Transmission for working vehicle and working vehicle equipped with the same

Abstract

The present invention relates to a transmission for a work vehicle and a work vehicle equipped with the same. The transmission for a work vehicle comprises a first speed change mechanism for changing the speed of input power into one of a plurality of stages, and a second speed change mechanism for changing the speed of the power after the speed change obtained by the first speed change mechanism into one of a plurality of stages less in number than the first speed change mechanism. The plurality of speed change multi-plate clutches of the first speed change mechanism and the plurality of speed reduction multi-plate clutches of the second speed change mechanism are arranged in parallel in a manner adjacent to each other in the radial direction.

Description

[0001] This application is a divisional application of the Chinese invention patent application with application number 201810635161.6, application date June 20, 2018, and invention name “Transmission for work vehicle and work vehicle equipped with the same”. Technical Field

[0002] The present invention relates to a transmission for a working vehicle and a working vehicle equipped with the same. The working vehicle is typically a tractor, but is not limited thereto. Background Art

[0003] (1) First related technology

[0004] The transmission for a working vehicle disclosed in JP2001-105912A comprises a plurality of transmission shafts extending parallel to each other in the front-rear direction of the vehicle body and a multi-stage transmission device, wherein the transmission device comprises a multi-stage transmission device having a first transmission mechanism for shifting the input power in multiple stages, and a second transmission mechanism for shifting the power shifted by the first transmission mechanism in a number of stages less than that of the first transmission mechanism.

[0005] The transmission has a structure that includes a main transmission device capable of shifting to 1 to 4 speeds by disconnecting / connecting operations of four multi-plate clutches (hydraulic clutches), and a sub-transmission device capable of shifting to high and low speeds by disconnecting / connecting operations of two multi-plate clutches (hydraulic clutches), thereby enabling 8-speed shifting as a whole. In addition, in the transmission for a working vehicle, the main transmission device and the sub-transmission device capable of shifting to 8 speeds as a whole are dispersedly arranged in the front and rear directions on the front and rear sides of the transmission case.

[0006] In this structure, since the main transmission and the auxiliary transmission are dispersedly arranged in the front-to-back direction, the operating systems for the main transmission and the auxiliary transmission capable of 8-speed shifting are also dispersedly constructed in the front-to-back direction. Therefore, the operating systems for the main transmission and the auxiliary transmission are complicated, and it takes time to construct the operating system.

[0007] Therefore, it is desired to be able to easily configure an operating system for a multi-speed transmission.

[0008] (2) Second related technology

[0009] The working vehicle transmission disclosed in JP8-2267A (or its corresponding US5599247) includes a transmission case also serving as an oil tank, a plurality of hydraulic devices arranged inside the transmission case, and a valve unit for controlling the flow of oil to the hydraulic devices.

[0010] The transmission has an opening on one side wall of the transmission case (front case), and a valve unit (control valve device) for controlling the operation of the auxiliary transmission device is fixedly supported on the transmission case in a state where it is inserted into the opening and spans the inside and outside of the transmission case.

[0011] In this structure, the strength of the transmission case is reduced by providing an opening on one side wall of the transmission case. In addition, when the valve unit has a solenoid valve, iron powder and the like contained in the oil stored in the transmission case are attracted toward the valve unit by the excitation of the solenoid valve, and may enter the interior of the valve unit and cause the solenoid valve to bite into the solenoid valve.

[0012] Therefore, it is desired to prevent the strength of the transmission case from being reduced while avoiding the possibility that iron powder and the like contained in the oil in the transmission case may adversely affect the valve unit. Summary of the invention

[0013] (1a) In response to the first related art, the following transmission for a working vehicle has been proposed.

[0014] A transmission for a working vehicle, comprising: a plurality of transmission shafts extending parallel to each other in the front-to-rear direction of a vehicle body, the transmission shafts comprising a speed change shaft and a reduction shaft; a multi-stage speed change device, the multi-stage speed change device comprising: a first speed change mechanism for changing the input power to one of a plurality of stages, the first speed change mechanism comprising a plurality of speed change gear sets and a plurality of speed change multi-plate clutches, the plurality of speed change multi-plate clutches being arranged adjacent to each other on the speed change shaft along the front-to-rear direction, and disconnecting / connecting the transmission relative to the plurality of the speed change gear sets; a second speed change mechanism for changing the power after the speed change obtained by the first speed change mechanism to one of a plurality of stages less in number than the first speed change mechanism, the second speed change mechanism comprising a plurality of reduction gear sets and a plurality of reduction multi-plate clutches, the plurality of reduction multi-plate clutches being arranged on the reduction shaft, and disconnecting / connecting the transmission relative to the plurality of reduction gear sets; wherein the plurality of speed change multi-plate clutches and the plurality of reduction multi-plate clutches are arranged in parallel in a manner adjacent to each other in the radial direction thereof.

[0015] According to this scheme, a plurality of multi-plate clutches for shifting speed and a plurality of multi-plate clutches for reducing speed are arranged in a concentrated state so as to be adjacent to each other in the radial or front-to-rear direction, so the respective operating systems for each multi-plate clutch for shifting speed and each multi-plate clutch for reducing speed can also be easily constructed in a concentrated state.

[0016] In addition, since the number of speed stages of the second speed change mechanism is less than that of the first speed change mechanism, the number of multi-plate clutches for speed reduction of the second speed change mechanism is less than that of the multi-plate clutches for speed reduction of the first speed change mechanism. Moreover, in each multi-plate clutch for speed reduction, the power with a larger torque after deceleration brought by the reduction gear set is disconnected / connected, so the load condition becomes severe compared with each multi-plate clutch for speed reduction that disconnects / connects the power with a smaller torque before deceleration. Therefore, in each multi-plate clutch for speed reduction, the number of clutch plates equipped becomes more than that of each multi-plate clutch for speed reduction, and the length thereof in the axial direction (front-rear direction) becomes longer.

[0017] Taking this into consideration, in the transmission device, a plurality of multi-plate clutches for speed change, which are large in number but short in length in the axial direction, are arranged adjacent to each other along the front-rear direction on the shaft of the speed change shaft. In addition, a plurality of multi-plate clutches for speed reduction, which are small in number but long in length in the axial direction, are arranged adjacent to each other along the front-rear direction on the shaft of the speed reduction shaft.

[0018] As a result, the length of the transmission in the axial direction (front-to-back direction) can be shortened compared to a situation in which, for example, a plurality of multi-plate clutches for speed change having a shorter axial length are dispersed on the shaft of the speed change shaft and the shaft of the reduction shaft and are arranged adjacent to each other in the front-to-back direction on each shaft, and a plurality of multi-plate clutches for reduction having a longer axial length are arranged adjacent to each other in the front-to-back direction on the shaft of the reduction shaft together with some multi-plate clutches for speed change.

[0019] As a result, the front-to-rear length of the transmission for a working vehicle equipped with the transmission can be shortened, and an operating system for each multi-plate clutch of the transmission can be easily configured.

[0020] In a preferred embodiment, the transmission shaft includes an intermediate shaft disposed between the speed change shaft and the reduction shaft.

[0021] According to this scheme, the plurality of speed change gear sets that transmit from the speed change shaft to the intermediate shaft can be respectively composed of the first speed change gear arranged on the shaft of the speed change shaft and the second speed change gear arranged on the shaft of the intermediate shaft. In addition, the plurality of reduction gear sets that transmit from the intermediate shaft to the reduction shaft can be respectively composed of the first reduction gear arranged on the shaft of the intermediate shaft and the second reduction gear arranged on the shaft of the reduction shaft. That is, the plurality of speed change gear sets and the plurality of reduction gear sets can be respectively composed of the minimum number of gears (two pieces). As a result, the compactness and simplification of the structure of the speed change device due to the reduction in the number of parts can be achieved.

[0022] In a preferred embodiment, the speed change shaft, the reduction shaft, and the intermediate shaft are arranged to form an isosceles triangle with the intermediate shaft as an upper vertex when viewed from the front of the vehicle body.

[0023] According to this scheme, in the transmission, the speed change shaft and the reduction shaft are arranged in a left-right arrangement at the lower part of the speed change shaft, and the speed change shaft and the reduction shaft are made heavier by arranging a plurality of multi-plate clutches for speed change or a plurality of multi-plate clutches for reduction on the shaft. In addition, the intermediate shaft is arranged in the middle of the speed change shaft and the reduction shaft and at a position above the speed change shaft and the reduction shaft, and the intermediate shaft is made lighter by not arranging a multi-plate clutch for speed change or a multi-plate clutch for reduction on the shaft. That is, the speed change device can be equipped in a transmission for a working vehicle in a state where the center of gravity is low and the left-right balance is improved, thereby achieving a low center of gravity and an improvement in the left-right balance of the transmission for a working vehicle, so that the stability of the transmission for a working vehicle can be improved.

[0024] In a preferred embodiment, the radial sizes of the plurality of speed-changing multi-plate clutches and the plurality of speed-reduction multi-plate clutches are set to be the same size.

[0025] According to this scheme, the clutch plates (driving plates and driven plates), pressure plates, pistons, etc. used in multiple speed-changing multi-plate clutches and multiple speed-reduction multi-plate clutches can be made into common parts whose radial sizes are common to all multi-plate clutches. As a result, it is possible to achieve easier parts management, etc.

[0026] Furthermore, for example, when the disconnection / connection operation of a plurality of speed-changing multi-plate clutches and a plurality of speed-reducing multi-plate clutches is controlled by electronic hydraulic control, pistons and the like are common parts, and thus, by setting the initial pressures with respect to each speed-changing multi-plate clutch and each speed-reducing multi-plate clutch to be the same, the timing of clutch engagement of each multi-plate clutch can be made the same. As a result, it is easy to create each control program required when the disconnection / connection operation of each speed-changing multi-plate clutch and each speed-reducing multi-plate clutch is appropriately controlled by electronic hydraulic control.

[0027] Furthermore, a work vehicle having a work vehicle transmission having any of the above aspects is also an object of the present invention. In such a work vehicle, the front-rear length of the work vehicle can be prevented from being increased in size, and the stability of the work vehicle can be improved.

[0028] (1b) Furthermore, corresponding to the first related art, a transmission for a working vehicle described below has been proposed.

[0029] A transmission for a working vehicle comprises: a plurality of transmission shafts extending in parallel with each other in the front-rear direction of a vehicle body, the transmission shafts comprising a speed change shaft and a reduction shaft; a multi-stage transmission device, the multi-stage transmission device comprising: a first speed change mechanism for changing the input power to one of a plurality of stages, the first speed change mechanism having a plurality of speed change gear sets and a plurality of multi-plate clutches for speed change, the plurality of multi-plate clutches for speed change being arranged adjacent to each other on the speed change shaft along the front-rear direction, and disconnecting / connecting the transmission relative to the plurality of speed change gear sets; and a second speed change mechanism for changing the speed of the power after speed change obtained by the first speed change mechanism to one of a plurality of stages less in number than the first speed change mechanism. Mechanism, the aforementioned second speed change mechanism has a plurality of reduction gear groups and a plurality of multi-plate clutches for reduction, the plurality of multi-plate clutches for reduction are arranged on the aforementioned reduction shaft, and disconnect / connect the transmission relative to the plurality of aforementioned reduction gear groups; wherein the aforementioned transmission shaft also includes an intermediate shaft, the intermediate shaft is arranged between the aforementioned speed change shaft and the aforementioned reduction shaft, and the aforementioned speed change multi-plate clutch and the aforementioned multi-plate clutch for reduction are not arranged on the shaft; when observed from the front of the vehicle body, in a case where a pair of triangular imaginary spaces are formed above and below an imaginary line connecting the axis center of the aforementioned speed change shaft with the axis center of the aforementioned reduction shaft, the aforementioned intermediate shaft enters the imaginary space on one side.

[0030] According to this scheme, a plurality of multi-plate clutches for shifting speed and a plurality of multi-plate clutches for reducing speed are arranged on the shaft of the speed change shaft and the shaft of the reduction shaft in a concentrated state adjacent to each other in the front-to-rear direction, so the respective operating systems for each multi-plate clutch for shifting speed and each multi-plate clutch for reducing speed can also be easily constructed in a concentrated state.

[0031] In addition, the second transmission mechanism has a smaller number of speed stages than the first transmission mechanism, so the second transmission mechanism has a smaller number of speed reduction multi-plate clutches than the first transmission mechanism. In addition, since the power with a larger torque after deceleration obtained by the reduction gear set is disconnected / connected in each speed reduction multi-plate clutch, the load condition becomes severe compared with each speed reduction multi-plate clutch that disconnects / connects the power with a smaller torque before deceleration. Therefore, in each speed reduction multi-plate clutch, the number of clutch plates equipped becomes larger than that of each speed reduction multi-plate clutch, and its length in the axial direction (front-rear direction) becomes longer.

[0032] Taking this into consideration, in the transmission device, a plurality of multi-plate clutches for speed change, which are large in number but short in length in the axial direction, are arranged adjacent to each other along the front-rear direction on the shaft of the speed change shaft. In addition, a plurality of multi-plate clutches for speed reduction, which are small in number but long in length in the axial direction, are arranged adjacent to each other along the front-rear direction on the shaft of the speed reduction shaft.

[0033] As a result, the length of the transmission in the axial direction (front-to-back direction) can be shortened compared to a situation in which, for example, a plurality of multi-plate clutches for speed change having a shorter axial length are dispersed on the shaft of the speed change shaft and the shaft of the reduction shaft and are arranged adjacent to each other in the front-to-back direction on each shaft, and a plurality of multi-plate clutches for reduction having a longer axial length are arranged adjacent to each other in the front-to-back direction on the shaft of the reduction shaft together with some multi-plate clutches for speed change.

[0034] In addition, a pair of roughly triangular spaces formed between the speed-changing multi-plate clutch and the speed-reducing multi-plate clutch are effectively utilized, and the intermediate shaft is inserted into the space on one side, so that the length of the speed-changing device in a direction (up and down direction or left and right direction) orthogonal to the axial direction (front and rear direction) can be shortened.

[0035] As a result, the front-rear length and the up-down length or the left-right length of the transmission for a working vehicle equipped with the transmission can be shortened, and the operating system for each multi-plate clutch of the transmission can be easily configured.

[0036] In a preferred embodiment, the plurality of the aforementioned multi-plate clutches for shifting speed and the plurality of the aforementioned multi-plate clutches for reducing speed are arranged adjacent to each other in the left-right direction of the vehicle body; when viewed from the front of the vehicle body, the pair of imaginary spaces are formed above and below between the aforementioned multi-plate clutches for shifting speed and the aforementioned multi-plate clutches for reducing speed.

[0037] According to this scheme, a pair of upper and lower spaces of a substantially triangular shape formed between the speed-changing multi-plate clutch and the speed-reduction multi-plate clutch are effectively utilized, and the intermediate shaft is inserted into one of the spaces, so that the length of the speed change device in the vertical direction can be shortened.

[0038] As a result, the front-rear length and the top-bottom length of the transmission for a working vehicle equipped with the transmission can be shortened, and the operating system for each multi-plate clutch of the transmission can be easily configured.

[0039] In a preferred embodiment, the transmission for a work vehicle also includes a drive switching device, which has a multi-plate clutch and is configured to switch the transmission state relative to the left and right front wheels by means of the disconnection / connection operation of the multi-plate clutch; wherein the drive switching device is arranged below the transmission device when viewed from the front of the vehicle body and the upper part of the multi-plate clutch enters into the imaginary space on the lower side.

[0040] According to this scheme, the drive switching device can be arranged below the transmission device, and the vertical length of the transmission for the working vehicle can be shortened. In addition, compared with the case where the drive switching device is arranged above the transmission device, the center of gravity of the transmission for the working vehicle can be lowered.

[0041] In a preferred embodiment, the radial sizes of the plurality of speed-changing multi-plate clutches and the plurality of speed-reduction multi-plate clutches are set to be the same.

[0042] According to this scheme, the clutch plates (driving plates and driven plates), pressure plates, pistons, etc. used in multiple speed-changing multi-plate clutches and multiple speed-reduction multi-plate clutches can be made into common parts whose radial sizes are common to all multi-plate clutches. As a result, it is possible to achieve easier parts management, etc.

[0043] Furthermore, for example, when the disconnection / connection operation of a plurality of speed-changing multi-plate clutches and a plurality of speed-reducing multi-plate clutches is controlled by electronic hydraulic control, pistons and the like are common parts, and thus, by setting the initial pressures with respect to each speed-changing multi-plate clutch and each speed-reducing multi-plate clutch to be the same, the timing of clutch engagement of each multi-plate clutch can be made the same. As a result, it is easy to create each control program required when the disconnection / connection operation of each speed-changing multi-plate clutch and each speed-reducing multi-plate clutch is appropriately controlled by electronic hydraulic control.

[0044] Furthermore, a work vehicle having a work vehicle transmission having any of the above aspects is also an object of the present invention. In such a work vehicle, the front-rear length of the work vehicle can be prevented from being increased in size, and the stability of the work vehicle can be improved.

[0045] (2) In response to the second related art, the following transmission for a working vehicle has been proposed.

[0046] A transmission for a work vehicle, comprising: a transmission case, which also serves as an oil tank; a plurality of hydraulic devices, which are arranged inside the transmission case; and a valve unit, which controls the flow of oil relative to the hydraulic devices; wherein the transmission case has a valve unit mounting portion, and the valve unit mounting portion is used to mount the valve unit from the outside of the transmission case; the valve unit has a base plate mounted on the valve unit mounting portion, and a valve body having a plurality of solenoid valves; on the valve unit mounting portion, a recess is formed to form a storage chamber for the valve body, which is divided between the base plate and the valve unit mounting portion.

[0047] According to this solution, when the valve unit is mounted on the valve unit mounting portion, the valve body is accommodated in the accommodation chamber formed by partitioning the outer side of the transmission case. This can prevent iron powder and the like contained in the oil in the transmission case from being attracted toward the valve unit due to the excitation of the solenoid valve. As a result, it can avoid the possibility that the iron powder and the like contained in the oil in the transmission case enter the interior of the valve unit and bite into the solenoid valve due to the attraction.

[0048] In addition, there is no need to form an opening on the valve unit mounting portion for allowing the valve body to enter the internal space of the transmission case, as in the case where the valve body is arranged in the internal space of the transmission case, so a decrease in the strength of the transmission case caused by forming the opening can be prevented.

[0049] In a preferred embodiment, a return oil passage for returning excess oil from the valve body to the interior of the transmission case is formed on the valve unit mounting portion at a position in the recessed portion that is closer to the upper side of the vehicle body than the valve body.

[0050] According to this scheme, the oil leaking from the solenoid valve of the valve body can be stored as lubricating oil in a position on the upper side of the vehicle body in the storage chamber. Furthermore, in a case where the oil level of the lubricating oil reaches the return oil path forming portion of the storage chamber, the lubricating oil that has reached the return oil path forming portion can be sent back from the return oil path into the transmission case as residual oil. In addition, it is possible to prevent the occurrence of an undesirable situation in which the oil in the transmission case and the iron powder contained in the oil flow from the return oil path into the storage chamber due to a large tilt of the working vehicle equipped with the transmission. As a result, it is possible to return the residual oil in the storage chamber to the transmission case while preventing the iron powder contained in the oil in the transmission case from biting into the solenoid valve.

[0051] In a preferred embodiment, the return oil passage is formed in two layers, upper and lower, in the valve unit mounting portion.

[0052] According to this scheme, compared with the case where the return oil passage is not divided into two layers and is formed to have the same opening area, it is less likely to cause the oil in the transmission case and the iron powder contained in the oil to flow into the storage chamber from the return oil passage. As a result, it is possible to return the remaining oil in the storage chamber to the transmission case while more reliably preventing the iron powder contained in the oil in the transmission case from being bitten into the solenoid valve.

[0053] In a preferred embodiment, the oil return passage is formed so that an opening area of ​​an upper oil return passage is smaller than an opening area of ​​a lower oil return passage.

[0054] According to this scheme, when the amount of oil leaking from each solenoid valve is small, the remaining oil in the storage chamber can be quickly sent back to the transmission case from the return oil passage of the lower layer with a larger opening area, and when the amount of oil leaking from each solenoid valve is large, the remaining oil in the storage chamber can be quickly sent back to the transmission case from the return oil passages of the upper and lower layers. In addition, by reducing the opening area of ​​the return oil passage of the upper layer that is auxiliary used when the amount of oil leaking from each solenoid valve is large, it is possible to prevent the strength of the transmission case from being reduced due to unnecessary expansion of its opening area.

[0055] In a preferred embodiment, the aforementioned recess has a lower recessed portion for accommodating the aforementioned valve body, and an upper recessed portion connected to the interior of the aforementioned transmission housing via the aforementioned return oil passage; the aforementioned upper recessed portion is formed to be narrower than the aforementioned lower recessed portion with a recessed depth shallower than that of the aforementioned lower recessed portion.

[0056] According to this scheme, the internal space of the transmission case can be made larger than, for example, a case where the upper recessed portion that does not accommodate the valve body has the same recessed depth and the same width as the lower recessed portion. As a result, it is easy to configure and assemble the transmission system and the like that are arranged in the internal space of the transmission case. Furthermore, by making the recessed depth of the lower recessed portion deeper than the recessed depth of the upper recessed portion, the valve body can be accommodated in the accommodation chamber, for example, in a case where the thickness of the valve body increases due to a larger solenoid valve, or in a case where the valve body is configured as a two-layer overlapping structure due to an increase in the number of solenoid valves installed.

[0057] In a preferred embodiment, an oil filter is provided in the return oil passage.

[0058] According to this scheme, even if the oil accumulated in the transmission case flows from the return oil passage into the storage chamber, it is possible to prevent iron powder and the like contained in the oil from flowing into the storage chamber. Furthermore, when the return oil passage is divided into two layers, as described above, and when the oil filter provided in the return oil passage of the lower layer is clogged, the remaining oil in the storage chamber can be sent back to the interior of the transmission case from the return oil passage of the upper layer.

[0059] In a preferred embodiment, the solenoid valve comprises a plurality of solenoid switch valves and a plurality of solenoid proportional valves; the valve body comprises a first valve body having a plurality of the solenoid switch valves and a second valve body having a plurality of the solenoid proportional valves; the first valve body is assembled onto a accommodating chamber forming surface on the bottom plate, and the accommodating chamber forming surface forms the accommodating chamber between the bottom plate and the recess; the second valve body is assembled onto the outer surface of the bottom plate on the opposite side of the accommodating chamber forming surface.

[0060] According to this scheme, the oil leaking from the electromagnetic switch valve with a high possibility of oil leakage can be accumulated in the storage chamber as lubricating oil, and the oil can be prevented from leaking to the outside. In addition, compared with the case where all electromagnetic valves including the electromagnetic proportional valve with a low possibility of oil leakage are accommodated in the storage chamber, the recess for the storage chamber formed in the transmission case can be narrowed, and the internal space of the transmission case can be enlarged. As a result, it becomes easy to configure and assemble the transmission system and the like arranged in the internal space of the transmission case.

[0061] In a preferred embodiment, a partition wall is integrally formed on the aforementioned transmission housing for supporting multiple transmission shafts equipped therein; the multiple aforementioned hydraulic equipment includes multiple transmission switching devices arranged on the multiple aforementioned transmission shafts; the aforementioned valve unit mounting portion is formed on the aforementioned transmission housing at a predetermined position in the front-rear direction of the vehicle body where the aforementioned partition wall is formed; and in the aforementioned partition wall, multiple internal oil circuits are formed, and the multiple internal oil circuits span multiple connection ports formed on the aforementioned valve unit and multiple oil circuits formed in the multiple aforementioned transmission shafts.

[0062] According to this scheme, in terms of forming each hydraulic path across the valve unit and each transmission switching device, it is not necessary to assemble a hydraulic pipe inside the transmission case. In addition, each internal hydraulic path of the partition wall that spans each connection port of the valve unit and each hydraulic path of multiple transmission shafts can be formed as short as possible in a simple straight line shape. As a result, the number of operating steps required to form each hydraulic path relative to each transmission switching device can be reduced. In addition, by forming each internal hydraulic path of the partition wall as short as possible in a simple straight line shape, each hydraulic path across the valve unit and each transmission switching device can be formed as short as possible in a simple shape. As a result, the responsiveness of each transmission switching device can be improved.

[0063] In addition, a work vehicle having a work vehicle transmission with any of the above schemes is also the object of the present invention. In such a work vehicle, failure of the solenoid valve caused by iron powder contained in the oil in the transmission case is less likely to occur, and a decrease in the strength of the transmission case can be prevented.

[0064] (3) The solutions proposed in (1a), (1b) and (2) above may be implemented independently or in combination as appropriate unless there is any contradiction.

[0065] Other features and advantages achieved thereby will become apparent from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a left side view of the tractor;

[0067] Figure 2 It is a schematic diagram showing a transmission for a working vehicle of a tractor's transmission system, etc.;

[0068] Figure 3 is a cross-sectional top view of a transmission for a working vehicle showing a transmission system of a tractor;

[0069] Figure 4 is a cross-sectional plan view showing a main part of the structure of the first transmission mechanism in the main transmission device;

[0070] Figure 5is a cross-sectional plan view showing the main parts of the structures of the second speed change mechanism of the main speed change device and the creeper speed change device;

[0071] Figure 6 It is a longitudinal sectional left side view showing the main parts of the structure of the first speed change shaft side in the auxiliary transmission device;

[0072] Figure 7 It is a longitudinal sectional left side view showing the main part of the structure of the second speed change shaft side in the auxiliary transmission device;

[0073] Figure 8 is a longitudinal sectional front view of a transmission for a working vehicle showing the arrangement of a transmission shaft, etc.;

[0074] Fig. 9 is a longitudinal sectional front view of a transmission for a working vehicle showing the shape of a valve unit mounting portion and a storage chamber, etc.;

[0075] Fig.10 It is a perspective view of a valve unit mounting portion in a transmission for a work vehicle;

[0076] Fig.11 yes Fig. 9 Sectional view XII-XII of the valve unit (longitudinal section left side view of the valve unit mounting portion);

[0077] Fig.12 is a right side view of the valve unit;

[0078] Fig.13 A longitudinal sectional left side view of the main part showing a state where the transmission case is divided front and rear at the configuration position of the creeper gear shift device;

[0079] Fig.14 The creeper transmission device of another embodiment is shown in FIG. Figure 5 the corresponding graph; and

[0080] Fig.15 The creeper transmission device of another embodiment is shown in FIG. Fig.13 The corresponding figure. DETAILED DESCRIPTION

[0081] Hereinafter, as an example of the present specific embodiment, an embodiment in which the transmission for a working vehicle according to the present invention is applied to a tractor as an example of a working vehicle will be described with reference to the drawings.

[0082] In addition, Figure 1 , Fig.11 The direction indicated by the arrow of the reference numeral F in the figure is the front side of the tractor, and the direction indicated by the arrow of the reference numeral U is the upper side of the tractor.

[0083] [Overall structure of the tractor]

[0084] like Figure 1 As shown, the tractor illustrated in this embodiment comprises: a prime mover 1, which is arranged in the front half of the vehicle body; a riding-type driving part 2 and a transmission for a working vehicle (hereinafter referred to as a transmission) 3, which are arranged in the rear half of the vehicle body; a fuel tank 4, which is arranged adjacent to the left side of the transmission 3; left and right front wheels 5, which are arranged on the left and right of the prime mover 1 so as to be drivable and steerable; left and right rear wheels 6, which are arranged on the left and right of the transmission 3 so as to be drivable; and a connecting rod mechanism 7 for connecting the working device, which is installed on the rear end of the transmission 3 so as to be able to be raised and lowered and swung; etc.

[0085] The driving unit 1 includes a front frame 8 disposed on the front side of the vehicle body, an engine 9 supported by the rear side of the front frame 8, and a swing-opening and closing engine hood 10 covering the engine 9. The engine 9 has an output shaft 9A protruding rearward toward the transmission 3 (see FIG. Figure 2 ).

[0086] The driving unit 2 includes a cockpit 11 supported by the transmission 3 to prevent vibration, a steering wheel 12 for steering the front wheels arranged at the front side of the cockpit 11 , and a driver's seat 13 arranged at the rear side of the cockpit 11 .

[0087] [Transmission and transmission case]

[0088] like Figure 1 to Figure 3 As shown, the transmission 3 includes: a transmission case 14, which also serves as a rear frame and an oil tank of the vehicle body; an input shaft 15, to which power from the engine 9 is input; a first output shaft 16 for the front wheels, which outputs power for driving the front wheels; left and right second output shafts 17 for the rear wheels, which output power for driving the rear wheels; a PTO shaft 18, which outputs power for working; a travel transmission system 19, which transmits the power input to the input shaft 15 to the first output shaft 16 and the left and right second output shafts 17; and a working transmission system 20, which transmits the power input to the input shaft 15 to the PTO shaft 18, etc. The axial direction of the first output shaft 16 and the PTO shaft 18 is set to the front-rear direction of the vehicle body. The axial direction of the left and right second output shafts 172 is set to the left-right direction of the vehicle body.

[0089] The transmission case 14 includes: a first case 21 bolted to the rear end of the engine 9; a second case 22 bolted to the rear end of the first case 21; a third case 23 bolted to the rear end of the second case 22; a fourth case 24 bolted to the rear end of the third case 23; a fifth case 25 bolted to the lower end of the second case 22; and left and right sixth cases 26 bolted to the left and right side ends of the fourth case 24; etc. That is, the transmission case 14 is configured as a seven-division structure that can be divided into seven cases 21 to 26. The second case 22 includes a front cover 27 bolted to the inner flange 22A thereof, and a first support wall 28 bolted to the rear end of the second case 22. The second case 22 is integrally formed with a partition wall 22B that divides its internal space into a front space and a rear space. The third housing 23 has a second support wall 29 and the like connected to a connection portion 23A therein by bolts. A partition wall 23B is integrally formed at the rear end of the third housing 23 to separate the interior space of the third housing 23 from the interior space of the fourth housing 24. The fourth housing 24 has a rear cover 30 and the like connected to the rear end thereof by bolts.

[0090] [Driving transmission system]

[0091] like Figure 2 to Figure 9 As shown, the travel transmission system 19 includes: an electronic hydraulic control type forward / rearward switchover device (electro-hydraulic controllable forward / rearward switchover device) 31 (an example of a transmission switching device), which is configured to switch the power input to the input shaft 15 into the power for forward travel and the power for reverse travel; an electronic hydraulic control type main transmission device 32 (an example of a transmission device, an example of a transmission switching device), which changes the speed of the power for travel from the forward / rearward switchover device 31 in 8 stages; a creeper transmission device 33, which changes the speed of the power for travel from the main transmission device 32 in 2 stages; an auxiliary transmission device 34, which changes the speed of the power for travel from the creeper transmission device 33 in 3 stages; a distribution shaft 35, which changes the speed of the power for travel from the auxiliary transmission device 34 to Front and rear distribution; reduction gear set 36, which reduces the driving power distributed by the distribution shaft 35 to drive the front wheels; an electronic hydraulically controlled drive switching unit 37, which switches the transmission state from the reduction gear set 36 to the first output shaft 16; a rear wheel differential device 38, which distributes the driving power from the distribution shaft 35 to the left and right rear wheels 6 while allowing the differential of the left and right rear wheels 6; left and right planetary gear reduction devices 39, which reduce the driving power from the rear wheel differential device 38 to drive the rear wheels; and left and right side brakes 40, which brake the left and right differential shafts 38A of the rear wheel differential device 38; etc.

[0092] The rear wheel differential device 38 includes a hydraulic differential switching mechanism 38B that switches its operating state between a differential enabling state and a differential stopping state. The left and right planetary gear type reduction devices 39 transmit the decelerated power obtained therefrom to the left and right rear wheels 6 via the left and right second output shafts 17 .

[0093] like Figure 1 As shown, the power for front wheel driving from the first output shaft 16 is transmitted to the left and right front wheels 5 via the external transmission shaft 41 and the front wheel differential device (not shown), etc., the external transmission shaft 41 rotates integrally with the first output shaft 16, and the front wheel differential device distributes the power for front wheel driving from the external transmission shaft 41 to the left and right front wheels 5 while allowing the differential of the left and right front wheels 5. The front wheel differential device has a hydraulic differential switching mechanism that switches its operating state between a differential allowing state and a differential stopping state.

[0094] [Operation transmission system]

[0095] like Figure 2-3 , Figure 8 As shown, the working transmission system 20 includes an upstream relay shaft 42 and a downstream relay shaft 43 for transmitting working power, which are arranged on the same axis as the input shaft 15 so as to rotate integrally with the input shaft 15, and a working power switching device 44 (an example of a transmission switching device) for switching the transmission state from the downstream relay shaft 43 to the PTO shaft 18.

[0096] [Forward / reverse switching device]

[0097] like Figure 2-3 , Fig. 9 As shown, the forward / reverse switching device 31 includes: a forward multi-plate clutch 45 and a reverse multi-plate clutch 46, which are arranged on the shaft of the input shaft 15; a reverse rotation shaft 47, which is arranged below the input shaft 15 and parallel to the input shaft 15; a forward output gear 48, which outputs the power transmitted via the forward multi-plate clutch 45 as forward power; a reverse gear set 49, which transmits the power transmitted via the reverse multi-plate clutch 46 to the reverse rotation shaft 47; and a reverse output gear 50, which outputs the reverse rotation power of the reverse rotation shaft 47 as reverse power; etc. That is, in the forward / reverse switching device 31, a multi-plate clutch type transmission switching device is adopted, which switches the transmission state by disconnecting / connecting operations of the two multi-plate clutches 45 and 46 for the front wheels and for the reverse.

[0098] The forward-reverse switching device 31 is arranged in the front side space inside the second housing 22, with the front end side of the input shaft 15 and the front end of the reverse rotating shaft 47 being supported by the front cover 27, and the rear end of the input shaft 15 and the rear end of the reverse rotating shaft 47 being supported by the partition wall 22B of the second housing 22.

[0099] [Main transmission]

[0100] like Figure 2 to Figure 5 , Figure 8-Figure 9 As shown, the main transmission device 32 is configured as an 8-speed transmission type including a first transmission shaft 51 (an example of a speed change shaft) for input, a second transmission shaft 52 (an example of an intermediate shaft) for relay, a third transmission shaft 53 (an example of a reduction shaft) for output, a first speed change mechanism 54 for changing the speed of the power input to the first transmission shaft 51 in four steps, and a second speed change mechanism 55 for changing the speed of the power after the speed change obtained by the first speed change mechanism 54 in two steps. The first speed change mechanism 54 includes four speed change gear groups 56 to 59 for transmitting the power from the first transmission shaft 51 to the second transmission shaft 52 at different speed ratios, and four speed change multi-plate clutches 60 to 63 for disconnecting / connecting the transmission to the corresponding speed change gear groups 56 to 59. The second transmission mechanism 55 includes two groups of reduction gears 64 and 65 for transmitting power from the second transmission shaft 52 to the third transmission shaft 53 at different speed ratios, and two reduction multi-plate clutches 66 and 67 for disconnecting / connecting the power from the corresponding reduction gears 64 and 65. That is, in the main transmission device 32, a multi-plate clutch type transmission switching device is adopted, which switches the transmission state by disconnecting / connecting operations of the four speed-changing multi-plate clutches 60 to 63 and the two reduction multi-plate clutches 66 and 67.

[0101] The main transmission 32 is arranged in the rear space inside the second housing 22 with the front ends of the transmission shafts 51 to 53 supported by the partition wall 22B of the second housing 22 and the rear ends of the transmission shafts 51 to 53 supported by the first support wall 28 .

[0102] In the main transmission device 32, three transmission shafts 51 to 53 are arranged in parallel with their axial directions set to the front-rear direction of the vehicle body. The second transmission shaft 52 is a cylindrical shaft that is relatively rotatably externally fitted on the upstream side relay shaft 42 of the working transmission system 20. The third transmission shaft 53 is arranged adjacent to the first transmission shaft 68 for input of the auxiliary transmission device 34 on the same axis.

[0103] like Figure 2-3 , Figure 5As shown, the crawling speed device 33 is arranged between the third transmission shaft 53 of the main speed device 32 and the first transmission shaft 68 of the auxiliary speed device 34 in such a manner that the third transmission shaft 53 of the main speed device 32 is the upstream transmission shaft relative to the crawling speed device 33, and the first transmission shaft 68 of the auxiliary speed device 34 is the downstream transmission shaft relative to the crawling speed device 33.

[0104] [Crawler gear shift device]

[0105] The creeping transmission 33 has a speed reduction mechanism 69 that reduces the power of the third transmission shaft 53 of the main transmission 32, and a synchronous meshing type switching mechanism 70 that switches the transmission state from the third transmission shaft 53 of the main transmission 32 to the first speed shaft 68 of the auxiliary transmission 34 to a constant speed state in which the power from the third transmission shaft 53 is directly transmitted to the first speed shaft 68 and a reduced speed state in which the power is transmitted via the speed reduction mechanism 69, etc. That is, in the creeping transmission 33, a synchronous meshing type transmission switching device is adopted in which the transmission state is switched by the switching operation of the synchronous meshing type switching mechanism 70.

[0106] The speed reduction mechanism 69 is a creeper speed reduction mechanism that reduces the power from the third transmission shaft 53 of the main transmission 32 to an ultra-low speed via two speed reduction gear sets 71 and 72 having a large speed ratio.

[0107] [Sub-speed transmission]

[0108] like Figure 2-3 , Figure 6-7 As shown, the auxiliary transmission device 34 includes the aforementioned first speed shaft 68, the second speed shaft 73 arranged in parallel with the first speed shaft 68, three speed gear groups 74 to 76 for transmitting power from the first speed shaft 68 to the second speed shaft 73 at different speed ratios, a first synchronous meshing switching mechanism 77 for disconnecting / connecting the transmission from the first speed shaft 68 to the high-speed reduction gear group 72, a second synchronous meshing switching mechanism 78 for disconnecting / connecting the transmission from the medium-speed and low-speed speed gear groups 75 and 76 to the second speed shaft 73, and an output gear group 79 for outputting the power after the speed change transmitted to the second speed shaft 73 to the distribution shaft 35. That is, in the auxiliary transmission device 34, a synchronous meshing transmission switching device is adopted in which the transmission state is switched by the switching operation of the two synchronous meshing switching mechanisms 70.

[0109] The auxiliary transmission device 34 is arranged in the internal space of the third housing 23 by the front end portions of the first speed shaft 68 and the second speed shaft 73 being supported by the second support wall 29, and the rear end portions of the first speed shaft 68 and the second speed shaft 73 being supported by the partition wall 23B of the third housing 23.

[0110] [Drive switching unit]

[0111] like Figure 2 , Figure 8-Figure 9 As shown, the drive switching unit 37 has a front wheel transmission shaft 80 arranged directly above the first output shaft 16 and in parallel with the first output shaft 16, a first drive switching device 81 for front wheel driving, and a second drive switching device 82 for front wheel speed increase. The drive switching unit 37 is arranged across the rear side space inside the second housing 22 and the internal space of the fifth housing 25 by the front end portion of the front wheel transmission shaft 80 being supported by the partition wall 22B of the second housing 22, the rear end portion of the front wheel transmission shaft 80 being supported by the first supporting wall 28, and the first output shaft 16 being supported by the fifth housing 25.

[0112] The first drive switching device 81 includes a reduction gear group 83 that reduces the power for front wheel driving from the reduction gear group 36 to a constant speed drive, and a multi-plate clutch 84 for constant speed transmission that disconnects / connects the transmission to the reduction gear group 83. The reduction gear group 83 reduces the power for front wheel driving and transmits it from the front wheel transmission shaft 80 to the first output shaft 16 so that the left and right front wheels 5 are driven at the same circumferential speed as the left and right rear wheels 6. The multi-plate clutch 84 for constant speed transmission switches between a transmission state in which the left and right front wheels 5 are driven at the same circumferential speed as the left and right rear wheels 6, and a disconnection state in which the left and right front wheels 5 are driven by the propulsion force of the left and right rear wheels 6. That is, in the first drive switching device 81, a multi-plate clutch type transmission switching device is adopted in which the transmission state is switched by the disconnection / connection operation of the multi-plate clutch 84 for constant speed transmission.

[0113] The second drive switching device 82 includes a speed-increasing gear set 85 for increasing the power for driving the front wheels from the reduction gear set 36 to increase the power for driving the speed-increasing gear set 85, and a multi-plate clutch 86 for speed-increasing transmission for disconnecting / connecting the transmission to the speed-increasing gear set 85. The speed-increasing gear set 85 increases the power for driving the front wheels and transmits it from the front wheel transmission shaft 80 to the first output shaft 16, so that the left and right front wheels 5 are driven at a circumferential speed of about twice that of the left and right rear wheels 6. The multi-plate clutch 84 for speed-increasing transmission switches between a transmission state in which the left and right front wheels 5 are driven at a circumferential speed of about twice that of the left and right rear wheels 6, and a disconnection state in which the left and right front wheels 5 are driven by the propulsion force of the left and right rear wheels 6. That is, in the second drive switching device 82, a multi-plate clutch type transmission switching device is adopted, in which the transmission state is switched by the disconnection / connection operation of the multi-plate clutch 84 for speed-increasing transmission.

[0114] In the drive switching unit 37, the multi-plate clutch 84 for constant speed transmission and the multi-plate clutch 86 for speed-increasing transmission are arranged front to back and configured on the shaft of the front wheel drive shaft 80, with the multi-plate clutch 84 for constant speed transmission being supported by the front side of the front wheel drive shaft 80 and the multi-plate clutch 86 for speed-increasing transmission being supported by the rear side of the front wheel drive shaft 80.

[0115] [Working power switching device]

[0116] like Figure 2-3 As shown, the working power switching device 44 has a hydraulic PTO clutch 87 for disconnecting / connecting the working power from the downstream relay shaft 43, a first speed change mechanism 88 of a constant mesh type for changing the speed of the power transmitted via the PTO clutch 87 in two stages, and a second speed change mechanism 89 of a constant mesh type for changing the speed of the power after the speed change obtained by the first speed change mechanism 88 in two stages. In addition, a multi-plate clutch is used in the PTO clutch 87. That is, in the working power switching device 44, a multi-plate clutch type and a constant mesh type transmission switching device are used to switch the transmission state by disconnecting / connecting the multi-plate clutch (PTO clutch 87) for working and switching the two constant mesh type speed change mechanisms 88 and 89. The working power switching device 44 is supported by the rear cover 30 and the like and is arranged in the internal space of the fourth housing 24.

[0117] With the help of the above structure, the transmission 3 is constructed as a plurality of transmission switching devices of a multi-plate clutch type, and comprises: a forward-reverse switching device 31, having two multi-plate clutches 45 and 46 for the front wheels and the reverse wheels; a main transmission device 32, having four multi-plate clutches 60 to 63 for speed change and two multi-plate clutches 66 and 67 for speed reduction; a first drive switching device 81, having a multi-plate clutch 84 for constant speed transmission; a second drive switching device 82, having a multi-plate clutch 84 for speed increase transmission; and an operating power switching device 44, having a multi-plate clutch for operation (PTO clutch 87).

[0118] [Multi-plate clutch for main transmission]

[0119] like Figure 2 to Figure 5 , Figure 8As shown, in the main transmission 32, the four speed-changing multi-plate clutches 60 to 63 are arranged in the front-to-back direction on the shaft of the first transmission shaft 51 arranged on the upstream side of the transmission direction among the three transmission shafts 51 to 53 arranged in parallel. Thus, the first transmission shaft 51 functions as a speed-changing shaft supporting the four speed-changing multi-plate clutches 60 to 63. The two speed-reducing multi-plate clutches 66 and 67 are arranged in the front-to-back direction on the shaft of the third transmission shaft 53 arranged on the downstream side of the transmission direction among the three transmission shafts 51 to 53 arranged in parallel. Thus, the third transmission shaft 53 functions as a speed-reducing shaft supporting the two speed-reducing multi-plate clutches 66 and 67. In addition, in the main transmission 32, the four speed-changing multi-plate clutches 60 to 63 and the two speed-reducing multi-plate clutches 66 and 67 are arranged in parallel in a manner adjacent to each other in the radial direction.

[0120] That is, in the main transmission 32, the four speed-changing multi-plate clutches 60 to 63 and the two speed-reducing multi-plate clutches 66 and 67 are arranged at the same position in the front-rear direction of the vehicle body. Thus, compared with, for example, a case where the four speed-changing multi-plate clutches 60 to 63 and the two speed-reducing multi-plate clutches 66 and 67 are arranged at different positions in the front-rear direction of the vehicle body with a positional deviation, the front-rear length of the main transmission 32 can be shortened, and the front-rear length of the transmission 3 provided with the main transmission 32 can be shortened. As a result, it is possible to prevent the tractor from being enlarged due to the increase in the front-rear length of the transmission 3 and the increase in the total length of the tractor.

[0121] [Main transmission shaft]

[0122] like Figure 2 , Figure 8 As shown, in the main transmission 32 , the second transmission shaft 52 of the three transmission shafts 51 to 53 arranged in parallel is arranged as an intermediate shaft between the first transmission shaft 51 (speed change shaft) and the third transmission shaft 53 (reduction shaft).

[0123] Thus, the four speed change gear groups 56 to 59 transmitting from the first transmission shaft 51 to the second transmission shaft 52 can be respectively composed of the first speed change gears 56A to 59A arranged on the shaft of the first transmission shaft 51, and the second speed change gears 56B to 59B arranged on the shaft of the second transmission shaft 52. In addition, the two reduction gear groups 64 and 65 transmitting from the second transmission shaft 52 to the third transmission shaft 53 can be respectively composed of the first reduction gears 64A and 65A arranged on the shaft of the second transmission shaft 52, and the second reduction gears 64B and 65B arranged on the shaft of the third transmission shaft 53.

[0124] That is, the four speed change gear sets 56 to 59 and the two reduction gear sets 64 and 65 can be configured with the minimum number of gears (two). As a result, the main transmission 32 can be made more compact and simpler in structure due to the reduction in the number of parts.

[0125] Furthermore, in the main transmission 32, the second speed gear 56B of the second speed gear set 57 of the four speed gear sets 56 to 59 also serves as the first reduction gear 65A of the high speed reduction gear set 65 of the two reduction gear sets 64 and 65. Thus, the main transmission 32 can be made more compact and the structure can be simplified due to the reduction in the number of parts.

[0126] like Figure 8 As shown, in the main transmission 32 , three propeller shafts 51 to 53 arranged in parallel are arranged to form a substantially isosceles triangle with the second propeller shaft 52 (intermediate shaft) as the upper vertex when viewed in the front-rear direction of the vehicle body.

[0127] Thus, in the main transmission device 32, the first transmission shaft 51 and the third transmission shaft 53 are arranged side by side at the lower part of the main transmission device 32, and the first transmission shaft 51 and the third transmission shaft 53 are heavier by arranging four multi-plate clutches 60 to 63 for speed change or two multi-plate clutches 66 and 67 for speed reduction on the shaft. In addition, the second transmission shaft 52 is arranged between the first transmission shaft 51 and the third transmission shaft 53 and at a position above the first transmission shaft 51 and the third transmission shaft 53, and the second transmission shaft 52 is lighter by not arranging the multi-plate clutches 60 to 63 for speed change and the multi-plate clutches 66 and 67 for speed reduction on the shaft.

[0128] That is, the main transmission 32 can be arranged in the internal space of the second housing 22 in a state where the left-right balance is improved with a low center of gravity. As a result, the stability of the tractor including the transmission 3 including the main transmission 32 can be improved.

[0129] like Figure 8 As shown, in the main transmission device 32, three transmission shafts 51 to 53 are arranged in parallel, and the second transmission shaft 52 (intermediate shaft) on which the multi-plate clutches 60 to 63 for speed change and the multi-plate clutches 66 and 67 for speed reduction are not arranged enters the upper space 90 in a pair of upper and lower imaginary spaces 90 and 91 of a roughly triangular shape formed between the multi-plate clutches 60 to 63 for speed change and the multi-plate clutches 66 and 67 for speed reduction.

[0130] That is, when observing from the front of the vehicle body, in a virtual space having an imaginary line connecting the axis of the first transmission shaft 51 (speed change shaft) and the axis of the third transmission shaft 53 (reduction shaft) as one side, and forming a pair of triangles (triangles with a height greater than the above-mentioned isosceles triangles, such as equilateral triangles) above and below the imaginary line, the second transmission shaft 52 (intermediate shaft) exists inside the imaginary space 90 on one side (here, the upper side). This is referred to as "entry" in this specification. In addition, in the following description, the imaginary spaces 90 and 91 are simply referred to as "spaces 90 and 91".

[0131] This can shorten the vertical length of the main transmission 32 and the transmission 3 including the main transmission 32. As a result, the height of the cab 2 disposed above the transmission 3 can be lowered, and the vehicle height of the tractor can be lowered.

[0132] Furthermore, as described above, the second transmission shaft 52 is a cylindrical shaft relatively rotatably fitted on the upstream relay shaft 42 of the working transmission system 20, so the upstream relay shaft 42 also enters the upper space 90 formed between the speed-changing multi-plate clutches 60 to 63 and the speed-reducing multi-plate clutches 66 and 67. Thus, the upstream relay shaft 42 can be arranged in the internal space of the second housing 22 without ensuring a dedicated arrangement space for the upstream relay shaft 42 to pass through.

[0133] like Figure 8 As shown, the first transmission shaft 51 and the second transmission shaft 52 among the three transmission shafts 51 to 53 are distributed and configured on the left and right sides so that their axes are in a positional relationship that is roughly symmetrical on the left and right sides with respect to the line connecting the axis of at least one of the front wheel transmission shaft 80 and the first output shaft 16 and the axis of the second transmission shaft 52 as a reference.

[0134] [Configuration of multi-plate clutch]

[0135] like Figure 8 As shown, in the drive switching unit 37, the multi-plate clutch 84 for constant speed transmission and the multi-plate clutch 86 for speed increasing transmission are arranged below the main transmission device 32 with their upper sides entering into the lower space 91 formed between the multi-plate clutches 60 to 63 for speed change and the multi-plate clutches 66 and 67 for speed reduction.

[0136] Thus, the vertical length of the second housing 22 in which the main transmission 32 and the drive switching unit 37 are arranged in the internal space can be shortened, and the vertical length of the transmission 3 equipped therewith can be shortened. As a result, the height position of the cab 2 arranged above the transmission housing 14 can be lowered, and the vehicle height of the tractor can be lowered.

[0137] Furthermore, by arranging the multi-plate clutch 84 for constant speed transmission and the multi-plate clutch 86 for speed increasing transmission below the main transmission 32, the center of gravity of the transmission 3 including the main transmission 32 and the drive switching unit 37 can be lowered compared to a case where the multi-plate clutches 84 and 86 are arranged above the main transmission 32. As a result, the stability of the tractor including the transmission 3 can be improved.

[0138] [Detailed structure of multi-plate clutch]

[0139] like Figure 2 to Figure 5 , Figure 8 As shown, the forward / reverse switching device 31, the main transmission device 32, the first drive switching device 81 and the second drive switching device 82 of the five transmission switching devices (31, 32, 44, 81, 82) equipped in the travel transmission system 19 are arranged as transmission switching devices for travel in the internal space of the second housing 22. On the other hand, the working power switching device 44 equipped in the working transmission system 20 is arranged in the internal space of the fourth housing 24 as a transmission switching device for working.

[0140] That is, in the transmission 3, the transmission switching devices for driving (forward-reverse switching device 31, main transmission device 32, first drive switching device 81, second drive switching device 82) having multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86 which are disconnected / connected by means of electronic oil pressure control are concentrated in the internal space of the second housing 22, so the oil pressure operating system relative to the transmission switching devices (31, 32, 81, 82) for driving can be easily constructed in a state concentrated in the second housing 22.

[0141] The forward / reverse switching device 31, the main transmission device 32, the first drive switching device 81 and the second drive switching device 82, which are equipped as transmission switching devices for driving, have the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86 in all of them set to the same size in radial direction.

[0142] Thus, the clutch plates (driving plates and driven plates) 92, pressure plates 93, pistons 94, etc. used in the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86 can be made into common parts whose radial sizes are common to all the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86. As a result, it is possible to achieve easy parts management.

[0143] Furthermore, in controlling the disconnection / connection operation of each multi-plate clutch 45, 46, 60 to 63, 66, 67, 84, 86 by electronic hydraulic control, the piston 94 and the like are common parts, and thus, by making the initial pressures for each multi-plate clutch 45, 46, 60 to 63, 66, 67, 84, 86 the same, the timing of clutch engagement of each multi-plate clutch 45, 46, 60 to 63, 66, 67, 84, 86 can be made the same. As a result, it is easy to create each control program required for appropriately controlling the disconnection / connection operation of each multi-plate clutch 45, 46, 60 to 63, 66, 67, 84, 86 by electronic hydraulic control.

[0144] In the travel transmission system 19, the multi-plate clutch 66 for deceleration on the low-speed side provided in the second speed change mechanism 55 of the main transmission device 32 disconnects / connects the travel power with a larger torque after deceleration by the low-speed reduction gear group 64 in the main transmission device 32 and before being branched into front wheel drive and rear wheel drive. Therefore, the load condition becomes severe compared with the other multi-plate clutches 45, 46, 60 to 63, 67, 84, 86 provided in each of the forward and reverse switching device 31, the main transmission device 32, the first drive switching device 81 and the second drive switching device 82.

[0145] The forward-reverse switching device 31, the main transmission device 32, the first drive switching device 81 and the second drive switching device 82, the radial sizes of the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86 included in all of them are set to the same size to suit the larger size of the multi-plate clutch 66 for deceleration on the low-speed side where the load conditions are the most severe.

[0146] Thus, in the other multi-plate clutches 45, 46, 60 to 63, 67, 84, 86 that have a margin in terms of load conditions compared to the multi-plate clutch 66 for speed reduction on the low speed side, the number of clutch plates 92 equipped therein can be reduced, and their lengths in the axial direction (vehicle front-back direction) can be shortened. In addition, in the forward / reverse switching device 31, the main transmission device 32, the first drive switching device 81, and the second drive switching device 82 that have the multi-plate clutches 45, 46, 60 to 63, 67, 84, 86 that can shorten the length in the axial direction, the lengths in the vehicle front-back direction can be shortened, and the front-back length of the transmission 3 equipped therewith can be shortened. As a result, it is possible to prevent the tractor from being enlarged due to the increase in the front-back length of the transmission 3 and the increase in the total length of the tractor.

[0147] In addition, in the above-mentioned structure, the radial size of each multi-plate clutch 45, 46, 60-63, 66, 67, 84, 86 is enlarged, and the upper and lower pairs of spaces 90, 91 formed in a substantially triangular shape between the speed-changing multi-plate clutch 60-63 and the speed-reducing multi-plate clutch 66, 67 are also enlarged. As a result, the second transmission shaft 52 and the upstream relay shaft 42 that have entered the upper space 90 as described above can enter deeper into the upper space 90. In addition, the upper side of the multi-plate clutch 84 for constant speed transmission and the multi-plate clutch 86 for speed-increasing transmission that have entered the lower space 91 as described above can enter deeper into the lower space 91.

[0148] As a result, the radial sizes of the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, and 86 can be set to the same size as the larger size of the multi-plate clutch 66 for deceleration on the low-speed side where the load conditions are most severe, while suppressing the occurrence of the undesirable condition in which the vertical length of the transmission 3 equipped therewith becomes longer.

[0149] In addition, in the main transmission 32, the multi-plate clutch 66 for speed reduction on the low speed side and the multi-plate clutch 67 for speed reduction on the high speed side disconnect / connect the power for travel with a large torque after deceleration obtained by the low speed reduction gear group 64 or the high speed reduction gear group 65, so the load condition becomes severer than that of each multi-plate clutch 60 to 63 for speed change that disconnects / connects the power for travel with a small torque before deceleration. Therefore, if the radial sizes of the multi-plate clutches 60 to 63, 66, and 67 provided in the main transmission 32 are set to the same size as described above, each multi-plate clutch 66 for speed reduction has a larger number of clutch plates 92 than each multi-plate clutch 60 to 63 for speed change, and its length in the axial direction (vehicle front-rear direction) becomes longer.

[0150] Taking this into consideration, in the main transmission 32, four multi-plate clutches 60 to 63 for speed change with shortened lengths in the axial direction are arranged adjacent to each other in the front-to-rear direction on the shaft of the first transmission shaft 51. In addition, two multi-plate clutches 66 and 67 for speed reduction with shortened lengths in the axial direction are arranged adjacent to each other in the front-to-rear direction on the shaft of the third transmission shaft 53.

[0151] Thus, compared with a case where, for example, two of the four multi-plate clutches 60 to 63 for speed change whose axial length is short are arranged adjacent to each other in the front-rear direction on the shaft of the first transmission shaft 51, and the remaining two are arranged adjacent to each other in the front-rear direction together with the two multi-plate clutches 66 and 67 for speed reduction whose axial length is long on the shaft of the third transmission shaft 53, the front-rear length of the main transmission device 32 can be shortened. As a result, the front-rear length of the transmission 3 having the main transmission device 32 can be shortened, and in a tractor having the transmission 3, the enlargement of the tractor can be prevented from being lengthened in total.

[0152] like Figure 4-5 As shown, in each of the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86 that has been enlarged in diameter as described above, the piston 94 is not enlarged in diameter as a whole, but is formed into a stepped shape in which only the pressing portion 94A that presses the clutch plate 92 is enlarged in diameter.

[0153] Thus, it is possible to prevent the responsiveness of the piston 94 from being reduced due to the increase in the volume of the piston 94 when the overall diameter of the piston 94 is increased. In addition, it is possible to prevent the centrifugal force generated when the piston 94 rotates due to the increase in the volume of the piston 94, and thus, a small-diameter spring with a weaker spring force can be used as the return spring 95 whose spring force is required to overcome the centrifugal force.

[0154] like Figure 2 to Figure 5 As shown, in the forward / reverse switching device 31, the forward multi-plate clutch 45 and the reverse multi-plate clutch 46 adjacent to each other share a single clutch housing 96. In the main transmission 32, the 1st-speed multi-plate clutch 60 and the 2nd-speed multi-plate clutch 61 adjacent to each other among the four speed-changing multi-plate clutches 60 to 63 share a single clutch housing 97, and the 3rd-speed multi-plate clutch 62 and the 4th-speed multi-plate clutch 63 adjacent to each other share a single clutch housing 98. Furthermore, the 2 speed-reducing multi-plate clutches 66 and 67 adjacent to each other share a single clutch housing 99.

[0155] As a result, the forward and reverse switching device 31 and the main transmission device 32 can be made compact in the front-to-rear direction due to the front-to-rear adjacent multi-plate clutches 45, 46, 60-63, 66, 67 sharing the clutch housing 97-99, and the assemblability can be improved due to the reduction in the number of parts.

[0156] The forward / reverse switching device 31 , the main transmission device 32 , the first drive switching device 81 , and the second drive switching device 82 have respective lengths of the clutch housings 96 to 99 and the clutch hubs 100 to 103 that allow for the addition of the clutch plates 92 .

[0157] Thus, the forward / reverse switching device 31, the main transmission device 32, the first drive switching device 81, and the second drive switching device 82 included in the transmission 3 can be easily adapted to other tractors with severe load conditions, such as those equipped with a large-horsepower engine 9, without increasing the size of the transmission 3. That is, the transmission 3 can be made into a highly versatile structure that can be adopted in other tractors with different specifications.

[0158] [Detailed structure of the drive switching unit]

[0159] like Figure 2 As shown, in the drive switching unit 37, the first drive switching device 81 unitizes the first reduction gear 83A of the reduction gear group 83 disposed on the shaft of the front wheel transmission shaft 80 and the multi-plate clutch 84 for constant speed transmission and the like with the front wheel transmission shaft 80. The second drive switching device 82 unitizes the first speed increasing gear 85A of the speed increasing gear group 85 disposed on the shaft of the front wheel transmission shaft 80 and the multi-plate clutch 84 for speed increasing transmission and the like.

[0160] That is, in the drive switching unit 37 , the first drive switching device 81 and the second drive switching device 82 are separately unitized without the second reduction gear 83B of the reduction gear group 83 and the second speed increasing gear 85B of the speed increasing gear group 85 arranged on the shaft of the first output shaft 16 .

[0161] Therefore, in the drive switching unit 37, the speed increasing gear set 85 can be arranged between the first drive switching device 81 and the second drive switching device 82, and there is no need to arrange the speed increasing gear set 85 behind the second drive switching device 82 as in the case where the first drive switching device 81 and the second drive switching device 82 are integrated into a unit.

[0162] As a result, the distance between the speed increasing gear set 85 and the speed reducing gear set 83 can be shortened, and the speed reducing gear set 83 is arranged closer to the front side of the vehicle body than the first drive switching device 81, and the front-to-rear length of the first output shaft 16 on which the second speed reducing gear 83B of the speed reducing gear set 83 and the second speed increasing gear 85B of the speed increasing gear set 85 are arranged on the shaft, and the front-to-rear length of the fifth housing 25 supporting the first output shaft 16 can be shortened. As a result, the transmission 3 equipped with the same can be made lighter in weight.

[0163] like Figure 2 As shown in FIG. 1 , the drive switching unit 37 is provided with the second drive switching device 82 which is unitized as described above so as to be attachable to and detachable from the front wheel propeller shaft 80 .

[0164] Thus, by performing a simple operation of disassembling the unitized second drive switching device 82 relative to the front wheel transmission shaft 80, the drive switching unit 37 specification can be easily changed to: a standard specification, which can switch to a two-wheel drive state and a four-wheel drive state by only having the first drive switching device 81; and a front wheel speed-increasing specification, which can switch to a two-wheel drive state, a four-wheel drive state, and a front wheel speed-increasing state by having the first drive switching device 81 and the second drive switching device 82. As a result, the versatility of the transmission 3 can be improved.

[0165] like Figure 2 As shown, the first output shaft 16 is constructed by being arranged on its shaft in a state of integral rotation through the second reduction gear 83B and the second speed increasing gear 85B, and can be used in both the standard specification (unassembled specification) without the second drive switching device 82 installed, and the front wheel speed increasing specification (assembled specification) with the second drive switching device 82 installed.

[0166] Thus, when the specification of the drive switching unit 37 is changed to the standard specification or the front wheel speed increasing specification, it is no longer necessary to replace the first output shaft 16 in accordance with the specification change. As a result, the specification change of the drive switching unit 37 can be facilitated.

[0167] Although omitted in the figure, the tractor is equipped with an electronic control unit, which outputs various control instructions such as forward and reverse switching instructions, speed change instructions and front-wheel drive switching instructions based on the operation of the forward and reverse switching lever, main speed change lever, front-wheel drive selection switch and differential lock pedal equipped in the driving part 2.

[0168] [Hydraulic equipment]

[0169] like Figure 2-3 , Figure 8 As shown, in this tractor, the forward / reverse switching device 31, the main transmission device 32, the drive switching unit 37, the rear wheel differential device 38, and the front wheel differential device are hydraulic devices that are electronically hydraulically controlled by the control operation of the electronic control unit. In addition, the forward / reverse switching device 31, the main transmission device 32, the drive switching unit 37, and the rear wheel differential device 38 among these hydraulic devices are equipped inside the transmission case 14.

[0170] like Figure 2-3 , Fig. 9 As shown, the transmission 3 includes a pump unit 104 for pressurizing the oil stored in the transmission case 14 toward various hydraulic devices such as the forward / reverse switching device 31 , and a valve unit 105 for controlling the flow of oil relative to various hydraulic devices such as the forward / reverse switching device 31 .

[0171] When the pump unit 104 and the valve unit 105 are arranged at the upper end of the transmission case 14, the pump unit 104 and the valve unit 105 may come into contact with the cab 11 supported by the transmission 3 for vibration isolation due to the vibration during driving, so in order to avoid such contact, they are arranged at the right side of the transmission case 14. In addition, since the right side of the transmission case 14 is a lateral side open to the outside that is not adjacent to the fuel tank 4, it is easy to perform maintenance on the pump unit 104 and the valve unit 105.

[0172] like Figure 2-3 , Figure 9-10 As shown, the transmission case 14 has a pump unit mounting portion 106 to which the pump unit 104 is mounted from the right outer side thereof, and a valve unit mounting portion 107 to which the valve unit 105 is mounted from the right outer side of the transmission case 14. The pump unit mounting portion 106 bulges toward the right outer side from the right side portion of the third case 23 of the transmission case 14. The valve unit mounting portion 107 is formed on the right side portion of the second case 22 of the transmission case 14.

[0173] like Figure 2-3 As shown, the pump unit 104 includes a first double hydraulic pump 104A mounted on the front end of the pump unit mounting portion 106, and a second hydraulic pump 104B mounted on the rear end of the pump unit mounting portion 106. The first hydraulic pump 104A and the second hydraulic pump 104B are driven by power transmitted from the working transmission system 20 via a pump driving gear group 108. The pump driving gear group 108 includes a first gear 108A that also serves as a coupling that links the upstream side relay shaft 42 and the downstream side relay shaft 43 of the working transmission system 20, a second gear 108B for relaying, and a third gear 108C for output.

[0174] [Valve unit]

[0175] like Figure 3 , Fig. 9 , Figure 11-12 As shown, the valve unit 105 includes a bottom plate 110 mounted on a valve unit mounting portion 107 , a first valve body 111 and a second valve body 112 each including a plurality of electromagnetic valves, and the like.

[0176] The first valve body 111 has a plurality of electromagnetic valves: an electromagnetic switch valve 113 for forward movement, which switches the flow of oil relative to the forward multi-plate clutch 45; an electromagnetic switch valve 114 for reverse movement, which switches the flow of oil relative to the reverse multi-plate clutch 46; an electromagnetic switch valve 115 for 1st speed, which switches the flow of oil relative to the 1st speed multi-plate clutch 60; an electromagnetic switch valve 116 for 2nd speed, which switches the flow of oil relative to the 2nd speed multi-plate clutch 61; an electromagnetic switch valve 117 for 3rd speed, which switches the flow of oil relative to the 3rd speed multi-plate clutch 62; an electromagnetic switch valve 118 for 4th speed, which switches the flow of oil relative to the 4th speed multi-plate clutch 63; an electromagnetic switch valve 119 for 5th speed, which switches the flow of oil relative to the 5th speed multi-plate clutch 64; an electromagnetic switch valve 110 for 6th speed, which switches the flow of oil relative to the 6th speed multi-plate clutch 65; an electromagnetic switch valve 111 for 7th speed, which switches the flow of oil relative to the 7th speed multi-plate clutch 66; an electromagnetic switch valve 112 for 8th speed, which switches the flow of oil relative to the 8th speed multi-plate clutch 67; an electromagnetic switch valve 113 for 9th speed, which switches the flow of oil relative to the 9th speed multi-plate clutch 68; an electromagnetic switch valve 114 for 15th speed, which switches the flow of oil relative to the 15th speed multi-plate clutch 69; an electromagnetic switch valve 115 for 1st speed, which switches the flow of oil relative to the 15th speed multi-plate clutch 60; an electromagnetic switch valve 116 for 2nd speed, which switches the flow of oil relative to the 2nd speed multi-plate clutch 61; an electromagnetic switch valve 117 for 3rd The magnetic switch valve 118 switches the flow of oil relative to the multi-plate clutch 63 for 4th speed; the electromagnetic switch valve 119 for constant speed transmission switches the flow of oil relative to the multi-plate clutch 84 for constant speed transmission; the electromagnetic switch valve 120 for speed-increasing transmission switches the flow of oil relative to the multi-plate clutch 86 for speed-increasing transmission; the electromagnetic switch valve 121 for rear wheel differential switches the flow of oil relative to the differential switching mechanism 38B of the rear wheel differential device 38; and the electromagnetic switch valve 122 for front wheel differential switches the flow of oil relative to the differential switching mechanism of the front wheel differential device.

[0177] The second valve body 112 serves as a plurality of solenoid valves, including: an electromagnetic proportional valve 123 for forward and reverse movement, which continuously controls the flow of oil relative to the forward multi-plate clutch 45 and the reverse multi-plate clutch 46; an electromagnetic proportional valve 124 for low speed, which continuously controls the flow of oil relative to the deceleration multi-plate clutch 66 on the low-speed side of the two deceleration multi-plate clutches 66 and 67; and an electromagnetic proportional valve 125 for high speed, which continuously controls the flow of oil relative to the deceleration multi-plate clutch 67 on the high-speed side of the two deceleration multi-plate clutches 66 and 67.

[0178] Although not shown in the figure, a plurality of internal oil passages related to the electronic hydraulic control of the forward / reverse switching device 31 , the main transmission device 32 , the drive switching unit 37 , etc. are formed in the base plate 110 , the first valve body 111 , and the second valve body 112 .

[0179] [Valve unit mounting section]

[0180] like Figures 9 to 11 As shown, a recessed portion 107A is formed on the valve unit mounting portion 107 to define a storage chamber 126 for the first valve body between the bottom plate 110 and the first valve body 111. The first valve body 111 is assembled to a storage chamber forming surface 110A in the bottom plate 110, and the storage chamber forming surface 110A forms the storage chamber 126 between the recessed portion 107A of the valve unit mounting portion 107. The second valve body 112 is assembled to an outer surface 110B of the bottom plate 110 on the opposite side to the storage chamber forming surface 110A.

[0181] Thus, the valve unit 105 is configured such that, in a state in which the valve unit 105 is mounted on the valve unit mounting portion 107 of the transmission case 14, the first valve body 111 having 10 electromagnetic switch valves 113 to 122 is accommodated in an accommodation chamber 126 formed in the right side portion of the transmission case 14 and in the internal space of the transmission case 14. In addition, the second valve body 112 having three electromagnetic proportional valves 123 to 125 is arranged in the right side portion of the transmission case 14 at a position laterally outward of the accommodation chamber 126.

[0182] With the above-mentioned structure, it is possible to prevent iron powder and the like contained in the oil stored in the transmission case 14 from being attracted toward the valve unit 105 due to the excitation of each electromagnetic switch valve 113 to 122 and each electromagnetic proportional valve 123 to 125. As a result, it is possible to avoid the possibility that the iron powder and the like contained in the oil in the transmission case 14 due to the attraction enters the interior of the valve unit 105 and is bitten into any of the electromagnetic switch valves 113 to 122 and each electromagnetic proportional valve 123 to 125.

[0183] In addition, since there is no need to form an opening on the valve unit mounting portion 107 for allowing the first valve body 111 to enter the internal space of the transmission housing 14 as in the case where the first valve body 111 is arranged in the internal space of the transmission housing 14, a decrease in the strength of the transmission housing 14 due to the formation of the opening can be prevented.

[0184] Furthermore, by accommodating the first valve body 111 having the electromagnetic switch valves 113 to 122 with a high possibility of oil leakage in the accommodating chamber 126 and arranging the second valve body 112 having the electromagnetic proportional valves 123 to 125 with a low possibility of oil leakage outside the transmission case 14, it is possible to narrow the recessed portion 107A for the accommodating chamber formed in the transmission case 14 while preventing oil leakage to the outside, and to enlarge the internal space of the transmission case 14. As a result, it is easy to arrange and assemble the travel transmission system 19 and the working transmission system 20 arranged in the internal space of the transmission case 14.

[0185] The valve unit 105 is set at its installation height position so that when installed on the valve unit mounting portion 107 of the transmission case 14 , at least the upper end of the first valve body 111 is located at a position higher than the height position of the oil level stored in the transmission case 14 .

[0186] [Return oil passage of valve unit mounting section]

[0187] like Figure 3 , Figures 9 to 11As shown, the valve unit mounting portion 107 has seven return oil passages 107B formed in the recess 107A at a position above the first valve body 111 of the vehicle body for returning excess oil from the first valve body 111 to the interior of the transmission case 14 .

[0188] Thus, the oil leaking from each electromagnetic switch valve 113 to 122 of the first valve body 111 can be stored as lubricating oil in a position on the upper side of the vehicle body in the storage chamber 126 relative to the first valve body 111. Furthermore, when the oil level of the lubricating oil reaches the return oil passage forming portion of the storage chamber 126, the lubricating oil reaching the return oil passage forming portion can be sent back to the inside of the transmission case 14 from each return oil passage 107B as excess oil. In addition, the oil accumulated in the inside of the transmission case 14 due to a large tilt of the tractor, etc., can be prevented from flowing into the storage chamber 126 from each return oil passage 107B together with iron powder and the like contained in the oil.

[0189] like Figures 9 to 11 As shown, in the valve unit mounting portion 107, the seven return oil passages 107B are divided into two layers, upper and lower, thereby making it less likely to cause the oil accumulated in the transmission case 14 to flow into the storage chamber 126 from each return oil passage 107B together with iron powder and the like contained in the oil, compared with the case where all the return oil passages 107B are formed at the same height.

[0190] The return oil passages 107B of the upper and lower layers are formed by forming three return oil passages 107B in the upper layer and four return oil passages 107B in the lower layer so that the opening area of ​​the return oil passages 107B in the upper layer is smaller than that of the return oil passages 107B in the lower layer.

[0191] This is based on the consideration that: when the return oil circuit 107B is divided into two layers, the majority of the remaining oil returns to the interior of the transmission case 14 from the lower return oil circuit 107B, and the upper return oil circuit 107B is used auxiliary when a large amount of oil leaks from each solenoid switch valve 113 to 122. Thus, it is possible to prevent a decrease in the strength of the transmission case 14 caused by unnecessary expansion of the opening area of ​​the upper return oil circuit 107B used auxiliary.

[0192] like Figure 3 , Fig. 9 , Fig.11As shown, each return oil passage 107B is provided with an oil filter 127. Thus, even if the oil accumulated in the transmission case 14 flows from each return oil passage 107B into the storage chamber 126, iron powder and the like contained in the oil can be prevented from flowing into the storage chamber 126. In addition, as described above, the seven return oil passages 107B are divided into two layers, upper and lower, and when the mesh of the oil filter 127 provided in the return oil passage 107B of the lower layer is clogged, the remaining oil in the storage chamber 126 can be sent back to the inside of the transmission case 14 from the return oil passage 107B of the upper layer.

[0193] [Valve unit mounting recess]

[0194] like Figures 9 to 11 As shown, in the valve unit mounting portion 107, the recessed portion 107A includes a lower recessed portion 107a for accommodating the first valve body 111, and an upper recessed portion 107b communicating with the interior of the transmission case 14 via each return oil passage 107B. The upper recessed portion 107b is formed narrower than the lower recessed portion 107a with a shallower recessed depth than the lower recessed portion 107a.

[0195] Thus, the internal space of the transmission case 14 can be made larger than, for example, the case where the upper recessed portion 107b that does not accommodate the first valve body 111 is formed to have the same recessed depth and width as the lower recessed portion 107a. As a result, the arrangement and assembly of the travel transmission system 19 and the working transmission system 20, etc., which are arranged in the internal space of the transmission case 14, can be easily performed.

[0196] Although not shown in the figure, the input shaft 15 of the transmission 3 has a forward oil passage spanning the front portion of the input shaft 15 supported by the front cover 27 and the forward multi-plate clutch 45, and a reverse oil passage spanning the front portion of the input shaft 15 supported by the front cover 27 and the reverse multi-plate clutch 46, etc. The front wheel drive shaft 80 of the drive switching unit 37 has a constant speed oil passage spanning the rear end portion of the front wheel drive shaft 80 supported by the first support wall 28 and the constant speed transmission multi-plate clutch 84, and a speed-increasing oil passage spanning the rear end portion of the front wheel drive shaft 80 supported by the first support wall 28 and the speed-increasing oil passage, etc.

[0197] [Oil passages in the valve unit mounting area]

[0198] like Figure 4-5 , Figure 8 to Figure 11As shown, in the main transmission device 32, the three transmission shafts 51 to 53 are configured so that the lower end of the second transmission shaft (intermediate shaft) 52 is located closer to the upper side of the vehicle body than the upper end of the first transmission shaft (speed change shaft) 51 and the upper end of the third transmission shaft (reduction shaft) 53, and the upper end of the first transmission shaft 51 is located closer to the lower side of the vehicle body than the upper end of the third transmission shaft 53. In the first transmission shaft 51, there are formed: a 1st speed oil circuit 51A, spanning the front end portion of the first transmission shaft 51 supported by the partition wall 22B of the second housing 22 and the 1st speed multi-plate clutch 60; a 2nd speed oil circuit 51B, spanning the front end portion of the first transmission shaft 51 supported by the partition wall 22B of the second housing 22 and the 2nd speed multi-plate clutch 61; a 3rd speed oil circuit 51C, spanning the front end portion of the first transmission shaft 51 supported by the partition wall 22B of the second housing 22 and the 3rd speed multi-plate clutch 62; and a 4th speed oil circuit 51D, spanning the front end portion of the first transmission shaft 51 supported by the partition wall 22B of the second housing 22 and the 4th speed multi-plate clutch 63; etc. In the third transmission shaft (reduction shaft) 53, there are formed a low-speed oil passage 53A spanning the front end portion of the third transmission shaft 53 supported by the partition wall 22B of the second housing 22 and the multi-plate clutch 66 for reduction on the low-speed side, and a high-speed oil passage 53B spanning the front end portion of the third transmission shaft 53 supported by the partition wall 22B of the second housing 22 and the multi-plate clutch 67 for reduction on the high-speed side.

[0199] The valve unit mounting portion 107 is formed in the second housing 22 of the transmission housing 14 at a predetermined position in the front-rear direction of the vehicle body where a partition wall 22B is formed. The partition wall 22B is formed with: an internal oil passage 22C for the first speed, which crosses the connection port 105A for the first speed formed on the valve unit 105 and the oil passage 51A for the first speed formed in the first transmission shaft 51; an internal oil passage 22D for the second speed, which crosses the connection port 105B for the second speed formed on the valve unit 105 and the oil passage 51B for the second speed formed in the first transmission shaft 51; an internal oil passage 22E for the third speed, which crosses the connection port 105C for the third speed formed on the valve unit 105 and the oil passage 51A for the third speed formed in the first transmission shaft 51; 51C; the internal oil circuit 22F for 4th speed, spanning over the 4th speed connection port 105D formed on the valve unit 105 and the 4th speed oil circuit 51D formed in the first transmission shaft 51; the internal oil circuit 22G for low speed, spanning over the low speed connection port 105E formed on the valve unit 105 and the low speed oil circuit 53A formed in the third transmission shaft 53; and the internal oil circuit 22H for high speed, spanning over the high speed connection port 105F formed on the valve unit 105 and the high speed oil circuit 53B formed in the third transmission shaft 53; etc.

[0200] Thus, in forming each of the six hydraulic paths for the main transmission across the valve unit 105 and each of the multi-plate clutches 60 to 63, 66, and 67 of the main transmission device 32, it is not necessary to assemble the hydraulic pipe into the interior of the transmission case 14. In addition, each of the internal oil paths 22C to 22H across the valve unit 105 and the partition wall 22B of the first transmission shaft 51 or the third transmission shaft 53 can be formed in a simple straight line shape to be the shortest. As a result, the number of work steps required to form each hydraulic path for the main transmission can be reduced.

[0201] Furthermore, by forming each internal oil passage 22C to 22H of the partition wall 22B in a simple straight line shape and being the shortest, each hydraulic path of the six systems for the main transmission across the valve unit 105 and each multi-plate clutch 60 to 63, 66, 67 of the main transmission device 32 can be formed in a simple shape and be the shortest. As a result, the responsiveness of each multi-plate clutch 60 to 63, 66, 67 in the main transmission device 32 is improved.

[0202] like Figure 3 , Fig. 9 As shown, the valve unit mounting portion 107 is arranged closer to the first transmission shaft 51 supporting the four speed-changing multiple plate clutches 60 to 63 than the third transmission shaft 53 supporting the two speed-reducing multiple plate clutches 66 and 67 .

[0203] Thus, the number of the long internal oil passages 22G and 22H formed in the partition wall 22B can be reduced compared to the case where the valve unit mounting portion 107 is arranged at a position closer to the third transmission shaft 53 than the first transmission shaft 51. As a result, it is possible to prevent the strength of the partition wall 22B from decreasing due to an increase in the number of the long internal oil passages 22G and 22H formed in the partition wall 22B.

[0204] [Detailed structure of the creeper gear]

[0205] like Figure 2-3 , Figure 5 , Fig.13As shown, in the creeper transmission 33, the speed reduction mechanism 69 includes: a speed reduction shaft 130, which is arranged in parallel with the third transmission shaft 53 of the main transmission 32 and the first speed change shaft 68 of the auxiliary transmission 34; a first speed reduction gear 71A, which is arranged on the shaft of the third transmission shaft 53 in a state of integral rotation with the third transmission shaft 53; a second speed reduction gear 71B and a third speed reduction gear 72A, which are arranged on the shaft of the speed reduction shaft 130 in a state of integral rotation with the speed reduction shaft 130; and a fourth speed reduction gear 72B, which is arranged on the shaft of the first speed change shaft 68 in a state of relative rotation with the first speed change shaft 68; etc. And, the first speed reduction gear 71A and the second speed reduction gear 71B constitute the speed reduction gear group 71 on the upstream side of the transmission direction of the two speed reduction gear groups 71 and 72, which performs speed reduction transmission from the third transmission shaft 53 to the speed reduction shaft 130 at a larger speed ratio. The third reduction gear 72A and the fourth reduction gear 72B constitute the reduction gear 72 on the downstream side of the two reduction gear groups 71 and 72 in the transmission direction for reducing the transmission from the reduction shaft 130 to the first speed change shaft 68 at a larger speed ratio.

[0206] The speed reduction mechanism 69 has a first reduction gear 71A assembled to the third transmission shaft 53 , and a fourth reduction gear 72B assembled to the first speed change shaft 68 .

[0207] The switching mechanism 70 comprises: a first meshed rotating body 131, which is arranged on the shaft of the third transmission shaft 53 in such a manner as to rotate integrally with the third transmission shaft 53 while allowing movement in the axial direction relative to the third transmission shaft 53; a second meshed rotating body 132, which is arranged on the shaft of the first speed change shaft 68 in such a manner as to rotate relative to the first speed change shaft 68 while rotating integrally with the fourth reduction gear 72B; and a meshing rotating body 133, which is arranged on the shaft of the first speed change shaft 68 in such a manner as to rotate integrally with the first speed change shaft 68 while allowing movement in the axial direction across a constant speed position meshed with the first meshed rotating body 131 and a reduction speed position meshed with the second meshed rotating body 132; etc. The switching mechanism 70 is assembled on the first speed change shaft 68 (refer to Fig.13 ).

[0208] Thus, by assembling the switching mechanism 70 to the first speed-change shaft 68, it is possible to perform an operation confirmation of whether the meshing rotating body 133 crosses the constant speed position meshed with the first meshed rotating body 131 and the deceleration position meshed with the second meshed rotating body 132 without forcibly moving normally. Furthermore, if a malfunction occurs during the operation confirmation, the malfunction can be eliminated by performing fine adjustments of the rotating bodies 131 to 133 assembled on the first speed-change shaft 68. As a result, the assembly including the operation confirmation of the switching mechanism 70 can be facilitated.

[0209] Furthermore, in the creep speed change device 33, the first reduction gear 71A of the reduction mechanism 69 and the first meshed rotating body 131 of the switching mechanism 70 are formed independently of each other, so the load acting on the first reduction gear 71A does not affect the first meshed rotating body 131. Thus, the possibility that the load acting on the first reduction gear 71A affects the first meshed rotating body 131 and the durability of the first meshed rotating body 131 is reduced can be avoided.

[0210] like Fig.13 As shown in FIG. 1 , the switching mechanism 70 is formed as a unit with the fourth reduction gear 72B. This makes it easy to attach and detach the fourth reduction gear 72B and the switching mechanism 70 to and from the first speed change shaft 68.

[0211] like Figure 2-3 , Figure 5 , Fig.13 As shown, the transmission case 14 is provided with a split position of the second case 22 and the third case 23 at the configuration position of the creep speed change device 33 so as to be split into the second case 22 on the upstream side of the transmission direction having the third transmission shaft 53 and the third case 23 on the downstream side of the transmission direction having the first speed change shaft 68. Of the speed reduction mechanism 69, only the first reduction gear 71A is assembled to the second case 22 together with the third transmission shaft 53, and the substantially entire speed reduction mechanism 69 except the first reduction gear 71A is assembled to the third case 23 together with the first speed change shaft 68 and the switching mechanism 70.

[0212] Thus, when the creep speed change device 33 is assembled to the transmission case 14, the first reduction gear 71A of the reduction mechanism 69 can be assembled to the second case 22 together with the third transmission shaft 53 and the like from the end side of the second case 22 that is separated from the third case 23. In addition, the substantially entire reduction mechanism 69 except the first reduction gear 71A and the switching mechanism 70 can be assembled to the third case 23 together with the first speed change shaft 68 and the like from the end side of the third case 23 that is separated from the second case 22. Furthermore, by connecting the second housing 22 and the third housing 23, the first meshed rotating body 131 assembled on the third housing 23 is arranged on the shaft of the third transmission shaft 53 assembled on the second housing 22, and the second reduction gear 71B assembled on the third housing 23 is meshed with the first reduction gear 71A assembled on the second housing 22, thereby enabling the creep speed change device 33 to be assembled to the transmission housing 14 in a state of straddling the third transmission shaft 53 and the first speed change shaft 68. That is, the creep speed change device 33 can be assembled to the transmission housing 14 simply.

[0213] Furthermore, when the creep speed change device 33 is removed from the transmission case 14, the creep speed change device 33 can be separated into the first reduction gear 71A assembled to the second case 22, and the substantially entirety of the reduction mechanism 69 assembled to the third case 23 except the first reduction gear 71A, and the switching mechanism 70 by releasing the connection between the second case 22 and the third case 23. And, by this separation, the first reduction gear 71A can be removed from the second case 22 together with the third transmission shaft 53 and the like from the end side of the second case 22 separated from the third case 23. Furthermore, the substantially entirety of the reduction mechanism 69 except the first reduction gear 71A and the switching mechanism 70 can be removed from the third case 23 together with the first speed change shaft 68 and the like from the end side of the third case 23 separated from the second case 22. That is, the creeper shift device 33 can be easily removed from the transmission case 14 , thereby facilitating maintenance of the creeper shift device 33 .

[0214] like Figure 2 , Figure 5 , Fig.13 As shown, in the creeping speed change device 33, the front end of the reduction shaft 130 is supported by the first support wall 28, and the rear end is supported by the front end of the distribution shaft 35. The first reduction gear 71A is splined to the rear of the third transmission shaft 53, and is prevented from loosening by the stopper wheel 134. The second reduction gear 71B is splined to the front end side of the reduction shaft 130. The third reduction gear 72A is integrally formed at the rear end of the reduction shaft 130. The first engaged rotating body 131 is splined to the rear end of the third transmission shaft 53 in a state where the rotating body 135 splined to the front end of the first speed change shaft 68 is supported so as to be relatively rotatable. The second engaged rotating body 132 is engaged and connected to the fourth reduction gear 72B so as to rotate integrally with the fourth reduction gear 72B. The engaging rotating body 133 is splined to the outer periphery of the rotating body 135. That is, in the creep speed change device 33, the reduction shaft 130, the second reduction gear 71B and the third reduction gear 72A are unitized into the first unit 33A and are detachably mounted on the third housing 23. In addition, the fourth reduction gear 72B, the first meshed rotating body 131, the second meshed rotating body 132, the meshing rotating body 133 and the rotating body 135 are unitized into the second unit 33B and are detachably mounted on the third housing 23.

[0215] [Other embodiments of the creeper transmission device]

[0216] exist Fig.14 and Fig.15, another embodiment of the creep speed change device 33 is shown in which the structures of the first reduction gear 71A of the speed reduction mechanism 69 and the first meshed rotating body 131 of the switching mechanism 70 are different from those of the aforementioned creep speed change device 33 .

[0217] exist Fig.15 In the creeper transmission 33 shown, the first reduction gear 71A of the reduction mechanism 69 is arranged on the shaft of the third transmission shaft 53 in such a manner that the first reduction gear 71A rotates integrally with the third transmission shaft 53 while allowing movement in the axial direction relative to the third transmission shaft 53. Furthermore, the first reduction gear 71A of the reduction mechanism 69 and the first meshed rotating body 131 of the switching mechanism 70 are formed integrally.

[0218] Thus, compared with the case where the first reduction gear 71A and the first engaged rotation body 131 are formed independently of each other, it is possible to simplify the structure by reducing the number of parts.

[0219] exist Fig.15 In the creeping speed change device 33 shown, the reduction mechanism 69 and the switching mechanism 70 are assembled together with the first speed change shaft 68 on the third housing 23 in such a manner that as the second housing 22 and the third housing 23 are connected, the first reduction gear 71A and the first meshed rotating body 131 are arranged on the shaft of the third transmission shaft 53, and as the connection between the second housing 22 and the third housing 23 is released, the first reduction gear 71A and the first meshed rotating body 131 are removed from the shaft of the third transmission shaft 53.

[0220] More specifically, if Figure 2-3 , Fig.14 , Fig.15As shown, in the creeping transmission 33, the reduction mechanism 69 comprises: a reduction shaft 130, which is arranged in parallel with the third transmission shaft 53 of the main transmission 32 and the first speed shaft 68 of the auxiliary transmission 34; a first reduction gear 71A, which is arranged on the shaft of the third transmission shaft 53 in a manner that allows the third transmission shaft 53 to rotate integrally with the third transmission shaft 53 while allowing movement in the axial direction relative to the third transmission shaft 53; a second reduction gear 71B and a third reduction gear 72A, which are arranged on the shaft of the reduction shaft 130 in a state of rotating integrally with the reduction shaft 130; and a fourth reduction gear 72B, which is arranged on the shaft of the first speed shaft 68 in a state of rotating relative to the first speed shaft 68; etc. Furthermore, the first reduction gear 71A and the second reduction gear 71B constitute the reduction gear set 71 on the upstream side of the transmission direction of the two reduction gear sets 71 and 72, which performs reduction transmission from the third transmission shaft 53 to the reduction shaft 130 at a larger speed ratio. Furthermore, the third reduction gear 72A and the fourth reduction gear 72B constitute the reduction gear set 72 on the downstream side of the transmission direction of the two reduction gear sets 71 and 72, which performs reduction transmission from the reduction shaft 130 to the first speed change shaft 68 at a larger speed ratio.

[0221] The switching mechanism 70 comprises: a first meshed rotating body 131, which is arranged on the shaft of the third transmission shaft 53 in a manner that it rotates integrally with the third transmission shaft 53 while allowing movement in the axial direction relative to the third transmission shaft 53; a second meshed rotating body 132, which is arranged on the shaft of the first speed change shaft 68 in a manner that it rotates relative to the first speed change shaft 68 while rotating integrally with the fourth reduction gear 72B; and a meshing rotating body 133, which is arranged on the shaft of the first speed change shaft 68 in a manner that it rotates integrally with the first speed change shaft 68 while allowing movement in the axial direction across a constant speed position meshed with the first meshed rotating body 131 and a reduction position meshed with the second meshed rotating body 132; etc. The switching mechanism 70 is assembled on the first speed change shaft 68 together with the first reduction gear 71A and the fourth reduction gear 72B (refer to Fig.15 ).

[0222] In this way, by assembling the switching mechanism 70 together with the first reduction gear and the fourth reduction gear on the first speed-change shaft 68, it is possible to perform an action confirmation of whether the meshing rotating body 133 crosses the constant speed position meshed with the first meshed rotating body 131 and the reduction position meshed with the second meshed rotating body 132 without forcibly moving normally. Furthermore, if a malfunction occurs during the action confirmation, the malfunction can be eliminated by performing fine adjustments of the rotating bodies 131 to 133 assembled on the first speed-change shaft 68. As a result, the assembly including the action confirmation of the switching mechanism 70 can be facilitated.

[0223] like Figure 2-3 , Fig.14 , Fig.15 As shown, the transmission case 14 is provided with a division position of the second case 22 and the third case 23 at the configuration position of the creep speed change device 33 so as to be divided into the second case 22 on the upstream side of the transmission direction having the third transmission shaft 53 and the third case 23 on the downstream side of the transmission direction having the first speed change shaft 68. The reduction mechanism 69 and the switching mechanism 70 are assembled to the third case 23 together with the first speed change shaft 68 in such a manner that the first reduction gear 71A and the first meshed rotating body 131 are arranged on the shaft of the third transmission shaft 53 as the second case 22 and the third case 23 are connected, and the first reduction gear 71A and the first meshed rotating body 131 are removed from the shaft of the third transmission shaft 53 as the connection between the second case 22 and the third case 23 is released.

[0224] Thus, when the creep speed change device 33 is assembled to the transmission case 14, the speed reduction mechanism 69 and the switching mechanism 70 can be assembled to the third case 23 from the end side of the third case 23 that is separated from the second case 22 together with the first speed change shaft 68 and the like. And after the assembly, by coupling the second case 22 and the third case 23 so that the first reduction gear 71A and the first meshed rotating body 131 are arranged on the shaft of the third transmission shaft 53, the speed reduction mechanism 69 and the switching mechanism 70 can be assembled to the transmission case 14 in a state of straddling the third transmission shaft 53 and the first speed change shaft 68. That is, the creep speed change device 33 can be easily assembled in a state of straddling the third transmission shaft 53 and the first speed change shaft 68 inside the transmission case 14.

[0225] Furthermore, when the creep speed change device 33 is removed from the transmission case 14, the connection between the second case 22 and the third case 23 is released to separate the second case 22 and the third case 23, so that the first reduction gear 71A and the first meshed rotating body 131 can be removed from the shaft of the third transmission shaft 53, and the entire speed reduction mechanism 69 and the entire switching mechanism 70 can be left on the third case 23 together with the first speed change shaft 68 and the like. Furthermore, the speed reduction mechanism 69 and the switching mechanism 70 remaining on the third case 23 can be removed from the third case 23 together with the first speed change shaft 68 and the like from the end side of the third case 23 that is separated from the second case 22. That is, the creep speed change device 33 can be easily removed from the transmission case 14, thereby facilitating maintenance of the creep speed change device 33 and the like.

[0226] like Fig.15As shown, in the creep speed change device 33, the first reduction gear 71A of the reduction mechanism 69 and the first meshed rotating body 131 of the switching mechanism 70 are formed integrally. Thus, compared with the case where the first reduction gear 71A and the first meshed rotating body 131 are formed independently, it is possible to achieve a simplified structure due to a reduction in the number of parts.

[0227] like Figure 2 , Fig.14 , Fig.15 As shown, in the creeping speed change device 33, the front end of the reduction shaft 130 is supported by the first support wall 28, and the rear end thereof is supported by the front end of the distribution shaft 35. The first reduction gear 71A is splined to the rear of the third transmission shaft 53 in a state where it is formed integrally with the first engaged rotating body 131. The second reduction gear 71B is splined to the front end side of the reduction shaft 130. The third reduction gear 72A is formed integrally on the rear end of the reduction shaft 130. The first engaged rotating body 131 is splined to the rear end of the third transmission shaft 53 in a state where the rotating body 135 splined to the front end of the first speed change shaft 68 is supported so as to be relatively rotatable. The second engaged rotating body 132 is engaged and connected to the fourth reduction gear 72B so as to rotate integrally with the fourth reduction gear 72B. The engaging rotating body 133 is splined to the outer periphery of the rotating body 135. That is, in the creep speed change device 33, similarly to the aforementioned creep speed change device 33, the reduction shaft 130, the second reduction gear 71B and the third reduction gear 72A are detachably mounted on the third housing 23 in a state where they are unitized into the first unit 33A (see Figure 2 , Figure 7 On the other hand, in this creep speed change device 33, unlike the aforementioned creep speed change device 33, the first reduction gear 71A, the fourth reduction gear 72B, the first engaged rotating body 131, the second engaged rotating body 132, the engaging rotating body 133 and the rotating body 135 are detachably mounted on the third housing 23 in a state of being unitized into the second unit 33B.

[0228] [Arrangement of the main transmission and auxiliary transmission in the split transmission case]

[0229] like Figure 2-3 , Figure 6-7As shown, the main transmission device 32 and the auxiliary transmission device 34 are arranged in the transmission case 14, the main transmission device 32 is arranged on the upstream side in the transmission direction, and the auxiliary transmission device 34 is arranged on the downstream side in the transmission direction. When the transmission case 14 is divided into the second case 22 having the main transmission device 32 on the upstream side in the transmission direction and the third case 23 having the auxiliary transmission device 34 on the downstream side in the transmission direction, an opening 136 is formed at the front end of the third case 23 which is the dividing end of the third case 23 with the second case 22. In addition, in the auxiliary transmission device 34, the aforementioned output gear set 79 is replaceably arranged at the front end position of the auxiliary transmission device 34 which is close to the opening 136 of the third case 23.

[0230] Thus, in this tractor, by replacing the output gear set 79 with another output gear set 79 having a different gear ratio, the maximum vehicle speed setting of the tractor can be easily changed to a vehicle speed suitable for the work pattern performed by the user. Furthermore, the output gear set 79 can be easily replaced from the opening 136 of the third housing 23, which is exposed when the transmission case 14 is divided into the second housing 22 and the third housing 23 for the replacement. That is, by the simple replacement operation of the output gear set 79 from the opening 136 of the third housing 23, the maximum vehicle speed setting of the tractor can be easily changed to a vehicle speed suitable for the work pattern performed by the user.

[0231] In addition, as described above, the transmission case 14 is configured to be divided into the second case 22 on the upstream side in the transmission direction and the third case 23 on the downstream side in the transmission direction at the location where the creep speed change device 33 is arranged. The creep speed change device 33 is assembled to a position on the opening side of the interior of the third case 23, which is a location adjacent to the output gear group 79 across the second support wall 29. And the creep speed change device 33 is detachably equipped on the third case 23 in a state where it is substantially integral or in a state where the entirety is unitized into the first unit 33A and the second unit 33B.

[0232] Thus, when the output gear set 79 is replaced, first, the connection between the second case 22 and the third case 23 of the transmission case 14 is released, and the second case 22 and the third case 23 are separated. Next, the first unit 33A and the second unit 33B of the creeper speed change device 33 disposed on the opening side of the third case 23 are removed from the opening 136 of the third case 23 exposed by the separation, and then the second support wall 29 is removed, thereby enabling the output gear set 79 to be replaced from the opening 136 of the third case 23. Furthermore, by replacing the output gear set 79 from the opening 136 of the third case 23, the maximum vehicle speed setting of the tractor can be easily changed to a vehicle speed suitable for the working form performed by the user.

[0233] That is, while the creeper transmission device 33 is arranged at the dividing portion between the second housing 22 and the third housing 23 on the transmission housing 14, the output gear set 79 can be easily replaced from the opening 136 of the third housing 23, and the maximum speed setting of the tractor can be easily changed to a speed suitable for the working mode performed by the user.

[0234] [Other implementation methods]

[0235] The present invention is not limited to the configurations illustrated in the above embodiments, and other representative embodiments of the present invention are illustrated below. In addition, the configurations illustrated in the above embodiments may be combined with certain configurations of other embodiments as long as there is no contradiction.

[0236] [1] It is also possible that the transmission for the work vehicle includes a multi-plate clutch (PTO clutch) 87 for work equipped in a work power switching device 44 (an example of a transmission switching device), and the radial sizes of all the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86, 87 equipped in each transmission switching device (forward and reverse switching device 31, main transmission device 32, work power switching device 44, first drive switching device 81, second drive switching device 82) are set to the same size.

[0237] [2] Alternatively, the radial sizes of the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86, 87 of each transmission switching device (forward-reverse switching device 31, main transmission device 32, working power switching device 44, first drive switching device 81, second drive switching device 82) may be set to the same size, which is smaller than the size of the multi-plate clutch 66 suitable for the most severe load conditions.

[0238] [3] The structure of the main transmission 32 can be modified in various ways. For example, the main transmission 32 can be configured as a 12-speed transmission type having six multi-plate clutches for six-speed shifting and two multi-plate clutches 66 and 67 for two-speed shifting, or can be configured as an 18-speed transmission type having six multi-plate clutches for six-speed shifting and three multi-plate clutches for three-speed shifting.

[0239] That is, the number of speed stages of the main transmission device 32 can be changed in various ways. For example, the main transmission device 32 may be configured as a 12-speed transmission type having a first speed change mechanism 54 that changes the speed of input power in 6 stages and a second speed change mechanism 55 that changes the speed of the power obtained by the first speed change mechanism 54 in 2 stages, or may be configured as an 18-speed transmission type having a first speed change mechanism 54 that changes the speed of input power in 6 stages and a second speed change mechanism 55 that changes the speed of the power obtained by the first speed change mechanism 54 in 3 stages.

[0240] [4] The working power switching device 44 (an example of a transmission switching device) may be configured to include a multi-plate clutch for changing the speed of the working power.

[0241] [5] The first drive switching device 81 for front wheel driving and the second drive switching device 82 for front wheel speed increase may be integrally formed into a unit.

[0242] [6] The main transmission 32 may be configured such that the plurality of speed-changing multi-plate clutches 60 to 63 and the plurality of speed-reduction multi-plate clutches 66 and 67 are arranged in parallel so as to be adjacent to each other in the up-down direction (an example of the radial direction) of the vehicle body.

[0243] [7] The main transmission 32 may be arranged such that the three transmission shafts 51 to 53 form a substantially isosceles triangle with the intermediate shaft (the second transmission shaft 52 ) being the lower vertex.

[0244] [8] The main transmission 32 may be configured such that the radial sizes of the plurality of speed-changing multi-plate clutches 60 to 63 and the plurality of speed-reduction multi-plate clutches 66 and 67 are different.

[0245] [9] The main transmission 32 may be configured such that the intermediate shaft (second transmission shaft 52 ) enters the lower space 91 of a pair of substantially triangular upper and lower spaces 90 , 91 formed between the speed-changing multi-plate clutches 60 to 63 and the speed-reduction multi-plate clutches 66 , 67 .

[0246]

[10] The main transmission device 32 can also be constructed so that the lower side of the multi-plate clutches 84, 86 in the drive switching device (the first drive switching device 81, the second drive switching device 82) enters into the upper space 90 of a pair of upper and lower spaces 90, 91 of a roughly triangular shape formed between the multi-plate clutches 60~63 for shifting and the multi-plate clutches 66, 67 for deceleration.

[0247]

[11] The working vehicle transmission may include the valve unit mounting portion 107 formed on the left side of the transmission case 14 , or may include the valve unit mounting portion 107 formed on both left and right sides of the transmission case 14 .

[0248]

[12] The valve unit 105 may be configured such that the valve body 111 including all the solenoid valves (the solenoid on / off valves 113 to 122 and the solenoid proportional valves 123 to 125 ) included in the valve unit 105 is assembled onto the storage chamber forming surface 110A of the bottom plate 110 and is stored in the storage chamber 126 .

[0249]

[13] A single return oil passage 107B may be formed in the valve unit mounting portion 107, or a plurality of return oil passages 107B may be formed in a row in the front-rear direction of the vehicle body. Alternatively, two return oil passages 107B having the same opening area may be formed in two upper and lower layers.

[0250]

[14] The auxiliary transmission device 34 may be configured such that the output gear group 79 is located at a dividing end between the downstream side case (the third case 23 ) and the upstream side case (the second case 22 ).

[0251]

[15] In the above embodiment, the working vehicle is a tractor, but the present invention is not limited thereto. The working vehicle may be another working vehicle such as a lawn mower, a combine harvester, a rice transplanter, or a transport working vehicle.

Claims

1. A transmission for a working vehicle, comprising: A plurality of transmission shafts extending parallel to each other in the front-rear direction of the vehicle body, the transmission shafts including a speed change shaft and a reduction shaft; A multi-stage speed change device, the multi-stage speed change device comprising: A first transmission mechanism for changing the input power into one of a plurality of speed levels, wherein the first transmission mechanism comprises a plurality of speed change gear sets and a plurality of speed change multi-plate clutches, wherein the plurality of speed change multi-plate clutches are arranged adjacent to each other along the front-rear direction on the speed change shaft and disconnect / connect the transmission relative to the plurality of speed change gear sets; A second speed change mechanism for changing the speed of the power obtained by the first speed change mechanism to a plurality of speeds less than that of the first speed change mechanism, wherein the second speed change mechanism has a plurality of reduction gear sets and a plurality of reduction multi-plate clutches, wherein the plurality of reduction multi-plate clutches are arranged on the reduction shaft and disconnect / connect the transmission relative to the plurality of reduction gear sets; It is characterized in that The transmission shaft further includes an intermediate shaft, which is arranged between the speed change shaft and the reduction shaft, and the speed change multi-plate clutch and the reduction multi-plate clutch are not arranged on the shaft; When viewed from the front of the vehicle body, the intermediate shaft is arranged so as to enter one of the imaginary spaces, with the imaginary line connecting the axis of the speed change shaft and the axis of the reduction shaft as one side and a pair of triangular imaginary spaces formed above and below the imaginary line. The upper side of the multi-plate clutch of the multi-plate clutch type drive switching device configured to switch the transmission state relative to the left and right front wheels by disconnection / connection operation of the multi-plate clutch is arranged to enter the lower space of the pair of upper and lower spaces. A housing protruding downward from the bottom side wall is installed relative to the bottom side wall of the transmission housing which serves as the lower side of the aforementioned drive switching device, and the first output shaft which transmits the driving force from the aforementioned drive switching device to the aforementioned front wheel is supported by the aforementioned housing at a position lower than the aforementioned bottom side wall in a posture along the front-to-rear direction of the aforementioned vehicle body.

2. The transmission for a working vehicle according to claim 1, characterized in that: The plurality of the multi-plate clutches for speed change and the plurality of the multi-plate clutches for speed reduction are arranged adjacent to each other in the left-right direction of the vehicle body; The pair of imaginary spaces are formed above and below between the speed-changing multi-plate clutch and the speed-reducing multi-plate clutch when viewed from the front of the vehicle body.

3. The transmission for a working vehicle according to claim 1 or 2, characterized in that: The radial sizes of the plurality of speed-changing multi-plate clutches and the plurality of speed-reduction multi-plate clutches are set to be the same.

4. A working vehicle, characterized in that: A working vehicle transmission according to claim 1 or 2.

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