JP2570851B2 - Hydraulic devices in battery-powered industrial vehicles - Google Patents

Description

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

[Related Art] In a battery-driven industrial vehicle including an electric motor that drives a pump of a hydraulic device for cargo handling, for example, a battery forklift, a hydraulic pump that functions as a motor is used by returning oil from a lift cylinder to generate an electric motor. There is a device that acts as a power source to perform battery regeneration.

As such a regenerative hydraulic device, the applicant of the present application has proposed a device shown in FIG. 8 in Japanese Patent Application No. 63-174405. That is, the controller C drives the induction motor 49 based on signals from the limit switches LS1 and LS2 that detect the operation directions of the lift lever 40 and the tilt lever 41 and the potentiometers P1 and P2 that detect the operation amounts of both levers 40 and 41. Then, the hydraulic pump 42 is driven, and hydraulic oil is sucked from the oil tank via the regenerative check valve 51. Then, the tilt control valve 47 is switched and controlled based on the operation of the tilt lever 41, hydraulic fluid is supplied to the tilt cylinder 48, which expands and contracts, and the fork tilt operation is performed.

Further, hydraulic oil is supplied from the hydraulic pump 42 to the lift cylinder 45 via the lift control valve 44 held at the position a based on the lifting operation of the lift lever 40, and the fork is raised. Further, when the lift control valve 44 is switched to the position c based on the lowering operation of the lift lever 40, the return oil from the lift cylinder 45 due to the load of the fork passes through the lift control valve 44 to the return line 46. Pumped.

The lowering operation of the lift lever 40 is performed by a limit switch LS.
When 1 is detected, the controller C sets the limit switch L
The regenerative braking mode is executed based on the detection result of S1. Then, when the return oil flows into the hydraulic pump 42 via the return pipe 46, the hydraulic pump 42 functions as a hydraulic motor by the oil pressure of the return oil and regenerates and drives the electric motor 49. As a result, the motor 49 functions as a generator, and the battery 50
Is to be charged.

However, the hydraulic pressure of the return oil flowing from the lift cylinder 45 to the hydraulic pump 42 is determined by the load on the fork. When the load weight of the fork is small and the fork is lowered with a light load, the pressure of the return oil also falls below the rotation speed command value based on the lever operation amount, and the hydraulic pump
Not enough to drive 42 as a hydraulic motor. For this reason, when the number of rotations of the electric motor 49 falls below the predetermined value despite the lowering of the fork, the electric motor 45 does not perform regeneration, performs power running operation, and consumes battery power.

Therefore, the present applicant has proposed a hydraulic device as shown in FIG. In this device, an electromagnetic fog valve 52 is interposed between the tank and the pump 42, and when the return oil pressure in the lift pipe 53 falls below a preset lower limit of regeneration, a signal from the oil pressure sensor 54 detecting this is detected. As a result, the controller switches the switching valve 52 to the position "a" to collect the return oil in the tank. This prevents the low-pressure return oil from flowing into the pump 42, prevents the electric motor 49 from performing a power running operation, and avoids unnecessary consumption of battery power.

However, even in this hydraulic device, when the fork is suddenly switched from the ascending position to the descending position with a light load, the hydraulic oil generated in the lift cylinder 45 immediately thereafter causes the second movement to occur.
As shown in FIG. 10, the hydraulic pressure returns to the lift pipe 53 and pulsation occurs in the hydraulic pressure. Therefore, the switching valve 52 is repeatedly opened and closed, and the return oil intermittently passes through the switching valve 52 and flows into the tank. Accordingly, hunting occurs in the switching valve 52, and the usability of the lift lever 40 is reduced, and the stable lowering of the cargo handling member is not performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and an object thereof is to stop the rotation of the electric motor when the loading / unloading member descends under a light load and the electric motor cannot perform a regenerative operation. It is an object of the present invention to provide a hydraulic circuit having a power regeneration function in a battery-type industrial vehicle, which enables saving and further prevents a malfunction such as hunting of components in the circuit and enables a stable lowering of a cargo handling member. .

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention is based on a lift cylinder for lifting and lowering a cargo handling member, and a lift cylinder driven to operate the lift cylinder, which is raised by a switching operation means. A hydraulic pump that supplies hydraulic oil to the cylinder, and is driven to rotate at a pressure of return oil exceeding a predetermined value when the lift cylinder is contracted based on the lowered position, and functions as a hydraulic motor, A lift control valve interposed between the hydraulic pump and an electric motor driven by electric power supplied from a battery to rotate the hydraulic pump and regenerate electric power of the battery by a hydraulic pump functioning as a hydraulic motor. And a return path for selectively switching the return direction of the return oil to the hydraulic pump side and the drain side in the return oil return path. Switching means, when the pressure of the return oil can cause the hydraulic pump to function as a hydraulic motor, return path switching means to the hydraulic pump side,
When the pressure of the return oil does not allow the hydraulic pump to function as a hydraulic motor, a pilot fluid passage for communicating the return passage switching means to the drain side, and a sealing means provided in the pilot fluid passage for closing the pilot fluid passage. In addition, when the lift control valve closes the return path of the return oil, the closing means is opened to provide a block release means for enabling the backflow of the pilot fluid.

[Operation] The present invention adopts the above-mentioned solution means,
When the pressure of the return oil reaches a value that allows the hydraulic pump to function as a hydraulic motor, pilot pressure is applied to the return path switching means via the pilot fluid passage, and the return path switching means is connected to the hydraulic pump. Thereafter, when the pressure of the return oil drops to a value at which the hydraulic pump cannot function as a hydraulic motor, the pilot fluid passage is blocked by the blocking means and the backflow of the pilot fluid is prevented, so that the return path switching means The pilot pressure is prevented from being released,
The return path switching means is held at the hydraulic pump side communication position.
Then, the blocking means is opened by the blocking release means, and backflow of the pilot fluid is allowed in the pilot fluid passage,
The pilot fluid pressure is released from the return path switching means,
The return path switching means is switched to the drain side communication position.

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

In FIG. 1, a hydraulic pump 1 sucks hydraulic oil stored in an oil tank T via a regenerative check valve 2a of a supply pipe 2 and then a main pipe in a fork drive hydraulic circuit H. Discharge to 3. A lift control valve 4 is provided in the main conduit 3, and the lift control valve 4 instructs lifting and lowering and stopping of the fork. The lift lever 5 can be switched to three positions a, b, and c corresponding to the upward, neutral, and downward operation positions.

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

Further, at the position b (FIG. 4) based on the neutral position of the lift lever 5, the lift control valve 4 shuts off the lift line 6 from the main line 3 and the return line 8, and Fluctuations in the flow rate of the hydraulic oil are prevented, the pressure is maintained without contraction, and the main pipeline 3 is opened downstream.

The lift control valve 4 is at a position c based on the lowering operation position of the lift lever 5 (FIGS. 3A, 6B and 6).
In, the pipeline 6 for lift and the pipeline 8 for return are communicated. A pilot control switching valve 8a as a return path switching means capable of switching between a and b positions is provided on a branch path D of the return pipe 8.
Is provided.

A switching pilot line 6a as a pilot fluid passage is connected to the switching valve 8a from a connection point J of the branch passage D. And especially as shown in FIG. 3 (b),
When the internal pressure of the lift pipe 6 exceeds the pilot set pressure of the switching valve 8a, the switching pilot fluid transmitted from the check pilot pipe 6a through the check valve 6b and the pressure fluctuation preventing nipple valve 6c is transmitted. The switching valve 8a is set to b according to the pressure
The position can be switched from the position to the position a.

That is, when the return hydraulic pressure in the lift pipe 6 according to the load of the lowered fork is equal to or lower than the pilot set pressure, the switching pilot pressure does not act on the switching valve 8a, and the switching valve 8a is moved to the position b (third position). (A), and when the return oil pressure exceeds the pilot set pressure, the switching valve 8a is held at the position a (FIGS. 3 (b) and 6) and closed. The switching valve 8a returns the return oil flowing from the lift cylinder 7 into the return pipe 8 at the position a to return between the regenerative check valve 2a of the supply pipe 2 and the hydraulic pump 1.
The return oil whose flow to the tank T is blocked by the regenerative check valve 2a in the supply pipe 2 flows into the hydraulic pump 1 and drives it.

If the return oil pressure in the lift line 6 falls below the pilot set pressure after the switch valve 8a is once switched to the position a, the switching pilot fluid will not flow into the switch pilot line 6a. The switching pilot fluid for applying pressure to the switching valve 8a has its return path closed by the check valve 6b, and keeps the switching valve 8a at the position a at a high pressure.

As shown in FIG. 7, when the lift control valve 4 is switched to the position b in accordance with the neutral operation of the lift lever 5, the pressure passage 4a provided in the central normal chamber of the lift control valve 4 opens the pilot fluid line O for opening. The check valve 6b is opened by the opening pilot pressure applied to the valve seat side of the check valve 6b via the same pipeline O. As a result, the switching valve 8a is switched to the position b, and the return oil passing from the lift cylinder 7 through the return pipe 8 is returned to the tank T from the drain pipe 15 through the bypass pipe 8b.

In this embodiment, an opening pilot pressure for opening the check valve 6b, which is closed by the hydraulic pressure acting from the switching valve 8a side, is set according to the opening pilot ratio of the check valve 6b. .

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

The tilt control valve 9 controls the amount of oil in the front chamber 14a and the rear chamber 14b of the tilt cylinder 14 by switching the position thereof, thereby contracting the cylinder 14.
At a position (FIGS. 2 and 5) based on the rearwardly inclined position 10, the backwardly inclined line 12 communicates with the tilt line 11 and the forwardly inclined line 13 communicates with the drain line 15, respectively. 1 to supply hydraulic oil to the front chamber 14a of the tilt cylinder 14 and allow the hydraulic oil in the rear chamber 14b to flow out to the oil tank T,
The fork is tilted backward by contracting the tilt cylinder 14.

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

Further, based on the neutral position of the tilt lever 10, the tilt control valve 9 is held at the position b (FIGS. 3 (a) and 3 (b)), and the forward and backward tilt pipes 13 and 12 are tilted. Line 1
The fork is kept in the inclined state at that time without changing the amount of oil in the tilt cylinder 14, and the main line 3 is communicated with the oil tank T without any change in the oil amount in the tilt cylinder 14.

When the lift lever 5 is operated to the raised position and the tilt lever 10 is operated to one of the forward and backward tilt positions (for example, the backward tilt), the lift control valve 4 is moved to the a position as shown in FIG. In addition, the switching valve 8a is also held at the position a to communicate the lift cylinder 7 and the pump 1, and the tilt cylinder 14 is positioned at either a or c (position a in the drawing).
Is connected to the pump 1 and the tank T via the tilt control valve 9 and is expanded and contracted. Therefore, the fork performs a tilt operation while rising.

When the lift lever 5 is operated to descend and the tilt lever 10 is operated to any position (for example, forward inclination), the lift control valve 4 is moved to the position c as shown in FIG. The switching valve 8a is held at the position a, and the lift cylinder 7 and the pump 1 are communicated with each other. The return oil flowing from the lift cylinder 7 flows into the pump 1 due to the load of the fork. And the tilt cylinder 14 is
The tilt cylinder is returned from the lift cylinder 7 through the pump 1 by being connected to the pump 1 and the tank T via the tilt control valve 9 at one of the positions a and c (position c in the drawing). 14 is stretched.

Therefore, the fork performs a tilt operation while descending in the same manner as when ascending, and the forklift and the tilt can be simultaneously operated.

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

The ascending, neutral and descending operation positions of the lift lever 5 are detected by a lift operation position sensor 16 comprising a limit switch, and the operation amount at the ascending and descending positions of the lift lever 5 is a lift operation amount comprising a potentiometer. The signal is detected by the sensor 17, and the detection signal is input to the controller 20. The forward tilt, neutral and backward tilt positions of the tilt lever 10 are detected by a tilt operation position sensor 18 comprising a limit switch, and the amount of operation of the lever 10 at the forward tilt position and the backward tilt position is comprised of a tilt potentiometer. It is detected by the operation amount sensor 19 and outputs each detection signal to the controller 20.

The switching valve stroke sensor 22 includes a potentiometer, detects the amount of movement of the spool of the switching valve 8a, and outputs a detection signal to the controller 20. Then, based on this detection signal, the controller 20 switches the switching positions a and b of the switching valve 8a.
Judge.

The controller 20 controls the drive power of a battery 24 to supply the power to an induction motor 21, which is connected to the hydraulic pump 1.

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

When the lift lever 5 and the tilt lever 10 are operated at the same time, the controller 20 calculates a rotation speed command value for each operation amount, and determines the larger rotation speed command value of the two command values as the rotation speed of the electric motor 21. It is set as a number. The controller 20 controls the electric power supplied from the battery 24 to the motor 21 based on the calculated rotation speed command value, and drives the motor 21 at a rotation speed according to the rotation speed command value to discharge the hydraulic pump 1. Adjust the volume. That is, the lift lever 5 and the tilt lever 10
The fork elevating speed and the mast tilting speed are controlled in accordance with the respective operation amounts of.

When the lift lever 5 is independently lowered, the controller 20 controls the electric motor 21 based on a signal from the stroke sensor 22.
To control the rotation of That is, when the switching valve 8a is at the position "a", the rotation of the electric motor 21 is controlled at a speed according to the rotation speed command value based on a signal from the stroke sensor 22 which detects this. Then, the electric motor 21 is driven as a generator by the pump 1 functioning as a hydraulic motor by the return oil flowing from the lift cylinder 7 via the switching valve 8a, and the battery 24 is charged via the controller 20.

Further, when the switching valve 8a is at the position "b", based on a signal from the stroke sensor 22 which detects this, the controller
20 stops the drive of the electric motor 21. The tilt lever 10
During the operation of, the controller 20 invalidates the signal from the stroke sensor 22 and drives the electric motor 21 even when the switching valve 8a is at the position b.

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

Now, as shown in FIG. 3 (b), when the lift lever 5 is operated to descend with a heavy load on the fork, the return hydraulic pressure flowing into the lift pipe 6 from the lift cylinder 7 exceeds the pilot set pressure. . Then, after the pressure fluctuation of the pilot fluid flowing through the pilot pipe line 6a via the branch passage D is adjusted by the check valve 6b and the nipple valve 6c, the switching valve 8a
Is transmitted to And the switching valve is operated by this pilot pressure.
8a is held in the a position. For this reason, the controller 20 uses the rotation speed command value according to the operation amount of the lift lever 5 to
21, that is, the pump 1 is rotated. Further, the return oil is forcibly pumped to the pump 1 to increase its rotation speed,
The electric motor 21 rotating following the above functions as a generator, and the battery 24 is charged via the controller 20.

When the fork is lowered with no load or an extremely low load, the return hydraulic pressure does not reach the pilot set pressure of the switching valve 8a, and the switching valve 8a at the position b is not switched. Therefore, low-pressure return oil does not flow to the hydraulic pump 1 and the controller 20 also stops and holds the electric motor 21 in accordance with a signal from the stroke sensor 22, so that unnecessary energy is not consumed.

However, when the lift lever 5 is suddenly switched from the raised position to the lowered position, the hydraulic pressure in the piston chamber 7a of the lift cylinder 7 immediately fluctuates. And the tenth
As shown in the drawing, the return hydraulic pressure in the lift pipe 6 instantaneously exceeds the pilot set pressure due to the dance. Then, the switching valve 8a at the position b is switched to the position a by the switching pilot pressure transmitted from the pilot line 6a.

Thereafter, the return hydraulic pressure is decreased according to the load of the fork, and the pilot fluid for closing does not flow into the pilot line 6 thereafter. However, the switching valve of pilot line 6a
Between 8a and the check valve 6b, the closing pilot fluid that has applied the pilot pressure to the switching valve 8a is blocked from retreating by the check valve 6b, so that the switching valve 8a and the check valve 6b
Is kept constant. Therefore, the switching pilot valve is not released from the switching valve 8a and the switching valve
8a continues to be held at the a position, and the return oil continues to flow into the pump 1. Therefore, at the time of the fork lowering switching operation,
Although the return valve 8a intermittently exceeds the switching pilot set pressure due to the return oil pulsating in the lift line 6 and intermittently,
No hunting occurs.

In addition, since the pressure is held by the check valve 6b while the fork is being lowered, the return of the spool of the switching valve 8a is prevented. Therefore, the motor is provided with a function of preventing the motor from stopping during the descent of the fork and preventing a change in the descent speed accompanying the descent.

Further, the controller 20 drives the electric motor 21 according to a signal from the stroke sensor 22 that detects that the switching valve 8a is at the position a. At this time, the return oil flows into the pump 1 from the switching valve 8a, and the pump 1 regenerates and drives the electric motor 21.

Thereafter, as shown in FIG. 7, when the lift lever 5 is switched to the neutral position, the opening pilot fluid flows to the check valve 6b via the opening pilot line O, and the switching valve
The check valve 6b, which is closed by the pressure between the check valve 8a and the check valve 6b, is opened. Then, the switching valve 8a is switched to the position b.

Further, as shown in FIG. 5, when the tilt lever 10 is operated alone, the switching valve 8a is held at the position b, and the return oil is collected in the tank T. At this time, the controller 20 rotates the pump 1 by driving the electric motor 21. Thereby, the tilt cylinder is controlled via the tilt control valve 9.
Hydraulic oil is supplied to 14 to assure stable tilting of the fork.

As shown in FIGS. 2 and 6, when the lift lever 5 is moved up or down and the tilt lever 10 is moved to one of the forward and backward tilt positions, the controller 20 is driven by the electric motor.
21 is rotated with a larger rotation speed command value among the respective rotation speed command values based on the operation amounts of both levers 5 and 10. Then, the controller 20 drives the electric motor 21 regardless of the position of the switching valve 8a, that is, regardless of the presence or absence of a signal from the stroke sensor 22,
The electric motor 21 is driven in accordance with the rotation speed command value based on the operation amounts of the levers 5 and 10 having the larger operation amounts, and the mast is tilted by the hydraulic oil supplied from the pump 1 to the tilt cylinder 14.

As described above, in this embodiment, when the fork is rapidly switched from the ascending operation to the descending operation with a light load, the return hydraulic pressure due to the hydraulic pressure immediately after that temporarily exceeds the switching pilot set pressure. Then, the switching valve 8a is closed at the position a by the pressure of the switching pilot fluid generated at this time, and then the return oil falls below the switching pilot set pressure according to the fork load, but flows backward from the switching valve 8a side. Since the reversing path of the switching pilot fluid is blocked by the check valve 6b, the switching valve 8a is held at the position a, and the return oil rotates the pump 1, that is, the electric motor 21, to perform a stable cargo handling operation. When the lift lever 5 is switched to the neutral position, the check valve 6b is opened by the pressure of the opening pilot fluid.

Therefore, the switching pilot pressure is gradually released from the switching valve 8a, the switching valve 8a is not suddenly switched to the position b, and the oil does not return to the switching valve 8a at once and pass through.
Therefore, hunting of the switching valve 8a is avoided.

Also, as shown in FIG. 3 (b), when the fork is lowered with a light load, the main pipe 3 is communicated with the opening pilot pipe O via the lift control valve 4, but the stroke sensor is not used. The electric motor 21 rotates the hydraulic pump 1 under the control of the controller 20 based on the signal from the signal 22, and the hydraulic oil is actively sent from the pump 1 to the tank T, so that the main pipeline 3 is connected to the lift control valve 4. Negative pressure is generated in the pipeline. Therefore, no pilot pressure is generated in the opening pilot line O, and the check valve 6b is not opened.

The present invention is not limited to the above-described embodiment. For example, a DC motor may be used in place of the induction motor 21, or the connecting pipe between the switching valve 8a and the tank T may be connected to the bypass pipe 8b and the drain pipe. Instead of the pipe 15, the pipe is directly guided to the tank T in the same manner as in the conventional example shown in FIG. 9 to reduce the resistance of the return oil in the pipe. Is of course possible.

[Effects] As described above in detail, according to the present invention, when the loading / unloading member descends with a light load and the motor cannot perform the regenerative operation and performs the power running operation, the rotation of the motor is stopped to save energy. In addition to ensuring a good feeling of use of the switching operation member, avoiding a malfunction such as hunting of devices in the circuit such as the switching valve and the electric motor, preventing a change in the descending operation, and ensuring a stable operation of the cargo handling member. It has an excellent effect of being able to descend.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a hydraulic and electrical configuration of a forklift according to a first embodiment of the present invention, FIG. 2 is a circuit diagram showing a hydraulic and electrical configuration when a fork is raised, and FIG. ) And (b) are circuit diagrams showing hydraulic and electrical configurations when the fork is under heavy load and low load respectively, FIG. 4 is a circuit diagram showing hydraulic and electrical configurations when the fork is tilted forward, and FIG. FIG. 5 is a circuit diagram showing a hydraulic and electrical configuration when the fork is tilted backward, FIG. 6 is a circuit diagram when the fork is lowered and tilted forward, and FIG. 7 is a circuit showing a state where the fork is stopped after the fork is lowered. FIGS. 8, 8 and 9 are circuit diagrams showing a conventional example, respectively, and FIG. 10 is a diagram showing a change in return hydraulic pressure of the hydraulic circuit shown in FIG. Hydraulic pump 1, lift control valve 4, lift cylinder 7,
A switching pilot line 6a as a pilot fluid passage,
A check valve 6b as a closing means, a switching valve 8a as a return path switching means, an induction motor 21, a battery 24, and an opening pilot pipe O as a sealing release means.

Claims (1)

(57) [Claims] 1. A lift cylinder for raising and lowering a cargo handling member, and a hydraulic cylinder which is driven to operate the lift cylinder and supplies hydraulic oil to the cylinder based on an ascending position of a switching operation means. When contracted, the hydraulic pump is driven to rotate at a pressure of return oil exceeding a predetermined value and functions as a hydraulic motor; a lift control valve interposed between the lift cylinder and the hydraulic pump; and a battery. An electric motor that is driven by electric power supplied from the motor and rotates the hydraulic pump and regenerates electric power of a battery by a hydraulic pump that functions as a hydraulic motor. A return path switching means for selectively switching to a hydraulic pump side and a drain side; and A pilot fluid passage for communicating the return path switching means to the hydraulic pump side when the hydraulic pump can function, and a return path switching means to the drain side when the pressure of the return oil cannot function the hydraulic pump as a hydraulic motor; Closing means provided in the fluid passage, for closing the pilot fluid passage, when the lift control valve closes the return oil return path,
A hydraulic system for a battery-powered industrial vehicle, comprising: a sealing release means for opening the sealing means and allowing a backflow of the pilot fluid.