device (electrical resistance) instead of the power storage device 38B, or may be configured to include both the power storage device 38B and a resistance device (electrical resistance).

[0123] When the first variator 33 and the second variator 34 are hydraulic pump-motors (hydraulic pumps, hydraulic motors), the power absorbing device 38 can be configured with a relief valve or an accumulator. Fig. 12 shows a case where the power absorbing device 38 is configured with relief valves 38C, 38D. The first variator 33 and the second variator 34 are connected by a pair of main lines 35A, 35B which serve as the transmission element 35. That is, the pair of main pipes 35A, 35B connect the first variator 33 and the second variator 34 to each other.The pair of relief valves 38C, 38D are provided at a position where a pair of main lines 35A, 35B that connect the first variator 33 and the second variator 34 are connected. That is, one main line 35A and the other main line 35B are connected by a connecting line 35C, and the relief valves 38C, 38D are provided in the connecting line 35C together with the check valves 35D, 35E. The relief valves 38C, 38D and the check valves 35D, 35E are provided opposite each other so that relief can be provided in both directions between the main lines 35A, 35B. When the relief valve 38C on one main line 35A side relieves, the hydraulic oil flows through the opposing check valve 35E to the other main line 35B on the opposite side. The relief pressure of the relief valves 38C, 38D can be fixed or changed by a signal from the controller 25. The effect of the configuration in which the relief start pressure of the relief valves 38C, 38D is variable will be described.

[0124] First, Fig. 13 shows the relationship between the pressure in the high-pressure side main line 35A (characteristic line 111), the relief start pressure of the relief valve 38C (characteristic line 112), and the withstand pressure of the first variator 33, the second variator 34, or the main lines 35A and 35B (characteristic line 113) when the relief start pressures of the relief valves 38C and 38D are fixed. In Fig. 13, characteristic line 114 corresponds to the theoretical discharge volume of the first variator 33 (hydraulic pump / motor), and characteristic line 115 corresponds to the theoretical discharge volume of the second variator 34 (hydraulic pump / motor). When the controller 25 increases the discharge volume of the first variator 33 and supplies a flow rate greater than the capacity of the second variator 34 to be received by the first variator 33, the pressure in one main line 35A rises to or exceeds the relief start pressure, and the relief valve 38C operates. As a result, hydraulic oil flows into the other main line 35B. At this time, the pressure in one main line 35A temporarily rises (surges) above the relief start pressure. This is because it takes a certain amount of time for the relief valve 38C to respond to the operation. Since there is an upper limit to the withstand pressure of the first variator 33, the second variator 34, or the main lines 35A and 35B, the relief start pressure of the relief valves 38C and 38D needs to be set low in anticipation of a surge. For this reason, it is necessary to set the relief start pressure of the relief valves 38C and 38D to about 80% to 85% of the withstand pressure upper limit, which may reduce the maximum output torque of the second variator 34.

[0125] Therefore, in the embodiment, the relief start pressure of the relief valves 38C, 38D is configured to be changeable. Fig. 14 shows the relationship between the pressure of the high pressure side main line 35A (characteristic line 116), the relief start pressure of the relief valves 38C, 38D (characteristic line 117), and the withstand pressure of the first variator 33, the second variator 34, or the main lines 35A, 35B (characteristic line 113) in the case where the relief start pressure of the relief valves 38C, 38D is changeable. The controller 25 sets the relief start pressure of the relief valves 38C, 38D to about 80% to 85% of the withstand pressure before the relief valves 38C, 38D operate. This relief start pressure is defined as the first relief start pressure. Thereafter, when the discharge volume of the first variator 33 is increased and the first variator 33 supplies a flow rate that is greater than the flow rate that the second variator 34 can receive, the pressure in one main line 35A rises to or above the first relief start pressure, and the relief valve 38C operates, causing the hydraulic oil to flow to the other main line 35B. At this time, the pressure in one main line 35A temporarily rises (surges) to or above the first relief start pressure, but since the first relief start pressure of the relief valve 38C is kept low at about 80% to 85% of the upper limit of the withstand pressure, it is possible to control the pressure so that it does not exceed the withstand pressure.

[0126] After the relief valve 38C starts to relieve, the controller 25 sends a signal to the relief valve 38C to increase the relief start pressure so that the set pressure of the relief valve 38C becomes higher. This relief start pressure is defined as the second relief start pressure. The controller 25 detects the start of relief by the relief valve 38C from the value (detection value) of the pressure detectors 35F, 35G (hereinafter referred to as the pressure sensors 35F, 35G) that detect the hydraulic pressure (pressure) of the main lines 35A, 35B, or from the relationship between the theoretical discharge volume and the rotation speed of the first variator 33 and the second variator 34. That is, the controller 25 detects from the detection value of the pressure sensor 35F, etc. that the relief valve 38C has started to perform the relief operation due to an increase in the load caused by excavation or the like (an increase in the output torque of the transmission 21) and an increase in the pressure of the main line 35A.

[0127] Furthermore, the controller 25 detects, from the detection value of the pressure sensor 35F, that the relief of the relief valve 38C has stopped due to a decrease in the load caused by excavation or the like (a decrease in the output torque of the transmission 21) and a decrease in the pressure in the main pipe 35A. After detecting the end of the relief operation of the relief valve 38C, the controller 25 immediately reduces the relief setting pressure of the relief valve 38C from the second relief start pressure. This makes it possible to increase the maximum value of the output torque of the transmission 21 within the withstand pressure range, even if the output torque of the transmission 21 fluctuates. Through the above control, it becomes possible to use the second variator 34 within the limits of the withstand pressure, and by increasing the output torque of the second variator 34, the traction force of the wheel loader 1 can be increased.

[0128] 15 shows a case where the power absorbing device 38 is configured with accumulators 38E, 38F. The power absorbing device 38 has two accumulators 38E, 38F, that is, a high-pressure side accumulator 38E and a low-pressure side accumulator 38F. Between each of the accumulators 38E, 38F and each of the main lines 35A, 35B, there are provided switching valves 38G, 38H for storing pressure, which switch between connection (communication) and cutoff (disconnection) between the respective accumulators 38E, 38F and the respective main lines 35A, 35B. As a result, the high pressure side accumulator 38E and the low pressure side accumulator 38F are connected to the pair of main lines 35A, 35B via changeover valves 38G, 38H that communicate with or block communication therebetween. The high-pressure side accumulator 38E is an accumulator that absorbs power. The high-pressure side accumulator 38E stores power and releases the stored power. The pressure at which the high-pressure side accumulator 38E starts accumulating is, for example, in the range of 25 MPa to 45 MPa.

[0129] The low-pressure side accumulator 38F serves as a reservoir for hydraulic fluid that is supplied to and discharged from the high-pressure side accumulator 38E. The pressure at which the low-pressure side accumulator 38F starts accumulating is, for example, in the range of 2.0 MPa to 3.0 MPa. When accumulating pressure in the high-pressure side accumulator 38E, hydraulic oil is supplied from the low-pressure side accumulator 38F to the main line 35A (35B), so the flow rate of hydraulic oil passing through the first variator 33 is smaller than that of hydraulic oil passing through the second variator 34.

[0130] In Fig. 15, when storing power in one (upper in Fig. 15) main line 35A of the pair of main lines 35A, 35B, the spool of one (upper in Fig. 15) switching valve 38G is moved to the left to connect the high-pressure side accumulator 38E to one main line 35A. This allows hydraulic oil to flow from one main line 35A to the high-pressure side accumulator 38E. Meanwhile, the other (lower in Fig. 15) switching valve 38H has its spool moved to the left to connect the low-pressure side accumulator 38F to the other (lower in Fig. 15) main line 35B. As a result, hydraulic oil flows from one main line 35A to the high-pressure side accumulator 38E via one changeover valve 38G, and hydraulic oil is supplied from the low-pressure side accumulator 38F to the other main line 35B via the other changeover valve 38H.

[0131] When the pressure accumulated in the high-pressure side accumulator 38E is to be released to one of the main lines 35A, the spool of one of the switching valves 38G is moved to the left to connect the high-pressure side accumulator 38E to one of the main lines 35A. As a result, hydraulic oil flows from the high-pressure side accumulator 38E to one of the main lines 35A. Meanwhile, the spool of the other switching valve 38H moves to the left to connect the low-pressure side accumulator 38F to the other of the main lines 35B. As a result, hydraulic oil is supplied to the low-pressure side accumulator 38F from the other of the main lines 35B via the other switching valve 38H.

[0132] When storing power in the other main line 35B, the spool of one of the switching valves 38G is moved to the right to connect the high-pressure side accumulator 38E to the other main line 35B. This allows hydraulic oil to flow from the other main line 35B to the high-pressure side accumulator 38E. Meanwhile, the spool of the other switching valve 38H moves to the right to connect the low-pressure side accumulator 38F to one of the main lines 35A. This allows hydraulic oil to flow from the other main line 35B to the high-pressure side accumulator 38E via one of the switching valves 38G, and hydraulic oil is supplied from the low-pressure side accumulator 38F to one of the main lines 35A via the other switching valve 38H.

[0133] When the pressure accumulated in the high-pressure accumulator 38E is to be released to the other main line 35B, the spool of one of the switching valves 38G is moved to the right to connect the high-pressure accumulator 38E to the other main line 35B. As a result, hydraulic oil flows from the high-pressure accumulator 38E to the other main line 35B. Meanwhile, the spool of the other switching valve 38H moves to the right to connect the low-pressure accumulator 38F to the one main line 35A. As a result, hydraulic oil is supplied to the low-pressure accumulator 38F from the one main line 35A via the other switching valve 38H. These operations enable the storage and release of power between the first variator 33 and the second variator 34.

[0134] Next, the internal lockup operation of the planetary continuously variable transmission mechanism 24 will be described. The planetary continuously variable transmission mechanism 24 has a power transmission efficiency of 80 to 93%, which is high for a continuously variable transmission. In contrast, for example, the power transmission efficiency of a gear transmission in which a pair of gears mesh with each other is about 99%. For this reason, the planetary continuously variable transmission mechanism 24 has a lower power transmission efficiency than a transmission in which a pair of gears mesh with each other. The reason for this will be described with reference to FIG. 3.

[0135] That is, consider the power transmission efficiency between the planetary gear mechanism 29 and the idler element 28 (idler gear 28B). Here, the power transmission path via the first connecting member 30, the first variator 33, the transmission element 35, the second variator 34, the transmission 39, and the third clutch 37 has a transmission efficiency of about 70 to 80%. In contrast, the power transmission path via the third connecting member 32 has a transmission efficiency of about 99%. For this reason, in order to increase the transmission efficiency, the rotation of the first connecting member 30 connected to the first variator 33 may be stopped so that power transmission is not performed between the first variator 33 and the second variator 34. As a result, the power supplied from the engine 9 to the planetary gear mechanism 29 through the second connecting member 31 is not distributed to the first connecting member 30 connected to the first variator 33, but is entirely transmitted to the third connecting member 32 connected to the idler element 28 (idler gear 28B).

[0136] Because power is transmitted between the third connecting member 32 and the idler gear 28B by meshing of the gears, power supplied from the engine 9 to the planetary gear mechanism 29 through the second connecting member 31 can be transmitted to the idler gear 28B with high efficiency. This improves the power transmission efficiency of the planetary continuously variable transmission mechanism 24 to approximately 97%, improving the transmission efficiency of the transmission 21. As a result, the wheel loader 1 can be made more fuel-efficient.

[0137] When the planetary continuously variable transmission mechanism 24 is in an internal lockup operation, the planetary continuously variable transmission mechanism 24 has a fixed speed ratio. If the internal lockup speed ratio is In, the internal lockup speed ratio In can be expressed by the following equation 14. The rotational speed of the third connecting member 32 is "V32", the rotational speed of the second connecting member 31 is "V31", and the rotational speed of the first connecting member 30 is "V30".

[0138]

number

[0139] The above-mentioned formula 8 holds even during internal lockup operation. Therefore, the internal lockup speed ratio In can be calculated by substituting the rotation speed of first connecting member 30 linked to first variator 33 as 0 into formula 8. For example, in the first embodiment (No. 1-A in Table 4), the rotation speed Vs1 of first sun gear 29B connected to first connecting member 30 is substituted as 0 into formula 8. That is, the internal lockup speed ratio In is given by the following formula 15.

[0140]

number

[0141] In the fourth modified example (No. 1-B in Table 4) shown in Fig. 24, Equation 8 is modified and the rotation speed Vc of the carrier 29A connected to the first connecting member 30 is substituted as 0. That is, the internal lockup speed ratio In is expressed by the following Equation 16.

[0142]

number

[0143] In a fifth modified example (No. 1-C in Table 4) shown in FIG. 25, the rotation speed Vs2 of second sun gear 29C connected to first connecting member 30 is substituted as 0 into equation 8. That is, the internal lockup speed ratio In is expressed by the following equation 17.

[0144]

number

[0145] In this way, the internal lockup speed ratio In depends on the gear combination of the planetary gear mechanism 29 and Ka. In order to put the planetary continuously variable transmission mechanism 24 into an internal lockup state, it is sufficient to stop rotation of the first connecting member 30 connected to the first variator 33, among the three connecting members 30, 31, 32 connected to the planetary gear mechanism 29. When the first variator 33 and the second variator 34 are hydraulic pump-motors, the controller 25 maintains the volume of the hydraulic pump-motor of the first variator 33 at or above a predetermined volume (preferably at or above 10% of the maximum volume), and controls the volume of the hydraulic pump-motor of the second variator 34 to zero.

[0146] In order to stop the rotation of the first connecting member 30, for example, as in a first modified example shown in Fig. 19, a configuration in which a blocking mechanism 40 is provided in a transmission element 35 that transmits power between the first variator 33 and the second variator 34 may be adopted. The blocking mechanism 40 is controlled by the controller 25 to interrupt the power transmission between the first variator 33 and the second variator 34.

[0147] For example, when the power transmission of the transmission element 35 is performed by hydraulic pressure, the block mechanism 40 can be configured by a hydraulic valve. The controller 25 sends a signal to the block mechanism 40 to cut off the flow of oil between the first variator 33 and the second variator 34. When the power transmission between the first variator 33 and the second variator 34 is performed by electricity, the block mechanism 40 can be configured by an inverter / converter. In this case, the inverter / converter applies a pseudo resistance between the power lines to increase the voltage between the power lines. The block mechanism 40 may be configured to cut off the flow of power by a magnet contactor or to apply resistance between the power lines by a resistor. In either case, the controller 25 sends a signal to the block mechanism 40 to transmit and cut off the power, and controls the block mechanism 40.

[0148] The internal lockup state may be realized by fixing the rotating shaft of the first variator 33 to a non-rotating part and stopping the rotation of the first variator 33. For example, as in a second modified example shown in FIG. 20 and a third modified example shown in FIG. 21, the internal lockup state may be realized by fixing the first connecting member 30 to a non-rotating part (for example, the case of the transmission 21) by a brake mechanism 41. The brake mechanism 41 may be configured to fix the first connecting member 30 connected to the first variator 33 to the non-rotating part by frictional coupling or mechanical meshing coupling. In particular, when the first variator 33 is a generator, it is necessary to pass a current through the first variator 33 (generator) even during the internal lockup operation. For this reason, from the viewpoint of power loss, it is desirable to fix the first connecting member 30 to the non-rotating part by the brake mechanism 41. That is, when the first variator 33 is a generator, it is desirable to fix the first connecting member 30 to the non-rotating part by the brake mechanism 41 from the viewpoint of power loss. This makes it possible to improve the power transmission of the planetary continuously variable transmission mechanism 24 during internal lockup, thereby making the wheel loader 1 more fuel efficient.

[0149] The first to third modified transmissions 21A, 21B, and 21C shown in Figs. 19 to 21 can perform an internal lockup operation of the planetary continuously variable transmission mechanism 24, but are not provided with an external lockup mechanism (direct drive mechanism 27). In the case of such transmissions 21A, 21B, and 21C, the planetary continuously variable transmission mechanism 24 is infinitely variable to transmit power during starting and excavation, and the planetary continuously variable transmission mechanism 24 is internally locked up to transmit power during transportation and forwarding. As a result, during starting and excavation (vehicle speed 0 to 7 km / h) when infinitely variable transmission is required, the power transmission efficiency can be improved by infinitely variable fluctuation by the planetary continuously variable transmission mechanism 24. On the other hand, during transportation and forwarding (vehicle speed 7 km / h or more) when infinitely variable transmission is not required, the planetary continuously variable transmission mechanism 24 is internally locked up to perform transmission efficiency even higher than that of infinitely variable transmission. This enables the wheel loader 1 to be fuel efficient.

[0150] Next, the direct drive mechanism 27, which is an external lockup mechanism, will be described with reference to FIG. 3. The direct drive mechanism 27 transmits the power supplied from the engine 9 to the idler gear 28B by meshing of gears without passing through the planetary type continuously variable transmission mechanism 24. The power transmission efficiency of the direct drive mechanism 27 is about 99%, which improves the transmission efficiency of the transmission 21 and enables the wheel loader 1 to be fuel-efficient. The direct drive mechanism 27 includes an input gear 27A provided on the input shaft 22, a lockup gear 27B meshing with the input gear 27A, and a first clutch 27C. The rotating shaft 27B1 provided with the lockup gear 27B is connected to the idler shaft 28A of the idler element 28 via the first clutch 27C. The first clutch 27C is configured, for example, by a clutch (friction plate) by frictional connection, a dog clutch, or a dog clutch with synchromesh. The first clutch 27C mechanically couples (connects) and disengages the lockup gear 27B and the idler gear 28B. By disengaging the second clutch 36 and engaging the first clutch 27C, the power input from the input shaft 22 is transmitted to the idler gear 28B via the input gear 27A, the lockup gear 27B, and the first clutch 27C. This allows the power supplied from the engine 9 to be transmitted to the idler gear 28B via the direct drive mechanism 27, which is an external lockup mechanism, without passing through the planetary type continuously variable transmission mechanism 24.

[0151] Due to the characteristics of the planetary gear mechanism 29 of the speed relation line Y1 shown in Fig. 7, the planetary type continuously variable transmission mechanism 24 can increase the speed of the third connecting member 32 connected to the idler gear 28B relative to the second connecting member 31 connected to the power source (engine 9). In order to effectively use the speed increase range of the planetary type continuously variable transmission mechanism 24, it is preferable to increase the speed of the power transmission via the direct drive mechanism 27. Here, when the rotation speeds of the first connecting member 30 connected to the first variator 33 and the third connecting member 32 connected to the idler gear 28B among the three connecting members 30, 31, 32 connected to the planetary gear mechanism 29 are the same, the rotation speeds of the second connecting member 31 connected to the engine 9 and the third connecting member 32 connected to the idler gear 28B become the same.

[0152] At this time, the rotational speed of the idler gear 28B is expressed by the following formula 18. Note that the rotational speed of the idler gear 28B is "V28B", the rotational speed of the second connecting member 31 connected to the engine 9 is "V31", the number of teeth of the third connecting member 32 connected to the idler gear 28B is "N32", and the number of teeth of the idler gear 28B is "N28B".

[0153]

number

[0154] Here, the synchronous rotation speed ratio Id is defined as in the following formula 19. Note that the number of teeth of the third connecting member 32 is "N32", and the number of teeth of the idler gear 28B is "N28B".

[0155]

number

[0156] Moreover, the external lockup rotation speed ratio Ir is defined as the following formula 20. Note that the number of teeth of the input gear 27A is "N27A", and the number of teeth of the lockup gear 27B is "N27B".

[0157]

number

[0158] In this case, by making the external lockup rotation speed ratio Ir larger than the synchronous rotation speed ratio Id, the speed increase range of the planetary continuously variable transmission mechanism 24 can be effectively used. For example, in the case of a transmission device 21 that has an external lockup but does not perform an internal lockup operation, power is transmitted as follows. That is, when starting and excavating (vehicle speed 0 to 7 km / h) when infinitely variable speed is required, power is transmitted via the planetary continuously variable transmission mechanism 24. When transporting and driving (vehicle speed 7 km / h or more) when infinitely variable speed is not required, power is transmitted via the external lockup mechanism (direct-coupled mechanism 27).

[0159] On the other hand, in the case of the transmission 21 that is equipped with an external lockup mechanism (direct-coupled mechanism 27) and performs an internal lockup operation, it is preferable that the external lockup rotation speed ratio Ir satisfies the relationship of the following formula (21).

[0160]

number

[0161] As a result, when starting and excavating (vehicle speed 0 to 7 km / h) which require infinitely variable speed, power is transmitted while infinitely variable speed is being changed via the planetary type infinitely variable speed mechanism 24. When transporting and deadheading (vehicle speed 7 km / h or more) which do not require infinitely variable speed, power is transmitted via the planetary type infinitely variable speed mechanism 24 while operating the internal lockup. When transporting and deadheading (vehicle speed 10 km / h or more) which do not require infinitely variable speed, power is transmitted via the external lockup mechanism (direct drive mechanism 27). As a result, the transmission 21 can select the power transmission path with the highest power transmission efficiency during all operations of excavation, starting, transporting, and deadheading. As a result, the wheel loader 1 can be made fuel-efficient.

[0162] Next, the multi-speed mechanism 26 will be described. The multi-speed mechanism 26 is a transmission mechanism that changes speed by meshing gears, switching the clutch, and switching the brake. The multi-speed mechanism 26 corresponds to, for example, a planetary transmission, a countershaft type transmission, a manual transmission, an automated manual transmission, a dual clutch transmission, and the like. In the first embodiment, the multi-speed mechanism 26 is configured by a dual clutch transmission with four forward speeds and one reverse speed. In contrast, in the first modified example shown in FIG. 19, the second modified example shown in FIG. 20, and the third modified example shown in FIG. 21, the multi-speed mechanism 26A is configured by a dual clutch transmission with five forward speeds and two reverse speeds. Note that the multi-speed mechanisms 26 and 26A are not limited to these configurations, and for example, one to sixteen forward speeds can be assumed, and one to eight reverse speeds can be assumed.

[0163] The multi-speed mechanism 26, which is a dual clutch transmission, will be described with reference to Fig. 16. The multi-speed mechanism 26 includes an odd-numbered shaft 51, an even-numbered shaft 52, an output shaft 53, and a counter gear 54. The output shaft 53 of the multi-speed mechanism 26 also corresponds to the output shaft 23 of the transmission 21. The odd-numbered shaft 51 includes an odd-numbered gear 55, a forward first-speed gear 56, a forward third-speed gear 57, a fourth clutch 58 as a first output clutch, a sixth clutch 59, an eighth clutch 60, and an odd-numbered shaft 61. The even shaft 52 is configured to include an even-speed gear 62, a forward second-speed gear 63, a forward fourth-speed gear 64, a reverse first-speed gear 65, a fifth clutch 66 as a second output clutch, a seventh clutch 67, a tenth clutch 68, a ninth clutch 69, and an even-speed shaft 70.

[0164] The counter gear 54 is a gear for reversing the rotation direction of the output shaft 53. The output shaft 53 is configured to include a forward first speed output gear 71, a forward second speed output gear 72, a forward third speed output gear 73, a forward fourth speed output gear 74, and a reverse first speed output gear 75. The even-numbered gear 62 and the odd-numbered gear 55 are constantly meshed with the idler gear 28B and rotate together with the idler gear 28B. In addition, the forward first speed gear 56 and the forward first speed output gear 71, the forward second speed gear 63 and the forward second speed output gear 72, the forward third speed gear 57 and the forward third speed output gear 73, and the forward fourth speed gear 64 and the forward fourth speed output gear 74 are constantly meshed with each other. In addition, the reverse first speed gear 65, the counter gear 54, and the reverse first speed output gear 75 are also constantly meshed with each other. The fourth clutch 58 couples (fastens) and disengages the odd-numbered gear 55 and the odd-numbered shaft 61. The odd-numbered gear 55 and the odd-numbered shaft 61 are coupled by the fourth clutch 58, thereby enabling power transmission between the idler gear 28B and the odd-numbered shaft 61. The fifth clutch 66 couples (fastens) and disengages the even-numbered gear 62 and the even-numbered shaft 70. The even-numbered gear 62 and the even-numbered shaft 70 are coupled by the fifth clutch 66, thereby enabling power transmission between the idler gear 28B and the even-numbered shaft 70.

[0165] The sixth clutch 59 couples (fastens) and releases the first forward gear 56 and the odd-numbered shaft 61. The sixth clutch 59 couples the first forward gear 56 and the odd-numbered shaft 61, thereby enabling power transmission between the output shaft 53 and the odd-numbered shaft 61. The eighth clutch 60 couples the third forward gear 57 and the odd-numbered shaft 61, thereby enabling power transmission between the output shaft 53 and the odd-numbered shaft 61. The seventh clutch 67 couples the second forward gear 63 and the even-numbered shaft 70, thereby enabling power transmission between the output shaft 53 and the even-numbered shaft 70. The tenth clutch 68 couples the fourth forward gear 64 and the even-numbered shaft 70, thereby enabling power transmission between the output shaft 53 and the even-numbered shaft 70. The ninth clutch 69 connects the first reverse gear 65 and the even-stage shaft 70, thereby enabling power transmission between the output shaft 53 and the even-stage shaft 70. The sixth clutch 59, the seventh clutch 67, the eighth clutch 60, the ninth clutch 69, and the tenth clutch 68 are each configured as a dog clutch or a dog clutch with a synchromesh.

[0166] Next, the operation of the multi-speed mechanism 26 will be described. In order to transmit the power input to the idler gear 28B to the output shaft 53 in the first forward speed, the fourth clutch 58 is engaged, the fifth clutch 66 is disengaged, the sixth clutch 59 is engaged, and the eighth clutch 60 is disengaged. In this state, any two or more of the seventh clutch 67, the tenth clutch 68, and the ninth clutch 69 are disengaged. The first forward speed corresponds to No. 1 to No. 4 in Table 5 described later.

[0167] To transmit power to the output shaft 53 in the second forward speed, the fifth clutch 66 and the seventh clutch 67 are engaged, and the fourth clutch 58, the tenth clutch 68 and the ninth clutch 69 are disengaged. In this state, either or both of the sixth clutch 59 and the eighth clutch 60 are disengaged. The second forward speed corresponds to No. 9 to No. 11 in Table 5 described later.

[0168] To transmit power to the output shaft 53 in the third forward gear, the fourth clutch 58 and the eighth clutch 60 are engaged, and the fifth clutch 66 and the sixth clutch 59 are disengaged. In this state, any two or more of the seventh clutch 67, the tenth clutch 68, and the ninth clutch 69 are disengaged. The third forward gear corresponds to No. 5 to No. 8 in Table 5 described later.

[0169] To transmit power to the output shaft 53 in the fourth forward speed, the fifth clutch 66 and the tenth clutch 68 are engaged, and the fourth clutch 58, the seventh clutch 67 and the ninth clutch 69 are disengaged. In this state, either or both of the sixth clutch 59 and the eighth clutch 60 are disengaged. The fourth forward speed corresponds to No. 12 to No. 14 in Table 5 described later.

[0170] To transmit power to the output shaft 53 in the first reverse gear, the fifth clutch 66 and the ninth clutch 69 are engaged, and the fourth clutch 58, the seventh clutch 67 and the tenth clutch 68 are disengaged. In this state, either or both of the sixth clutch 59 and the eighth clutch 60 are disengaged. The first reverse gear corresponds to No. 15 to No. 17 in Table 5 described later.

[0171] When power is being transmitted from the idler gear 28B to the output shaft 53 through the odd-numbered shaft 51, the seventh clutch 67, the tenth clutch 68 and the ninth clutch 69 can be switched between engagement and release. This allows any one of the forward second gear 63, the forward fourth gear 64 and the reverse first gear 65 to be pre-coupled to the even-numbered shaft 70. Similarly, when power is being transmitted from the idler gear 28B to the output shaft 53 through the even-numbered shaft 52, the sixth clutch 59 and the eighth clutch 60 can be switched between engagement and release. This allows any one of the forward first gear 56 and the forward third gear 57 to be pre-coupled to the odd-numbered shaft 61.

[0172] Power transmission from the idler gear 28B to the output shaft 53 can be switched from via the odd-numbered stage shaft 61 to via the even-numbered stage shaft 70 by disengaging the fourth clutch 58 and engaging the fifth clutch 66 from a state in which the fourth clutch 58 is engaged and the fifth clutch 66 is disengaged. Similarly, power transmission from the idler gear 28B to the output shaft 53 can be switched from via the even-numbered stage shaft 70 to via the odd-numbered stage shaft 61 by engaging the fourth clutch 58 and disengaging the fifth clutch 66 from a state in which the fourth clutch 58 is disengaged and the fifth clutch 66 is engaged.

[0173] However, the switching of the engagement of the fourth clutch 58 and the fifth clutch 66 does not necessarily have to be performed alternately. For example, as shown in Table 5 below, there is a switching from No. 1 to 4 to No. 5 to 8, and a switching from No. 5 to 8 to No. 1 to 4. In this case, after the fourth clutch 58 is released, the sixth clutch 59 and the eighth clutch 60 are engaged or released. After that, the released fourth clutch 58 is engaged. In addition, there is a switching from No. 9 to 11 to No. 12 to 14, a switching from No. 12 to 14 to No. 9 to 11, a switching from No. 9 to 11 to No. 15 to 17, a switching from No. 15 to 17 to No. 9 to 11, a switching from No. 12 to 14 to No. 15 to 17, and a switching from No. 15 to 17 to No. 12 to 14. In this case, after the fifth clutch 66 is released, the seventh clutch 67, the tenth clutch 68, and the ninth clutch 69 are engaged or released. Thereafter, the fifth clutch 66, which has been released, is engaged.

[0174] [Table 5]

[0175] When the wheel loader 1 performs a V-cycle mainly for dumping gravel or the like, the vehicle moves forward to excavate gravel or the like, and then moves backward to move toward the dump. At this time, a specific example of the first embodiment (i.e., No. 1-A in Table 4) will be described. The planetary type continuously variable transmission mechanism 24 can reverse the rotation direction of the third connecting member 32 connected to the idler gear 28B by controlling the rotation speed of the first connecting member 30 connected to the first variator 33 according to the relationship of the speed relationship line Y1 of the planetary gear mechanism 29 shown in FIG. 7. However, when the rotation direction of the second sun gear 29C is reversed relative to the rotation direction of the first sun gear 29B (i.e., when controlled in the lower right direction in FIG. 7), the rotation speed of the first sun gear 29B becomes high. Similarly, when the rotation direction of first sun gear 29B is reversed relative to the rotation direction of second sun gear 29C (when controlled to the upper left direction in FIG. 7), the rotation speed of second sun gear 29C increases.

[0176] In such a case, the first variator 33 connected to the first connecting member 30 must have a higher maximum rotation speed limit. For this reason, rotating the first connecting member 30 connected to the first variator 33 at high speed and reversing the rotation direction of the third connecting member 32 connected to the idler gear 28B from forward rotation means adopting an expensive first variator 33 with a high maximum rotation speed. This may increase the cost of the planetary type continuously variable transmission mechanism 24. For this reason, when the wheel loader 1 moves backward, it is desirable to use the multi-speed transmission mechanism 26 and reverse the rotation direction of the output shaft 53 (output shaft 23) from the forward direction to the reverse direction. This makes it possible to reduce the rotation speed of the first variator 33 connected during reverse rotation, allowing the use of an inexpensive first variator 33. While the first embodiment (i.e., No. 1-A in Table 4) has been given as an example, in the case of the fourth modified example (i.e., No. 1-B in Table 4) and the fifth modified example (i.e., No. 1-C in Table 4), similarly, by using the multi-speed mechanism 26 and switching the rotation direction of the output shaft 53 to switch between the forward direction and the reverse direction, it becomes possible to reduce the rotation speed of the first variator 33 connected during reverse rotation, and therefore it is possible to use a less expensive first variator 33.

[0177] As described above, according to the first embodiment, the transmission 21 includes the input shaft 22 (input member) connected to the power source (engine 9), the output shaft 23 (output member) connected to the load (front axle 12, rear axle 13), the planetary gear mechanism 29 (planetary mechanism) provided between the input shaft 22 and the output shaft 23, the first variator 33 connected to the planetary gear mechanism 29, the second variator 34 provided separately from the first variator 33, and the controller 25 that changes the rotation speed of the first variator 33. The planetary gear mechanism 29 includes three members (rotating members): the carrier 29A, the first sun gear 29B (first sun member) that rotates about the rotation center axis of the carrier 29A, and the second sun gear 29C (second sun member) that rotates about the rotation center axis of the carrier 29A.

[0178] In this case, for example, as shown in FIG. 4 and FIG. 5, carrier 29A, which is the first member of the three members, is connected to input shaft 22 via second connecting member 31 (another member). First sun gear 29B, which is the second member different from carrier 29A, is connected to first variator 33 via first connecting member 30 and second clutch 36 (all other members). Second sun gear 29C, which is the third member different from carrier 29A and first sun gear 29B, is connected to output shaft 23 via third connecting member 32, idler element 28, and multi-stage transmission mechanism 26 (all other members). Carrier 29A (first member) may be directly connected to input shaft 22. First sun gear 29B (second member) may be directly connected to first variator 33. Second sun gear 29C (third member) may be directly connected to output shaft 23.

[0179] Here, carrier 29A supports planet gears 29D (planet member) that transmit power while revolving around rotation center axis S of carrier 29A and rotating with first sun gear 29B and second sun gear 29C, and balance gear 29E (balance member) that serves as a counter gear. Planetary gear mechanism 29 distributes torque transmitted from engine 9 to carrier 29A (first member) of planetary gear mechanism 29 to first sun gear 29B (second member) and second sun gear 29C (third member). Planetary gear mechanism 29 performs rotational motion with two degrees of freedom between carrier 29A, first sun gear 29B, and second sun gear 29C. The second variator 34 transmits the power transmitted from the first variator 33 to the load (output shaft 23) or the power source (input shaft 22), or transmits the power transmitted from the load (output shaft 23) or the power source (input shaft 22) to the first variator 33. The controller 25 changes the rotation speed of the output shaft 23 relative to the rotation speed of the input shaft 22 by changing the rotation speed of the first variator 33.

[0180] That is, the transmission 21 of the first embodiment performs stepless speed change by the planetary gear mechanism 29, and transmits power from a power source (input shaft 22) to a load (output shaft 23), or transmits power from the load (output shaft 23) to the power source (input shaft 22). In this case, the transmission 21 includes a planetary gear mechanism 29 provided between the input shaft 22 and the output shaft 23, a first variator 33 connected to the planetary gear mechanism 29, and a second variator 34 that transmits the power transmitted from the first variator 33 to the load or the power source. The planetary gear mechanism 29 includes a carrier 29A connected to the input shaft 22 and supporting a planet gear 29D and a balance gear 29E, a first sun gear 29B connected to the first variator 33, and a second sun gear 29C connected to the output shaft 23 via an idler element 28 and a multi-stage transmission mechanism 26. Furthermore, the transmission 21 is provided with at least one of an internal lockup and an external lockup (direct drive mechanism 27). The transmission 21 can switch between power transmission by the planetary continuously variable transmission mechanism 24 and power transmission by the lockup.

[0181] Furthermore, in the transmission 21 of the first embodiment, a power absorbing device 38 is provided between the second variator 34 and the first variator 33 to absorb power therebetween. The power absorbing device 38 changes the absorbed torque of the first variator 33 by the controller 25, and when power is generated that is greater than the second variator 34 can absorb, the power absorbing device 38 absorbs the power, thereby increasing the torque of the output shaft 23 that serves as the output member. For this reason, the power absorbing device 38 absorbs (disposes of or stores) the power that is greater than the second variator 34 can absorb, out of the power generated by the first variator 33, so that torque boost control can be performed to increase the torque of the output shaft 23. As a result, even if a small, inexpensive second variator 34 with a small maximum output torque is used, sufficient torque can be output from the output shaft 23. That is, even if the second variator 34 is a small, inexpensive one with a small maximum output torque, sufficient torque can be output from the output shaft 23 when traveling at a low vehicle speed. As a result, the traction force required for excavation by the wheel loader 1 can be sufficiently increased, and excavation can be carried out efficiently.

[0182] According to the first embodiment, the first variator 33 and the second variator 34 are configured by hydraulic pump-motors. The power absorbing device 38 is configured by at least one of relief valves 38C, 38D and accumulators 38E, 38F. When the first variator 33 and the second variator 34 are configured by electric motor-generators, the power absorbing device 38 may be configured by at least one of an electricity storage device 38B such as a battery and an electric resistance device such as a resistor. In either case, the torque of the output shaft 23 can be increased by absorbing (disposing of or storing) the power generated by the first variator 33 in excess of the power that the second variator 34 can receive by the power absorbing device 38.

[0183] According to the first embodiment, the relief valves 38C, 38D are capable of varying the relief start pressure in response to a signal from the controller 25. The controller 25 sends a signal of the first relief start pressure to the relief valve 38C before sending a command to the first variator 33 to generate power that is greater than the second variator 34 can absorb. In this case, the first relief start pressure is kept low to a value that has a margin relative to the upper limit of the withstand pressure (for example, a value of about 80% to 85% of the upper limit of the withstand pressure). Therefore, even if the pressure temporarily rises (surges) above the first relief start pressure due to the operation of the relief valve 38C when a command to generate power that is greater than the second variator 34 can absorb is sent to the first variator 33, this pressure can be prevented from exceeding the withstand pressure.

[0184] According to the first embodiment, the controller 25 sends a command to the first variator 33 to generate power greater than the power that the second variator 34 can absorb, and then sends a signal of a second relief start pressure higher than the first relief start pressure to the relief valve 38C. This makes it possible to suppress a decrease in the maximum output torque of the second variator 34. Furthermore, when the power sent by the second variator 34 to the first variator 33 decreases, the controller 25 lowers the signal of the relief start pressure to the second relief pressure or lower (or the first relief pressure or lower). This makes it possible to increase the maximum value of the output torque of the transmission 21 within the withstand pressure range, even if the output torque of the transmission 21 fluctuates.

[0185] According to the first embodiment, the transmission 21 is provided with the multi-speed mechanism 26, which is an auxiliary transmission mechanism. The second variator 34 is connected to an idler element (specifically, an idler gear 28B, which is a rotating element) provided between the planetary gear mechanism 29 and the multi-speed mechanism 26. As in a sixth modified example shown in FIG. 26, the second variator 34 may be connected to the output shaft 23 (output member). That is, as shown in FIGS. 41 to 50, which will be described later, the second variator 34 may be connected to a rotating element provided between the input shaft 22 (input member) and the drive source (engine 9), a rotating element constituting the multi-speed mechanism 26, a rotating element provided between the multi-speed mechanism 26 and the output shaft 23 (output member), the output shaft 23 (output member), or a rotating element provided between the output shaft 23 and a load.

[0186] Next, Figures 27 to 30 show a second embodiment. The second embodiment is characterized in that the planetary gear mechanism is composed of a carrier, a sun gear, and a ring gear. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0187] In the first embodiment, the planetary gear mechanism 29 of the planetary continuously variable transmission mechanism 24 is configured with a carrier and two sun gears. In contrast, in the second embodiment, the planetary gear mechanism 81 of the planetary continuously variable transmission mechanism 24 is configured with a carrier 81A, a sun gear 81B, and a ring gear 81C. Table 6 below shows combinations of components (carrier, sun gear, ring gear) of the planetary gear mechanism 81. In either case, power transmission is possible. "No. 2-A" in Table 6 is most suitable in terms of improving the transmission efficiency of the planetary continuously variable transmission mechanism 24, reducing the maximum absorption torque of the first variator 33, and making the entire planetary continuously variable transmission mechanism 24 small and lightweight.

[0188] [Table 6]

[0189] 27 and 28, in the second embodiment (i.e., No. 2-A in Table 6), the planetary gear mechanism 81 includes a carrier 81A corresponding to the first member, a sun gear 81B corresponding to the second member, a ring gear 81C corresponding to the third member, and a planet gear 81D. Note that the sun gear 81B, the ring gear 81C, and the planet gears 81D do not have to transmit power by meshing of gears (gears), and may transmit power by friction of rollers (outer circumferential surfaces), for example.

[0190] The engine 9 is coupled to the carrier 81A via the second connecting member 31. The sun gear 81B is connected to the first variator 33 via the first connecting member 30. The ring gear 81C is connected to the idler element 28 (idler gear 28B) via the third connecting member 32. The sun gear 81B meshes with the planet gear 81D. The planet gear 81D also meshes with the ring gear 81C. The rotation axis Sp (FIG. 29) of the planet gear 81D is supported by the carrier 81A. Therefore, the planet gear 81D rotates while revolving around the central axis S (FIG. 29) of the planetary gear mechanism 81.

[0191] Next, the operation of the planetary gear mechanism 81, which is composed of the carrier 81A, the sun gear 81B, and the ring gear 81C, will be described. The following applies under all conditions of "No2-A", "No2-B", "No2-C", "No2-D", "No2-E", and "No2-F" in Table 6.

[0192] First, the distribution of torque among the three members (carrier 81A, sun gear 81B, ring gear 81C) of the planetary gear mechanism 81 will be described. FIG. 29 is a cross-sectional view of the planetary gear mechanism 81 seen from the power source side. The carrier 81A, sun gear 81B, and ring gear 81C are arranged concentrically. That is, the central axes S (rotational central axes) of the carrier 81A, sun gear 81B, and ring gear 81C coincide with each other. The planet gear 81D is arranged so as to be in contact with the outer periphery of the sun gear 81B and the inner periphery of the ring gear 81C. The planet gear 81D meshes with the sun gear 81B and the ring gear 81C. The carrier 81A, sun gear 81B, and ring gear 81C are supported by the casing of the planetary type continuously variable transmission mechanism 24 so as to be rotatable about the central axis S and so as not to move in the other direction, so that the meshing of the respective gears is established. The planet gear 81D is supported by the carrier 81A so as to be rotatable about a rotation axis Sp, which is the central axis of the planet gear 81D, and so as not to move in the other direction. The planet gear 81D rotates about the central axis Sp of the planet gear 81D while revolving around the central axis S of the carrier 81A.

[0193] The constraint of the planetary gear mechanism 81 is that the sun gear 81B, the ring gear 81C, and the planet gear 81D must mesh with each other, as shown in Fig. 29. Also, in order to ensure the strength of the gears, the diameter of the planet gear 81D must be large. In other words, the constraint of the planetary gear mechanism 81 is that the meshing radius rs of the sun gear 81B must be significantly smaller than the meshing radius rr of the ring gear 81C.

[0194] In the configuration of "No2-A" in Table 6, the carrier 81A is connected to the second connecting member 31 connected to the engine 9 (power source). Therefore, the torque Tc of the carrier 81A is the torque that the engine 9 can generate. The sun gear 81B is connected to the first connecting member 30 connected to the first variator 33. Therefore, the torque Ts of the sun gear 81B is the torque that the first variator 33 can generate. The ring gear 81C is connected to the third connecting member 32 connected to the idler element 28. Therefore, the torque Tr of the ring gear 81C is the torque reaction force received from the idler gear 28B.

[0195] In the configuration of "No2-B" in Table 6, the ring gear 81C is connected to the second connecting member 31. Therefore, the torque Tr of the ring gear 81C is the torque that the engine 9 can generate. The carrier 81A is connected to the first connecting member 30. Therefore, the torque Tc of the carrier 81A is the torque that the first variator 33 can generate. The sun gear 81B is connected to the third connecting member 32. Therefore, the torque Ts of the sun gear 81B is the torque reaction force received from the idler gear 28B.

[0196] In the configuration of "No2-C" in Table 6, the carrier 81A is connected to the second connecting member 31, the ring gear 81C is connected to the first connecting member 30, and the sun gear 81B is connected to the third connecting member 32. In the configuration of "No2-D" in Table 6, the ring gear 81C is connected to the second connecting member 31, the sun gear 81B is connected to the first connecting member 30, and the carrier 81A is connected to the third connecting member 32. In the configuration of "No2-E" in Table 6, the sun gear 81B is connected to the second connecting member 31, the ring gear 81C is connected to the first connecting member 30, and the carrier 81A is connected to the third connecting member 32. In the configuration of "No2-F" in Table 6, the sun gear 81B is connected to the second connecting member 31, the carrier 81A is connected to the first connecting member 30, and the ring gear 81C is connected to the third connecting member 32.

[0197] Next, the relationship between torque Ts of sun gear 81B, torque Tr of ring gear 81C, and torque Tc of carrier 81A will be described. Sun gear 81B and ring gear 81C mesh with each other via planet gear 81D. Therefore, the meshing tangential force between sun gear 81B and planet gear 81D is equal to the meshing tangential force between planet gear 81D and ring gear 81C. That is, the following formulas 22 and 23 are obtained.

[0198]

number

[0199]

number

[0200] The action-reaction relationship gives us the following equation (24).

[0201]

number

[0202] From these formulas 22, 23, and 24, the torque Ts of the sun gear 81B, the torque Tr of the ring gear 81C, and the torque Tc of the carrier 81A can be calculated from the meshing radius rr of the ring gear 81C and the meshing radius rs of the sun gear 81B. The meshing radius rr of the ring gear 81C and the meshing radius rs of the sun gear 81B are determined by the meshing radius of each gear, and therefore cannot be changed while the planetary continuously variable transmission mechanism 24 is transmitting power. For this reason, the ratio of the torque Ts of the sun gear 81B, the torque Tr of the ring gear 81C, and the torque Tc of the carrier 81A remains unchanged while the planetary continuously variable transmission mechanism 24 is transmitting power.

[0203] Based on this law, the controller 25 outputs a signal to control the first variator 33, and controls the torque of the first connecting member 30 (for example, the sun gear 81B) connected to the first variator 33. That is, the controller 25 controls the torque of the first connecting member 30 (for example, the sun gear 81B) by controlling the first variator 33. As a result, the controller 25 indirectly controls the torque of the second connecting member 31 (for example, the carrier 81A) connected to the engine 9 and the torque of the third connecting member 32 (for example, the ring gear 81C) connected to the idler element 28. As a result, it is possible to control the transmission torque between the second connecting member 31 (for example, the carrier 81A) connected to the engine 9 and the third connecting member 32 (for example, the ring gear 81C) connected to the idler element 28.

[0204] Next, the relationship between the rotation speed of the sun gear 81B, the rotation speed of the ring gear 81C, and the rotation speed of the carrier 81A will be described. First, the sun gear 81B and the ring gear 81C are meshed with each other via the planet gear 81D. The sun gear 81B and the ring gear 81C rotate about the central axis S. The planet gear 81D rotates freely in the rotation direction by the carrier 81A, and is constrained in the revolution direction with respect to the central axis S of the carrier 29A. From these, the relationship between the rotation speeds is obtained as shown in the following formula 25. Note that "Kb" in formula 25 is as shown in formula 26. Note that the rotation speed of the carrier 81A is "Vc", the rotation speed of the sun gear 81B is "Vs", and the rotation speed of the ring gear 81C is "Vr".

[0205]

number

[0206]

number

[0207] FIG. 30 shows the relationship of the rotation speed of the planetary gear mechanism 81. The speed relationship line Y2 in FIG. 30 is a diagram of the formula (25). It is assumed that the rotation speed of the carrier 81A is constant. In this case, if the rotation speed of the ring gear 81C is increased, the rotation speed of the sun gear 81B is decreased. Conversely, if the rotation speed of the ring gear 81C is decreased, the rotation speed of the sun gear 81B is increased. Based on this law, the controller 25 outputs a signal to control the first variator 33 and controls the rotation speed of the first connecting member 30 (for example, the sun gear 81B) connected to the first variator 33. That is, the controller 25 controls the rotation speed of the first connecting member 30 (for example, the sun gear 81B) by controlling the first variator 33. Thereby, the controller 25 indirectly controls the rotation speed of the second connecting member 31 (e.g., carrier 81A) connected to the engine 9 and the rotation speed of the third connecting member 32 (e.g., ring gear 81C) connected to the idler element 28. As a result, it is possible to control the gear ratio between the second connecting member 31 (e.g., carrier 81A) connected to the engine 9 and the third connecting member 32 (e.g., ring gear 81C) connected to the idler element 28.

[0208] As described above, the planetary gear mechanism 81 requires that the sun gear 81B, the ring gear 81C, and the planet gear 81D mesh with each other. In addition, the diameter of the planet gear 81D needs to be increased in order to ensure the strength of the gears. However, increasing the diameter of the planet gear 81D increases the size of the planetary gear mechanism 81. That is, the structural constraint of the planetary gear mechanism 81 is that, when designing the planetary gear mechanism 81 to be compact, the meshing radius rs of the sun gear 81B becomes significantly smaller than the meshing radius rr of the ring gear 81C. For this reason, it is difficult for the planetary gear mechanism 81 to have a value of Kb greater than 0.3, and there is a possibility that the value of Kb will be too small compared to the ideal value.

[0209] Due to this structural constraint, the planetary gear mechanism 81 adjusts the meshing radius rs of the sun gear 81B and the meshing radius rr of the ring gear 81C according to the torque that the first variator 33 can absorb and the maximum allowable rotation speed from the relational expressions (Equation 22, Equation 23, Equation 24) of the torques Tc, Ts, and Tr and the relational expressions (Equation 25, Equation 26) of the rotational speeds Vs, Vr, and Vc. This allows both the torque that the first variator 33 can absorb and the maximum allowable rotation speed to be reduced by setting the value of Kb in Equation 26 to an ideal value and setting the gradient of the speed relational line Y2 shown in FIG. 30 to an ideal value. However, this makes the value of Kb too small, making it difficult to achieve both. That is, the second embodiment may be disadvantageous in providing an arrangement of the planetary gear mechanism 81 in which both the torque that the first variator 33 can absorb and the maximum allowable rotation speed are optimized, compared to the first embodiment. That is, in the second embodiment, the first variator 33 tends to be more expensive than in the first embodiment, and the transmission efficiency of the planetary continuously variable transmission mechanism 24 may decrease.

[0210] The size and price of the first variator 33 are proportional to the amount of torque that can be absorbed. For this reason, it is desirable for the torque absorbed by the first variator 33 to be small. A specific example will be described in the second embodiment (i.e., No. 2-A in Table 6). First, it is desirable to make the value of Kb in equation (26) small. In addition, the smaller the torque distributed to the first variator 33, the more the transmission efficiency of the planetary continuously variable transmission mechanism 24 can be improved. For this reason, it is advantageous for the planetary continuously variable transmission mechanism 24 to make the value of Kb in equation (26) small.

[0211] On the other hand, from the speed relationship line Y2 shown in FIG. 30, if the value of Kb is reduced, the rotation speed of the first variator 33 increases. For this reason, it is desirable to reduce the value of Kb within a range that does not exceed the maximum allowable rotation speed of the first variator 33. The planetary gear mechanism 81, which is composed of a sun gear, a ring gear, and a carrier, has a structural constraint that, when attempting to design the planetary gear mechanism 81 in a compact size, the meshing radius rs of the sun gear 81B is significantly smaller than the meshing radius rr of the ring gear 81C. For this reason, when attempting to design the planetary gear mechanism 81 in a compact size, the value of Kb becomes too small. As a result, the rotation speed of the first variator 33 increases, and there is a possibility that it will exceed the maximum allowable rotation speed of the first variator 33. For this reason, a planetary gear mechanism 81 that can operate at high revolutions is required. That is, the first variator 33 must be expensive in order to handle high speed rotation, the planetary gear mechanism 81 must be large, and the transmission efficiency of the planetary continuously variable transmission mechanism 24 may decrease.

[0212] In the second embodiment (No. 2-A in Table 6), the terminal 30 connected to the first variator 33 is connected to the sun gear 81B. From the above formulas 22, 23, and 24, by increasing the absorption torque of the first variator 33, the torque of the carrier 81A and the ring gear 81C can be increased, and the torque of the terminal 32 connected to the idler gear 28B connected to the ring gear 81C can be increased. Since the terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, the torque of the output shaft 23 can be increased.

[0213] Moreover, according to the above-mentioned formula 26, since Kb>0, the intercept of the formula 25 is positive. This relationship is shown in FIG. 30. When the rotation speed of the carrier 81A is constant, when the rotation speed of the ring gear 81C is low (i.e., when the vehicle speed is low), the rotation speed (rotation speed) of the sun gear 81B becomes high. For example, when the vehicle speed of the vehicle is 0 (when the rotation speed of the ring gear 81C is 0), the sun gear 81B rotates, so that the first variator 33 rotates, whereas the rotation speed of the second variator 34 is 0. When the vehicle speed of the vehicle is 0, if the absorption torque of the first variator 33 is increased, the first variator 33 sends to the transfer element 35 more power than the second variator 34 can receive. Therefore, when the vehicle speed is lower than a predetermined value, the power absorbing device 38 installed on the transfer element 35 absorbs (disposes of or stores) the surplus power. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0214] In the seventh modified example (No. 2-B in Table 6) shown in FIG. 36, the terminal 30 connected to the first variator 33 is connected to the carrier 81A. From the above-mentioned formulas 22, 23, and 24, by increasing the absorption torque of the first variator 33, the torque of the sun gear 81B and the ring gear 81C can be increased, and the torque of the terminal 32 connected to the idler gear 28B connected to the sun gear 81B can be increased. Since the terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, the torque of the output shaft 23 can be increased. On the other hand, by transforming the above-mentioned formula 25, the following formula 27 is obtained.

[0215]

number

[0216] Moreover, according to Equation 26, since Kb>0, the intercept of Equation 27 is positive. This relationship is shown in FIG. 31. When the rotation speed of the ring gear 81C is constant, the rotation speed of the sun gear 81B is proportional to the rotation speed of the carrier 81A. For example, when the vehicle speed is 0 (when the rotation speed of the sun gear 81B is 0), the carrier 81A is rotating, so the first variator 33 is rotating, whereas the rotation speed of the second variator 34 is 0. When the vehicle speed is 0, if the absorption torque of the first variator 33 is increased, the first variator 33 sends to the transfer element 35 more power than the second variator 34 can receive. Therefore, when the vehicle speed is equal to or lower than a predetermined value, the power absorbing device 38 installed on the transfer element 35 absorbs (disposes of or stores) the surplus power. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0217] In the eighth modified example (No. 2-C in Table 6) shown in FIG. 37, the terminal 30 connected to the first variator 33 is connected to the ring gear 81C. From the above formulas 22, 23, and 24, by increasing the absorption torque of the first variator 33, the torque of the sun gear 81B and the carrier 81A can be increased, and the torque of the terminal 32 connected to the idler gear 28B connected to the sun gear 81B can be increased. Since the terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, the torque of the output shaft 23 can be increased. On the other hand, by modifying the above formula 25, the following formula 28 is obtained.

[0218]

number

[0219] Moreover, according to Equation 26, since Kb>0, the slope of Equation 28 is negative. This relationship is shown in FIG. 32. When the rotation speed of the carrier 81A is constant, the rotation speed of the sun gear 81B and the rotation speed of the ring gear 81C are proportional. For example, when the vehicle speed is 0 (when the rotation speed of the sun gear 81B is 0), the ring gear 81C is rotating, so the first variator 33 is rotating, whereas the rotation speed of the second variator 34 is 0. When the vehicle speed is 0, if the absorption torque of the first variator 33 is increased, the first variator 33 sends to the transmission element 35 more power than the second variator 34 can receive. Therefore, when the vehicle speed is equal to or lower than a predetermined value, the power absorbing device 38 installed on the transmission element 35 absorbs (disposes of or stores) the surplus power. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0220] In a ninth modified example (No. 2-D in Table 6) shown in FIG. 38, the terminal 30 connected to the first variator 33 is connected to the sun gear 81B. From the above formulas 22, 23, and 24, by increasing the absorption torque of the first variator 33, the torque of the ring gear 81C and the carrier 81A can be increased, and the torque of the terminal 32 connected to the idler gear 28B connected to the carrier 81A can be increased. Since the terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, the torque of the output shaft 23 can be increased. On the other hand, by modifying the above formula 25, the following formula 29 is obtained.

[0221]

number

[0222] Moreover, according to Equation 26, since Kb>0, the slope of Equation 29 is positive. This relationship is shown in FIG. 33. When the rotation speed of the ring gear 81C is constant, the rotation speed of the sun gear 81B and the rotation speed of the carrier 81A are proportional. For example, when the vehicle speed is 0 (when the rotation speed of the carrier 81A is 0), the sun gear 81B is rotating, so the first variator 33 is rotating, whereas the rotation speed of the second variator 34 is 0. Therefore, when the vehicle speed is 0, if the absorption torque of the first variator 33 is increased, the first variator 33 sends to the transfer element 35 more power than the second variator 34 can receive. Therefore, when the vehicle speed is equal to or lower than a predetermined value, the power absorbing device 38 installed on the transfer element 35 absorbs (disposes of or stores) the surplus power. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0223] In a tenth modified example (No. 2-E in Table 6) shown in FIG. 39, the terminal 30 connected to the first variator 33 is connected to the ring gear 81C. From the above formulas 22, 23, and 24, by increasing the absorption torque of the first variator 33, the torque of the sun gear 81B and the carrier 81A can be increased, and the torque of the terminal 32 connected to the idler gear 28B connected to the carrier 81A can be increased. Since the terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, the torque of the output shaft 23 can be increased. On the other hand, by modifying the above formula 25, the following formula 30 is obtained.

[0224]

number

[0225] Moreover, according to Equation 26, since Kb>0, the slope of Equation 30 is positive. This relationship is shown in FIG. 34. When the rotation speed of the sun gear 81B is constant, the rotation speed of the ring gear 81C and the rotation speed of the carrier 81A are proportional to each other. For example, when the vehicle speed is 0 (when the rotation speed of the carrier 81A is 0), the ring gear 81C rotates, so the first variator 33 rotates, whereas the rotation speed of the second variator 34 is 0. Therefore, when the vehicle speed is 0, if the absorption torque of the first variator 33 is increased, the first variator 33 sends to the transfer element 35 more power than the second variator 34 can receive. Therefore, when the vehicle speed is equal to or lower than a predetermined value, the power absorbing device 38 installed on the transfer element 35 absorbs (disposes of or stores) the surplus power. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0226] In an eleventh modified example (No. 2-F in Table 6) shown in FIG. 40, the terminal 30 connected to the first variator 33 is connected to the carrier 81A. From the above-mentioned formulas 22, 23, and 24, by increasing the absorption torque of the first variator 33, the torque of the ring gear 81C and the sun gear 81B can be increased, and the torque of the terminal 32 connected to the idler gear 28B connected to the ring gear 81C can be increased. Since the terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, the torque of the output shaft 23 can be increased. On the other hand, by transforming the above-mentioned formula 25, the following formula 31 can be obtained.

[0227]

number

[0228] Moreover, according to Equation 26, since Kb>0, the slope of Equation 31 is positive. This relationship is shown in FIG. 35. When the rotation speed of the sun gear 81B is constant, the rotation speed of the ring gear 81C and the rotation speed of the carrier 81A are proportional. For example, when the vehicle speed is 0 (when the rotation speed of the ring gear 81C is 0), the carrier 81A is rotating, so the first variator 33 is rotating, whereas the rotation speed of the second variator 34 is 0. Therefore, when the vehicle speed is 0, if the absorption torque of the first variator 33 is increased, the first variator 33 sends to the transfer element 35 more power than the second variator 34 can receive. Therefore, when the vehicle speed is equal to or lower than a predetermined value, the power absorbing device 38 installed on the transfer element 35 absorbs (disposes of or stores) the surplus power. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0229] In the second embodiment of FIG. 27 (No. 2-A in Table 6), when the torque of the first variator 33 is increased, the torque of the terminal 30 connected to the first variator 33 increases, and the torque of the sun gear 81B increases. In proportion to the torque of the sun gear 81B, the torque of the ring gear 81C (terminal 32 connected to the idler gear 28B) and the torque of the carrier 81A (terminal 31 connected to the power source) increase. For example, when the gear ratio is 0.5 (corresponding to a vehicle speed of 2 to 5 km / h), the power absorbing device 38 is configured in consideration of the power that the second variator 34 can receive when the first variator 33 is in a gear ratio of 0.5 (corresponding to a vehicle speed of 2 to 5 km / h).

[0230] When the torque of the first variator 33 is increased to a predetermined value or more at a speed ratio of less than 0.5, the output torque of the second variator 34 is at a maximum value, so that the second variator 34 cannot receive all of the power sent by the first variator 33. Therefore, the torque of the ring gear 81C (terminal 32 connected to the idler gear 28B) can be increased by increasing the torque of the first variator 33 by the power absorbing device 38 between the first variator 33 and the second variator 34. As a result, according to the above formula 13, the torque of the idler gear 28B can be increased at a speed ratio of less than 0.5 (corresponding to a vehicle speed of 2 to 5 km / h). The terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, so that the torque of the output shaft 23 can be increased. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0231] In the seventh modified example in FIG. 36 (No. 2-B in Table 6), when the torque of the first variator 33 is increased, the torque of the terminal 30 connected to the first variator 33 increases, and the torque of the carrier 81A increases. In proportion to the torque of the carrier 81A, the torque of the sun gear 81B (terminal 32 connected to the idler gear 28B) and the torque of the ring gear 81C (terminal 31 connected to the power source) increase. For example, at a gear ratio of 0.5 (corresponding to a vehicle speed of 2 to 5 km / h), the torque of either the first variator 33 or the second variator 34 constitutes the power absorbing device 38 based on the maximum value that can be absorbed or output.

[0232] When the speed ratio is less than 0.5, the torque of the first variator 33 or the second variator 34 is at a maximum value, and therefore the torque of the first variator 33 cannot be increased any more. For this reason, the torque of the sun gear 81B (terminal 32 connected to the idler gear 28B) can be increased by increasing the torque of the first variator 33 by the power absorbing device 38 between the first variator 33 and the second variator 34. As a result, according to the above formula (13), the torque of the idler gear 28B can be increased when the speed ratio is less than 0.5 (corresponding to a vehicle speed of 2 to 5 km / h). Since the terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-stage transmission mechanism 26, the torque of the output shaft 23 can be increased. As a result, the transmission 21 can increase the output torque when the vehicle speed is 0 to 5 km / h, and the traction force of the wheel loader 1 increases.

[0233] In the eighth modified example of Fig. 37 (No. 2-C in Table 6), when the torque of the first variator 33 is increased, the torque of the terminal 30 connected to the first variator 33 increases, and the torque of the ring gear 81C increases. In proportion to the torque of the ring gear 81C, the torque of the sun gear 81B (terminal 32 connected to the idler gear 28B) and the torque of the carrier 81A (terminal 31 connected to the power source) increase. For example, when the gear ratio is 0.5 (corresponding to a vehicle speed of 2 to 5 km / h), the power absorbing device 38 is configured taking into consideration the power that the second variator 34 can receive when the first variator 33 is relative to the second variator 34.

[0234] When the torque of the first variator 33 is increased to a predetermined value or more at a speed ratio of less than 0.5, the output torque of the second variator 34 is at a maximum value, so that the second variator 34 cannot receive all of the power sent by the first variator 33. Therefore, the torque of the sun gear 81B (terminal 32 connected to the idler gear 28B) can be increased by increasing the torque of the first variator 33 by the power absorbing device 38 between the first variator 33 and the second variator 34. As a result, according to the above formula 13, the torque of the idler gear 28B at a speed ratio of less than 0.5 (corresponding to a vehicle speed of 2 to 5 km / h) can be increased. Since the terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-stage transmission mechanism 26, the torque of the output shaft 23 can be increased. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0235] In the ninth modified example of Fig. 38 (No. 2-D in Table 6), when the torque of the first variator 33 is increased, the torque of the terminal 30 connected to the first variator 33 increases, and the torque of the sun gear 81B increases. In proportion to the torque of the sun gear 81B, the torque of the carrier 81A (terminal 32 connected to the idler gear 28B) and the torque of the ring gear 81C (terminal 31 connected to the power source) increase. For example, when the gear ratio is 0.5 (corresponding to a vehicle speed of 2 to 5 km / h), the power absorbing device 38 is configured in consideration of the power that the second variator 34 can receive when the first variator 33 is relative to the second variator 34.

[0236] When the torque of the first variator 33 is increased to a predetermined value or more at a speed ratio of less than 0.5, the output torque of the second variator 34 is at a maximum value, so that the second variator 34 cannot receive all of the power sent by the first variator 33. Therefore, the torque of the carrier 81A (terminal 32 connected to the idler gear 28B) can be increased by increasing the torque of the first variator 33 by the power absorbing device 38 between the first variator 33 and the second variator 34. As a result, according to the above formula 13, the torque of the idler gear 28B at a speed ratio of less than 0.5 (corresponding to a vehicle speed of 2 to 5 km / h) can be increased. Since the terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, the torque of the output shaft 23 can be increased. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0237] In the tenth modified example of Fig. 39 (No. 2-E in Table 6), when the torque of the first variator 33 is increased, the torque of the terminal 30 connected to the first variator 33 increases, and the torque of the ring gear 81C increases. In proportion to the torque of the ring gear 81C, the torque of the carrier 81A (terminal 32 connected to the idler gear 28B) and the torque of the sun gear 81B (terminal 31 connected to the power source) increase. For example, when the gear ratio is 0.5 (corresponding to a vehicle speed of 2 to 5 km / h), the power absorbing device 38 is configured taking into consideration the power that the second variator 34 can receive when the first variator 33 is relative to the second variator 34.

[0238] When the torque of the first variator 33 is increased to a predetermined value or more at a speed ratio of less than 0.5, the output torque of the second variator 34 is at a maximum value, so that the second variator 34 cannot receive all of the power sent by the first variator 33. Therefore, the torque of the carrier 81A (terminal 32 connected to the idler gear 28B) can be increased by increasing the torque of the first variator 33 by the power absorbing device 38 between the first variator 33 and the second variator 34. As a result, according to the above formula 13, the torque of the idler gear 28B at a speed ratio of less than 0.5 (corresponding to a vehicle speed of 2 to 5 km / h) can be increased. Since the terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, the torque of the output shaft 23 can be increased. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0239] In the eleventh modified example in Fig. 40 (No. 2-F in Table 6), when the torque of the first variator 33 is increased, the torque of the terminal 30 connected to the first variator 33 increases, and the torque of the carrier 81A increases. In proportion to the torque of the carrier 81A, the torque of the ring gear 81C (terminal 32 connected to the idler gear 28B) and the torque of the sun gear 81B (terminal 31 connected to the power source) increase. For example, when the gear ratio is 0.5 (corresponding to a vehicle speed of 2 to 5 km / h), the power absorbing device 38 is configured taking into consideration the power that the second variator 34 can receive when the first variator 33 is in relation to the second variator 34.

[0240] When the torque of the first variator 33 is increased to a predetermined value or more at a speed ratio of less than 0.5, the output torque of the second variator 34 is at a maximum value, so that the second variator 34 cannot receive all of the power sent by the first variator 33. Therefore, the torque of the ring gear 81C (terminal 32 connected to the idler gear 28B) can be increased by increasing the torque of the first variator 33 by the power absorbing device 38 between the first variator 33 and the second variator 34. As a result, according to the above formula 13, the torque of the idler gear 28B can be increased at a speed ratio of less than 0.5 (corresponding to a vehicle speed of 2 to 5 km / h). The terminal 32 connected to the idler gear 28B is connected to the output shaft 23 via the idler gear 28B and the multi-speed mechanism 26, so that the torque of the output shaft 23 can be increased. This enables the transmission 21 to increase the output torque when the vehicle speed is between 0 and 5 km / h, and the tractive force of the wheel loader 1 increases.

[0241] Next, the planetary gear mechanism 29 of the first embodiment and the planetary gear mechanism 81 of the second embodiment are compared. That is, these two planetary gear mechanisms 29, 81 each have their own characteristics, and it cannot be said that one is superior to the other. That is, when the torque that the first variator 33 can absorb and the maximum rotation speed that the first variator 33 can tolerate can be freely set, it is preferable to adopt the planetary gear mechanism 81, which is structurally simple. As a result, by designing the first variator 33 in accordance with the structural constraints (value of Kb) of the meshing radius rs of the sun gear 81B of the planetary gear mechanism 81 and the meshing radius rr of the ring gear 81C, a small and inexpensive first variator 33 can be used. As a result, the planetary gear mechanism 81 can be simplified, and the transmission efficiency of the planetary type continuously variable transmission mechanism 24 can be improved.

[0242] On the other hand, when the torque that the first variator 33 can absorb and the maximum allowable rotation speed cannot be freely set, it is preferable to employ the planetary gear mechanism 29 of the first embodiment. In this case, it is preferable to set the value of Ka to an ideal value and to make the gradient of the speed relationship line Y1 shown in Fig. 7 an ideal value, so that the torque that the first variator 33 can absorb and the maximum allowable rotation speed can all be used. This makes it possible to use a small and inexpensive first variator 33 and to improve the transmission efficiency of the planetary continuously variable transmission mechanism 24.

[0243] Next, the internal lockup speed ratio In of the planetary continuously variable transmission mechanism 24 according to the second embodiment will be described. During internal lockup operation, the internal lockup speed ratio In can be calculated by substituting the rotation speed of the first connecting member 30 connected to the first variator 33 as 0 into the above-mentioned equation (25). For example, in the second embodiment (No. 2-A in Table 6), the rotation speed Vs of the sun gear 81B connected to the first connecting member 30 is substituted as 0 into the equation (25). That is, the internal lockup speed ratio In is given by the following equation (32).

[0244]

number

[0245] In the seventh modified example (No. 2-B in Table 6) shown in Fig. 36, Equation 25 is modified and the rotation speed Vc of the carrier 81A connected to the first connecting member 30 is substituted as 0. That is, the internal lockup speed ratio In is expressed by the following Equation 33.

[0246]

number

[0247] In the eighth modified example (No. 2-C in Table 6) shown in FIG. 37, the rotation speed Vr of ring gear 81C connected to first connecting member 30 is substituted as 0 into equation (25). That is, the internal lockup speed ratio In is expressed by the following equation (34).

[0248]

number

[0249] In a ninth modified example (No. 2-D in Table 6) shown in FIG. 38, the rotation speed Vs of sun gear 81B connected to first connecting member 30 is substituted as 0 into equation (25). That is, the internal lockup speed ratio In is expressed by the following equation (35).

[0250]

number

[0251] In a tenth modified example (No. 2-E in Table 6) shown in FIG. 39, the rotation speed Vr of ring gear 81C connected to first connecting member 30 is substituted as 0 into equation (25). That is, the internal lockup speed ratio In is expressed by the following equation (36).

[0252]

number

[0253] In an eleventh modified example (No. 2-F in Table 6) shown in FIG. 40, equation (25) is modified and the rotation speed Vc of the carrier 81A connected to the first connecting member 30 is substituted as 0. That is, the internal lockup speed ratio In is expressed by the following equation (37).

[0254]

number

[0255] In this way, the internal lockup speed ratio In of the planetary continuously variable transmission mechanism 24 according to the second embodiment depends on the gear combination of the planetary gear mechanism 81 and Kb.

[0256] As described above, according to the second embodiment, the transmission 21 includes the input shaft 22 (input member), the output shaft 23 (output member), the planetary gear mechanism 81 (planetary mechanism), the first variator 33, the second variator 34, and the controller 25. The planetary gear mechanism 81 includes three members (rotating members): the carrier 81A, the sun gear 81B (sun member) that rotates about the central axis of rotation of the carrier 81A, and the ring gear 81C (ring member) that is positioned radially outward of the sun gear 81B and rotates about the central axis of rotation of the carrier 81A.

[0257] In this case, for example, as shown in FIG. 27 and FIG. 28, the carrier 81A, which is the first member of the three members, is connected to the input shaft 22 via the second connecting member 31 (another member). The sun gear 81B, which is the second member different from the carrier 81A, is connected to the first variator 33 via the first connecting member 30 and the second clutch 36 (all other members). The ring gear 81C, which is the third member different from the carrier 81A and the sun gear 81B, is connected to the output shaft 23 via the third connecting member 32, the idler element 28, and the multi-stage transmission mechanism 26 (all other members). The carrier 81A (first member) may be directly connected to the input shaft 22. The sun gear 81B (second member) may be directly connected to the first variator 33. The ring gear 81C (third member) may be directly connected to the output shaft 23.

[0258] Here, the carrier 81A supports a planet gear 81D (planet member) that transmits power while revolving around the rotation center axis S of the carrier 81A and rotating with the sun gear 81B and the ring gear 81C. The planetary gear mechanism 81 distributes the torque transmitted from the engine 9 to the carrier 81A (first member) of the planetary gear mechanism 81 to the sun gear 81B (second member) and the ring gear 81C (third member). The planetary gear mechanism 81 performs a two-degree-of-freedom rotational motion between the carrier 81A, the sun gear 81B, and the ring gear 81C. The second variator 34 transmits the power transmitted from the first variator 33 to the load (output shaft 23) or the power source (input shaft 22), or transmits the power transmitted from the load (output shaft 23) or the power source (input shaft 22) to the first variator 33. The controller 25 changes the rotation speed of the output shaft 23 relative to the rotation speed of the input shaft 22 by changing the rotation speed of the first variator 33 .

[0259] That is, the transmission 21 of the second embodiment performs stepless speed change by the planetary gear mechanism 81, and transmits power from the power source (input shaft 22) to the load (output shaft 23), or transmits power from the load (output shaft 23) to the power source (input shaft 22). In this case, the transmission 21 includes the planetary gear mechanism 81 provided between the input shaft 22 and the output shaft 23, the first variator 33 connected to the planetary gear mechanism 81, and the second variator 34 that transmits the power transmitted from the first variator 33 to the load or the power source. The planetary gear mechanism 81 includes a carrier 29A connected to the input shaft 22 and supporting a planet gear 81D, a sun gear 81B connected to the first variator 33, and a ring gear 81C connected to the output shaft 23 via the idler element 28 and the multi-stage transmission mechanism 26. Furthermore, the transmission 21 is provided with at least one of an internal lockup and an external lockup (direct drive mechanism 27). The transmission 21 can switch between power transmission by the planetary continuously variable transmission mechanism 24 and power transmission by the lockup.

[0260] Furthermore, in the transmission 21 of the second embodiment, similarly to the first embodiment, a power absorbing device 38 that absorbs power between the second variator 34 and the first variator 33 is provided. The power absorbing device 38 changes the absorption torque of the first variator 33 by the controller 25, and when power is generated that is greater than can be absorbed by the second variator 34, it absorbs the power, thereby increasing the torque of the output shaft 23, which serves as an output member. Therefore, the second embodiment can also achieve the same effects as the first embodiment.

[0261] According to the second embodiment, similarly to the first embodiment, the second variator 34 is connected to an idler element 28 (specifically, an idler gear 28B serving as a rotating element) provided between the planetary gear mechanism 81 and the multi-speed mechanism 26. Note that, as shown in Fig. 41 to Fig. 50, the second variator 34 may be configured to be connected to a rotating element provided between the input shaft 22 (input member) and the drive source (engine 9), a rotating element constituting the multi-speed mechanism 26, a rotating element provided between the multi-speed mechanism 26 and the output shaft 23 (output member), the output shaft 23 (output member), or a rotating element provided between the output shaft 23 and a load.

[0262] That is, in the first and second embodiments, the second variator 34 is connected closer to the output shaft 23 (output member) than the planetary gear mechanism 29, that is, the second variator 34 is connected between the planetary gear mechanism 29 and the output shaft 23. In contrast to this, FIG. 41 shows a twelfth modified example. In the twelfth modified example, the second variator 34 is connected to the input gear 27A of the direct drive mechanism 27 provided on the input shaft 22. That is, the second variator 34 is connected between the planetary gear mechanism 29 and the input shaft 22 (input member). In this way, the second variator 34 may be connected closer to the engine 9 (drive source) than the planetary gear mechanism 29. Although not shown, the second variator 34 may be connected to the lockup gear 27B of the direct drive mechanism 27.

[0263] FIG. 42 shows a thirteenth modified example. In the thirteenth modified example, the second variator 34 is connected to the third connecting member 32 which is connected to the idler element 28. FIG. 43 shows a fourteenth modified example. In the fourteenth modified example, the second variator 34 is connected to the odd-numbered gear 55 of the multi-stage transmission mechanism 26. Although not shown, the second variator 34 may be connected to the even-numbered gear 62 of the multi-stage transmission mechanism 26. FIG. 44 shows a fifteenth modified example. In the fifteenth modified example, the second variator 34 is connected to the forward first gear 56 of the multi-stage transmission mechanism 26. FIG. 45 shows a sixteenth modified example, in which the second variator 34 is connected to the forward third gear 57 of the multi-stage transmission mechanism 26. FIG. 46 shows a seventeenth modified example, in which the second variator 34 is connected to the forward second gear 63 of the multi-stage transmission mechanism 26. Fig. 47 shows an 18th modified example, in which the second variator 34 is connected to a fourth forward gear 64 of the multi-speed transmission mechanism 26. Fig. 48 shows a 19th modified example, in which the second variator 34 is connected to a first reverse gear 65 of the multi-speed transmission mechanism 26. Although not shown in the figures, the second variator 34 may also be connected to the counter gear 54 of the multi-speed transmission mechanism 26.

[0264] FIG. 49 shows a twentieth modified example, in which the second variator 34 is connected to the output shaft 53 of the multi-speed change mechanism 26 (the output shaft 23 of the transmission 21). Although not shown, the second variator 34 may be connected to the first-speed output gear 71, the second-speed output gear 72, the third-speed output gear 73, the fourth-speed output gear 74, or the reverse first-speed output gear 75 of the multi-speed change mechanism 26. FIG. 50 shows a twentieth modified example, in which the second variator 34 is connected to the load side (the front axle 12 side, the rear axle 13 side) of the output shaft 23 of the transmission 21. Although not shown, the second variator 34 may be connected to the front axle 12, the rear axle 13, the front propeller shaft 14, or the rear propeller shaft 15. According to these modified examples, for example, the 15th to 21st modified examples shown in Figures 44 to 50, by connecting the second variator 34 closer to the output shaft 53 than the idler gear 28B, it is possible to reduce the size of the idler element 28 (idler gear 28B) and the multi-stage transmission mechanism 26. This allows the transmission 21 to be manufactured at low cost.

[0265] In the first embodiment, the transmission 21 including the multi-speed mechanism 26 has been described as an example. However, the present invention is not limited to this, and the transmission 21 may omit the multi-speed mechanism 26. In this case, for example, the planetary gear mechanism 29 of the planetary type continuously variable transmission mechanism 24 and the output shaft 23 (output member) can be connected by screwing the output gear of the output shaft 23 to the third connecting member 32. In this case, the second variator 34 may be connected to the output shaft 23 side (output member side) of the planetary gear mechanism 29, or may be connected to the input shaft 22 side (input member side) of the planetary gear mechanism 29. Furthermore, in the first embodiment, the transmission 21 including the direct drive mechanism 27 as the external lockup mechanism has been described as an example, but the direct drive mechanism 27 may be omitted. The same applies to the second embodiment and each modified example.

[0266] In the first embodiment, the transmission 21 has been described as being mounted on a wheel loader 1. However, the present invention is not limited to this, and the transmission 21 may be mounted on work vehicles (construction machines) other than wheel loaders, such as hydraulic excavators, hydraulic cranes, dump trucks, and forklifts. Furthermore, the transmission can be widely applied not only to work vehicles, but also to various vehicles such as automobiles and railroad cars, or various industrial and general machines, as a transmission incorporated therein. The same applies to the second embodiment and each of the modified examples.

[0267] Furthermore, the above-described embodiments and modifications are merely examples, and it goes without saying that partial replacement or combination of the configurations shown in different embodiments and modifications is possible. [Explanation of symbols]

[0268] 1. Wheel loader (work vehicle) 21, 21A, 21B, 21C, 21D, 21E Transmission 22 Input shaft (input member) 23, 23A, 23B Output shaft (output member) 24 Planetary type continuously variable transmission (first power transmission path) 25 Controller 26 Multi-speed mechanism (auxiliary transmission mechanism) 27 Direct-coupled mechanism (external lock-up mechanism, second power transmission path) 27C First clutch 28 Idler elements 29 Planetary gear mechanism (planetary mechanism) 29A Carrier (1st member, 2nd member, 3rd member) 29B 1st sun gear (1st sun member, 1st member, 2nd member, 3rd member) 29C Second sun gear (second sun member, first member, second member, third member) 33 First variator 34 Second variator 36 Second clutch 38 Power Absorber 58 4th clutch (1st output clutch) 66 5th clutch (2nd output clutch) 69 9th clutch (2nd output clutch) 81 Planetary gear mechanism (planetary mechanism) 81A Carrier (1st member, 2nd member, 3rd member) 81B Sun gear (sun member, first member, second member, third member) 81C Ring gear (ring member, first member, second member, third member)

Claims

1. a first variator including an input member connected to a power source, an output member connected to a load, a planetary mechanism provided between the input member and the output member, a hydraulic pump connected to the planetary mechanism, a second variator including a hydraulic motor provided separately from the first variator, a pair of main lines connecting the first variator and the second variator to each other, and a controller that changes the rotation speed of the first variator, The planetary mechanism includes a carrier, a first sun member that rotates about a rotational center axis of the carrier, and a second sun member that rotates about a rotational center axis of the carrier, a first member of the members constituting the planetary mechanism is connected to the input member directly or via another member; a second member, which is separate from the first member, among the members constituting the planetary mechanism is connected to the first variator directly or via another member; a third member, which is different from the first member and the second member, among the members constituting the planetary mechanism is connected to the output member directly or via another member; A planet member and a balance member are supported on the carrier of the planetary mechanism, and the planet member and the balance member transmit power while revolving around a central axis of rotation of the carrier and rotating with the first sun member and the second sun member, the planetary mechanism is configured to be able to distribute torque transmitted from the power source to the planetary mechanism between the second member and the third member, the second variator is configured to transmit the power transmitted from the first variator to the load or the power source, or to transmit the power transmitted from the load or the power source to the first variator; a power absorbing device including two accumulators for absorbing power is provided between the second variator and the first variator; The two accumulators include a first accumulator that absorbs power and a second accumulator that supplies hydraulic oil to the first accumulator, the first accumulator and the second accumulator are connected to the pair of main lines via a switching valve that communicates with or blocks communication with the pair of main lines; the controller changes a rotational speed of the output member relative to a rotational speed of the input member by changing a rotational speed of the first variator; A transmission characterized in that, when power is generated that is greater than the power that can be absorbed by the second variator by changing the absorption torque of the first variator, the power is absorbed by accumulating pressure in the first accumulator, which is the power absorption device, thereby increasing the torque of the output member.

2. a first variator including an input member connected to a power source, an output member connected to a load, a planetary mechanism provided between the input member and the output member, a hydraulic pump connected to the planetary mechanism, a second variator including a hydraulic motor provided separately from the first variator, a pair of main lines connecting the first variator and the second variator to each other, and a controller that changes the rotation speed of the first variator, The planetary mechanism includes three members: a carrier, a sun member that rotates about a central axis of rotation of the carrier, and a ring member that is located radially outward of the sun member and rotates about the central axis of rotation of the carrier, a first member of the three members of the planetary mechanism is connected to the input member directly or via another member; a second member of the three members of the planetary mechanism, which is separate from the first member, is connected to the first variator directly or via another member; a third member, which is different from the first member and the second member, of the three members of the planetary mechanism is connected to the output member directly or via another member; A planet member is supported on the carrier of the planetary mechanism and rotates around a central axis of rotation of the carrier while transmitting power between the sun member and the ring member. the planetary mechanism is configured to be able to distribute torque transmitted from the power source to the second member and the third member, the second variator is configured to transmit the power transmitted from the first variator to the load or the power source, or to transmit the power transmitted from the load or the power source to the first variator; a power absorbing device including two accumulators for absorbing power is provided between the second variator and the first variator; The two accumulators include a first accumulator that absorbs power and a second accumulator that supplies hydraulic oil to the first accumulator, the first accumulator and the second accumulator are connected to the pair of main lines via a switching valve that communicates with or blocks communication with the pair of main lines; the controller changes a rotational speed of the output member relative to a rotational speed of the input member by changing a rotational speed of the first variator; A transmission characterized in that, when power is generated that is greater than the power that can be absorbed by the second variator by changing the absorption torque of the first variator, the power is absorbed by accumulating pressure in the first accumulator, which is the power absorption device, thereby increasing the torque of the output member.

Images