JP7231014B2 - Hydraulic circuits in electric industrial vehicles - Google Patents

Description

The present invention relates to hydraulic circuits in electric industrial vehicles.

In an electric forklift as an electric industrial vehicle, a hydraulic pump is driven by a motor that receives power from a battery built into the main body, and hydraulic pressure generated by this hydraulic pump is supplied to a hydraulic cylinder to raise and lower cargo. have Hydraulic oil sent from the hydraulic pump is supplied to the hydraulic cylinder via the spool valve. Such a spool valve is a manual type in which an operator operates an operating portion such as a lever and moves the spool of the spool valve using the operating force at this time to control the hydraulic oil supplied to the hydraulic cylinder. A spool valve is used.

In addition, in such an electric forklift, there has been proposed an electric forklift that uses an electromagnetic proportional spool valve instead of the manual spool valve (see Patent Document 1). This electromagnetic proportional spool valve has a configuration in which a solenoid is used as an actuator, and the spool is moved by driving the solenoid based on an electric signal and pilot pressure.

Japanese Unexamined Patent Application Publication No. 2013-203510

Since the electromagnetic proportional spool valve controls its operation based on electrical signals, when using an electromagnetic proportional spool valve in an electric forklift, the operating part can be placed in any position, giving greater design freedom. There is an advantage that the degree is improved.

On the other hand, when an electromagnetic proportional spool valve is used in an electric forklift, it is necessary to drive the hydraulic pump to ensure the pilot pressure even when lowering the load. That is, when a manual spool valve is used in an electric forklift, the spool is moved by the operating force of the operator. Occasionally, cargo is lowered by its own weight, so there is no need to drive the hydraulic pump. On the other hand, when an electromagnetic proportional spool valve is used in an electric forklift, pilot pressure must be supplied to the electromagnetic proportional spool valve even when the spool is moved to lower the load. For some reason it is necessary to drive the hydraulic pump.

Therefore, when an electromagnetic proportional spool valve is used in an electric forklift, it is necessary to drive the hydraulic pump even when lowering the cargo, and the motor that drives the hydraulic pump consumes power from the battery. Electric forklifts preferably use less power.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic circuit for an electric industrial vehicle that can reduce the amount of electric power used in the electric industrial vehicle.

The present invention is a hydraulic circuit in an electric industrial vehicle that drives a hydraulic pump with a motor and supplies hydraulic pressure generated by the hydraulic pump to a hydraulic cylinder to raise and lower cargo, and moves a spool according to operation of an operation unit. a hydraulically piloted electromagnetic proportional spool valve for supplying hydraulic pressure to the hydraulic cylinder, an accumulator, and a pump line connected to the hydraulic pump to supply a pilot pressure to the hydraulically piloted electromagnetic proportional spool valve. a branch passage connecting a passage and the accumulator; an on-off valve disposed in the branch passage and opened when the cargo is lifted or lowered; disposed between the branch passage and the pump line; a check valve that allows hydraulic fluid to flow from the pump line to the branch passage and blocks hydraulic fluid flow from the branch passage to the pump line.

According to this invention, it is possible to reduce the amount of electric power used in an electric industrial vehicle.

1 is a schematic diagram of an electric forklift as an electric industrial vehicle; FIG. 1 is a circuit diagram of a hydraulic circuit in an electric industrial vehicle according to an embodiment of the invention; FIG. 1 is a circuit diagram of a hydraulic circuit in an electric industrial vehicle according to an embodiment of the invention; FIG. 1 is a circuit diagram of a hydraulic circuit in an electric industrial vehicle according to an embodiment of the invention; FIG. 1 is a circuit diagram of a hydraulic circuit in an electric industrial vehicle according to an embodiment of the invention; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. First, the configuration of an electric industrial vehicle to which the hydraulic circuit in the electric industrial vehicle according to the embodiment of the invention is applied will be described. FIG. 1 is a schematic diagram of an electric forklift as an electric industrial vehicle.

This electric forklift includes a main body 93 having front wheels 91 as running wheels and rear wheels 92 as steering wheels, a seat 98 for an operator to sit on, a steering wheel 95 for operating the rear wheels 92, It has a fork 96 as an elevating member that moves up and down with respect to an elevating mechanism 94 arranged on a main body 93 while supporting a cargo handling device 97, and a lever 23 as an operation unit for performing elevating operation of the fork 96. A battery 5, which will be described later, is built in the main body 93, and this electric forklift truck is driven by electric energy of the battery 5, and the hydraulic pump 22 driven by the battery 5 lifts and lowers the fork 96. .

2 to 5 are circuit diagrams of hydraulic circuits in electric industrial vehicles according to embodiments of the present invention. 2 shows a state in which the fork 96 loaded with the cargo 97 is raised, FIG. 3 shows a state in which the pressure of the hydraulic oil in the accumulator 26 exceeds a set value when the fork 96 is raised, and FIG. FIG. 5 shows the state in which the fork 96 is lowered and the pressure in the accumulator 26 becomes smaller than the set value when the fork 96 is lowered.

This hydraulic circuit comprises a control unit 1 having a lift part 2 for raising and lowering the fork 96 and a tilt part 3 for tilting the fork 96 together with the lifting mechanism 94 . The lift part 2 is connected to a hydraulic cylinder 28 for raising and lowering the fork 96 by being supplied with hydraulic pressure via a hydraulic pilot type electromagnetic proportional spool valve 41 and a hydraulic oil supply line 16 . Also, the tilt part 3 is connected to a hydraulic cylinder 29 for receiving hydraulic pressure supplied through a hydraulic pilot type electromagnetic proportional spool valve 42 and hydraulic oil supply pipes 17 and 18 to tilt the fork 96 together with the lifting mechanism 94. there is

The control unit 1 is supplied with hydraulic oil stored in the tank 4 by the action of the hydraulic pump 22 . The hydraulic pump 22 is connected to a motor 21 that rotates using the power of the battery 5 and is driven by the motor 21 . High-pressure hydraulic oil supplied from the hydraulic pump 22 is supplied to the lift part 2 and the tilt part 3 through the center bypass passage 11 and the parallel passage 13 and discharged to the tank 4 through the tank passage 12 .

A portion of the high-pressure hydraulic fluid supplied from the hydraulic pump 22 to the control unit 1 is preferentially supplied to the power steering mechanism for assisting the operation of the steering 95 via the conduit 19 by the priority valve 34, A portion is supplied to Lift Part 2. The control unit 1 is provided with a main relief valve 32 connected to the center bypass passage 11 and a steering relief valve 33 connected to a conduit 19 leading to the power steering mechanism.

Hydraulic oil supplied from the hydraulic pump 22 and passed through the priority valve 34 becomes the pressure necessary to operate the pilot spools in the hydraulic pilot type electromagnetic proportional spool valves 41 and 42 by the action of the sequence valve 36, and the hydraulic pilot type The pilot spool corresponding to the pair of solenoids 43 and 44 in the electromagnetic proportional spool valve 41 and the pilot spool corresponding to the pair of solenoids 45 and 46 in the hydraulic pilot type electromagnetic proportional spool valve 42 are sent. At this time, the pressure of the hydraulic oil is maintained at a constant pressure or less corresponding to the pressure resistance of the hydraulic pilot type electromagnetic proportional spool valves 41 and 42 by the action of the pressure reducing valve 35 .

In the lift part 2, when the main spool of the hydraulic pilot type electromagnetic proportional spool valve 41 is arranged at the position shown in FIG. passes through the main spool in hydraulically piloted electromagnetic proportional spool valve 41 and is supplied to hydraulic cylinder 28 via supply line 16 . As a result, the piston of the hydraulic cylinder 28 rises, and the fork 96 rises together with the load handling 97 .

On the other hand, when the main spool of the hydraulic pilot type electromagnetic proportional spool valve 41 is arranged at the position shown in FIG. Acts on lock valve 38 . As a result, the check valve in the pilot lock valve 38 opens, the lift lock poppet 37 opens, and the working oil in the hydraulic cylinder 28 flows out. As a result, the piston of the hydraulic cylinder 28 descends, and the fork 96 descends together with the cargo handling 97 .

In the flow path 14 between the center bypass passage 11 functioning as a hydraulic oil supply path connected to the hydraulic pump 22 and the pressure reducing valve 35 disposed in the pilot pressure supply path to the hydraulic pilot type electromagnetic proportional spool valve 41. is connected to a branch 15 whose one end is connected to an accumulator 26 . Hydraulic oil is allowed to flow from the center bypass passage 11 connected to the hydraulic pump 22 to the branch passage 15 between the branch passage 15 and the center bypass passage 11. A check valve 30 is provided to block the flow of hydraulic oil. Further, an electromagnetic on-off valve 27 is arranged in the branch passage 15, and a pressure sensor 25 for detecting the pressure of hydraulic oil in the accumulator 26 is arranged between the electromagnetic on-off valve 27 and the accumulator 26. It is An unloading mechanism 31 is connected to the center bypass passage 11 to operate the hydraulic cylinders 28 and 29 only when the operator is seated on the seat 98 .

In the tilt part 3, when the main spool in the hydraulic pilot type electromagnetic proportional spool valve 42 is moved by the action of the pair of solenoids 45 and 46 in the hydraulic pilot type electromagnetic proportional spool valve 42, the supply line connected to the hydraulic cylinder 29 17 or supply line 18 is selectively supplied with hydraulic oil. As a result, the movement of the piston of the hydraulic cylinder 29 causes the fork 96 to tilt together with the lifting mechanism 94 to perform a tilting operation.

This hydraulic circuit has a control section 24 . This control unit 24 is composed of a computer in which software is installed. The function of each part included in this control part 24 is realized by executing software installed in the computer. The control unit 24 is connected to the lever 23, the motor 21, the electromagnetic on-off valve 27, and the pressure sensor 25 as an operation unit for performing the lifting operation of the fork 96 described above, and receives signals from these, or Send a command signal to The control unit 24 is also electrically connected to a pair of solenoids 43 and 44 in the hydraulic pilot type electromagnetic proportional spool valve 41 and a pair of solenoids 45 and 46 in the hydraulic pilot type electromagnetic proportional spool valve 42 .

In the hydraulic circuit configured as described above, the operator operates the lever 23 when the fork 96 is lifted together with the load handling 97 . This operation signal is transmitted to the control unit 24 , and the control unit 24 drives the hydraulic pump 22 by rotating the motor 21 . High-pressure hydraulic fluid sent from the hydraulic pump 22 is supplied to spools corresponding to a pair of solenoids 43 and 44 via a check valve 30 and a pressure reducing valve 35, where pilot pressure is generated. As a result, the main spool in the hydraulic pilot type electromagnetic proportional spool valve 41 becomes movable.

At this time, the hydraulic oil sent from the hydraulic pump 22 is accumulated in the accumulator 26 via the center bypass passage 11, the flow passage 14, the check valve 30, the branch passage 15, and the open electromagnetic on-off valve 27. The pressure of the hydraulic fluid in the accumulator 26 at this time is detected by the pressure sensor 25 and the detected value is transmitted to the control section 24 . Then, when the pressure of the hydraulic oil in the accumulator 26 reaches a preset value, the controller 24 sends a signal to the electromagnetic on-off valve 27 to close the accumulator 26 and the branch passage 15 . This electromagnetic on-off valve 27 is closed until it becomes necessary to supply pilot pressure from the accumulator 26 to the pair of solenoids 43 and 44 in the hydraulically piloted electromagnetic proportional spool valve 41 .

Due to the movement of the main spool in the hydraulic pilot type electromagnetic proportional spool valve 41 , it is supplied to the hydraulic cylinder 28 via the supply line 16 , the piston of the hydraulic cylinder 28 rises, the fork 96 rises together with the cargo handling 97 , and the hydraulic pressure to the hydraulic cylinder 28 When the supply of hydraulic oil becomes unnecessary, the driving of the hydraulic pump 22 is stopped by stopping the rotation of the motor 21 with a signal from the control unit 24 . Note that when high-pressure hydraulic oil is required in other areas such as the tilt part 3, the motor 21 continues to drive the hydraulic pump 22 .

On the other hand, the operator operates the lever 23 when the fork 96 is lowered together with the load handling 97 . This operation signal is transmitted to the control unit 24 . At this time, when the rotation of the motor 21 is stopped and the hydraulic pump 22 is not driven, the supply of the pilot pressure by the hydraulic oil from the hydraulic pump 22 is stopped. Therefore, the controller 24 transmits a command signal to the electromagnetic shut-off valve 27 to open the electromagnetic shut-off valve 27 . As a result, the hydraulic oil pressurized to the set value in the accumulator 26 is supplied via the pressure reducing valve 35 to the pilot spool corresponding to the pair of solenoids 43 and 44, and pilot pressure is generated there. As a result, the main spool in the hydraulic pilot type electromagnetic proportional spool valve 41 becomes movable. Then, when the main spool of the hydraulic pilot type electromagnetic proportional spool valve 41 is in the state shown in FIG. At this time, due to the action of the check valve 30 , the working oil in the accumulator 26 is not sent to the center bypass passage 11 .

Therefore, even when the motor 21 stops driving the hydraulic pump 22, the pilot pressure can be supplied to the hydraulic pilot type electromagnetic proportional spool valve 41, and the main spool can be moved. This makes it possible to reduce power consumption of the battery 5 .

Further, when the fork 96 is lowered together with the load handling 97, the control unit 24 closes the electromagnetic on-off valve 27 when the pressure of the hydraulic oil in the accumulator 26 detected by the pressure sensor 25 is lower than a preset value. Then, the control unit 24 restarts the rotation of the motor 21 to drive the hydraulic pump 22 to supply the pilot pressure to the hydraulic pilot type electromagnetic proportional spool valve 41 .

In addition, in the embodiment described above, an electric forklift is used as an electric industrial vehicle. However, electric industrial vehicles are not limited to electric forklifts, and other electric industrial vehicles that raise and lower cargo by driving hydraulic pumps with motors and supplying hydraulic pressure generated by the hydraulic pumps to hydraulic cylinders are used. can do.

As described above, a first aspect of the present invention is a hydraulic circuit in an electric industrial vehicle that drives a hydraulic pump with a motor and supplies hydraulic pressure generated by the hydraulic pump to a hydraulic cylinder to raise and lower cargo. , a hydraulic pilot type electromagnetic proportional spool valve that supplies hydraulic pressure to the hydraulic cylinder by moving the spool in accordance with the operation of the operation part; an accumulator; A branch passage connecting a passage to a pilot pressure supply passage to the accumulator, an on-off valve disposed in the branch passage and opened when cargo is lifted or lowered, and a branch passage and the hydraulic oil supply passage. Allows the flow of hydraulic oil from the hydraulic oil supply passage disposed between and connected to the hydraulic pump to the branch passage, and the hydraulic oil flows from the branch passage to the hydraulic oil supply passage connected to the hydraulic pump and a check valve that shuts off the

With such a configuration, since the hydraulic oil stored in the accumulator can be used to supply the pilot pressure to the hydraulic pilot type electromagnetic proportional spool valve, the amount of electric power used in the electric industrial vehicle can be reduced. becomes possible.

The embodiment according to the first aspect of the present invention includes a pressure sensor that detects the pressure of hydraulic oil in the accumulator, and receives a command signal from the operation unit and a command signal from the pressure sensor, and raises cargo handling. , and when the pressure of the hydraulic oil in the accumulator is lower than the preset set value when lowering the cargo, the hydraulic pump is driven by the motor so that the pressure of the hydraulic oil in the accumulator reaches the preset value when lowering the cargo. A control unit is provided for stopping the drive of the hydraulic pump by the motor when the value is equal to or greater than the minimum value.

With such a configuration, the motor can be rotated by the battery only when the motor needs to be used, and power consumption can be reduced.

In another embodiment according to the first aspect of the present invention, the control unit closes the on-off valve when the pressure of the hydraulic oil in the accumulator becomes a preset value and the lifting operation for cargo handling is not performed.

With such a configuration, it is possible to hold high-pressure hydraulic fluid in the accumulator for supplying pilot pressure to the hydraulically piloted electromagnetic proportional spool valve.

It should be noted that the above-described description of the embodiment of the present invention is for explanation of the embodiment, and does not limit the present invention.

Reference Signs List 1 control unit 2 lift part 3 tilt part 4 tank 5 battery 11 center bypass passage 12 tank passage 13 parallel passage 14 flow path 15 branch passage 16 supply pipe 21 motor 22 hydraulic pump 23 lever 24 controller 25 pressure sensor 26 accumulator 27 electromagnetic On-off valve 28 Hydraulic cylinder 30 Check valve 36 Sequence valve 41 Hydraulic pilot type electromagnetic proportional spool valve 42 Hydraulic pilot type electromagnetic proportional spool valve 43 Solenoid 44 Solenoid 45 Solenoid 46 Solenoid 96 Fork 97 Cargo handling

Claims (1)

A hydraulic circuit in an electric industrial vehicle that raises and lowers cargo by driving a hydraulic pump with a motor and supplying hydraulic pressure generated by the hydraulic pump to a hydraulic cylinder,
a hydraulic pilot type electromagnetic proportional spool valve that supplies hydraulic pressure to the hydraulic cylinder by moving the spool according to the operation of the operation unit;
an accumulator;
a branch path connecting a flow path from a hydraulic oil supply path connected to the hydraulic pump to a pilot pressure supply path to the hydraulic pilot type electromagnetic proportional spool valve and the accumulator;
an on-off valve disposed in the branch passage;
is disposed between the branch passage and the hydraulic oil supply passage, and allows hydraulic oil to flow from the hydraulic oil supply passage connected to the hydraulic pump to the branch passage; a check valve that cuts off the flow of hydraulic fluid to a hydraulic fluid supply line that is connected to the pump;
a pressure sensor that detects the pressure of hydraulic fluid in the accumulator;
a control unit;
When the control unit receives a command signal from the operation unit and raises the cargo handling unit, the control unit drives the hydraulic pump with the motor, so that the hydraulic pilot type electromagnetic proportional spool valve is operated by hydraulic oil from the hydraulic pump. is supplied with pilot pressure, and the hydraulic fluid is accumulated in the accumulator via the branch passage and the open/close valve, and the pressure of the hydraulic fluid in the accumulator reaches a preset value. When the on-off valve is closed,
When receiving a command signal from the operation unit and lowering the cargo handling, when the pressure of the hydraulic oil in the accumulator is equal to or higher than the preset value, the on-off valve is opened, and the hydraulic pressure is controlled by the motor. By stopping the driving of the pump, the hydraulic oil in the accumulator supplies pilot pressure to the hydraulic pilot type electromagnetic proportional spool valve,
When receiving a command signal from the operation unit and lowering the cargo handling, when the pressure of hydraulic oil in the accumulator is smaller than the preset value, the on-off valve is closed, and the hydraulic pressure is controlled by the motor. By driving the pump, the hydraulic oil from the hydraulic pump supplies pilot pressure to the hydraulic pilot type electromagnetic proportional spool valve,
Hydraulic circuits in electric industrial vehicles.

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