JPH02193900A - Hydraulic device in battery type industrial vehicle - Google Patents

Abstract

PURPOSE:To reduce the pressure loss of return oil, and to efficiently carry out the recovery of electric power by means of an electric motor, when a changeover operation means is operated so as to lower a cargo member, by providing an operating oil return passage for returning return oil from a lift cylinder to a hydraulic pump so as to bypass a lift control valve. CONSTITUTION:When a lift lever 5 is lowered in a heavy load condition of a fork, and also when a tilt lever 5 is tilted, a hydraulic pump 1 is turned via an electric motor 27 driven at a rotating speed based on the operational amount of the levers, and operating oil is forcibly fed inside a tilting pipe line 18. Further, the return oil is led inside a return pipe line(operation oil return passage) 11 via a pilot check valve 10 which is in an opened condition based on the heavy load of the fork. In this case, when the rotating speed of the hydraulic pump 1 based on the return oil pressure is greater than the rotating speed command value of the hydraulic pump 1 based on the operational amount of the lever 15, the hydraulic pump 1 functions as a hydraulic motor by the return oil, so that a battery 26 can be charged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic mechanism for power regeneration in a battery-powered industrial vehicle.

[Prior Art] A battery-powered industrial vehicle, such as a battery forklift truck, which is equipped with an electric motor that drives a pump in a hydraulic system for cargo handling, uses a hydraulic pump that functions as a motor using return oil from a lift cylinder to generate electricity for the electric motor. There are some that regenerate the battery by acting as a battery.

As such a regenerative hydraulic system as described above, the applicant of the present application proposed the system shown in FIG. 7 in Japanese Patent Application No. 174405/1983. That is, the limit switch LS detects the operating direction of the lift Leno Nl-40 and the tilt lever 41.
1. The controller C rotates the induction motor 49 based on the signals from the potentiometers Pi and P2 that detect the operation amount of the LSZ and both levers 40 and 41, and the hydraulic pump 42
is driven. Then, based on the operation of the tilt lever 41, the tilt control valve 47 is switched and controlled, the tilt cylinder 48 is expanded and contracted, and the fork is tilted.

Furthermore, hydraulic oil is supplied from the hydraulic pump 42 to the lift cylinder 45 via the lift control valve 44 which is held at the a position based on the lifting operation of the lift lever 40, and the fork is lifted. Further, when the lift control valve 44 is switched to the C position based on the lowering operation of the lift lever 40, the return oil from the lift cylinder 45 is forced to be sent to the return pipe 46 via the control valve 44 due to the load of the fork. The 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 controlled by the limit switch L.
When the SI is detected, the controller C executes the regenerative braking mode based on the detected value of the limit switch LSI.

Then, the return oil is transferred from the return pipe 46 to the hydraulic pump 42.
When the return oil flows into the interior, the hydraulic pump 42 functions as a hydraulic motor using the hydraulic pressure of the return oil to regeneratively drive the electric motor 49. As a result, the electric motor 49 functions as a generator,
The battery 50 is charged.

[Problem to be solved by the invention]

The hydraulic pump 42 is driven by return oil whose hydraulic pressure has increased due to the load of the fork, and functions as a hydraulic motor. Therefore, the higher the pressure of the return oil, the more efficient the electric motor 49 regenerates power.

However, the hydraulic pump 42 is disconnected from the lift cylinder 45.
The return oil flowing into the lift control valve 44 has a large pressure loss due to the resistance it receives when passing through the lift control valve 44, which in turn reduces the regeneration efficiency of the electric motor 1a49.

This invention was made to solve the above-mentioned problems, and its purpose is to reduce the pressure loss of return oil,
An object of the present invention is to provide a hydraulic circuit equipped with a power regeneration function in a battery-powered industrial vehicle that can efficiently regenerate power by an electric motor.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes a switching operation means that is operated to instruct raising and lowering of a cargo handling member;
a lift cylinder that controls the elevation and descent of the cargo handling member by an expansion and contraction operation based on a switching operation of the switching operation means; a lift cylinder that is driven to operate the lift cylinder and supplies hydraulic oil thereto to extend the lift cylinder; , is rotated by the return oil from the contracting lift cylinder,
a hydraulic pump functioning as a hydraulic motor; an electric motor driven by electric power supplied from a battery to rotate the hydraulic pump and regenerating electric power from the battery by the hydraulic pump functioning as a hydraulic motor; and the switching operation means. In a hydraulic system for a battery-powered industrial vehicle, which includes a lift control valve that allows hydraulic oil to pass from a hydraulic pump to a lift cylinder when the cargo handling member is operated to raise it, the switching operation means lowers the cargo handling member. The gist is that a hydraulic oil return path is provided that returns oil from the lift cylinder to the hydraulic pump, bypassing the lift control valve, when the lift cylinder is operated to lift the lift cylinder.

[Function] This invention employs the solution described above, so that when the switching operation means is operated to lower the cargo handling member, the hydraulic oil pumped from the lift cylinder into the hydraulic oil return path is controlled for lift control. It bypasses the valve and returns to the hydraulic pump.

[Embodiment 1] Hereinafter, a first embodiment in which the present invention is embodied in a battery-powered forklift will be described in detail with reference to FIGS. 1 to 6.

In FIG. 1, a hydraulic pump 1 sucks up hydraulic oil stored in an oil tank T through a regeneration check valve 2a disposed in a supply pipe 2, and then pumps it into a fork drive hydraulic circuit H.
It is discharged to the main pipe line 3 inside.

A lift control valve 4 is disposed in the main pipe 3, and the lift control valve 4 corresponds to the raising, neutral, and lowering operating positions of a lift lever 5, which is a switching operation means for instructing the raising and lowering of the fork. It can be switched to three positions: a, b, and c.

Further, the lift control valve 4 is connected to a pressure-reducing pipe 6 that communicates with the oil tank T on its upstream side, and a pressure-up check valve 7 that regulates the flow of hydraulic oil toward the pump 1 on its downstream side. The lift cylinder 9 is connected to a lift pipe 8 via a lift cylinder 9, and the lift pipe 8 communicates with a bottom chamber 9a of a lift cylinder 9. Furthermore, a return pipe 11 as a hydraulic oil return path equipped with a pilot check valve 10 is branched from the downstream of the pressure increase check valve 7 of the lift pipe 8, and a return pipe 11 is branched from the downstream of the pressure increase check valve 7 of the lift pipe 8. It is connected between the regeneration check valves 2a. Then, from the connection point 12 between the pressure increase check valve 7 of the lift pipe 8 and the lift control valve 4, the pilot pipe 1
The pilot check valve 10 is closed by the biloft pressure transmitted through the valve 3, and opened by the release of this pilot pressure.

The lift control valve 4 is held at the third position (FIG. 2) based on the lifting operation position of the lift lever 5, and communicates the main pipe line 3 with the lift pipe line 8 via the pressure increase check valve 7. . The pilot pipe 1 is then connected to the connection point 12, which has become under high pressure due to the hydraulic oil pumped from the pump 1 into the lift pipe 8.
3, the pilot check valve 10 is closed by the pilot pressure transmitted through the hydraulic pump 1 and the bottom chamber 9a of the lift lever 9. Hydraulic oil is supplied to extend the foot cylinder 9, that is, raise the fork.

Furthermore, when the lift lever is operated to the neutral position and switched to the 5th position (Fig. 4), the lift control valve 4 opens the main pipe line 3 to the downstream side, and also connects the lift pipe line 8 from the main pipe line 3. Cut off. The flow of the high-pressure hydraulic oil remaining at the connection point 12 is blocked by the pressure increase check valve 7 and the lift control valve 4, which are blocked by the load of the fork. The pilot check valve 10 is held in a closed state by the pyro pressure applied thereto, and the lift pipe line is cut off from the return pipe line 11. This prevents fluctuations in the flow rate of the hydraulic oil in the lift pipe line 8 and the lift cylinder 9, and maintains it without being contracted.

In addition, when the lift control valve 4 is in the C position (FIGS. 3 and 6) based on the lowering operation of the lift lever 5, the lift control valve 4 is connected to the upstream side of the pressure increase check valve 7 of the lift pipe 8 and to the pressure drop pipe. 6, and the hydraulic oil accumulated near the connection point 12 is led out to the tank T. As a result, the pressure at the connection point 12 is lowered, and the pilot pressure applied to the pilot check valve 10 from the pilot line 13 is released and opened. And lift pipe 8
is communicated with the supply pipe 2 via the return pipe 11, and the return oil that returns from the lift cylinder 9 by the downward load of the fork bypasses the lift control valve 4 with high fluid resistance and returns to the tank T. The flow is cut off by the regeneration check valve 2a, and flows into the hydraulic pump 1 to drive it.

A tilt control valve 14 is disposed in the main pipe 3 on the downstream side of the lift control valve 4, and corresponds to the forward, neutral, and backward tilt operation positions of the tilt lever 15 that instructs the forward and backward tilting operation of the fork. The tilt control valve 14 can be switched to three positions, a, b, and c.

The tilt control valve 14 controls the amount of oil in the front chamber 16a and rear chamber 16b of the tilt cylinder 16 by changing its position to contract the cylinder 16, and has three positions based on the backward tilting position of the tilt lever 15. (Fig. 2.5), the backward tilting pipe 17 is connected to the tilting pipe 18, and the forward tilting pipe 19 is connected to the drain pipe 20, and the hydraulic pump 1 is connected to the front chamber 16a of the tilt cylinder 16. At the same time, the hydraulic oil in the rear chamber 16b is discharged into the oil tank T, and the tilt cylinder 16 is contracted to tilt the fork backward.

The tilt control valve 14 also includes a tilt lever 15.
At position C (Fig. 4) based on the forward tilting operation, the backward tilting conduit 17 is connected to the train conduit 20, the forward tilting conduit 19 is connected to the tilting conduit 18, and the hydraulic pump 1 is connected to the tilting conduit 18. Hydraulic oil is supplied to the rear chamber 16b of the cylinder 16, and hydraulic oil in the front chamber 16a is discharged to the oil tank T, and the tilt cylinder 16 is extended to tilt the fork forward.

Furthermore, the tilt control valve 14 is held at position b (FIG. 3) based on the neutral position of the tilt lever 15, and the forward tilting and backward tilting conduits 19 and 17 are connected to the tilting conduit 1, respectively.
8 and the drain-in pipe 20,
without changing the amount of oil in the tilt cylinder 16.
The fork is held in the tilted state at that time, and the main pipe 3 is communicated with the oil tank T.

Further, when the lift lever 5 is operated to the raised position and the tilt lever 15 is operated to either the forward or backward tilting position (for example, backward tilting), the lift control valve is in the a position as shown in FIG. Lift cylinder 9 and pump 1 through 4
The tilt cinder 16 is connected to the tilt control valve 1 located at either position a or C (position a in the drawing).
4, it is communicated with the pump l and the tank T, and is expanded and contracted. Therefore, the fork performs a tilt operation while ascending.

Further, when the lift lever 5 is operated downward and the tilt lever 15 is operated to either the forward or backward tilting position (for example, forward tilting), the lift control valve 4 in the C position as shown in FIG. The upstream side of the pressure increase check valve 7 and the tank T are communicated through the pressure increase check valve 7, and the pilot check valve 1o is opened when the pressure decreases at the connection point 12. Then, return oil having a pressure according to the load on the fork is pumped from the lift cylinder 9 through the return pipe 11 into the pump l. The tilt cinder 16
is connected to the pump L and tank T via the tilt control valve 14 located at either position a or c (position C in the drawing), so the return oil flowing from the lift cylinder 9 through the pump 1 causes the tilt The cylinder 16 is expanded and contracted.

Therefore, the fork can perform a tilt operation while descending as well as when ascending, making it possible to simultaneously lift and tilt the fork.

Now, the electrical configuration for driving the above-mentioned hydraulic circuit will be explained.

The operating positions of the lift lever 5 such as up, neutral and lowering are detected by a lift operating position sensor 21 consisting of a limit switch, and the operating amount of the lever 5 at the ascending and descending positions is detected by a lift operating amount sensor 22 consisting of a potentiometer. , and each detection signal is input to the controller 23. Further, the forward, neutral, and backward tilting positions of the tilt lever 15 are detected by a tilt operation position sensor 24 consisting of a limit switch, and the amount of operation of the lever 15 at the forward and backward tilting positions is detected by a tilt operation consisting of a potentiometer. It is detected by the amount sensor 25, and each detection signal is input to the controller 23.

The rotational speed of the electric motor 27 driven by electric power supplied from the battery 26 is detected by a rotational speed sensor 28 made of a rotary encoder or the like, and this detection signal is input to the controller 23 .

When the lift lever 5 is lifted in response to a detection signal from the lift operation position sensor 21, the controller 23 controls the electric motor 27 to drive the pump 1 with the electric motor 27. Further, the controller 23 controls the electric motor 27 to drive the pump 1 when the tilt lever 15 is tilted forward or backward based on a detection signal from the tilt operation position sensor 24 .

The controller 23 has an electric motor 27 corresponding to each detected value of the lift operation amount sensor 22 and the tilt operation amount sensor 25.
Calculate the rotation speed of. 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 set based on a predetermined program, and when only the tilt lever 15 is operated, the rotation speed command value for the tilt lever operation amount is set based on a predetermined program. is calculated.

Furthermore, when both levers 5.15 are operated at the same time, the controller 23 calculates the rotation speed command value for each operation amount, and selects the larger rotation speed command value of the two command values as the rotation speed command value of the electric motor 27. It is designed to be. Then, the controller 23 controls the electric power supplied from the battery 26 to the electric motor 27 based on the calculated rotational speed command value, drives the electric motor 27 at a rotational speed according to the rotational speed command value, and controls the discharge amount of the hydraulic pump l. Adjust. That is, the lifting speed and tilting speed of the fork are controlled according to the respective operation amounts of the lift lever 5 and the tilt lever 15.

Further, when the lift lever 5 is lowered due to a heavy load on the fork and the tilt lever 15 is held at the neutral position, the control valve 15 is operated via the opened pilot check valve 10, that is, by bypassing the lift control valve 4. High-pressure return oil flows in the return pipe 11, and no hydraulic oil is introduced into the tilt pipe 18, so that the pressure inside the tilt pipe 18 is low. When the rotational speed of the pump 1 according to the pressure of the return oil is higher than the rotational speed of the electric motor 27 based on the operation amount of the lift lever 5, that is, when the pressure of the return oil is sufficient for the pump 1 to function as a motor, the pump 1 The electric motor 27 is driven as a generator, and the battery 26 is charged via the controller 23.

Conversely, when the tilt lever 15 is held at the neutral position and the lift lever 5 is operated downward to lower the fork under no load or light load, the hydraulic pressure of the return oil sent from the lift cylinder 9 to the pump 1 If the value is low, the hydraulic pump l cannot function as a hydraulic motor, and it is impossible to expect the electric motor 27 to function as a generator.

At this time, if the rotation speed command value of the electric motor 27 based on the operation amount of the lift lever 5 exceeds the actual rotation speed detected by the rotation speed sensor 28, the controller 23 supplies the electric power of the battery 26 to the electric motor 27. to stop. Therefore, even though the fork is lowered by its own load, the electric motor 27 is prevented from rotating based on the operation of the lift lever 5, so power consumption of the battery 26 is avoided and energy is effectively saved. be exposed.

Further, when the fork is under a heavy load and the lift lever 5 is operated to lower and the tilt lever 15 is operated to tilt, the hydraulic pump 1 is rotated via the electric motor 27 driven at a rotational speed based on the lever operation amount, and the tilt pipe is rotated. While hydraulic oil is pumped into the line 18, return oil due to the heavy load of the fork is introduced into the return line 11 via the pilot check valve 10 which is in an open state. In this case, when the rotational speed of the pump 1 based on the pressure of the return oil is greater than the rotational speed command value of the electric motor 27, that is, the pump 1, based on the operation amount of the tilt lever 15, the return oil causes the hydraulic pump 1 to As a hydraulic motor, electric motor 27 functions as a generator to charge battery 26 .

The return oil is then pumped from the pump 1 into the tilt cylinder 16. Therefore, when the fork is lowered under a heavy load, the return oil from the lift cylinder 9 is used to charge the battery 26 and then used for the tilt operation of the fork, so that the hydraulic oil is effectively utilized.

Also, when the fork is under a light load, the lift lever 5
is operated downward and the tilt lever 15 is operated to tilt forward or backward, and when the amount of operation of the lift lever 5 exceeds the amount of operation of the tilt lever 15, the electric motor 27 (pump l) It is driven by the rotational speed command value that is revealed.

Even if the rotational speed command value based on the operation amount of the lift lever 5 exceeds the rotational speed of the pump l due to low-pressure return oil, the controller 23 cuts off the power to the battery 26 from the electric motor 27 according to a predetermined program. The electric motor 27 is driven without any movement. Therefore, even when the fork descends under a low load, a stable tilt operation is ensured and is performed without reducing the descending speed.

As described above, in this embodiment, when the return oil from the lift cylinder 9 drives the pump 1 to regenerate the electric motor 27, the return oil return pipe 11 is routed around the lift control valve 4. By arranging the piping, the return oil will not be subject to large resistance within the pipe and the oil pressure value will not be lowered. Therefore, the pump 1 can be driven by the returned oil, that is, the electric power can be regenerated from the electric motor 27 effectively.

Note that this invention is not limited to the above-described embodiments, and any changes may be made without departing from the spirit of the invention, such as using a DC motor instead of the induction motor 27, for example.

[Effects] As detailed above, according to the present invention, the excellent effect of reducing the pressure loss of return oil and allowing the electric motor to efficiently regenerate electric power is exhibited.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the hydraulic and electrical configuration of the present invention, FIG. 2 is a circuit diagram showing the hydraulic and electrical configuration when the fork is raised, and FIG. 3 is a circuit diagram showing the hydraulic and electrical configuration when the fork is lowered. Electrical circuit diagram, Figure 4 is a circuit diagram showing the hydraulic and electrical configuration when the fork is tilted forward, Figure 5 is a circuit diagram showing the hydraulic and electrical configuration when the fork is tilted backward, Figure 6 7 is a circuit diagram showing the hydraulic and electrical configuration when the fork is lowered and tilted forward, and FIG. 7 is a circuit diagram showing the hydraulic and electrical configuration of a conventional example.

Claims (1)

[Scope of Claims] 1. A switching operation means that is switched to instruct the lifting and lowering of the cargo handling member; a lift cylinder that controls the lifting and lowering of the cargo handling member by an expansion and contraction operation based on the switching operation of the switching operating means; Driven to operate the lift cylinder, supplying hydraulic oil to extend the lift cylinder, and rotated by return oil from the contracting lift cylinder;
A hydraulic pump that functions as a hydraulic motor; an electric motor that is driven by electric power supplied from a battery to rotate the hydraulic pump and regenerate electric power from the battery by the hydraulic pump that functions as a hydraulic motor; and the switching operation means for cargo handling. In a hydraulic system for a battery-powered industrial vehicle, the hydraulic system includes a lift control valve that allows hydraulic oil to pass from a hydraulic pump to a lift cylinder when operated to raise a member, wherein the switching operation means lowers the cargo handling member. A hydraulic system for a battery-powered industrial vehicle, which is provided with a hydraulic oil return path that returns oil from a lift cylinder to a hydraulic pump, bypassing a lift control valve, when the lift cylinder is operated as intended.