JP2005170254A - Steering wheel driving unit and four-wheel drive vehicle equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering vehicle wheel driving unit having an excellent maintenance property while improving a steering property of a steering wheel, and a four-wheel drive vehicle equipped with it. <P>SOLUTION: This steering vehicle wheel driving unit 15 comprises a housing 28 supporting a single axle 35, a hydraulic motor for driving the axle installed in the housing 28, and front wheels 36, 36 as single steering wheel fixed to ends of the single axle 35. The housing 28 is rotatably mounted to a vehicle frame 2 via a king pin 27, and the hydraulic motor 10 is of a variable displacement type. A movable swash plate 53 of the hydraulic motor 10 is constituted so as to be inclined between the king pin 27, the housing 28 and the vehicle frame 2 by relative rotation in steering. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for a steering wheel drive unit and a four-wheel drive vehicle including the steering wheel drive unit, and more specifically, a drive unit in which a variable displacement hydraulic motor is disposed on a steering wheel. The present invention relates to a technique for improving running performance and turning performance.

  Work vehicles such as lawn mowers and riding lawn mowers are required to be improved in running performance and turning performance because they are repeatedly driven and turned even in a narrow road and soft ground. Therefore, in order to improve the turning performance of the work vehicle and facilitate turning in the left-right direction, a steering wheel for turning the driving wheel to the left and right by operating a steering tool such as a round handle is provided. Several are known.

  For example, in Patent Document 1, a work vehicle including a steering mechanism interposed between a pair of steering wheels and a steering tool (steering wheel), and an operation amount (steering angle from a position where the steering wheel is set to go straight) ) Is increased, the steering wheel configuration is proposed in which the increasing rate of the left / right turning angle per steering wheel unit operation amount on the steering wheel inside the turning is increased. By adopting such a configuration, it is possible to increase the left / right turning angle of the steered wheels without interfering with the left / right turning due to the differential driving drive wheels.

US Patent Application Publication No. 2003/0106725

  Certainly, the steering wheel of the work vehicle proposed in Patent Document 1 can increase the left-right turning angle according to the operation amount with a small handle operation. However, since the self-drive of the steered wheels is impossible, the traveling speed associated with the turn depends on the drive force of the rear wheels, and it is necessary to passively adjust the speed by the operator during the turn. In particular, if the drive speed is slow when turning left or right, the field or the like will be damaged, and the operator has to manually increase the drive speed.

  In addition, the steering wheel in the conventional work vehicle described above may require replacement of the work vehicle's transmission case, each drive wheel, gear mechanism, etc. as a whole when a drive device or the like is broken or defective. Maintenance was troublesome.

  Accordingly, the present invention relates to a steering wheel drive unit and a work vehicle using the same, and solves the above-described conventional problems, and proposes a work vehicle that improves the turning response of the steering wheel and has excellent maintainability. For the purpose.

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

  That is, in claim 1, a housing supporting a single axle, a hydraulic motor for driving the axle provided in the housing, a single steering wheel fixed to an end of the single axle, The housing is a steering wheel drive unit, and the housing is rotatably attached to the vehicle frame via a king pin.

  According to a second aspect of the present invention, a housing supporting a single axle, a hydraulic motor for driving the axle provided in the housing, and a single steering wheel fixed to an end portion of the single axle are provided. A steering wheel drive unit, wherein the single axle is disposed on the same axis inside the hydraulic motor, and the housing is rotatably attached to the vehicle frame via a king pin. Is.

  According to a third aspect of the present invention, in the first or second aspect, the hydraulic motor is a variable displacement type, and the volume adjuster of the hydraulic motor is operated by a relative rotation at the time of steering between the king pin, the housing, and the vehicle frame. It is what is done.

  According to a fourth aspect of the present invention, in the third aspect, the king pin is rotatably passed through a cylinder fixed to the vehicle frame, and the volume adjuster is operated by relative rotation of the king pin in the cylinder. Is.

  According to a fifth aspect, in the first or second aspect, an oil conduit of the hydraulic motor is provided in the king pin.

  In Claim 6, it comprises a steering wheel, a king pin, a housing connected to the king pin to support the steering wheel, and a first hydraulic motor for driving the steering wheel provided in the housing, A work vehicle including a steering wheel drive unit that is integrally rotatable by rotation of the kingpin with respect to a vehicle frame, the other second hydraulic motor and a traveling drive wheel driven thereby, A hydraulic pump that supplies oil to the second hydraulic motor is provided, and both hydraulic motors are connected in series to the hydraulic pump in a hydraulic circuit that fluidly connects the first and second hydraulic motors to the hydraulic pump. Is provided with a shift switching valve that can be switched between a state connected to and a state connected in parallel.

  According to a seventh aspect of the present invention, in the sixth aspect, the shift switching valve is further switchable so that the oil from the hydraulic pump flows only to the second hydraulic motor among the two hydraulic motors.

  According to an eighth aspect of the present invention, in the seventh aspect, the second hydraulic motor is of a variable displacement type, and the volume regulator of the hydraulic motor is configured such that the shift switching valve is provided only for the oil pressure from the hydraulic pump to the second hydraulic motor. When the operation is switched to flow, the shift switching valve is interlocked and linked so as to be operated in the direction of reducing the volume.

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

  With the configuration shown in claim 1, the steered wheels in the steered wheel drive unit can be driven separately, the left and right turning performance of the work vehicle can be improved, and the smooth acceleration / deceleration by the hydraulic motor can be achieved. The steerability is improved. Further, a wide space below the vehicle frame is ensured.

  Since the configuration shown in claim 2 is adopted, the number of members interposed between the motor shaft and the axle can be reduced, the volume in the housing can be made small and compact, and the housing can be easily stored in the wheel rim.

  With the configuration shown in claim 3, when the housing is steered from side to side from the straight position, the relative displacement of the volume controller of the hydraulic motor with respect to the vehicle frame is automatically converted based on the straight position of the housing. The steering property can be further enhanced.

  With the configuration shown in claim 4, the steering wheel drive unit can be easily attached to and detached from the support, and the king pin and the housing can be easily maintained and replaced.

  Since it is set as the structure shown in Claim 5, the oil conduit | pipe etc. in the said drive unit can be arrange | positioned in the hollow part of this support body, While preventing the damage | wound of this oil conduit | pipe etc., this drive unit is comprised well Can be made.

  With the configuration shown in claim 6, since the operation of the discharge oil amount and the discharge direction of the hydraulic pump can be performed continuously, it is used as a main transmission that can be operated during traveling, and the first hydraulic motor and the second hydraulic pressure are used. By switching the oil flow rate to the motor in stages and selecting the speed range according to the driving situation, the driving speed of the left and right front and rear wheels can be changed over a wide range. Further, since each of the hydraulic motors is connected to a hydraulic pump, each steering wheel and traveling drive wheel can be easily driven by four wheels. Further, by connecting the drive units with a hydraulic circuit, it is possible to easily secure a space for disposing a mower or the like below the four-wheel drive vehicle.

  With the configuration shown in claim 7, each steered wheel and traveling drive wheel can be easily switched from four-wheel drive to two-wheel drive, and the maneuverability of the four-wheel drive vehicle is improved.

  Since it is set as the structure shown in Claim 8, the economical high-speed driving | running | working by two-wheel drive is attained. Such switching can be performed instantaneously when traveling on a flat ground, and the traveling time can be shortened, resulting in high work efficiency.

Next, embodiments of the invention will be described.
1 is a plan view showing the overall configuration of a work vehicle according to a first embodiment of the present invention, FIG. 2 is a schematic plan view of a steering mechanism used in the first embodiment, and FIG. 3 is a front wheel drive unit on one of the left and right sides. FIG. FIG. 4 is an explanatory schematic view of the steering mechanism showing the turning state of the work vehicle, and FIG. 5 is a plan view showing the turning state of the work vehicle. 6 is an enlarged front sectional view of the upper part of the front wheel drive unit, FIG. 7 is a lower enlarged front sectional view of the front wheel drive unit, FIG. 8 is a sectional view taken along line AA in FIG. 10 is a cross-sectional view taken along the line CC in FIG. 3, FIG. 11 is a plan view of the control arm, FIG. 12 is a top plan view of the housing, and FIG. FIG. 14 is a front sectional view of the rear wheel drive unit. 15 is a hydraulic circuit diagram according to the first embodiment, FIG. 16 is a hydraulic circuit diagram in which a part of the hydraulic circuit diagram of FIG. 15 is changed, and FIG. 17 is an arrangement circuit diagram of sensors and the like. 18 is a plan view showing the overall configuration of the work vehicle according to the second embodiment of the present invention, FIG. 19 is a plan view in which the rear wheel drive device of FIG. 18 is changed, and FIG. 20 is the rear wheel drive of FIG. FIG. 21 is a hydraulic circuit diagram according to the second embodiment. FIG. 22 is a front sectional view in which a part of the steering wheel drive unit is changed. 23 is a front sectional view in which a part of the steering wheel drive unit is changed, FIG. 24 is a sectional view taken along the line DD in FIG. 23, and FIG. 25 is a top plan view of the housing. FIG. 26 is a plan view showing the overall configuration of the work vehicle according to the third embodiment of the present invention, FIG. 27 is a schematic plan view of the steering mechanism used in the third embodiment, and FIG. 29 is a front sectional view of the unit, FIG. 29 is a plan view showing the sudden turning state of the work vehicle, FIG. 30 is a plan view showing the interlining turning state of the work vehicle, and FIG. 31 is a sectional view taken along the line EE in FIG. 32 is a cross-sectional view of the drive unit for the rear wheel on the other side at the same position as the arrow EE in FIG. 28, FIG. 33 is a plan cross-sectional view of the control arm and the support body accompanying steering of the rear wheel, FIG. FIG. 35 is a plan sectional view of a control arm and a support body according to steering of the front wheels, FIG. 35 is a hydraulic circuit diagram according to the third embodiment, and FIG. 36 is a layout circuit diagram of sensors and the like.

(First Example)
First, the overall configuration of the work vehicle 1 according to the present embodiment will be described below.
As shown in FIG. 1, a work vehicle 1 according to this embodiment is a two-wheel steering / four-wheel drive type, and includes an engine 3, a mower 4, a hydraulic pump 5, non-steering on left and right vehicle frames 2 along the front-rear direction. A (rear) wheel, a steering (front) wheel, a handle 16, a rear discharge duct 74, and the like are arranged.

  The engine 3 is supported by a vibration isolating member 75 at the rear end of the vehicle frame 2, and a device group such as a radiator, a battery, an air cleaner, and a muffler is disposed around the engine 3 (not shown). A mower 4 having three cutting blades 4a, 4a, 4a is supported on the abdomen of the work vehicle 1 (mid-mount mower), and the mower 4 is disposed above the engine 3 and an input shaft (not shown). It is connected through. A rear discharge duct 74 is provided along the front-rear direction extending backward between the non-steering (rear) wheels of the work vehicle 1. The duct 74 is connected to the mower 4, and the turf grass cut by the mower 4 is sent to a grass collection container (not shown) installed at the rear end of the work vehicle 1 through the rear discharge duct 74. To be.

  A variable displacement hydraulic pump 5 is disposed in the vicinity of the engine 3 mounted at an appropriate location on the vehicle frame 2. The hydraulic pump 5 is driven by power from the engine 3 via pulleys disposed on the engine 3 and respective input shafts and output shafts (not shown). The hydraulic pump 5 is fluidly connected to first and second hydraulic motors 10 and 80, which will be described later, via oil passages (first circuit 89, second circuit 90, etc.) provided in the work vehicle 1. (See FIG. 15). In addition, the arrangement positions of the engine 3 and the hydraulic pump 5 in the work vehicle 1 are not limited to this, and the hydraulic pump 5 is laid out at an appropriate position according to the direction of the crankshaft of the engine 3.

  The oil discharge amount and the discharge direction from the hydraulic pump 5 are changed by operating a movable swash plate, and the movable swash plate 106 is connected to a main transmission pedal 106 provided on the work vehicle 1 via connecting means such as an arm or a link. The work vehicle 1 is connected to a speed adjusting operation tool such as a lever or a lever, and the forward / backward movement of the work vehicle 1 is switched by operating the operation tool. A main transmission sensor (not shown) disposed in the vicinity of the main transmission pedal 106 is connected to a controller 107 which will be described later, and the work vehicle 1 travels (forward / reverse) by a stepping operation of the main transmission pedal 106. The direction is detected (see FIG. 17).

  The hydraulic pump 5 is of a variable displacement type. When the oil discharge amount and the discharge direction are changed by output adjusting means such as tilting of the movable swash plate, there is no change from the drive units 15L and 15R and the drive units 13L and 13R described later. A step shift output can be obtained.

  A pair of left and right drive units 15L and 15R each having a front wheel 36, which is a steered wheel, are disposed at the front portion of the vehicle frame 2 so as to be steerable (left and right rotation). A pair of left and right drive units 13L and 13R each having a rear wheel 79, which is a non-steered wheel, are disposed at the rear portion so that the position cannot be changed (left and right rotation). A cross member 14 is horizontally provided in the left and right direction of the front portion of the vehicle frame 2, and drive units 15L and 15R are pivotally provided at both left and right ends of the cross member 14 so that the relative position can be changed (left and right rotation). Yes. The drive units 15L and 15R each include a variable displacement type first hydraulic motor 10, and the drive units 13L and 13R each include a variable displacement type second hydraulic motor 80. The left and right first hydraulic motors 10 are fluidly connected to the hydraulic pump 5 in parallel in a closed circuit through a pipe (not shown), and thereby hydraulic pressure is applied according to the load acting on each of the left and right first hydraulic motors 10. A differential effect is produced. The same applies to the left and right second hydraulic motors 80.

  Hereinafter, the drive unit 15L (13L) will be described unless otherwise specified. That is, in the present embodiment, the left and right drive units 15L and 15R (or 13L and 13R) are not different from each other, and are substantially the same and arranged symmetrically.

Next, the steering mechanism of the front wheels 36 and 36 which are steering wheels will be described.
As shown in FIGS. 2 and 3, a steering link mechanism 18 is formed in the work vehicle 1 by left and right steering gear mechanisms 17, 17 that interlock and connect the front wheels 36, 36 to the handle 16. The handle 16 is connected to an output shaft 21 at a substantially central portion of the steering link 20 via a steering gear box 19. By the turning operation of the handle 16, the turning of the steering link 20 is transmitted to the steering link mechanism 18, and the left and right drive units 15L and 15R are turned left and right via the left and right steering gear mechanisms 17 and 17. It is. A hydraulic power steering may be interposed between the handle 16 and the output shaft 21 in order to convert the turning power of the handle 16 into oil pressure. In such a case, instead of the gear box 19, a hydraulic control device such as a power steering cylinder is provided.

  A steering angle sensor 104 that detects a rotation (steering) angle of the handle 16 is disposed in the vicinity of the handle 16. The steering angle sensor 104 is connected to a controller 107 described later (see FIG. 17).

  The steering link mechanism 18 has a fan-shaped gear as a drive gear 22 at a position opposite to the left and right above the cross member 14 with a substantially vertical fulcrum pin 23 in a state where the tooth circumference is directed left and right. Each is pivotally supported so as to be horizontally rotatable. One end of a rod 25 is attached to each inner end of the drive gear 22 (from each fulcrum pin 23 from the left and right center of the work vehicle 1) via a pivot joint 24. On the other hand, the other end of the rod 25 is attached to both ends of the steering link 20 attached to the output shaft 21 of the steering gear box. Thus, when the handle 16 is turned to the left and right, the drive gears 22 are rotated in opposite directions.

  A support body 26 of a king pin 27 is fixed to each of the left and right ends of the cross member 14, and a cylindrical king pin 27 that is opened up and down is inserted into the support body 26 from below so as to be rotatable left and right. Has been. A fan-shaped gear as a driven gear 30 is fitted on the upper end portion of the king pin 27, and the king pin 27 is pivoted substantially horizontally with the driven gear 30 as a pivot of the driven gear 30. A periodontal portion on the inner side of the driven gear 30 meshes with a periodontal portion on the outer side of the drive gear 22. A housing 28 is connected to the lower end portion of the king pin 27 to constitute the drive unit 15. Since the king pin 27 is rotated integrally with the driven gear 30, the housing 28 connected to the king pin 27 is attached to the vehicle frame 2 via the king pin 27 so as to be rotatable relative to the vehicle frame 2. become. Reference numeral 29 denotes a mount boss portion formed on the upper surface of the housing 28, and a base plate portion 27a provided at the lower portion of the king pin 27 is mounted (see FIG. 6).

  As shown in FIGS. 4 and 5, when the handle 16 is rotated to the left or right, one steering gear mechanism 17 is rotated so that the drive gear 22 moves forward in the periodontal region. Thus, the driven gear 30 meshed with the drive gear 22 is rotated so that the periodontal portion is moved forward. The other steering gear mechanism 17 is rotated so that the driven gear 30 moves rearward along the periodontium together with the drive gear 22. Then, in conjunction with the rotation of the driven gear 30, one of the front wheels 36 is rotated left and right so that the front end faces outward and the other turns the front end inward. The driving gear 22 and the driven gear 30 are arranged so that the front end of the front wheel 36 becomes closer to the left and right inner sides as the front end of the driving gear 22 approaches the front end of the driven gear 30 (in other words, the rear ends move away from each other). Turn to. On the contrary, the front end of the front wheel 36 is configured to face the left and right sides as the front end of the drive gear 22 and the front end of the driven gear 30 move away (in other words, the rear ends approach each other). Yes.

  In particular, in this embodiment, the Ackerman-Jantt mechanism is provided in which the inner and outer wheels are provided with a left and right turning angle so that the left and right turning angles of the inner wheel are larger than those of the outer wheel. I try to increase it. Specifically, by making the shapes of the drive gear 22 and the driven gear 30 non-circular, such a left-right turning angle difference appears. That is, the radius R1 of the drive gear 22 is longer than the radius R2 of the driven gear 30 regardless of the rotation direction and angle thereof, thereby amplifying the left-right rotation allowable angle of the front wheel 36. Further, the drive gear 22 is formed such that the radius R1 changes with rotation, and the driven gear 30 is also shaped so that the radius R2 compensates for this.

  When the steering gear mechanism 17 is interlocked with the inner ring, the radius R1 increases as the rear ends of the drive gear 22 and the driven gear 30 approach each other, and the radius R2 decreases as the radius R1 increases. To do. On the other hand, when the steering gear mechanism 17 is interlocked with the outer wheel, the radius R1 decreases as the front ends of the drive gear 22 and the driven gear 30 approach each other, and the radius R2 is reduced by the amount of the decrease of the radius R1. Increase. Therefore, as the turning angle of the handle 16 is increased, the gear diameter ratio R2 / R1 of the steering gear mechanism 17 interlocked with the outer wheel is increased, and the increasing rate of the left and right rotation angle of the outer wheel is decreased. At the same time, the gear diameter ratio R2 / R1 of the steering gear mechanism 17 linked to the inner wheel decreases by the increase of that of the steering gear mechanism 17 linked to the outer wheel, and the rate of increase of the left and right rotation angle of the inner ring is large. Become.

  With the above-described configuration, the left-right rotation angle difference between the inner and outer wheels of the front wheel 36 can be increased as the rotation angle of the handle 16 increases. In addition, the drive units 15L and 15R can be rotated largely by providing a difference in the left and right rotation angle between the inner ring and the outer ring with a small operation amount of the handle 16. In the present embodiment, the turning center point 110 is set to appear on the rotation axis of the rear wheel 79 as shown in FIG. At that time, since the load acting on the rear wheel 79 on the inner ring side (left side in FIG. 5) exceeds the driving force, the rotation of the rear wheel 79 stops.

  Here, as shown in FIG. 5, in the plan view, the left-right center line in the front-rear direction of the work vehicle 1 (vehicle frame 2) is A1, and the left-right rotation centers of the left and right front wheels 36, 36, that is, both left-right drive The straight line in the left-right direction connecting the axes of the king pins 27 of the units 15L and 15R is A2, the axes of the left and right rear wheels 79 and 79, that is, the axes of the left and right drive units 13L and 13R (both second hydraulic motors 80). A straight line connecting the left and right directions is A3, and further, an intersection point between the line A1 and the line A2 is a point 111, and an intersection point between the line A1 and the line A3 is a point 112. From the turning center point 110 to the point 111 Is the turning radius of the vehicle center between the left and right front wheels 36 (hereinafter simply referred to as “the turning radius 111a of the front wheel 36”), and the distance from the turning center point 110 to the point 112 is the left and right rear wheel 79.・ In 79 vehicles The turning radius (hereinafter, simply referred to as "turning radius 112a of the rear wheel 79") it becomes.

  Then, when the work vehicle 1 is turned, the turning radius 111a of the front wheel 36 is larger than the turning radii 111a and 112a of the front wheel 36 and the rear wheel 79. This is because, while the rear wheel 79 is not steered left and right, the turning center point 110 does not appear between the front wheel 36 and the rear wheel 79 when the front wheel 36 is steered by the handle 16. This is because it appears on the rotation axis of the rear wheel 79. Therefore, in order to obtain a smooth turn in the four-wheel drive state, it is necessary to increase the rotation speed of the first hydraulic motor 10 more than the second hydraulic motor 80 at a rate commensurate with this turning radius difference. As will be described later, when the handle 16 is turned, the volume of the first hydraulic motor 10 is automatically reduced to improve the turning performance of the work vehicle 1.

  In the present embodiment, the volume of the first hydraulic motor 10 is decreased at the same left / right ratio (X) as will be described later, while the front wheel rotation difference between the inside and outside of the turn is the left and right first hydraulic pressure. Although it is absorbed by the hydraulic differential effect of the motor 10, as another countermeasure, the volume reduction rate is changed independently on the left and right of the first hydraulic motor 10, that is, the front wheels on the inside and outside of the turn. The volume change amount (Y) corresponding to the rotation difference is subtracted from the ratio (X) for the first hydraulic motor 10 inside the turning, and added to the first hydraulic motor 10 outside the turning. The rotation difference may be positively generated.

Next, the drive unit 15 will be described below.
As shown in FIGS. 3 and 6, in the drive unit 15 for the steered wheels, a cap member 31 is connected by a joint member 34 so as not to be relatively rotatable so as to cover an upper portion of the driven gear 30. ing. The king pin 27 on which the driven gear 30 is fitted is provided between the lower surface of the driven gear 30 and the upper opening edge of the support 26, and the upper surface of the base plate portion 27 a of the king pin 27 and the support 26. Thrust bearings 33a are respectively interposed between the lower opening edge portions. A bearing (bush) 33b is interposed between the outer peripheral surface of the king pin 27 and the inner peripheral surface of the support 26, and further, between each thrust bearing 33a and the bearing (bush) 33b. Has an oil seal. Then, the retaining gear 32 prevents the driven gear 30 from coming off upward, so that the king pin 27 is stably and rotatably supported inside the support body 26.

  The king pin 27 can be easily inserted and removed from the support 26 by first removing the cap member 31 from the support 26 and then removing the retaining ring 32 and removing the driven gear 30. That is, the king pin 27 inserted from below the support body 26 formed in a cylindrical shape is fitted to the driven gear 30 at the upper end, but by removing the driven gear 30, the support body 26 can be easily removed from below. With such a configuration, the king pin 27 and the housing 28 can be easily maintained and replaced.

  In the hollow portion of the kingpin 27, a drain conduit 46, oil pipes 47 and 48, and a brake wire 49 are provided. The oil pipes 47 and 48 are fluidly connected to the hydraulic pump 5 and the drain conduit 46 is fluidly connected to an oil tank (not shown) via pipe joints 46b, 47b and 48b fixed to the upper surface of the cap member 31, respectively. . The outer wire of the brake wire 49 is held on the upper surface of the cap member 31 and connected to a brake pedal (not shown). These drain conduits 46 and the like rotate together with the housing 28 and the king pin 27 as will be described later. The oil pipe 47 and the like are made of an elastic pipe material having a slight slack, and the function is not impaired even if twisted. In addition, the rotation of the king pin 27 is not hindered. Further, by providing the oil pipe 47 and the like in the hollow portion of the cylindrical king pin 27, it is possible to prevent the oil pipe 47 and the like from being damaged and to make the drive unit 15 well organized.

  As shown in FIGS. 3 and 7, the housing 28 having two halved housing portions 28a and 28b that can be separated and joined in the vertical direction along the axis of the axle 35 is fixed to the lower end of the king pin 27. ing. In the housing 28, a variable displacement type first hydraulic motor 10, a planetary gear mechanism speed reduction mechanism 38, a brake mechanism 39, a tilting mechanism (volume controller) 40 of a movable swash plate 53, and the like are disposed. The axle 35 is supported in the horizontal direction by the bearing support portions 67 and 67 disposed in the housing 28, and one end of the axle 35 is directed outward from the work vehicle 1 from one side of the housing 28. The front wheel 36 is fixed to a hub formed at the protruding end.

  In the vicinity of the axle 35, axle rotation speed sensors 102 and 102 are disposed, and the axle rotation speed sensors 102 and 102 are connected to a controller 107 described later (see FIG. 16).

  The upper half housing portion 28a and the lower half housing portion 28b are brought into contact with each other through a joint surface and fixed with screws 37 by bolts 37. The housing 28 is provided with each drive unit 15 in the operating position. In this state, the joint surface is disposed so as to be parallel to the axle 35. Further, a mount boss portion 29 is formed on the upper surface of the upper half housing portion 28a, and the mount boss portion 29 is connected to a base plate portion 27a at the lower end portion of the king pin 27. The housing 28 may be constituted by two halved housing portions that can be separated and joined in the left-right direction through a joining surface perpendicular to the axis of the axle 35.

Next, the first hydraulic motor 10 will be described in detail below.
As shown in FIG. 3 and FIG. 7 to FIG. 9, a center section 41 is disposed in the center of the housing 28 in the left-right direction, and the center section 41 is bolted to the upper half housing portion 28a from below. -The screw is fixed by 42. By using the center section 41, the housing 28 can be separated from the housing 28, so that the processing of the housing 28 is facilitated and oil leakage to the outside of the housing 28 can be prevented. Further, the housing 28 is divided into upper and lower halves, and the center section 41 is fixed to the upper halved housing b portion 28a, thereby reducing the influence of hydraulic pressure on the center section 41 and the like.

  The center section 41 is formed in a substantially rectangular plate shape, and an oil supply / discharge port 41a and an oil supply / discharge port 41b are concentratedly opened on the upper surface. Three pipe joints 46a, 47a and 48a are screwed onto the upper wall of the upper half housing portion 28a, and the oil supply / discharge port 41a and the oil supply / discharge port 41b are connected to the pipe joints 47a and 48a. The oil pipes 47 and 48 provided in the hollow portion of the kingpin 27 are connected to the hollow pipes 27 and 48, respectively. The pipe joint 46 a communicates with an oil reservoir in the housing 28 and is connected to a drain conduit 46 in the hollow portion of the king pin 27. On the installation surface with the first hydraulic motor 10, a kidney port 50a communicating with the oil supply / discharge port 41a and a kidney port 50b communicating with the oil supply / discharge port 41b are opened, and the intake ports 50a and 50b are connected to the suction portion. A cylinder block 51 constituting the first hydraulic motor 10 is rotatably supported so that the discharge part communicates. Further, a through hole 43 is formed on the rotational shaft core at the substantially center of the center section 41, and a motor shaft 56 formed in a hollow shape for inserting the axle 35 into the through hole 43 is provided with the installation surface and the motor shaft 56. Are supported so as to protrude to the opposite side.

  Pistons 52, 52... Are reciprocally fitted in a plurality of cylinder holes drilled in the cylinder block 51 via biasing springs, and the heads of the pistons 52, 52. A thrust bearing 54 of a movable swash plate 53 as a volume adjuster is in contact. Thus, the axial piston type first hydraulic motor 10 is formed. An opening is formed in the left-right direction at the center position of the movable swash plate 53, and the axle 35 is penetrated through the opening. A convex arc surface is formed on the left side of the movable swash plate 53, and is in sliding contact with a pedestal 55 having a concave arc surface installed on the left inner surface of the upper half housing portion 28a. By adopting such a shape, the movable swash plate 53 can be tilted in the left-right direction along the pedestal 55. The cradle-shaped movable swash plate 53 may be a trunnion type that does not require the base 55 as described above. In the present invention, the first hydraulic motor 10 is not limited to the axial piston type, but may be a radial piston type. In this case, the volume controller is a cam ring.

  The oil pumped from the hydraulic pump 5 through the oil pipe 47 (48) to the pipe joint 47a (48a) is supplied from the oil supply / discharge port 41a (41b) introduced into the center section 41 to the cylinder block 51. Is sent to. In this way, the first hydraulic motor 10 and the hydraulic pump 5 are fluidly connected to each other. In addition, the movable swash plate 53 has its initial position (tilt) so that the contact surface portion is tilted by a predetermined angle from a plane (horizontal plane) perpendicular to the rotational axis of the cylinder block 51 as shown in FIG. Set the vehicle straight position). When the contact surface portion is operated so as to approach the vertical direction from this position, the volume of the first hydraulic motor 10 is changed so that the rotational speed of the front wheel 36 is increased compared to the initial position. The Details of the tilting mechanism 40 of the movable swash plate 53 will be described later.

  As described above, each drive unit 15 is provided with the first hydraulic motor 10 for driving the front wheels 36, and can be driven individually for each front wheel 36. In addition, since the hydraulic pump 5 and each first hydraulic motor 10 are connected via easily deformable piping, when the power of the engine 3 is transmitted to the left and right drive units 15L and 15R, There is no need to separately provide a drive shaft, a transmission mechanism, and the like, and the space below the vehicle frame 2 can be secured widely for the arrangement of the mower 4, the rear discharge duct 74, and the like.

Next, the speed reduction mechanism 38 will be described in detail below.
As shown in FIGS. 3, 7, and 8, a two-stage reduction planetary gear mechanism is configured as the speed reduction mechanism 38 on the right side of the center section 41. An axle 35 is horizontally penetrated through the through hole 43 of the first hydraulic motor 10, and the motor shaft 56 is loosely supported on the axle 35 via a bearing (bush). Thus, since the motor shaft 56 of the first hydraulic motor 10 is hollow and the motor shaft 56 is loosely fitted to the axle 35 so as to be relatively rotatable, the first hydraulic motor 10 is disposed. The volume in the housing 28 can be made small and compact, and it can be comfortably stored in the wheel rim.

  The motor shaft 56 is spline-fitted to the rotation center portion of the cylinder block 51, and an output gear 65 is fitted to one end of the motor shaft 56 so as not to be relatively rotatable. On the outer periphery of the output gear 65, a plurality of first planetary gears 57, 57... Are rotatably supported by the first carrier 58 so as to be able to mesh with the output gear 65, and simultaneously mesh with the internal gear 59. Has been. The internal gear 59 is fixed to the inner wall surfaces of the upper half housing portion 28a and the lower half housing portion 28b in a non-rotatable manner by a rotation stop projection 59a formed on the outer peripheral surface thereof.

  The first carrier 58 has internal teeth at the center of rotation, and is installed and meshed on one side of a wide sun gear 60 loosely fitted on the axle 35. On the right side of the first carrier 58, a plurality of second planetary gears 61, 61... Are pivotally supported by the second carrier 62 so as to be able to mesh with the sun gear 60, and simultaneously meshed with the internal gear 59. Yes. The rotation center portion of the second carrier 62 is spline-fitted with one end portion of the axle 35 so as not to be relatively rotatable.

  The cylinder block 51 driven to rotate by the first hydraulic motor 10 is driven by the cylinder block 51 → the motor shaft 56 → the output gear 65 → the first planetary gears 57, 57... → the first carrier 58 → the sun gear. 60 → second planetary gears 61, 61... → second carrier 62 → axle 35 → front wheel 36 so that the work vehicle 1 can travel.

  As shown in FIG. 8, the housing 28 has a diameter on the inner side (right side in FIG. 8) on the inner side (right side in FIG. 8) side than the outer side (left side in FIG. 8) side of the center section 41. It is comprised so that a direction dimension may become large (L1 <L2). Therefore, when the first hydraulic motor 10 is disposed outside the housing 28, the first hydraulic motor 10 is positioned outside the wheel rim in order to be able to use a high-speed, low-torque type with a small size so as to be accommodated in the wheel rim. A sufficient space for disposing the speed reduction mechanism 38 inside the housing 28 can be secured.

  As described above, the first hydraulic motor 10, the axle 35, and the like are disposed in the housing 28 so that the housing 28 can be rotated relative to the vehicle frame 2. The drive unit 15 can be configured without providing a complicated mechanism for transmitting power from the vehicle to the axle 35. In addition, since the first hydraulic motor 10 and the axle 35 are disposed in common in the housing 28, the number of members interposed between the first hydraulic motor 10 and the axle 35 can be reduced. Furthermore, by providing the hollow motor shaft 56, the drive by the first hydraulic motor 10 can be transmitted to the axle 35 more effectively.

  In addition, as the speed reduction mechanism 38 of the drive unit 15 in the present embodiment, the above-described two-stage reduction type planetary gear mechanism is shown, but is not limited to this, for example, a two-stage reduction type parallel gear mechanism. A gear mechanism may be used. Further, depending on the specification of the vehicle, a one-stage reduction type planetary gear mechanism may be used. Details of another embodiment of the speed reduction mechanism 38 will be described later.

Next, the brake mechanism 39 will be described below.
As shown in FIGS. 3, 7 and 8, a wet disc type brake mechanism 39 is provided between the speed reduction mechanism 38 and the center section 41, and the brake mechanism 39 is controlled by a brake pedal (not shown). Power operation is possible. When the brake pedal is depressed, the brake wire 49 connected to the brake pedal 49 and the brake arm 68 disposed above the housing 28 are pulled, the cam 63 is rotated, and the pressure plate 64 is slid in the axial direction. The friction plate 66 locked to the end portion of the output gear 65 is pressed, rotational resistance is applied to the output gear 65, and a braking action is generated on the axle 35.

Next, the tilting mechanism 40 of the movable swash plate 53 will be described below.
As shown in FIGS. 3, 7, 10 to 13, in the drive unit 15, the tilt mechanism that changes the tilt angle of the movable swash plate 53 of the first hydraulic motor 10 from the initial position to a predetermined volume reduction position. 40 is configured. A control shaft 69 is rotatably supported in the vertical direction on the upper surface of the upper half housing portion 28a, and a rotating arm 70 is fitted to the lower end of the control shaft 69 so as not to be relatively rotatable. The distal end portion of the rotating arm 70 is engaged with a convex portion 53 a that protrudes from the upper surface of the movable swash plate 53.

  A control arm 71 is fitted to the upper end of the control shaft 69 so as not to be relatively rotatable. The control arm 71 protrudes upward and then bends in parallel with the rotation direction of the housing 28 (the direction of the support 26). Thus, an input portion 71a is formed. The input portion 71a extends in two directions along the cam 26a provided on the outer peripheral surface of the support 26 and is curved in a substantially C shape in plan view. . The contact portion 71b at the tip of the input portion 71a is in contact with the outer peripheral surface of the cam 26a of the support 26.

  As shown in FIG. 10, the cam 26a of the support 26 is formed such that the distance L3 from the axis S to the outer peripheral surface is different at approximately 90 degree intervals. What is indicated by a two-dot chain line is for comparison purposes and is a perfect circle having a radius of the distance L3. That is, the outer peripheral edge of the cam 26a is formed such that the distances L3 are equal in length at positions P1 and P3 and positions P2 and P4 on the vertical line passing through the axis S. The distance L3 is formed to gradually decrease from the position P1 to the position P2 (counterclockwise), and a negative deviation ΔL is generated between the position P1 and the position P2. The distance L3 is formed so as to gradually increase from the position P3 to the position P4, and a positive deviation ΔL occurs with respect to the perfect circle. The distance L3 is gradually decreased from the position P1 to the position P4 (clockwise), and a negative deviation ΔL is generated between the position P1 and the position P4. The distance L3 is formed so as to gradually increase from the position P3 to the position P2, and a positive deviation ΔL occurs with respect to the perfect circle. These four deviations ΔL have substantially the same length in this embodiment. One of the contact portions 71b at the tip of the input portion 71a is in sliding contact from the position P1 to the position P2 and from position P1 to the position P4, and the other contact portion 71b is from the position P3. The sliding contact is made between the position P4 and between the position P3 and the position P2. A step 26b is formed at the positions P2 and P4.

  At the outer peripheral edge of the cam 26a, the central angular region from the position P1 to the position P4 and the central angular region from the position P3 to the position P2 are the outer peripheral central angular region of the front wheels, and from the position P1 to the position P2 direction. If the central angle region to the center and the central angle region from the position P3 to the position P4 is the inner-cut central angle region of the front wheel, the inner-cut central angle region is larger than the outer-cut central angle region. Is formed. In this way, the outer peripheral edge of the cam 26a is formed to have a different central angle region, so that it is possible to easily cope with different turning angles depending on the outer cut and inner cut of the drive units 15L and 15R based on the Ackermann-Jant mechanism. Can be made.

  As shown in FIG. 13A, when the swash plate angle of the movable swash plate 53 is in the neutral position, the contact portion 71b of the control arm 71 is contacted at the outer peripheral surface positions P1 and P3 of the cam 26a. ing. When the handle 16 is cut, the king pin 27 and the housing 28 are rotated by the turning angle by the steering gear mechanism 17. Since the control arm 71 is fitted to a control shaft 69 projecting from the housing 28, the distance L4 from the axis S to the control shaft 69 is maintained in conjunction with the rotation of the housing 28. Then, it is rotated relative to the cam 26a. Then, the corresponding contact portion 71b is rotated along the outer peripheral surface of the cam 26a, and the control arm 71 is always rotated in one direction with the control shaft 69 as the rotation center regardless of the direction in which the handle 16 is cut. (Hereinafter, this direction is referred to as X direction).

  Specifically, as shown in FIG. 13B, when the handle 16 is rotated to the left, the drive unit 15L is cut off and the corresponding contact portion 71b is moved from the position P1 (position 3). It is rotated in the direction of the position P2 (position 4), and is brought into contact with the step 26b when the inner limit is cut. The cam 26a is formed such that the distance L3 gradually decreases from the position P1 to the position P2, and is formed so that the distance L3 gradually increases from the position P3 to the position P4. It is gradually rotated in the X direction about the control shaft 69 by a deviation ΔL through the contact portion 71b. When the control arm 71 is rotated in the X direction, the rotation arm 70 is rotated in conjunction with the control shaft 69, and the angle of the swash plate 53 of the movable swash plate 53 is adjusted by the rotation arm 70. Tilt to decrease.

  On the other hand, as shown in FIG. 13C, when the handle 16 is rotated to the right, the drive unit 15L is disconnected and the corresponding contact portion 71b is moved from the position P1 (position 3) to the position P4 (position 2) It is rotated in the direction. The cam 26a is formed so that the distance L3 gradually decreases from the position P1 to the position P4, and is formed so that the distance L3 gradually increases from the position P3 to the position P2. It is gradually rotated in the X direction through the contact portion 71b around the control shaft 69 by the deviation ΔL, as in the case of the inner cut. Similarly, as the control arm 71 rotates, the movable swash plate 53 is tilted so that the swash plate angle becomes smaller.

  In addition, in the present embodiment, the same deviation amount ΔL appears at the inner edge and the outer edge of the cam 26a in the present embodiment. The volume of the hydraulic motor 10 is reduced at the same rate, and the wheel rotation difference between the turning inner side and the turning outer side is absorbed by the hydraulic differential effect of the left and right first hydraulic motors 10. If the outer peripheral edge shape of the cam 26a is formed such that a difference ΔL appears between the inner cut and the outer cut, the left turn and the right turn of the first hydraulic motor 10 are independent. , Each volume reduction rate can be changed. That is, the speed increase rate is reduced for the first hydraulic motor 10 on the inside of the turn, whereas the ratio is increased in the first hydraulic motor 10 on the outside of the turn to positively generate a wheel rotation difference. It is also possible to do so.

  As described above, when the housing 28 is steered to the left and right from the straight movement position, the relative displacement amount with respect to the support portion 26 of the vehicle frame 2 with respect to the straight movement position of the housing 28 is automatically set as the first hydraulic motor. Since the swash plate angle of the movable swash plate 53 is converted to an operation amount that reduces the swash plate angle, the steering wheel of the work vehicle 1 is adapted to the ideal turning speed when turning, and the steering operation described above is performed. Sex is further enhanced.

Next, the rear wheels 79 and 79 that are non-steering wheels will be described below.
As shown in FIG. 14, a pair of left and right drive units 15L and 15R each having a rear wheel 79, which is a traveling drive wheel, are disposed so that their positions cannot be changed. A housing 76 of the drive units 15L and 15R is located behind the vehicle frame 2 and on the side of the rear discharge duct 74 via a bracket 77 that is substantially L-shaped in front view. It is fixed with screws by bolts 86 and 87. The upper half housing portion 76a and the lower half housing portion 76b are brought into contact with each other through a joint surface and fixed with screws by bolts 88. The housing 76 is disposed such that the joint surface is substantially horizontal in a state where the drive unit 13 is disposed at the operating position. The axle 78 is supported in the horizontal direction by bearing support portions 84 and 84 disposed in the housing 76, and one end of the axle 78 projects from one side of the housing 76 toward the outside of the work vehicle 1. The rear wheel 79 is fixed to the protruding portion.

  In the housing 76, a variable displacement type second hydraulic motor 80, a speed reduction mechanism 81, a brake mechanism 82, a movable swash plate 73, a tilting mechanism 83 thereof, and the like are arranged. The configurations of the speed reduction mechanism 81, the brake mechanism 82, and the tilting mechanism 83 are the same as those in the drive unit 15 described above, and a description thereof is omitted. The second hydraulic motor 80 may be a fixed displacement type, but in this embodiment, a variable displacement type is used for the reason described later, and the tilt mechanism 83 is controlled by the external actuator 101. Further, axle rotation speed sensors 102 and 102 are disposed in the vicinity of the axles 78 and 78 of the left and right drive units 13L and 13R, respectively, and the axle rotation speed sensors 102 and 102 are connected to a controller 107 described later. (See FIG. 17).

  In order to drive the rear wheel 79, in addition to using each of the separate driving units 13 provided with the second hydraulic motor 80, for example, an HST driving device having a mechanical differential mechanism is provided, It is good also as a structure which transmits the drive from the engine 3 to the rear-wheel 79 via a differential mechanism. Details will be described later (see FIGS. 18 and 21). Alternatively, the rear wheel 79 may be a steering wheel, and the rear wheel 79 may be steered by the handle 16 (four-wheel steering) as with the front wheel. Details will be described later (see FIGS. 19 and 26).

  The housing 76 may be shared with the steering wheel housing 28. Specifically, a mount boss portion that is common to the shape of the mount boss portion 29 of the housing 28 is formed in the housing 76. By adopting such a shape, the king pin 27 can be attached when used for a steered wheel, or the bracket 77 can be attached when used for a non-steered wheel. Covered by the drive unit, it is possible to reduce production costs by sharing parts.

Next, a traveling hydraulic circuit of the work vehicle 1 will be described below.
In the hydraulic circuit shown in FIG. 15, a first circuit 89 for connecting the first hydraulic motors 10 and 10 to the hydraulic pump 5 is formed in each drive unit 15L and 15R of the steered wheels. In each of the drive units 13L and 13R, a second circuit 90 for connecting the second hydraulic motors 80 and 80 to the hydraulic pump 5 is formed. A hydraulic oil supply charge pump 94 and a relief valve 95 are connected to an oil supply / discharge circuit 91 in which the hydraulic pump 5 is disposed via a pair of check valves 96 and 96. The oil supply / discharge circuit 91 is connected to the first circuit 89 and the second circuit 90 via a shift switching valve 92. The first circuit 89 has a pair of main oil passages 89a and 89b that connect the first hydraulic motors 10 and 10 in parallel to each other, and the second circuit 90 connects the second hydraulic motors 80 and 80 in parallel to each other. A pair of main oil passages 90a and 90b is provided.

  Both the main oil passages 89 a and 89 b of the first circuit 89 are connected to the shift switching valve 92. One of the main oil passages 90 b of the second circuit 90 is connected to the shift switching valve 92, and the other 90 a of the second circuit 90 is connected to one side of the oil supply / discharge circuit 91 via the oil passage 100. It is connected. Forward and reverse flow control valves 98 and 99 are disposed on the suction side and suction side of the first hydraulic motor 10 and the second hydraulic motor 80, respectively, and by changing the current value to the electric step motors 98a and 99a. The opening degree of the throttle passage inside the valve is mechanically changed, and the flow rate of the oil fed to the first hydraulic motor 10 and the second hydraulic motor 80 is adjusted. The step motors 98a and 99a are connected to the controller 107. When the vehicle moves forward, only the step motor 99a operates to cause the flow rate control valve 99 to function, and the flow rate control valve 98 does not function. Only the motor 99b is operated to control the flow control valve 98, and the flow control valve 99 is controlled not to function (see FIG. 15).

  Between the suction side and the suction side of each first hydraulic motor 10 and second hydraulic motor 80, traction bypass valves 108, 108,. The first hydraulic motor 10 and the second hydraulic motor 80 can be idled by switching the bypass valve 108. When the work vehicle 1 is towed, the first hydraulic motor 10 and the second hydraulic motor 80 act as pumps via the front wheels 36 and 36 and the rear wheels 79 and 79, and the oil flow at that time is The self-circulation is made through the bypass valve 108 and does not reach the hydraulic pump 5 side. As a result, the front wheels 36 and 36 and the rear wheels 79 and 79 can idle with a light force, and the towing operation can be easily performed.

Next, the shift switching valve 92 of the hydraulic circuit will be described in detail below.
As shown in FIG. 15, the shift switching valve 92 is a manual valve that is mechanically linked and interlocked with a switching operation means 93 such as a pedal, and can be switched in three stages in this embodiment. The switching operation means 93 may be switched by a hydraulic actuator or the like for ease of operation and control.

  When the shift switching valve 92 is operated to the position L by the switching operation means 93, the first circuit 89 and the second circuit 90 are connected in parallel. That is, the hydraulic pump 5 is set so as to be discharged from the port on the left side of the sheet when the vehicle moves forward, and the pressure oil discharged from the hydraulic pump 5 is supplied to the first through the shift switching valve 92 and the oil passage 100. They are sent to the main oil passage 89a of the circuit 89 and the main oil passage 90a of the second circuit 90 so as to be distributed. The return oil after driving the first and second hydraulic motors 10 and 80 is collected in the shift switching valve 92 from the main oil passages 89b and 90b and sucked into the hydraulic pump 5. In such a case, the left and right front wheels 36 and 36 and the rear wheels 79 and 79 are driven, and the work vehicle 1 is optimal for heavy traction work and can be driven at a low speed with four-wheel drive excellent in climbing performance.

  When the shift switching valve 92 is operated to the position M, the first circuit 89 and the second circuit 90 are connected in series. That is, the pressure oil from the hydraulic pump 5 is discharged from the port on the left side of the page when the vehicle moves forward. First, the oil supply / discharge circuit 91 passes through the oil passage 100 to the main oil passage 90a of the second circuit 90. After the second hydraulic motor 80 is driven, it is sent to the main oil passage 89a of the first circuit 89 via the gear change valve 92, and after the first hydraulic motor 10 is driven, the speed is changed from the main oil passage 89b. It is sucked into the hydraulic pump 5 through the switching valve 92. In such a case, the left and right front wheels 36 and 36 and the rear wheels 79 and 79 are driven, but the work vehicle 1 is faster and more efficient in operation than the case where the above-described shift switching valve 92 is operated to the position L. Medium speed running with four-wheel drive is possible. When the first circuit 89 and the second circuit 90 are connected in series rather than being connected in parallel, the total amount of oil discharged from the hydraulic pump 5 is transferred to the first hydraulic motor 10 and the second hydraulic motor. This is because it can be sent to 80.

  When the shift switching valve 92 is operated from the position L or the position M to the position H, the oil supply to the first circuit 89 is stopped, and the oil supply / discharge circuit 91 and the second circuit are stopped. 90 is connected through a shift switching valve 92. That is, the pressure oil from the hydraulic pump 5 is sent to the shift switching valve 92 via the second circuit 90, and the two-wheel drive is performed by driving only the rear wheels 79 and 79. Oil circulation when the first hydraulic motor 10 that is not sent to the first circuit 89 and stops driving is pumped during travel is permitted via the shift switching valve 92. 89c is an oil replenishment check valve for preventing negative pressure in the circuit due to oil leakage at various points when oil circulates in the first circuit 89.

  As long as it is sufficient to provide the four-wheel drive / two-wheel drive switching function at the position H of the shift switching valve 92, the second hydraulic motor 80 does not need to use a variable displacement type as described later. In this embodiment, it is detected that the shift switching valve 92 has been operated to the position H by the sensor 103 disposed in the vicinity of the switching operation means 93 in order to obtain another shift number at the position H. The Then, the external actuator 101 is tilted so that the swash plate angle of the movable swash plate 73 of the second hydraulic motors 80 and 80 in the tilt mechanism 83 is decreased at the same rate, and the above-described shift switching valve 92 is moved to the position L. It becomes faster than the traveling speed when operated to the position M, and economical high-speed traveling by two-wheel drive becomes possible. The switching operation means 93 and the tilt mechanism 83 may be mechanically linked using a rod, a wire, or the like without using the external actuator 101.

  In this way, hydraulic circuits that can supply oil from the hydraulic pump 5 to the first hydraulic motor 10 and the second hydraulic motor 80 disposed in the drive units 13 and 15 are formed. Therefore, by controlling the pressure oil delivered from the hydraulic pump 5, the driving speeds of the left and right front wheels 36 and 36 and the rear wheels 79 and 79 can be easily increased or decreased or differentially driven. Further, since the first and second hydraulic motors 10 and 80 are respectively connected to the hydraulic pump 5, they can be easily driven four-wheels by hydraulic pressure.

  Further, since the operation of the discharge oil amount and the discharge direction of the hydraulic pump 5 can be performed continuously, it is used as a main transmission that can be operated during traveling, and the first hydraulic motor 10 and the second hydraulic motor are operated by the shift switching valve 92. The driving speed of the left and right front wheels 36 and 36 and the rear wheels 79 and 79 is comprehensively changed by stepwise switching the oil flow rate to 80 and selecting a speed range according to the driving situation. Can be changed over a wide range. In this embodiment, when the hydraulic pump 5, the first hydraulic motor 10, and the second hydraulic motor 80 are connected in series, the oil discharged from the hydraulic pump 5 when the vehicle moves forward is driven first by the rear wheels. However, due to the characteristics of the vehicle, the rear wheels are firmly installed on the road surface even when the front wheels are lifted up at the time of sudden start. This is to improve the running stability.

  In particular, the work vehicle 1 can be easily switched from four-wheel drive to two-wheel (rear wheel) drive by switching so that oil is fed only into the second circuit 90. In this embodiment, the oil in the hydraulic circuit is sent only to the second hydraulic motor 80 and tilted so that the swash plate angle of the movable swash plate of the second hydraulic motor 80 is smaller than that in the case of four-wheel drive. Thus, the driving speed of the rear wheels 79 and 79 is increased. For this reason, the traveling performance of the work vehicle 1 is enhanced by high-speed traveling by two-wheel drive. For example, when such switching is instantaneously performed when traveling on a flat ground, the traveling time is shortened and the working efficiency is good.

Here, the hydraulic control by the controller 107 will be described in detail below.
As shown in FIG. 17, in addition to the pair of front and rear step motors 98a and 99a, the differential lock pedal 105, a sensor disposed in the vicinity of the main transmission pedal 106, an axle rotation speed sensor 102, a steering angle sensor 104, and the like. , Connected to the controller 107. The controller 107 has a storage function for data related to control and a program, a development function and an arithmetic function for executing the data and program, and specifically, a CPU, a ROM, a RAM, and the like are connected by a bus. Alternatively, it may be a single-chip LSI or the like having all the above functions.

  An electrically operated flow control valve 98 capable of independently restricting the amount of flow into the left and right of the first hydraulic motors 10 and 10 and the right and left of the second hydraulic motors 80 and 80 and controlling their rotational speeds. By providing 99 in the first and second circuits 89 and 90, the rotational speeds of the left and right sides of the first hydraulic motors 10 and 10 and the left and right sides of the second hydraulic motors 80 and 80 can be varied according to the vehicle. It can be controlled according to various situations.

  An example of the control means by the controller 107 will be described. There is a differential lock function for controlling the left and right front wheels 36 and 36 and the rear wheels 79 and 79 so that the rotational speeds are forcibly made equal. That is, when the controller 107 detects that the diff lock pedal 105 has been depressed (diff lock “ON”) by the operator when the vehicle moves forward, the step motor 99a is driven, and the first hydraulic motor 10. The oil flow rates to the left and right of each of the 10 and the left and right of the second hydraulic motors 80 and 80 make the rotation speeds of the left and right axles 35 and 78 equal based on the feedback signals of the axle rotation speed sensors 102, 102. Thus, the left and right front wheels 36 and 36 and the rear wheels 79 and 79 are differentially locked. During forward travel, the throttle effects of all the flow control valves 98 and 99 have disappeared, and the left and right sides of the first hydraulic motors 10 and 10 and the second hydraulic motors 80 and 80 are in accordance with the load acting on the left and right front and rear wheels. A hydraulic differential function appears on each of the left and right sides.

  Here, for example, when one wheel is removed, the load on the one wheel is lightened and the amount of oil flowing into the first hydraulic motor 10 is increased, and the oil flowing into the first hydraulic motor 10 on the other wheel is eliminated and the left front wheel. Stops rotating. At this time, if the diff-lock pedal 105 is depressed, the controller 107 causes the flow control valve 99 to inject oil into the first hydraulic motor 10 on the light load side according to the degree of slip, based on the actually measured rotational difference between the left and right axles. The first hydraulic motor 10 on the high load side is rotated by rotating the front wheels by causing the throttle effect to appear so as to force the oil to flow into the first hydraulic motor 10 on the high load side. Control of the flow control valve 99 is continued while changing the throttle degree until the difference becomes substantially zero.

  Such flow control valves 98 and 99 can also exhibit a limited slip differential function by detecting the steering angle and the rotational speeds of the left and right front wheels. This is based on the rotation difference between the left front wheel 36L and the right front wheel 36R based on the difference between the turning radius of the left front wheel and the turning radius of the right front wheel from the turning center point 110 of the work vehicle 1 corresponding to the detected steering angle. The controller 107 can determine the one-wheel slip turning state of the work vehicle 1 by comparing the measured value with the measured value of the axle rotation speed sensor 102, and the throttle effect of the flow control valves 98 and 99 is the same as described above. The oil inflow to the first hydraulic motor 10 on the slipping side is made to appear depending on the degree of slip, and the oil is forced to flow into the first hydraulic motor 10 on the high load side, Wheel driving can be continued during turning on any road surface.

  In the present embodiment, each of the flow control valves 98 and 99 has two variable throttle passages and a combination of step motors 98a and 99a capable of controlling the degree of throttling in contradiction. The two hydraulic motors 10, 10, 80, and 80 are each connected to the hydraulic pump side in parallel to the left and right to make two total, but as shown in FIG. A total of four flow regulating valves 109 having two variable throttle passages and provided with a step motor 109a for controlling the throttle degree may be used on the suction side and the discharge side of the first hydraulic motors 10 and 10, respectively. Although not shown, the circuits of the second hydraulic motors 80 and 80 are the same.

(Second embodiment)
As shown in FIGS. 18 to 21, the work vehicle 1 according to the present embodiment includes a pair of left and right drive units 15 </ b> L and 15 </ b> R according to the present invention, each having a front wheel 36 in front of the vehicle frame 2. An axle driving device 114 including a single second hydraulic motor 115 and a mechanical differential gear mechanism 113 for driving the rear wheel 119 is suspended behind the vehicle frame 2.

  As shown in FIG. 18, a rear axle case 117 is fixed to the rear of the vehicle frame 2, and in the rear axle case 117, a hydraulic pump 5, a second hydraulic motor 115, a reduction gear mechanism 118, a mechanical A differential gear mechanism 113 with a differential lock and a pair of left and right axles 116 connected by the differential gear mechanism 113 are disposed. The hydraulic pump 5 is driven by an engine 3 (not shown) disposed in the vicinity of the rear axle case 117, and an output shaft 115a of a second hydraulic motor 115 fluidly connected to the hydraulic pump 5 The gear mechanism 118 is connected. The axle 116 projects from the side surface of the axle drive device 114 in the left-right direction of the vehicle frame 2, and rear wheels 119 are fixed to both ends of the projecting portion. The drive by the second hydraulic motor 115 is transmitted to the differential gear mechanism 113 via the reduction gear mechanism 118 and to the axle 116 and the rear wheel 119.

  The pair of left and right drive units 15L and 15R have their maximum steering angles set so that the turning center point 110 appears on the rear wheel 119 inside the turning when the handle 16 is fully cut. Therefore, the structure of the drive units 15L and 15R (particularly the shape of the cam 26a not shown) is the same as that of the first embodiment described above, and when turning, the turning radius 112a on the rear wheel 119 side and the turning radius 111a on the front wheel 36 side. The rotational speed of the first hydraulic motor 10 is increased more than the second hydraulic motor 115 at a rate commensurate with the turning radius difference.

  Thus, the steering wheel drive unit 15 according to the present embodiment is also applied to a two-wheel steering / four-wheel drive vehicle equipped with the axle drive device 114 having the mechanical differential gear mechanism 113, and the turning thereof. Performance and running performance can be improved.

  The work vehicle 1 shown in FIG. 19 has a four-wheel steering / four-wheel drive type in which steering wheels capable of rotating the rear wheels 119 and 119 in the left-right direction are formed at both ends of the axle 116 of the axle drive device 114. It is said. Such a steered wheel has a front wheel 36 and a rear wheel 119 swinging left and right via a steering link mechanism (not shown) connected to an axle stay 123 fixed to the vehicle frame 2 so as not to be relatively rotatable. The front wheels 36 and 36 are turned to the same left and right sides corresponding to the turning direction of the handle 16, and the rear wheels 119 and 119 are turned to the side opposite to the turning direction of the handle 16. The linkage structure is as follows.

  With such a configuration, the turning center point 110 appears between the front wheel 36 and the rear wheel 119 when the handle 16 is fully cut as compared with the work vehicle 1 shown in FIG. The difference between 111a and the turning radius 112a of the rear wheel 119 is small, and the work vehicle 1 turns with a small turn. The cam 26a (not shown) used for the drive units 15L and 15R is the second hydraulic motor 115 at an optimum ratio corresponding to the turning radius difference between the turning radius 112a on the rear wheel 119 side and the turning radius 111a on the front wheel 36 side during turning. Instead, the shape is set so as to increase the rotational speed of the first hydraulic motor 10. Since the axle stay 123 is fixed to the vehicle frame 2, the rotation angle of the rear wheel 119 in the left-right direction is limited to a range in which the rear wheel 119 does not contact the vehicle frame 2. The turning center point 110 is not located inward of the vehicle body than the wheel 36 (119) inside the turning and does not turn the interlining.

  In the work vehicle 1 shown in FIG. 20, the hydraulic pump 5 is arranged outside the axle drive device 114. If the hydraulic pump 5 is arranged in the axle drive device 114, the shape of the engine 3 used and the layout of the axle drive device 114 are limited in order to connect the engine 3 and the hydraulic pump 5. It had been. Therefore, with this configuration, the hydraulic pump 5 can be freely arranged according to the direction (horizontal / vertical) of the output shaft of the engine 3, and the axle drive device 114 is equipped with a first one. The two hydraulic motors 115 may be connected using external piping that can be easily deformed. This layout can also be applied to the four-wheel steering / four-wheel drive work vehicle according to FIG.

  In the above embodiment, the steering wheel drive units 15L and 15R individually including the first hydraulic motors 10 and 10 according to the present invention are arranged on the front and rear sides of the work vehicle, and further, a single side is provided on the front and rear sides. An axle driving device 114 including a second hydraulic motor 115 and a mechanical differential gear mechanism 113 is disposed. A hydraulic circuit for fluidly connecting the main oil passages 89a and 89b of the first hydraulic motors 10 and 10 and the main oil passages 172a and 172b of the second hydraulic motor 115 to the hydraulic pump 5 is shown in FIG. As described above, the components that are substantially the same as those in FIG. 15 and that have the same functions are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 32, in the hydraulic circuit of the work vehicle 1, a first circuit 89 is formed between the hydraulic pump 5 and the first hydraulic motors 10 and 10, and the hydraulic pump 5 and the second hydraulic motor 115 are formed. The second circuit 120 is formed between the two. The first circuit 89 and the second circuit 120 are connected via the shift switching valve 92. In this embodiment, the first circuit 89 does not show the forward / reverse flow control valves 98 and 99 for the sake of convenience, but will be described with reference to FIGS. 15 and 16 if necessary. Such flow control valves 98 and 99 may be provided so that the differential lock acts on the front wheel 36.

  The pair of first hydraulic motors 10 on the front wheel 36 side and one second hydraulic motor 115 on the rear wheel 119 side are connected in series or in parallel with the hydraulic pump 5 by switching the shift switching valve 92 to the position L and the position M. The first and second motors 10 and 115 are synchronized to output different rotations. When the shift switching valve 92 is operated to the position H, the oil from the hydraulic pump 5 flows into only the second circuit 120, and the two-wheel drive is performed in which only the rear wheels 119 and 119 are driven. At the same time, when such a switching operation is detected by the sensor 103, the swash plate of the movable swash plate 121 of the second hydraulic motor 115 is detected by the external actuator 101 connected to the movable swash plate 121 of the second hydraulic motor 115. Tilts are made to reduce the angle, and the driving speed of the rear wheels 119 and 119 is increased.

  The steering wheel drive unit 15 shown in FIG. 22 has a support 141 and a kingpin 142 etc. that are shorter in the vertical length than the support 26 and the kingpin 27 etc. in the first embodiment. The configured drive unit 15 is configured to be located on the side of the vehicle frame 2.

  A support bracket 138 having a substantially L-shape when viewed from the front is screwed and fixed to the inside of the vehicle frame 2 (to the right in FIG. 22) by a bolt 138a, and the fulcrum pin 23 of the drive gear 22 is pivoted to the support bracket 138. It is installed. On the other hand, a substantially U-shaped support frame 139 is fixed to the outside of the vehicle frame 2 with screws. An upper horizontal surface 139a of the support frame 139 is fixed to the support body 141, and a lower horizontal surface 139b is pivotally supported by a pivot bolt 140 from below the lower half housing portion 28b so as to be relatively rotatable. The pivot bolt 140 and the king pin 142 are configured to have a coaxial core, and the king pin 142 and the housing 28 are rotatable relative to the support frame 139 and the support 141 fixed to the support frame 139. Two points are supported.

  The support 141 has a solid king pin 142 inserted from below in a substantially vertical direction so as to be relatively rotatable. The driven gear 30 is fitted to the upper end portion of the king pin 142 so as not to be relatively rotatable, and the housing 28 is fixed to the lower end portion of the king pin 142. The housing 28 is provided with the speed reduction mechanism 38, the brake mechanism 39, the tilting mechanism 40 of the movable swash plate 53, and the like.

  By adopting such a configuration, the vertical height of the work vehicle 1 can be lowered, and the work vehicle 1 can be made compact and have good running stability due to the low center of gravity. On the other hand, since the housing 28 and the like are pivotally supported by the support frame 139, the left and right turning angles of the front wheels 36 and 36 are limited. However, when the work vehicle 1 is formed in a small size, the vehicle itself is compact so that it can be turned slightly and does not impair the left-right turning performance of the steered wheels. Rather, a plurality of housings 28 and the like are provided. Since it is pivotally supported at a point (two points in the present embodiment), the stability and smoothness during the turning are improved.

  In the solid king pin 142, four through-holes 143, 144, 145 are formed along the upper and lower longitudinal directions, and among these, three lower opening ends have pipe joints 143a, 144a. The pipe joints 46a, 47a, and 48a screwed to the upper surface of the housing 28 are connected through the short oil pipes 47 and 48 and the drain conduit 46 as in FIGS. 9 and 12 described above. Pipe joints 143b, 144b, and 145b are screwed to the upper opening ends of the through holes 143, 144, and 145 in the king pin 142, and the hydraulic pump 5 is fluidly connected to two of them, and the remaining one Is connected to an oil tank (not shown). A brake wire 49 connected to the brake pedal is inserted into the remaining one through hole and connected to the brake arm 68 on the upper surface of the housing 28. The use of such a through hole provided in the king pin 142 as an oil passage may be applied to the long king pin 27 shown in FIG.

  The steering wheel drive unit 15 shown in FIGS. 23 to 25 includes a two-stage reduction type parallel gear mechanism with a small number of parts and a low cost as the reduction mechanism 38 in the drive unit 15.

  The first hydraulic motor 10 is disposed in the housing 124, and the motor shaft 56 is fitted to the cylinder block 51 of the first hydraulic motor 10. On the other hand, the axle 35 is supported by bearing support portions 67 and 67 in the left-right direction of the housing 124, the motor shaft 56 is loosely fitted to the axle 35, and the output gear 65 is spline-fitted to the motor shaft 56. . A reduction shaft 146 is disposed so as to be substantially parallel to the axle 35, and a fixed gear 147 is fixed to the reduction shaft 146. A gear 148 is spline-fitted to one end of the fixed gear 147, and the gear 148 is engaged with the output gear 65. The other end of the fixed gear 147 is engaged with a final reduction gear 149 that is spline-fitted to the end of the axle 35.

  In such a configuration, the cylinder block 51 driven to rotate by the first hydraulic motor 10 is driven by the cylinder block 51 → the motor shaft 56 → the output gear 65 → the gear 148 → the fixed gear 147 → the final reduction gear 149 → the axle. It is transmitted to 35-> front wheel 36, and work vehicle 1 can run.

  A brake mechanism 39 is disposed behind the speed reduction mechanism 38 and in the vicinity of the gear 148. The brake mechanism 39 can be operated with a braking force by a hand brake (not shown). In the brake mechanism 39, the cam 152 is operated and the pressure plate 153 is slid through the brake wire 150 connected to the hand brake and the brake arm 151 disposed above the housing 124. When such a hand brake is operated, a thrust in the left direction is generated, and the pressure plate 153 applies resistance to the gear 148 to generate a braking action.

  With the configuration as described above, the number of parts is small and processing is easy and the manufacturing cost can be reduced as compared with the case where a planetary gear mechanism is provided as the speed reduction mechanism 38. Further, the housing 124 in the present embodiment is shorter in the longitudinal direction, and further, the inner side can be formed shorter in the shorter direction than the outer side. Therefore, each drive unit 15 can be made more compact and its turning performance can be improved. The speed reduction mechanism 38 using the parallel gear mechanism may be applied not only to the drive unit 15 in the front wheel but also to the drive unit 13 in the rear wheel.

(Third embodiment)
As shown in FIGS. 26 and 27, the work vehicle 1 according to the present embodiment should be a four-wheel steering / four-wheel drive type by applying the steering wheel drive unit according to the present invention to both the front and rear wheels. In front of the vehicle frame 2, a pair of left and right drive units 15L and 15R each having a front wheel 36 as a steering wheel are disposed so as to be steerable (left and right rotation), and a rear portion of the vehicle frame 2 is provided. A pair of left and right drive units 157L and 157R each having a rear wheel 167, which is a steered wheel, are disposed so as to be steerable (right and left). Furthermore, the drive unit 157 includes an axle 164 and a second hydraulic motor 165 for driving the axle 164 in the housing 166. In other words, the work vehicle 1 has steering wheels formed in the front and rear of the vehicle frame 2 so that the front wheels 36 and the rear wheels 167 can be independently driven, and the front link 36 and the rear wheels are driven by the steering link mechanism 18. 167 is steered so as to be rotatable relative to the vehicle frame 2. By adopting such a structure, the work vehicle 1 can turn with an excellent small turning radius while maintaining a very good balance, and further turn the outer handle to the maximum to turn the interlining as shown in FIG. It is set so that.

  In the work vehicle 1, a mower 44 having three cutting blades 44 a, 44 a, and 44 a is supported at the front portion of the vehicle frame 2 (front mount mower). The mower 44 is driven by the engine 3. They are connected via a belt 85.

  As shown in FIGS. 26 and 27, in the front-rear direction of the left and right vehicle frames 2, a cross member 14 extending in the left-right direction is laterally provided at the front portion of the vehicle frame 2, and a steering wheel is provided at each of the end portions. The drive units 15L and 15R of the front wheel 36 are suspended so as to be steerable. The left and right steering gear mechanisms 17 for interlockingly connecting the front wheels 36 to the handle 16 are formed as in FIG. A cross member 156 that extends in the left-right direction of the rear portion of the vehicle frame 2 is provided in a laterally symmetrical manner, and drive units 157L and 157R of a rear wheel 167 serving as a steering wheel can be steered at both left and right ends of the cross member 156. Has been. A left and right steering gear mechanism 155 is formed to interlock the rear wheel 167 with the handle 16.

  The steering gear mechanism 155 has a fan-shaped gear as a drive gear 158 at a position opposite to the left and right above the cross member 156, with a substantially vertical fulcrum pin 159 in a state where the tooth circumference is directed left and right. Each is pivotally supported so as to be horizontally rotatable. A pivot joint 160 is attached to each inner end of the drive gear 158. Of the left and right rods 161, one end of which is pivotally connected to the steering link 20, the rod 161L is the right drive gear 158R. The rod 161R is pivotally connected to the left drive gear 158L via a pivot joint 160 in a cross shape.

  As shown in FIG. 28, a support member 162 of a king pin 27 is fixed to each of the left and right ends of the cross member 156, and a cylindrical king pin 27 opened up and down is attached to the support member 162 in the left and right direction. It is movably inserted from below. The king pin 27 is connected to the housing 166 below the support 162. At the upper end of the king pin 27, a fan-shaped gear as the driven gear 163 is fitted over the support body 26. A toothed portion on the inner side of the driven gear 163 is engaged with a toothed portion on the outer side of the drive gear 158, and the king pin 27 is pivoted substantially horizontally integrally with the driven gear 163 as a pivot of the driven gear 163. The

  The drive units 157L and 157R have the same configuration as that of the drive units 15R and 15L. That is, a housing 166 in which a second hydraulic motor 165 for driving the axle 164 is disposed is integrally fixed below the king pin 27 pivotally supported by the support body 26. Therefore, the drive unit 157 is substantially the same as the drive unit 15 of the front wheel 36.

  In FIG. 27, when the handle 16 is rotated leftward, the steering link 20 is tilted in the same direction, the rod 25L is pulled backward, the rod 25R is pushed forward, and the front wheel 36 is moved to the left. It is turned. At the same time, the rod 161R is pushed forward, the rod 161L is pulled backward, and the rear wheel 167 is turned to the right. That is, when the handle 16 is rotated to the left or right from the neutral position (the straight traveling position of the work vehicle 1), the front wheel 36 is turned left and right on the same left and right sides corresponding to the rotation direction of the handle 16, and the rear The wheel 167 is turned left and right in the direction opposite to the turning direction of the handle 16.

  The steering gear mechanisms 17 and 155 are configured such that the shapes of the drive gears 22 and 158 and the driven gears 30 and 163 are non-circular gears, thereby providing left and right turning angles to the inner and outer wheels, and the front wheels 36 and the rear wheels 167. Among them, an Ackerman-Jant mechanism is employed in which the left and right pivoting angle of the inner ring is larger than that of the outer ring, and the steerability of the left and right turn is enhanced. That is, the radius R1 of the drive gear 158 is longer than the radius R2 of the driven gear 163 regardless of the rotation direction and angle, and the drive gear 158 further changes its radius R1 as it rotates. The driven gear 163 is also shaped so that the radius R2 compensates for this.

  The front wheel 36 and the rear wheel 167 are rotated by the same angle although they are opposite to each other with respect to the rotation direction of the handle 16 by the rotation operation of the handle 16, and therefore the distance between the front wheel 36 and the rear wheel 167. The turning center point 110 appears at a substantially half position, and the turning radius 111a of the front wheel 36 and the turning radius 112a of the rear wheel 167 are turned to be equal. As described above, in this embodiment, since the rear wheel 167 that is a steering wheel is provided, the work vehicle 1 is excellent in turning performance, and is capable of small turning, sudden turning, and in-situ turning (zero turn).

  Specifically, as shown in FIG. 29, when the handle 16 is rotated to the left, the turning radius 111a of the front wheel 36 and the turning radius 112a of the rear wheel 167 are substantially equal. Compared to the case of the steered wheels (see FIG. 5), when the steering angle of the handle 16 is approximately the same, both the turning radius 111a of the front wheel 36 and the turning radius 112a of the rear wheel 167 are small. The swirlability is improved. Then, as shown in FIG. 30, when the handle 16 is rotated further leftward and reaches the maximum time, the turning radius 111a of the front wheel 36 and the turning radius 112a of the rear wheel 167 are substantially equal. The turning center point 110 moves to the vehicle frame 2 side (to the right in FIG. 30) and overlaps with the substantial center between the front and rear wheels and between the left and right wheels of the work vehicle 1. In such a case, the work vehicle 1 is zero-turned around the turning center point 110 without traveling in any direction.

Next, the tilting mechanism 40 of the movable swash plate 53 and the movable swash plate 171 will be described below.
As shown in FIGS. 28 and 32, the drive unit 157 of the rear wheel 167 includes a tilt mechanism 40 that changes the tilt angle of the movable swash plate 171 of the second hydraulic motor 165. The tilting mechanism 40 includes a support arm 162 cam 162a at a contact portion 71b at the tip of the input portion 71a. It is contact | abutted to the outer peripheral surface. When the king pin 166 is relatively rotated with respect to the support 162, the corresponding contact portion 71b of the control arm 71 is also rotated along the outer peripheral surface of the cam 162a. In this case, the control arm 71 is rotated about the control shaft 69 as a rotation center, and the movable swash plate 171 is tilted.

  Here, the front wheel 36 and the rear wheel 167 are rotated in directions opposite to the rotation direction of the handle 16, respectively. However, the turning radius 111a of the front wheel 36 and the turning radius 112a of the rear wheel 167 are substantially equal. Unlike the embodiment, it is not necessary to increase the driving speed of the front wheel 36 compared to the rear wheel 167 during turning. Therefore, the first and second hydraulic motors 10 and 165 may be fixed displacement types. On the other hand, if the hydraulic pump 5 is in a high discharge amount state when making a sudden turn or a zero turn, the front wheel 36 and the rear wheel 167 enter a turning posture in a high speed state, and stable turning cannot be performed. In such a case, the first and second hydraulic motors 10 and 165 can be easily dealt with by using the variable displacement type as follows. That is, the work vehicle 1 in this embodiment automatically adjusts the tilt angle of the movable swash plate 53 of the first hydraulic motor 10 and the tilt angle of the movable swash plate 171 of the second hydraulic motor 165 by the tilt mechanism 40 when turning. The driving speed of the front wheel 36 and the rear wheel 167 is changed to be reduced.

  As one form of such a configuration, as shown in FIGS. 31 and 32, the shape of the cam 170a in the support 170 of the drive unit 15 and the shape of the cam 162a in the support 162 of the drive unit 157 are formed as follows. The The cams 170a and 162a are formed such that the distances L3 are equal in length at positions P1 and P3 and positions P2 and P4 on the vertical line passing through the axis S, and from the position P1 to the position P2 (counterclockwise). The distance L3 is formed so that the distance L3 gradually increases, and the distance L3 is gradually decreased from the position P3 to the position P4. The distance L3 is gradually increased from the position P1 to the position P4 (clockwise), and the distance L3 is gradually decreased from the position P3 to the position P2. Steps 170b and 162b are formed at the positions P2 and P4.

  At the outer peripheral edge of the cam 170a, the central angular region from the position P1 to the position P4 and the central angular region from the position P3 to the position P2 are the outer peripheral central angular region of the front wheel, and from the position P1 to the position P2 direction. If the central angle region to the center and the central angle region from the position P3 to the position P4 is the inner-cut central angle region of the front wheel, the inner-cut central angle region is larger than the outer-cut central angle region. Is formed. On the other hand, the cam 162a is formed symmetrically with the cam 170a and is formed so that the outer cut center angle region is larger than the inner cut center angle region.

  As for the drive unit 15L on the front wheel side, as shown in FIGS. 33 (a) and 33 (b), the handle 16 rotates to the left from the state where the swash plate angle of the movable swash plate 53 is in the neutral position. Then, the drive unit 15L is cut off, and the corresponding contact portion 71b is rotated from the position P1 (position P3) to the position P2 (position P4). The control arm 71 is gradually rotated counterclockwise around the control shaft 69 (hereinafter, this direction is referred to as Y direction). When the control arm 71 is rotated in the Y direction, the movable swash plate 53 is tilted so that the swash plate angle increases. Further, as shown in FIG. 33 (c), when the handle 16 is rotated to the right, the drive unit 15L is disconnected and the corresponding contact portion 71b is moved from the position P1 (position P3) to the position P4 (position P2) is rotated in the direction. The control arm 71 is gradually rotated in the Y direction around the control shaft 69 as in the case of the inner end. As the control arm 71 rotates, the movable swash plate 53 is tilted so that the swash plate angle increases.

  On the other hand, with respect to the drive unit 157L on the rear wheel side, as shown in FIG. 34A, when the handle 16 is turned to the left from the state where the swash plate angle of the movable swash plate 171 is in the neutral position. The drive unit 157L is rotated in the opposite direction to the drive unit 15L. That is, as shown in FIG. 34B, the corresponding contact portion 71b is rotated from the position P1 (position P3) to the position P4 (position P2). The control arm 71 is rotated in the Y direction about the control shaft 69. When the control arm 71 is rotated in the Y direction, the movable swash plate 171 is tilted so as to increase the swash plate angle. As shown in FIG. 34 (c), when the handle 16 is rotated to the right, the corresponding contact portion 71b is rotated from the position P1 (position P3) to the position P2 (position P4), Similarly, the control arm 71 is gradually rotated in the Y direction around the control shaft 69. As the control arm 71 rotates, the movable swash plate 171 is tilted so that the swash plate angle increases.

  With the above-described configuration, the driving speed of both the front wheel 36 and the rear wheel 167 is automatically reduced without reducing the discharge amount of the hydraulic pump 5 by the turning operation of the handle 16. . Therefore, the sudden turn and zero turn of the work vehicle 1 can be stably performed, and the turnability of the work vehicle 1 can be further improved. The shapes of the cams 170a and 162a and the configuration of the tilt mechanism 40 of the movable swash plates 53 and 171 are not limited to this. By changing the shape of each of the cams 170a and 162a on the left and right sides, the tilting amount of the movable swash plates 53 and 171 and the oil flow rate to the first hydraulic motor 10 and the second hydraulic motor 165 are independently changed. Also good.

  In the present embodiment, the steering wheel drive units 15L and 15R each having the first hydraulic motors 10 and 10 according to the present invention are arranged on one side of the front and rear of the work vehicle 1, and further on the other side of the front and rear. Steering wheel drive units 157L and 157R having the same configuration including the hydraulic motors 165 and 165 are arranged symmetrically in the front-rear direction, and the main oil passages 89a and 89b of the first hydraulic motors 10 and 10 and the second hydraulic pressure are arranged. As shown in FIG. 35, the hydraulic circuit that fluidly connects the main oil passages 172a and 172b of the motors 165 and 165 to the hydraulic pump 5 is substantially the same as FIG. Reference numerals are assigned and explanations thereof are omitted. Therefore, if the shift switching valve 92 is at the position L shown in the figure, the low-speed four-wheel drive state in which the first hydraulic motor 10 and the second hydraulic motor 165 are connected in parallel to the hydraulic pump 5, or the position M The first hydraulic motor 10 and the second hydraulic motor 165 can be switched to the hydraulic pump 5 so as to be in a high-speed four-wheel drive state. When the shift switching valve 92 is switched to the position H, oil is circulated only in the second circuit 172, and two-wheel drive is performed by driving only the rear wheel 167.

  The first and second hydraulic motors 10 and 165 may be fixed displacement type as long as it is not necessary to change the speed in conjunction with the steering angle of the front and rear wheels as described above. If a variable displacement type interlocking with the shift switching valve 92 is employed on the second hydraulic motor 165 side, as in the case of FIG. 15 and FIG. 21, when the two-wheel drive state is set at the position H of the shift switching valve 92, The vehicle speed can be increased.

  36, the steering angle detected by the steering angle sensor 104 disposed in the vicinity of the handle 16, the rotational state of the front wheels 36 and the rear wheels 167 of the axle rotation speed sensors 102, 102,. The step motors 98a and 98a are driven in the same manner as in FIG. 17 on the basis of the traveling direction of the vehicle according to the depression direction of the speed change pedal 106 and the presence or absence of depression of the differential lock pedal 105, and the first hydraulic motor 10 and By limiting the flow rate of oil supplied to the second hydraulic motor 165, a hydraulic limited slip differential control function and a differential lock function are provided for the front wheels 36 and the rear wheels 167.

1 is a plan view showing an overall configuration of a work vehicle according to a first embodiment of the present invention. 1 is a schematic plan view of a steering mechanism used in the first embodiment. Front sectional drawing of the drive unit of the front wheel of the left-right one side. Brief description of the steering mechanism showing the turning state of the work vehicle. The top view showing the turning state of a work vehicle. The upper enlarged front sectional view of the front wheel drive unit. The lower enlarged front sectional view of the front wheel drive unit. AA arrow sectional drawing in FIG. BB sectional drawing in FIG. CC sectional view taken on the line in FIG. The top view of a control arm. The upper top view of a housing. Explanatory drawing of the control arm and support body accompanying steering of a front wheel. Front sectional drawing of the drive unit of a rear wheel. 1 is a hydraulic circuit diagram according to a first embodiment. The hydraulic circuit diagram which changed a part of hydraulic circuit diagram of FIG. Arrangement circuit diagram of sensors and the like. The top view which shows the whole structure of the working vehicle which concerns on the 2nd Example of this invention. The top view which changed the rear-wheel drive device of FIG. The top view which similarly changed the rear-wheel drive device of FIG. FIG. 3 is a hydraulic circuit diagram according to a second embodiment. The front sectional view which changed a part of steering wheel drive unit. The front sectional view which changed a part of steering wheel drive unit. DD sectional view taken on the line in FIG. The upper top view of a housing. The top view which shows the whole structure of the working vehicle which concerns on the 3rd Example of this invention. The schematic plan view of the steering mechanism used in the third embodiment. The front sectional view of the drive unit of the rear wheel on the left and right side. The top view showing the sudden turning state of a work vehicle. The top view showing the interlining turning state of a work vehicle similarly. EE arrow sectional drawing in FIG. Sectional drawing in the same position as the EE arrow in FIG. 28 of the drive unit of the other side rear wheel. FIG. 6 is a plan sectional view of a control arm and a support body that are accompanied by steering of the rear wheels. FIG. 3 is a plan sectional view of a control arm and a support body that are accompanied by steering of the front wheels. The hydraulic circuit figure concerning a 3rd example. Arrangement circuit diagram of sensors and the like.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Work vehicle 2 Vehicle frame 3 Engine 4 Mower 5 Hydraulic pump 10 1st hydraulic motor 13, 15, 157 Drive unit 14 Cross member 26, 162, 170 Support body 27, 142, 166 King pin 28, 76, 124, 166 Housing 36 Front wheel 38 Deceleration mechanism 39 Brake mechanism 40 Tilt mechanism 53 Movable swash plate 74 Duct 79, 119, 167 Rear wheel 80, 115, 165 Second hydraulic motor

Claims (8)

  A steering wheel drive unit comprising: a housing that supports a single axle; a hydraulic motor for driving the axle provided in the housing; and a single steering wheel fixed to an end of the single axle. The steering wheel drive unit is characterized in that the housing is rotatably attached to the vehicle frame via a king pin.   A steering wheel drive unit comprising: a housing that supports a single axle; a hydraulic motor for driving the axle provided in the housing; and a single steering wheel fixed to an end of the single axle. The single axle is disposed on the same axial center inside the hydraulic motor, and the housing is rotatably attached to the vehicle frame via a king pin. Wheel drive unit.   3. The hydraulic motor is a variable displacement type, and a volume adjuster of the hydraulic motor is operated by relative rotation during steering between the kingpin and the housing and a vehicle frame. Steering wheel drive unit.   The steering according to claim 3, wherein the king pin is rotatably passed through a cylindrical body fixed to the vehicle frame, and the volume adjuster is operated by relative rotation of the king pin in the cylindrical body. Wheel drive unit.   3. The steered wheel drive unit according to claim 1, wherein an oil conduit for the hydraulic motor is provided in the king pin.   A steering wheel; a king pin; a housing connected to the king pin to support the steering wheel; and a first hydraulic motor for driving the steering wheel provided in the housing; A work vehicle including a steering wheel drive unit that can be rotated integrally by rotation, the second hydraulic motor, a traveling drive wheel driven by the second hydraulic motor, and the first and second hydraulic motors In a hydraulic circuit that fluidly connects the first and second hydraulic motors to the hydraulic pump, both hydraulic motors are connected in series to the hydraulic pump. A four-wheel drive vehicle comprising a shift switching valve that can be switched to a state connected in parallel.   7. The four-wheel drive vehicle according to claim 6, wherein the shift switching valve is further switchable so that oil from the hydraulic pump flows only to the second hydraulic motor among the two hydraulic motors.   The second hydraulic motor is of a variable displacement type, and the volume controller of the hydraulic motor has a volume when the shift switching valve is switched to flow the oil from the hydraulic pump only to the second hydraulic motor. The four-wheel drive vehicle according to claim 7, wherein the four-wheel drive vehicle is linked to the shift switching valve so as to be operated in a direction to reduce the speed.

Images