JP2007022466A - Working cart - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a trouble wherein transmission of drive force to wheels is interrupted at disengagement of a clutch in gear shifting and traveling performance is impaired, in a working cart having a structure in which an engine, an axle and a stepped transmission for transmitting drive force from the engine to the axle are arranged below a load-carrying platform. <P>SOLUTION: In the working cart 1, the step type transmission 19 is provided with a plurality of shift drive rows; an auxiliary drive row; a main clutch 301 for the plurality of shift drive rows; and a sub-clutch 302 for the auxiliary drive row. The axle 25 is usually driven by one shift drive row selected by turning on the main clutch 301 and the main clutch 301 is turned off so as to select one row from the plurality of shift drive row at shift operation and motive power of the engine 5 is transmitted to the axle 25 through the auxiliary drive row by turning on the sub-clutch 302. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technology of a work transport vehicle provided with an engine, an axle, and a means for transmitting power from the engine to the axle below the loading platform.

2. Description of the Related Art Conventionally, an engine and an axle are disposed below a loading platform, and a transmission mechanism comprising a belt-type continuously variable transmission and a geared type sub-transmission as a means for transmitting driving force from the engine to the axle. Work carrier vehicles are known (see Patent Document 1). The belt-type continuously variable transmission has an advantage that the gear can be continuously shifted without interrupting the power transmission from the engine to the axle.
JP 2000-38042 A

However, the work transport vehicle having the above-described configuration has a drawback peculiar to the belt type. For example, (1) the belt may slip due to adhesion of moisture, (2) the belt has a drawback in durability, and (3) the engine brake is not applied. Furthermore, there are disadvantages such as troublesome operations such as the operation of the auxiliary transmission cannot be performed unless the vehicle is temporarily stopped.
Therefore, in order to eliminate the above-described drawbacks, it is conceivable to replace the combination of a conventional belt-type continuously variable transmission mechanism and a stepped sub-transmission device such as a gear type only with a stepped transmission such as a gear type.
However, in such a transmission, it is necessary to solve the problem that traveling performance is impaired, such as transmission of driving force to the wheels being interrupted when the clutch is disengaged during gear shifting and unexpected movement when shifting on a slope.
An object of the present invention is to provide a work transport vehicle including a stepped transmission that replaces a combination of a conventional belt-type continuously variable transmission and a stepped auxiliary transmission.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

That is, in claim 1,
A work transport vehicle having a structure in which an engine, an axle, and a stepped transmission that transmits driving force from the engine to the axle are disposed below the loading platform, and the stepped transmission includes a plurality of steps. A shift drive train, an auxiliary drive train, a main clutch for the plurality of shift drive trains, and a sub-clutch for the auxiliary drive train are provided. The axle is driven by a drive train, and during the shift operation, the main clutch is disengaged to select one of the plurality of shift drive trains, and the sub-clutch is engaged and the engine is connected via the auxiliary drive train. Provided is a work transportation vehicle characterized in that power is transmitted to the axle.

  According to a second aspect of the present invention, the engine is disposed such that a crankshaft is directed in the longitudinal direction of the fuselage, and in the stepped transmission, transmission from an input portion that receives the output of the engine to an output portion to the axle. Provided is a work transport vehicle characterized in that a shaft extends in the longitudinal direction of the machine body and is arranged in parallel in the lateral direction of the machine body.

  According to a third aspect of the present invention, the stepped transmission includes a plurality of shifter shafts for selecting one shift drive train for the plurality of shift drive trains, and the shifter shafts are arranged in parallel in the horizontal direction. Provided is a work transport vehicle characterized by

  In claim 4, the oil is collected and stored from the case so that the oil level of the oil in the case housing the stepped transmission is lower than a predetermined height when the engine is running. There is provided a work transport vehicle characterized in that a tank that discharges into the case as lubricating oil for the stepped transmission is provided.

  In claim 5, each of the main clutch, the support clutch, and the shifter shaft of the stepped transmission is configured to be hydraulically driven, and the oil stored in the tank is used as the hydraulic oil. Providing a featured work vehicle.

  According to a sixth aspect of the present invention, the amount of oil recovered to the tank increases as the engine speed increases, and the amount of oil recovered to the tank is released into the case as lubricating oil and hydraulic oil. Provided is a work transporter characterized by being larger than the amount of oil.

  According to a seventh aspect of the present invention, there is provided the work transport vehicle, wherein the main clutch also serves as a starting clutch.

  As effects of the present invention, the following effects can be obtained.

  According to the first aspect, in the stepped transmission, the speed change operation can be smoothly performed without interrupting the power transmission from the engine to the axle. That is, the traveling performance at the time of shifting of the work transport vehicle including the stepped transmission can be improved. Moreover, since it is a mechanical gear type transmission, all the faults peculiar to a belt type continuously variable transmission can be eliminated. Furthermore, it can be provided at a low cost.

  According to the second aspect, the vertical width of the transmission case of the transmission can be kept small. Therefore, the transmission can be easily arranged under the loading platform or under the seat without lowering the ground height or without increasing the seat height.

  According to the third aspect, the vertical width of the case of the transmission can be further reduced. Therefore, the transmission can be more easily disposed under the loading platform without lowering the ground clearance.

According to the fourth aspect of the present invention, the oil level of the oil sump in the transmission case can be lowered when the vehicle is traveling. As a result, it is possible to reduce the resistance loss of power that occurs because the gear of the transmission device stirs the oil. Thereby, the speed of the work transport vehicle can be increased. In addition, fuel efficiency is improved.
Further, it is not necessary to separately provide a device for supplying lubricating oil, and the structure can be simplified.

  According to the fifth aspect of the present invention, it is not necessary to separately provide a device for supplying hydraulic oil, and the structure can be simplified.

  According to the sixth aspect of the invention, the oil level of the oil sump in the case is always stabilized at a predetermined position, and the effect of reducing the stirring resistance loss can be obtained.

  In claim 7, since the main clutch also serves as the starting clutch, the structure of the stepped transmission is simplified. Thereby, a stepped transmission can be comprised compactly. In addition, the stepped transmission can be provided at low cost.

Next, embodiments of the invention will be described.
FIG. 1 is a side view showing the overall configuration of a work transport vehicle according to an embodiment of the present invention, and FIG. 2 is a plan view showing the overall configuration of the work transport vehicle according to an embodiment of the present invention. is there.
FIG. 3 is a skeleton diagram showing the configuration of the stepped transmission. FIG. 4 is a sectional front view showing the configuration of the stepped transmission.
FIG. 5 is a sectional front view showing details of the fork control mechanism, and FIG. 6 is a sectional left side view showing details of the fork control mechanism.
FIG. 7 is a diagram showing a hydraulic circuit of the shift control system. FIG. 8 is a diagram showing a shift control flow. FIG. 9 is a diagram showing a shift point characteristic model diagram.
In FIG. 3, the left side of the page is the front side of the vehicle, and the upper side of the page is the right side of the vehicle. 4 and 5, the front side of the paper is the front side of the vehicle, and the left side of the paper is the right side of the vehicle. In FIG. 6, the left side of the paper is the front side of the vehicle, and the front side of the paper is the left side of the vehicle. Unless otherwise specified, front / rear / left / right expressions in this specification are based on the front / rear / left / right direction of the vehicle.

First, the overall configuration of the work transport vehicle 1 according to the present invention will be described with reference to FIGS.
The main body of the work transport vehicle 1 is configured by connecting a front frame 2 and a rear frame 3 back and forth.
The rear frame 3 includes a horizontal floor plate that is substantially rectangular in plan view, and vertical side plates that are erected on the front, rear, left, and right ends of the floor plate. 4 is preferably arranged so as to be rotatable up and down, and the rear frame 3 also serves as a support for the loading platform 4. The front part of the rear frame 3 is lowered and recessed, and a driver seat 9a is mounted on the left and a passenger seat 9b is mounted on the right.

  An engine 5 is disposed in the rear frame 3 below the driver seat 9a and the passenger seat 9b so that the crankshaft is directed in the longitudinal direction of the fuselage. The engine 5 is arranged on the opposite side (right side) with respect to one of the left and right sides (left side) of the driver seat 9a, and thus, the weight can be distributed in the left and right direction of the fuselage. The weight balance is kept good and the running performance can be improved.

  A mission case 8 is disposed in front of the engine 5, and an input shaft 18 projecting rearward from the right rear portion of the mission case 8 has an output shaft 6 projecting forward from the engine 5, It is connected via a flywheel 7 for absorbing vibration.

A stepped transmission 19 comprising a plurality of gear trains is provided in the transmission case 8, and a front output shaft 10 and a rear output shaft 11 project from the front and rear surfaces of the transmission case 8. Thus, the power from the engine 5 input to the input shaft 18 is shifted or reversed by a gear train so as to be output forward and backward from the front output shaft 10 and the rear output shaft 11.
In the work transport vehicle 1 of the present invention, the stepped transmission 19 includes a sub-clutch and an auxiliary drive train for applying auxiliary power to the front and rear wheels during shifting. The stepped transmission 19 will be described in detail later.

  A front wheel drive device 12 and a rear wheel drive device 13 are respectively disposed before and after the mission case 8. An input shaft 17 projects from the front surface of the rear wheel drive device 13, and the input shaft 17 is connected to the rear output shaft 11 via a rear wheel drive shaft 15 that is slightly inclined in the horizontal direction. . An input shaft 16 protruding from the rear surface of the front wheel drive device 12 is connected to the front output shaft 10 substantially straight through a front wheel drive shaft 14.

  In the rear half of the rear frame 3, a vibration isolating rubber is attached to a mounting bracket (not shown) that is raised one step higher than the front half and is extended from the rear frame 3 by the rear wheel drive device 13 at a substantially horizontal center position below the rear half. The rear wheel drive device 13 has a north pin differential type rear wheel differential mechanism 27. In the rear wheel differential mechanism 27, a bevel gear 21 is formed at the rear end of the input shaft 17, and both left and right first are interposed in a differential cage 23 integrated with a bull gear 22 meshing with the bevel gear 21 via a clutch mechanism 24. Axles 25 and 25 are inserted. The first axles 25 and 25 are respectively connected by a universal joint 28 and a transmission shaft 29 to a rear wheel shaft 26a that is a central axis of each rear wheel 26 disposed on the left and right outer sides of the rear half of the rear frame 3. Drive coupled.

  In the clutch mechanism 24, if the rotational speeds of the first axles 25 and 25 are substantially equal, the rotational force of the differential cage 23 is transmitted to both, and the left and right rear wheels 26 and 26 are driven. If there is a difference between the rotational speeds of the first axles 25 and 25, the clutch between the differential cage 23 in the clutch mechanism 24 and the differential output shaft 25 having the higher rotational speed is disengaged. No driving force is applied to the rear wheel 26 on one side that is drivingly connected to 25. As a result, even when one of the rear wheels 26 and 26 slips, the driving force continues to be automatically applied to the other wheels, so there is no need to perform a diff lock operation, and the traction performance does not drop extremely. I am doing so.

  In addition, a stay 3a protrudes outward from the left and right side ends of the rear part of the rear frame 3, and a usual suspension composed of a coil spring, a shock absorber or the like from each stay 3a to each rear wheel shaft 26a. A mechanism 30 is extended, and both the rear wheels 26 are suspended by the suspension mechanism 30.

  In addition, the front wheel drive device 12 is attached to a mounting bracket (not shown) extending from the front frame 2 in the front half of the front frame 2 so as to be one step higher than the rear half of the front frame 2 and at a substantially horizontal center position below the front frame. The front wheel drive device 12 is provided with a front wheel differential mechanism 31 which is disposed via a vibration isolating rubber. In the front wheel differential mechanism 31, a bevel gear 32 is formed at the front end of the input shaft 16, and a side gear fixed on the second axles 36 and 36 in a differential cage 34 integrated with a bull gear 33 that meshes with the bevel gear 32. The left and right second axles 36 and 36 are fitted via a bevel gear mechanism 35 constituted by a bevel pinion meshing with both gears. The second axles 36 and 36 are respectively connected to a universal joint 38 and a transmission with respect to a front wheel shaft 37a that is a central axis of each front wheel 37 that is steerable on the left and right outer sides of the front half of the front frame 2. The shaft 39 is drivingly connected.

  In this bevel gear mechanism 35, if the loads from the ground acting on both second axles 36, 36 are substantially equal, the rotational force of the differential cage 34 is transmitted to both, and the left and right front wheels 37, 37 are driven, Differential rotation is performed according to the load applied to both the second axles 36 and 36. An LSD (Limited Slip Differential) mechanism is attached so that the rotation of the axle with the larger load is transmitted to the axle with the smaller load when the difference between the loads on the second axles 36 and 36 exceeds a predetermined value. ing. Thereby, the rotational speed difference can be appropriately controlled, and the turning performance can be improved and the left and right wheels can be controlled to rotate appropriately for the road surface. Further, since the central differential mechanism 101 and the second axles 36 and 36, which will be described later, are mechanically connected, the engine brake can be reliably applied to the second axles 36 and 36.

  In addition, a stay 2a protrudes outward from the left and right side ends of the front portion of the front frame 2, and is usually configured by a coil spring, a shock absorber, or the like from each stay 2a to each front wheel shaft 37a. The suspension mechanism 40 is extended, and the front wheels 37 are suspended by the suspension mechanism 40.

  Further, a front cover 2b is erected on the front half of the front frame 2, the rear upper end is an operation / instrument panel, and a round handle 41 is disposed above the front cover 2b. On the rear part of the rear end of the front cover 2b, a tread board is laid to form a horizontal platform 2c, and the platform 2c extends to the left and right outer sides.

Next, the stepped transmission 19 including the sub-clutch 302 and the auxiliary drive train, which are features of the work transport vehicle of the present invention, will be described.
In the present embodiment, the stepped transmission 19 is configured as a three-stage automatic transmission.
As shown in FIG. 3, the stepped transmission 19 includes a plurality of speed change drive trains for first to third speeds and reverse, an auxiliary drive train, and a main clutch 301 for the plurality of speed change drive trains. And a sub-clutch 302 for the auxiliary drive train, and the axles 65 and 76 are driven by a single shift drive train selected with the main clutch 301 in the normal state. The main clutch 301 is disengaged to select one from a plurality of shift drive trains, and the sub-clutch 302 is engaged to transmit the power of the engine 5 to the axles 65 and 76 via the auxiliary drive train.

The configuration of the stepped transmission 19 will be further described in detail.
As shown in FIG. 3, the transmission 19 includes auxiliary power to the travel output shaft 316 during a shift in addition to the main clutch 301 and the shift drive train for transmitting power from the input shaft 18 to the travel output shaft 316 during normal travel. A sub-clutch 302 and an auxiliary drive train are provided.
As described above, in the work transport vehicle 1 of the present invention, the engine 5 is disposed such that the crankshaft is directed in the longitudinal direction of the machine body. In the stepped transmission 19, the transmission shaft from the input unit that receives the output of the engine 5 to the output unit to the axles 65 and 76 extends in the longitudinal direction of the vehicle body and is arranged in parallel in the lateral direction of the vehicle body. . Specifically, in the transmission case 19 of the stepped transmission 19, the input shaft 18, the clutch input shaft 303, the intermediate shaft 308, the travel transmission shaft 311, the travel output shaft 316, in order from the input unit to the output unit. The front and rear wheel drive force take-out shafts 346 and 11 are spanned in parallel in the longitudinal direction of the machine body.

  As shown in FIGS. 3 and 4, the output shaft 6 of the engine 5 is directly connected to the input shaft 18 of the transmission 19 via the flywheel 7. A gear 304 is fixed on the input shaft 18 so as not to be relatively rotatable. The front end portion of the input shaft 18 projects forward of the case 8 and serves as a drive shaft for pumps 213 and 214 described later.

  A main clutch 301 and a sub-clutch 302 that are integrally coupled to the front of the main clutch 301 are disposed above the input shaft 18. Both clutches 301 and 302 are preferably wet multi-plate clutches, and share a single clutch input shaft 303, and each clutch housing is fixed to the shaft 303. A gear 305 is fixed on the clutch input shaft 303 so as not to be relatively rotatable, and the gear 305 and the gear 304 of the input shaft 18 are engaged with each other. Power is transmitted from the input shaft 18 to the clutch input shaft 303 via both gears 304 and 305.

First, power transmission from the main clutch 301 through the speed change drive train during normal travel will be described.
A cylindrical main clutch output shaft 306 extends rearward of the main clutch 301. The main clutch output shaft 306 is fitted on the clutch input shaft 303 so as to be relatively rotatable. A gear 307 is fixed on the main clutch output shaft 306 so as not to be relatively rotatable. A multi-plate hydraulic clutch device is interposed between the main clutch output shaft 306 and the clutch housing.

  An intermediate shaft 308 is provided on the left side of the clutch input shaft 303. A gear 309 is fixed to the intermediate shaft 308 so as to be relatively non-rotatable toward the center rear side, and meshes with the gear 307 of the main clutch output shaft 306. A gear 310 for transmitting power to a travel transmission shaft 311 described below is fixed to the rear end portion of the intermediate shaft 308 so as not to be relatively rotatable.

The travel transmission shaft 311 is provided on the upper left side of the intermediate shaft 308. A third speed drive gear 312 is fixed to the rear end portion of the travel transmission shaft 311 so as not to be relatively rotatable. The third-speed drive gear 312 also serves as a power input gear for the travel transmission shaft 311 and meshes with the gear 310 for the intermediate shaft 308. As described above, power is transmitted from the main clutch output shaft 306 to the travel transmission shaft 311 via the gears 307, 309, and 310 and the third speed drive gear 312.
The third speed drive gear 312, the second speed drive gear 313, the first speed drive gear 314, and the reverse drive gear 315 are not rotatable relative to the traveling transmission shaft 311 in order from the rear end to the front. Is fixed.

  A travel output shaft 316 is provided on the lower right side of the travel transmission shaft 311. A third-speed driven gear 317, a second-speed driven gear 318, a first-speed driven gear 319, and a reverse driven gear are provided on the traveling output shaft 316 in order from the rear end portion toward the front. A gear 320 is externally fitted so as to be relatively rotatable. The first to third driven gears 319, 318, and 317 mesh with the first to third driving gears 314, 313, and 312 of the traveling transmission shaft 311, respectively. The reverse driven gear 320 meshes with the reverse drive gear 315 via the reverse gear 323.

  On the traveling output shaft 316, a first shifter 324 is provided between the reverse driven gear 320 and the first speed driven gear 319. A first fork 325 is engaged with the first shifter 324. The first shifter 324 is controlled by the first fork 325 to take three positions along the travel output shaft 316, that is, a reverse position (front side), a neutral position (center), and a first speed position (rear side) (see FIG. 5, see FIG. When the first shifter 324 is in the reverse drive position, the reverse drive gear 320 is coupled to the travel output shaft 316 through the synchronizer and the first spline hub 336 so as not to be relatively rotatable. When the first shifter 324 is in the first speed position, the first speed driven gear 319 is coupled to the travel output shaft 316 via the synchronizer and the first spline hub 336 so as not to be relatively rotatable. When the first shifter 324 is in the neutral position, the traveling output shaft 316 is not coupled to either of the gears 319 and 320.

Similarly, a second shifter 326 is provided between the second speed driven gear 318 and the third speed driven gear 317. A second fork 327 is engaged with the second shifter 326. The second shifter 326 is controlled by the second fork 327 to take three positions along the travel output shaft 316, that is, a second speed position (front side), a neutral position (center), and a third speed position (rear side). (See FIGS. 5 and 6). When the second shifter 326 is in the second speed position, the second speed driven gear 318 is coupled to the travel output shaft 316 through the synchronizer and the second spline hub 337 so as not to be relatively rotatable. When the second shifter 326 is in the third speed position, the third speed driven gear 317 is coupled to the travel output shaft 316 via the second spline hub 337 so as not to be relatively rotatable. When the second shifter 326 is in the neutral position, the traveling output shaft 316 is not coupled to either of the gears 317 and 318.
When the vehicle is traveling, any one of the first to third driven gears 319, 318, and 317 and the reverse driven gear 320 is selected by the first and second forks 325 and 327, and the spline hubs 336 and 337 are selected. It is connected to the travel output shaft 316 through a non-rotatable connection.

  On the traveling output shaft 316, in front of the reverse driven gear 320, a gear 322 for transmitting power to a driven gear 321 of an auxiliary drive train (to be described later) and a bull gear 343 of the central differential mechanism 342 is relatively rotated. It is fixedly impossible. The rotation output of the travel output shaft 316 is transmitted to the bull gear 343 of the central differential mechanism 342 via the gear 322. Power is appropriately distributed from the bull gear 343 via the bevel gear 344 for driving the front and rear wheels. The rear output shaft of the central differential mechanism 342 protrudes rearward of the transmission case 8 as a rear wheel drive force extraction shaft (rear output shaft) 11 and is directly connected to the rear wheel drive shaft 15 via the universal joint 20. ing. On the other hand, the forward output shaft of the central differential mechanism 342 projects into the front wheel drive gear case 348 as a front wheel drive force take-out shaft 346. The power of the front wheel drive force extraction shaft 346 is transmitted to the front output shaft 10 disposed in the front-rear direction from the left and right center of the mission case 8 via the gear train. The front output shaft 10 projects forward from the front wheel drive gear case 348 and is connected to the front wheel drive shaft 14 via the universal joint 20.

Next, power transmission from the sub-clutch 302 via the auxiliary drive train will be described.
The sub-clutch 302 is used to continuously give power to the travel output shaft 316 without interruption during a shift operation, and is connected only while power transmission from the main clutch 301 is interrupted. Therefore, compared to the main clutch 301, the multi-plate hydraulic clutch device capable of slipping is reduced in consideration of the number of friction plates and the piston diameter.

With reference to FIG. 3, as described above, the sub-clutch 302 is integrally disposed in front of the main clutch 301 and shares the clutch input shaft 303 with the main clutch 301.
A cylindrical sub-clutch output shaft 330 extends forward of the sub-clutch 302. The sub-clutch output shaft 330 is fitted on the clutch input shaft 303 so as to be relatively rotatable. A gear 331 is fixed on the sub-clutch output shaft 330 so as not to be relatively rotatable. The gear 331 is engaged with a large gear 333 of a two-stage gear 332 that is externally fitted to the intermediate shaft 308 so as to be relatively rotatable. . The small gear 334 of the two-stage gear 332 meshes with a relay gear 335 that is externally fitted to the travel transmission shaft 311 so as to be relatively rotatable. The relay gear 335 also meshes with the driven gear 321 fixed on the travel output shaft 316 so as not to be relatively rotatable. As described above, the output from the sub-clutch output shaft 330 is transmitted to the travel output shaft 316 via the gear 331, the second gear 332, the gear 335, and the driven gear 321. The auxiliary drive train is configured as described above.
In the present embodiment, the reduction ratio in the auxiliary drive train is set to correspond to about the third speed, which is the highest speed stage in the shift drive train.

A control mechanism for the main clutch 301 and the sub-clutch 302 will be described.
The main clutch 301 and the sub-clutch 302 are connected / disconnected by a first hydraulic actuator 271 and a second hydraulic actuator 272 shown in the control system hydraulic circuit diagram of FIG.
The hydraulic oil is supplied to and discharged from the first hydraulic actuator 271 for the main clutch 301 by an electromagnetic proportional pressure reducing valve 273. The electromagnetic proportional pressure reducing valve 273 can be completely inserted by continuously changing the operating pressure of the oil supplied to the first hydraulic actuator 271 from zero to the maximum clutch operating pressure set by the relief valve 298. On the other hand, since hydraulic oil is supplied to and discharged from the second hydraulic actuator 272 for the sub-clutch 302 by an ordinary electromagnetic switching valve 274, the operating pressure is switched to either zero or the maximum clutch operating pressure. However, when the maximum clutch operating pressure is supplied to the sub-clutch 302, the sub-clutch 302 is set to a smaller capacity than the main clutch 301 as described above, and therefore slips without being completely engaged.

  In the control system hydraulic circuit, the oil in the oil reservoir of the transmission case 8 is supplied to the pump 214 as hydraulic oil for actuators 271 and 272 and cylinders 230 and 231 described later. A hydraulic circuit for a clutch control system and a shift control system, which will be described later, is provided in parallel to the pump 214. The operating pressure in the clutch control and shift control system is set by a relief valve 298. The downstream side of the relief valve 298 further leads to a lubricating oil passage, and surplus oil is supplied as lubricating oil. The pressure in the lubricating oil passage is set by a relief valve 299. Lubricating oil is supplied to the first and second actuators 271 and 272 via an oil passage 295 in the lubricating oil passage. Lubricating oil is also supplied to the geared drive train, auxiliary drive train, and other parts to be lubricated, which are represented by the component 297.

Next, the control mechanism of the first and second forks 325 and 327 will be described.
Referring to FIGS. 5 and 6, as described above, the first and second forks 325 and 327 engage with the first and second shifters 324 and 326 for selecting the shift drive train to be used, respectively. The shifters 324 and 326 are moved. As shown in FIG. 5, the first and second forks 325 and 327 have fork-like engaging portions at the lower portions, and the engaging portions are grooves (not shown) of the first and second shifters 326 and 326, respectively. ).
The first fork 325 and the second fork 327 are fixed to a first shifter shaft 221 and a second shifter shaft 222 disposed in the front-rear direction above the travel output shaft 316. The first shifter shaft 221 and the second shifter shaft 222 are arranged side by side at the same height. The shifter shafts 221 and 222 can be slid in the axial direction (front-rear direction).

Here, as shown in FIG. 6, the second shifter shaft 222 is inserted and supported so as to be slidable in the axial direction in bearing holes provided in front and rear inner walls of the mission case 8. Along the outer periphery of the rear end portion of the second shifter shaft 222, annular grooves 226a, 226b, and 226c for positioning the second speed position, the neutral position, and the third speed position are formed in order from the rear. The grooves 226a, 226b, and 226c communicate with a lower portion of a hole 229 that is perforated upward from the lower surface of the rear wall, and a biasing spring 228 and a detent ball 227 are provided in the hole 229. The detent sphere 227 is inserted so that the tip of the detent ball 227 faces the grooves 226a, 226b, and 226c, thereby forming a detent mechanism.
As a result, the detent ball 227 is constantly pressed toward the grooves 226a, 226b, and 226c by the biasing spring 228. Therefore, when the second shifter shaft 222 is slid in the longitudinal direction of the machine body and moved to a predetermined shift position. Since the detent ball 227 is locked in any one of the grooves 226a, 226b, and 226c, the second shifter shaft 222 can be reliably held at the predetermined shift position without being displaced after the movement. The first shifter shaft 221 is also provided with the same detent mechanism for positioning the reverse position, the neutral position, and the first speed position.

As shown in FIGS. 5 and 6, the first and second forks 325 and 327 (first and second shifters 324 and 326) are controlled by a fork control mechanism using two hydraulic cylinders 230 and 231 as drive sources. Is done.
In the fork control mechanism, the cylinder 231 is operated to select either the first shifter shaft 221 or the second shifter shaft 222, and the cylinder 230 is operated to slide the selected shifter shafts 221 and 222. Accordingly, the positions of the forks 325 and 327 (shifters 324 and 326) on the selected shifter shafts 221 and 222 are moved. That is, when the first shifter shaft 221 is selected, the position of the first fork 325 (first shifter 324) is controlled to move to any one of the reverse position, the neutral position, and the first speed position. When the second shifter shaft 222 is selected, the position of the second fork 327 (second shifter 326) is controlled to move to any one of the second speed position, the neutral position, and the third speed position.

The fork control mechanism will be described in further detail.
As shown in FIGS. 5 and 6, the hydraulic cylinders 230 and 231 are provided inside the shifter case 238 installed so as to block the upper wall opening of the transmission case 8 above the first and second shifter shafts 221 and 222. Yes. The cylinder 231 is a drive mechanism of a selector mechanism that selects a fork to be moved from the first fork 325 and the second fork 327. The cylinder 230 is a drive source of a shift mechanism that slides the first and second shifter shafts 221 and 222 back and forth to move the first and second forks 325 and 327 back and forth.

First, a selector mechanism for selecting a fork to be moved and controlled will be described with reference to FIG.
The hydraulic cylinder 231 has a rod 231a that extends horizontally leftward (rightward in the drawing). The cylinder 231 is configured so that the tip position of the rod 231a is controlled in two stages, that is, the rear position and the front position of the illustrated position by an electromagnetic switching valve 255 (see FIG. 7). And). An engaging member 232 is fitted and fixed to the tip of the rod 231a. The engaging member 232 has a substantially spherical engaging ball portion 232a at the bottom.

As shown in FIGS. 5 and 6, a fork control shaft 240 is provided below the cylinder 231. The fork control shaft 240 is disposed in the left-right direction, that is, in parallel with the rod 231a, and is supported by the support legs 239a and 239b at both ends thereof so as to be slidable in the axial direction.
A lever 241 is fixed on the fork control shaft 240. The lever 241 is externally fitted and fixed at the fixing portion 241c so as not to rotate relative to the fork control shaft 240 and to move in the axial direction. An engagement recess 241a that is open upward and frontward and rearward is provided on the upper portion of the lever 241, and the engagement ball portion 232a of the engagement member 232 is engaged with the engagement recess 241a. Further, a substantially spherical engagement ball portion 241b is provided at the lower end portion of the lever 241.

As shown in FIGS. 5 and 6, an engaging member 224 is fixed on the second shifter shaft 222 in front of the second fork 327. The engaging member 224 is externally fitted and fixed at the fixing portion 224b so as not to rotate relative to the second shifter shaft 222 and to move back and forth. An engaging portion 224a is formed on the fixed portion 224b. The engaging portion 224a is formed with an engaging concave portion 224c opened upward and leftward. In the state shown in FIG. 5, the engaging ball portion 241b of the lever 241 is engaged with the engaging concave portion 224c. ing.
Further, as shown in FIG. 5, a similar engaging member 223 is also fixed on the first shifter shaft 221 in front of the first fork 325. The engaging member 223 is disposed adjacent to the left side of the engaging member 224 of the second shifter shaft 222. The engagement member 223 is configured to be bilaterally symmetrical with the engagement member 224, and the engagement recess 223c of the engagement portion 223a is opened upward and rightward. As a result, when both shifter shafts 221 and 222 are in the neutral position as shown in FIG. 5, the right opening surface of the engaging recess 223c faces the left opening surface of the engaging recess 224c. .

  5 and 6, both shifter shafts 221 and 222 are in a neutral position, and the vertically open surfaces of the engaging recesses 223c and 224c face each other. In this state, the engaging ball portion 241b of the lever 241 can move between the engaging concave portions 223c and 224c. Accordingly, the engaging ball portion 241b below the lever 241 is selectively engaged with either the engaging recess 223c on the first shifter shaft 221 side or the engaging recess 224c on the second shifter shaft 222 side.

5 and 6, the tip of the rod 231a of the cylinder 231 is in the rear position, and the engagement ball portion 241b of the lever 241 is engaged with the engagement recess 224c on the second shifter shaft 222 side. . When the tip of the rod 231a is moved from this state to the front position, the engaging member 232 pushes the lever 241 to the left and the fork control shaft 240 slides to the left. As a result, the engagement ball portion 241b of the lever 241 moves from the engagement recess 224c to the engagement recess 223c on the first shifter shaft 221 side.
The shifter shafts 221 and 222 to be moved are selected by the above mechanism.

Next, fork position shift control will be described.
With reference to FIGS. 5 and 6, as described above, the position movement of the first and second forks 325 and 327 is performed by a mechanism using the hydraulic cylinder 230 as a drive source. The hydraulic cylinder 230 is configured such that the tip position of the rod 230a is controlled in three stages, front, middle, and rear, by electromagnetic switching valves 251 and 252 (see FIG. 7). To do).

  An engagement pin 230b penetrating in the horizontal direction is provided at the tip of the rod 230a, and a rotation lever 242 for controlling the rotation of the fork control shaft 240 is engaged with the engagement pin 230b. The rotation lever 242 is splined to the fork control shaft 240 at the lower portion, and the expansion / contraction operation of the rod 230a is transmitted to the fork control shaft 240 as a rotation operation around the axis via the rotation lever 242.

For example, the operation when the rod 230a is controlled to move to the front position from the state shown in FIGS. 5 and 6 will be described.
As described above, in FIGS. 5 and 6, the second shifter shaft 222 is selected to be controlled by the lever 241. The rod 230a of the cylinder 230 is in the neutral position, and the position of the second fork 327 is in the neutral position.
If the electromagnetic switching valves 251 and 252 (see FIG. 7) are controlled from this state to move the tip of the rod 230a to the front position, the fork control shaft 240 rotates counterclockwise as viewed from the left side via the rotation lever 242. At the same time, the lever 241 fixed to the fork control shaft 240 rotates in the same direction. Then, the engaging ball part 241b below the lever 241 pushes the engaging member 224 of the second shifter shaft 222 backward from the inside of the engaging part 224a. As a result, the second fork 327 (second shifter 326) moves to the third speed position, and the third speed driven gear 317 is coupled to the travel output shaft 316 via the second spline hub 337 in a relatively non-rotatable manner. .
Conversely, when the rod 230a is moved from the middle position to the rear position, the second shifter shaft 222 is pushed forward. As a result, the second fork 327 (second shifter 326) moves to the second speed position, and the second speed driven gear 318 cannot be rotated relative to the travel output shaft 316 via the synchronizer and the second spline hub 337. Combined.

  When the first shifter shaft 221 is selected to be controlled by the lever 241, when the rod 230a is controlled to move to the front position, the first fork 325 (first shifter 324) is The first shift gear 319 is pushed rearward together with the shifter shaft 221 to move to the first speed position, and the first speed driven gear 319 is coupled to the travel output shaft 316 via the first spline hub 336 in a relatively non-rotatable manner. When the rod 230a is controlled to move to the rear position, the first fork 325 (first shifter 324) is pushed forward together with the first shifter shaft 221 to move to the reverse position, and the reverse driven gear 320 is moved to the first spline. It is coupled to the travel output shaft 316 via the hub 336 so as not to be relatively rotatable.

Here, the configuration and control method of the hydraulic cylinders 230 and 231 will be described in detail.
First, the configuration of a three-position hydraulic cylinder 230 for moving the fork position will be described with reference to FIG.
The cylinder 230 formed in the shift case 238 has a first chamber 230c at the rear and a second chamber 230d having a smaller diameter than the first chamber 230c at the front. A shoulder 230e is formed at the boundary between the first chamber 230c and the second chamber 230d due to the difference in diameter between the two chambers.
The cylinder 230 has a first piston 230f and a second piston 230g. The first piston 230f is configured in a return shape. The second piston 230g includes a front large-diameter portion 230h and a rear small-diameter portion 230i.
A first piston 230f is fitted in the first chamber 230c so as to be able to slide back and forth in a close contact state. The large diameter portion 230h of the second piston 230g is fitted into the second chamber 230d so as to be slidable back and forth. The small diameter portion 230i of the second piston 230g is fitted in the hole of the first piston 230f so as to be slidable back and forth. The rod 230a extends from the front end surface of the second piston 230g.

In the first chamber 230c, a first oil chamber 230m filled with oil is formed behind the first piston 230f. Further, in the second chamber 230d, a second oil chamber 230n filled with oil is formed in front of the second piston 230g.
A hydraulic oil supply / discharge port 230j is provided in the upper portion of the rear end of the side wall of the first chamber 230c, and the first oil chamber 230m is electromagnetically connected through an oil passage formed in the supply / discharge port 230j and the oil passage plate 238a. The switching valve 251 is fluidly connected. The first oil chamber 230m is switched to the control pressure or drain pressure set by the relief valve 298 by the electromagnetic switching valve 251 (see FIG. 7).
A supply / discharge port 230k is provided in the upper portion of the front end of the side wall of the second chamber 230d, and the second oil chamber 230n is connected to the electromagnetic switching valve 252 through an oil passage formed in the supply / discharge port 230k and the oil passage plate 238a. Fluid connection. Similarly to the first oil chamber 230m, the second oil chamber 230n is switched to the control pressure or the drain pressure by the electromagnetic switching valve 252 (see FIG. 7).
In addition, a supply / discharge port 230l that leads to an oil sump of the transmission case 8 through an oil passage formed in the oil passage plate 238a is provided at the upper side wall of the shoulder portion 230e. (Drain pressure) is maintained.
The oil passage plate 238a is a plate-like member that is installed on and coupled to the upper surface of the shift case 238. The oil passage plate 238 has a plurality of grooves formed on the coupling surface with the shift case 238. When the oil passage plate 238a is coupled to the shift case 238, the open surface of the groove is closed, the groove forms a tubular oil passage, and the electromagnetic switching valves 251, 252, and 255 installed on the upper surface thereof are hydraulically connected. Oil is supplied to and discharged from the cylinders 230 and 231.

  In the state where the first oil chamber 230m is set to a high pressure (control pressure) and the second oil chamber 230n is set to a low pressure (drain pressure) by the electromagnetic switching valves 251 and 252, the rod 230a is controlled to the front position. In a state where the first oil chamber 230m is at a low pressure (drain pressure) and the second oil chamber 230n is at a high pressure (control pressure), the rod 230a is controlled to the rear position. In a state where both the first oil chamber 230m and the second oil chamber 230n are at a high pressure (control pressure), the rod 230a is controlled to the middle position.

The operation of the cylinder 230 will be described in detail. In a state where the first oil chamber 230m is at a high pressure (control pressure) and the second oil chamber 230n is at a low pressure (drain pressure), the small diameter portion 230i of the second piston 230g is the first. The force pushed forward by the oil in the oil chamber 230m exceeds the force pushed rearward by the oil in the second oil chamber 230n, and the second piston 230g is pressed against the front end of the cylinder. Therefore, the rod 230a is in the front position. The first piston 230f is pressed against the shoulder 230e and stopped.
Conversely, in a state where the first oil chamber 230m is at a low pressure and the second oil chamber 230n is at a high pressure, the force with which the large-diameter portion 230h of the second piston 230g is pushed backward by the oil in the second oil chamber 230n is The small diameter portion 230i of the piston 230f and the second piston 230g exceeds the force pushed forward by the oil in the first oil chamber 230m, and the first piston 230f and the second piston 230g are both pressed against the rear end of the cylinder. Therefore, the rod 230a is in the rear position.

  In a state where both the first oil chamber 230m and the second oil chamber 230n are at the same high pressure, a force pushed forward by the oil in the first oil chamber 230m acts on the first piston 230f. On the other hand, the force pushed forward and backward by the oil in the first oil chamber 230m and the second oil chamber 230n is applied to the second piston 230g, but the resultant pressure is rearward because the pressure receiving area on the large diameter portion 230h side is larger. The second piston 230g is pushed backward. Here, in the cylinder 230, the pressure receiving area of the first piston 230f is greater than the total pressure receiving area of the second piston 230g (the area obtained by subtracting the pressure receiving area on the first oil chamber 230m side from the pressure receiving area on the second chamber side 230d). Therefore, the force that pushes the first piston 230f forward is larger than the resultant force that the second piston 230g pushes backward. Therefore, the first piston 230f is pressed against the shoulder 230e and stopped, while the second piston 230g cannot move by pushing the first piston 230f backward, and is also stopped at the shoulder 230e. . Therefore, the rod 230a is stopped at the middle position.

Next, the fork selection hydraulic cylinder 231 will be described with reference to FIG.
The cylinder 231 is an ordinary two-position cylinder. A piston 231c is fitted in a cylindrical cylinder chamber 231b so as to be slidable in the front-rear direction. The rod 231a extends from the front end surface of the piston 231c.
In the cylinder chamber 231b, a first oil chamber 231d filled with oil is formed behind the piston 231c. A second oil chamber 231e filled with oil is formed in front of the piston 231c.
As shown in FIG. 7, hydraulic oil supply / discharge ports 231f and 231g are provided at the rear end and upper front end of the cylinder chamber 231b, respectively. The supply / discharge port 231g on the front end side is directly connected to the main hydraulic oil supply oil passage from the pump through an oil passage formed in the oil passage plate 238, and the second oil chamber 231e is always set by the relief valve 298. The control pressure is maintained. On the other hand, the first oil chamber 231d is fluidly connected to the electromagnetic switching valve 255 via an oil passage formed in the supply / discharge port 231f and the oil passage plate 238. The electromagnetic switching valve 255 can switch the pressure in the second oil chamber 231e to high pressure (control pressure) or low pressure (drain pressure).
Referring to FIG. 5, in piston 231c, the first oil chamber 231d side has a larger pressure receiving area than the second oil chamber 231e side. Therefore, in a state where the first oil chamber 231d is at a high pressure, that is, in a state where the pressure is the same as that of the second chamber 231e, the piston 231c is pressed against the front end of the cylinder. Therefore, the rod 231a is in the front position. On the other hand, when the first oil chamber 231d is at a low pressure, the piston 231c is pressed against the rear end of the cylinder. Therefore, the rod 231a is in the rear position.

Next, details of the automatic transmission control of the stepped transmission 19 will be described.
In the stepped transmission 19 according to the present invention, automatic shifting is performed in relation to the amount of depression of an accelerator pedal (not shown) and the vehicle speed at that time, and a shift command is automatically issued from the centralized control device, All hydraulic control valves that control the main clutch 301, the sub-clutch 302, and the first and second forks 325 and 327 are controlled at an optimal timing. When the engine is started, all the selector valves 251, 252 and 255 are in the non-excited positions as shown in the figure, so that the selector mechanism is in the state where the shifter shaft 222 is selected, but the shifter shaft 222 is held in the neutral position by the shift mechanism Is done.
A command for upshifting or downshifting between the respective gears is issued based on a shift point characteristic model diagram as shown in FIG. 9, and a vehicle speed and a throttle opening detected by the vehicle speed sensor and the throttle sensor, respectively. That is, the centralized control device determines a shift stage to be used by determining which region of the shift point characteristic model diagram is based on the detected vehicle speed, the rate of change thereof, and the throttle opening. When the vehicle speed and the throttle opening change so as to cross the region boundary line, a shift command is issued by recognizing that the shift stage to be used has changed. Note that the region boundary line is set such that the throttle opening gradually increases with increasing vehicle speed when the vehicle speed is increased than when the vehicle is decelerated. Further, the throttle opening is set to gradually increase as the vehicle speed increases as the gear speed increases.

With reference to FIG. 8, the control flow at the time of shifting will be described. For example, the operation when the shift command from the first speed to the second speed is issued by depressing the accelerator pedal will be described.
First, referring to FIG. 3, during traveling at the first speed, the main clutch 301 is connected and the sub-clutch 302 is disconnected. The first fork 325 is in the first speed position on the rear side, and the travel output shaft 316 is coupled to the first speed driven gear 319 to transmit power. On the other hand, the second fork 327 (second shifter 326) is in the neutral position.
Referring to FIG. 8, when the vehicle speed increases and a command to shift to the second speed is issued at timing A, the electromagnetic proportional pressure reducing valve 273 is switched and the main clutch 301 is disconnected. Under control, the sub-clutch 302 is connected. As a result, power transmission from the main clutch 301 to the transmission drive train is cut off, and power transmission from the sub-clutch 302 to the auxiliary drive train is started instead.

  As described above, since the gear ratio by the auxiliary drive train from the sub-clutch output shaft 330 to the travel output shaft 316 is set to about the third speed of the shift drive train, the shift from the first speed to the second speed is performed. , There is a difference in the rotational speed between the sub-clutch output shaft 330 and the clutch input shaft 303 (the sub-clutch output shaft 330 rotates more slowly). However, since the capacity of the sub-clutch 302 is set smaller than that of the main clutch 301 for an auxiliary purpose, the clutch plate slips and the sub-clutch output shaft 330 and the clutch input shaft 303 are completely synchronized. It does not lead to rotation. That is, the sub-clutch 302 and the auxiliary drive train play a role of continuously providing auxiliary power to the travel output shaft 316 to the extent that the travel performance is not impaired while the main clutch 301 is disengaged.

  Referring to FIG. 8, the driven gear 319 at the current gear position (first speed) is next disconnected from the travel output shaft 316 at a timing B at which the clutch engagement / disengagement operation is completed after a lapse of the gear shift command. A command is issued (see FIG. 3). That is, referring to FIG. 7, the electromagnetic switching valves 251 and 252 are switched, and the rod 230a is moved to the middle position. Thus, the first fork 325 (first shifter 324) is moved from the first speed position to the neutral position, and the first speed driven gear 319 is disconnected from the travel output shaft 316.

Referring to FIG. 8, at timing C at which first-speed driven gear 319 is completely disconnected, next, a command for coupling driven gear 318 of the next gear stage (second speed) to traveling output shaft 316 is issued. (See FIG. 3). That is, referring to FIG. 7, first, the electromagnetic switching valve 255 is controlled to be switched, and the rod 231a of the cylinder 231 is pulled from the front position to the rear position. As a result, as shown in FIG. 5, the engaging ball portion 241b of the lever 241 moves from the engaging concave portion 223c on the first fork 325 side to the engaging concave portion 224c on the second fork 327 side.
Referring to FIG. 7, next, the electromagnetic switching valves 251 and 252 are controlled to be pushed, and the rod 230a of the cylinder 230 is pushed out from the middle position to the front position. As a result, the second fork 327 (second shifter 326) is moved from the neutral position to the second speed position, and the second speed driven gear 318 is coupled to the travel output shaft 316 in a relatively non-rotatable manner.
During this time, the sub-clutch 302 continues to provide auxiliary power to the travel output shaft 316.

By the way, referring to FIG. 8, as described above, a connection command for the main clutch 301 is issued at a timing D which is a short time after the movement command for the second fork 327 is issued. The main clutch 301 is controlled by the electromagnetic proportional pressure reducing valve 273 so as to gradually increase the clutch pressure.
Then, at timing E when the clutch pressure of the main clutch 301 substantially reaches the clutch pressure of the sub-clutch 302, the electromagnetic switching valve 274 is controlled to be disconnected and the sub-clutch 302 is disconnected. Thereby, the power transmission from the sub-clutch 302 via the auxiliary drive train is completely switched from the main clutch 301 to the power transmission via the shift drive train.
The main clutch 301 increases the clutch pressure as it is, and at the timing F when the maximum clutch pressure is reached, the second fork 327 (second shifter 327) is also moved to the second speed position, and the shift control is completed.
Switching control between the other shift speeds is also performed in the same process as described above. However, in the shift control between the second speed and the third speed, the movement of the lever 241 is not necessary, so the cylinder 231 is not controlled.

As described above, the automatic gear shift control using the sub-clutch 302 and the auxiliary drive train achieves a smooth gear shifting operation without interruption of power transmission in the mechanical gear type stepped transmission 19.
In the stepped transmission 19 of this embodiment, the main clutch 301 also serves as a starting clutch.

As described above, in the work transport vehicle according to the present embodiment, the engine 5 is arranged so that the output shaft 6 faces in the longitudinal direction of the machine body, and the stepped transmission 19 receives the output of the engine 5. The transmission shaft from the input part to the output part to the axles 25 and 36 extends in the longitudinal direction of the machine body and is arranged in parallel in the lateral direction of the machine body. Thereby, it is possible to configure the mission case 8 with a small vertical width.
Further, as described above, since the two shifter shafts 221 and 222 are provided horizontally, the vertical width of the mission case 8 can be further suppressed.

Next, the tank 201 and the partition wall 203 for reducing the stirring resistance loss provided in the stepped transmission 19 of this embodiment will be described.
As shown in FIG. 4, in the work transport vehicle 1 according to the present embodiment, the stepped transmission 19 is housed in order to reduce the resistance loss of power caused by stirring the oil accumulated in the oil sump. The oil is collected and stored from the case 8 so that the oil level of the oil in the mission case 8 is lower than a predetermined height when the engine 5 is operated, and this stored oil is used as lubricating oil for the stepped transmission 19. 8 is provided with a tank 201 for discharging into the tank 8.

More specifically, as shown in FIG. 4, the bottom of the transmission case 8 is an oil reservoir in which lubricating oil and hydraulic oil leaking from the speed change drive train, cylinders and the like are accumulated along the walls.
When the vehicle travels, the oil accumulated in the oil sump is temporarily forcibly discharged from the discharge port 210 with a strainer to the outside of the case 2 by the pump 213 in which the input shaft 18 of the transmission 19 also serves as a pump input shaft. The discharged oil is guided and stored in the tank 201 built in the right end inside the mission case 8 via the hydraulic pipe 211, the pump 213, and the hydraulic pipe 212. The upper end of the tank 201 is open, and is configured to fall into the oil reservoir when the stored oil overflows.

  The oil stored in the tank 201 is discharged from the tank discharge port 219 via the oil filter 220 by the pump 214 in which the input shaft 18 of the mission case 8 also serves as the pump input shaft, similarly to the pump 213. The discharged oil is discharged again into the case 2 as lubricating oil through the hydraulic pipe 215 and the pump 214. Further, a part of the oil stored in the tank 201 is also used as hydraulic oil for the shift actuator control valve. Note that the hydraulic fluid of the shift actuator control valve may be configured to be performed through a route different from the route through the tank 201 described above.

  As described above, the oil accumulated in the oil reservoir is forcibly discharged by the pump 213, stored in the temporary tank 201, and then supplied again as lubricating oil and hydraulic oil for the control system hydraulic circuit into the case 2 by the pump 214. To do. With this mechanism, the oil level of the oil sump can be lowered from the lower end of the gears of the speed change drive train and the auxiliary drive train that rotate at a relatively high speed during vehicle travel. That is, the loss of stirring resistance caused by the gear in the transmission 2 can be reduced, so that the work transport vehicle can be speeded up more economically.

  Further, although the leakage amount of the lubricating oil and hydraulic oil increases approximately proportionally with the increase in the engine speed, the pumps 213 and 214 are directly connected to the output shaft 6 of the engine 5 in the present embodiment. The amount of recovered oil also increases substantially proportionally as the engine speed increases. In addition, by setting the discharge amount of the pump 213 slightly larger than that of the pump 214, the tank 201 is always maintained in an overflow state. Therefore, the oil level of the oil sump is always stable at a predetermined position, and the effect of reducing the stirring resistance loss can be obtained.

Further, in order to prevent the oil in the oil sump from being biased to the left and right and the gears on the left and right end sides being soaked deeply and increasing the stirring resistance when the vehicle travels in a posture inclined to the left and right on a rough road or the like, this embodiment In the stepped transmission 19, a partition wall 203 is provided at the bottom of the transmission case 8 to block oil.
More specifically, the partition wall 203 is provided so as to partition a space for accommodating the upper shift drive train and the like and a space near the bottom of the case 8. The partition wall 203 has a substantially horizontal plate shape, and has an inflow port 203a immediately below the front and rear wheel driving force extraction shafts 346 and 11 located at the leftmost end in the case 8. When the oil level is lower than the partition wall 203, the oil leaked from the speed change drive train or the like is configured to mainly flow into the bottom of the case 8 from the inflow port. The partition wall 203 extends to the right from the edge of the inflow port 203 a, bends substantially vertically upward in the vicinity of the tank 201, and has an upper end at substantially the same height as the upper end of the tank 201. Thereby, the flow path in which the oil overflowing from the tank 201 falls directly into the oil reservoir is formed. The tank 201 may be provided outside the mission case 8.

  With the above configuration, even when the vehicle travels in a laterally inclined posture, the oil accumulated under the partition wall 203 is blocked by the partition wall 203, and the left and right end gears are prevented from being deeply immersed in the oil. Yes. However, depending on the inclination direction of the vehicle, a part of the oil flows out from the inlet 203a. Therefore, in order to prevent the oil from preferentially biasing toward the input shaft gear rotating at the highest speed, the inlet 203a has a low speed as described above. Is provided at the end of the output shaft gear.

The embodiment of the work transport vehicle according to the present invention has been described above.
In the stepped transmission 19 of the present embodiment, the electromagnetic switching valve 274 that controls only on / off of the hydraulic oil supply is used to control the sub-clutch 302, but the electromagnetic switching valve 274 is used instead. As with the main clutch 301, a proportional pressure reducing valve may be used. As a result, the clutch pressure can be changed according to the speed stage to which the speed change drive train is changed and the shift-up / shift-down operation to change any slip ratio, that is, the auxiliary drive train to the optimum reduction ratio.
Further, the stepped transmission 19 of the present embodiment is a three-speed automatic transmission, but the speed stage is not limited to three, and the sub-clutch and the auxiliary drive train mechanism are applied to a transmission of any configuration. can do.

  The above is a recommended example of the invention disclosed in the present application, and it is possible to change the structure such as arrangement and combination of parts and the like that can be easily understood by those skilled in the art without departing from the scope of the claims. .

  The work transport vehicle of the present invention can be configured as a work transport vehicle for various uses.

The side view which showed the whole structure of the work transport vehicle which concerns on one Example of this invention. The top view which showed the whole structure of the working vehicle which concerns on one Example of this invention. The skeleton figure which shows the structure of a stepped transmission. The cross-sectional front view which shows the structure of a stepped transmission. Sectional front view which showed the detail of the fork control mechanism. The cross-sectional left view which showed the detail of the fork control mechanism. The figure which showed the hydraulic circuit of the transmission control system. The figure which showed the transmission control flow. The figure which showed the shift point characteristic model figure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Work vehicle 8 Mission case 10 Front output shaft 11 Rear output shaft 18 Input shaft 19 Stepped transmission 201 Tank 203 Bulkhead 221 First shifter shaft 222 Second shifter shaft 230 Hydraulic cylinder 231 Hydraulic cylinder 240 Fork control shaft 241 Lever 242 Rotating lever 301 Main clutch 302 Sub clutch 303 Clutch input shaft 306 Main clutch output shaft 308 Intermediate shaft 311 Traveling transmission shaft 316 Traveling output shaft 324 First shifter 325 First fork 326 Second shifter 327 Second fork 330 Sub clutch output shaft 346 Front wheel drive force take-out shaft

Claims (7)

  A work transport vehicle having a structure in which an engine, an axle, and a stepped transmission that transmits driving force from the engine to the axle are disposed below the loading platform, and the stepped transmission includes a plurality of steps. A shift drive train, an auxiliary drive train, a main clutch for the plurality of shift drive trains, and a sub-clutch for the auxiliary drive train are provided. The axle is driven by a drive train, and during the shift operation, the main clutch is disengaged to select one of the plurality of shift drive trains, and the sub-clutch is engaged and the engine is connected via the auxiliary drive train. A work carrier characterized by transmitting power to the axle.   The engine is arranged such that the crankshaft is directed in the longitudinal direction of the fuselage, and in the stepped transmission, the transmission shaft from the input portion that receives the output of the engine to the output portion to the axle is provided in the longitudinal direction of the fuselage. The work transportation vehicle according to claim 1, wherein the work transportation vehicle extends and is arranged in parallel in the left-right direction of the machine body.   The stepped transmission includes a plurality of shifter shafts for selecting one shift drive train for the plurality of shift drive trains, and the shifter shafts are arranged in parallel in the horizontal direction. The work transportation vehicle according to claim 1 or 2.   The oil is collected and stored from the case so that the oil level of the oil in the case housing the stepped transmission is lower than a predetermined height when the engine is operated, and the stored oil is stored in the stepped transmission. The work transport vehicle according to claim 1, further comprising a tank that is discharged into the case as lubricating oil.   5. The main clutch, the support clutch, and the shifter shaft of each of the stepped transmissions are each configured to be hydraulically driven, and oil stored in the tank is used as hydraulic fluid for them. The work vehicle described in 1.   The amount of oil recovered into the tank increases as the engine speed increases, and the amount of oil recovered into the tank is greater than the amount of oil released into the case as lubricating oil and hydraulic oil. The work transportation vehicle according to claim 4 or 5, characterized by the above-mentioned. The work transport vehicle according to claim 1, wherein the main clutch also serves as a starting clutch.

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