JP2539648Y2 - Hydraulic motor controller for fork elevating - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic motor control device for lifting a fork in a forklift.

[0002]

2. Description of the Related Art Conventionally, in a forklift equipped with a hydraulic motor for elevating and lowering a fork, a flow regulator is usually arranged in an oil passage in order to adjust the lowering speed of the fork. This is because a throttle valve is provided so that only a fixed amount of oil flows even when the pressure difference in the oil passage changes, so that the maximum descent speed is kept below a predetermined value regardless of the weight of the load. Things.
On the other hand, there is a method in which the power consumption of the forklift is reduced by using the regenerative operation of the motor when lowering the fork. In this case, in order to achieve an effective regenerative operation of the hydraulic motor (generator). The permissible flow rate per unit time by the flow regulator is increased.

[0003]

However, as described above, when the flow rate of oil per unit time is increased as described above, due to the pressure difference between the upstream portion and the downstream portion in the hydraulic circuit, the weight of the load increases. In such a case, the fork connected to the hydraulic circuit may suddenly descend, causing the load to fall or being damaged. The present invention solves the above-described problems, and provides a fork lift hydraulic motor control device for lowering the fork at an appropriate speed without impairing the regenerative function regardless of the weight of the load in the forklift. The purpose is to provide.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above object, a hydraulic motor control device for raising and lowering a fork according to the present invention comprises a lift cylinder for raising and lowering a piston for supporting a fork by oil pressure of oil, and an oil for storing oil. A hydraulic pump for transferring oil driven by a hydraulic motor on a path of an oil passage connecting the oil tank and the lift cylinder, and a hydraulic pump for moving the oil between the hydraulic pump and the lift cylinder in the oil passage. A flow path opening / closing valve that permits or shuts off the transfer of oil, and a fork up command and a down command are input, and control means is provided for controlling the hydraulic motor and the flow path opening / closing valve. When the fork lowering command is input, the hydraulic motor is driven until the pressure difference between the upstream side and the downstream side of the flow path on-off valve disappears. And controls to open the on-off valve.

[0005]

According to the above construction, the hydraulic motor is driven in the forklift immediately after the fork lowering command is input, so that the oil passage in the upstream of the hydraulic circuit, that is, the oil passage between the discharge side of the hydraulic motor and the flow path on-off valve is opened. By increasing the oil pressure and controlling the flow path on-off valve to be opened when the pressure difference between the pressure of the section and the downstream section, that is, the pressure of the oil passage between the flow path on-off valve and the lift cylinder is eliminated. The fork can be lowered at an appropriate speed, and a regenerative operation can be performed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a forklift on which a hydraulic motor control device for a lifting fork according to the present embodiment is mounted. A mast 3 is fixed to a front portion of a vehicle body 2 on which the control device 1 is mounted, and a fork 5 for mounting a load 4 is mounted on a front surface of the mast 3 so as to be able to move up and down. Mast 3
A piston 7 is inserted into a lift cylinder 6 installed on the back of the cylinder, and the piston 7 moves up and down by oil filled in the lift cylinder 6, and the fork 5 moves up and down in conjunction with the piston. Further, the vehicle body 2 is provided with a switch 8 through which a driver inputs a fork elevating command.

FIG. 2 is a hydraulic circuit diagram. Oil tank 2
1 stores oil for transmitting power through the hydraulic circuit. The oil tank 21 and the lift cylinder 6 are connected by a flow path including oil passages 22a, 22b and the like.
A flow path opening / closing valve (solenoid valve) 27 that allows or shuts off the transfer of oil between the oil tank 21 and the lift cylinder 6 is disposed between the solenoid valve b. Also,
A hydraulic pump 24 driven by a hydraulic motor 23 is provided in the oil passage 22a, and the oil is transferred by the pressure supplied by the hydraulic pump 24. Further, a check valve 25 is provided in the oil passage 22b to prevent the oil transferred to the lift cylinder 6 from flowing backward. Check valve 2
The lift cylinder 6 is provided in the oil passage 22c parallel to the lift cylinder 6.
A throttle valve 26 is provided to limit the flow rate of oil returned from the oil tank 21 to the oil tank 21 per unit time.

In the above hydraulic circuit, when the fork 5 is raised, the hydraulic pump 24 is driven by the hydraulic motor 23, and the solenoid valve 27 is moved leftward in the drawing to open the oil passage 22.
The piston 7 is transferred to the lift cylinder 6 via a and 22b, and the piston 7 supporting the fork 5 is pushed up by the pressure of the oil filled in the lift cylinder 6. on the other hand,
When the fork 5 is lowered, the solenoid valve 27 is similarly opened, whereby the oil filled in the lift cylinder 6 is pushed out to the oil passage 22b by the pressure due to the load transmitted from the piston 7, and the oil passage 22b Is returned to the oil tank 21 via the branched oil passage 22c and the throttle valve 26, through the oil passage 22a and the hydraulic pump 24.

When the fork 5 is lifted, the passage opening / closing valve 2
The oil passage 22a communicates with the oil passage 22b, and the oil passage 22d communicates with the oil passage 22e, so that the oil sent from the oil tank 21 is transferred to the lift cylinder 6 through the oil passages 22a and 22b. On the other hand, when the fork 5 stops,
Oil passage 22a, oil passage 22e, oil passage 22
b and the oil passage 22d are communicated with each other to shut off the upstream side (oil tank side) and the downstream side (lift cylinder side) on the oil path, thereby maintaining the downstream hydraulic pressure at a predetermined level. When the fork 5 descends, the oil passage 22a and the oil passage 22
b, a path through which oil is transferred from the lift cylinder 6 to the oil tank 21 is formed by making the oil passage 22d communicate with the oil passage 22e.

The operation when the fork 5 is lowered is to perform a regenerative operation. The hydraulic motor 23 is reversely rotated by oil flowing in the oil passage 22a in a direction opposite to that when the fork 5 is raised, so that the electric power is regenerated. Charge the battery. Thereby, power consumption can be saved.

FIG. 3 shows a block configuration of the control device. An up switch 31a and a down switch 31b for the driver to perform the raising / lowering operation of the fork 5, a flow path opening / closing valve operating circuit 33, a hydraulic motor driving circuit 35, and a pressure detecting circuit 36 for detecting the pressure in the hydraulic circuit. It is connected to the control circuit 32. Further, the passage opening / closing valve operating circuit 33 is connected to the passage opening / closing valve 27, and the hydraulic motor driving circuit 35 is connected to the hydraulic motor 23.

FIG. 4 is a flowchart of a control procedure when the fork 5 is raised, and FIG. 5 is a flowchart of a control procedure when the fork 5 is lowered. First, a case where the fork 5 is raised will be described with reference to FIG. Before the input of the ascending command, that is, when the fork 5 is stopped, the flow path on-off valve 27
Is closed. Input of the up switch 31a (# 4
When a fork lift command is input to the control circuit 32 according to 1), a motor drive command is output from the control circuit 32 to the hydraulic motor drive circuit 35, and the hydraulic motor 23 operates.
When the operated hydraulic motor 23 drives the hydraulic pump 24 (# 42), the oil is transferred from the oil tank 21 into the oil passage 22a (# 43), but the flow path opening / closing valve 27 is closed. Therefore, the oil pressure in the oil passage 22a increases.

When it is detected from the output from the pressure detecting circuit 36 that measures the upstream pressure and the downstream pressure in the hydraulic circuit that the differential pressure has disappeared (# 44), the control circuit 32 determines whether the pressure difference has been reduced. A flow path opening command is output to the valve operation circuit 33, and the flow path opening / closing valve 27 is opened (# 45). The oil passage 22a and the oil passage 22b communicate with each other by the opening operation of the passage opening / closing valve 27, and the oil is transferred to the lift cylinder 6, and the fork 5 is raised by the oil pressure of the filled oil (# 46). When the fork 5 rises to a desired position and the input of the up switch 31a is stopped (# 41),
A flow path shutoff command is output from the control circuit 32 to the flow path opening / closing valve operation circuit 33, and the flow path opening / closing valve 27 is closed (# 47). The hydraulic motor drive circuit 35 is output simultaneously with the output of the flow path cutoff command.
, The hydraulic motor 23 and the hydraulic pump 24 interlocked with it are stopped (# 48), and the fork 5 stops.

As described above, the reason why the opening / closing valve 27 does not open when the fork 5 is raised, not immediately after the input of the lift command but until the pressure difference between the upstream portion and the downstream portion disappears, will be described below. In the hydraulic circuit, when the fork 5 is stopped, the downstream hydraulic pressure is higher than the upstream hydraulic pressure due to the load of the fork 5 or the like. When the oil is transferred from the downstream side to the upstream side, the fork 5 may temporarily descend. In order to prevent such a temporary lowering operation of the fork 5, immediately after the rising command is input, the hydraulic motor 23 is driven to increase the hydraulic pressure in the upstream portion, and when the differential pressure disappears, the flow path opening / closing valve 27 is closed. It is necessary to control so as to perform the opening operation.

Next, a case where the fork 5 is lowered will be described with reference to FIG. Before the input of the descending command, that is, when the fork 5 is stopped, the flow path opening / closing valve 27 is closed. When a fork lowering command is input to the control circuit 32 by the input of the down switch 31b (# 51), a motor drive command is output from the control circuit 32 to the hydraulic motor drive circuit 35, and the hydraulic motor 23 operates. The activated hydraulic motor 23 drives the hydraulic pump 24 (# 5).
2) The oil is transferred from the oil tank 21 into the oil passage 22a (# 53), but the oil pressure in the oil passage 22a increases because the flow path opening / closing valve 27 is closed.

When the output from the pressure detection circuit 36 detects that the differential pressure has been eliminated (# 54), a motor stop command is output from the control circuit 32 to the hydraulic motor drive circuit 35, and the hydraulic motor 23 is driven. At the same time, the hydraulic pump 24 driven by the hydraulic motor 23 stops (# 55). Subsequently, a flow path opening command is output from the control circuit 32 to the flow path opening / closing valve operation circuit 33, the flow path opening / closing valve 27 is opened, and the oil passage 22a and the oil passage 22b are communicated (# 56). When the passage is connected, the oil in the lift cylinder 6 pressurized downward by the load on the fork 5 is transferred from the lift cylinder 6 to the oil tank 21 by the pressure, and the fork 5 descends (# 5).
7). At this time, the hydraulic motor 23 that was driving the hydraulic pump 24 at the time of ascent is regenerated by the oil flowing in the opposite direction to that at the time of ascending (# 58). When the fork 5 is lowered to a desired position and the input of the down switch 31b is stopped (# 51), a flow path shutoff command is output from the control circuit 32 to the flow path opening / closing valve operating circuit 33, and the flow path opening / closing valve 27 is turned on. The lowering of the fork 5 is stopped by closing and shutting off the transfer of oil to the oil tank 21 (# 59).

As described above, when the fork 5 is lowered, the hydraulic motor 23 is driven immediately after the lowering command is input,
Until the pressure difference between the upstream part and the downstream part disappears, the flow path on-off valve 27
The reason why the opening operation is not performed will be described below. As previously mentioned,
When the fork 5 is stopped, the hydraulic pressure in the downstream portion is higher than the hydraulic pressure in the upstream portion. Therefore, when the flow path opening / closing valve 27 is immediately opened when the descent command is input, the fork 5 may May drop sharply. Immediately after the descent command is input, the hydraulic motor 23 is driven to increase the hydraulic pressure in the upstream part immediately after the descent command is input, and when the differential pressure disappears, the flow path opening / closing valve 27 is stopped. After the opening operation, it is necessary to control the hydraulic motor 23 to stop.

FIG. 6 is a time chart in the present embodiment. T1, T4, and T7 represent periods during which no lift elevating command is input, T2 and T3 represent periods during which an ascending command is input, and T5 and T6 represent periods during which a descending command is input. . In the initial period T5 when the descending command input is started, as described above, the flow path on-off valve 2
With the valve 7 closed, the hydraulic motor 23 is operated to increase the hydraulic pressure on the discharge side of the hydraulic motor, that is, on the upstream portion of the oil path. Subsequently, in the period T6, the hydraulic motor 23 is stopped, the flow path on-off valve 27 is opened, and the regenerative operation is performed.
Note that a DC shunt motor including an armature coil and a field coil is used as the hydraulic motor 23. In the period T5, both coils are energized to operate as a motor, whereas in the period T6, The regenerative operation is performed by energizing only the field coil.

The present invention is not limited to the configuration of the above-described embodiment, but can be variously modified. For example, without using the pressure detection circuit 36, the period until the differential pressure in the hydraulic circuit disappears when the fork 5 descends is experimental. Therefore, the hydraulic motor 23 may be driven without opening the passage opening / closing valve 27 for a required predetermined time. In addition, the flow path on-off valve 2
Regarding the opening operation and the closing operation of 7, the opening / closing operation may not be instantaneous as in the above embodiment, but may be performed stepwise or gradually.

[0020]

As described above, according to the present invention, when the fork is lowered, immediately after the descent command is input, the hydraulic motor is driven without opening the flow path opening / closing valve until the differential pressure in the hydraulic circuit disappears, By stopping the hydraulic motor when the differential pressure disappears and opening the flow path on-off valve to lower the fork, it is possible to lower the fork at an appropriate speed while performing a power regeneration operation. As a result, it is possible to regenerate electric power, and it is possible to prevent the load from being dropped or damaged due to a sudden drop of the fork. Further, in the related art, the lifting and lowering operation of the fork is performed in consideration of the weight of the load. It is possible to reduce the psychological burden on the driver.

[Brief description of the drawings]

FIG. 1 is a side view of a forklift according to an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of the forklift according to one embodiment of the present invention.

FIG. 3 is a block diagram of an apparatus for controlling the hydraulic circuit.

FIG. 4 is a flowchart showing a control procedure when the fork is raised.

FIG. 5 is a flowchart showing a control procedure when the fork is lowered.

FIG. 6 is a time chart at the time of a fork raising and lowering operation.

[Explanation of symbols]

 Reference Signs List 6 lift cylinder 7 piston 21 oil tank 22a, 22b, 22c oil passage 23 hydraulic motor 24 hydraulic pump 27 flow path on-off valve 31a up switch 31b down switch 32 control circuit

Claims (1)

(57) [Scope of request for utility model registration] 1. A hydraulic motor control device for a forklift having a function of regenerating a hydraulic motor when a fork is lowered, comprising: a lift cylinder for raising and lowering a piston for supporting a fork by oil pressure of an oil; an oil tank for storing oil; A hydraulic pump, which is on a path of an oil passage connecting the oil tank and the lift cylinder and is driven by a hydraulic motor to transfer oil, and an oil transfer within the oil passage between the hydraulic pump and the lift cylinder; A flow opening / closing valve for allowing or shutting off, and a control means for inputting a fork raising command and a fork lowering command, and controlling the hydraulic motor and the flow path opening / closing valve, and the control means includes a fork lowering command. When the hydraulic motor is driven, the hydraulic motor is driven until the pressure difference between the upstream side and the downstream side of the flow path on-off valve disappears. A hydraulic motor control device for raising and lowering the fork, wherein the control is performed so as to open the flow path opening / closing valve thereafter.