JPH0549800U - Hydraulic motor controller for lifting forks - Google Patents

Abstract

(57) [Summary] [Purpose] In a hydraulic motor control device for a forklift, which has a function of regenerating a hydraulic motor when the fork descends, a fork is provided even if the load is light without impairing the regenerative function more than necessary. Provided is a hydraulic motor control device for raising and lowering a fork, which can lower the fork at an appropriate speed when the fork is lowered. [Structure] When the weight of the load is appropriate when the fork is lowered, the fork is lowered while regenerating the hydraulic motor. On the other hand, when the load is light and the lowering speed is slow, the hydraulic motor is lowered. Is operated in the reverse rotation to control the oil transfer.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a hydraulic motor control device for lifting a fork in a forklift.

[0002]

[Prior Art]

 Conventionally, in a forklift equipped with a hydraulic motor for raising and lowering a fork, when the fork is lowered, the regenerative operation of the hydraulic motor is used to convert the position energy of the fork into electric energy to consume the forklift. Some are saving power. That is, when lowering a fork that has been raised by hydraulic pressure, the flow path on-off valve (solenoid valve) in the hydraulic circuit is opened immediately after the lowering command is input, and the time when the fork and the load of the load raise it The battery provided in the forklift is charged by reversing the hydraulic motor by the oil flowing in the reverse direction to regenerate the electric power.

[0003]

[Problems to be solved by the device]

 However, in the above-mentioned forklift, when the fork descends, resistance due to frictional damage occurs between the fork and the mast supporting the fork, so the descending speed of the fork decreases depending on the weight of the load. May or may not descend at all. The present invention solves the above-mentioned problems, and provides a hydraulic motor control device for raising and lowering a fork, which lowers the fork at an appropriate speed without impairing the regeneration function regardless of the weight of the load on the forklift. The purpose is to provide.

[0004]

[Means for Solving the Problems]

 In order to achieve the above object, a hydraulic motor control device for lifting a fork according to the present invention comprises a lift cylinder for lifting and lowering a piston supporting a fork by oil pressure of oil, an oil tank for storing oil, the oil tank and the lift. Allows or blocks the transfer of oil between the hydraulic pump, which is driven by a hydraulic motor and transfers oil, on the oil passage that connects to the cylinder, and between the hydraulic pump and the lift cylinder, which is inside the oil passage. And a control means for driving and controlling the hydraulic motor and the flow path opening / closing valve to which a command to raise and lower the fork are input, and the control means detects the rotational speed of the hydraulic motor. Thus, the rotation of the hydraulic motor is controlled in a predetermined acceleration / deceleration pattern when a fork lowering command is input.

[0005]

[Action]

 According to the above configuration, when the fork is lowered, normally, the positive direction exciting current is supplied only to the field coil of the hydraulic motor to lower the fork while regenerating the hydraulic motor. On the other hand, when the load of the load is light, the field coil is energized in the positive direction and the armature coil of the hydraulic motor is energized in the reverse direction to reversely rotate the hydraulic motor. Control to lower the fork. By controlling in this way, when the fork is lowered, the fork can be lowered at an appropriate speed regardless of the weight of the load.

[0006]

【Example】

 An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a forklift equipped with a hydraulic motor controller for a lifting fork according to this embodiment. A mast 3 is fixed to a front part 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 the front surface of the mast 3 so as to be able to move up and down. Further, the piston 7 is inserted into the lift cylinder 6 installed on the rear surface of the mast 3, and the oil filled in the lift cylinder 6 causes the piston 7 to move up and down, and the fork 5 moves up and down in conjunction therewith. Further, the vehicle body 2 is provided with a switch 8 for the driver to input a fork lift command.

FIG. 2 shows a hydraulic circuit for moving the fork up and down. The oil tank 21 stores oil that flows in the hydraulic circuit to transmit power. The oil tank 21 and the lift cylinder 6 are connected by a flow path including oil passages 22a and 22b. Between the oil passage 22a and the oil passage 22b, the oil tank 21 and the lift cylinder 6 are connected. A passage opening / closing valve (solenoid valve) 27 that allows or blocks the transfer of oil is provided. The oil passage 22a is equipped with a hydraulic pump 24 driven by a hydraulic motor 23, 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 reverse flow of the oil transferred to the lift cylinder 6. In the oil passage 22c parallel to the check valve 25, a throttle valve 26 for limiting the flow rate of the oil returned from the lift cylinder 6 to the oil tank 21 per unit time is arranged.

In the above hydraulic circuit, when the fork 5 rises, the hydraulic motor 23 drives the hydraulic pump 24, and further the solenoid valve 27 is moved leftward in the drawing to open the oil, so that the oil is passed through the oil passages 22a and 22b. The lift cylinder 6 is transferred to the lift cylinder 6, and the piston 7 supporting the fork 5 is lifted by the pressure of the oil filled in the lift cylinder 6. On the other hand, when the fork 5 descends, by similarly opening the solenoid valve 27, 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, It is returned to the oil tank 21 through an oil passage 22c branched from the oil passage 22b, a throttle valve 26, an oil passage 22a and a hydraulic pump 24.

When the fork 5 is raised, the oil sent from the oil tank 21 is discharged by connecting the oil passage 22a and the oil passage 22b and the oil passage 22d and the oil passage 22e by the passage opening / closing valve 27, respectively. The oil is transferred to the lift cylinder 6 through the oil passages 22a and 22b. On the other hand, when the fork 5 is stopped, the solenoid valve 27 is moved to the right side in the drawing to be closed, so that the upstream side (oil tank side) and the downstream side (lift cylinder side) on the path by the oil passage are shut off. As a result, the hydraulic pressure on the downstream side is maintained at a predetermined level. Further, when the fork 5 descends, the oil passage 22a and the oil passage 22b are connected to each other and the oil passage 22d and the oil passage 22e are connected to each other so that the oil is transferred from the lift cylinder 6 to the oil tank 21. To form.

The operation of lowering the fork 5 is to perform a regenerative operation. The oil flowing in the oil passage 22a in the direction opposite to the upward direction causes the hydraulic motor 23 to reversely rotate to perform a regenerative operation of electric power. And charge the battery. This can save power consumption. As the hydraulic motor 23, a DC shunt motor including an armature coil and a field coil is used.

FIG. 3 shows a block configuration of the control device. An up switch 31a and a down switch 31b for the driver to move the fork 5 up and down, a passage opening / closing valve actuation circuit 33, a rotation speed detection circuit 34 for detecting the rotation speed of the hydraulic motor 23, and a hydraulic motor drive circuit. 35 is connected to the control circuit 32. Further, the passage opening / closing valve 27 is connected to the passage opening / closing valve operating circuit 33, and the hydraulic motor 23 is connected to the hydraulic motor drive circuit 35. The rotation speed detection circuit 34 is connected to the hydraulic motor 23.

FIG. 4 shows a flow chart of a control procedure when the fork 5 is raised, and FIG. 5 shows a flow chart of a control procedure when the fork 5 is lowered. First, the case of raising the fork 5 will be described with reference to FIG. Before the input of the rising command, that is, when the fork 5 is stopped, the flow path opening / closing valve 27 is closed. When the fork lift command is input to the control circuit 32 by the input of the up switch 31a (# 41), the motor drive command is output from the control circuit 32 to the hydraulic motor drive circuit 35, and the field coil and armature of the hydraulic motor 23 are output. The coils are energized in the forward direction to rotate the hydraulic motor 23 in the forward direction (# 42, # 43). Simultaneously with the output of the motor drive command described above, a flow path opening 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 opened (# 44). By the communication of the oil passage 22a and the oil passage 22b by the opening operation, a passage for transferring the oil from the oil tank 21 to the lift cylinder 6 is formed. The operated hydraulic motor 23 drives the hydraulic pump 24, whereby the oil is transferred from the oil tank 21 to the lift cylinder 6, and the fork 5 is raised by the hydraulic pressure of the filled oil (# 45).

When the fork 5 rises to a desired position and the input of the up switch 31a is stopped (# 41), the control circuit 32 outputs a flow path shutoff command to the flow path opening / closing valve actuation circuit 33 to open and close the flow path. The valve 27 is closed (# 46). Simultaneously with the output of the flow path cutoff command, a motor stop command is output to the hydraulic motor drive circuit 35 to stop the power supply to the field coil and the armature coil of the hydraulic motor 23 to stop the hydraulic motor 23 (# 47) and the hydraulic pump 24 interlocked therewith, and the fork 5 stops (# 48).

Next, a case where the fork 5 is lowered will be described with reference to FIG. Before inputting the descending instruction, 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 flow path opening 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 opened. After being opened (# 52), the oil passage 22a and the oil passage 22b are communicated with each other to form a passage for transferring the oil from the lift cylinder 6 to the oil tank 21. Then, when the field coil energization command is output from the control circuit 32 to the motor drive circuit 35, the field coil of the hydraulic motor 23 is energized in the positive direction (# 53), and the energization of the armature coil is stopped. (# 54).

When the oil transfer path is formed by the opening operation of the flow path opening / closing valve 27, when the load 4 having an appropriate weight is placed (hereinafter, referred to as “normal time”), the fork 5 and its product are stacked. The oil in the lift cylinder 6 that is pressed downward by the load of the object 4 is transferred from the lift cylinder 6 to the oil tank 21 by the pressure, and the fork 5 starts to descend (# 56). Further, the hydraulic motor 23, which was driving the hydraulic pump 24 at the time of rising, is regenerated by rotating the hydraulic motor 23 in the opposite direction to the oil flowing in the direction at the time of rising (# 57).

However, when the fork 5 descends, resistance due to frictional damage or the like occurs between the fork 5 and the mast 3 that supports the fork 5 so that the fork 5 can be moved up and down. When the fork 5 is not mounted (hereinafter, referred to as a light load), the descending speed of the fork 5 may decrease or may not descend at all. Then, the number of rotations per unit time of the hydraulic motor 23 that is reversely rotated by the oil flowing in the opposite direction is measured by the number of rotations detection circuit 34, and the output signal from the number of rotations detection circuit 34 is controlled by the control circuit 32. When the rotation speed is less than the predetermined value (# 55), the armature coil of the hydraulic motor that has been deenergized is energized in the reverse direction (# 58), and the hydraulic motor 23 is rotated in the reverse direction (# 58). As a result, the hydraulic pump 24 interlocking with the hydraulic motor 23 is operated in the opposite direction to the upward movement to transfer the oil to the oil tank 21 and lower the fork 5 (# 60).

When the fork 5 is lowered to a desired position and the input of the down switch 31b is stopped (# 51), the control circuit 32 outputs a flow path shutoff command to the flow path opening / closing valve actuation circuit 33 to open and close the flow path. The valve 27 is closed (# 61) to shut off the oil transfer to the oil tank 21. Then, the control circuit 32 outputs an energization stop command to the hydraulic motor drive circuit 35 to stop the energization of the field coil and the armature coil, thereby causing the hydraulic motor 23 to perform a regenerative operation in a normal time or a light-duty operation. The reverse rotation operation under load is stopped (# 62), and the lowering of the fork 5 is stopped (# 63).

FIG. 6 is a time chart in this embodiment. For T1, T4, T5, T8, and T9, the up switch 31a and the up switch 31b are turned off and the fork up / down command is not input, and for T2 and T3, the up switch 31a is turned on and the up command is input. The periods T6 and T7 represent the period during which the down switch 31b is turned on and the descending command is input. During the stop period T1, T4, T5, T8, T9 of the fork 5, since the hydraulic motor 23 is stopped and the regenerative operation by reverse rotation is not performed, the field coil and the armature coil are not connected. Not energized.

In the initial period T2 when the rise command input is started, the positive direction exciting current is applied to the field coil and the armature coil of the hydraulic motor 23 to rotate the hydraulic motor 23 in the positive direction. To accelerate. When the rotational speed of the hydraulic motor 23 reaches a predetermined value, the field coil and the armature coil are energized to raise the fork 5 as shown in period T3. During the period T4 in which the fork 5 has risen to the desired position, by stopping the energization of the field coil and the armature coil, the rotational speed of the hydraulic motor 23 in the positive direction gradually decreases, and the fork 5 eventually stops. To do.

In the initial period T6 when the down command input is started, in the normal time, the reverse rotation of the hydraulic motor 23 is gradually accelerated by the oil flowing in the direction opposite to the direction in which the fork 5 is raised, and By supplying an exciting current in the positive direction only to the field coil of the hydraulic motor 23, the hydraulic motor 23 is regenerated. Then, during a period T7 when the reverse rotation speed reaches a predetermined value, the field coil is kept energized, and the fork 5 is lowered while the hydraulic motor 23 is regeneratively operated. On the other hand, when the load is light, the field coil of the hydraulic motor 23 is energized in the forward direction and the armature coil is energized in the reverse direction to reversely rotate the hydraulic motor 23. Lower the fork 5. In the period T8 when the fork 5 descends to the desired position, the flow passage opening / closing valve 27 is closed and the energization of the field coil and the armature coil is stopped, so that the rotational speed of the hydraulic motor 23 in the reverse direction is gradually increased. It will decrease and the fork 5 will stop soon.

The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, during the raising and lowering operation of the fork 5, the rotation speed is measured at a predetermined interval using the rotation speed detection circuit 34, and the field coil and the armature coil of the hydraulic motor 23 are energized according to the measured values. By controlling the forward rotation and the reverse rotation of the motor by controlling the timing, the excitation direction and the conduction ratio, not only the fork 5 lowering at a light load but also the fork 5 ascending / descending operation at the normal time can be performed. The reverse rotation of the hydraulic motor 23 can be used also when the hydraulic motor 23 is stopped and controlled, and the hydraulic motor 23 can be controlled more accurately by the stop control. It is possible to realize the lifting operation of the fork 5 that responds to the lifting command at high speed. Further, in the above-described embodiment, the rotation speed of the hydraulic motor 23 is measured by the rotation speed detection circuit 34 in order to detect the speed at which the fork 5 descends. However, as another method, for example, the hydraulic circuit is moved in the hydraulic circuit. The rotation speed can also be detected by measuring the flow rate of oil that is generated per unit time, measuring the descending speed of the piston 7 that descends in the lift cylinder 6, or detecting the power generation voltage of the regenerative operation. Similarly, the function of detecting the descending speed of the fork 5 can be obtained.

[0022]

[Effect of the device]

 As described above, according to the present invention, when the fork descends, normally, by supplying a positive direction exciting current only to the field coil of the hydraulic motor, the hydraulic motor is regenerated and the fork is moved. On the other hand, when the load of the load is light, the field coil is energized in the forward direction and the armature coil is energized in the reverse direction to reversely rotate the hydraulic motor. By lowering the fork, the fork can be lowered at an appropriate speed when the fork is lowered, regardless of the weight of the load and without impairing the regenerative operation more than necessary. As a result, it is possible to reduce the psychological burden on the driver, who has conventionally operated the lifting of the fork while considering the weight of the load, and to operate the forklift stably.

[Brief description of 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 a forklift according to an embodiment of the present invention.

FIG. 3 is a block configuration diagram of a device that controls the hydraulic circuit.

FIG. 4 is a flowchart showing a control procedure when a fork is lifted.

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

FIG. 6 is a time chart when the fork is raised and lowered.

[Explanation of symbols]

 1 Hydraulic Motor Control Device 6 Lift Cylinder 7 Piston 21 Oil Tank 22a, 22b, 22c Oil Passage 23 Hydraulic Motor 24 Hydraulic Pump 27 Flow Opening Valve 31a Up Switch 31b Down Switch 32 Control Circuit

Claims (1)

[Scope of utility model registration request] 1. A hydraulic motor control device for a forklift having a function of regeneratively operating a hydraulic motor when a fork descends, a lift cylinder for moving a piston supporting a fork up and down by oil pressure of oil, and an oil tank for storing oil. A hydraulic pump that is on the path of an oil passage that connects the oil tank and the lift cylinder and that is driven by a hydraulic motor to transfer oil, and that transfers oil between the hydraulic pump and the lift cylinder that is in the oil passage. And a control means for driving and controlling the hydraulic motor and the flow passage opening / closing valve, and a rise / fall command of a fork being inputted. The rotation speed of the hydraulic motor is detected and the hydraulic motor is rotated in a predetermined acceleration / deceleration pattern when a fork down command is input. A hydraulic motor control device for raising and lowering a fork, which is characterized by controlling the rotation.