JPH02188398A - Hydraulic device of battery used industrial vehicle - Google Patents

Abstract

PURPOSE:To correctly lower a loading member according to the instructed speed by installing a means for properly correcting the revolution speed of an electric motor which a revolution speed calculating means calculates, in order to absorb the increase of the revolution speed of a hydraulic pump due to the returned oil on the basis of the result of the detection of a load detecting means for detecting the value of the load of the loading member. CONSTITUTION:A load detecting means 6 detects the load value of a loading member F. On the basis of the result of the detection. a revolution speed correcting means 20 properly corrects the standard revolution speed which a revolution speed calculating means calculates, in order to absorb the increase of the revolution speed of a hydraulic pump 1 due to the returned oil. Therefore, the loading member F is correctly lowered according to the instructed speed, and the fine loading operation can be carried out.

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 equipped with a hydraulic system for cargo handling, such as a battery forklift, the fork is raised and lowered according to the operating direction of a lift lever, and the raising and lowering speed is determined based on the operating amount in each operating direction. .

The applicant of the present application has filed a patent application in 1983 for the above-mentioned hydraulic system.
-174405 proposes what is shown in FIG. That is, the lift lever 40 and the tilt lever 41
Rimint switch LSI, LS2 that detected the operating direction of
Based on signals from potentiometers P1 and P2 which detect the amount of operation of both levers 40 and 41, controller C rotates hydraulic pump 42 via induction motor 49, and hydraulic oil is sucked up from the oil tank. Then, the tilt control valve 47 is switched and controlled based on the operation of the tilt lever 41, and hydraulic oil is supplied to the tilt cylinder 48, which is expanded and contracted, thereby performing a tilting operation of the fork.

Further, when the lift lever 40 is operated to rise, the controller C drives and controls the electric motor 49 to rotate the hydraulic pump 42 at a rotation speed based on this operation amount. Then, the hydraulic pump 42 supplies hydraulic oil at a flow rate corresponding to the rotation speed of 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 4o, and the speed according to this flow rate. The fork is raised.

Further, when the lift lever 40 is operated to lower, the controller C drives and controls the electric motor 49 at a rotation speed based on this operation amount, thereby rotationally driving the pump 42 and lowering the fork.

[Problems to be Solved by the Invention] During the cargo handling operation of the forklift, the fork is moved up and down extremely frequently. However, the descending speed of the fork is greatly influenced by the amount of lift lever operation as well as the weight of the fork at the time, that is, the load, and the fork's descending speed cannot accurately follow the amount of lift lever operation. , cargo handling operations become rough.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a hydraulic circuit for a battery-powered industrial vehicle in which a cargo handling member can be lowered accurately according to a commanded speed to enable detailed cargo handling operations.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes a cargo handling member that is lifted and lowered to carry out cargo handling work, and a cargo handling member that is raised and lowered by an extension operation. A lift cylinder contracts due to the load when the cargo handling member is lowered, and is rotated to operate the lift cylinder, supplies hydraulic oil to the lift cylinder to extend it, and further expands the cargo handling member when the cylinder contracts. A hydraulic pump whose rotational speed is increased according to the pressure value of return oil from a cylinder based on the load, an electric motor driven by electric power supplied from a battery to rotate the hydraulic pump, and when the cargo handling member is lifted or lowered. a speed instruction means for instructing a change in the vertical speed of the cargo handling member in response to the operation amount; an operation amount detection means for detecting the operation amount of the speed instruction means; and a detection result of the operation amount detection means. In a hydraulic system for a battery-powered industrial vehicle, the hydraulic system includes a rotation speed calculation means for calculating the rotation speed of the electric motor based on the calculation result of the calculation means, and a drive control means for driving and controlling the electric motor based on the calculation result of the calculation means. Load detection means detects the value, and the rotation speed of the motor calculated by the rotation speed calculation means is calculated based on the detection result of the load detection means, in order to absorb the increase in rotation speed of the hydraulic pump due to return oil. The gist thereof is that a rotational speed correction means is provided to correct the rotational speed as appropriate.

[Function] By adopting the above solution, the load detection means detects the value of the load on the cargo handling member, and based on this detection result, absorbs the increase in the rotational speed of the hydraulic pump due to the return oil. Therefore, the rotational speed correction means appropriately corrects the reference rotational speed calculated by the rotational speed calculation means.

[Embodiment] 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 7.

In FIG. 1, a hydraulic pump l sucks up hydraulic oil stored in an oil tank T through a regeneration check valve 2a in a supply pipe line 2, and then pumps hydraulic oil for driving a fork F as a cargo handling member. It is discharged into the main pipe line 3 in the circuit H. A lift control valve 4 as a switching control valve is disposed in the main pipe 3, and the lift control valve 4 serves as a speed instruction means for instructing the raising and lowering of the fork F to raise, neutralize, and lower the lift lever 5. It can be switched to three positions, a, b, and c, depending on the position. Although the fork F is shown in FIG. 1, it is omitted from FIGS. 2 onwards in order to simplify and clarify the illustration of the piping state in the hydraulic circuit.

The lift control valve 4 controls the amount of hydraulic oil in the bottom chamber 7a of the lift cylinder 7 by changing its position to extend and retract the cylinder 7, and has three positions (the third position) based on the upward operation position of the lift lever 5. 2), the main pipe line 3 and the lift pipe line 6 are communicated, and the hydraulic pump l supplies hydraulic oil to the bottom chamber 7a of the lift lever 7, thereby extending the lift cylinder 7 and moving the fork F. raise.

In addition, the lift control valve 4 connects the lift pipe 6 and the return pipe 8 at the 0 position M (Fig. 3.6) based on the lowering operation position of the lift lever 5, and At a load of F, return oil is returned from the lift cylinder 7 between the regeneration check valve 2a of the supply pipe 2 and the hydraulic pump 1. In the supply pipe line 2, a regeneration check valve 2a is provided.
The return oil whose flow to the tank T is cut off at , flows into the hydraulic pump 1 and drives it.

Furthermore, at position 5 (FIG. 4) based on the neutral position of the lift lever 5, the lift control valve 4 blocks the lift pipe 6 from the main pipe 3 and the return pipe 8, and prevents the operation in the lift cylinder 7. To maintain the height of a fork F at that time without causing oil contraction by preventing fluctuations in the oil flow rate, and to open a main pipe line 3 to the downstream side.

A tilt control valve 9 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 10 that instructs the fork F to tilt forward and backward. The tilt control valve 9 is set to 3, a, b, and c.
It is designed to be driven to change the position.

The tilt control valve 9 controls the amount of oil in the front chamber 14a and rear chamber 14b of the tilt cylinder 14 by changing its position, thereby causing the cylinder 14 to contract.

That is, the tilt control valve 9 opens the rearward tilting conduit 1 at three positions (FIGS. 2 and 5) based on the rearward tilting position of the tilt lever 10.
2 is connected to the tilt conduit 11, and the forward tilt conduit 13 is connected to the drain conduit 15. As a result, the hydraulic oil is supplied from the hydraulic pump 1 to the front chamber 14a of the tilt cylinder 14, and the hydraulic oil in the rear chamber 14b is caused to flow out to the oil tank T, and the tilt cylinder 14 is contracted. Do a tilt.

Further, the tilt control valve 9 is in the 0 position (FIG. 4) based on the forward tilt operation of the tilt lever 10.
2 is connected to the drain pipe 15, and the forward tilt pipe 13 is connected to the tilt pipe 11, so that the hydraulic oil is supplied from the hydraulic pump 1 to the rear chamber 14b of the tilt cylinder 14, and the pressure inside the front chamber 14a is communicated. The hydraulic oil is discharged into the oil tank T, and the tilt cylinder 14 is extended to move the fork F to about 1 point forward.

Further, based on the neutral position of the tilt lever 10, the tilt control valve 9 is held at the 5 position (FIG. 3), and the forward and backward tilting conduits 13 and 12 are connected to the tilting conduit 11 and the drain-in conduit. The fork F is held in the tilted state at that time without changing the amount of oil in the tilt cylinder 14, and the main pipe 3
is connected to the oil tank T.

Further, when the lift lever 5 is operated to the raised position and the tilt lever 10 is operated to either the forward or backward tilting position (for example, backward tilting), the lift control valve is located at the 3rd position as shown in FIG. Lift cylinder 7 and pump 1 through 4
The tilt tank 14 is connected to a tilt control valve 9 located at either position a or C (position a in the drawing).
It is connected to the pump 1 and the tank T via the pump 1 and is expanded and contracted.

Therefore, the fork F performs a tilt operation while rising.

Further, when the lift lever 5 is operated downward and the tilt lever 10 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. via lift cylinder 7 and pump l
The return oil flowing from the lift cylinder 7 due to the load of the fork F flows into the pump 1. The tilt cylinder 14 is located at either position a or C (
By communicating with the pump 1 and the tank T through the tilt control valve 9 located at position C in the drawing, the tilt cylinder 14 is expanded and contracted by return oil flowing from the lift cylinder 7 through the pump l.

Therefore, the fork F performs a tilting operation while descending in the same way as when ascending, and the fork F can be simultaneously lifted and tilted.

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

The oil pressure value in the lift pipe 6 is detected by an oil pressure sensor 6a as a load detection means attached thereto, and a detection signal based on this is sent to a controller as a rotational speed calculation means, a drive control means, and a rotational speed correction means. 20 is input.

The operating positions of the lift lever 5, such as up, neutral, and down, are detected by a lift operating position sensor 16 made up of a limit switch, and the operating amounts at the up and down positions of the lift lever 5 are detected by potentiometers. Lift operation amount sensor 1 as a detection means
7, and the detection signal is input to the controller 20.

Further, the forward, neutral and backward tilted positions of the tilt lever 10 are detected by a tilt operation position sensor 18 consisting of a limit switch, and the tilt lever lO
The amount of operation at the forward tilted position and the backward tilted position is detected by a tilt operation amount sensor 19 consisting of a potentiometer,
Each detection signal is input to the controller 20.

The controller 20 controls the drive power of the battery 24 to supply power to the induction motor 21. The rotation speed of this electric motor 21 is detected by a rotation speed sensor 23 consisting of a rotary encoder, and this detection signal is sent to the controller 2.
It is input to 0.

When the lift lever 5 is lifted in response to a detection signal from the lift operation position sensor 16, the controller 20 controls the electric motor 21 to drive the pump l. The controller 20 also controls the tilt lever 10 based on the detection signal from the tilt operation position sensor 18.
When the pump 1 is tilted forward or backward, the electric motor 21 is driven and controlled to drive the pump 1.

The controller 20 has an electric motor 21 corresponding to each detected value of the lift operation amount sensor 17 and the tilt operation amount sensor 19.
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 predetermined, and when only the tilt lever 10 is operated, the rotation speed command value for the tilt lever operation amount is predetermined. Calculations are performed based on the programmed program.

Further, when the tilt lever 10 is tilted forward or backward during the downward operation of the lift lever 5, the controller 20 sets the rotation speed command value as the rotation speed command value of the electric motor 21 based on the lift lever operation amount. Furthermore, when the tilt lever 10 is operated to tilt forward or backward during the upward operation of the lift lever 5, the controller 20 compares the rotational speed command values based on the operating amounts of both levers, and selects the larger rotational speed command value for the electric motor 21. The controller 20 controls the electric power supplied from the battery 24 to the electric motor 21 based on the calculated speed command value, and controls the electric motor 21 at a speed according to the rotation speed command value. is rotated to adjust the discharge amount of the hydraulic pump 1. 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 10.

Furthermore, when the lift lever 5 is lowered, the controller 20 controls the return oil pressure from the lift cylinder 7 based on the detection signal from the oil pressure sensor 6a, regardless of whether the tilt lever 10 is in the neutral position or the forward/backward tilt operation position. Calculate. Then, in order to prevent the rotational speed of the pump 1 from exceeding the value instructed by the operation amount of the lift lever 5 with this return oil pressure, a rotational speed correction value for correcting the rotational speed command value is calculated.

That is, as shown in FIG. 7, when the calculated return oil pressure is zero, the correction value is set to zero, and the correction value is increased in proportion to the increase in the return oil pressure. Then, the correction value is subtracted from the rotational speed command value, and the rotational speed command value is gradually decreased in inverse proportion to the increase in the return hydraulic pressure, and when the maximum return hydraulic pressure corresponding to the maximum allowable load of the fork F is reached, the maximum value is corrected. The rotational speed command value is changed so that the value of the rotational speed command value is minimized. Therefore, the increase in the rotational speed of the pump 1 based on the return oil pressure is absorbed by the decrease in the rotational speed command value of the electric motor 21, which is inversely proportional to this increase, and the rotational speed of the pump 1 is maintained so as to correspond to the operation amount of the lift lever 5. ing.

Now, the operation of the hydraulic system configured as described above will be explained below.

As shown in FIG. 3, when the lift lever 5 is operated to lower the lift lever 5 alone, the controller 20 sends the pump l
drive the rotation. When the fork F is under a light load,
The pressure of the return oil flowing out from the lift cylinder 7 into the lift pipe 6 is also small, and the force that tries to rotate the pump 1 is not large. At this time, the controller 20 corrects the command value by subtracting a small correction value from the rotation speed command value corresponding to the lever operation amount based on the detection signal from the oil pressure sensor 6a, and based on this corrected command value, the electric motor 21. Therefore, the rotation speed of the pump 1, which is rotated by the electric motor 21 driven by the corrected rotation speed command value and the return hydraulic pressure, corresponds to the amount of operation of the lift lever 5, and the rotation speed of the pump 1 is adjusted accordingly. A flow rate of return oil flows out from the lift cylinder 7, and the fork F descends at an accurate speed.

Also, when the fork F is under a heavy load and the lift lever 5 is operated down alone, high pressure return oil is released into the lift cylinder 7.
and flows into the lift conduit 6.

In accordance with the detection signal from the oil pressure sensor 6a based on this return oil pressure, the controller 20 subtracts a large correction value from the value corresponding to the lift lever operation amount to significantly lower the rotation speed command value, and the pump 10 based on the high pressure return oil The electric motor 21 is driven at a rotational speed that is lower by a value corresponding to the rotational speed. Therefore, the rotational speed of the pump 1 driven by the return oil and the electric motor 21 accurately corresponds to the operation amount of the lift lever 5, making it possible to control the lowering speed of the fork F with high precision.

Also, when the lift lever 5 is lowered, the tilt lever 1
0 is tilted forward or backward, the controller 20 corrects the rotational speed command value of the electric motor 21 with a correction value based on the return oil pressure, so that it corresponds accurately to the operation amount of the lift lever 5, as described above. The rotational speed of the pump 1, that is, the lowering speed of the fork F is controlled.

Note that when the fork F is lowered, the rotational speed of the pump 1 exceeds the rotational speed of the electric motor 21.
functions as a hydraulic motor and causes the electric motor 21 to work as a generator. This produces the additional effect that the electric motor 21 performs power regeneration and the battery 24 is charged.

Furthermore, as shown in FIG. 2, when the tilt lever 10 is operated to tilt forward or backward during the lift lever 5's upward operation, the controller 20 selects the larger of the rotational speed command values based on the operating amounts of the levers 5 and 10. The pump l is driven via the electric motor 21 at a rotational speed command value of . Also, 4th.
As shown in FIG. 5, when the tilt lever 10 is operated alone, the controller 20 drives the pump 1 via the electric motor 21 at each rotational speed command value based on the operating amount of the tilt lever IO.

In the embodiment described above, when the lift lever 5 is lowered, the controller 20 sets the rotation speed command value of the electric motor 21 according to the lever operation amount based on the load on the fork F (according to the magnitude of the return oil pressure in the lift pipe 6). The pump 1 is rotated by the electric motor 21 which rotates at a speed based on the reduced rotational speed command value and the return hydraulic pressure.Therefore, the pump 1 rotates at a rotational speed according to the operation amount of the lift lever 5. The return oil is allowed to flow out from within the lift cylinder 7. As a result, the fork F is lowered at a speed that exactly corresponds to the amount of operation of the lift lever 5.

Note that the present invention is not limited to the embodiments described above; for example, (1) the oil pressure sensor 6a is attached to the bottom chamber 7a of the lift cylinder 7 or the return pipe 8, (2) the induction motor 21 is replaced with a DC motor; Arbitrary changes, such as adopting the above, are possible as long as they do not deviate from the spirit of the invention.

[Effects] As described in detail above, according to the present invention, the cargo handling member descends accurately according to the indicated speed, and exhibits an excellent effect of enabling detailed cargo handling operations.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing the hydraulic and electrical configuration of the forklift of the present invention, Figure 2 is a circuit diagram showing the hydraulic and electrical configuration when the fork is raised, and Figure 3 is the hydraulic diagram when the fork is lowered. and a circuit diagram showing the electrical configuration, Figure 4 is a circuit diagram showing the hydraulic and electrical configuration when the fork is tilted forward, and Figure 5 is a circuit diagram showing the 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 diagram showing a method of calculating a correction value for correcting the rotational speed command value based on the lift lever operation amount according to the return oil pressure. FIG. 8 is a hydraulic and electrical circuit diagram showing a conventional example. Hydraulic pump 1, lift control valve 4 as a switching control valve,
A lift lever 5 as a speed command means, an oil pressure sensor 6a as a load detection means, a lift cylinder 7, a lift operation sensor 16 as an operation amount detection means, a rotation speed calculation means, a drive control means, a controller 20 as a rotation speed correction means, An induction motor 21, a battery 24, and a fork F as a cargo handling member.

Claims (1)

[Scope of Claims] 1. A cargo handling member that is lifted and lowered to perform cargo handling work; a lift cylinder that raises the cargo handling member by an extension operation and contracts due to a load when the cargo handling member is lowered; and the lift. Rotationally driven to operate the cylinder,
Supply hydraulic oil to the lift cylinder to extend it,
Furthermore, when the cylinder contracts, a hydraulic pump whose rotational speed is increased according to the pressure value of return oil from the cylinder based on the load of the cargo handling member, and a hydraulic pump that is driven by electric power supplied from a battery to rotate the hydraulic pump. an electric motor; a speed instruction means that is operated when the cargo handling member is raised or lowered and instructs to change the lifting speed of the cargo handling member in accordance with the amount of operation; and an operation amount detection means that detects the amount of operation of the speed instruction means; Hydraulic pressure in a battery-powered industrial vehicle, comprising a rotational speed calculation means for calculating the rotational speed of the electric motor based on the detection result of the operation amount detection means, and a drive control means for driving and controlling the electric motor based on the calculation result of the calculation means. In the apparatus, the load detection means detects a value of the load on the cargo handling member; and the rotation speed calculation means is configured to absorb an increase in the rotation speed of the hydraulic pump due to return oil based on the detection result of the load detection means. A hydraulic system for a battery-powered industrial vehicle, which is provided with rotational speed correction means for appropriately correcting the calculated rotational speed of an electric motor.