JPH0735153U - Large forklift drive system - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce wear of mechanical brakes and tires. [Structure] The HST pump 32 is driven by the engine 33.
The pressure oil is discharged from the vehicle, and the pressure oil is sent to the HST motor 30 of each wheel 25, 26, 27, 28. HST motor 30
Is driven to rotate the wheels 25, 26, 27, 28, and the vehicle runs. When the supply of pressure oil from the HST pump 32 is stopped, the driving of the HST motor 30 is stopped. The stopped HST motor 30 brakes each wheel 25, 26, 27, 28 which is rotating due to inertial force. Rear wheel 2
When 2 and 23 are turned to turn the vehicle, the wheels on the inside of the turn are more resistant and the pressure oil supplied to each HST motor 30 changes. The wheel on the inside of the turn has a lower rotation speed, and the wheels 25, 26, 27, 28 turn without slipping.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a hydraulic traveling drive device for a large forklift truck in which the left and right drive front wheels are compound wheels.

[0002]

[Prior art]

 In general, a counterbalance type cargo handling vehicle represented by a forklift is valued for its ease of cargo handling and its good turning performance. However, there are problems that the weight of the vehicle is heavy due to the equipment such as the counter weight at the rear of the vehicle, and there is a large shift in the position of the center of gravity between when there is no load and when there is no load. In large forklifts, the front wheels are double wheels (4 wheels or 6 wheels) to shorten the front overhang.

In this traveling drive device for a large forklift of the double-wheel type, as shown in FIGS. 16 and 17, the rotational force of the engine 1 is transmitted to the torque converter 2, the propeller shaft 4 is rotated via the transmission 3, and the differential is transmitted. In general, the driving front wheels 7 of the left and right compound wheels are synchronously rotated via a drive axle 6 equipped with 5. In FIG. 16, 8 is a hydraulic pump, 9 is a hydraulic valve, 10 is a rear wheel which is a diverting wheel, and 11 is a steering axle. When the torque converter 2 is used in this way, the power of the engine 1 is transmitted through the fluid, so even if the input speed from the engine 1 is the same, the speed of the output shaft will differ depending on the resistance of the output side. In addition, it is highly versatile in that it is hard to apply engine braking (low resistance to driving from the output shaft side). Therefore, compared with the case where a mechanical transmission is adopted, the engine stop does not cause so-called engine stall, the impact from the output shaft side can be mitigated, and the durability of the power system can be improved. There is.

[0004]

However, in a large forklift truck that employs a conventional torque converter, the rigidity is poor, and it is difficult to travel at a constant speed due to a load or the like depending on the road surface condition. Moreover, since the engine brake is hard to apply, the mechanical brakes such as the service brakes built into the wheels are responsible for all braking when stopping a vehicle that is heavy and has a large inertial force. There is a drawback that the mechanical brake will be severely worn if the work is repeated forward and backward.

On the other hand, in a small forklift having left and right driving front wheels as single wheels, for example, when turning to the left as shown in FIG. 18, the differential 16 absorbs the rotational difference between the left and right driving front wheels 15 and the left side. Drive front wheel 15 has a turning radius r_iAnd the driving front wheel 15 on the right side has a turning radius r_oWith this, you can make turns with less slip. However, in a large forklift truck in which the left and right drive front wheels 7 are compound wheels, the relative rotational difference between the left drive front wheel 7 and the right drive front wheel 7 when turning is not adjusted by the differential 5. However, there is no differential function between the inner ring 7a and the outer ring 7b of the left and right drive front wheels 7, and a rotation difference occurs between the inner ring 7a and the outer ring 7b. In order for the inner wheel 7a and the outer wheel 7b of the left and right drive front wheels 7 to turn without slip, for example, when turning left as shown in FIG. 17, the outer wheel 7b of the left drive front wheel 7 turns with a turning radius r._ii, Inner ring 7a has a turning radius r_io, The inner wheel 7a of the right driving front wheel 7 is the turning radius r_oi, The outer ring 7b has a turning radius r _oo Although it is ideal to make a turn at, the turning radius r, which is an intermediate position between the inner wheel 7a and the outer wheel 7b of the left and right drive front wheels 7, is actually used._xAnd turning radius r_yI have no choice but to turn around with. Therefore, the inner wheels 7a and the outer wheels 7b of the left and right driving front wheels 7 travel while slipping, and the tire is severely worn.

As described above, in the conventional large-sized forklift, the mechanical brakes and the tires are heavily worn, so that the maintenance cost of the mechanical brakes and the tires is increased, and the life cycle cost is increased.

In view of the above, the present invention has an object to provide a traveling drive device for a large forklift capable of reducing wear of mechanical brakes and tires.

[0008]

[Means for Solving the Problems]

 As shown in FIGS. 1 and 2, the left and right driving front wheels 20 and 21 are compound wheels, and the rear wheels 22 and 23 are diverting wheels. A hydraulic motor 30 mounted on each wheel 25, 26, 27, 28 for rotationally driving each wheel 25, 26, 27, 28, a hydraulic pump 32 for driving the hydraulic motor 30, and an engine for driving the hydraulic pump 32. 33 and 33 are provided.

As shown in FIG. 12, the means for solving the problem according to claim 2 is a variable displacement type first hydraulic pump 120 for driving each hydraulic motor 30 arranged on the left drive front wheel 20, and a right drive front wheel. 21 is provided with a variable displacement type second hydraulic pump 121 for driving the respective hydraulic motors 30 arranged in 21 to change the discharge direction and discharge amount of the pressure oil from the first and second hydraulic pumps 120, 121. Then, a traveling switching means for switching the rotational direction and rotational speed of the front driving wheels 20, 21 is provided.

According to a third aspect of the present invention, the rear wheel 130 is provided in the center of the rear portion of the vehicle body 40 to form a compound wheel, as shown in FIG.

According to a fourth aspect of the present invention, as shown in FIG. 8, the fork 100 can be raised and lowered between the outer wheels 25 and 28 and the inner wheels 26 and 27 of the left and right driving front wheels 20 and 21. A fixed mast 101 for holding the fixed mast 101 is provided.

[0012]

[Action]

 In the problem solving means according to claim 1, when the engine 33 is driven, pressure oil is discharged from the hydraulic pump 32 and sent to each hydraulic motor 30 mounted on each wheel 25, 26, 27, 28. Then, the hydraulic motor 30 is driven, each wheel 25, 26, 27, 28 rotates, and the vehicle runs.

Here, when the traveling of the vehicle is stopped, if the supply of the pressure oil from the hydraulic pump 32 is stopped, the drive of the hydraulic motor 30 is stopped regardless of the drive of the engine 33. The stopped hydraulic motor 30 applies a load to the wheels 25, 26, 27, 28 that are rotating due to inertial force, decelerates and stops (brake function). By utilizing this brake function, the mechanical brake is not applied to the mechanical brakes when the vehicle is stopped, but at the final stage of the braking process (when the vehicle is completely stopped or is continuously stopped). Just use.

When the rear wheels 22 and 23 are turned to turn the vehicle, the wheels 25, 26, 27 and 28 have different resistances, that is, the wheels on the inside of the turning have a larger resistance. A hydraulic motor 30 is attached to each of the wheels 25, 26, 27, and 28 and driven separately, and the load on the hydraulic motor 30 increases as the resistance of the wheel increases. At this time, the larger the load of the hydraulic motor 30, the smaller the supply amount of the pressure oil discharged from the hydraulic pump 32. Therefore, the rotation speed of the wheel on the inside of the turning becomes slower (differential function). As a result, the wheels 25, 26, 27, 28 turn ideally without slipping.

In the problem solving means according to the second and third aspects, when the vehicle is turned by the interlining, the rear wheels 130 are turned by 90 degrees so that the first hydraulic pump 120 and the second hydraulic pump 121 discharge the hydraulic pressure. So that they are opposite to each other. As a result, the left drive front wheel 20 and the right drive front wheel 21 rotate in opposite directions, and the vehicle turns in the interlining direction.

In the problem solving means according to claim 4, since the hydraulic motors 30 are mounted on the wheels 25, 26, 27, 28, respectively, the distance between the wheels 25 and 26 and the distance between the wheels 27 and 28 are increased, Since the fixed mast 101 is mounted in these gaps, the field of view in the front center portion is expanded, and the cargo handling efficiency and the safety during transportation are improved as compared with the case where the fixed mast 101 is mounted between the wheels inside.

[0017]

(First Embodiment) As shown in FIGS. 1, 2, and 3, a large forklift according to a first embodiment of the present invention has left and right drive front wheels 20 and 21 as double wheels, and left and right rear wheels. 22 and 23 are said to be directional wheels. The traveling drive device 24 for driving the left and right driving front wheels 20, 21 is mounted on each wheel 25, 26, 27, 28 of the left and right driving front wheels 20, 21 and connects the respective vehicle wheels 25, 26, 27, 28. A constant-capacity hydrostatic motor (hereinafter referred to as an HST motor) 30 that is a rotationally driven hydraulic motor, and a hydraulic pressure that is supplied by supplying pressure oil to each HST motor 30 via a high-pressure hose 31 that is a closed circuit. A variable displacement hydrostatic pump (hereinafter referred to as HST pump) 32, which is a pump, and an engine 33 that drives the HST pump 32 are provided.

As shown in FIG. 4, each wheel 25, 26, 27, 28 is composed of a hub 45 and a tire 37 mounted on the hub via a rim 36. The wheels 27, 28 are opposed to each other with a left housing 41 projecting forward from the left front part interposed therebetween, and the wheels 27, 28 are opposed to each other with a right housing 42 projecting forward from the right front part of the vehicle body 40 interposed therebetween.

As shown in FIGS. 4 and 5, the HST motor 30 has a cylinder block 52, a plurality of pistons 53 that are arranged in the cylinder block 52 so as to be movable back and forth, and an angle with respect to the axis of the motor shaft 54. And a swash plate 55 connected to the piston 53 and installed inside the spindle 51. The spindle 51 is fixed by penetrating the side walls of the left and right housings 41, 42, and is installed in the hub 45 of each wheel 25, 26, 27, 28. The spindle 51 is fixed with a flange 50 on which a valve unit 57 having a relief valve, a shuttle valve, etc. is mounted. The flange 50 is formed with a piping port 56 for connecting the high pressure hose 31 guided from the HST pump 32 to the left and right housings 41, 42, and the high pressure hose 31 is connected to the ports A and B of the HST motor 30. It is in communication. The cylinder block 52 has a gidney 59 communicating with the port A and the port B. Further, the HST motor 30 is provided with a parking brake device 60 that restricts rotation of the cylinder block 52, and a speed reducer 61 that is provided on the output side of the motor shaft 54 and that transmits the rotation of the motor shaft 54 to the hub 45. It is included.

As shown in FIGS. 3 and 6, the HST pump 32 includes an input shaft 85 spline-fitted to the drive shaft 33 a of the engine 33, a movable swash plate 86 attached to the input shaft 85, and a movable swash plate 86. A cylinder block 88 is provided with a cylinder block 88 connected to a swash plate 86 via a plurality of pistons 87 that can move back and forth, and the cylinder block 88 is formed with a gidney 89 that communicates with the port A and the port B.

Further, the HST pump 32 is equipped with a control lever 90, a charge pump 91 and a main pump 99, which control the traveling speed and forward and backward movement of the vehicle by varying the discharge direction and discharge amount of the pressure oil to be discharged. There is. The control lever 90 can be switched between a vehicle forward position, a neutral stop position, and a vehicle reverse position by a pedal or an operating lever arranged in the driver's cab, and the tilt angle switching valve 93 or the like is operated to operate the movable swash plate 86. It has a structure that switches the tilt angle. The traveling speed of the vehicle increases as the control lever 90 moves from the neutral stop position to the vehicle forward position or the vehicle reverse position. The charge pump 91 supplies pressure oil to the brake valve 70 in the brake device 60, and the main pump 99 supplies pressure oil to the cargo handling device and the diversion device. Further, FIG. 7 shows a detailed oil flow between the HST motor 30 and the HST pump 32. In the figure, 94 is a suction filter, 95 is a check valve, 96 is an oil tank, 97 is an oil cooler, and R is Is a charging pump circuit, S is a drain circuit, T is a main hydraulic circuit, and U is a brake circuit.

In the traveling drive device 24 as described above, the HST motor 30 is mounted on each wheel 25, 26, 27, 28, and the left and right housings 41, 42 of the vehicle body 40 include the HST motor 30, that is, each wheel. Since 25, 26, 27, and 28 are held, the wheel spacing on the left side and the right side is wider than in the case where the wheels are connected by an axle shaft or the like. Therefore, as shown in FIGS. 2, 8 and 9, fixed masts 101 holding the forks 100 are attached to the left and right housings 41 and 42 so as to be tiltable around the mast support pins 102. An elevating mast 103 is attached to the fixed mast 101 so as to be able to elevate and lower, a finger bar 107 is attached to the elevating mast 103 so as to be able to elevate, and forks 100 are attached to both ends of the finger bar 107. 2 and 8, reference numeral 104 is an elevating cylinder for elevating the elevating mast 103 along the fixed mast 101, 105 is a tilt cylinder for tilting the fixed mast 101, and 106 in FIG. And the pipe connection holes formed in the right housings 41 and 42.

In the above configuration, the movable swash plate 86 of the HST pump 32 is tilted to move the vehicle forward and backward by setting the control lever 90 to the vehicle forward position or the vehicle reverse position by operating the pedal or the operating lever in the cab. When the rotation speed of the engine 33 increases and the drive shaft 33a rotates according to the depression amount of the accelerator pedal, the input shaft 85 and the movable swash plate 86 of the HST pump 32 rotate. As a result, the cylinder block 88 rotates, and when the vehicle moves forward as shown in FIG. 10, the high pressure oil is discharged from the gidney 89 to the port A in proportion to the rotation speed, and the low pressure oil is sucked from the port B to the gidney 89 in the same amount. . When the vehicle is moving backward as shown in FIG. 11, the high pressure oil is discharged from the gidney 89 to the port B and the low pressure oil is sucked from the port A to the gidney 89. The high-pressure oil discharged to the port A or the port B is guided to the gidney 59 from the pipe port 56 of the HST motor 30 mounted on each wheel 25, 26, 27, 28 and the piston 53 of the cylinder block 52. Press it against the swash plate 55. Since the swash plate 55 is attached at an angle with respect to the axis of the motor shaft 54, torque is generated by the component force when the piston 53 is pressed, and this torque acts as rotational force via the piston 53 and the cylinder 53. The block 52 is rotated and the motor shaft 54 is rotated. The rotation of the motor shaft 54 is decelerated by the reduction gear 61 and transmitted from the hub 45 to the wheels 25, 26, 27, 28, and the vehicle runs.

Here, when stopping the traveling of the vehicle, as shown in FIG. 6, the control lever 90 is set to the neutral stop position and the inclined surface of the movable swash plate 86 is made parallel to the cylinder block 88. Then, regardless of the driving of the engine 33, the high pressure oil is not discharged from the HST pump 32, the force for pressing the piston 53 against the swash plate 55 in the HST motor 30 is lost, and the operation of the HST motor 30 is stopped. At this time, the wheels 25, 26, 27, 28 are rotated by inertial force, and the rotation of the wheels 25, 26, 27, 28 rotates the motor shaft 54 and the swash plate 55 of the HST motor 30. As a result, the piston 53 is pushed into the cylinder block 52 at the portion where the swash plate 55 approaches the cylinder block 52, and the oil in the cylinder block 52 is compressed, and the force for compressing this oil is applied to each wheel. The rotation of 25, 26, 27, 28 is decelerated to stop (brake function). By utilizing this braking function, the mechanical brake is not used for stopping all braking when the vehicle is stopped, and the mechanical brake is used at the final stage of the braking process (when the vehicle is completely stopped or continues to be stopped). Just use.

Further, when the rear wheels 22 and 23 are turned to turn the vehicle, different resistances are applied to the wheels 25, 26, 27 and 28, that is, a larger resistance is applied to the wheels on the inside of the turn. An HST motor 30 is attached to each wheel 25, 26, 27, and 28 and driven separately, and a wheel having a larger resistance has a larger load on the HST motor 30. At this time, the higher the load of the HST motor 30, the smaller the supply amount of the high-pressure oil discharged from the HST pump 32, and therefore the rotation speed of the wheel on the inside of the turning becomes slower (differential function). Thus, for example, when the vehicle is turned to the left, as shown in FIG. 8, the wheel 25 has a turning radius r _ii , the wheel 26 has a turning radius r _io , the wheel 27 has a turning radius r _oi , and the wheel 28 has a turning radius r i. _{At oo} , the rotation speed is suitable for turning, and the wheels 25, 26, 27, 28 turn without slipping. The same applies when the vehicle is turned to the right.

As described above, the HST motor 30 is attached to each of the wheels 25, 26, 27, 28, and the HST motor 30 is operated by the supply of high-pressure oil from the HST pump 32 by driving the engine 33. Therefore, when the vehicle is stopped, the frequency of use of the mechanical brake can be reduced by utilizing the brake function, and when the vehicle is turned, the wheels 25, 26, 27, 28 are prevented from slipping by the differential function. Can be turned. Therefore, the wear of the mechanical brake and each tire 37 can be reduced, and the life cycle cost can be reduced.

Further, since the HST motor 30 is attached to each of the wheels 25, 26, 27, 28, the distance between the wheels 25 and 26 and the distance between the wheels 27 and 28 are widened, and the distance is between them. The fixed mast 101, the lifting mast 103, and the lifting cylinder 104 can be mounted on the left and right housings 41 and 42, and as compared with the field of view P when mounted between the conventional wheel 26 and the wheel 27 as shown in FIG. Since the field of view Q in the front center part is expanded, the cargo handling efficiency and the safety during transportation are improved. Moreover, since the gap between the fixed masts 101 is widened, the gap between the mounting positions of the finger bars 107 with respect to the lifting mast 103 is widened, and the force applied to the finger bars 107 can be reduced. Therefore, the finger bar 107 can be made thin or thin to be lightweight.

Second Embodiment As shown in FIGS. 12 and 13, the large forklift according to the second embodiment has a variable capacity for driving each HST motor 30 mounted on each wheel 25, 26 of the left drive front wheel 20. A first HST pump 120 of a variable displacement type and a second HST pump 121 of a variable displacement type for driving each HST motor 30 mounted on each wheel 27, 28 of the right front drive wheel 21 are provided. (2) Operation of operating the respective control levers 90 of the pumps 120 and 121 as travel switching means for changing the direction and quantity of discharge of the high pressure oil from the HST pumps 120 and 121 to switch between forward and backward traveling and traveling speed of the vehicle. A lever is provided. The power of the engine 33 is transmitted to the first and second HST pumps 120 and 121 by a gear mechanism (not shown). Further, in FIG. 13, reference numeral 129 is a vehicle fall prevention leg, and tires can be easily replaced from the rear.

Further, the compound wheel type rear wheel 130 is arranged in the center of the rear part of the vehicle body 40. As shown in FIGS. 14 and 15, the rear wheel 130 is provided with a caster angle K in order to have a straight traveling property when the vehicle is moving forward, and the rear wheel 131 and the pair of rear wheels 131 and 132 are provided. A rear axle 133 that rotatably holds the rear axle 133 and a rear axle support 135 that rotatably holds the rear axle 133 around the support pin 134. The rear axle support 135 is integrally formed with a vertical axis portion 135a penetrating the frame 136 of the vehicle body 40 and rotatably supported by the support housing 137, and an axle stopper 140 for restricting the swing of the rear axle 133. The driven sprocket 150 connected to the drive sprocket 146 of the steering device 145 via the endless chain 147 is fixedly installed. Then, the rear wheel 130 can be turned 90 degrees in the left-right direction by the steering device 145. The other configurations are the same as those in the first embodiment.

In the above structure, when the vehicle is traveling straight ahead and is turning left about the point X shown in FIG. 12, the rear wheel 130 is turned to a predetermined position, and the discharge amount of the high pressure oil of the first HST pump 120 is changed. The control lever 90 corresponding to the first HST pump 120 is operated from the vehicle forward position to the neutral stop position by the operating lever so that the rotational speed of the left drive front wheel 20 is changed to that of the right drive front wheel 21. Rotate while making it slower than the rotation speed.

When the vehicle turns left around the point Y shown in FIG. 12, the rear wheels 130 are further turned so that the first HST pump 120 does not discharge the high-pressure oil. The control lever 90 corresponding to is moved to the neutral stop position and the left drive front wheel 20 is stopped to rotate while the right drive front wheel 21 is rotated.

Further, when the vehicle turns left (interlining turn) around the point Z shown in FIG. 12, the rear wheels 130 are turned 90 degrees and the control lever 90 corresponding to the second HST pump 121 is moved forward. Position, the control lever 90 corresponding to the first HST pump 120 is set to the vehicle reverse position, and the left drive front wheel 20 is rotated while being rotated in the reverse direction. When turning the vehicle to the right, the operation of the control lever 90 may be reversed.

As described above, the first and second HST pumps 120 and 121 are arranged so that the rotational speed and the rotational direction of the left driving front wheel 20 and the right driving front wheel 21 are switched separately. Ground turning becomes possible.

Moreover, since the rear wheel 130 is arranged in the center of the rear part of the vehicle body 40, the structure for diverting the rear wheel 130 is simple and inexpensive, and the vehicle body 40 does not protrude from the left and right. The rear wheel 130 does not hit anything. Further, since the distance between the front wheels 20 and 21 and the rear wheels 130 is widened, as shown in FIG. 13, the engine 33 and the HST pumps 120 and 121 can be mounted low between them to form a low center of gravity type vehicle. The counter weight can be reduced by mounting the engine 33 and the HST pumps 120, 121 on the rear side, and the pitching during running can be reduced to improve the riding comfort and reduce driver's fatigue. Further, since the rear wheel 130 is a compound wheel and the left and right wheels can be rotated separately, the rear wheel 130 at the time of conversion does not slip and wear can be reduced.

It should be noted that the present invention is not limited to the above embodiment, and it goes without saying that many modifications and changes can be made to the above embodiment within the scope of the present invention. For example, the HST motor 30 in the first and second embodiments may be equipped with a brake valve device for smoothly controlling the HST motor 30. Further, the HST motor 30 may be of a variable displacement type, and a high / low speed two-stage switching device for switching the rotation speed of the motor shaft 54 by switching the inclination angle of the swash plate 55 may be provided.

Further, the left and right driving front wheels 20, 21 may be six wheels in total, and the HST pump 32 may be arranged for each HST motor 30. Furthermore, a microcomputer may be equipped to determine the traveling speed of the vehicle by adjusting the discharge amount of the pressure oil discharged from the HST pumps 32, 120, 121 according to the turning angle of the steering wheel.

[0037]

[Effect of device]

 As is clear from the above description, according to claim 1 of the present invention, when the hydraulic motor is mounted on each wheel and each hydraulic motor is operated by the supply of the pressure oil from the hydraulic pump, the vehicle is stopped. In addition, the use of the brake function can reduce the frequency of use of mechanical brakes, and when the vehicle turns, the differential function allows each wheel to turn without slipping. Therefore, the wear of the mechanical brake and each tire can be reduced, and the life cycle cost becomes low.

According to the second aspect of the present invention, the first and second hydraulic pumps are arranged so that the rotational speed and the rotational direction of the left drive front wheel and the right drive front wheel can be switched separately. Ground turning becomes possible.

According to the third aspect, since the rear wheel is arranged in the center of the rear part of the vehicle body, the structure for diverting the rear wheel is simple and inexpensive, and the rear wheel can be protruded from the left and right sides of the vehicle body. It won't hit anything. Furthermore, since the distance between the front wheels and the rear wheels is wide, it is possible to mount the engine and hydraulic pump low during this period to create a vehicle with a low center of gravity. Counterweight can be reduced, and pitching during driving is reduced to improve ride comfort and reduce driver fatigue. In addition, since the rear wheels are compound wheels, it is possible to reduce wear of the rear wheels during the turning.

According to the fourth aspect, the fixed mast can be mounted between the outer wheels and the inner wheels of the left and right driving front wheels, and the front field of view can be improved as compared with the case where the fixed mast is mounted between the inner wheels. Since it is expanded, cargo handling efficiency and safety during transportation are improved.

[Submission date] March 17, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

[Problems to be solved by the device]

 However, in a large-sized forklift that employs a conventional torque converter, the rigidity is poor, and it is difficult to drive at a constant speed due to the load due to road conditions. Moreover, the engine brake is hard to apply, so when stopping a vehicle that is heavy and has a large inertial force, mechanical brakes (including brakes operated by hydraulic pressure) such as service brakes built into the wheels of the wheels all provide full braking. However, there is a drawback in that the mechanical brake will be severely worn if the work is repeated such that the brakes are frequently used, such as forward and backward movements.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

On the other hand, in a small forklift having left and right driving front wheels as single wheels, for example, when turning to the left as shown in FIG. 18, the differential 16 absorbs the rotational difference between the left and right driving front wheels 15 and the left side. The driving front wheels 15 of the right driving front wheels 15 have a turning radius r _i , and the right driving front wheels 15 have a turning radius r _o of each other, so that the driving can be performed by turning with less slip. However, in a large forklift truck in which the left and right drive front wheels 7 are compound wheels, the relative rotational difference between the left drive front wheel 7 and the right drive front wheel 7 when turning is not adjusted by the differential 5. However, there is no differential function between the inner wheel 7a and the outer wheel 7b of the left and right drive front wheels 7, and there is no difference in rotation between the inner wheel 7a and the outer wheel 7b. In order for the inner wheel 7a and the outer wheel 7b of the left and right drive front wheels 7 to turn without slippage, for example, when turning left as shown in FIG. 17, the outer wheel 7b of the left drive front wheel 7 has a turning radius r _ii , 7a should have a turning radius r _io , the inner wheel 7a of the right driving front wheel 7 should have a turning radius r _oi , and the outer wheel 7b should have a turning radius r _oo , so there must be a difference in rotation, but in reality there are left and right sides. of which it is forced to pivot and the turning radius r _x and swivel radius r _y is an intermediate position between the inner ring 7a and the outer ring 7b of the drive wheel 7. Therefore, the inner wheels 7a and the outer wheels 7b of the left and right drive front wheels 7 turn while slipping, and the tires are greatly worn.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

In the means for solving the problems according to claims 2 and 3, when turning the vehicle, the rear wheels 130 are turned so that the first hydraulic pump 120 and the second hydraulic pump 121 have the discharge directions of the pressure oils mutually. If the pumps 120 and 121 are stopped in reverse, the left drive front wheel 20 and the right drive front wheel 21 rotate in opposite directions to each other, or one of them stops, and the vehicle turns in the interlining direction.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

[0017]

【Example】

 (First Embodiment) As shown in FIGS. 1, 2 and 3, in a large forklift according to a first embodiment of the present invention, the left and right drive front wheels 20 and 21 are compound wheels, and the left and right rear wheels 22 and 23 are respectively. It is known as a conversion wheel. The traveling drive device 24 for driving the left and right driving front wheels 20, 21 is mounted on each wheel 25, 26, 27, 28 of the left and right driving front wheels 20, 21 and connects the respective vehicle wheels 25, 26, 27, 28. A constant displacement hydrostatic motor (hereinafter referred to as an HST motor) 30 that is a hydraulic motor that is rotationally driven, and a variable displacement that is a hydraulic pump that is driven by supplying pressure oil to each HST motor 30 via a high pressure hose 31. A hydrostatic pump (hereinafter referred to as HST pump) 32 and an engine 33 for driving the HST pump 32 are provided.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

As shown in FIGS. 4 and 5, the HST motor 30 has a cylinder block 52, a plurality of pistons 53 that are arranged in the cylinder block 52 so as to be movable back and forth, and an angle with respect to the axis of the motor shaft 54. And a swash plate 55 connected to the piston 53 and installed inside the spindle 51. The spindle 51 is fixed by penetrating the side walls of the left and right housings 41, 42, and is installed in the hub 45 of each wheel 25, 26, 27, 28. The spindle 51 is fixed with a flange 50 on which a valve unit 57 having a relief valve, a shuttle valve, etc. is mounted. The flange 50 is formed with a piping port 56 for connecting the high pressure hose 31 guided from the HST pump 32 to the left and right housings 41, 42, and the high pressure hose 31 is connected to the ports A and B of the HST motor 30. It is in communication. The cylinder block 52 has a gidney 59 communicating with the port A and the port B. Further, the HST motor 30 is provided with a brake device 60 that restricts rotation of the cylinder block 52, and a speed reducer 61 that is provided on the output side of the motor shaft 54 and that transmits the rotation of the motor shaft 54 to the hub 45. Has been.

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

Further, when turning the vehicle to the left around the point Z shown in FIG. 12, the rear wheels 130 are turned by 90 degrees and the control lever 90 corresponding to the second HST pump 121 is moved to the vehicle forward position to move the first wheel. The control lever 90 corresponding to the one HST pump 120 is set to the vehicle reverse position, and the left drive front wheel 20 is rotated while being reversely rotated. When turning the vehicle to the right, the operation of the control lever 90 may be reversed.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction content]

As described above, the first and second HST pumps 120 and 121 are arranged so that the rotational speed and the rotational direction of the left driving front wheel 20 and the right driving front wheel 21 are switched separately. Ground turning becomes possible. The spin turn and pivot turn are collectively referred to as interlining turning.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

Moreover, since the rear wheel 130 is arranged in the center of the rear part of the vehicle body 40, the structure for diverting the rear wheel 130 is simple and inexpensive, and the vehicle body 40 does not protrude from the left and right. The rear wheel 130 does not hit people or objects. Further, since the distance between the front wheels 20 and 21 and the rear wheels 130 is widened, it is possible to mount the engine 33 and the HST pumps 120 and 121 low between them as shown in FIG. 13 to make a low center of gravity type vehicle. The counterweight can be reduced by mounting the engine 33 and the HST pumps 120 and 121 in the rear, and the pitching during traveling can be reduced to improve the riding center and reduce driver fatigue. Further, since the rear wheel 130 is a compound wheel and the left and right wheels can be rotated separately, the rear wheel 130 at the time of conversion does not slip and wear can be reduced.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction content]

According to the third aspect, since the rear wheel is arranged in the center of the rear part of the vehicle body, the structure for diverting the rear wheel is simple and inexpensive, and the rear wheel can be protruded from the left and right sides of the vehicle body. Without hitting people or things. Furthermore, since the distance between the front wheels and the rear wheels is wide, it is possible to mount the engine and hydraulic pump low during this period to create a vehicle with a low center of gravity. As a result, the counterweight can be reduced, and the riding comfort is improved by reducing the pitching while driving, and the fatigue of the driver can be reduced. Further, since the rear wheels are compound wheels and can rotate separately, it is possible to reduce the wear of the rear wheels during the turning.

[Brief description of drawings]

FIG. 1 is a block diagram showing a traveling drive device for a large forklift according to a first embodiment of the present invention.

[Figure 2] Side view of the same large forklift

FIG. 3 is a hydraulic circuit diagram of the traveling drive device.

FIG. 4 is a sectional view of a driving front wheel.

FIG. 5 is a perspective view of an HST motor

FIG. 6 is a perspective view of a main part of the HST pump in a neutral state.

FIG. 7 is a diagram showing a detailed oil flow between the HST pump and the HST motor.

FIG. 8 is a plan view showing a turning radius and a visual field in a large forklift.

FIG. 9 is a view showing how the fixed mast is attached to the vehicle body.

FIG. 10 is a perspective view of the HST pump when the vehicle is moving forward.

FIG. 11 is a perspective view of the HST pump when the vehicle is traveling in reverse.

FIG. 12 is a configuration diagram showing a traveling drive device for a large forklift according to a second embodiment.

FIG. 13 is a side view of the same large forklift truck.

FIG. 14 is a partial sectional view of a rear wheel.

FIG. 15 is a side sectional view of a rear wheel.

FIG. 16 is a side view of a conventional large forklift.

FIG. 17 is a diagram showing a turning radius of a wheel in a large-sized forklift whose front driving wheels are a double wheel type.

FIG. 18 is a diagram showing a turning radius of a wheel in a small forklift having a single-wheel drive front wheel.

[Explanation of symbols]

 20, 21 Drive front wheel 22, 23 Rear wheel 25, 26 Left wheel 27, 28 Right wheel 30 Hydraulic motor 32 Hydraulic pump 33 Engine 40 Vehicle body 90 Control lever 100 Fork 101 Fixed mast 120 First hydraulic pump 121 Second hydraulic pump 130 Rear wheel

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 17, 1994

[Procedure Amendment 10]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

[Procedure Amendment 11]

[Document name to be corrected] Drawing

[Correction target item name] Figure 15

[Correction method] Change

[Correction content]

FIG. 15

Claims (4)

[Scope of utility model registration request] 1. A large-sized forklift having left and right drive front wheels each being a compound wheel and rear wheels being diverting wheels, and a hydraulic motor mounted on each wheel of the drive front wheels for rotationally driving each wheel, and the hydraulic pressure. A traveling drive device for a large forklift, comprising: a hydraulic pump that drives a motor; and an engine that drives the hydraulic pump. 2. A variable displacement first hydraulic pump for driving each hydraulic motor arranged on the left drive front wheel, and a variable displacement first hydraulic pump for driving each hydraulic motor arranged on the right drive front wheel. Two hydraulic pumps are provided, and traveling switching means is provided for changing the discharge direction and discharge amount of the pressure oil from the first and second hydraulic pumps to switch the rotational direction and rotational speed of the left and right drive front wheels. The traveling drive device for a large forklift according to claim 1. 3. The traveling drive device for a large forklift according to claim 1, wherein the rear wheel is provided in the center of the rear part of the vehicle body to form a compound wheel. 4. A large forklift according to claim 1, wherein fixed masts for holding the fork vertically are provided between the outer wheels and the inner wheels of the left and right drive front wheels, respectively. Travel drive.