JP2000318995A - Hydraulically driven forklift - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulically driven forklift equipped with an enhanced mobility through introducing a two-pump and two-motor system and capable of lessening the turning radius. SOLUTION: The front wheels 3A and 3B are coupled with hydraulic motors 21A and 21B in an interlocking manner, and hydraulic pumps 26A and 26B to be driven by an engine 25 are installed, wherein the hydraulic pumps 26A and 26B are connected to the hydraulic motors 21A and 21B, respectively. The control of the speed is made by changing over the direction of oil flow in the pumps 26A and 26B, changing the rotating directions of the motors 21A and 21B, controlling the revolving speed of the engine 25 and the rate of oil flow in the pumps 26A and 26B, and changing the revolving speeds of the motors 21A and 21B. The control of turning the heading is made by controlling the revolving speeds (equal or different) and/or the rotating direction (normal or reverse) of the front wheels 3A and 3B on the basis of the turning angle of the steering wheel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine type forklift employing a hydraulic drive system.

[0002]

2. Description of the Related Art Conventionally, as a power transmission device of a general engine type forklift, a clutch type or a torque converter type is mainly used, but there is also an engine type forklift employing a hydraulic drive system. The engine type forklift adopting this hydraulic drive system is a one-pump one-motor type or a one-pump two-motor type. Its features include high efficiency and no need for a front differential. Has become.

Further, a conventional general forklift is
Since the center of gravity is higher than that of a passenger car and it has a cradle, stability during turning is poor, and there is a risk of overturning when making a sharp turn at high speed. Is controlled accordingly. In addition, since the rollover during turning is more likely to occur as the traveling speed becomes faster and the turning becomes steeper, the traveling speed at the time of turning may be reduced. In this case, the driver (operator) will (the accelerator pedal depression). ) Is related, the operation error easily occurs. Therefore, as a system for automatically controlling the traveling speed, there has been provided a system in which the steering angle of the steering wheel is fed back and the rotation speed of the engine is changed using an electronic governor or the like.

[0004]

However, in the above-described conventional forklift, since a common pump is used for the left and right front wheels as driving wheels, the mobility is poor and the turning radius is large. Become. Further, according to the method of controlling the traveling speed during turning by changing the number of revolutions of the engine, the structure becomes complicated and the traveling speed cannot be set arbitrarily.

Therefore, the invention of claim 1 of the present invention
An object of the present invention is to provide a hydraulically driven forklift capable of improving mobility and reducing a turning radius by adopting a pump 2 motor type. Another object of the present invention is to provide a hydraulically driven forklift capable of automatically controlling the traveling speed during turning without changing the engine speed.

[0006]

According to a first aspect of the present invention, there is provided a hydraulically driven forklift having a pair of left and right front wheels and a pair of right and left rear wheels. A mast and a fork are provided on the front end side of the vehicle body, and each front wheel is connected to a drive shaft on a hydraulic motor side attached to the vehicle body, and a plurality of hydraulic pumps driven by an engine are provided on the vehicle body side. And one hydraulic pump is associated with and connected to one hydraulic motor, and each rear wheel is provided so as to be pivotable about a longitudinal axis with respect to the vehicle body side. .

Therefore, according to the first aspect of the invention, the right and left front wheels and the right and left rear wheels are oriented in the front-rear direction during normal straight running. The speed control during forward and backward running is controlled by changing the direction of oil flow of both hydraulic pumps using the change lever to change the rotation direction of each hydraulic motor, and by using the accelerator pedal, the engine speed and the oil flow rate of the hydraulic pump. , Thereby changing the rotation speed of the hydraulic motor. The turning control is based on the steering wheel turning angle (rotation angle) by controlling each rotation speed (same number or difference) and each rotation direction (same direction or reverse direction) for the left and right front wheels. , Becomes possible.

According to a second aspect of the present invention, there is provided a hydraulically driven forklift according to the first aspect of the invention, wherein the change of the traveling speed at the time of turning is performed in accordance with the turning angle of the steering wheel. It is performed by controlling the number of rotations of a motor. Therefore, according to the second aspect of the invention, the rotation speed of the hydraulic motor is automatically controlled in accordance with the steering angle of the steering wheel, so that the traveling speed during turning can be changed without changing the engine rotation speed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. The forklift 1 has its body 2
A pair of left and right front wheels (drive wheels) 3A, 3B are provided at the front of the vehicle body, a pair of left and right rear wheels 4A, 4B are provided at the rear, and a driver's seat 5 is provided above the front of the vehicle body 2. Can be At the front end of the vehicle body 2, a mast 6 that can expand and contract in the vertical direction is attached via a connecting shaft 7 in the vehicle width direction so as to be rotatable in the front-rear direction, and a tilt cylinder 8 that rotates back and forth is provided. It is provided between the vehicle body 2 and the mast 6.

The mast 6 includes a pair of left and right outer frames 9 on the forklift 1 side, and a pair of left and right inner frames 10 which are guided by the outer frames 9 and can move up and down.
0 is provided with a lift cylinder 11. In addition, a lift bracket 12 that is guided by the inner frame 10 and that can move up and down is provided.
A pair of left and right forks 13 is provided via a pair of upper and lower finger bars.

The driver's seat 5 is provided with a seat 15 and a handle 16 located in front of the seat 15.
A head guard 19 is disposed above the head guard 19 via a front pipe 17 and a rear pipe 18 erected from the main body 2 side. Further, a counterweight 20 is provided on the main body 2 behind the seat 15. The pair of left and right front wheels 3A, 3B have rims 3a whose rotary flanges (drive shafts) 22A, 22 of hydraulic motors 21A, 21B, respectively.
By being directly attached to B via the connecting members 23A and 23B, it is linked to the hydraulic motors 21A and 21B. The mounts of the hydraulic motors 21A and 21B are fixed to the vehicle body 2, that is, to the front frame.

An engine 25 is provided on the vehicle body 2 side, and a pair (plurality) of hydraulic pumps (HST tandem pumps) 26A and 26B are directly attached to the engine 25. At that time, the mounting method is engine 2
Rubber mounting with 5 and frame. One hydraulic pump 26A is connected to one hydraulic motor 21A, 21B.
A, 26B, that is, two pumps 2
The corresponding hydraulic pumps 26A, 26B and the hydraulic motors 21A, 21B are connected to a pipe (a hydraulic hose, etc.)
A, 27B.

A pair of left and right rear wheels 4A, 4B are provided so as to be pivotable about the longitudinal centers 29A, 29B with respect to the vehicle body 2, respectively. 30 is an electric change lever, 3
1 is a controller, 32 is an electric accelerator pedal, 3
Reference numeral 3 denotes an electric brake pedal. The operation of the above embodiment will be described below.

FIG. 1, FIG. 2 and FIG. 4 (A) show normal forward and backward traveling. At this time, the left and right front wheels 3
A, 3B and the left and right rear wheels 4A, 4B face in the front-rear direction. The forward / backward traveling is performed by a change lever 30, a forward / backward traveling signal A is input to a controller 31, and the direction of the oil flow of the hydraulic pumps 26A and 26B is switched by the traveling instruction B and C through the controller 31, and the hydraulic motor 21A Change the rotation direction of 21B.

Further, by inputting a vehicle speed command signal d into the controller 31 with an accelerator pedal 32, the engine 25
Of the hydraulic motors 21A and 21B, thereby controlling the speed of the hydraulic motors 21A and 21B. Note that the brake pedal 33
This can be performed by inputting a brake signal into the controller 31.

The turning control is performed on the seat 1 of the driver's seat 5.
5 is operated by operating the handle 16 or the like. At this time, the traveling speed is changed by the position signal H due to the turning angle of the handle 16 (rotation angle).
6A and 26B, the hydraulic motor 21 is controlled.
It can be performed by controlling the rotation speed and the rotation direction of the A and 21B. That is, it can be performed by controlling the rotation speed and rotation direction of both hydraulic motors 21A and 21B according to the turning angle of the handle 16 as described below.

A: When the handle 16 is neutral ...
... As shown in FIG. 4A, the rotation speeds of the left and right hydraulic motors 21A and 21B are the same, and the vehicle travels straight. b: When the steering angle (position signal h) is small ...
As shown in FIG. 4B, by rotating in the same direction in the left and right directions,
Give a difference between the left and right rotation speeds (for example,
G).

C: When the steering wheel turning angle (position signal h) is in the middle: As shown in FIG. 4C, only one front wheel is rotated (for example, only the left front wheel 3A is rotated). ). d: When the steering angle (position signal h) is larger than the middle value ........ As shown in FIG. (For example, head>).

E: When the steering wheel turning angle (position signal h) is the maximum (handle lock)..., As shown in FIG. Are the same. In this case, the turning radius can be minimized.
In the above description, FIGS. 4B to 4E show the case of turning right, but by turning the steering direction of the handle 16 in the opposite direction, turning left is performed in the same manner. . Although the case of forward travel is shown, the same applies to the case of reverse travel. When the vehicle turns left and right, the left and right rear wheels 4A and 4B in the form of a turning caster follow.

Further, if the steering angle of the steering wheel 16 turns sharply beyond a certain angle (for example, a pivot turn in which only one wheel rotates), regardless of the accelerator pedal 32, the rotation speeds of the hydraulic motors 21A and 21B are limited. Is automatically controlled. That is, the hydraulic motor 2 set during the sharp turn
The accelerator pedal 32 up to the rotation speeds 1A and 21B
, But it is not to exceed the set value. As the method, in the case of the first-speed fixed motor: The controller 31 inputs the turning angle of the handle 16 and the rotation speeds of the hydraulic motors 21A and 21B to control the swash plates of the hydraulic motors 21A and 21B.

In the case of the two-speed displacement motor: handle 16
When the turning angle of the hydraulic motor 21A becomes greater than a certain value, the hydraulic motors 21A, 21A
By controlling the switching of the capacity of B, the rotation is performed only at the first speed, and the number of rotations is limited. and so on. As described above, the two-pump two-motor type hydraulic drive system (HST system) is used as the drive type of the forklift 1, so that the turning can be performed by the front wheels 3A and 3B.
There is no need to steer with the rear wheels 4A, 4B. However, in the case of a risette, tire slippage occurs during turning. In this case, the front wheels 3A,
It can follow forward and backward movement and turning by 3B.

The forklift 1 is driven in a two-pump two-motor type hydraulic drive system (HS).
T system) and the left and right front wheels 3
By controlling A and 3B separately, mobility can be improved and the turning radius can be reduced. And each front wheel 3A, 3
B are hydraulic motors 21A attached to the vehicle body 2, respectively.
By directly attaching to the 21B side, the power transmission unit can be simplified and the degree of freedom in layout can be increased. Furthermore, in addition to the high efficiency that is characteristic of the hydraulic drive system, the front differential is not required, and low fuel consumption can be expected by the optimal control of the engine.

The forklift 1 has a driver's seat 5
An operator sitting on the seat 15 of the vehicle operates, for example, a lift lever to operate the lift cylinder 11,
The fork 13 can be moved up and down along the mast 6 via the lift bracket 12 and the like, so that the intended fork operation can be performed. By operating the tilt lever 8 by operating the tilt lever, the mast 6 can be rotated (tilted) around the connecting shaft 7, thereby changing the attitude of the fork 13 via the lift bracket 12 or the like. .

In the above-described embodiment, a pair of right and left rear wheels 4A, 4B is of a swivel caster type that is adapted to follow.
B, a steering type in which one rear wheel 4 is forcibly turned by a cylinder or the like by a handle wheel,
The other rear wheel 4 may be of a swivel caster type. In this case, the steering angle of one rear wheel 4 is fed back to control the hydraulic pumps 26A and 26B, and
By controlling the rotation speeds of 1A and 21B, the vehicle travels straight and turns.

In the above-described embodiment, the change of the traveling speed at the time of turning is performed by controlling the rotation speeds of the hydraulic motors 21A and 21B in accordance with the turning angle of the steering wheel 16. In carrying out the first aspect of the present invention, for example, the traveling speed at the time of turning is controlled by the hydraulic motors 21A, 2A by the accelerator pedal 32 regardless of the turning angle of the steering wheel 16.
The control may be performed by controlling the rotation speed to 1B.

[0026]

According to the first aspect of the present invention, the speed control in forward and backward traveling is performed by changing the direction of oil flow of both hydraulic pumps by the change lever, changing the rotation direction of each hydraulic motor, The number of rotations of the hydraulic motor can be changed by controlling the number of revolutions of the engine and the flow rate of oil of the hydraulic pump by the accelerator pedal. Turning control is based on the steering wheel turning angle (rotation angle), and controls each rotation speed (same number or difference) and each rotation direction (same direction or reverse direction) for the left and right front wheels. Is possible.

Further, as a driving form of the forklift,
By adopting a two-pump two-motor type hydraulic drive system (HST system) and separately controlling the left and right front wheels as drive wheels, the mobility can be improved and the turning radius can be reduced. By attaching each front wheel directly to the hydraulic motor attached to the vehicle body, the power transmission unit can be simplified and the degree of freedom in layout can be increased. In addition to the high efficiency of hydraulic drive systems, which eliminates the need for a front differential, fuel economy can be expected through optimal engine control.

According to the second aspect of the present invention, the traveling speed during turning is automatically controlled by controlling the rotation speed of the hydraulic motor in accordance with the steering angle without changing the rotation speed of the engine. It can be changed, the structure can be simplified, and the traveling speed during turning can be set arbitrarily regardless of the accelerator pedal.

[Brief description of the drawings]

FIG. 1 shows an example of an embodiment of the present invention and is a side view of a hydraulically driven forklift.

FIG. 2 is a partially cutaway plan view of a wheel portion of the hydraulically driven forklift.

FIG. 3 is a system configuration diagram of the hydraulically driven forklift.

FIG. 4 is a schematic plan view illustrating an operating state of the hydraulically driven forklift.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Forklift 2 Body 3A Front wheel 3B Front wheel 4A Rear wheel 4B Rear wheel 5 Driver's seat 6 Mast 8 Tilt cylinder 13 Fork 16 Handle 20 Counterweight 21A Hydraulic motor 21B Hydraulic motor 22A Rotary flange (drive shaft) 22B Rotary flange (drive shaft) ) 25 Engine 26A Hydraulic pump 26B Hydraulic pump 29A Vertical axis 29B Vertical axis 30 Change lever 31 Controller 32 Accelerator pedal 33 Brake pedal A Forward / reverse signal B Travel command C Travel command d Vehicle speed command signal E Engine 25 rotation speed F Hydraulic pressure Revolution of motor 21A G Revolution of hydraulic motor 21B H Position signal Re Brake signal

Claims (2)

[Claims] 1. A vehicle having a pair of left and right front wheels and a pair of left and right rear wheels, a mast and a fork provided on a front end side of the vehicle body, each front wheel being connected to a hydraulic motor mounted on the vehicle body. A plurality of hydraulic pumps driven by the engine are provided on the vehicle body side, and one hydraulic pump is connected to one hydraulic motor correspondingly, and each rear wheel is connected to the vehicle body side. A hydraulically driven forklift, which is provided to be pivotable about a vertical axis. 2. The hydraulically driven forklift according to claim 1, wherein the change of the traveling speed at the time of turning is performed by controlling the rotation speed of a hydraulic motor in accordance with the steering angle of the steering wheel.