Work vehicle

Abstract

The present invention comprises a hydrostatic continuously variable transmission device (20) for steplessly changing the speed of the driving force of an engine (4), a plurality of planetary gear transmission devices (Q1, Q2) arranged in parallel for changing the speed of the driving force changed by the continuously variable transmission device (20), a plurality of clutch mechanisms (C1, C2) for respectively extracting the driving force from the plurality of planetary gear transmission devices (Q1, Q2), a travel speed change device (50) for changing the speed of the driving force transmitted from the plurality of clutch mechanisms (C1, C2) and transmitting the same to a travel mechanism, and the plurality of planetary gear transmission devices (Q1, Q2), the plurality of clutch mechanisms (C1, C2) and the travel speed change device (50) are accommodated in a transmission case (12).

Description

Technical Field

[0001] The present invention relates to a working vehicle that changes the speed of an engine's driving force by means of a hydrostatic continuously variable transmission and a planetary gear transmission.

[0002] Furthermore, the present invention relates to a work vehicle capable of changing the travel speed by intermittent operation of a multi-plate clutch. Background Art [Background Technology 1]

[0004] As a work vehicle having the above-described structure, Patent Document 1 describes a technology in which the driving force of an engine is shifted by a hydrostatic continuously variable transmission, then by a planetary gear transmission, and further by a sub-transmission.

[0005] The planetary gear transmission described in Patent Document 1 includes three planetary gear transmission units (referred to as planetary transmission mechanisms in the document) arranged in series along the same axis, with two clutch mechanisms extracting driving force from two of the three planetary gear transmission units. Specifically, the two clutch mechanisms are also arranged in series coaxially with the three planetary gear transmission units.

[0006] Furthermore, the auxiliary transmission described in Patent Document 1 is configured by combining two clutch mechanisms and two gear sets so that the driving force transmitted from the planetary gear transmission is switched into two stages, high and low. [Background Technology 2]

[0008] As a work vehicle configured with the above-mentioned structure, the following anti-rotation structure is recorded in patent document 2: it is equipped with a hydraulic speed change device, the aforementioned hydraulic speed change device has a first hydraulic clutch on the high-speed side and a second hydraulic clutch on the low-speed side so that the driving force of the future self-propelled propulsion shaft can be shifted into two levels of high and low. The aforementioned anti-rotation structure has a braking component that contacts the transmission body of the hydraulic speed change device when both the first hydraulic clutch and the second hydraulic clutch are in a disconnected state.

[0009] In Patent Document 2, a second gear that transmits driving force from a second hydraulic clutch is used as a transmission body, a piston is accommodated in an oil chamber inside a transmission case, and a brake member is provided at the distal end of the piston.

[0010] Patent document 2 provides a switching valve that selectively supplies working oil to one of the first hydraulic clutch and the second hydraulic clutch. When the switching valve does not supply working oil to either the first hydraulic clutch or the second hydraulic clutch, it supplies working oil to the piston to cause the brake component to protrude, thereby applying braking force to the transmission body.

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-159883.

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 5-164238.

[0013] [Technical Issue 1]

[0014] The problems with respect to [Background Art 1] are as follows.

[0015] The transmission structure described in Patent Document 1 can perform stepless speed change using a continuously variable transmission, can perform two-stage speed change using a planetary gear transmission, and can further perform two-stage speed change using an auxiliary transmission.

[0016] Furthermore, in the speed change structure described in Patent Document 1, since the planetary gear speed change device can reduce speed at a large reduction ratio, a continuously variable speed change device with a small capacity can be used.

[0017] However, the planetary gear transmission described in Patent Document 1 has three planetary gear transmission units and two clutch mechanisms arranged in series, which not only complicates the structure but also sometimes results in an increase in size in the front-to-back direction. In particular, the transmission structure for extracting the shifted driving force in the transmission structure described in Patent Document 1 is also complex, leaving room for improvement.

[0018] For these reasons, a work vehicle is required that can suppress an increase in the size of the transmission structure and simplify the transmission structure without impairing the effectiveness of using a hydrostatic continuously variable transmission and a planetary gear transmission.

[0019] [Technical Issue 2]

[0020] The problems with respect to [Background Art 2] are as follows.

[0021] The anti-rotation structure described in Patent Document 2 suppresses the following phenomenon: when the first hydraulic clutch and the second hydraulic clutch are in the disconnected state, as the propeller shaft rotates, a part of the hydraulic transmission device rotates with the propeller shaft, resulting in that the driving force of the propeller shaft is transmitted to the wheels and the vehicle moves at an extremely low speed.

[0022] However, in the structure of Patent Document 2, in order to suppress follow-up rotation, the transmission requires an oil chamber, which not only requires a piston and a brake component, but also requires a switching valve and an oil circuit for supplying working oil to the oil chamber when the two hydraulic clutches of the hydraulic transmission device are in a disconnected state. Therefore, the structure is complicated, resulting in an increase in the number of parts, which may lead to an increase in cost.

[0023] For these reasons, there is a need for a work vehicle that can suppress the disadvantage of the vehicle body moving at a low speed while the hydraulic clutch is in a disengaged state, without complicating the structure for suppressing follow-up. Summary of the Invention

[0024] The technical solution corresponding to [Technical Problem 1] is as follows.

[0025] The work vehicle of the present invention is characterized in that it is provided with a hydrostatic continuously variable transmission device for steplessly changing the driving force of the engine, and is provided with a plurality of planetary gear transmission devices for changing the driving force changed by the aforementioned continuously variable transmission device. In order to respectively extract the driving force from the plurality of aforementioned planetary gear transmission devices, it is provided with a plurality of clutch mechanisms corresponding to the plurality of aforementioned planetary gear transmission devices, and is provided with a travel speed change portion for changing the driving force transmitted from the plurality of aforementioned clutch mechanisms and transmitting it to a travel mechanism. The plurality of aforementioned planetary gear transmission devices are arranged in a parallel positional relationship, and the plurality of aforementioned planetary gear transmission devices, the plurality of aforementioned clutch mechanisms, and the aforementioned travel speed change portion are accommodated in a transmission case.

[0026] According to this characteristic structure, the engine's driving force is continuously variable-speeded by the continuously variable transmission. This shifted driving force can be significantly reduced by each of the multiple planetary gear transmissions, enabling the use of a smaller capacity continuously variable transmission. Furthermore, the driving force shifted by the multiple planetary gear transmissions can be individually extracted and transmitted to the travel transmission unit via their corresponding clutch mechanisms. In particular, the multiple planetary gear transmissions are arranged in parallel, reducing the front-to-back dimensions of the space housing the planetary gear transmissions compared to a configuration in which multiple planetary gear transmissions are arranged in series.

[0027] Therefore, a work vehicle is constructed that can suppress an increase in size of a transmission structure and simplify the transmission structure without impairing the effectiveness of using a hydrostatic continuously variable transmission and a planetary gear transmission.

[0028] As another structure, it can also be that the aforementioned engine, the aforementioned continuously variable transmission, and the plurality of aforementioned planetary gear transmissions are arranged in this order along the front-to-rear direction of the vehicle body, the aforementioned continuously variable transmission has a variable capacity hydraulic pump driven by the aforementioned engine, and a hydraulic motor rotated by means of working oil supplied from the aforementioned hydraulic pump, and the input shaft of the aforementioned hydraulic pump and the output shaft of the aforementioned hydraulic motor are formed to protrude in the direction where the aforementioned planetary gear transmission is arranged, the drive shaft for transmitting the driving force of the aforementioned engine is arranged to pass through the aforementioned continuously variable transmission in the front-to-rear direction, and is equipped with a driving gear mechanism and a branch gear mechanism, the aforementioned driving gear mechanism transmits the driving force from the passing portion of the aforementioned drive shaft passing through the aforementioned continuously variable transmission to the aforementioned input shaft, and the aforementioned branch gear mechanism transmits the driving force from the aforementioned output shaft to the plurality of aforementioned planetary gear transmissions.

[0029] Thus, the drive shaft transmitting the driving force of the engine passes through the continuously variable transmission in the front-to-rear direction. The driving force from the through-portion is transmitted to the input shafts of the multiple planetary gear transmissions via the drive gear mechanism, thereby enabling speed shifting by the continuously variable transmission. Furthermore, the driving force from the output shaft of the continuously variable transmission is transmitted to the multiple planetary gear transmissions via the branch gear mechanism, thereby enabling speed shifting by the multiple planetary gear transmissions.

[0030] As another structure, it is also possible that as multiple aforementioned planetary gear transmissions, a first planetary gear transmission is provided with a high-speed side with a small transmission rate, and a second planetary gear transmission is provided with a low-speed side with a large transmission rate; as multiple aforementioned clutch mechanisms, a first clutch mechanism is provided for intermittently driving the force from the aforementioned first planetary gear transmission, and a second clutch mechanism is provided for intermittently driving the force from the aforementioned second planetary gear transmission; and the aforementioned travel speed change portion is provided with a sub-speed change device for changing the speed of the driving force from the aforementioned first clutch mechanism and the aforementioned second clutch mechanism.

[0031] Thus, by selectively operating the first clutch mechanism and the second clutch mechanism, the driving force shifted by the first planetary gear transmission and the driving force shifted by the second planetary gear transmission can be taken out, and the auxiliary transmission can be further shifted and transmitted to the travel mechanism.

[0032] As another structure, the continuously variable transmission device may include a variable capacity hydraulic pump driven by the engine, a hydraulic motor rotated by the working oil supplied from the hydraulic pump, and a port block forming a hydraulic circuit, wherein the hydraulic circuit is formed between the hydraulic pump and the hydraulic motor, and the hydraulic pump and the hydraulic motor are arranged on the rear surface side of the port block.

[0033] Thus, by arranging the hydraulic pump and the hydraulic motor on the rear surface side of the port block, it is easy to configure, for example, so that the input shaft of the hydraulic pump and the output shaft of the hydraulic motor protrude rearward.

[0034] The technical solution corresponding to [Technical Problem 2] is as follows.

[0035] The work vehicle of the present invention is characterized in that it has a wet first clutch mechanism, a wet second clutch mechanism, an intermediate rotating component, and a connecting portion. The aforementioned wet first clutch mechanism intermittently transmits the travel driving force transmitted from the first shaft to the travel mechanism, and the aforementioned wet second clutch mechanism intermittently transmits the travel driving force transmitted from the second shaft to the travel mechanism. The aforementioned intermediate rotating component rotates relative to the aforementioned first shaft by means of a drag torque accompanying the rotation of the first shaft, and the aforementioned connecting portion transmits the rotational force of the aforementioned intermediate rotating component to the output portion of the aforementioned second clutch mechanism.

[0036] In the above configuration, when the first clutch mechanism is set to the disengaged state, the drag torque acting on the friction plates of the first clutch mechanism is transmitted to the travel drive system. Similarly, when the second clutch mechanism is set to the disengaged state, the drag torque acting on the friction plates of the second clutch mechanism transmits driving force to the travel drive system.

[0037] In contrast, according to the characteristic structure, the rotational force of the intermediate rotating member that rotates due to the drag torque accompanying the rotation of the first transmission shaft is transmitted to the output portion of the second clutch mechanism via the connecting portion. For example, the speed difference between the rotational speed of the output portion of the second clutch and the rotational speed transmitted from the connecting portion can be increased. In addition, by reversing the rotational direction of the driving force transmitted from the connecting portion, the torque that suppresses each other's rotation can be used to offset the driving force transmitted to the travel drive system. In other words, by utilizing the drag torque generated at the two clutch mechanisms in the disconnected state, even though the structure does not have an actuator, it is possible to reduce or offset the rotational force transmitted to the travel drive system.

[0038] As a result, a work vehicle is configured that suppresses the disadvantage of the vehicle body moving at low speed when the hydraulic clutch is in the disengaged state without complicating the structure for suppressing follow-up rotation.

[0039] As a structure based on the above structure, it can also be provided with a first planetary gear transmission device and a second planetary gear transmission device, the above-mentioned first planetary gear transmission device changes the speed of the travel driving force and transmits it to the above-mentioned first shaft, and the above-mentioned second planetary gear transmission device changes the speed of the travel driving force and transmits it to the above-mentioned second shaft, the above-mentioned first clutch mechanism is configured to transmit the driving force of the above-mentioned first shaft as the forward driving force to the above-mentioned travel mechanism as the forward driving force in the transmission state, the above-mentioned second clutch mechanism has a forward clutch part and a reverse clutch part, the above-mentioned forward clutch part transmits the driving force of the above-mentioned second shaft as the forward driving force to the above-mentioned travel mechanism as the reverse driving force in the transmission state, and the above-mentioned reverse clutch part transmits the driving force of the above-mentioned second shaft as the reverse driving force to the above-mentioned travel mechanism as the reverse driving force in the transmission state, the above-mentioned second clutch mechanism has a reverse output gear that outputs the reverse driving force from the above-mentioned reverse clutch part, and is configured so that the above-mentioned reverse output gear meshes with the reverse transmission gear, thereby transmitting the reverse driving force to the above-mentioned travel mechanism.

[0040] As a result, the forward driving force is transmitted from the first planetary gear transmission via the first shaft to the first clutch mechanism. In the transmission state, the first clutch mechanism transmits the driving force of the first shaft as the forward driving force to the travel mechanism. Furthermore, the forward driving force is transmitted from the second planetary gear transmission via the second shaft to the second clutch mechanism. In the transmission state, the forward clutch portion of the second clutch mechanism transmits the driving force of the second shaft as the forward driving force to the travel mechanism, and in the transmission state, the reverse clutch portion of the second clutch mechanism transmits the reverse driving force to the reverse transmission gear engaged with the reverse output gear.

[0041] As a configuration in addition to the above configuration, the connecting portion may be a gear portion that rotates by a rotational force of the intermediate rotating member, and the gear portion may be engaged with the reverse transmission gear.

[0042] Therefore, when the first clutch mechanism and the second clutch mechanism are in the disconnected state, as the first shaft rotates, the drag torque acts from the first clutch mechanism in the forward direction relative to the travel mechanism, and as the second shaft rotates, the drag torque acts from the forward clutch part of the second clutch in the forward direction relative to the travel mechanism, and as the second shaft rotates, the drag torque acts from the reverse clutch part of the second clutch in the reverse direction relative to the travel mechanism.

[0043] Considering a comparative structure without an intermediate rotating member, in this comparative structure, drag torque acts in the forward direction from both clutch mechanisms, while drag torque acts in the reverse direction from one clutch mechanism. Therefore, the drag torque in the forward direction is greater than the drag torque in the reverse direction, which can lead to a disadvantageous low-speed vehicle movement. In contrast, by meshing a gear portion, which rotates due to the rotational force of the rotating member rotated by the drag torque of the first shaft, with the reverse transmission gear, the drag torque acting in the reverse direction on the travel mechanism in the aforementioned comparative structure is increased, thereby offsetting the forward and reverse drag torques.

[0044] As a configuration in addition to the above configuration, the gear portion may be formed on an outer periphery of the intermediate rotating member.

[0045] Thus, the rotational force of the intermediate rotating member can be directly transmitted to the reverse transmission gear from the gear portion formed on the outer periphery of the intermediate rotating member, and the transmission structure can be simplified.

[0046] As a structure based on the above structure, it can also be that the driving speed transmitted from the above-mentioned first shaft to the above-mentioned travel mechanism when the above-mentioned first clutch mechanism is in a transmission state is faster than the driving speed transmitted from the above-mentioned second shaft to the above-mentioned travel mechanism when the forward clutch part of the above-mentioned second clutch mechanism is in a transmission state, and the above-mentioned intermediate rotating component has a friction plate that is rotatably supported on the above-mentioned first shaft and rotates integrally with the intermediate rotating component, and the above-mentioned friction plate is arranged adjacent to the friction component that rotates integrally with the clutch housing of the above-mentioned first clutch mechanism.

[0047] Thus, by setting the first clutch mechanism to a transmission state, the vehicle can travel at a predetermined speed, and by setting the forward clutch portion of the second clutch mechanism to a transmission state, the vehicle can travel at a speed lower than the predetermined speed. Furthermore, the friction plate, which rotates integrally with the intermediate rotating member, is disposed adjacent to the friction member, which rotates integrally with the clutch housing of the first clutch mechanism. Thus, when the clutch housing of the first clutch mechanism rotates due to the drag torque associated with the rotation of the first shaft, the rotation can be transmitted to the intermediate rotating member.

[0048] As a configuration in addition to the above configuration, a sub-transmission device for changing the speed of the driving force from the first clutch mechanism and the second clutch mechanism may be provided.

[0049] Thus, the travel driving force from the first clutch mechanism and the travel driving force from the second clutch mechanism can be shifted in speed via the auxiliary transmission device and transmitted to the travel mechanism.

[0050] As a structure based on the above structure, it can also be a structure with a hydrostatic continuously variable transmission device, which changes the driving force of the engine steplessly and transmits it as a driving force relative to the first planetary gear transmission device and the second planetary gear transmission device. The first planetary gear transmission device and the second planetary gear transmission device are accommodated in the transmission case in a parallel position relationship.

[0051] As a result, the driving force from the engine can be continuously variable-speeded and transmitted to the first planetary gear transmission and the second planetary gear transmission by means of a hydrostatic continuously variable transmission, and the first planetary gear transmission and the second planetary gear transmission are accommodated in the transmission case in a parallel positional relationship, thereby shortening the front-to-rear length of the transmission case.

[0052] As a structure based on the above structure, it can also be that the aforementioned engine and the aforementioned continuously variable transmission are arranged in this order along the front-to-rear direction, and the aforementioned first planetary gear transmission and the aforementioned second planetary gear transmission are arranged in a parallel positional relationship at a position farther rearward than the aforementioned continuously variable transmission, and the aforementioned continuously variable transmission has a variable capacity hydraulic pump driven by the aforementioned engine and a hydraulic motor rotated by means of working oil supplied from the aforementioned hydraulic pump, the input shaft of the aforementioned hydraulic pump and the output shaft of the aforementioned hydraulic motor are formed to protrude rearward from the continuously variable transmission, and the drive shaft for transmitting the driving force of the aforementioned engine is configured to pass through the aforementioned continuously variable transmission in the front-to-rear direction, and is equipped with a driving gear mechanism and a branch gear mechanism, the aforementioned driving gear mechanism transmits the driving force of the passing portion of the aforementioned drive shaft passing through the aforementioned continuously variable transmission to the aforementioned input shaft, and the aforementioned branch gear mechanism transmits the driving force of the aforementioned output shaft to the aforementioned first planetary gear transmission and the aforementioned second planetary gear transmission.

[0053] Thus, the driving speed of the hydraulic motor can be adjusted by adjusting the amount of hydraulic oil supplied to the hydraulic motor from the variable displacement hydraulic pump, which is driven by the engine's driving force. Furthermore, the input shaft and output shaft of the hydraulic pump are positioned to project rearward from the continuously variable transmission. This allows the driving force from the drive shaft, which passes through the continuously variable transmission, to be transmitted from the drive gear mechanism to the input shaft, and then from the branch gear mechanism to the first and second planetary transmissions.

[0054] As a structure based on the above structure, the continuously variable transmission device may also include a variable capacity hydraulic pump driven by the engine, a hydraulic motor rotated by the working oil supplied from the hydraulic pump, and a port block forming a hydraulic circuit, the hydraulic circuit being formed between the hydraulic pump and the hydraulic motor, and the hydraulic pump and the hydraulic motor being arranged on the rear surface side of the port block.

[0055] Thus, by arranging the hydraulic pump and the hydraulic motor on the rear surface side of the port block, for example, it is easy to configure so that the input shaft of the hydraulic pump and the output shaft of the hydraulic motor protrude rearward. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a side view of the tractor.

[0057] Figure 2 It is a plan view showing the arrangement of the clutch housing and the continuously variable transmission housing.

[0058] Figure 3 It is a cross-sectional view of the continuously variable transmission case.

[0059] Figure 4 It is a diagram schematically showing a transmission structure.

[0060] Figure 5 This is a diagram schematically showing a transmission structure of another embodiment (a).

[0061] Figure 6 It is a diagram schematically showing a transmission structure of another embodiment (b).

[0062] Figure 7 This is a diagram schematically showing an intermediate rotating member and a connecting portion in another embodiment (b).

[0063] Figure 8 It is a diagram showing a first clutch mechanism, a second clutch mechanism, and a gear portion according to another embodiment (b).

[0064] Figure 9 This is a diagram showing a gear portion and a second reverse input gear according to another embodiment (b). DETAILED DESCRIPTION

[0065] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0066] [Overall structure]

[0067] like Figure 1 As shown, a tractor serving as a work vehicle is provided with a pair of left and right front wheels 1 and a pair of left and right rear wheels 2 on a traveling vehicle body A. An engine 4 is installed inside an engine hood 3 at the front of the traveling vehicle body A. A cab B having a cab 5 is located at the rear of the traveling vehicle body A. In this tractor, the left and right front wheels 1 and the left and right rear wheels 2 function as a propulsion mechanism.

[0068] like Figure 1 、 Figure 2 As shown in the figure, F stands for "front", B stands for "back", U stands for "up", D stands for "down", R stands for "right", and L stands for "left".

[0069] Inside the cockpit 5 , there are provided a driver's seat 7 disposed between the left and right rear fenders 6 , a steering wheel 8 disposed in front of the driver's seat 7 , and operating levers and switches near the driver's seat 7 .

[0070] like Figures 1 to 4 As shown, this tractor has a main clutch housing 10, a continuously variable transmission housing 11, and a transmission 12 connected in this order on the rear side of the engine 4. The transmission 12 houses a travel transmission device 50 (an example of a travel transmission unit) that transmits driving force to the left and right front wheels 1 and the rear wheels 2.

[0071] At the rear of the transmission case 12 are a pair of left and right lifting arms 14, which swing upward and downward by the driving force of a hydraulic cylinder 13, and a pair of left and right lower links 15. The swing ends of the lifting arms 14 and the lower links 15 are suspended and connected by lifting rods 16. A power takeoff shaft 17 is provided on the rear surface of the transmission case 12 for extracting the driving force to the outside.

[0072] This tractor has a rotary tillage device, a plow, and other working devices connected to the rear ends of left and right low links 15, and is configured so that the working devices can be raised and lowered by raising and lowering the left and right lift arms 14. Furthermore, when the rotary tillage device is used as the working device, a drive shaft is provided to transmit driving force between the power take-off shaft 17 and the rotary tillage device.

[0073] 〔Speed ​​Shifting Structure〕

[0074] In this tractor, Figures 1 to 4 As shown, the main clutch housing 10 houses a main clutch mechanism 18, and the continuously variable transmission housing 11 houses a hydrostatic continuously variable transmission 20. Furthermore, the transmission 12 houses a first planetary gear transmission Q1 (high-speed side with a slower transmission speed), a second planetary gear transmission Q2 (low-speed side with a faster transmission speed), a first clutch mechanism C1, a second clutch mechanism C2, a travel transmission 50, and a working transmission 70.

[0075] like Figure 4 As shown, in this transmission structure, the continuously variable transmission 20, the first planetary gear transmission Q1, the second planetary gear transmission Q2, the first clutch mechanism C1, the second clutch mechanism C2, and the transmission gears connected thereto constitute a main transmission 50A. Furthermore, the first transmission portion 54, the second transmission portion 55, and the transmission gears connected thereto constitute an auxiliary transmission 50B.

[0076] Furthermore, it has a travel transmission structure for transmitting the driving force of the future propulsion transmission device 50 from the rear wheel drive shaft 53 to the rear wheel differential gear 61 and then to the rear wheel 2, and it has a travel transmission structure for transmitting the driving force from the rear wheel drive shaft 53 to the front wheel differential gear 62 and then to the front wheel 1.

[0077] In addition, the driving transmission structure for transmitting driving force to the front wheel 1 is constructed as follows: the driving force from the rear wheel drive shaft 53 is transmitted to the front wheel drive shaft 64 via the front wheel drive gear 63, and from the front wheel drive shaft 64 to the front wheel drive shaft 66 via the front wheel speed change device 65, and then to the front wheel differential gear 62.

[0078] In particular, in this structure, the first planetary gear transmission Q1 and the second planetary gear transmission Q2 are specific examples of a plurality of planetary gear reduction devices, and the first clutch mechanism C1 and the second clutch mechanism C2 are specific examples of clutch mechanisms for intermittently transmitting the driving force from the planetary gear reduction mechanisms.

[0079] The main clutch mechanism 18 is configured to be freely set to a state of transmitting or disconnecting the driving force of the engine 4 based on the operator's operation. The continuously variable transmission 20 can continuously change the travel speed based on the operator's shift operation, and can also stop the vehicle body A without outputting driving force.

[0080] [Main transmission: continuously variable transmission]

[0081] like Figure 3 、 Figure 4 As shown, the continuously variable transmission 20 has a structure in which a variable displacement hydraulic pump P, a hydraulic motor M, and a port block 23 are housed in the continuously variable transmission case 11. The driving force of the engine 4 is transmitted to the variable displacement hydraulic pump P via an input shaft 21. The hydraulic motor M transmits the variable displacement driving force to the first planetary gear transmission Q1 and the second planetary gear transmission Q2 via an output shaft 22. The port block 23 forms a pair of oil passages for supplying and discharging hydraulic oil between the hydraulic pump P and the hydraulic motor M. Furthermore, the input shaft 21 and the output shaft 22 are arranged in a parallel position with their protruding ends facing rearward.

[0082] The hydraulic pump P includes a plurality of retractable plungers in a pump body 24a that rotates integrally with the input shaft 21. The hydraulic pump P also includes a movable swash plate 24b that controls the amount of expansion and contraction of the plungers when the pump body 24a is driven and rotated. A servo piston (not shown) that controls the position of the movable swash plate 24b is supported by the continuously variable transmission case 11.

[0083] The hydraulic motor M includes a plurality of extendable and retractable plungers in a motor body 26 a that rotates integrally with the output shaft 22 , and includes a fixed swash plate 26 b that converts the extension and retraction of the plungers into rotational motion.

[0084] With this structure, when the pump body 24a is driven to rotate while the movable swash plate 24b is set at a predetermined angle (relative to the pump axis), the ends of the multiple plungers of the hydraulic pump P contact the movable swash plate 24b as the pump body 24a rotates. As the pump body 24a rotates, the ends of the multiple plungers of the hydraulic pump P contact the movable swash plate 24b, causing the pump body 24a to contract sequentially. This contraction causes hydraulic oil to be delivered to one of the pair of oil passages in the port block 23. The pressure of this hydraulic oil causes the multiple plungers of the hydraulic motor M to extend sequentially. This extension, in turn, causes the motor body 26a to rotate due to the reaction force from the fixed swash plate 26b. Furthermore, as the hydraulic motor M rotates, the plungers of the hydraulic motor M contract, and as this contraction occurs, the hydraulic oil returns to the hydraulic pump P through the other flow passage.

[0085] In this continuously variable transmission 20, the angle of the movable swash plate 24b is adjusted by the operation of the servo piston, thereby controlling the discharge rate of hydraulic oil and enabling the rotational speed of the hydraulic motor M to be arbitrarily set. Furthermore, by setting the angle of the movable swash plate 24b to be perpendicular to the input axis, the supply and discharge of hydraulic oil between the hydraulic pump P and the hydraulic motor M can be stopped, thereby also stopping the hydraulic motor M.

[0086] like Figure 3 、 Figure 4 As shown, the main drive shaft 31 that transmits the driving force from the engine 4 via the main clutch mechanism 18 is configured to penetrate the continuously variable transmission device 20 in the front-to-rear direction, and has a drive gear mechanism 32 that transmits the driving force from the main drive shaft 31 to the input shaft 21 of the continuously variable transmission device 20.

[0087] Furthermore, a branch gear mechanism 33 is provided for transmitting the driving force from the output shaft 22 of the continuously variable transmission 20 to the first planetary gear transmission Q1 and the second planetary gear transmission Q2.

[0088] [Main transmission: planetary gear transmission]

[0089] like Figure 4 As shown, the first planetary gear transmission Q1 and the second planetary gear transmission Q2 are housed in the transmission case 12 in a horizontally parallel relationship. A first clutch mechanism C1 is coaxially arranged with the first output shaft 46a to interrupt the driving force from the first output shaft 46a of the first planetary gear transmission Q1. Similarly, a second clutch mechanism C2 is coaxially arranged with the second output shaft 46b to interrupt the driving force from the second output shaft 46b of the second planetary gear transmission Q2.

[0090] That is, the first planetary gear transmission Q1 has a first sun gear 42a on the first input shaft 41a, and has a plurality of first planetary gears 44a between the first ring gear 43a and the first sun gear 42a, which are arranged to rotate freely coaxially with the first input shaft 41a, so that the gear portion formed by the first bracket 45a supporting the plurality of first planetary gears 44a meshes with the interlocking gear portion 34 of the main drive shaft 31.

[0091] Furthermore, the first planetary gear transmission Q1 includes a first output shaft 46 a that rotates integrally with the first ring gear 43 a .

[0092] The second planetary gear transmission Q2 has a second sun gear 42b on the second input shaft 41b, and has a plurality of second planetary gears 44b between the second ring gear 43b and the second sun gear 42b, which are arranged to rotate freely coaxially with the second input shaft 41b, so that the gear portion formed on the second bracket 45b supporting the plurality of second planetary gears 44b engages with the interlocking gear portion 34 of the main drive shaft 31.

[0093] The second planetary gear transmission Q2 includes a second output shaft 46b that rotates integrally with the second carrier 45b.

[0094] [Main transmission: clutch mechanism]

[0095] like Figure 4 As shown, the first clutch mechanism C1 is a wet friction multi-plate type that can be switched between a transmission state (transmitting driving force) and a disconnection state (interrupting driving force) by the supply and discharge of hydraulic oil. The second clutch mechanism C2 is a wet friction multi-plate type clutch unit that can be switched between a transmission state (transmitting driving force) and a disconnection state (interrupting driving force) by the supply and discharge of hydraulic oil.

[0096] The intermediate shaft 35 is provided with a cylindrical shape and is rotatable coaxially with the main drive shaft 31 . When the first clutch mechanism C1 is set to the transmission state, the high-speed driving force from the first output shaft 46a of the first planetary gear transmission Q1 is transmitted to the intermediate shaft 35 via the first transmission gear 36 .

[0097] One of the two clutch parts of the second clutch mechanism C2 ( Figure 4 The clutch portion (on the right side) is configured for forward transmission, and is configured to transmit the low-speed driving force from the second output shaft 46b of the second planetary gear change device Q2 to the intermediate shaft 35 via the second transmission gear 37 by setting the clutch portion to the transmission state.

[0098] In addition, the other of the two clutch parts of the second clutch mechanism C2 ( Figure 4 The left side of the center) is configured for reverse transmission, and is configured so that the low-speed driving force from the second output shaft 46b of the second planetary gear transmission Q2 is transmitted to the first pair of shafts 51 via the third transmission gear 38 by setting the clutch portion to the transmission state.

[0099] The first pair of shafts 51 are provided in a posture parallel to the intermediate shaft 35 , and the second pair of shafts 52 are provided in a posture parallel to the first pair of shafts 51 . A rear wheel drive shaft 53 is provided coaxially with the first pair of shafts 51 .

[0100] [Auxiliary transmission]

[0101] The auxiliary transmission 50B is configured to include a first transmission portion 54, a second transmission portion 55, and transmission gears connected thereto. The first transmission portion 54 is provided between the first pair of shafts 51 and the rear wheel drive shaft 53, and the second transmission portion 55 is provided coaxially with the second pair of shafts 52. The auxiliary transmission 50B is capable of three speed changes: high, medium, and low, and is also capable of a reverse transmission state.

[0102] The first speed change portion 54 and the second speed change portion 55 are configured as manually operable meshing clutches.

[0103] The auxiliary transmission device 50B has a high-speed transmission gear 56 and a medium-speed transmission gear 57 between the intermediate shaft 35 and the first speed change unit 54, a first low-speed transmission gear 58 between the first pair of shafts 51 and the second pair of shafts 52, and a second low-speed transmission gear 59 between the second speed change unit 55 and the rear wheel drive shaft 53.

[0104] [Transmission method]

[0105] Due to the configuration of the forward transmission 50, the driving force of the engine 4 is continuously variable at the continuously variable transmission 20. By setting the first clutch mechanism C1 to the transmission state, the high-speed driving force, which has been shifted by the first planetary gear transmission Q1, is transmitted to the intermediate shaft 35 via the first transmission gear 36. Furthermore, by setting one clutch portion of the second clutch mechanism C2 to the transmission state, the low-speed driving force is transmitted to the intermediate shaft 35 via the second transmission gear 37. Furthermore, by setting the other clutch portion of the second clutch mechanism C2 to the transmission state, the driving force for reverse travel is transmitted to the first pair of shafts 51.

[0106] In the main transmission 50A, the control mode is set so that the first clutch mechanism C1 and the second clutch mechanism C2 are not simultaneously set to the transmission state. Similarly, the operation mode is set so that the first speed change portion 54 and the second speed change portion 55 are not simultaneously set to the transmission state.

[0107] In the auxiliary transmission device 50B, when the driving force of one of the first clutch mechanism C1 and the second clutch mechanism C2 is transmitted to the intermediate shaft 35, the first transmission unit 54 transmits the driving force from the high-speed transmission gear 56 to the rear wheel drive shaft 53, thereby transmitting the high-speed rotating driving force to the rear wheel 2 and the front wheel 1.

[0108] Similarly, when the driving force of one of the first clutch mechanism C1 and the second clutch mechanism C2 is transmitted to the intermediate shaft 35, the first speed change unit 54 transmits the driving force from the medium-speed transmission gear 57 to the rear wheel drive shaft 53, thereby transmitting the medium-speed rotating driving force to the rear wheel 2 and the front wheel 1.

[0109] Furthermore, when the driving force of either the first clutch mechanism C1 or the second clutch mechanism C2 is transmitted to the intermediate shaft 35, the first pair of shafts 51 is rotated by the driving force transmitted by the high-speed transmission gear 56 without being transmitted via the first speed change unit 54. Therefore, in this state, the second speed change unit 55 is set to the transmission state, whereby the low-speed driving force reduced by the first low-speed transmission gear 58 and the second low-speed transmission gear 59 is transmitted to the rear wheel drive shaft 53, and the low-speed rotational driving force is transmitted to the rear wheels 2 and the front wheels 1.

[0110] Furthermore, with the other of the two clutch portions of the second clutch mechanism C2 set to the transmission state, the driving force from the third transmission gear 38 is transmitted to the first pair of shafts 51. The first speed change portion 54 is operated to transmit the driving force of the first pair of shafts 51 to the rear-wheel drive shaft 53, thereby transmitting the reverse driving force to the rear wheels 2 and the front wheels 1. Furthermore, in the second clutch mechanism C2, the operating position for transmitting the driving force from the first pair of shafts 51 to the rear-wheel drive shaft 53 is the same as the position for transmitting the driving force from the high-speed transmission gear 56 to the rear-wheel drive shaft 53.

[0111] The front-wheel transmission 65 distributes the driving force of the front-wheel propeller shaft 64 between the front-wheel drive shafts 66 and includes a constant-speed transmission gear 65a, a speed-increasing transmission gear 65b, and a switching clutch mechanism 65c. The switching clutch mechanism 65c is a hydraulic multi-plate type that can selectively operate between a state of transmitting driving force and a state of interrupting driving force by the supply and discharge of hydraulic oil.

[0112] According to this configuration, when vehicle body A is moving straight ahead, the switching clutch mechanism 65c controls the constant-speed transmission gear 65a to the transmission state, thereby equalizing the peripheral speeds of the front wheels 1 and the rear wheels 2. Furthermore, when the steering wheel 8 is operated beyond a set amount, the switching clutch mechanism 65c controls the speed-increasing transmission gear 65b to the transmission state, thereby increasing the peripheral speed of the front wheels 1 relative to the rear wheels 2 and reducing the turning radius. Furthermore, when traveling in a state where driving force is not being transmitted to the front wheels 1 (two-wheel drive mode), the switching clutch mechanism 65c is set to a state that cuts off the transmission of driving force.

[0113] [Operation speed change device]

[0114] A transmission structure for transmitting the driving force from the main drive shaft 31 to the working pump 72 via the pump drive gear 71 is provided at a rear position of the intermediate shaft 35 .

[0115] The working speed change device 70 includes a hydraulic multi-plate working clutch 73 that intermittently transmits the driving force from the main drive shaft 31, a working speed change unit 74, a working speed change shaft 75 that transmits the driving force from the working speed change unit 74, and an output gear 76 that transmits the driving force from the working speed change shaft 75 to the power take-off shaft 17.

[0116] The working speed change unit 74 includes two working speed change clutches 74a arranged coaxially with the working speed change shaft 75, a working countershaft 74b externally fitted to the rear wheel drive shaft 53 for relative rotation, a first working gear 74c that transmits driving force from the working clutch 73 to the working countershaft 74b, and three second working gears 74d that transmit driving force from the working countershaft 74b to corresponding working speed change clutches in the two working speed change clutches 74a. Each of the two working speed change clutches 74a is a manually operated meshing clutch.

[0117] In the working speed change section 74, when the working clutch 73 is set to the transmission state, the two working speed change clutches 74a can be selectively operated to set the working speed change section 74 to one of the reduced speed transmission state, the intermediate speed transmission state, the high speed transmission state, and the reverse transmission state, thereby transmitting the driving force transmitted from the main drive shaft 31 to the working speed change shaft 75. Furthermore, the working pump 72 is configured to supply the lubricating oil stored in the transmission case 12 as hydraulic fluid.

[0118] Furthermore, the hydraulic oil of the working pump 72 is supplied to the first clutch mechanism C1 , the second clutch mechanism C2 , the switching clutch mechanism 65 c , and the working clutch 73 described above via a control valve (not shown).

[0119] [Effects of the implementation method]

[0120] The driving force of the engine 4 is continuously variable-speeded by the continuously variable transmission 20. The thus-varied driving force can be significantly reduced in speed by both the first planetary gear transmission Q1 and the second planetary gear transmission Q2, thereby enabling the use of a smaller capacity device for the continuously variable transmission 20. Furthermore, the driving force thus-varied by the first planetary gear transmission Q1 and the second planetary gear transmission Q2 can be extracted via the corresponding first clutch mechanism C1 and second clutch mechanism C2, respectively, and transmitted to the travel transmission 50.

[0121] In particular, because the first planetary gear transmission Q1 and the second planetary gear transmission Q2 are arranged in parallel, the front-to-back dimensions of the space housing the planetary gear transmissions can be reduced compared to a structure in which multiple planetary gear transmissions are arranged in series. This allows for a tractor with a simplified transmission structure while suppressing the size of the transmission structure without compromising the effectiveness of the hydrostatic continuously variable transmission 20 and the planetary gear transmissions.

[0122] [Alternative Implementation Method]

[0123] In addition to the above-described embodiment, the present invention may also be configured as follows (configurations having the same functions as those in the embodiment are denoted by the same numbers and reference numerals as those in the embodiment).

[0124] (a) If Figure 5 As shown, a transmission 12 for a tractor (an example of a work vehicle) is constructed without the main clutch housing 10 and main clutch mechanism 18 described in the embodiment. In this alternative embodiment (a), the transmission 12 has a configuration that is basically the same as that of the embodiment, except for the main clutch housing 10 and main clutch mechanism 18.

[0125] In the structure of this other embodiment (a), when the engine 4 is started or the moving vehicle body A is stopped, the angle of the movable inclined plate 24b of the continuously variable transmission device 20 is set to a posture orthogonal to the pump axis, thereby setting the control to stop the flow of the working oil, or setting the first clutch mechanism C1 and the second clutch mechanism C2 to be in the disconnected state at the same time.

[0126] Thus, in another embodiment (a), the parts constituting the main clutch housing 10 and the main clutch mechanism 18 described in the embodiment are not required, so the number of work vehicles can be reduced, the dimensions of the vehicle body in the front-rear direction can be shortened to miniaturize the vehicle body, and the vehicle body can also be made lightweight.

[0127] (b) If Figure 6 As shown, similar to the previously described other embodiment (a), the transmission 12 of a tractor (an example of a work vehicle) is configured without the main clutch housing 10 and main clutch mechanism 18 described in the embodiment. In particular, the configuration is such that when both the wet-type first clutch mechanism C1 and the wet-type second clutch mechanism C2 are in the disengaged state, the drag torque acting from the first output shaft 46a (an example of a first shaft) and the second output shaft 46b (an example of a second shaft) respectively suppresses the inconvenience of the vehicle body A moving at a low speed.

[0128] like Figure 6 、 Figure 7As shown, the first clutch mechanism C1 transmits the driving force of the first output shaft 46a (an example of the first shaft) as forward driving force from the first forward output gear 36a to the first forward input gear 36b of the intermediate shaft 35 in the transmission state.

[0129] Furthermore, the second clutch mechanism C2 includes a forward clutch portion C2f and a reverse clutch portion C2r. In the transmission state, the forward clutch portion C2f transmits the driving force of the second output shaft 46b (an example of the second shaft) as forward driving force from the second forward output gear 37a to the second forward input gear 37b of the intermediate shaft 35. In the transmission state, the reverse clutch portion C2r transmits the driving force of the second output shaft 46b as reverse driving force from the second reverse output gear 38a (an example of a reverse output gear) to the second reverse input gear 38b (an output portion, an example of a reverse transmission gear) of the first pair of shafts 51.

[0130] In addition, the transmission 12 is constructed so that the driving speed transmitted to the front wheels 1 and the rear wheels 2 when the first clutch mechanism C1 is set to the transmission state is faster than the driving speed transmitted to the front wheels 1 and the rear wheels 2 when the forward clutch part C2f of the second clutch mechanism C2 is set to the transmission state.

[0131] In this alternative embodiment (b), if Figures 7 to 9 As shown, an intermediate rotating component 85 that acts as a drag torque with the rotation of the first output shaft 46a is constructed to suppress the following phenomenon: the rotational force of the intermediate rotating component 85 is transmitted to the second reverse output gear 38a (an example of a reverse transmission gear), thereby transmitting the travel driving force to the left and right front wheels 1 and the left and right rear wheels 2 serving as the travel mechanism.

[0132] The first clutch mechanism C1 includes a first sleeve 36s disposed within the first clutch housing CH1, which rotates integrally with the first forward output gear 36a. Furthermore, the mechanism comprises a plurality of driving-side friction plates 81 that fit within a plurality of first slits 80a formed on the outer circumference of the first clutch housing CH1; a plurality of driven-side friction plates 82 that are externally fitted to the first sleeve 36s to transmit torque; and a first piston 83 that presses the driving-side friction plates 81 and the driven-side friction plates 82 together by supplying pressurized oil.

[0133] The first clutch housing CH1 of the first clutch mechanism C1 rotates integrally with the first output shaft 46a, and has alternately arranged driving side friction plates 81 and driven side friction plates 82. An oil passage for supplying and discharging hydraulic oil to and from the first piston 83 is formed inside the first output shaft 46a.

[0134] The hydraulic oil is then supplied to the first piston 83, creating a transmission state in which the plurality of driving-side friction plates 81 and the plurality of driven-side friction plates 82 are in press-contact, transmitting the driving force of the first output shaft 46a to the first forward output gear 36a. Furthermore, as the hydraulic oil is discharged, the pressure from the piston is released, separating the plurality of driving-side friction plates 81 and the plurality of driven-side friction plates 82, achieving a disconnected state in which no driving force is transmitted.

[0135] The second clutch mechanism C2 is constructed by accommodating a forward clutch component C2f and a reverse clutch component C2r within the second clutch housing CH2. The forward clutch component C2f and the reverse clutch component C2r share a fundamentally similar structure to the first clutch mechanism C1. The forward clutch component C2f includes a forward piston C2fp that presses against friction plates, while the reverse clutch component C2r includes a reverse piston C2rp that presses against friction plates.

[0136] With this structure, the supply of hydraulic oil to the forward piston C2fp establishes a transmission state in which the driving force of the second output shaft 46b is transmitted to the second forward output gear 37a, and the discharge of hydraulic oil establishes a cutoff state in which the driving force is not transmitted. Furthermore, the supply of hydraulic oil to the reverse piston C2rp establishes a transmission state in which the driving force of the second output shaft 46b is transmitted to the second reverse output gear 38a, and the discharge of hydraulic oil establishes a cutoff state in which the driving force is not transmitted.

[0137] The first clutch mechanism C1 and the second clutch mechanism C2 are configured to allow the lubricating oil stored in the transmission 12 to penetrate. Due to this structure, when the first clutch mechanism C1 is in the disengaged state, even if the driving-side friction plates 81 and the driven-side friction plates 82 are spaced apart, they rotate due to the viscosity of the lubricating oil, and the drag torque is transmitted to the front wheels 1 and the rear wheels 2 via the first forward output gear 36a.

[0138] When the forward clutch component C2f and the reverse clutch component C2r of the second clutch mechanism C2 are in the disengaged state, similarly to the first clutch mechanism C1, the internal friction plates rotate due to the viscosity of the lubricating oil, and the drag torque is transmitted to the front wheel 1 and the rear wheel 2.

[0139] In this other embodiment (b), the intermediate rotating component 85 is a tubular component that is relatively freely rotatable and externally embedded in the first output shaft 46a. Relative to the intermediate rotating component 85, a gear portion 85G is integrally formed on the outer peripheral side of the intermediate rotating component 85 as a connecting portion, and the gear portion 85G is engaged with the second reverse input gear 38b.

[0140] like Figure 8As shown, the intermediate rotating member 85 is arranged inside the first clutch housing CH1 on the side opposite to the first sleeve 36s along the axis of the first output shaft 46a. The first clutch housing CH1 has a plurality of second slits 80b formed on the side opposite to the first slits 80a along the axis of the first output shaft 46a.

[0141] Furthermore, the first clutch housing CH1 includes a plurality of plate-shaped friction plates 86 (an example of a friction member) that fit into the second slit 80b of the first clutch housing CH1, and a plurality of plate-shaped friction rings 87 (an example of a friction plate) that are externally fitted to the outer periphery of the intermediate rotating member 85 in a torque-transmitting manner. The plurality of friction plates 86 and the plurality of friction rings 87 have a similar structure to that of the first clutch mechanism C1, but differ from the first clutch mechanism C1 in that the plurality of friction plates 86 and the plurality of friction rings 87 are not provided with a piston for contacting the plurality of friction plates 86 and the plurality of friction rings 87.

[0142] As previously mentioned, the first clutch housing CH1 rotates integrally with the first output shaft 46a. Therefore, when the first clutch mechanism C1 is disengaged, the first clutch housing CH1 also rotates. This rotation also causes the friction plate 86 to rotate, and the friction ring 87 adjacent to it to rotate due to the drag torque. As a result, rotational force is transmitted to the intermediate rotating member 85, which is then transmitted via the second reverse input gear 38b to the first pair of shafts 51. The drag torque thus transmitted from the intermediate rotating member 85 to the first pair of shafts 51 acts in the direction of moving the vehicle body A backward.

[0143] [Function and Effect] of Another Embodiment (b)

[0144] Figures 6 to 9 In the structure of the transmission 12 shown, when the first clutch mechanism C1 is in a disengaged state and the forward clutch portion C2f and the reverse clutch portion C2r of the second clutch mechanism C2 are in a disengaged state, the drag torque acts from the first clutch mechanism C1 and the forward clutch portion C2f relative to the front wheels 1 and the rear wheels 2 in the forward direction, and the drag torque acts from the reverse clutch portion C2r to the front wheels 1 and the rear wheels 2 in the reverse direction.

[0145] In this way, the drag torque acts in the forward direction from both clutches and in the reverse direction from one clutch. The drag torque in the forward direction is larger than the drag torque in the reverse direction, resulting in the disadvantageous situation that the vehicle body moves forward at a low speed.

[0146] In contrast, Figure 8 、 Figure 9As shown, the gear portion 85G of the intermediate rotating member 85 meshes with the second reverse input gear 38b, allowing the rotational force of the intermediate rotating member 85 to act in the reverse direction. This increases the drag torque in the reverse direction, offsetting the forward and reverse drag torques, thereby eliminating the problem of the vehicle body A moving at low speed. In particular, this structure does not include an actuator to suppress the problem of the vehicle body A moving at low speed due to the drag torque, thereby avoiding structural complexity and an increase in the number of parts.

[0147] (c) A timing belt or a plurality of gears is used as a connection portion for transmitting the rotational force of the intermediate rotating member 85 to the second reverse input gear 38b (output portion) of the second clutch mechanism C2.

[0148] As a modified example of this alternative embodiment (c), the second reverse output gear 38a of the second clutch mechanism C2 may be used as the output portion. A gear portion 85G formed on the outer periphery of the intermediate rotating member 85 and an idler gear meshing with the gear portion 85G may constitute a connection portion so as to transmit the rotational force of the intermediate rotating member 85 to the second reverse output gear 38a. In this configuration, the idler gear meshes with the second reverse output gear 38a, thereby transmitting the rotational force in the opposite direction of the rotation of the intermediate rotating member 85 to the second reverse output gear 38a.

[0149] (d) As a structure for applying a drag torque associated with the rotation of the first output shaft 46a (first shaft) to the intermediate rotating member 85, a structure in which the intermediate rotating member 85 is simply loosely fitted with the first output shaft 46a or a coupling in which the drag torque of the first output shaft 46a is applied by utilizing a fluid may be used. Furthermore, the intermediate rotating member 85 and the connecting portion (such as the gear portion 85G) may be supported by separate shafts.

[0150] Another embodiment (d) includes the concept that the intermediate rotating member 85 and the connecting portion (such as the gear portion 85G) are not necessarily arranged coaxially with the first output shaft 46a (first shaft). Therefore, for example, a configuration is conceivable in which the gear portion 85, serving as the connecting portion, is supported on a shaft at a position different from the first output shaft 46a, and the drag torque from the intermediate rotating member 85 is transmitted to the gear portion 85 via a timing belt, an endless chain, a gear (including multiple gears), or the like.

[0151] As a similar structure, it is also considered to be configured such that a shaft body that rotates with the help of the driving force of the first output shaft 46a is provided at a position different from the first output shaft 46a, and the intermediate rotating component 85 is embedded in the shaft body to transmit the drag torque accompanying the rotation of the shaft body to the intermediate rotating component 85, and then transmit it from the intermediate rotating component 85 to the gear part 85.

[0152] (e) The continuously variable transmission case 11 of the continuously variable transmission 20 and the main clutch case 10 may be integrally formed, and the continuously variable transmission 20 and the transmission case 12 may be integrally formed. This configuration can improve strength and reduce the weight of the entire transmission system compared to a configuration in which these are manufactured separately and connected with bolts or the like.

[0153] (f) Three or more planetary gear transmission mechanisms are used to configure the travel speed change device 50. By using three or more planetary gear transmission mechanisms in this manner, multi-stage speed change can be easily performed.

[0154] (g) The input shaft 21 and the output shaft 22 of the continuously variable transmission 20 may be configured to protrude forward.

[0155] Industrial applicability

[0156] The present invention can be used in a work vehicle that changes the driving force of an engine via a hydrostatic continuously variable transmission and a planetary gear transmission.

[0157] Furthermore, the present invention can be utilized in a work vehicle that performs speed change by controlling two wet clutches.

[0158] Description of Reference Numerals

[0159] 1 front wheel (travel mechanism)

[0160] 2 rear wheels (travel mechanism)

[0161] 4 engines

[0162] 12 gearbox

[0163] 20 continuously variable transmission

[0164] 21 Input shaft

[0165] 22 output shaft

[0166] 23-port block

[0167] 31 Main drive shaft (drive shaft)

[0168] 32 drive gear mechanism

[0169] 33 branch gear mechanism

[0170] 38a 2nd reverse output gear (reverse output gear)

[0171] 38b: Second reverse input gear, reverse transmission gear (output part)

[0172] 46a 1st output shaft (1st shaft)

[0173] 46b 2nd output shaft (2nd shaft)

[0174] 50 Travel speed change device (travel speed change unit)

[0175] 50B auxiliary transmission device

[0176] 85 intermediate rotating parts

[0177] 85G Gear Department, Contact Department

[0178] 86 friction plates, friction parts

[0179] 87 friction ring, friction plate

[0180] A moving vehicle body (vehicle body)

[0181] C1 No. 1 clutch mechanism (clutch mechanism)

[0182] C2 2nd clutch mechanism (clutch mechanism)

[0183] C2f forward clutch unit

[0184] C2r reverse clutch

[0185] CH1 No. 1 clutch housing (clutch housing)

[0186] Q1 1st planetary gear transmission (planetary gear transmission)

[0187] Q2 2nd planetary gear transmission (planetary gear transmission mechanism)

[0188] Hydraulic Pump

[0189] M hydraulic motor.

Claims

1. A work vehicle, characterized in that: A hydrostatic continuously variable transmission for steplessly changing the speed of the engine driving force, a plurality of planetary gear transmissions for changing the speed of the driving force changed by the continuously variable transmission, and a plurality of clutch mechanisms corresponding to the plurality of planetary gear transmissions for respectively extracting the driving force from the plurality of planetary gear transmissions. A travel speed change unit is provided for changing the speed of the driving force transmitted from the plurality of clutch mechanisms and transmitting the same to the travel mechanism. The plurality of planetary gear transmissions are arranged in parallel in the left-right direction, and the plurality of planetary gear transmissions, the plurality of clutch mechanisms, and the travel speed change portion are housed in a transmission case. The engine, the continuously variable transmission, and the plurality of planetary gear transmissions are arranged in this order along the front-rear direction of the vehicle body. The continuously variable transmission comprises a variable displacement hydraulic pump driven by the engine and a hydraulic motor rotated by hydraulic oil supplied from the hydraulic pump, wherein an input shaft of the hydraulic pump and an output shaft of the hydraulic motor are formed to protrude in a direction in which the planetary gear transmission is arranged. The drive shaft for transmitting the driving force of the engine is arranged to pass through the continuously variable transmission in the front-to-rear direction, and includes a drive gear mechanism and a branch gear mechanism. The drive gear mechanism transmits the driving force from the portion of the drive shaft that passes through the continuously variable transmission to the input shaft, and the branch gear mechanism transmits the driving force from the output shaft to the plurality of planetary gear transmissions. A main clutch mechanism capable of transmitting and cutting off the driving force of the engine is provided between the engine and the continuously variable transmission in the front-rear direction of the vehicle body.

2. The work vehicle according to claim 1, wherein: The plurality of planetary gear transmissions include a first planetary gear transmission with a low speed and a high-speed side, and a second planetary gear transmission with a high speed and a low-speed side. The plurality of clutch mechanisms include a first clutch mechanism for intermittently transmitting the driving force from the first planetary gear transmission and a second clutch mechanism for intermittently transmitting the driving force from the second planetary gear transmission. The travel speed change portion includes a sub-speed change device for changing the speed of the driving force from the first clutch mechanism and the second clutch mechanism.

3. The work vehicle according to claim 1 or 2, characterized in that: The continuously variable transmission includes a variable displacement hydraulic pump driven by the engine, a hydraulic motor rotated by hydraulic oil supplied from the hydraulic pump, and a port block forming a hydraulic circuit, wherein the hydraulic circuit is formed between the hydraulic pump and the hydraulic motor. The hydraulic pump and the hydraulic motor are arranged on the rear surface side of the port block.

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