JP3234053B2 - Hydraulic circuit for 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 circuit as a power source in an industrial vehicle such as a forklift truck.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional hydraulic circuit for an industrial vehicle, for example, a hydraulic circuit for a forklift truck. In this configuration, the hydraulic pump 2 is driven by the engine 1 which is a work power source, and the hydraulic oil in the hydraulic oil tank 3 can be supplied to the flow priority valve F. A power steering cylinder device is connected via a steering valve 4 to the priority flow extraction port P1 side of the flow priority valve F, so that a constant flow of hydraulic oil can always be supplied to the power steering hydraulic circuit 5. Has become.

A control valve 6 for cargo handling is provided on the side of the excess flow outlet port P2 of the flow priority valve F.
, A lift cylinder device 7 and a tilt cylinder device 8 that perform lifting and lowering and tilting of the mast are connected.
When the cargo handling device is not in operation, the lift cylinder spool 6a and the tilt cylinder spool 6b of the cargo handling control valve 6 are held at the neutral position of the open center, and the surplus in the supply flow rate from the hydraulic pump 2 is maintained. The flow rate, that is, the hydraulic oil flowing to the cargo control valve 6 returns to the hydraulic oil tank 3 through the neutral position. When the spools 6a and 6b are switched to the actuator operation side, the hydraulic oil flowing to the cargo control valve 6 is supplied to the corresponding cylinder devices 7 and 8, and the cargo handling operation is performed.

When the steering valve 4 is held at the neutral position, the operating oil flowing out of the priority flow outlet port P1 of the flow priority valve F is:
It returns to the hydraulic oil tank 3 through the neutral position. When the steering valve 4 is switched to the actuator operation side, the priority flow is supplied to the power steering cylinder device 5.

In the drawings, reference numeral 9 denotes a relief valve for cargo handling operation, and reference numeral 10 denotes a relief valve for power steering. As shown in FIGS. 7 and 8, the structure of the flow priority valve F is such that one end opening of a hollow portion formed in the valve housing 20 and extending in the left-right direction has a screw member 2.
1, a connector 22 having a bottomed cylindrical shape is coaxially fitted to the other end opening side, and an oil chamber is formed between the screw member 21 and the connector 22.

The oil chamber communicates with a hydraulic pump supply connection port P3, which is an input port, and a surplus outlet port P2.
3a communicates. The priority flow passage 23 communicates with a first oil chamber 24, which will be described later, and communicates with the inside of the connector 22 via a priority flow control restrictor 26 opened at a side peripheral portion of the connector 22. ing. The opening of the connector 22 is a priority flow extraction port P1.

A flow control spool 27, which is a mover, is slidably fitted in the oil chamber, so that the oil chamber is divided into two, a first oil chamber 24 and a second oil chamber 25. It is partitioned. Then, the spool 27 is moved to the left side (the first oil chamber 24).
Side), the degree of opening of the one end opening 23a in the priority flow passage 23 is increased by the spool land, and the degree of opening of the opening to the surplus flow discharge port P2 is reduced. As the position 27 moves to the right, the degree of opening of the one end opening 23a in the priority flow passage 23 decreases, and the degree of opening of the opening to the excess flow extraction port P2 increases.

Further, a second portion is provided at the bottom of the connector 22.
A spool operation control throttle 28 communicating with the oil chamber 25 side is opened, and a bottomed hole 27a which is a hollow portion extending in the extending direction of the spool 27 is formed at the end of the spool 27 facing the spool operation control throttle 28. The setting spring 29 extending in the left-right direction is disposed between the bottom of the bottomed hole 27a and the end face of the connector 22, whereby the spool 27 is biased toward a predetermined position.

When the hydraulic oil is supplied from the hydraulic pump 2 to the flow priority valve F having the above structure, the spool 27 is located at a position as shown in FIG. After passing through the flow path 23, the priority flow control restrictor 26, and the connector 22, it flows to the priority flow extraction port P1, and the remaining excess flow flows out to the excess flow extraction port P2. Then, the load fluctuation of the cargo handling and the load fluctuation of the power steering are compared with the priority flow extraction port P1 side and the second oil chamber 2 across the spool operation control throttle 28.
5 and the differential pressure between the first oil chamber 24 and the second oil chamber 25, and the spool 27 slides to the left and right. The opening degree of the opening 23a is adjusted so that the supply flow rate to the priority flow extraction port P1 is maintained at a set value.

[0010]

However, in the hydraulic circuit having the above-described structure, if the load on the cargo handling side is suddenly applied while the engine 1 is idling at a low torque, the first circuit is temporarily stopped. When the pressure in the oil chamber 24 suddenly increases, the flow control spool 27 moves rapidly, and the opening of the one end opening 23a of the priority flow passage 23 is sharply narrowed. There is a danger that the engine will suddenly rise and stop the engine.

At this time, the relationship between the discharge pressure of the hydraulic pump 2 and the rotation speed of the engine 1 is as shown in FIG. In order to prevent such a sudden increase in the load of the hydraulic pump, the opening area of the spool operation control throttle 28 may be reduced to slow down the response of the spool 27 to the load fluctuation. In the case where the response of step 27 is slowed down, if an operation such as a sudden operation or a reversing operation in the power steering operation is performed to rapidly increase the load on the steering cylinder device 5, the priority flow passage 23 is closed. The increase in the degree of opening of the one end opening 23a and the decrease in the degree of opening of the opening to the surplus flow take-out port P2 cannot quickly follow the load fluctuation, and the supply flow rate to the power steering circuit temporarily exceeds the set value. And may cause problems such as a catching phenomenon during steering operation.

As described above, the above-mentioned conventional hydraulic circuit includes the above-mentioned problem that is contrary to the size of the opening area of the spool operation control throttle 28. The present invention has been made in view of the above-mentioned problems, and the operation of the flow control spool has been optimized by simple means.
It is an object of the present invention to provide a hydraulic circuit in which the load of the hydraulic pump does not rise rapidly even when the load of the cargo handling operation suddenly increases in the idle rotation state.

[0013]

To achieve the above object, a hydraulic circuit for an industrial vehicle according to the present invention comprises a hydraulic pump driven by a working power source connected to an input port of a flow priority valve. A fluid pressure circuit for power steering is connected to the priority flow extraction port side of the flow priority valve, and a fluid pressure circuit for cargo handling equipment is connected to the excess flow extraction port side of the flow priority valve. The flow control spool is urged to a predetermined position by a setting spring, and one of the liquid chambers defined by the flow control spool and the passage to the priority flow extraction port are communicated by a spool operation control throttle. The flow control spool is activated by the differential pressure across the operation control throttle, and the flow to the priority circuit side is set to the set value. In the fluid pressure circuit of an industrial vehicle, the flow control spool only resists the fluid passing through the spool operation control throttle only when the flow control spool moves suddenly in a direction to narrow the opening of the passage to the priority flow extraction port. Is provided in the spool operation control throttle.

The resistance means includes, for example, a throttle portion having an opening area smaller than an opening area of the spool operation control throttle and capable of communicating with the spool operation control throttle, and bypassing a fluid which can flow through the throttle portion. There is a check valve with a throttle provided with a bypass passage for closing, and a closing mechanism for closing the bypass passage only when the flow control spool moves suddenly in a direction to narrow the opening of the passage to the priority flow extraction port.

Alternatively, a fluid pressure pump driven by a working power source is connected to an input port of the flow priority valve, and a power steering fluid pressure circuit is connected to a priority flow extraction port side of the flow priority valve. A fluid pressure circuit for a cargo handling device is connected to the surplus flow take-out port side of the flow priority valve, and the flow priority valve has a flow control spool urged to a predetermined position by a setting spring, and the flow control spool is Of the two liquid chambers defined, one of the liquid chambers and a passage to the priority flow extraction port are communicated with a spool operation control throttle, and the flow control spool is operated by a differential pressure across the spool operation control throttle. In a fluid pressure circuit for an industrial vehicle that holds a flow rate to the priority circuit side at a set value, A communication passage for communicating the other liquid chamber defined by the spool with the passage to the priority flow extraction port is provided in the flow control spool or the valve housing, and the other passage is connected to the other flow passage from the passage to the priority flow extraction port. A resistance means for increasing the resistance to the fluid passing through the communication passage only when the fluid suddenly flows into the chamber is provided in the communication passage.

As the resistance means, for example, a check valve with a throttle may be adopted.

[0017]

[Function] When the working power source is in the idle state,
When the loading load is suddenly applied, the other liquid chamber temporarily increases suddenly, and the flow control spool temporarily decreases the opening degree of the opening of the passage to the priority flow extraction port. Try to move.

At this time, since the resistance means increases the resistance to the fluid passing through the spool operation control throttle, the movement of the fluid control spool becomes slower than in the prior art, and the passage to the priority flow outlet port is reduced. Since the opening degree of the opening is prevented from being sharply reduced, the load of the fluid pressure pump discharging the hydraulic oil to the flow priority valve is prevented from sharply increasing.

In other cases, the resistance to the fluid passing through the spool operation control throttle is the same as that of the conventional art, so that even if the load of the power steering acts suddenly, the disadvantage of the steering operation occurs as in the conventional art. do not do. As described in claim 3, when the resistance means is provided in the communication path that connects the other liquid chamber and the path to the priority flow extraction port, the working power source is in an idle state. Sometimes, when the cargo load is suddenly applied, the fluid tends to rapidly flow into the other liquid chamber from the passage to the priority flow take-out port, but the fluid flows into the other liquid chamber by the resistance means provided in the communication passage. Sudden inflow of the fluid is suppressed, and the pressure of the other liquid chamber is prevented from increasing rapidly.

Therefore, when the cargo handling load is suddenly applied while the working power source is in the idle state,
Since the movement of the flow control spool is slower than in the past, and the opening of the passage opening to the priority flow extraction port is prevented from being sharply reduced, the hydraulic oil is discharged to the flow priority valve. The load of the fluid pressure pump is prevented from rising rapidly.

In other cases, the resistance to the fluid passing through the communication passage is the same as that of the conventional art, so that even if the load of the power steering acts suddenly, the steering operation does not become inconvenient as in the conventional art.

[0022]

An embodiment of the present invention will be described with reference to the drawings.
First, the configuration will be described. The basic configuration of the hydraulic circuit has the same configuration as the above-described conventional example. As shown in FIG. 6, the hydraulic pump 2 is driven by the engine 1 which is a working power source, and Hydraulic oil in the oil tank 3 can be supplied to the flow priority valve F, and a power steering cylinder device 5 is connected via a steering valve 4 to the priority flow extraction port P1 of the flow priority valve F. Thus, a constant flow of hydraulic oil can always be supplied to the power steering hydraulic circuit. In addition, a control valve 6 for cargo handling is provided on the side of the excess flow take-out port P2 of the flow priority valve F via the cargo control valve 6.
It is connected to a lift cylinder device 7 and a tilt cylinder device 8 that perform lifting and lowering and tilting of the mast.

As shown in FIG. 1, the basic structure of the flow priority valve F has the same basic structure as that of the above-described conventional example, and is formed in the valve housing 20 and extends in the left-right direction. The one end opening side of the screw member 2
1, a connector 22 having a bottomed cylindrical shape is coaxially fitted to the other end opening side, and an oil chamber is formed between the screw member 21 and the connector 22.

The oil chamber is connected to a hydraulic pump supply connection port P3, which is an input port, and a surplus outlet port P2.
3a communicates. The priority flow passage 23 communicates with a first oil chamber 24, which will be described later, and communicates with the inside of the connector 22 via a priority flow control restrictor 26 opened at a side peripheral portion of the connector 22. ing. The opening of the connector 22 is a priority flow extraction port P1.

A flow control spool 27 as a mover is slidably fitted in the oil chamber, so that the oil chamber is connected to two oil chambers, a first oil chamber 24 and a second oil chamber 25. It is partitioned. Then, the spool 27 is moved to the left side (the first oil chamber 24).
Side), the degree of opening of the one end opening 23a in the priority flow passage 23 is increased by the spool land, and the degree of opening of the opening to the surplus flow discharge port P2 is reduced. As the position 27 moves to the right, the degree of opening of the one end opening 23a in the priority flow passage 23 decreases, and the degree of opening of the opening to the excess flow extraction port P2 increases.

The bottom of the connector 22 is provided with a second
A spool operation control throttle 28 communicating with the oil chamber 25 side is opened, and a bottomed hole 27a which is a hollow portion extending in the extending direction of the spool 27 is formed at the end of the spool 27 facing the spool operation control throttle 28. The setting spring 29 extending in the left-right direction is disposed between the bottom of the bottomed hole 27a and the end face of the connector 22, whereby the spool 27 is biased toward a predetermined position.

In this embodiment, an example of the resistance means T according to the present invention is attached to the opening of the spool operation control throttle 28 on the second oil chamber 25 side. As shown in FIGS. 2 and 3, the configuration of the resistance means T includes a check housing 50 in the form of a cap with one end closed, and a check valve body 51 with a throttle provided in the check housing 50.

The check housing 50 has a cylindrical shape, and has an opening-side end surface 50a abutted on an end surface of the connector 22 so as to cover the opening of the spool operation control diaphragm 28, and is fixed. Extending in the sliding direction of
A passage hole 50c communicating with the second oil chamber 25 is opened at the top end 50b. At this time, the spool operation control throttle 2
The check housing 50 is arranged so that the opening 8 is located at the center of the opening of the check housing 50.

In the check housing 50, a check valve body 51 with a throttle is provided so as to be slidable only in the spool 27. Check valve body 51 with throttle
Has a cylindrical shape that can be engaged with the inner peripheral surface of the check housing 50, and has a pair of cutting surfaces 51 that face each other when the peripheral surfaces facing left and right are cut in the extending direction.
b is formed.

Further, the check valve body 51 with a throttle has a bottomed hole 51c formed from the spool 27 side toward the spool operation control throttle 28, and the bottom thereof has a bottom facing the opening of the spool operation control throttle 28. An aperture 52 coaxial with the spool operation control aperture 28 is provided. At this time, the opening area of the throttle 52 of the check valve body 51 is set to be smaller than the opening area of the spool operation control throttle 28.

The pair of cutting surfaces 51b are each provided with a two-sided opening 51a communicating with the bottomed hole 51c. The two-sided opening 51a is formed between the two-sided opening 51a and the cutting surface 51b and the check housing 50. The space therebetween is defined as a bypass 53 that bypasses the above-described aperture. This bypass 53
When the check valve body 51 is pressed against the end face of the connector 22, the entrance of the space between the cutting surface 51b and the check housing 50 is closed by the end face of the connector 22.

With the above configuration, the resistance means T
Constitutes a check valve with throttle as shown in FIG. In the hydraulic circuit having the above configuration, when the cargo handling device is not in operation, the lift cylinder spool 6a and the tilt cylinder spool 6b of the cargo handling control valve 6 are held at the neutral position of the open center, and the hydraulic pressure is increased. The surplus flow rate in the supply flow rate from the pump 2, that is, the hydraulic oil flowing to the cargo handling control valve 6 returns to the hydraulic oil tank 3 through the neutral position. The spool 6
When a and 6b are switched to the actuator operation side, the hydraulic oil flowing to the cargo control valve 6 is supplied to the corresponding cylinder devices 7 and 8, and the cargo handling operation is performed.

When the steering valve 4 is held at the neutral position, the operating oil flowing out of the priority flow outlet port P1 of the flow priority valve F is:
It returns to the hydraulic oil tank 3 through the neutral position. When the steering valve 4 is switched to the actuator operation side, the priority flow is supplied to the power steering cylinder device 5.

When the hydraulic oil is supplied from the hydraulic pump 2, the set flow rate is changed to the priority flow path 23,
After passing through the priority flow control restrictor 26 and the connector 22, it flows to the priority flow extraction port P1, and the remaining excess flow flows to the excess flow extraction port P2. In addition, the load fluctuation of the cargo handling and the load fluctuation of the power steering are controlled by the priority flow extraction port P1 across the spool operation control throttle 28 and the second oil chamber 25.
And the spool 27 slides to the left and right, and the one end opening 23a of the priority flow passage 23 is responsive to the pressure difference between the first oil chamber 24 and the second oil chamber 25. Is adjusted so that the flow rate supplied to the priority flow extraction port P1, that is, the power steering circuit, is maintained at a set value.

At this time, when the engine 1 is idle and the cargo handling load is suddenly applied in order to carry out the cargo handling operation, the pressure in the first oil chamber 24 is temporarily reduced to the second oil chamber 2.
5, the spool 27 closes the one end opening 23a of the priority flow passage 23, that is, the spool 27 moves to the right in the drawing, and the hydraulic oil in the second oil chamber 25 An attempt is made to flow out to the connector 22 through the operation control throttle 28.

Then, the check valve body 51 with the throttle moves to the opening side of the spool operation control throttle 28 and the connector 2
2 to close the entrance of the bypass passage 53. As a result, the hydraulic oil in the second oil chamber 25 enters the bottomed hole 51c of the check valve main body 51 with a throttle through the passage hole 50c of the check housing 50, and operates the spool via the throttle of the check valve main body 51 with the throttle. It passes through the control aperture 28 and flows to the connector 22 side.

At this time, since the opening area of the throttle of the check valve body 51 with the throttle is smaller than the opening area of the spool operation control throttle 28, the resistance to the fluid passing through the spool operation control throttle 28 increases more than before. As a result, the operation of the spool 27 becomes slow, and the priority flow path 2
3 is prevented from being narrowed, and as a result, FIG.
As shown in (1), a sudden increase in the load on the hydraulic pump 2 is suppressed, and inconvenience such as engine stop is avoided.

When the load by the steering circuit is suddenly applied, the internal pressure in the connector 22 increases, and the hydraulic fluid flows through the spool operation control throttle 28 into the second oil chamber 25.
, The spool 27 attempts to move in the left direction in the figure, that is, in a direction to open the opening of the one end opening 23 a of the priority flow passage 23. At this time, the check valve body with throttle 51
Moves in the direction away from the spool 27 side, that is, the end face of the connector 22, and the bypass passage 53 is opened.

Thus, the spool operation control throttle 28
The hydraulic oil flows into the second oil chamber 25 through the throttle of the check valve main body 51 with a throttle, flows into the bottomed hole 51c, the gap between the check housing 50 and the cutting surface 51b, and the two-sided opening 51a. And flows into the bottomed hole 51c through the bottomed hole 51c, and flows into the second oil chamber 25 through the passage hole 50c of the check housing 50.

As described above, the check housing 50 and the cutting surface 5 are not affected by the throttle action of the check valve body 51.
1b and a bypass path 5 having a two-sided opening 51a
Since the working oil flows into the second oil chamber 25 through the third cylinder 3, the responsiveness of the spool 27 maintains the conventional characteristics, and no inconvenience occurs in the steering operation such as a feeling of being caught. The supply amount to the circuit is held at the set value.

In the above embodiment, the check valve as the resistance means is provided on the second oil chamber 25 side, but may be provided on the opening of the flow control throttle on the connector 22 side. Further, since the check valve with a throttle is an example, another known check valve with a throttle may be adopted. Next, a second embodiment will be described.

The flow priority valve of the second embodiment is also
As shown in FIG. 11, it has a basic structure similar to that of the first embodiment described above, and one end opening side of a hollow portion formed in the valve housing 20 and extending in the left-right direction is closed by a screw member 21. At the same time, a connector 22 having a bottomed cylindrical shape is coaxially fitted to the other opening side, and the screw member 2
An oil chamber is formed between the connector 1 and the connector 22.

The oil chamber is connected to a hydraulic pump supply connection port P3, which is an input port, and a surplus outlet port P2.
3a communicates. The priority flow passage 23 communicates with the inside of the connector 22 via a priority flow control throttle 26 which is opened at a side peripheral portion of the connector 22. The opening of the connector 22 is a priority flow extraction port P1.

A flow control spool 27 as a mover is slidably fitted in the oil chamber, so that the oil chamber is divided into a first oil chamber 24 and a second oil chamber 25. Is divided into Then, the spool 27 is moved to the left side (the first oil chamber 24).
Side), the degree of opening of the one end opening 23a in the priority flow passage 23 is increased by the spool land, and the degree of opening of the opening to the surplus flow discharge port P2 is reduced. As the position 27 moves to the right, the degree of opening of the one end opening 23a in the priority flow passage 23 decreases, and the degree of opening of the opening to the excess flow extraction port P2 increases.

The bottom of the connector 22 has a second
A spool operation control throttle 28 communicating with the oil chamber 25 side is opened, and a bottomed hole 27a which is a hollow portion extending in the extending direction of the spool 27 is formed at the end of the spool 27 facing the spool operation control throttle 28. The setting spring 29 extending in the left-right direction is disposed between the bottom of the bottomed hole 27a and the end face of the connector 22, whereby the spool 27 is biased toward a predetermined position.

In this embodiment, the communication part which connects the priority passage 23 inside the valve housing 20 and the first oil chamber 24 in the first embodiment is closed. Communication passage 7 for communicating between the use passage 23 and the first oil chamber 24
0 is provided in the spool 27, and a check valve with a throttle, which is an example of the resistance means T based on the present invention, is attached in the middle of the communication passage 70.

As shown in FIG. 12, the communication path 70
An opening 70a is formed in the center of the surface of the spool 27 facing the first oil chamber 24. The opening 70a is bored coaxially with the spool 27 toward the second oil chamber 25 from the opening 70a. Thus, the valve guide portion 71 is formed. The second oil chamber 25 side of the valve guide portion 71 has a larger diameter to form a large-diameter portion 71b, and extends in a radial direction of the spool 27 from the peripheral surface of the large-diameter portion 71b to form a priority flow passage. 23.

A check valve body 72 with a throttle is slidably provided in the valve guide 71 of the communication passage 70. The outer shape of the throttled check valve main body 72 has a cylindrical shape capable of engaging with the inner peripheral surface of the valve guide main body 71a, and is fitted to the valve guide main body 71a so as to be slidable in the axial direction. The end face of the first oil chamber 24 side is the first face of the valve guide body 71a.
It can contact the end face on the oil chamber 24 side.

The check valve body with throttle 72 has a pair of cut surfaces 72b opposed to each other by cutting the peripheral surfaces facing left and right in the extending direction. The throttle-equipped check valve body 72 has a bottomed hole 72c formed from the large-diameter portion 71b toward the first oil chamber 24, and has an opening at the bottom of the communication passage 70 in the first oil chamber 24 side. A diaphragm 73 is opened coaxially toward the section.

The pair of cutting surfaces 72b are each provided with a two-sided opening 72a communicating with the bottomed hole 72c, and the two-sided opening 72a, the cutting surface 72b and the valve guide 71 are provided. The space between is defined as a bypass that bypasses the aperture. When the check valve main body 72 is pressed against the end surface of the valve guide portion 71 on the first oil chamber 24 side, the entrance of the space between the cutting surface 72b and the valve guide portion 71 is formed in the bypass passage. The side end face is closed.

In the hydraulic circuit having the above configuration, when the cargo handling device is inactive, the lift cylinder spool 6a and the tilt cylinder spool 6b of the cargo handling control valve 6 are held at the neutral position of the open center. Thus, the surplus flow rate in the supply flow rate from the hydraulic pump 2, that is, the hydraulic oil flowing to the cargo control valve 6 returns to the hydraulic oil tank 3 through the neutral position. When the spools 6a and 6b are switched to the actuator operation side, the hydraulic oil flowing to the cargo control valve 6 is supplied to the corresponding cylinder devices 7 and 8, and the cargo handling operation is performed.

When the steering valve 4 is held at the neutral position, the operating oil flowing out of the priority flow outlet port P1 of the flow priority valve F is:
It returns to the hydraulic oil tank 3 through the neutral position. When the steering valve 4 is switched to the actuator operation side, the priority flow is supplied to the power steering cylinder device 5.

When the hydraulic oil is supplied from the hydraulic pump 2, the set flow rate is changed to the priority flow passage 23,
After passing through the priority flow control restrictor 26 and the connector 22, it flows to the priority flow extraction port P1, and the remaining excess flow flows to the excess flow extraction port P2. Further, the load fluctuation of the cargo handling and the load fluctuation of the power steering are controlled by the differential pressure between the priority flow outlet port P1 and the second oil chamber 25 across the spool 27 operation control throttle 28, and the first oil chamber 24 and the second oil chamber 25. The spool 27 slides left and right in response to the change in the differential pressure of
Is adjusted so that the flow rate supplied to the priority flow extraction port P1, that is, the power steering circuit, is maintained at a set value.

At this time, when the engine 1 is idle and the cargo handling load is suddenly applied in order to carry out the cargo handling operation, the engine 1 is temporarily and suddenly moved through the priority flow passage 23 and the communication passage 70. When the hydraulic oil tries to flow into the first oil chamber 24, the check valve main body 72 with the throttle is pushed by the hydraulic oil and moves toward the first oil chamber 24, and the first oil chamber of the valve guide portion 71. It abuts on the side end surface and closes the opening of the communication passage 70 on the first oil chamber 24 side.

As a result, the hydraulic oil passing through the communication passage 70 enters the bottomed hole 72c of the check valve main body 72 with the throttle through the passage hole 50c of the valve guide portion 7172, and the throttle 73 of the check valve main body 72 with the throttle is closed. And flows toward the first oil chamber 24 through the first oil chamber 24. As a result, the resistance to the fluid passing through the communication passage 70 sharply increases, so that the pressure increase in the first oil chamber 24 becomes slow, and the sudden movement of the spool 27 to the right is temporarily suppressed. Is done. That is, it is possible to prevent the opening portion of the priority flow passage 23 from being sharply narrowed, and accordingly, the configuration shown in FIG.
As shown by 0, the load on the hydraulic pump 2 does not suddenly increase, and inconvenience such as engine stop is avoided.

When the load by the steering circuit is suddenly applied, the internal pressure in the connector 22 increases, and the hydraulic fluid is supplied to the second oil chamber 25 through the spool operation control throttle 28.
, The spool 27 attempts to move in the left direction in the figure, that is, in a direction to open the opening of the one end opening 23 a of the priority flow passage 23. At this time, the hydraulic oil in the first oil chamber 24 is
After passing through the communication passage 70 and flowing out to the priority passage passage 23 side, at this time, the check valve main body 72 with the throttle is located on the first oil chamber 24 side, that is, the end surface of the valve guide 71 on the first oil chamber 24 side. Moving in a direction away from the vehicle to open the bypass.

As a result, the hydraulic oil flowing out of the first oil chamber 24 flows into the bottomed hole 72c through the throttle 73 of the check valve body 72 with a throttle, and the hydraulic oil between the valve guide 71 and the cutting surface 72b. It flows into the bottomed hole 72c through the gap and the two-sided opening 72a, and flows out from the bottomed hole 72c through the large-diameter portion 71b of the valve guide 71 to the priority flow passage 23 side.

As described above, the working oil in the first oil chamber 24 flows out through the gap between the valve guide 71 and the cutting surface 72b and the bypass path of the two-sided opening 72a without affecting the throttling action of the check valve body 72. Therefore, the responsiveness of the spool 27 maintains the conventional characteristics, and the supply amount to the power cylinder circuit, which is the priority circuit, is held at the set value without causing any inconvenience in steering operation such as a feeling of being stuck. .

In the second embodiment, the communication passage 70 and the check valve as the resistance means are provided in the spool 27. However, as shown in FIG. A communication portion that communicates with the first oil chamber 24 may be provided inside, and the above-described resistance means may be installed in the communication portion. Conventionally, when the pressure on the surplus flow side is higher than the pressure on the priority flow side, the surplus flow discharge port is
There is a possibility that the hydraulic fluid leaks to the fifth side, but if such a leakage phenomenon occurs, in the flow priority valve F of the first embodiment, the hydraulic fluid flows into the second oil chamber 25 by the resistance means T. , The response of the spool 27 may be slightly delayed, but in the second embodiment, the installation of the resistance means T does not affect the hydraulic oil flowing through the spool operation control throttle 28, There is no fear that the response of 27 will be delayed.

The above check valve with throttle is an example, and other known check valves with throttle may be used.

[0061]

As described above, in the hydraulic circuit for an industrial vehicle according to the present invention, when an operating power source such as an engine is in an idling state, the load of the hydraulic pump can be reduced even if the load is suddenly applied. It is possible to prevent a sudden rise and prevent the occurrence of problems such as a stop of the operating power source, and also to prevent the occurrence of troubles such as catching at the time of steering operation as in the related art even at the time of sudden steering operation. effective.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a flow priority valve according to an embodiment of the present invention.

FIG. 2 is a detailed view of a portion A in FIG. 1 showing a check valve with a throttle according to an embodiment of the present invention.

FIG. 3 is a sectional view taken along line BB in FIG. 2;

FIG. 4 is a diagram showing an open state of a bypass in the check valve with a throttle according to the embodiment of the present invention.

FIG. 5 is a diagram showing oil pressure symbols of the check valve with throttle according to the embodiment of the present invention.

FIG. 6 is a diagram showing a hydraulic circuit in a forklift truck.

FIG. 7 is a side sectional view showing a conventional flow priority valve.

FIG. 8 is a side sectional view showing a state when a hydraulic pump is operated in a conventional flow priority valve.

FIG. 9 is a diagram illustrating a hydraulic pump load and an engine speed in a conventional hydraulic circuit.

FIG. 10 is a diagram showing a hydraulic pump load and an engine speed in the hydraulic circuit of the embodiment according to the present invention.

FIG. 11 is a side sectional view showing a flow priority valve of a second embodiment according to the present invention.

FIG. 12 is a detailed sectional view showing a check valve with a throttle according to a second embodiment of the present invention.

FIG. 13 is a longitudinal sectional view showing a check valve with throttle according to a second embodiment of the present invention.

FIG. 14 is a side sectional view showing a flow priority valve according to a third embodiment of the present invention.

[Explanation of symbols]

 F Flow priority valve T Resistance means P1 Priority flow discharge port P2 Excess flow discharge port 1 Engine 2 Hydraulic pump 5 Power steering cylinder device 7, 8 Cargo handling cylinder device 24 First oil chamber 25 Second oil chamber 27 Flow control spool 28 Spool operation control throttle 29 Spring 50 Check housing 72a Double opening 72b Cutting surface 52 Throttle 53 Bypass path 70 Communication path 72 Check valve body with throttle

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tsutomu Matsuura 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Nissan Motor Co., Ltd. (56) References JP-U 5-79005 (JP, U) JP-A 61- 137103 (JP, U) Shokai Sho 59-123705 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 5/07

Claims (3)

(57) [Claims] 1. A fluid pressure pump driven by a working power source is connected to an input port of a flow priority valve, and a power steering fluid pressure circuit is connected to a priority flow extraction port side of the flow priority valve. A fluid pressure circuit for a cargo handling device is connected to the surplus flow take-out port side of the flow priority valve, and the flow priority valve has a flow control spool urged to a predetermined position by a setting spring, and the flow control spool is One of the partitioned liquid chambers and a passage to the priority flow take-out port are communicated with a spool operation control throttle, and the flow control spool is operated by a differential pressure across the spool operation control throttle to flow to the priority circuit side. In a hydraulic circuit of an industrial vehicle that maintains the set value at a set value, The spool operation control throttle is provided with a resistance means for increasing resistance to fluid passing through the spool operation control throttle only when the spool operation control throttle suddenly moves in a direction to narrow the opening of the passage to the port. Industrial vehicle fluid pressure circuit. 2. The throttle means having an opening area smaller than the opening area of the spool operation control throttle and capable of communicating with the spool operation control throttle, and bypassing a fluid which can flow through the throttle section. A throttle valve provided with a bypass passage and a closing mechanism that closes the bypass passage only when the flow control spool moves rapidly in a direction to narrow the opening of the passage to the priority flow extraction port. The hydraulic circuit for an industrial vehicle according to claim 1, wherein: 3. A fluid pressure pump driven by a working power source is connected to an input port of the flow priority valve, and a power steering fluid pressure circuit is connected to a priority flow extraction port side of the flow priority valve. A fluid pressure circuit for a cargo handling device is connected to the surplus flow take-out port side of the flow priority valve, and the flow priority valve has a flow control spool urged to a predetermined position by a setting spring, and the flow control spool is Of the two liquid chambers defined, one of the liquid chambers and a passage to the priority flow extraction port are communicated with a spool operation control throttle, and the flow control spool is operated by a differential pressure across the spool operation control throttle. In a fluid pressure circuit for an industrial vehicle that holds a flow rate to the priority circuit side at a set value, A communication passage for communicating the other liquid chamber defined by the liquid flow passage with the passage to the priority flow take-out port is provided in the flow control spool or the valve housing, and the communication passage from the passage to the priority flow take-out port to the other liquid chamber is provided. A fluid pressure circuit for an industrial vehicle, characterized in that a resistance means for increasing the resistance to the fluid passing through the communication passage only when the fluid suddenly flows toward the communication passage is provided in the communication passage.