JP3376263B2 - Hydraulic devices in battery-powered industrial vehicles - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic system for a battery-powered industrial vehicle, and more particularly to a battery for driving a generator by a hydraulic motor provided in a return line of a lift cylinder to regenerate electric power from a battery power source. TECHNICAL FIELD The present invention relates to a hydraulic system of a type industrial vehicle.

[0002]

2. Description of the Related Art In a battery-powered industrial vehicle such as a forklift that uses a battery as a power source, a generator is driven by using a hydraulic motor driven by return oil from a lift cylinder that moves a cargo handling member up and down. There is a device for performing regeneration (for example, JP-A-55-5699).
No. 9). In this device, as shown in FIG. 28, a bottom chamber 101a of a lift cylinder 101 of a forklift truck is used.
The lift cylinder line 102 and the lift control valve 103
Also, it is connected to the oil tank 105 via the pressure oil supply pipe line 104. A hydraulic pump 106 is provided in the middle of the pressure oil supply line 104. Also, the lift control valve 103
Is connected to the oil tank 105 via a return line 107, and the lift cylinder line 102 is connected to the pressure oil supply line 104 and the return line 10 by operating the operation lever 108.
7 in a state of communicating with one of the two or both pipelines 104, 10
It is switched to a state in which communication with 7 is impossible. Return line 1
A hydraulic motor 109 is provided in the middle of 07, and a generator 110 is connected to the hydraulic motor 109.

When the lift control valve 103 is held in the lowered position, that is, in the state where the lift cylinder pipe line 102 and the return pipe line 107 communicate with each other, by operating the operation lever 108,
The pressure oil in the bottom chamber 101a is supplied to the hydraulic motor 109. The generator 1 connected to the hydraulic motor 109
10 is driven, and the generated power is regenerated in a battery (not shown). Further, the pressure detection device 111 is provided between the lift control valve 103 and the hydraulic motor 109, and the field control according to the pressure is performed to stabilize the descending speed of the fork 112 and improve the regenerative effect. It is disclosed. Specifically, a variable resistor is connected in series to the field winding of the generator 110, and the set value of the variable resistor is changed according to the pressure of the return oil.

[0004]

In industrial vehicles such as forklifts, it is required that the lowering speed of a cargo handling member (cargo handling attachment) such as a fork be a predetermined speed regardless of the presence or absence of a load and the difference in the weight of the load. ing. In the conventional device, when the load is relatively heavy and the pressure of the hydraulic oil in the bottom chamber 101a is large, the lowering speed of the cargo handling member can be set to a predetermined speed. However, when the load is relatively light or when there is no load (light load), it is difficult to secure a predetermined descending speed. Because, in the conventional device, the bottom chamber 101
Since all the return oil from a returns to the oil tank 105 through the hydraulic motor 109, even if the starting torque of the generator 110 is set to the minimum or even 0, the hydraulic motor 109
The resistance slows down the speed.

Further, in the field control in which the set value of the variable resistor is changed according to the pressure of the return oil, the regenerative electric power fluctuates even if the hydraulic pressure is the same depending on the discharge state of the battery, and the descending speed cannot be stabilized. .

The present invention has been made in view of the above problems, and an object thereof is a battery-powered industry which can secure a descending speed at a light load and can obtain regenerative electric power at a predetermined load or more. To provide a hydraulic system for a vehicle.

[0007]

In order to achieve the above object, in the invention according to claim 1, a lift cylinder for raising and lowering a cargo handling member, a battery power supply, and a motor driven by the battery power supply are used. A hydraulic pump that is driven to supply hydraulic oil to the lift cylinder; a lift control valve that is interposed between the lift cylinder and the hydraulic pump and that expands and contracts the lift cylinder by switching positions; and the lift control valve. In a hydraulic system in a battery-powered industrial vehicle, comprising: a hydraulic oil tank; and a return conduit for returning pressure oil in the bottom chamber of the lift cylinder to the hydraulic oil tank when the lift control valve is lowered.
A hydraulic motor disposed in the return pipe, a generator driven by the hydraulic motor to regenerate electric power of a battery power source, and a branch from the return pipe on the upstream side of the hydraulic motor, and a flow rate in the middle. A bypass having a control valve is provided, and the flow rate characteristic of the flow rate control valve is set so that the sum of the flow rate of the hydraulic motor and the flow rate of the flow rate control valve is equivalent to the target lowering speed of the cargo handling member when the load is light. So that

According to a second aspect of the present invention, a separately excited generator is used as the generator, and a control means for performing field control of the generator is provided, and the control means causes all return oil to pass through the hydraulic motor. In the state, the field control is performed so that the rotation speed of the generator becomes a predetermined rotation speed corresponding to the target lowering speed.

According to a third aspect of the present invention, in the second aspect of the present invention, the bypass circuit is merged with the return pipe downstream of the hydraulic motor, and a power source under heavy load is provided downstream of the junction. A second flow rate control valve is provided in which the set flow rate is set to the target lowering speed equivalent amount in the shutoff state.

According to another aspect of the invention, a lift cylinder for raising and lowering the cargo handling member, a battery power source, and a hydraulic pump driven by a motor driven by the battery power source to supply hydraulic oil to the lift cylinder. And a lift control valve that is interposed between the lift cylinder and the hydraulic pump and that expands and contracts the lift cylinder by switching the position, and lowering operation of the lift control valve that connects the lift control valve and the hydraulic oil tank to each other. In a hydraulic system in a battery-powered industrial vehicle, which is provided with a return conduit for returning pressure oil in the bottom chamber of the lift cylinder to the hydraulic oil tank, a hydraulic motor arranged in the return conduit, and the hydraulic motor. And a generator that drives the battery to regenerate electric power from a battery power source, and a branch from the return pipe on the upstream side of the hydraulic motor. In addition, a detour that joins on the downstream side of the hydraulic motor is provided, the flow rate of the hydraulic motor is prioritized at the confluence of the return line and the detour, and the hydraulic motor responds to changes in the pressure of the detour. A flow rate control valve was provided to control the flow rate so that the sum of the passing flow rate and the bypass flow rate was constant.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the flow control valve includes a pressure of the hydraulic oil in the bypass or a downstream pressure of the hydraulic motor, and an urging means. Equipped with a spool that is moved by counteracting pressure,
The flow rate of the passage communicating with the hydraulic oil tank can be adjusted by operating the spool.

According to a sixth aspect of the invention, in the invention according to the fourth or fifth aspect, a separately excited generator is used as the generator, and a control means for performing field control of the generator is provided. The control means performs the field control so that the rotation speed of the generator becomes a predetermined rotation speed corresponding to the target lowering speed of the cargo handling member when the load is light, when all the return oil passes through the hydraulic motor.

According to a seventh aspect of the invention, in the invention according to any one of the fourth to sixth aspects, the bypass circuit is a logic for changing a bypass flow rate characteristic of the flow control valve. A valve and a switching valve that is arranged at a communication position that activates the logic valve when the pressure in the bottom chamber of the lift cylinder is equal to or higher than a predetermined pressure and is arranged at a shut-off position when the pressure is lower than the predetermined pressure are provided.

According to the first aspect of the present invention, the pressure oil in the bottom chamber of the lift cylinder is at least one of a return pipe communicating the lift control valve and the hydraulic oil tank, and a detour branched from the return pipe. And return to the hydraulic oil tank. When the pressure oil having a predetermined pressure or more passes through the return pipe, the hydraulic motor is operated and the generator is driven to regenerate electric power to the battery power supply. The sum of the flow rate of the hydraulic motor and the flow rate of the flow rate control valve becomes a flow rate corresponding to the target lowering speed of the cargo handling member at a light load due to the action of the flow rate control valve provided in the middle of the detour. Then, when the pressure of the pressure oil in the bottom chamber is low, the flow rate of the flow control valve increases, and when the pressure of the pressure oil in the bottom chamber is high, the flow rate of the hydraulic motor increases. Then, the descending speed of the cargo handling member becomes constant regardless of the load.

According to the second aspect of the invention, a separately excited generator is used as the generator, and the field control of the generator is performed by the control means. When all the return oil passes through the hydraulic motor, field control (external excitation control) is performed so that the rotation speed of the generator becomes a predetermined rotation speed corresponding to the target lowering speed.

According to a third aspect of the present invention, in the second aspect of the invention, the power supply is cut off during heavy load,
Even if the flow rate of the hydraulic motor increases, the flow rate is limited by the second flow rate control valve provided on the downstream side of the confluence of the bypass and the return pipe. Therefore, the descending speed of the cargo handling member is kept constant.

In the invention according to claim 4, the pressure oil in the bottom chamber of the lift cylinder is at least one of a return pipe communicating the lift control valve and the hydraulic oil tank, and a detour branched from the return pipe. And a flow rate control valve provided at the confluence of the return line and the detour to return to the hydraulic oil tank.
When pressure oil having a pressure equal to or higher than a predetermined pressure passes through the hydraulic motor, the hydraulic motor is operated and the generator is driven to regenerate electric power to the battery power supply. Due to the action of the flow rate control valve, the flow rate of the hydraulic motor is prioritized, and the flow rate is controlled so that the sum of the hydraulic motor passage flow rate and the bypass flow rate becomes constant in response to the change in the bypass pressure. Be seen.
When the pressure of the pressure oil in the bottom chamber, that is, the pressure of the pressure oil in the detour is low, the flow rate of the hydraulic motor decreases. Further, when the pressure of the pressure oil in the bottom chamber is high, the flow rate of the hydraulic motor increases. Then, the descending speed of the cargo handling member becomes constant regardless of the load (presence or absence of the load and weight of the load).

According to a fifth aspect of the invention, in the fourth aspect of the invention, the flow rate control valve includes a pressure of the hydraulic oil in the bypass or a downstream pressure of the hydraulic motor, and an urging means. The flow rate of the passage communicating with the hydraulic oil tank is adjusted by the operation of the spool that is moved in opposition to the pressure.
When the spool moves by a predetermined amount against the urging force of the urging means, the flow rate in the bypass becomes 0, and the entire amount flows in the hydraulic motor.

According to a sixth aspect of the present invention, in the fourth or fifth aspect of the present invention, the separately excited generator is used as the generator, and the field control of the generator is performed by the control means. When all the return oil passes through the hydraulic motor, field control (external excitation control) is performed so that the rotation speed of the generator becomes a predetermined rotation speed corresponding to the target lowering speed of the cargo handling member when the load is light.

According to a seventh aspect of the invention, in the invention according to any one of the fourth to sixth aspects, when the pressure in the bottom chamber of the lift cylinder is equal to or higher than a predetermined pressure, the switching valve is in the communicating position. Will be placed. Then, regeneration in the medium speed range becomes possible.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment in which the invention described in claims 4 to 6 is embodied in a battery-powered forklift will be described below with reference to FIGS. 1 to 5. To do.

As shown in FIG. 1, a lift cylinder 2 for raising and lowering a fork 1 as a cargo handling member is connected to a lift control valve 4 via a pipe line 3. Lift control valve 4
A direct acting spool valve is used for this. A manually operated three-position switching valve is used for the lift control valve 4, and a lift lever 5 for instructing the lifting and stopping of the fork 1 is lifted,
It is possible to switch between three states a, b, and c corresponding to the neutral and lowering operation positions.

A hydraulic pump 7 for supplying the hydraulic oil in the hydraulic oil tank 6 to the lift cylinder 2 is driven by a motor 8 which uses a battery E as a battery power source as a power source. The hydraulic pump 7 is connected to the port P ₁ of the lift control valve 4 via a hydraulic oil supply line 9. The lift control valve 4 is connected to the return line 10 at the port T _{1 and} to the line 3 at the port A ₁ . The pipe line 3 is connected to the bottom chamber 2 a of the lift cylinder 2. Return line 1
0 communicates the lift control valve 4 and the hydraulic oil tank 6, and plays a role of returning the pressure oil in the bottom chamber 2a of the lift cylinder 2 to the hydraulic oil tank 6 when the lift control valve 4 is lowered.

The lift control valve 4 is arranged at the position a based on the lifting operation of the lift lever 5, and at the position a, the hydraulic oil supply conduit 9 and the conduit 3 are communicated with each other to extend the lift cylinder 2. The lift control valve 4 is arranged at the position c based on the lowering operation of the lift lever 5, and the pipe 3 and the return pipe 10 are communicated with each other at the position c to make the lift cylinder 2
Contract. Further, the lift control valve 4 is arranged at the position b based on the neutral operation of the lift lever 5, and shuts off the communication between the pipeline 3 and the hydraulic oil supply pipeline 9 and the return pipeline 10.
The hydraulic oil in the lift cylinder 2 is prevented from moving and held without being expanded or contracted.

A hydraulic motor 11 is arranged in the return pipe 10, and a generator 12 is connected to the hydraulic motor 11. The generator 12 is driven by the hydraulic motor 11 to regenerate the electric power of the battery E. Generator 1
The second terminal is connected to the battery E via a control device 14 as a control means. The return pipe 10 is branched at the upstream side of the hydraulic motor 11 and is connected to a bypass 13 that joins at the downstream side of the hydraulic motor 11.
At the confluence of the return line 10 and the detour 13, the flow control valve 1
5 are provided. The flow control valve 15 is the hydraulic motor 1
The flow rate of 1 is prioritized, and the flow rate is controlled so that the sum of the hydraulic motor passage flow rate and the bypass flow rate becomes constant in response to the change in the pressure in the bypass 13.

Next, the flow control valve 15 will be described. As shown in FIGS. 2 to 4, the housing 1 of the flow control valve 15
A first port C1 connected to the detour 13 and a second port M1 connected to the return pipe 10 on the upstream side of the hydraulic motor 11 are formed at 6. Both ports C
1, 1 communicate with the passage 17. The passage 17 constitutes a part of the detour 13. Further, the housing 16 is provided with a third port M2 connected to the return pipe 10 on the downstream side of the hydraulic motor 11 and a fourth port T connected to the hydraulic oil tank 6 side. Hydraulic motor 1
1, the inlet is connected to the second port M1 and the outlet is connected to the third port M2. The third port M2 is connected to the passage 18 and the fourth port T is connected to the passage 19. The passages 17 to 19 are formed so that their ends are parallel to each other with a predetermined distance.

A housing portion 21 of a piston 20 as a spool which constitutes a spool valve is arranged in the housing 16 in a state of being orthogonal to the end portions of the passages 17 to 19.
The piston 20 is housed in the housing portion 21, and the open end of the housing portion 21 is closed by a cover 22. Cover 22
Are fixed by bolts 23. The piston 20 is formed in a substantially cylindrical shape and includes a damper chamber 24, a first chamber 25 and a second chamber 26. First chamber 25 is damper chamber 24
And the second chamber 26 and the damper chamber 24 and the first chamber.
The chamber 25 is partitioned by a partition wall 27, and a partition wall 27 is formed with a damper orifice 27a for communicating the two chambers 24, 25 with each other.

The piston 20 is formed with a first orifice 28 which allows the first chamber 25 and the passage 17 to communicate with each other. The first chamber 25 is formed to have a smaller sectional area, that is, a smaller diameter than the second chamber 26, and the first chamber 25 and the second chamber 26 are communicated with each other through the second orifice 29. The second orifice 29 is formed to have a predetermined diameter by fitting the orifice plate 30 to the piston 20. A third orifice 31 is formed between the passage 19 and the first end of the piston 20 (the left end in FIG. 2). A chamber 32 is formed in the housing 16 on the first end side of the piston 20. Second chamber 26 and chamber 3
A coil spring 33 as an urging means is interposed between the two ends. Due to the balance between the urging force of the coil spring 33 and the pressure of the hydraulic oil acting on the piston 20, the piston 20 has an end portion on the damper chamber 24 side shown in FIG.
It moves between a position where it abuts 2 and a position where it closes the passage 17 shown in FIG. The pressure for moving the piston 20 in the direction of closing the passage 17 against the biasing force of the coil spring 33 (flow control valve operating pressure) is set to be smaller than the pressure for operating the hydraulic motor 11 (hydraulic motor operating pressure). There is.

At the first end of the piston 20, the piston 2
A cutout portion 20a that connects the passage 19 with the second chamber 26 and the chamber 32 is formed when 0 is arranged at a position that closes the passage 17 shown in FIG. Further, in the state where the piston 20 is in contact with the cover 22 in the housing 16 in the position shown in FIG.
A recess 16a is formed to connect the passage 18 and the passage 18. The recess 16a is formed in an annular shape.

Next, the operation of the hydraulic device constructed as described above will be described. When the lift lever 5 is operated to be lifted, the lift spool is placed at the position a, and the hydraulic oil discharged from the hydraulic pump 7 enters the bottom chamber 2a of the lift cylinder 2 via the hydraulic oil supply pipe 9 and the pipe 3. It is supplied, the lift cylinder 2 extends, and the fork 1 rises. When the lift lever 5 is operated to be lowered, the lift spool is placed at the position c, the pipe 3 is communicated with the return pipe 10, and the bottom chamber 2 is closed.
The hydraulic oil a is returned to the hydraulic oil tank 6. Then, the lift cylinder 2 contracts and the fork 1 descends. Based on the neutral operation of the lift lever 5, the lift spool is b
The conduit 3 is located at the position, and the communication with the hydraulic oil supply conduit 9 and the return conduit 10 is blocked. As a result, movement of the hydraulic oil in the lift cylinder 2 is prevented, and the fork 1 is held at a desired position.

When the fork 1 descends, the hydraulic oil discharged from the bottom chamber 2a is guided to the flow control valve 15 from the first port C1 via the lift control valve 4. Further, the hydraulic motor 11 is diverted via the second port M1. As for the situation in which the hydraulic oil returns to the hydraulic oil tank 6, the entire amount is detour 1
There are three cases, that is, when passing through the detour 13 and when passing through the hydraulic motor 11, and when passing the entire amount through the hydraulic motor 11.

First, the case where the entire amount of hydraulic oil passes through the bypass 13 will be described. Since the flow control valve operating pressure <hydraulic motor operating pressure is set, the lift control valve 4
When the flow rate of hydraulic oil discharged through the engine is not large enough, that is, when there is no load or the load is light and the pressure of the hydraulic oil is less than the pressure required to operate the hydraulic motor 11 (during light load)
, The entire amount of hydraulic oil passes through the bypass 13.

The hydraulic oil introduced from the first port C1 to the flow control valve 15 is in the state shown in FIG.
First orifice 28 → first chamber 25 → second orifice 29
-> 2nd chamber 26-> 3rd orifice 31-> passage 19-> 4th port T is passed in the order of the flow control valve 15, and the return pipe 1
It is discharged to the hydraulic oil tank 6 through 0. When the amount of hydraulic oil is small, the opening area of the first orifice 28 is large, the pressure P1 of the passage 17, the pressure P2 of the first chamber 25, and the second chamber 26.
Is almost equal to the pressure P3. The flow rate gradually increases, and due to the pressure difference generated at the second orifice 29, the piston 20
Force F = S × (P2-P3) acting on the spring force F
When it becomes larger than s, the piston 20 is moved to the second chamber 26 side. However, S is the pressure receiving area of the piston 20.
Then, the opening area of the first orifice 28 is reduced until Fs = S × (P2−P3), and the excess pressure ΔP =
P1-P2 are absorbed by the first orifice 28.

Flow rate Q of fluid flowing through the second orifice 29
Is expressed by the following equation. Q = C × α × S0 × √ (P2-P3) where S0: orifice area, α: flow coefficient, P2-P
3: Pressure difference before and after the second orifice, C: constant.

Therefore, if the pressure difference before and after the second orifice 29 is made constant, the flow rate Q becomes constant. The pressure P2 in the first chamber 25 changes depending on the pressure P1 in the passage 17. Passage 1
The pressure P1 of 7 is equal to the pressure of the hydraulic oil discharged from the lift control valve 4. The opening degree of the lift control valve 4 changes depending on the operation amount of the lift lever 5 by the operator, and the bottom chamber 2
Even if the pressure of the hydraulic oil in a is the same, it differs depending on the opening degree of the lift control valve 4. The pressure of the hydraulic oil discharged from the lift control valve 4 also varies depending on the opening degree of the lift control valve 4.

When the flow rate control valve 15 is used, when the hydraulic oil discharged from the lift control valve 4 is not used for the operation of the hydraulic motor 11, the operator operates the lift lever while the fork 1 is descending. Even if the opening degree of the lift control valve 4 is changed, the piston 2 is controlled so that the pressure difference (P2-P3) before and after the second orifice 29 becomes constant as described above.
0 is moved. As a result, when hydraulic oil is discharged from the lift cylinder 2 at a flow rate (pressure) at which the hydraulic motor 11 is not operated, the lowering speed of the fork 1 is constant regardless of the presence or absence of a load and the weight of the load.

Next, a case will be described in which hydraulic fluid having a flow rate (pressure) at which the hydraulic motor 11 is operated is discharged from the lift control valve 4. In this case, after a part of the hydraulic oil flows through the hydraulic motor 11, it flows into the flow control valve 15, joins the hydraulic oil that does not pass through the hydraulic motor 11, and is discharged to the hydraulic oil tank 6. May flow into the flow control valve 15 via the hydraulic motor 11 and be discharged to the hydraulic oil tank 6.

When the hydraulic oil starts to flow through the hydraulic motor 11, the piston 20 is in the state of FIG. 3 in which the piston 20 has moved to the left from the state of FIG. In this state, the hydraulic motor 1
The passage 18 that guides the hydraulic oil from the first chamber 25 to the first chamber 25 is sufficiently open. Therefore, the pressure PM2 of the third port M2 and the pressure P2 of the first chamber 25 are substantially equal. In the first chamber 25, the flow rate Qc from the first orifice 28 and the flow rate from the third port M2, that is, the flow rate QM from the hydraulic motor 11 are provided.
And merge with each other, and the pressure difference (P2
-P3) is generated.

Flow rate QM flowing through the hydraulic motor 11
Is assumed to have a characteristic proportional to the difference (P1-P2) between the pressure P1 in the passage 17 and the pressure P2 in the first chamber 25,
The excess pressure ΔP = P1-P2 is absorbed by the first orifice 28 by the same action as described above. Therefore, also in this case, Fs = S × (P2−P3) becomes constant, and the flow rate Q discharged from the flow rate control valve 15 becomes constant. That is,
If the flow rate that flows in via the hydraulic motor 11 is QM,
The flow rate Qc is reduced by the flow rate QM. Then, the total flow rate Q is kept constant.

When the pressure of the hydraulic oil discharged from the lift control valve 4 further increases, the piston 20 moves further to the left from the state shown in FIG. 3, and the piston 20 is placed at a position where the first orifice 28 is fully closed. Then, the entire amount of the hydraulic oil returning to the hydraulic oil tank 6 passes through the hydraulic motor 11. When the pressure of the hydraulic oil discharged from the lift control valve 4 further increases from that state, the piston 20 further moves to the chamber 32 side as shown in FIG. 4, and the pressure difference ΔP = P3− at the third orifice 31. PT will be generated. That is, the pressure P3 rises so that the pressure difference ΔP = P2-P3 of the second orifice 29 becomes constant.

The force F1 acting on the piston 20 on the damper chamber 24 side is F1 = S × P2, and the force F2 acting on the piston 20 on the second chamber 26 side is F2 = S × P3 + F.
s. The piston 20 reduces the opening area of the third orifice 31 to a position where F1 = F2 and generates the pressure P3. Therefore, S × P2 = S × P3 + Fs,
P2-P3 = Fs / S. That is, the differential pressure ΔP = P2-P3 = Fs / when the hydraulic motor 11 does not operate.
Since it is almost the same as S, the flow rate Q discharged via the flow rate control valve 15 can be maintained at a constant amount.

Since the generator 12 is connected to the hydraulic motor 11, it is operated together with the hydraulic motor 11 to convert the kinetic energy of the hydraulic motor 11 into electric energy.
The electric power generated by the generator 12 is regenerated by the battery E.
If the voltage of the induced electromotive force generated by the generator 12 is higher than the voltage of the battery E, the power can be regenerated in the battery E. The control device 14 detects an electromotive force by a voltage sensor (not shown), and when the value is larger than the voltage of the battery E, switches the terminal of the generator 12 to the state of being electrically connected to the battery E. As a result, the electric power generated by the generator 12 is regenerated in the battery E.

As shown in FIG. 5, the amount Q of hydraulic oil (return oil) discharged from the lift cylinder 2 increases rapidly until the pressure P1 in the passage 17 reaches a predetermined pressure PD, and thereafter becomes substantially constant. . When the pressure P1 exceeds the predetermined pressure PD, a part of the hydraulic oil discharged from the lift cylinder 2 becomes the flow rate QM passing through the hydraulic motor 11, and the power generation by the generator 12 is performed. Further, the piston 20 is the first orifice 2
8 is fully closed, that is, in a state where at least a part of the return oil passes through the first orifice 28 (operating state A), the flow rate QM and the return oil passing through the first orifice 28 are Total flow rate with flow rate QC (= QM + Q
C) is maintained so that the flow rate QA corresponds to the target speed when the fork 1 descends when the load is light and the lift control valve 4 is fully open. Then, even in a state where all the return oil discharged from the lift cylinder 2 passes through the hydraulic motor 11 (operating state B), the flow rate QM is controlled to be the flow rate QA corresponding to the target speed.

This embodiment has the following effects. (A) The sum of the hydraulic motor passing flow rate and the bypass flow rate is kept constant by the action of the flow rate control valve 15 arranged in the middle of the return pipe 10 that connects the lift control valve 4 and the hydraulic oil tank 6. The flow rate of the flow rate control valve 15 is controlled so that Therefore, the lowering speed of the fork 1, that is, the maximum lowering speed in the fully opened state of the lift control valve 4 can be controlled to be constant regardless of the difference in load, that is, the presence or absence of a load on the fork 1 and the weight of the load.

(B) The flow rate control valve 15 is the hydraulic motor 11
When the amount of hydraulic oil discharged from the lift control valve 4 is large, a large amount of hydraulic oil is made to flow to the hydraulic motor 11 side so that the energy of the hydraulic oil can be effectively converted into electric power.

(C) Since the lift control valve 4 is of a manual type, its operating speed can be freely changed by the operator's intention, and when switching from the neutral position to the descending fully open position, the hydraulic oil passing through the hydraulic motor 11 is changed. It takes time for the flow rate to reach the target value. The flow rate control valve 15 always controls the sum of the flow rate QM of the hydraulic oil passing through the hydraulic motor 11 and the flow rate Qc passing through the bypass 13 to be constant.
The descending speed of becomes constant.

(D) The flow control valve 15 is moved by the piston (spool 20) moved by the opposition of the pressure of the hydraulic oil in the bypass 13 or the downstream pressure of the hydraulic motor 11 and the biasing force of the coil spring 33. The flow rate of the passage 19 communicating with the hydraulic oil tank 6 is adjusted. Therefore, the structure is simple.

(E) Hydraulic motor 11 and flow control valve 1
Since 5 is provided in the circuit dedicated to lowering, that is, the return circuit, unlike the configuration in which the discharge oil of the lift cylinder 2 is supplied to the hydraulic pump 7 for supplying hydraulic oil and the electric motor is used as a generator, It becomes possible to perform the tilt motion at the same time during the operation.

(F) The control device 14 judges whether the electric power generated by the generator 12 can be regenerated to the battery E,
Since the terminal of the generator 12 is switched to the state of being electrically connected to the battery E when regenerating is possible, there is no fear that the electric power of the battery E will be used by the generator 12 in a state where regeneration is impossible.

(Second Embodiment) Next, a second embodiment will be described with reference to FIGS. This embodiment differs from the above-mentioned embodiments in that a separately excited generator is used as the generator 12 and the regenerative effect is improved by performing field control. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

FIG. 7 is a block diagram corresponding to FIG. However, the lift cylinder 2 side of the lift control valve 4 and the hydraulic oil supply portion such as the hydraulic oil supply conduit 9 are not shown. As shown in FIG. 7, a rotation sensor 34 that detects the rotation speed of the generator 12 is provided, and the rotation sensor 34 outputs the detection signal to the control device 14. The control device 14 determines whether the rotation speed of the generator 12 has reached a predetermined value based on the output signal of the rotation sensor 34. And the control device 1
4 controls the exciting current value (field current value) flowing through the exciting winding 12f of the generator 12 so that the rotating speed becomes a constant value after the rotating speed of the generator 12 reaches a predetermined value. Specifically, control is performed by changing the resistance value of the field resistor 35 (illustrated in FIG. 6) which is a variable resistor connected to the field circuit.

As shown in FIG. 5, electric power is generated based on the flow rate QM of the hydraulic oil (return oil) discharged from the lift control valve 4 that passes through the hydraulic motor 11. Then, when the entire amount of the return oil passes through the hydraulic motor 11, that is, in FIG.
In the operating state (B), the rotation speed becomes constant because the hydraulic motor 11 has a fixed capacity. As a result, the amount of regenerative current does not change as the load increases or decreases. In the first embodiment, when the pressure P1 of the hydraulic oil discharged from the lift control valve 4 reaches the pressure corresponding to the operating state (B), the pressure P
With the increase of 1, the third orifice 31 is throttled and the flow rate QM
Was controlled so that the flow rate would be constant. As a result, part of the energy that can be used for power generation is absorbed by the third orifice 31, and the energy of the return oil has not been fully utilized.

In this embodiment, the control device 14 changes the excitation current (field current) from the time when the rotation speed of the generator 12 reaches the rotation speed corresponding to the state where the flow rate QM becomes the total amount of the return oil. Start control. Then, the field current value is increased to the maximum while the rotation speed does not fall below the set value. Generator 1
The induced electromotive force of No. 2 increases with an increase in the field current value if the rotation speed is constant. Therefore, in this embodiment,
By increasing the field current value, optimum power regeneration according to the energy of the return oil becomes possible. In addition, this embodiment also has the effects (a) to (f) of the above embodiment.

(Third Embodiment) Next, a third embodiment will be described with reference to FIGS. In both of the above-described embodiments, good power regeneration can be performed when the descending speed of the fork is high (the lift control valve 4 is fully opened), whereas in this embodiment, the medium speed region (for lift) is used. Control valve 4
The state that the electric power can be regenerated even in the state where the flow path is narrowed) is greatly different. Specifically, as shown in FIG. 9, in the hydraulic circuits of the first and second embodiments, the logic valve 3 is provided between the first port C1 and the flow control valve 15.
6, a switching valve 37 for assisting the operation of the logic valve 36
The difference is that. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIGS. 10 to 14, the valve unit is constructed by integrally incorporating the logic valve 36 and the switching valve 37 in the housing 16 in which the flow control valve 15 is provided. The passage 17 that can communicate with the first orifice 28
A logic valve 36 is provided midway. The plunger 38 forming the logic valve 36 has a tip end side (see FIG. 10).
On the left side), the fourth orifice 39 and the passage 4 that regulate the flow rate of the hydraulic oil toward the first orifice 28 via the passage 17 are provided.
0 is formed. The passage 40 is formed by holes that extend in a direction orthogonal to the moving direction of the plunger 38 and are orthogonal to each other. The fourth orifice 39 is formed at the axial center of the plunger 38 so as to communicate with the passage 40.

A spring chamber 41 open to the base end side is formed in the plunger 38, and a coil spring 42 as an urging means arranged in the spring chamber 41 acts so that the tip end side of the plunger 38 is not operated. The wall 43, which is provided in the middle of the passage 17 and partitions the chamber 17a in the vicinity of the first port C1, abuts. The plunger 38 comes into contact with the wall 43 in a state where the tip of the plunger 38 enters the hole 43a. When the plunger 38 is in contact with the wall 43, the flow rate of the hydraulic oil introduced from the first port C1 is regulated to the amount passing through the fourth orifice 39. Further, the plunger 38 is formed with a fifth orifice 44 which connects the spring chamber 41 and the end of the passage 40.

The spool 45 constituting the switching valve 37 corresponds to a chamber 47 whose first end (the left side in FIG. 10) communicates with a fifth port C which is connected to the bottom chamber 2a via a pipe line 46. The second end is slidably arranged in correspondence with a chamber 49 communicating with a sixth port T2 connected to the hydraulic oil tank 6 via a pipe line 48. The spool 45 is installed in the chamber 49 by a coil spring 50 as a biasing means.
The retaining ring 51, which is biased to the side and fixed to the second end portion side, comes into contact with the end surface of the chamber 49, whereby the retaining ring 51 is arranged at the predetermined non-operating position shown in FIG.

An annular recess 45a is formed in the spool 45. The annular recess 45a has the spool 45 shown in FIG.
When placed in the actuated position shown at 14, the logic valve 36
The port 52a communicating with the spring chamber 41 and the port 52b communicating with the first port C1 are formed at a position (in this embodiment, substantially in the center of the spool 45). At the center of the spool 45, the spool 4
A passage 53 that opens to the end surface of the No. 5 on the second end side is formed. A damper orifice 54 is formed near the first end of the spool 45. The damper orifice 54 connects the passage 53 and the annular chamber 55 formed on the first end side of the annular recess 45a. That is, the spool 45 is moved by the opposition of the pressure (hereinafter, bottom pressure) Pb of the working oil in the bottom chamber 2a and the biasing force (hereinafter, switching valve working pressure) Psw of the coil spring 50, and Pb> P
When sw, the spool 45 is arranged in the operating position.

As shown in FIG. 9, the lift control valve 4 has a stroke sensor 5 for detecting the operation amount of the lift lever 5.
6 is provided. The control device 14 determines from the output signal of the stroke sensor 56 whether or not regeneration of the fork 1 at the lowering speed of the fork 1 is possible, and changes the target rotational speed of the generator 12 between the middle speed region and the high speed region. It is like this.

Next, the operation of the apparatus configured as described above will be described. When the bottom pressure Pb is smaller than the switching valve operating pressure Psw, the spool 45 of the switching valve 37 is arranged as shown in FIGS.
It is held in the non-actuated position shown in. And the hydraulic motor 1
1 does not work, the bottom chamber 2 when the fork 1 descends
When the hydraulic oil discharged from a flows into the first port C1 via the lift control valve 4, the plunger 38 of the logic valve 36 is moved to the open position against the biasing force of the coil spring 42, and FIG. The state becomes as shown in. In this state, the fourth orifice 39 does not function and the first port C
The hydraulic oil flowing into No. 1 is guided to the flow control valve 15 via the passage 17 without resistance. Therefore, the same working effects as when the entire hydraulic oil of the first embodiment passes through the bypass 13 are exhibited.

When the bottom pressure Pb is lower than the switching valve operating pressure Psw and the hydraulic motor 11 operates, the spool 45 of the switching valve 37 is held in the non-operating position shown in FIGS. In this case, a part of the hydraulic oil flows through the hydraulic motor 11, then flows into the flow control valve 15, joins the hydraulic oil that does not pass through the hydraulic motor 11, and is discharged to the hydraulic oil tank 6. , All hydraulic motor 11
In some cases, it may flow into the flow control valve 15 via the above and may be discharged to the hydraulic oil tank 6. When a part of the hydraulic oil flows into the flow control valve 15 after passing through the hydraulic motor 11,
The same operational effect as in the case of the same state of the first embodiment is exhibited. Further, when the whole amount flows into the flow rate control valve 15 via the hydraulic motor 11 and then is discharged to the hydraulic oil tank 6, Qc = QM, so that the plunger 38 of the logic valve 36 is initially set as shown in FIG. Return to position. In this state, the same operational effect as in the case where the entire amount of hydraulic oil passes through the hydraulic motor 11 in the second embodiment is exhibited.

When the bottom pressure Pb is larger than the switching valve operating pressure Psw, the pressure Pb acting on the fifth port C overcomes the switching valve operating pressure Psw and the spool 45 of the switching valve 37.
Is moved to the operating position shown in FIGS. As a result, the spring chamber 41 of the logic valve 36 is kept in communication with the chamber 17a near the first port C1, and the plunger 38 of the logic valve 36 is always kept in the non-actuated position as shown in FIG. Only the orifice 39 serves as a passage to the first orifice 28 of the flow control valve 15.

The flow control valve 15 alone and the fourth orifice 3
The flow rate characteristic of No. 9 is as shown in (1) and (2) in FIG. Since the fourth orifice 39 and the flow rate control valve 15 are arranged in series, the flow rate characteristics of the both are shown in FIG.
It becomes (3) in 5 (c). Therefore, the characteristic of the flow rate Q of the hydraulic oil discharged from the lift control valve 4 is Pb <P
In the sw state, that is, in the state where the plunger 38 of the logic valve 36 is placed in the operating position and the fourth orifice 39 does not function, the characteristic (1) is exhibited. In addition, the state of Pb> Psw,
That is, in the state where the plunger 38 of the logic valve 36 is placed in the non-actuated position and the fourth orifice 39 functions,
The characteristic of (3) is shown.

If the lowering operation of the fork 1 is performed with the lift control valve 4 not fully opened but in a throttled state, the hydraulic motor 1
1 and the flow rate of the return oil supplied to the bypass 13 are below the target lowering speed equivalent amount QA. The pressure of the hydraulic oil is also lower than the bottom pressure Pb. In this state, if the fourth orifice 39 does not exist in the middle of the passage 17 as in the first and second embodiments, the flow rate Qc flowing into the flow rate control valve 15 without passing through the hydraulic motor 11 increases. The flow rate QM flowing into the flow rate control valve 15 after passing through the hydraulic motor 11 is reduced. As a result, almost no cargo handling regeneration is performed in the medium speed range.

However, by providing the fourth orifice 39 and limiting the flow rate Qc flowing into the flow rate control valve 15 without passing through the hydraulic motor 11, the relationship between the flow rate Qc and the pressure is shown in FIG. The state shown in 4) is obtained. as a result,
Even when the lift control valve 4 is not fully opened and is lowered in the medium speed range, the cargo handling regeneration is possible when the bottom pressure Pb> the switching valve operating pressure Psw. In FIG. 15 (c), the shaded area shows the cargo handling regeneration in the middle speed range when the fork 1 is descending.

As shown in FIG. 8, the proper field current value when performing field control differs depending on the opening degree of the lift control valve 4. The control device 14 determines the opening (throttle state) of the lift control valve 4 based on the output signal from the stroke sensor 56, and controls the field current value to be an appropriate value according to the opening. To do.

When the bottom pressure Pb is larger than the switching valve operating pressure Psw and the first orifice 28 of the flow control valve 15 is completely closed as shown in FIG. 14, the operation discharged from the lift control valve 4 is performed. The entire amount of oil flows into the flow control valve 15 via the hydraulic motor 11. That is, the flow rate QM =
Q and Qc = 0. At this time, the lift lever 5
Is fully open, the flow rate Q is equal to the target descending speed QA.
Is adjusted by the third orifice 31 to be equal to.
Then, the field control of the generator 12 is performed in the same manner as in the second embodiment, and the field current value is increased,
Optimal power regeneration according to the energy of the return oil is possible.

In the first and second embodiments in which the logic valve 36 is not provided, the relationship between the operation amount St of the lift lever 5 and the flow rate Q of the hydraulic oil passing through the lift control valve 4 is shown in FIG.
5 (a). That is, as the load (sum of the weight of the fork 1 and the load) increases, the flow rate Q with respect to the operation amount St
The rate of increase will increase. Then, in the vicinity of the maximum load, the increasing rate becomes sharp.

On the other hand, in this embodiment in which the logic valve 36 is provided, the relationship between the operation amount St of the lift lever 5 and the flow rate Q of the hydraulic oil passing through the lift control valve 4 is shown in FIG.
As shown in (b). That is, the portion surrounded by the chain line and the solid line (hatched portion) in FIG. 15B disappears, and the increase rate of the flow rate Q with respect to the manipulated variable St becomes small even at the maximum load. Therefore, the provision of the logic valve 36 reduces the rate of change in the flow rate Q of the hydraulic oil passing through the lift control valve 4 with respect to the operation amount St of the lift lever 5. As a result, the inching property (fine operability) is improved.

(Fourth Embodiment) Next, a fourth embodiment will be described with reference to FIGS. In this embodiment, the configurations of the logic valve 36 and the switching valve 37 are different from those in the third embodiment. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals and detailed description thereof will be omitted. Note that the hydraulic circuit in FIG. 16 shows only the path of return oil from the lift cylinder 2.

As shown in FIG. 17, the plunger 38 of the logic valve 36 is arranged so as to be movable in a direction orthogonal to the moving direction of the piston 20 of the flow control valve 15. At the tip of the plunger 38, a passage 57 opened to the tip side is provided.
And a fourth orifice 39 communicating with the passage 57 is formed. The fourth orifice 39 is a hole formed so as to extend in a direction orthogonal to the moving direction of the plunger 38. Plunger 38 on housing 16
An annular recess 58 is formed at a position corresponding to the peripheral surface of the. An annular groove 59 is formed on the peripheral surface of the plunger 38 so as to communicate with the recess 58. Also, the plunger 3
8 is a hole 60 that connects the spring chamber 41 and the groove 59.
Are formed.

The spool 45 of the switching valve 37 is the plunger 3
It is provided in parallel with 8. A hole 61 communicating with the passage 53 is formed substantially in the center of the spool 45, and an annular groove 45b is formed on the outer peripheral surface corresponding to the end of the hole 61.
Are formed. A passage 62 is formed in the housing 16 to connect the groove 45b and the recess 58 with each other when the spool 45 is arranged in the non-actuated position shown in FIG. Therefore, the spring chamber 41 of the logic valve 36 is provided with the passage 62 and the switching valve 37 when the switching valve 37 is in the non-operating state.
The hydraulic oil tank 6 is held in communication with the hydraulic oil tank 6 via the valve, and the communication with the hydraulic oil tank 6 is cut off when the switching valve 37 is operating.

Therefore, in this embodiment, the bottom pressure P
When b is smaller than the switching valve operating pressure Psw, the switching valve 37
Holds the spool 45 in the non-actuated position shown in FIGS. When the hydraulic motor 11 does not operate,
When the working oil discharged from the bottom chamber 2a flows into the first port C1 via the lift control valve 4 when the fork 1 descends, the pressure in the spring chamber 41 is almost equal to the working oil tank 6.
Is equal to the pressure of
Is moved to the open position against the biasing force of the coil spring 42,
It will be in the state shown in FIG. In this state, the fourth orifice 39 is in a non-functioning state, and the working oil flowing into the first port C1 passes through the passage 17 without resistance and flows into the flow control valve 15
Be led to. Therefore, the same working effects as when the entire hydraulic oil of the first embodiment passes through the bypass 13 are exhibited.

Even when the bottom pressure Pb is lower than the switching valve operating pressure Psw and the hydraulic motor 11 operates, the spool 45 is held in the non-operating position and the plunger 38 is held in the open position. Then, the generator 12 is operated together with the hydraulic motor 11, and the electric power generated by the generator 12 is regenerated in the battery E. When the entire amount of the return oil passes through the hydraulic motor 11, the flow control valve 15 is in a state where the first orifice 28 is completely closed as shown in FIG. Then, the field control is performed by the control device 14, and the same operational effect as in the case where the entire amount of hydraulic oil passes through the hydraulic motor 11 in the second embodiment is exerted.

When the bottom pressure Pb is larger than the switching valve operating pressure Psw, the pressure Pb acting on the fifth port C overcomes the switching valve operating pressure Psw, and the spool 45 moves to the positions shown in FIGS.
1 is moved to the operating position. As a result, the communication state between the spring chamber 41 of the logic valve 36 and the sixth port T2 is blocked, and the pressure in the spring chamber 41 increases via the fifth orifice 44. Then, the plunger 38 returns to the closed position as shown in FIG. 20, and the fourth orifice 39
Only the passage serves as a passage to the flow rate control valve 15 for the return oil that does not pass through the hydraulic motor 11. In this state, when the fork 1 is moved downward while the lift control valve 4 is not fully opened but in a throttled state, the cargo handling regeneration in the medium speed range is performed as in the third embodiment. .

When the bottom pressure Pb is higher than the switching valve operating pressure Psw and the first orifice 28 of the flow control valve 15 is completely closed as shown in FIG. 21, the operation discharged from the lift control valve 4 is performed. The entire amount of oil flows into the flow control valve 15 via the hydraulic motor 11. Then, similarly to the third embodiment, the field control of the generator 12 is performed, and when the amount of hydraulic oil flowing into the hydraulic motor 11 is equal to or larger than the predetermined amount, the rotation speed of the hydraulic motor 11 becomes the predetermined rotation speed. By thus controlling the field current value, it is possible to optimally regenerate the electric power according to the energy of the return oil.

In this embodiment, the logic valve 36
And the configuration of the switching valve 37 is different from that of the third embodiment,
It has the same effect as that of the third embodiment. (Fifth Embodiment) Next, a fifth embodiment will be described with reference to FIGS.
This will be described with reference to FIG. In this embodiment, FIG.
As shown in FIG. 3, the bypass line 13 branched from the return line 10 on the upstream side of the hydraulic motor 11 is joined on the downstream side of the hydraulic motor 11, and the flow control valve 63 is provided in the middle of the bypass line 13. This is different from the second embodiment. The same parts as those in the second embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 23 (a), the flow control valve 6
First to fourth ports C1, M1, M2, T are formed in the housing 16 forming the third valve 3 so as to communicate with the housing portion 65 of the piston 64 forming the spool valve. The first port C1 and the second port M1 are formed in the same plane, and the third port M2 and the fourth port T are formed in the same plane parallel to the plane. ing. The third port M2 and the fourth port T are arranged at opposite positions. The first port C1 is formed so as to be orthogonal to the second port M1. The first port C1 and the second port M1 are shown in FIG.
It is formed so as to be located on the front side of the paper surface with respect to the cross section shown in (b) and FIG. The first port C1 is shown in FIG.
It is formed so as to extend in a direction orthogonal to the paper surface of FIGS.

At the center of the piston 64, a stepped passage 66 having an opening is formed at the end face on the first end side (right side in FIG. 23A). The passage 66 has a large diameter on the first end side, and a spring 67 for urging the piston 64 toward the second end is housed in the large diameter portion of the passage 66. A passage 66 is provided in the piston 64 for the third and fourth ports M2, T.
A passage 68 is formed to communicate with. In the passage 68, the rate at which the opening of the passage 68 is covered by the wall surface of the accommodating portion 65 changes as the piston 64 moves, and the first end portion of the piston 64 resists the biasing force of the spring 67 as shown in FIG. Is formed in a position where it is completely closed when it contacts the housing 16.

The second port M1 is connected through the orifice 70 in the middle of the communication passage 69 for guiding the hydraulic oil flowing from the first port C1 to the passage 66. In the piston 64, the passage 66 and the communication passage 69 are provided at positions corresponding to the communication passage 69.
A passage 71 is formed to communicate with and. A plurality of passages 71 (four in this embodiment) are formed.

A chamber 72 is formed on the side of the second end of the piston 64, and a passage 73 for communicating the chamber 72 with the communication passage 69 is formed. The piston 64 has a smaller diameter on the first end side than the position corresponding to the passage 71 and on the second end side from the position corresponding to the chamber 72. The chamber 72 is located at a position corresponding to the chamber 72 of the piston 64, and the chamber 72 is located on the second end side of the accommodating portion 65 via the damper orifice 74.
Is in communication with. A chamber 7 is provided on the second end side of the piston 64.
A passage 76 that connects the chamber 5 and the chamber 72 is formed. The passage 76 is formed in a stepped shape, and a check valve 77 that allows passage of hydraulic oil to the chamber 72 side is provided on the small diameter portion side of the passage 76. As shown in FIG. 23 (b),
The check valve 77 includes a ball 78 having a diameter larger than that of the small diameter portion of the passage 76 and smaller than that of the large diameter portion, and a spring 79 for biasing the ball 78 toward the closing side.

The position of the piston 64 is changed by the balance between the pressure of the hydraulic oil in the chamber 75 and the urging force of the spring 67, and the opening of the passage 68 is adjusted. Then, the opening degree of the passage 68 becomes maximum when the hydraulic oil does not flow through the hydraulic motor 11, and becomes smaller as the flow rate of the hydraulic oil flowing through the hydraulic motor 11 increases, and the flow rate of the hydraulic oil passing through the hydraulic motor 11 becomes light. The spring force of the spring 67 and the shape of the passage 68 are set so as to be zero, that is, a fully closed state at a flow rate equal to or higher than the target lowering speed of the fork 1 under load. Further, when the opening degree of the passage 68 is between fully open and fully closed, the sum of the flow rate of the hydraulic oil passing through the passage 68 and the flow rate of the hydraulic oil passing through the hydraulic motor 11 becomes the target lowering speed equivalent amount. Is set. That is, the flow rate control valve 63 has a flow rate characteristic that is equal to the flow rate of the hydraulic motor 11 alone.
Fork 1 when the sum of the flow rate of flow rate control valve 63 and the load is light
It is configured so that the flow rate is equivalent to the target descending speed of.

In this flow control valve 63, the first port C
The hydraulic oil flowing from 1 passes through the communication passage 69 and the piston 64.
It reaches a position corresponding to and moves through the passage 71 into the passage 66. The hydraulic oil that has moved into the passage 66 passes through the passage 68, reaches the fourth port T, and returns to the hydraulic oil tank 6 via the return pipe 10. Further, a part of the hydraulic oil that has flowed into the communication passage 69 reaches the second port M1 via the orifice 70.

A part of the hydraulic oil in the communication passage 69 is introduced into the chamber 72 via the passage 73 and is introduced into the chamber 75 via the damper orifice 74. The position of the piston 64 is determined by the balance between the pressure of the hydraulic oil in the chamber 75 and the urging force of the spring 67. Further, since the check valve 77 is present, if the pressure in the chamber 72 decreases as the pressure in the communication passage 69 decreases, the check valve 77
Is opened and the pressure in the chamber 75 becomes the same as the pressure in the chamber 72. As a result, when the pressure of the hydraulic oil flowing from the first port C1 becomes low, the piston 64 moves in the direction in which the opening of the passage 68 increases without delay.

In this embodiment, when the pressure of the return oil is low and the hydraulic motor 11 cannot be driven under a light load, the return oil passes through the passage 66 of the flow control valve 63 of the bypass 13.
It passes through 68 and is discharged to the hydraulic oil tank 6. When the load weight increases and the hydraulic oil reaches a predetermined pressure, the hydraulic motor 1
1 is driven, and the flow rate of the hydraulic motor 11 increases as the pressure increases. As the flow rate of the hydraulic motor 11 increases, the passage 68 of the flow control valve 63 is throttled and the flow rate of the hydraulic oil flowing through the passage 68 decreases. At this time, the hydraulic motor 11
And the flow rate of the detour 13, that is, the flow rate flowing through the passage 68, is the same as the flow rate corresponding to the maximum lowering speed (target lowering speed) of the fork 1 under light load.

When the load further increases and the flow rate of the hydraulic oil passing through the hydraulic motor 11 reaches the flow rate Qa corresponding to the target lowering speed, the flow control valve 63 is fully closed and the return oil discharged from the lift cylinder 2 is reached. Flow through hydraulic motor 11. When the load becomes higher than that, the field control of the generator 12 directly connected to the hydraulic motor 11 is performed as in the second embodiment. Then, the rotation sensor 34 detects the rotation speed of the generator 12, and the exciting current is controlled by the controller 14 so that the rotation speed becomes constant at a predetermined rotation speed corresponding to the target descending speed. As a result, after the flow rate control valve 63 is fully closed, the discharge flow rate from the lift cylinder 2 is kept constant even if the load further increases.

Therefore, when the lift control valve 4 is fully opened, the flow rate of the hydraulic oil flowing through the hydraulic motor 11, the flow rate through the flow rate control valve 63, and the combined flow rate (total flow rate) and pressure of the two flow rates are 25 (a), (b), and (c), respectively.
The total flow rate is always constant until the full load FL is reached. Therefore, also in this embodiment, the same effect as that of the second embodiment is obtained.

(Sixth Embodiment) Next, a sixth embodiment will be described with reference to FIGS. In this embodiment, as shown in FIG. 26, the second side is located downstream of the confluence of the bypass 13 and the return pipe 10 downstream of the hydraulic motor 11.
The point that the flow control valve 80 is provided is different from the fifth embodiment. The same parts as those in the fifth embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 27, the second flow control valve 8
Zero is integrated in the same housing 16 as the flow control valve 63. A passage 81 is formed in the housing 16 in parallel with the accommodating portion 65 of the piston 64, and the second flow control valve 80 is fixed so as to close the opening end of the passage 81.
A fourth port T is formed in the housing 16 at a position corresponding to the second flow control valve 80. The passage 81 communicates with the housing portion 65 via the passage 82. The second flow rate control valve 80 has a housing 83 formed in a bottomed cylindrical shape, and a spool 84 is accommodated in the housing 83. The spool 84 uses the spring 85 for the housing 8
3, the movement is regulated by the orifice plate 86 fixed to the opening side while being biased toward the opening side. A recess 84a is formed at the tip of the spool 84, and an annular recess 87 is formed on the outer periphery near the tip. A plurality of holes 88 are formed in the spool 84 at positions corresponding to the annular recess 87. Further, the valve 89 is accommodated in the recess 84a in a state of being biased toward the orifice plate 86 by the spring 90. Even when the valve 89 is in contact with the orifice plate 86, the valve does not completely close the orifice, and the working oil can gradually move between the passage 81 and the recess 84a.

Holes 91 and 92 are formed in the housing 83 at positions corresponding to the annular recess 87 of the spool 84 and at positions corresponding to the fourth port T. The hole 91 is always formed in a position corresponding to the annular recess 87 regardless of the position of the spool 84. The hole 92 is in a fully open state when the spool 84 is arranged at a position where it abuts against the orifice plate 86 by the biasing force of the spring 85, and the spool 84 moves to the spool 84 as the spool 84 moves against the biasing force of the spring 85. The area to be blocked increases. The spring 85 has a spring force that allows the spool 84 to move when the flow rate of the hydraulic oil flowing through the second flow rate control valve 80 exceeds the maximum flow rate at light load, and the maximum flow rate at light load is maintained. It is formed such that the throttling function is exerted by exceeding the pressure so that the maximum flow rate corresponds to the target lowering speed.

In the fifth embodiment, all the return oil discharged from the lift cylinder 2 passes through the hydraulic motor 11,
When the load exceeds a predetermined value, the generator 12
The field control is performed so that the flow rate becomes a predetermined amount. Therefore, when the field control cannot be performed, for example, when the power is off, the flow rate cannot be controlled to a predetermined amount. However, there are many occasions when the power is off (key off) to unload the load, and it is desirable that the maximum lowering speed can be kept constant even if the lift lever 5 is fully opened and lowered in such a state.

In this embodiment, when the flow rate of the working oil flowing into the passage 81 is equal to or less than the target lowering speed corresponding to the light load, the second flow rate control valve 80 allows the working oil to pass freely. Therefore, when the power is on and the flow control valve 63 is not in failure, the same operational effect as the fifth embodiment is exhibited.

On the other hand, the power is off or the flow control valve 6
If 3 is a failure and the amount of hydraulic oil discharged from the lift cylinder 2 is about to exceed the target lowering speed equivalent amount, the second flow rate control valve 80 exerts a throttling function to bring the maximum flow rate to the target lowering speed equivalent amount. Control so that it becomes the amount. As a result, even when the lift lever 5 is fully opened to lower the load under heavy load in the state where the field control cannot be performed, the maximum lowering speed is controlled to be the target lowering speed. Even if the flow control valve 63 fails, the maximum lowering speed is controlled so as not to exceed the target lowering speed.

The embodiment is not limited to the above, and may be embodied as follows, for example. The target lowering speed does not necessarily have to be the maximum lowering speed in the unloaded state, and may be the maximum lowering speed in the lightly loaded state.

The logic valve 36, the switching valve 37, the second flow rate control valve 80, etc., which are provided in addition to the flow rate control valves 15 and 63, are not integrated into the single housing 16 together with the flow rate control valves 15 and 63. Alternatively, the individual valves may be connected by a pipeline.

The fourth orifice 39 may be omitted in the third embodiment, and the fourth orifice 39 and the passage 57 may be omitted in the fourth embodiment. In this case, all the return oil passes through the hydraulic motor 11 when the logic valve 36 is placed in the non-actuated position.

When performing the field control in the second to sixth embodiments, the flow rate of the hydraulic oil flowing through the hydraulic motor 11 is changed in place of the configuration in which the rotation speed of the generator 12 is controlled to be a predetermined rotation speed. The configuration is such that control is performed so that the target descent speed is equivalent. In this case, instead of providing the rotation sensor 34, a flow meter as a flow rate detecting means for measuring the flow rate of the hydraulic oil flowing through the hydraulic motor 11 is provided. Then, the control device 14 inputs the detection signal of the flow meter and controls the field current so that the detected flow rate of the flow meter becomes a predetermined value. The flow meter is arranged between the downstream side of the hydraulic motor 11 and the third port M2 of the housing 16. Also in this case,
Optimal power regeneration according to the energy of the return oil is possible.

Not limited to forklifts, the invention may be applied to a hydraulic system for industrial vehicles such as an aerial work vehicle and a shovel loader that use a battery as a power source. Technical ideas (inventions) other than the claims that can be understood from the respective embodiments will be described below along with their effects.

(1) In the invention described in claim 7,
The separately excited type generator is used as the generator, and the control means for controlling the field of the generator is based on the output signal of the detection means for detecting the opening degree of the lift control valve. The target rotation speed of the generator is changed between the high speed range and the high speed range. In this case, electric power can be efficiently regenerated even in the medium speed range.

(2) Claims 2, 3, 6, 7 and (1)
In any one of the inventions, the control means for performing field control of the generator, instead of controlling the field current so that the number of revolutions of the generator becomes the target number of revolutions, a flow rate detecting means for detecting the flow rate of the hydraulic motor. Based on the detection signal of, the field current is controlled so that the detection signal has a value corresponding to the target flow rate. In this case as well, the same effects as those of the corresponding inventions are exhibited.

The "light load" in this specification means
It means a state in which the cargo handling member does not hold a load and a state in which the load is light and the pressure of the hydraulic oil is smaller than the pressure required to operate the hydraulic motor even when the lift control valve is fully opened and lowered. Also, the "cargo handling member" does not mean only an attachment such as a fork of a forklift, but a hydraulic cylinder when a load (including a worker) such as a platform of an aerial work platform or an excavator of an excavator loader is loaded. Includes those that are moved to low and high positions.

[0102]

As described in detail above, the first to seventh aspects of the invention are described.
According to the invention described in (1), it is possible to secure the descending speed at the time of a light load, and it is possible to obtain regenerative power at a predetermined load or more.

According to the second and sixth aspects of the present invention, the field control is performed in the state where the load is large, so that optimum power regeneration according to the energy of the return oil becomes possible.

According to the third aspect of the present invention, the descending speed of the cargo handling member can be maintained at the target speed even when the field control is impossible under heavy load. According to the invention of claim 4, since the flow rate control valve gives priority to the flow rate of the hydraulic motor,
When the amount of hydraulic oil discharged from the lift control valve is large, a large amount of hydraulic oil flows to the hydraulic motor side, and the energy of the hydraulic oil can be effectively converted into electric power.

According to the invention described in claim 5, the structure of the flow control valve is simplified. According to the invention described in claim 7, it is possible to regenerate electric power in the medium speed range.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a sectional view of a flow control valve.

FIG. 3 is a partial cross-sectional view showing the action of the flow control valve.

FIG. 4 is a partial cross-sectional view showing the action of the flow control valve.

FIG. 5 is a graph showing the action of the flow control valve.

FIG. 6 is an electric circuit diagram.

FIG. 7 is a configuration diagram of main parts of the second embodiment.

FIG. 8 is a graph showing the relationship between the field current and the opening degree of the lift control valve.

FIG. 9 is a configuration diagram of a third embodiment.

10A is a sectional view of a valve unit, FIG.
Is a partially enlarged view of (a).

FIG. 11 is a sectional view of the valve unit showing the operation.

FIG. 12 is a sectional view of the valve unit showing the operation.

FIG. 13 is a sectional view of the valve unit showing the operation.

FIG. 14 is a sectional view of the valve unit showing the operation.

15A and 15B are graphs showing the relationship between the operation amount of the lift lever and the hydraulic oil flow rate, and FIG. 15C is a graph showing the action of the flow control valve.

FIG. 16 is a hydraulic circuit diagram of the fourth embodiment.

FIG. 17 (a) is a cross-sectional view of a valve unit, (b).
Is a partially enlarged view of (a).

FIG. 18 is a sectional view of the valve unit showing the operation.

FIG. 19 is a sectional view of the valve unit showing the operation.

FIG. 20 is a sectional view of the valve unit showing the operation.

FIG. 21 is a sectional view of the valve unit showing the operation.

FIG. 22 is a configuration diagram of the fifth embodiment.

23A is a sectional view of the flow control valve, and FIG. 23B is a partially enlarged view of FIG.

FIG. 24 is a sectional view showing the operation of the flow control valve.

FIG. 25 is a graph showing the characteristics of the flow control valve.

FIG. 26 is a configuration diagram of a sixth embodiment.

FIG. 27 is a sectional view of the valve unit.

FIG. 28 is a hydraulic circuit diagram of the related art.

[Explanation of symbols]

1 ... Fork as cargo handling member, 2 ... Lift cylinder,
2a ... bottom chamber, 4 ... lift control valve, 6 ... hydraulic oil tank, 7 ... hydraulic pump, 8 ... motor, 10 ... return line, 1
DESCRIPTION OF SYMBOLS 1 ... Hydraulic motor, 12 ... Generator, 13 ... Detour, 14 ...
Control device as control means, 15, 63 ... Flow control valve,
20 ... Piston as spool, 33 ... Coil spring as biasing means, 36 ... Logic valve, 37 ... Switching valve, 8
0 ... Second flow control valve, E ... Battery as battery power source.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeto Nakajima 1671 Asano, Toyono-cho, Kamimizunai-gun, Nagano Nishina Kogyo Co., Ltd. (56) Reference JP-A-55-56999 (JP, A) JP-A-1 -93601 (JP, A) JP-A-2-163300 (JP, A) Actual development 7-35499 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B66F 9/22 B66F 9/24

Claims (7)

(57) [Claims] 1. A lift cylinder for raising and lowering a cargo handling member, a battery power supply, a hydraulic pump driven by a motor driven by the battery power supply to supply hydraulic oil to the lift cylinder, the lift cylinder and hydraulic pressure. A lift control valve that is interposed between the pump and a lift cylinder that expands and contracts by changing the position, and connects the lift control valve and the hydraulic oil tank to each other. A hydraulic system in a battery-powered industrial vehicle having a return line for returning the pressure oil of the above to the hydraulic oil tank, a hydraulic motor disposed in the return line, and a battery power source driven by the hydraulic motor. A generator that regenerates electric power and a branch from the return pipe on the upstream side of the hydraulic motor, and flow control along the way. And a flow path characteristic of the flow rate control valve is such that the sum of the flow rate of the hydraulic motor and the flow rate of the flow rate control valve is a flow rate corresponding to the target lowering speed of the cargo handling member at a light load. Hydraulic system for battery-powered industrial vehicles. 2. A separately-excited generator is used as the generator, and control means for controlling the field of the generator is provided.
The battery-operated industrial vehicle according to claim 1, wherein the control means performs field control so that the number of revolutions of the generator becomes a predetermined number of revolutions corresponding to the target lowering speed when all the return oil passes through the hydraulic motor. Hydraulic system. 3. The bypass flow is merged with a return pipe downstream of the hydraulic motor, and the set flow rate is set to the target lowering speed equivalent amount in a power-off state at the time of heavy load downstream from the merged point. The hydraulic system for a battery-powered industrial vehicle according to claim 2, further comprising a second flow control valve. 4. A lift cylinder for raising and lowering a cargo handling member, a battery power source, a hydraulic pump driven by a motor driven by the battery power source to supply hydraulic oil to the lift cylinder, the lift cylinder and hydraulic pressure. A lift control valve that is interposed between the pump and a lift cylinder that expands and contracts by changing the position, and connects the lift control valve and the hydraulic oil tank to each other. A hydraulic system in a battery-powered industrial vehicle having a return conduit for returning the pressurized oil of the above to the hydraulic oil tank, a hydraulic motor disposed in the return conduit, and a battery power source driven by the hydraulic motor. A generator that regenerates electric power and a branch from the return pipe on the upstream side of the hydraulic motor and the downstream side of the hydraulic motor. A bypass line is provided to join the return line and the bypass line, and the flow rate of the hydraulic motor is prioritized at the junction point of the return line and the bypass line, and the hydraulic motor passage flow rate and the bypass line flow rate corresponding to the change in the pressure of the bypass line. Is a hydraulic device in a battery-powered industrial vehicle provided with a flow rate control valve that controls the flow rate so that the sum of the above is constant. 5. The flow control valve includes a spool moved by the pressure of the hydraulic oil in the bypass or the pressure on the downstream side of the hydraulic motor and the pressure of the urging means, and the spool is operated by the operation of the spool. The hydraulic system for a battery-operated industrial vehicle according to claim 4, wherein the flow rate of a passage communicating with the hydraulic oil tank is adjustable. 6. A separately-excited generator is used as the generator, and control means for controlling the field of the generator is provided.
The control means performs the field control so that the rotation speed of the generator is a predetermined rotation speed corresponding to the target lowering speed of the cargo handling member when the load is light, when all the return oil passes through the hydraulic motor. Alternatively, the hydraulic device in the battery-powered industrial vehicle according to claim 5. 7. The bypass circuit includes a logic valve for changing a bypass flow characteristic of the flow control valve, and a communication position for operating the logic valve when the pressure in the bottom chamber of the lift cylinder is equal to or higher than a predetermined pressure. 7. The hydraulic device for a battery-operated industrial vehicle according to claim 4, further comprising: a switching valve that is disposed at a shutoff position when the pressure is less than a predetermined pressure.