JPH0228498A - Hydraulic device of battery type industrial vehicle - Google Patents

Abstract

PURPOSE:To improve the working efficiency by installing a hydraulic circuit equipped with an electric power regeneration function onto a battery type industrial vehicle such as battery fork lift and simultaneously carrying out the lowering operation and the tilt operation for a fork. CONSTITUTION:The titled hydraulic device is equipped with an electromagnetic type selector valve 32 as feedback passage selecting means and a controller 21 for controlling an electric motor 22 for the normal revolution of a hydraulic pump 23 in the selecting operation of the selector valve 32. Therefore, when a lift cylinder 9 is contraction-operated to lower and tilt a fork, and a tilt cylinder 11 is operated for the extension or contraction, the selector valve 32 cuts off a feedback passage for the working oil supplied from the lift cylinder 9 to the hydraulic pump 23, and the feedback passage is allowed to directly communicate to a drain side. The electric motor 22 driven by the controller 21 drives the hydraulic pump 23 in the normal direction, and the pressurized oil discharged from the hydraulic pump 23 is transmitted to the tilt cylinder 11.

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] In a battery-powered industrial vehicle, such as a pufferby forklift, an oil pump is driven in the normal direction by the forward rotation of the electric motor, and the pressurized oil discharged from the oil pump is supplied to the lift cylinder and the tilt cylinder to drive the fork. Raising and tilting takes place. In some forklifts, when the fork is lowered, the pressurized oil discharged from the lift cylinder is returned to the oil pump, and the pump is reversed to drive the electric motor in reverse, and the electric motor is used as a generator, thereby draining the battery. There is one that allows you to charge the battery.

An example of a battery forklift truck having a hydraulic circuit equipped with the power regeneration function is disclosed in Japanese Patent Publication No. 62-15478. The hydraulic circuit of this forklift is
As shown in FIG. 8, a tilt cylinder 45 is connected to a main circuit 43 extending from an oil pump 42 driven by an electric motor 41 through a tilt control valve 44, and a lift cylinder 47 is connected through a lift control valve 46. each connected.

The lift control valve 46 and the lift cylinder 47
A pressure switch 49 is installed in the lift circuit 48 which detects the pressure inside the pipe and is turned off. It is provided near the proximal end of the. When the pressure in the pipe of the lift circuit 48 falls below a predetermined value, the lift lever 50 is activated to lower the fork.
, that is, only when there are signals from both switches 49 and 51, the electromagnetic switching valve 53 of the bypass circuit 52 branched from the main circuit 43 is energized and opened.

When the lift lever 50 is operated to raise the fork, the control valve 46 is switched to the raising side, and the lift circuit 48
The lift cylinder 47 is extended by the pressure oil sent through the fork, and the fork is raised.

Then, in order to lower the fork, the lift control valve 46 is activated as shown in FIG. 9 by operating the lift lever 50.
When switched to the lowering side, pressure oil in the lift cylinder 47 flows from the lift circuit 48 through the control valve 46 into the main circuit 43.

When the load of the descending fork is sufficient, that is, when the hydraulic pressure of the pressure oil discharged from the lift cylinder 47 exceeds a predetermined amount, the pressure switch 49 is not driven either. Therefore, the switching valve 53 only receives the signal from the limit switch 51, and the switching valve 53 is kept closed. Therefore, the pressure oil discharged from the lift cylinder 47 is returned to the tank 54 via the pump 42, and the oil pump 42, which is rotated in reverse by this returned oil, functions as a hydraulic motor. Therefore, the electric motor 41 functions as a generator and can charge the battery.

When the fork is lowered with a light load such as its own weight, the switching valve 53 is activated by signals from both switches 49 and 51.
will be released. As a result, the return oil from the lift cylinder 47 avoids the pump 42, which has a large passage resistance, passes through the bypass circuit 52, and flows into the tank 54. This prevents the lowering speed of the fork from decreasing, and also reduces the charging effect. Power regeneration is avoided.

Furthermore, when the tilt lever 55 is operated while the lift cylinder 47 is being lowered, the main circuit 43 is shut off by the tilt control valve 44 as shown in FIG. 10, and the return oil from the lift cylinder 47 to the pump 42 is The passage is cut off.

Therefore, the line pressure in the lift circuit 48 increases, the pressure switch 49 is switched, and the bypass circuit 52 is switched to the switching valve 5.
3, the circuit is closed. Furthermore, the tilt lever 55
The operation of is detected by the limit switch 56.

Then, the battery energizes the electric motor 41 in response to a signal from the limit switch 56, and as the electric motor 41 rotates in the normal direction, the pump 42 is driven in the normal rotation.

[Problems to be Solved by the Invention] Therefore, when a tilt operation is performed when the fork is lowered, the lift cylinder 47 is cut off from the pump 42 to stop the lowering of the fork, and then the tilt cylinder 47 is connected to the pump 42. The tilting operation of the fork is performed by the pressure oil forced into the fork.

Therefore, as described above, the lowering operation and the tilting operation of the fork cannot be performed at the same time, and the lowering operation is stopped and only the tilting operation is performed, resulting in a decrease in work efficiency.

This invention was made to solve the above-mentioned problems, and its purpose is to provide power regeneration in a battery-powered industrial vehicle that can perform both the lowering operation and the tilting operation of the fork to ensure high work efficiency. The objective is to provide a hydraulic circuit with functions.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes a lift cylinder that controls the elevation of a cargo handling member, a tilt cylinder that also controls the tilting of the cargo handling member, and a lift cylinder and a tilt cylinder that control the tilting of the cargo handling member. It is interposed in a pipe connecting the cylinder and drain side and rotates in both forward and reverse directions, and during forward rotation, pressure oil is discharged from the drain side to at least one cylinder, and pressure oil is returned from the lift cylinder to the drain side. The hydraulic pump is rotated in reverse order to function as a hydraulic motor, and the hydraulic pump is driven by electric power supplied from a battery to rotate the hydraulic pump, and when the hydraulic pump functions as a hydraulic motor, the hydraulic pump is rotated to regenerate power from the battery. In a hydraulic system for a battery-powered industrial vehicle comprising an electric motor that performs a return path switching means for blocking the return path of the drain and connecting the return path directly to the drain side; and a drive control means for driving and controlling the electric motor to rotate the hydraulic pump in the forward direction when the return path switching means is switched. The gist is that it has been established.

[Function] This invention employs the solution described above, so that when the lift cylinder is retracted to lower and tilt the cargo handling member, and the tilt cylinder is expanded or retracted, the return path switching means is activated. The return path of hydraulic oil from the lift cylinder to the hydraulic pump is shut off, and the return path is communicated directly to the drain side. Then, the electric motor driven by the drive control means drives the hydraulic pump to rotate normally, and the pressure oil discharged by the hydraulic pump reaches the tilt cylinder.

[Example 7] Hereinafter, a first example of the present invention will be described in detail with reference to FIGS. 1 to 7.

In Figures 1 and 2, battery-powered forklift vehicle 1
A pair of left and right outer masts 2 are erected at the front of the machine, and an inner mast 3 is disposed inside each outer mast 2. A chain 4 is disposed on the inner surface of both inner masts 3 so as to be able to go around each other, and the attachment suspended from one end of each chain 4 is attached to a pair of upper and lower suspension members 6 mounted between the plates 5 as cargo handling members. Fork 7 is attached. Furthermore, both inner masts 3 are connected at the upper part by a hanging member 8, and rods 10 of a pair of lift cylinders 9 are arranged corresponding to these inner masts 3.
The upper end of is fixed to the hanging member 8.

Further, a pair of tilt cylinders 11 extending obliquely upward are provided on the front frame of the vehicle 1, and these rods 12
The upper ends of the outer masts 2 are respectively connected to the vertical center portions of the corresponding outer masts 2.

A steering wheel 14 is provided at the front inside the driver's cab 13 of the vehicle 1.
, a lift lever 15 and a tilt lever 16 are provided, and furthermore, a battery case 18 for storing a battery 17 and a battery hood 19 for closing the battery case 18 are provided at the rear so as to be rotatable together with the driver's seat 20.

The lift lever 15 is used to raise and lower the fork 7,
It can be switched to three positions: up, neutral, and down. When the lift lever 15 is switched to the raised position, the rod 10 of the lift cylinder 9 protrudes upward as shown by the two-dot chain line in FIG.
is raised, and the fork 7 is moved upward by the rotation of the chain 4 accompanying this movement. After this, lift lever 1
By switching the fork 5 to the neutral position, the fork 7 is held upward. Further, when the lift lever 15 is switched to the lowered position, the inner mast 3 is lowered and the fork 7 held above is lowered.

Furthermore, the tilt lever 16 has three types: forward tilt, neutral and backward tilt.
It is possible to switch the position. When the tilt lever 16 is operated to tilt forward, the tilt cylinder 11
is driven, and the outer mast 2 is driven by the protrusion of the rod 10.
and the inner mast 3 tilts forward around the lower end,
The fork 7 is tilted forward. This forward inclination of the fork 7 is maintained by keeping the tilt lever 16 neutral,
Furthermore, both masts 2 are switched to the backward tilted position.
．． 3 is tilted in the opposite direction, and the fork 7 is returned to the horizontal state.

Next, regarding the electrical and hydraulic configuration of this example,
This will be explained according to FIGS. 3 to 6.

The battery 17 has a controller 2 as a drive control means.
1 is connected, and the electric motor 22 is driven by the controller 21. A hydraulic pump 23 is mechanically connected to the electric motor 22, and the hydraulic pump 23 is rotated in the forward direction by the electric motor 22, and the hydraulic oil stored in the oil tank 24 on the drain side is pumped into the main circuit 25. .

Note that when the fork 7 is lowered, the hydraulic pump 2
3 is rotated in the opposite direction by the hydraulic oil flowing in from the main circuit 25, that is, the return oil, and functions as a motor, which reverses the electric motor 22 and causes it to generate electricity, so that the battery 17 is charged. There is.

A lift control valve 26 is disposed in the main conduit 25, and the lift control valve 26 is further connected to a piston chamber 27 of the lift cylinder 9. The lift control valve 26 is provided so as to be switchable to three positions A, B, and C in response to the raising, neutral, and lowering operations of the lift lever 15, and is connected to a pipe line between the hydraulic pump 23 and the lift cylinder 9. Controls the flow of hydraulic oil within.

Further, a tilt control valve 28 is provided in the main pipe 25 on the downstream side of the lift control valve 26, and is connected to the front and rear chambers of the tilt cylinder 11. Like the lift control valve 26, this tilt control valve 28 can be switched to three positions A, B, and C, and when the tilt lever 16 is tilted forward, neutral, or backward, the hydraulic pump 23 and the tilt The passage of hydraulic oil in the pipe line between the cylinders 11 is appropriately controlled.

When the lift lever 15 is operated to the upward or downward side, this is detected by the limit switch LSI, and a signal based on this detection operation is output from the limit switch LSI to the controller 21. Also, lift lever 15
The amount of operation is detected by a lift lever operation amount sensor 29 consisting of a potentiometer, and a signal based on this detected value is output to the controller 21. When the lift lever 15 is operated to the upward side, the limit switch LS
In accordance with the signal from I, the controller 21 maintains the electric motor 22 in the normal rotation power running mode, and further, the controller 21 drives the electric motor 22 at the rotation speed based on the signal from the sensor 29 to rotate the hydraulic pump in the normal direction, and the hydraulic pump 23 discharges hydraulic oil in an amount based on the rotational speed of the electric motor 22 through a main pipe 25 to a lift control valve 26 located at the human position.

Further, when the lift lever 15 is operated to the lowered position, the controller 21 converts the electric motor 22 to the power regeneration mode according to a signal from the limit switch LSI. At the same time, by lowering the lift lever 15, the lift control valve 26 is held at the C position shown in FIG. Valve 32 and lift lowering check valve 33
It is returned to the pump 23 through the. For this reason, the pump 23
is reversed and functions as a motor, and the electric motor 22 is reversed to charge the battery 17.

Further, the oil pressure in the piston chamber 27 of the lift cylinder 9 is detected by a pressure sensor 31, and when this detected value falls below a preset light load reference value, a signal is output from the pressure sensor 31 to the controller 21. For example, when the lift lever 15 is lowered with the fork 7 empty and a signal from the pressure sensor 31 is output to the controller 21, the controller 21 outputs the signal from the lift lever operation amount sensor 29 to power regeneration mode. The mode of the electric motor 22 is set to reverse power running mode by invalidating the signal instructing the conversion,
Reverse the electric motor 22. As a result, when the fork 7 is lowered under a light load, the return oil with a low hydraulic pressure flowing from the lift cylinder 9 into the pump 23 via the lift control valve 26 is transferred to the pump 23 which is reversed by the electric motor 22. The oil is quickly discharged into the oil tank 24. Therefore, despite the light load, the lift cylinder 9 contracts, that is, the fork 7
The decline will not occur slowly. Furthermore, although the pump 23 is reversed, the electric motor 22 is forcibly maintained in the power mode, so that wasteful power regeneration with low charging effect due to low oil pressure return oil can be avoided.

Further, when the tilt lever 16 is operated from the neutral position to the forward or backward tilting position, the limit switch LS
Detected at 2. Then, a signal based on this detection operation is outputted from the limit switch LS2 to the controller 21 and the switching valve 32, and the controller 21 maintains the electric motor 22 in the running mode in accordance with this signal. Further, as the tilt lever 16 is tilted back and forth, the tilt control well 28 is switched to the A position or the C position as shown in FIGS. 5 and 6, respectively, and the front and rear chambers of the tilt cylinder 11 are pumped. It is connected to 23.

Then, the controller 21 drives the electric motor 22 at a rotation speed based on the operation amount of the tilt lever 16 detected by the tilt lever operation amount sensor 34 consisting of a potentiometer.
Hydraulic oil supplied to the tilt cylinder 11 through the fork 7 expands and contracts, causing the fork 7 to tilt forward or backward.

Furthermore, when the limit switch LS2 detects that the tilt lever 16 has been operated, the limit switch LS2
outputs a signal to the switching valve 32 to switch it from the open position shown in Figures 3 and 4 to the bypass position shown in Figure 5.6. Therefore, if the tilt lever 16 for tilting the fork 7 is tilted back and forth while the fork 7 is lowering, communication between the lift control valve 26 and the pump 23 is cut off, and the lift cylinder 9 is The returned oil is directly returned to the oil tank 24 via the bypass circuit 36. Therefore, charging of the battery 17 is stopped, the fork 7 is lowered, and the electric motor 22, which has been converted to the forward mode by the operation of the limit switch LS2, drives the pump 23 to supply hydraulic oil to the tilt cylinder 11. This allows the fork 7 to be tilted while being lowered.

In the above embodiment, when the lift lever 15 is lowered, the fork 7 is lowered and the battery 17 is lowered.
When the fork 7 is lowered under a light load, charging of the battery 17 is stopped and the pump 23 is forcibly rotated in the opposite direction to detect that the hydraulic pressure of the return oil is low. compensation, prompting a rapid downward movement.

Further, if the tilt lever 16 is operated to tilt forward or backward while the fork 7 is lowering, charging of the battery 17 is stopped, and the lowering and tilting operation of the fork 7 are performed simultaneously, so that high working efficiency can be guaranteed.

Next, a second embodiment of the present invention will be described with reference to FIG. 7. This embodiment employs a pilot pressure type switching valve 37 instead of the electromagnetic type switching valve 32 in the first embodiment as the return path switching means. An electromagnetic switching valve 39 is interposed in a pilot circuit 38 that connects the pilot operating portion of the switching valve 37 and the downstream side of the tilt check valve 35. Then, the switching valve 39, which is normally in the closed position, is opened by a signal from the limit switch LS2 based on the forward/backward tilting movement of the tilt lever 16, and pilot pressure is applied to the switching valve 37 via the pilot circuit 38. Switching from the open position to the bypass position, the return oil from the lift cylinder 9 is returned directly to the oil tank 24, and the
The structure is such that power regeneration of the fork 7 is stopped and the tilting operation and lowering operation of the fork 7 are performed simultaneously.

With the above configuration, the switching valve 39 that introduces the pilot pressure is equipped with a function of circulating a small flow of hydraulic oil, and the switching valve 37 is of the pilot pressure type, thereby reducing manufacturing costs. is reduced.

Note that this invention is not limited to the embodiments described above, and for example, a battery-powered industrial vehicle equipped with a hydraulic loading mechanism such as a shovel loader may be used in place of the battery forklift, and other modifications may be made based on the spirit of the invention. Any changes are of course possible as long as they do not deviate from the above.

Furthermore, although the switching valve 32 in the first embodiment and the switching valve 39 in the second embodiment are operated by a signal from the limit switch LS2, they may be controlled by a signal from the controller 21.

Furthermore, it is also possible to use a DC shunt motor or an induction motor as the motor.

[Effects] As described in detail above, the regeneration hydraulic circuit of the present invention exhibits the excellent effect of ensuring high work efficiency by performing both the lowering and tilting operations of the fork.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a forklift according to a first embodiment of the present invention, FIG. 2 is a perspective view showing its fork lifting and tilting mechanism, and FIG. 3 is a circuit diagram showing its hydraulic and electrical configuration. Figure 4 is a circuit diagram showing the hydraulic and electrical configuration when the fork is lowered, Figure 5 is a circuit diagram showing the hydraulic and electrical configuration when the fork is lowered and tilted forward, and Figure 6 is a circuit diagram showing the hydraulic and electrical configuration when the fork is lowered and tilted forward. A circuit diagram showing the hydraulic and electrical configuration when descending and tilting backward; FIG. 7 is a circuit diagram showing the hydraulic and electrical configuration of the second embodiment of the present invention; FIG. 8 is a conventional example. 9 and the same hydraulic circuit diagram showing the valve switching state when the fork is lowered in the conventional example, and FIG. 10 similarly shows the valve switching state when the fork is lowered and tilted forward in the conventional example. It is a hydraulic circuit diagram.

Claims (1)

[Scope of Claims] 1. A lift cylinder that controls the elevation of the cargo handling member; a tilt cylinder that also controls the tilting of the cargo handling member; A hydraulic pump that rotates in both reverse directions and discharges pressure oil from the drain side to at least one cylinder during forward rotation, and is reversed by the pressure oil returned from the lift cylinder to the drain side and functions as a hydraulic motor. A hydraulic system for a battery-powered industrial vehicle, comprising an electric motor driven by electric power supplied from a battery, which rotates the hydraulic pump, and which is rotated when the hydraulic pump functions as a hydraulic motor to regenerate electric power from the battery. In this case, when the lift cylinder is retracted and the tilt cylinder is expanded or retracted, the switch is operated to cut off a return path of hydraulic fluid from the lift cylinder to the hydraulic pump, and to connect the return path to the drain side. A hydraulic system for a battery-powered industrial vehicle, comprising: a return path switching means that directly communicates with the return path switching means; and a drive control means that drives and controls an electric motor to rotate a hydraulic pump in the normal direction when the return path switching means is switched.