JP2596107B2 - Hydraulic devices in battery-powered industrial vehicles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power regeneration hydraulic mechanism in a battery-type industrial vehicle.

[Related Art] In a battery-driven industrial vehicle including an electric motor that drives a pump of a hydraulic device for cargo handling, for example, a battery forklift, a hydraulic pump that functions as a motor is used by returning oil from a lift cylinder to generate an electric motor. In some cases, the battery is regenerated by acting as a machine.

As a regenerative hydraulic device as described above, the applicant of the present application has proposed a device shown in FIG. 9 in Japanese Patent Application No. 63-174405. That is, the controller C drives the induction motor 49 based on signals from the limit switches LS1 and LS2 that detect the operation directions of the lift lever 40 and the tilt lever 41 and the potentiometers P1 and P2 that detect the operation amounts of both levers 40 and 41. Then, the hydraulic pump 42 is driven. Then, the tilt control valve 47 is switched and controlled based on the operation of the tilt lever 41, the tilt cylinder 48 is extended and contracted, and the fork tilt operation is performed.

Further, hydraulic oil is supplied from the hydraulic pump 42 to the lift cylinder 45 via the lift control valve 44 held at the position a based on the lifting operation of the lift lever 40, and the fork is raised. Further, based on the lowering operation of the lift lever 40, when the lift control valve 44 is switched to the position c, the return oil from the lift cylinder 45 is forcibly fed to the return line 46 via the control valve 44 by the load of the fork. Return oil is prevented from flowing to the tank side by the check valve 51 and flows to the pump 42 side.

The lowering operation of the lift lever 40 is performed by a limit switch LS.
When 1 is detected, the controller C sets the limit switch L
The regenerative braking mode is executed based on the detected value of S1. When the return oil flows into the hydraulic pump 42 from the return line 46, the hydraulic pump 42 functions as a hydraulic motor by the oil pressure of the return oil and regenerates and drives the electric motor 49. Thus, the electric motor 49 functions as a generator and charges the battery 50.

[Problems to be Solved by the Invention] However, the hydraulic pressure value of the return oil flowing from the lift cylinder 45 to the hydraulic pump 42 is determined by the load of the fork. When the loaded weight of the fork is small and the fork is lowered with a light load, the hydraulic pressure of the return oil also falls below a predetermined value, and is not sufficient to drive the hydraulic pump 42 as a hydraulic motor. For this reason, despite the fork going down,
If the number of revolutions of the electric motor 49 falls below a predetermined value, the electric motor 49 does not perform regeneration, charging of the battery 50 becomes impossible, and the energy saving effect is not exhibited.

Further, if the fork is tilted back and forth with a light load, the tilt cylinder 48 is expanded and contracted by a small amount of return oil discharged from the pump 42, so that the fork is tilted extremely slowly. This leads to reduced efficiency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to save energy by stopping the rotation of the motor when the fork descends under a light load and the motor cannot perform regenerative operation. It is another object of the present invention to provide a hydraulic circuit having a power regeneration function in a battery-type industrial vehicle that enables stable tilt operation even when the fork descends with a light load and reinforces good work efficiency.

Means for Solving the Problems In order to achieve the above object, the present invention provides a lift cylinder for controlling the lifting and lowering of a cargo handling member, a tilt cylinder for controlling the tilting of the cargo handling member, and the lift cylinder and the tilt. Driven to operate the cylinder,
A hydraulic pump that supplies hydraulic oil to these cylinders, is driven to rotate by return oil that returns through a hydraulic oil return path when the lift cylinder is contracted, and functions as a hydraulic motor with an output exceeding a predetermined value; A lift control valve interposed between the cylinder and the hydraulic pump to control the flow of hydraulic oil therebetween, and the lift cylinder interposed between the tilt cylinder and the hydraulic pump to reduce the flow of hydraulic oil between the two. In a battery-type industrial vehicle, a tilt control valve to be controlled and an electric motor driven by electric power supplied from a battery to rotate the hydraulic pump and regenerate the electric power of the battery by a hydraulic pump functioning as a hydraulic motor. A hydraulic device, wherein a traveling direction of return oil flowing in the hydraulic oil return path is selectively switched to a hydraulic pump side and a drain side. And 択切 switching means, a first hydraulic detecting means for detecting a hydraulic pressure value of the return oil, a second hydraulic detecting means for detecting a hydraulic pressure value of the hydraulic pump downstream, said first
Judging means for judging that the output of the hydraulic pump does not have a function as a hydraulic motor and that the tilt cylinder is not operating, based on the detection results of the hydraulic pressure detecting means and the second hydraulic pressure detecting means, Control means for switching the selection switching means so as to change the traveling direction of the return oil flowing in the hydraulic oil return path from the hydraulic pump side to the drain side and stopping the electric motor in accordance with the determination result of the means. Make a summary.

[Operation] The present invention adopts the above-mentioned solution means,
When the determining means determines that the output of the hydraulic pump has no function as a hydraulic motor and that the tilt cylinder is not operating, based on the detection results of the first hydraulic pressure detecting means and the second hydraulic pressure detecting means, The control means switches the selection switching means so as to change the traveling direction of the return oil flowing in the hydraulic oil return path from the hydraulic pump side to the drain side, and stops the electric motor.

Embodiment A first embodiment in which the present invention is embodied in a battery type forklift will be described below in detail with reference to FIGS.

In FIG. 1, a hydraulic pump 1 sucks hydraulic oil stored in an oil tank T via an electromagnetic directional switching valve 2a as selection switching means disposed in a supply pipe line 2, and
It is discharged to the main pipeline 3 in the fork drive hydraulic circuit H. The directional control valve 2a is selectively switchable between two positions a and b.
When the position is switched to the position a (see FIG. 3 (a)) only in the supply direction to the hydraulic pump 1, the passage of hydraulic oil is permitted only in the discharge direction from the hydraulic pump 1 to the tank T.

Further, a lift control valve 4 is disposed in the main conduit 3, and the lift control valve 4 is provided with a, b corresponding to the ascending, neutral and descending operation positions of the lift lever 5 for instructing the fork to move up and down. , c.

The lift control valve 4 controls the amount of hydraulic oil in the bottom chamber 7a of the lift cylinder 7 by switching the position so that the cylinder 7 expands and contracts. In FIG. 2), the main pipe 3 and the lift pipe 6 are communicated with each other, and hydraulic oil is supplied from the hydraulic pump 1 to the bottom chamber 7 a of the lift cylinder 7 to extend the lift cylinder 7.

The lift control valve 4 is at a position c based on the lowering position of the lift lever 5 [FIGS. 3 (a), (b) and 6].
In the above, the lift line 6 and the return line 8 are communicated with each other, and are supplied from the lift cylinder 7 via the lift line 6 and the return line 8 constituting the hydraulic oil return line by a fork descending load. The return oil is fed back between the directional switching valve 2a of the service pipeline 2 and the hydraulic pump 1. Then, the return oil is blocked from flowing to the tank T by the direction switching valve 2a at the position b, flows into the hydraulic pump 1 and drives it.

Further, the lift control valve 4 shuts off the lift line 6 from the main line 3 and the return line 8 at the position b (FIG. 4) based on the neutral position of the lift lever, and the hydraulic oil in the lift cylinder 7 To prevent the flow rate from fluctuating and hold it without shrinking, and open the main pipeline 3 to the downstream side.

A tilt control valve 9 is disposed in the main line 3 downstream of the lift control valve 4 and corresponds to the forward, neutral and rearward operation positions of the tilt lever 10 for instructing the fork to tilt forward and backward. The tilt control valve 9 can be switched to three positions a, b, and c.

The tilt control valve 9 controls the amount of oil in the front chamber 14a and the rear chamber 14b of the tilt cylinder 14 by contracting the position of the tilt cylinder 14 to contract the cylinder 14. In FIGS. 2 and 5), the backward tilt pipe 12 is connected to the tilt pipe 11 via the check valve 11b, and the forward tilt pipe 13 is connected to the drain pipe 15, respectively. The operating oil is supplied to the front chamber 14a, and at the same time, the operating oil in the rear chamber 14b is discharged to the oil tank T, and the tilt cylinder 14 is contracted to tilt the fork backward.

Further, the tilt control valve 9 is set at the position c (FIG. 4) based on the tilt operation of the tilt lever 10 at the backward tilt conduit 12.
To the drain line 15 and the forward tilt line 13 to the tilt line.
The hydraulic pump 1 supplies hydraulic oil to the rear chamber 14b of the tilt cylinder 14 and
The hydraulic oil of 4a is discharged into the oil tank T, the tilt cylinder 14 is extended, and the fork is tilted forward.

Further, the tilt control valve 9 is held at the position b (FIGS. 3 (a) and 3 (b)) based on the neutral position of the tilt lever 11, and connects the forward and backward tilt pipes 13 and 12 respectively to the tilt. It is cut off from both the pipeline 11 and the drain pipeline 15,
The fork is kept in the inclined state at that time without changing the amount of oil in the tilt cylinder 14, and the main conduit 3 is communicated with the oil tank T.

When the lift lever 5 is operated to the raised position and the tilt lever 10 is operated to any one of the forward and backward tilts (for example, the backward tilt), as shown in FIG. 4 via lift cylinder 7 and pump 1
The tilt cylinder 14 is communicated with the pump 1 and the tank T via the tilt control valve 9 at one of the positions a and c (position a in the drawing) to extend and contract. Therefore, the fork performs a tilt operation while rising.

When the lift lever 5 is moved down and the tilt lever 10 is moved to any position (for example, forward tilt), the lift control valve 4 at the position c as shown in FIG. Lift cylinder 7 and pump 1 via
The return oil flowing from the lift cylinder flows into the pump 1 due to the load of the fork. The tilt cylinder 14 is located at either a or c (c in the drawing).
Position), the return oil flowing through the pump 1 from the lift cylinder 7 through the pump 1 is connected to the pump 1 and the tank T via the tilt control valve 9 at the tilt cylinder 14.
Is stretched.

Therefore, the tilt operation can be performed while the fork is lowered as in the case of the ascent, and the fork lift and the tilt can be simultaneously operated.

Now, an electrical configuration for driving the above hydraulic circuit will be described.

The lift side oil pressure sensor 6a as the first oil pressure detection means detects the oil pressure value in the lift line 6, and the tilt side oil pressure sensor 11a as the second oil pressure detection means is connected to the tilt line 1
The pressure in 1 is detected, and a high level (H) and a low level (L) signal are output to the discriminator 22 according to the level of the pressure in the pipelines 6 and 11. That is, the lift-side hydraulic sensor 6a outputs an H signal when the pressure of the return oil passing through the lift pipe 6 is equal to or higher than a predetermined value that allows the pump 1 to function as a hydraulic motor. An H signal is output by detecting the pressure of the hydraulic oil generated by being fed to the tilt cylinder 14 for tilt operation.

As shown in FIG. 7, the discriminator 22 comprises an OR circuit 25, and the direction switching valve is controlled by an H signal output from the discriminator 22.
While keeping 2a at the b position, the controller 20 drives the electric motor 21 with the electric power of the battery 24 to rotate the hydraulic pump 1 connected to the electric motor 21. In addition, the discriminator 22
Outputs the L signal, the directional control valve 2a is switched to the a position, and the controller 20
The power supply to 21 is stopped.

The lift, neutral and lower operation positions of the lift lever 5 are detected by a lift operation position sensor 16 composed of a limit switch, and the operation amount of the lift lever 5 at the raised and lowered positions is a lift operation amount sensor 17 composed of a potentiometer. , And each detection signal is determined by a determination means,
Motor rotation drive means and controller as control means
Entered in 20. The forward tilt, neutral and rearward tilt positions of the tilt lever 10 are detected by a tilt operation position sensor 18 composed of a limit switch, and the amount of operation of the lever 10 in the forward tilt and rearward tilt positions is controlled by a tilt operation composed of a potentiometer. Detected by the quantity sensor 19, each detection signal is input to the controller 20.

When the controller 20 lifts the lift lever 5 according to a detection signal from the lift operation position sensor 16, the controller 20
At 21, the electric motor 21 is driven and controlled to drive the pump 1.
When the tilt lever 10 is tilted forward or backward by a detection signal from the tilt operation position sensor 18, the controller 20 controls the drive of the electric motor 21 so that the pump 1 is driven by the electric motor 21.

The controller 20 calculates the rotation speed of the electric motor 21 with respect to each detection value of the lift operation amount sensor 17 and the tilt operation amount sensor 19. That is, when only the lift lever 5 is operated, the rotation speed command value for the operation amount of the lift lever 5 is based on a predetermined program, and when only the tilt lever 10 is operated, the rotation speed command value for the tilt lever operation amount is based on a predetermined program. Is calculated.

When both levers 5 and 10 are operated at the same time, the controller 20 calculates a rotation speed command value for each operation amount, and the larger rotation speed command value of the two command values is used as the rotation speed command value of the electric motor 21. It is supposed to be. The controller 20 controls the electric power supplied from the battery 24 to the electric motor 21 based on the appropriate rotation speed command value, and controls the electric motor 21 at a rotation speed according to the rotation speed command value.
To adjust the discharge amount of the hydraulic pump 1. That is, it controls the fork up / down speed and the achievement of the tilting in accordance with the respective operation amounts of the lift lever 5 and the tilt lever 10.

Also, when the lift lever 5 is moved down by a heavy load on the fork and the tilt lever 10 is not tilted,
High-pressure return oil flows in the lift pipe 6, and no hydraulic oil is introduced into the tilt pipe 11, so that the pressure in the pipe 11 is low. When the pressure of the return oil is sufficient to cause the pump 1 to function as a motor, the H signal from the lift-side oil pressure sensor 6a and the L signal from the tilt-side oil pressure sensor 11a are input to the discriminator 22. The determiner 22 outputs an H signal to the controller 20 and the direction switching valve 2a. At this time, the induction motor 21 based on the amount of operation of the lift lever 5 by the return oil from the lift cylinder 7
Hydraulic pump 1 rotated at a higher rotation speed than the rotation speed
Works as a hydraulic motor. As a result, the electric motor 21 is driven as a generator, and the battery
24 charges are made.

On the contrary, when the tilt lever 10 is not operated,
When the lift lever 5 is lowered to lower the fork with no load or light load, the hydraulic pressure of the return oil sent from the lift cylinder 7 to the pump 1 is low, and the hydraulic pump 1
Cannot function as a hydraulic motor, and it is impossible for the electric motor 21 to desire the function of a generator. In addition to the regeneration of the electric motor 21 not being performed, the electric motor 21 performs useless rotation even when the fork is descending, and the power consumption of the battery 24 is caused.

To prevent this, an L signal is output from both the lift-side hydraulic sensor 6a and the tilt-side hydraulic sensor 11a in response to the low pressure in the lift line 6 and the tilt line 11, and the discriminator 22 Outputs an L signal. Accordingly, the controller 20 stops the power supply from the battery 24 to the electric motor 21, and the direction switching valve 2a is switched to the position a as shown in FIG. Is washed away. As a result, not only does the electric motor 21 not rotate following the rotation of the pump 1, nor is the electric motor 21 driven in accordance with the operation of the lift lever 5, and the power consumption of the battery 24 is avoided. ,
Energy saving is effectively performed.

When the fork moves the lift lever 5 down and the tilt lever 10 is tilted under heavy load, the hydraulic pump 1 rotates via the electric motor 21 driven at a rotation speed based on the lever operation amount, and the tilt pipe is rotated. The hydraulic oil is pumped into the passage 11, and return oil based on the heavy load of the fork is introduced into the lift pipe 6. Then, an H signal is output to the discriminator 22 from both the hydraulic sensors 6a, 11a based on the high pressure in both the lift and tilt pipes 6, 11. Based on this, the controller 20 connects the power source of the battery 24 to the electric motor 21 and sets the directional control valve 2a to b
Hold in position.

At this time, the motor 2 based on the operation amount of the tilt lever 10
1, that is, when the rotation speed of the pump 1 based on the pressure of the return oil is higher than the rotation speed of the pump 1, the return oil causes the hydraulic pump 1 to function as a hydraulic motor, the electric motor 21 to function as a generator, and the battery 24 Charge. Then, the return oil is pumped from the pump 1 into the tilt cylinder 14. Therefore, when the heavy load of the fork is lowered, the return oil from the lift cylinder 7 is used for the tilt operation after being used for charging the battery 24, and the hydraulic oil is effectively used.

When the lift lever 5 is lowered and the tilt lever 10 is tilted forward or backward when the fork is lightly loaded, the fork operates via the electric motor 21 at a rotation speed based on the amount of operation of the tilt lever 10. The hydraulic oil is forcibly introduced into the tilt pipe 11 by the pump 1. The tilt-side oil pressure sensor 11a outputs an H signal and the lift-side oil pressure sensor 6a outputs an L signal according to the pressure of the hydraulic oil. Based on this, the controller 20 drives the electric motor 21 with the battery power by the H signal output from the discriminator 22, the directional control valve 2a is held at the position b, and the hydraulic oil supplied from the tank T A tilt operation is performed.

Therefore, when the fork descends with a light load, the tilt operation of the fork is performed at a normal speed, thereby avoiding adverse effects on work efficiency.

The present invention is not limited to the embodiment described above. For example, a DC motor may be used in place of the induction motor 21 or, as shown in FIG. A switching valve 8a is provided, and the direction switching valve 8a is switched to the positions a and b according to the pressure of the return oil, so that the traveling direction of the return oil is upstream and downstream of the regenerative check valve 2b, that is, the tank T Or the pump 1 side, or the lift side hydraulic sensor 6a is connected to the bottom chamber of the lift cylinder 7.
7a, a tilt-side hydraulic sensor 11a is provided between the connection point between the pump 1 of the main line 3 and the tilt line 11, and furthermore, a position downstream of the check valve 11b of the tilt line 11. It is of course possible to make any change without departing from the spirit of the invention, such as detecting only the hydraulic oil pumped from the main pipeline 3 at the pressure at which the tilt cylinder 14 should be driven.

[Effects] As described above in detail, according to the present invention, when the fork descends at a light load and the motor cannot perform regenerative operation, it is possible to save energy by stopping the rotation of the motor, Furthermore, even when the fork descends with a light load, stable tilt operation can be performed, and an excellent effect that good working efficiency is guaranteed is exhibited.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a hydraulic and electrical configuration of the present invention, FIG. 2 is a circuit diagram showing a hydraulic and electrical configuration when a fork is raised, and FIGS. 3 (a) and 3 (b) ) Is a hydraulic and electrical circuit diagram showing the position of the directional control valve when the fork descends under heavy load and light load, respectively. FIG. 4 shows the hydraulic and electrical configuration when the fork is tilted forward. FIG. 5 is a circuit diagram showing a hydraulic and electrical configuration when the fork is tilted backward, FIG. 6 is a circuit diagram when the fork is lowered and tilted forward, and FIG. 7 is a discriminator. FIG. 8 is a circuit diagram showing another example of the selection switching means, and FIG. 9 is a circuit diagram showing a conventional example. Hydraulic pump 1, direction switching valve 2a as selection switching means, lift control valve 4, lift side hydraulic sensor 6a as first detection means, lift cylinder 7, direction switching valve 8a as selection switching means, second detection means Tilt Side Oil Pressure Sensor
11a, a tilt cylinder 14, a controller 20 as a control means, an induction motor 21, a discriminator 22 as a judgment means, and a battery 24.

Claims (1)

(57) [Claims] A lift cylinder for controlling the lifting and lowering of the cargo handling member; a tilt cylinder for controlling the tilting of the cargo handling member; and a hydraulic cylinder driven to operate the lift cylinder and the tilt cylinder to supply hydraulic fluid to these cylinders. A hydraulic pump driven by return oil returning through a hydraulic oil return path when the lift cylinder is contracted, and functioning as a hydraulic motor with an output exceeding a predetermined value; and between the lift cylinder and the hydraulic pump. A lift control valve that controls the flow of hydraulic oil between the two, and the tilt cylinder and the hydraulic pump are interposed between the tilt cylinder and the hydraulic pump,
A tilt control valve for controlling the flow of hydraulic oil between the two, and an electric motor driven by electric power supplied from the battery to rotate the hydraulic pump and regenerate the electric power of the battery by the hydraulic pump functioning as a hydraulic motor And a selection switching means for selectively switching a traveling direction of return oil flowing through the hydraulic oil return path to a hydraulic pump side and a drain side, and a hydraulic value of the return oil. First hydraulic pressure detecting means for detecting the hydraulic pressure, second hydraulic pressure detecting means for detecting the hydraulic pressure value on the downstream side of the hydraulic pump, and based on the detection results of the first hydraulic pressure detecting means and the second hydraulic pressure detecting means. Judging means for judging that the output of the hydraulic pump does not have a function as a hydraulic motor and that the tilt cylinder is not operating; Control means for switching the selection switching means to change the traveling direction of the return oil flowing in the hydraulic oil return path from the hydraulic pump side to the drain side and stopping the electric motor in accordance with the result. Hydraulic equipment.