JP2002068696A - Solenoid control valve for industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that the stable and quick operation of forks is prevented by a pressure loss occurring on the operating oil passing in a sequence valve or the lift descending speed is temporarily reduced during a lift descent state. SOLUTION: A lift cylinder control valve 5 and a tilt cylinder control valve 6 are provided in a bypass passage 3 to set the bypass passage 3 to a communication state at a neutral position. A primary pressure generating valve 16 is provided on the downstream side of the tilt cylinder control valve 6 and on the upstream side of a merge point 25 of a tank passage 8 and the bypass passage 3 to generate the primary pressure of the pilot pressure for controlling both control valves 5 and 6. No pressure loss is applied by the primary pressure generating valve 16 even when both control valves 5 and 6 are operated, and no operation delay occurs at an operation change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic control valve having a mechanism capable of stably generating a pilot pressure of an electromagnetic control valve for controlling various actuators in an industrial vehicle such as a battery forklift.

[0002]

2. Description of the Related Art Conventionally, an electro-hydraulic control battery forklift has been provided with an electromagnetic proportional control valve.
Up-down operation and tilt operation of the front fork are driven and controlled by hydraulic oil supplied by a battery-driven hydraulic motor.

FIG. 3 is a hydraulic circuit diagram showing an electromagnetic proportional control valve of this type of battery forklift. As shown in the figure, hydraulic oil in a tank 52 is supplied to the electromagnetic proportional control valve 70 by a hydraulic pump 51 to the primary side of a sequence valve 53. The primary side of the sequence valve 53 is connected in parallel with the primary side of a pressure reducing valve 54, and the secondary side is connected in series with a lift cylinder control valve 55 and a tilt cylinder control valve 56. An output from the lift cylinder control valve 55 drives a lift cylinder 57.
At 7, the fork of the forklift is raised or lowered. When ascending, the load 58 is pushed up by the hydraulic oil from the hydraulic pump 51, and when descending, the hydraulic oil in the lift cylinder 57 is discharged to the tank 52 by the own weight of the load 58. Control valve for tilt cylinder 5
6 drives the tilt cylinder 59, and the fork of the forklift is tilted upward or downward by the tilt cylinder 59. At tilt,
The hydraulic oil from the hydraulic pump 51 is supplied to one of the tilt cylinders 59, and the other oil is discharged to the tank 52. The lift cylinder control valve 55 and the tilt cylinder control valve 56 are configured to return the hydraulic oil from the hydraulic pump 51 to the tank 52 via the bypass passage 60 at the neutral position to unload the output. I have. The hydraulic pump 51 side of this bypass passage 60 is called a P port, and the tank 52 side is called a T port. Reference numeral 69 denotes a relief valve for preventing the output of the hydraulic pump 51 from becoming excessive.

A sequence valve 53 provided on the hydraulic pump 51 side of the lift cylinder control valve 55
The primary pressure of the pressure reducing valve 54 is secured by the pressure reducing valve 5.
The pilot pressure for operating the lift cylinder control valve 55 and the tilt cylinder control valve 56 as an electromagnetic proportional control valve is secured by the oil reduced to a constant pressure by the step 4. The lift cylinder control valve 55 is provided with electromagnetic proportional pressure reducing valves 61 and 62, and the electromagnetic proportional pressure reducing valve 61 and the electromagnetic proportional pressure reducing valve 62 are provided.
By exciting the respective coils, the main spool 65 for lift cylinder control is caused to stroke from the neutral position. When the coils of the electromagnetic proportional pressure reducing valves 61 and 62 are not excited, the lift cylinder main spool 65 blocks the lift cylinder port 66, and the lift cylinder 57 is held while the load 58 is held. The tilt cylinder control valve 56 includes an electromagnetic proportional pressure reducing valve 63,
When the coils of the electromagnetic proportional pressure reducing valve 63 and the electromagnetic proportional pressure reducing valve 64 are respectively excited, the tilt cylinder control main spool 67 is stroked from the neutral position, and hydraulic oil is supplied to the cylinder port 68. Is done.

As a prior art of this type, there is a device described in Japanese Utility Model Registration No. 2590030. In this device, it is not necessary to rotate the pump when the lift cylinder descends, or the load due to leakage from the clearance is reduced. It does not relate to a mechanism for generating a primary pressure of an electromagnetic proportional pressure-reducing valve as in the present invention, in order to prevent natural descent.

[0006]

However, in the case of the electromagnetic proportional control valve 70, the sequence valve 53 for securing the primary pressure of the electromagnetic proportional pressure reducing valves 61 to 64 is provided by the lift cylinder control valve 55 and the tilt cylinder control valve 55. Since it is provided on the bypass passage 60 on the upstream side of the valve 56, it has the following problems.

First, in the switching state of the control valves, the hydraulic oil flowing from the P port on the hydraulic pump 51 side receives the two control valves 5 through the sequence valve 53.
Since the pressure reaches the cylinder ports 66 and 68 of 5,56, a pressure loss occurs when passing through the sequence valve 53. Therefore, if there is no margin in the capacity of the motor driving the pump, the pump pressure rises due to this pressure loss, the motor speed decreases, and the specified pump discharge flow rate may not be obtained.
There is a case where a regular cylinder speed cannot be obtained.
Further, if the size of the electric motor is increased in order to avoid this problem, the electric motor becomes excessively expensive and extremely uneconomical.

FIGS. 4 (a), 4 (b) and 4 (c) show hydraulic circuit diagrams in a state where the electromagnetic proportional control valve for forklift of FIG. 3 is operated. In the case of the electromagnetic proportional control valve 70, when the lift is raised, the electromagnetic proportional pressure reducing valve 61 is operated, and the lift cylinder 5
7 to increase the load 58 (a). When the lift is lowered, the electromagnetic proportional pressure reducing valve 62 is operated to drain the pressurized oil of the lift cylinder 57 into the tank, thereby lowering the load (b). ). In any case, the hydraulic oil flowing from the P port passes through the lift valve 5
7 (a) or (b) to the tank 52, a pilot pressure required to drive the electromagnetic proportional pressure reducing valve is generated upstream of the sequence valve 53. However, considering a case in which the simultaneous operation of lift lowering and tilting shown in (c) is shifted to a single operation of lift lowering in (b), when the driving pressure of the tilt cylinder 59 is higher than the set pressure of the sequence valve 53, In the state (c), the sequence valve 53 is fully opened. When the tilt cylinder control valve 56 is returned to the neutral state from this state, an operation delay occurs when the sequence valve 53 returns from the fully open state to the pressure regulation state, and the bypass passage 60 from the pump 51 to the tank 52 is temporarily connected. State, and the primary pressure temporarily drops. Therefore, before the sequence valve 53 returns from the fully open state to the pressure regulation state, the primary pressure of the lift lowering pilot proportional valve also temporarily decreases, and the speed of the lift lowering temporarily decreases. Will occur. This breathing phenomenon may prevent stable and quick operation of the fork.

In order to avoid this problem, it is only necessary to reduce the fully-opened position of the sequence valve 53. However, if the fully-opened value is reduced, the above-described pressure loss increases.
Conversely, if the opening at full opening is increased to avoid pressure loss, the breathing phenomenon will increase, and there is an urgent need for an electromagnetic proportional control valve that can solve both problems.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides one or more control valves disposed on a bypass passage connecting a pump port and a tank port. And a pilot passage connected from the bypass passage on the upstream side of the first control valve to the primary side of the electromagnetic pilot valve for controlling each control valve. An actuator control device provided with a tank passage for connecting return oil from an actuator connected to a control port of each control valve to a downstream bypass passage of the last control valve, wherein a downstream bypass passage of the last control valve is provided. On the upstream side of the junction of the tank passage and the bypass passage, It is provided primary pressure generation valve for generating a primary pressure of the solenoid pilot valve for a control valve controlled on the upstream side by flowing. Thus, by providing the primary pressure generating valve downstream of the tilt cylinder control valve in the bypass passage and upstream of the junction of the tank passage and the bypass passage of each control valve, the operation of each control valve is controlled. Occasionally, it can be operated without receiving pressure loss from the primary pressure generating valve, and because the primary pressure for operating these control valves is generated downstream of each control valve, there is a delay in operation when changing the operation. It can be operated without.

If a pressure reducing valve is provided in the pilot passage and the primary pressure of an electromagnetic pilot valve for controlling each control valve is led from the secondary side of the pressure reducing valve, the pilot pressure of each control valve operates. Stable control can be performed without being affected by the pump port pressure that changes depending on the state.

Further, if the secondary pressure of the pressure reducing valve is guided to the spring chamber of the primary pressure generating valve, and the secondary pressure and the spring force are used to adjust the upstream pressure of the primary pressure generating valve, the relative pressure can be relatively reduced. With a small spring force, a primary pressure higher than the set pressure of the pressure reducing valve can be secured.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a hydraulic circuit diagram of an electromagnetic proportional control valve for a forklift showing one embodiment of the present invention.

As shown in the figure, hydraulic oil in a tank 2 is supplied to a bypass passage 3 from a P port by a hydraulic pump 1 to an electromagnetic proportional control valve 24. A lift cylinder control valve 5 and a tilt cylinder control valve 6 are connected in series to the bypass passage 3, and the pilot pressure of both control valves 5 and 6 is kept constant upstream of the lift cylinder control valve 5. The primary side of the pressure reducing valve 4 is connected. Further, a relief valve 7 is provided upstream of the lift cylinder control valve 5 to release hydraulic oil to the tank passage 8 when the pressure in the bypass passage 3 increases. In this embodiment, by providing the pressure reducing valve 4, the pilot pressure for operating the control valves 5 and 6 is stabilized.

Also, a control valve 5 for a lift cylinder is provided.
A parallel passage 26 branches from a branch point on the bypass passage 3 located upstream of the control valve 5. The parallel passage 26 passes through a check valve 29, an inlet port 27 of the lift cylinder control valve 5, and a tilt valve passes through the check valve 30. The inlet port 28 of the cylinder control valve 6 is connected.

The lift cylinder control valve 5 drives a lift cylinder 9, and the lift cylinder 9 raises or lowers the load 10 (fork's own weight, luggage, etc.) of the forklift. When the load 10 is raised, the load 10 is pushed up by the hydraulic oil from the hydraulic pump 1, and when the load 10 is lowered, the hydraulic oil in the lift cylinder 9 is discharged from the tank passage 8 to the tank 2 by the weight of the load 10.

The tilt cylinder control valve 6 drives the tilt cylinder 11, and the fork of the forklift is tilted by the tilt cylinder 11. At the time of tilt, hydraulic oil from the hydraulic pump 1 is supplied to one of the tilt cylinders 11, and the other oil is discharged from the tank passage 8 to the tank 2.

The main spool 12 of the lift cylinder control valve 5 and the main spool 13 of the tilt cylinder control valve 6 communicate the hydraulic oil from the hydraulic pump 1 to the tank 2 by connecting the bypass passage 3 at a neutral position. And configured to unload the output. At this time, the cylinder ports 14, 15 of both control valves 5, 6 are blocked.

The primary side of the bypass passage 3 is located downstream of the tilt cylinder control valve 6 and upstream of the junction 25 between the tank passage 8 and the bypass passage 3 that pass from the control valves 5 and 6 to the tank 2. A pressure generating valve 16 is provided. The primary pressure generating valve 16 controls the flow of the hydraulic oil in the bypass passage 3 to generate a predetermined pressure on the primary side of the pressure reducing valve 4. The oil depressurized by the pressure reducing valve 4 secures a pilot pressure for operating the lift cylinder control valve 5 and the tilt cylinder control valve 6 as electromagnetic proportional control valves.

The lift cylinder control valve 5 controlled by the pilot pressure includes electromagnetic proportional pressure reducing valves 17 and 18.
The pressure from the pilot passage 21 connected to the pressure reducing valve 4 is set as the primary pressure, and the electromagnetic proportional pressure reducing valve 17 or the electromagnetic proportional pressure reducing valve 18 is excited by exciting the coil of the electromagnetic proportional pressure reducing valve 17 or 18. 2 for electromagnetic proportional pressure reducing valve 18
The next pressure is generated, and the lift cylinder main spool 12 strokes from the neutral position. When the coils of the electromagnetic proportional pressure reducing valves 17 and 18 are not excited, the lift cylinder main spool 12 blocks the lift cylinder port 14 and the lift cylinder 9 is held while the load 10 is held. The tilt cylinder control valve 6 is provided with electromagnetic proportional pressure reducing valves 19, 20. The pressure from the pilot passage 21 connected to the pressure reducing valve 4 is set to the primary pressure, and the electromagnetic proportional pressure reducing valve 19 or the electromagnetic proportional pressure reducing valve is used. By energizing the coil of the valve 20, the tilt cylinder main spool 13
Strokes from the neutral position.

FIG. 2 is a hydraulic circuit diagram showing a state where the above-described electromagnetic proportional control valve for a forklift is operated.
Fig. 3 is a hydraulic circuit diagram when the lift is raised, (b) is a hydraulic circuit diagram when the lift is lowered, and (c) is a hydraulic circuit diagram when the lift is lowered and the tilt is tilted simultaneously. The operation of the electromagnetic proportional control valve 24 configured as described above will be described below based on FIG. 1 and FIG. 2 described above.

First, as shown in FIG. 1, when the lift cylinder control valve 5 and the tilt cylinder control valve 6 are in a neutral state, the spools 12 and 13 of the control valves 5 and 6 communicate with the bypass passage 3 in a neutral state. Since the pump 1 rotates in the state in which the primary pressure is generated, the hydraulic oil flowing from the P port passes through the bypass passage 3 and the primary pressure generating valve 16.
To reach. At this time, since the primary pressure generating valve 16 is in a closed state, the pressure in the bypass passage 3 on the upstream side of the primary pressure generating valve 16 increases.

In this state, if the pressure in the bypass passage 3 becomes higher than the set pressure of the primary pressure generating valve 16 (for example, the pressure equivalent to the spring force of the primary pressure generating valve 16 + the secondary pressure of the pressure reducing valve 4), Since the spool of the primary pressure generating valve 16 strokes to connect the P port side and the T port side, the hydraulic oil flowing from the P port is returned to the tank 2 from the T port. In this state, since the pressure in the bypass passage 3 is equal to or higher than the set pressure of the primary pressure generating valve 16, the primary pressure of the pressure reducing valve 4 is always ensured.

Next, during the lift-up operation shown in (a), when the coil of the electromagnetic proportional pressure reducing valve 17 is excited, the main spool 1
2 strokes, the bypass passage 3 is fully closed by the main spool 12, the parallel passage 26 and the cylinder port 1
4 and the lift cylinder 9 is driven upward.
In the transitional state from the neutral state to the state (a), until the bypass passage 3 is fully closed by the main spool 12, a part of the hydraulic oil flowing from the P port passes through the bypass passage 3 and the primary pressure generating valve. Through the pressure reducing valve 4 as in the neutral state.
A pressure equal to or higher than the set pressure of the pressure reducing valve 4 is secured on the next side.
After the bypass passage 3 is fully closed by the main spool 12,
All of the hydraulic oil flowing from the P port is lift cylinder 9
, The lift cylinder 9 always rises, and the necessary pressure is generated at the P port. However, this pressure is usually higher than the set pressure of the pressure reducing valve 4. In this way,
Irrespective of the position of the main spool 12 from the neutral position to the ascending operation side, a pilot pressure necessary for normally operating the electromagnetic proportional pressure reducing valve 17 is always ensured. Further, since there is no pilot pressure generating mechanism such as the sequence valve of the prior art (FIG. 3) in the passage from the P port to the cylinder port 14, the pressure loss during this time should be minimized in the oil passage. Can be. As a result, a predetermined lift rising speed can be obtained with a minimum motor capacity.

At the time of the lift lowering operation shown in FIG.
When the coil of the electromagnetic proportional pressure-reducing valve 18 is excited, the main spool 12 strokes in the illustrated direction, and the holding side of the lift cylinder 9 communicates with the tank passage 8 to lower the load 10. In this state, since the bypass passage 3 is not blocked by the main spool 12, the hydraulic oil flowing from the P port is always guided to the primary pressure generating valve 16, and the P port pressure rises due to the operation of the primary pressure generating valve 16. Thus, a pilot pressure necessary for normally operating the electromagnetic proportional pressure reducing valve 18 is secured.

Furthermore, since the junction 25 between the tank passage 8 and the bypass passage 3 is located downstream of the primary pressure generating valve 16, the return oil from the lift cylinder 9 causes the primary pressure to be generated from the tank passage 8. It flows out to the T port without passing through the valve 16. For this reason, the pressure loss from the lift cylinder 9 to the T port can be minimized, and the lowering speed does not slow down even in the lift lowering operation under a light load.

(C) shows a state at the time of simultaneous operation of lowering the lift and tilting backward. In this state, since the bypass passage 3 is closed by the main spool 13 of the tilt cylinder control valve 6, there is no flow of hydraulic oil in the primary pressure generating valve 16, and the pressure adjustment of the primary pressure generating valve 16 is performed. The part is fully closed. The operation of the tilt cylinder 11 increases the P port pressure, and this pressure serves as a pilot pressure source for the lift cylinder control valve 5 and the tilt cylinder control valve 6. In this state, the excitation of the coil of the electromagnetic proportional pressure reducing valve 20 is released, the tilt control valve 6 is returned to the neutral state, and the operation moves to the independent operation (b) for lowering the lift.
Because 3 is returned to the neutral position and communicates downstream, 1
Hydraulic oil flows through the secondary pressure generating valve 16, and the primary pressure generating valve 16 shifts from a fully closed state to a pressure regulating state. During this time, the pressure adjusting section of the primary pressure generating valve 16 is operated in the opening direction by the flow of the hydraulic oil from the fully closed state to be in the pressure regulating state. The pressure, that is, the pilot pressure of the control valves 5 and 6 can be secured.

In this embodiment, the pressure of the pressure reducing valve 4 is guided to the primary pressure generating valve 16 through the pressure detection path 23, so that the primary pressure generating valve 16 is adjusted according to the set pressure of the pressure reducing valve 4. The pressure detection path 2
The valve 3 need not always be provided, and a valve that generates a primary pressure equal to or higher than the set pressure of the pressure reducing valve 4 using only a spring may be provided.

The above-described embodiment is one embodiment, and various changes can be made without departing from the spirit of the present invention, and the present invention is not limited to the above-described embodiment.

[0030]

The present invention is embodied in the form described above and has the following effects.

The pressure loss from the hydraulic oil supplied by the pump to each of the actuator ports can be reduced. For example, the self-weight lowering operation by the load of the single-acting cylinder such as the lift lowering operation and the simultaneous operation of other actuators can be performed. In addition, it is possible to prevent the breathing phenomenon of the self-weight lowering when shifting to the single operation of the self-weight lowering.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of an electromagnetic proportional control valve for a forklift showing an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing a state in which an electromagnetic proportional control valve for a forklift shown in FIG. 1 is operated, (a) is a hydraulic circuit diagram when the lift is raised, and (b) is a hydraulic circuit diagram when the lift is lowered. (C) is a hydraulic circuit diagram at the time of simultaneous operation of lowering the lift and tilting backward.

FIG. 3 is a hydraulic circuit diagram of a conventional electromagnetic proportional control valve for a forklift.

4 is a hydraulic circuit diagram showing a state where the electromagnetic proportional control valve for a forklift shown in FIG. 3 is operated, (a) is a hydraulic circuit diagram when the lift is raised, and (b) is a hydraulic circuit diagram when the lift is lowered. (C) is a hydraulic circuit diagram at the time of simultaneous operation of lowering the lift and tilting backward.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hydraulic pump 2 ... Tank 3 ... Bypass passage 4 ... Pressure reducing valve 5 ... Lift cylinder control valve 6 ... Tilt cylinder control valve 7 ... Relief valve 8 ... Tank passage 9 ... Lift cylinder 10 ... Load (fork) 11 ... Tilt Cylinder 12 ... Lift cylinder main spool 13 ... Tilt cylinder main spool 14 ... Lift cylinder port 15 ... Tilt cylinder port 16 ... Primary pressure generating valve 17, 18 ... Electromagnetic proportional pressure reducing valve 19, 20 ... Electromagnetic proportional pressure reducing valve 21 ... Pilot passage 22: drain passage 23 ... pressure detection passage 24 ... electromagnetic proportional control valve 25 ... junction 26 ... parallel passage 27, 28 ... inlet port 29, 30 ... check valve

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuyuki Yabumoto 234 Matsumoto, Hazeya-cho, Nishi-ku, Kobe-shi, Hyogo Kawasaki Heavy Industries, Ltd. Nishi-Kobe Plant F-term (reference) 3F333 AA02 AB13 DB02 FH05 FH08 3H089 AA60 AA71 BB02 BB10 CC11 DB03 DB47 DB49 DB55 EE05 EE31 GG02 JJ09

Claims (3)

[Claims] A first control valve disposed on a bypass passage connecting the pump port and the tank port, and the control valve is configured to communicate with the bypass passage at a neutral position of each control valve; A pilot passage connected from the bypass passage on the upstream side of the control valve to the primary side of the electromagnetic pilot valve for controlling each control valve, and return oil from an actuator connected to the control port of each control valve In the actuator control device provided with a tank passage that merges with the downstream bypass passage of the last control valve, on the downstream bypass passage of the last control valve,
When the hydraulic oil flows upstream of the junction of the tank passage and the bypass passage, a primary pressure of the electromagnetic pilot valve for controlling the control valve is generated on the upstream side.
An electromagnetic control valve for an industrial vehicle, comprising a secondary pressure generating valve. 2. The industrial vehicle according to claim 1, wherein a pressure reducing valve is provided in the pilot passage, and primary pressure of an electromagnetic pilot valve for controlling each control valve is led from a secondary side of the pressure reducing valve. Solenoid control valve. 3. The secondary pressure of the pressure reducing valve is guided to a spring chamber of the primary pressure generating valve, and the upstream pressure of the primary pressure generating valve is adjusted by the secondary pressure and the spring force. The electromagnetic control valve for an industrial vehicle according to claim 2.