JP2002225738A - Flow control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve miniaturization, weight saving and low cost in the way that energy consumption of a pump 4 is reduced by reducing a spring load on a spring 46 of a control spool 38 to reduce a discharge flow to a power steering device during rectilinear traveling of a vehicle, and a flow necessary for steering in the steering is secured by restoring the discharge flow by use of a hydraulic pressure of the steering device, and the operation is performed with simple structure. SOLUTION: In this flow control device, a discharge fluid from the pump 4 is led into a chamber 40 on one end part side of the spool 38 fitted in a valve bore 36, the discharge fluid is sent to the power steering device via an orifice 50, a pressure on the downstream side of the orifice 50 is led into a chamber 42 housing the spring 46 on the other end side of the spool 38, and the spool 38 is moved by a difference pressure between the front and the rear of the orifice 50 to return an excessive flow amount to a tank 58. The bottom part of a spring chamber 42 is disposed with a stepped piston 66, the hydraulic pressure of the steering device is applied to its both ends, and the piston 66 is moved according to its rise to increase the spring load on the spring 46.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control device for controlling a part of a pressure fluid discharged from a fluid pressure pump to have a predetermined discharge flow characteristic by recirculating the pressure fluid to a tank side. .

[0002]

2. Description of the Related Art For example, in a power steering device mounted on an automobile and reducing the steering operation force of a driver, a pump as a hydraulic pressure source is usually driven to rotate by an engine of the automobile. Thus, the discharge amount of hydraulic oil from the pump increases or decreases in proportion to a change in the engine speed. Therefore, such a pump is required to have a capacity capable of supplying a sufficient flow rate to a fluid device such as a power steering device even in a low engine speed range, that is, when the pump discharge amount is small. However, when such a pump displacement is set, an unnecessarily large flow rate is supplied to the power steering device in a high engine speed range, so that it is necessary to recirculate the surplus flow rate to the tank side.

For this purpose, an orifice is provided in a supply passage for supplying the pressurized fluid discharged from the pump to the power steering device, and the spool of the flow control valve is operated by a differential pressure across the orifice to open the valve. Then, a part of the pressure fluid (excess flow rate) unnecessary for the operation of the power steering device is smoothly returned to the tank side without causing flow path resistance, and the supply flow rate to the power steering device is less than a certain amount. Is generally adopted.

Further, in recent years, in order to improve the energy saving effect by increasing the surplus flow rate and reducing the flow rate supplied to the power steering device at a neutral position of the steering operation that does not require the steering assist force, the vehicle is driven straight ahead. During traveling, the discharge flow to the power steering device is reduced by lowering the spring load of the flow control valve.On the other hand, at the time of steering, the discharge flow is recovered using the generated operating pressure of the power steering device, and the steering flow is reduced. A power steering device (power steering device) provided with a flow control valve for discharging a required flow rate has been proposed (Japanese Patent Application Laid-Open Nos. 9-66848 and 10-673).
No. 32, JP-A-8-282513, etc.).

In general, a flow control valve has a spool slidably fitted in a valve hole, and defines a first pressure chamber and a second pressure chamber on both ends thereof. Introducing pressure upstream of the orifice provided in the supply passage discharged from the pump and fed to the power steering device, and introducing pressure downstream of the orifice into the second pressure chamber, A spring for urging the spool toward the first pressure chamber is disposed, and the first pressure chamber is connected to the pump when the spool moves due to a differential pressure across the orifice.

The first publication (Japanese Patent Laid-Open No. 9-66)
No. 848) is provided with a control pressure chamber to which the pressure of the second pressure chamber is introduced at the end on the second pressure chamber side, and the second pressure chamber is connected to the control pressure chamber. Between,
One end face is in contact with the spring facing the second pressure chamber,
A movable spring receiving member having the other end surface having a larger area than the one end surface and facing the control pressure chamber is provided, and the movable spring receiving member is provided with a spring member for applying a biasing force toward the control pressure chamber. Further, a control means for controlling the movement of the movable spring receiving member toward the second pressure chamber is provided.

In the flow control device described in the above publication,
When the power steering device is not steered, the pressure of the control pressure chamber (equal to the pressure of the second pressure chamber into which the operating pressure of the power steering device is guided) is low, and the movable spring receiving member is located farthest from the second pressure chamber. Since the length of mounting the spring is the longest, the spring force (set load) of the spring is weakened. Therefore, the spool is controlled by the spring having a small set load.

Further, when the steering operation of the power steering device is performed, the pressure in the control pressure chamber increases, and the movable spring receiving member opposes the spring force of the spring member.
Move to the pressure chamber side, gradually shrink the spring,
Increase the set load. Therefore, the movement of the spool is controlled based on the slightly increased spring force of the spring and the differential pressure across the orifice.

Further, when the pressure in the control pressure chamber reaches a predetermined pressure, the movable spring receiving member moves into the second pressure chamber,
Maximize the set load of the spring. The movement of the movable spring receiving member toward the second pressure chamber is controlled by control means.

Further, a second publication (Japanese Patent Laid-Open No. 10-6733)
In the flow control valve described in No. 2), a piston is slidably fitted to the other end of a spring for urging the spool, similarly to the flow control device of the first publication. Behind this, a post-pressure of the variable throttle is introduced through a passage in the piston, a spring chamber is formed in a gap between the piston rod and the inner peripheral surface of the cylinder, and a spring is housed therein. It communicates with the suction side or the drain side.

In this flow control valve, the movement of the spool is controlled by a spring having a small set load during non-steering, similarly to the flow control device of the first publication.
When the steering operation is performed, the piston moves to compress the spring, and the movement of the spool is controlled based on the increased spring force of the spring and the differential pressure across the orifice.

A third publication (Japanese Unexamined Patent Application Publication No. Hei 8-2825)
No. 13) has a flow control valve (flow control valve) connected to the downstream side of the orifice.
In the pressure chamber (referred to as a first pilot chamber in this device), the spool and the moving body are opposed to each other, and a spring is interposed between the opposed portions of the spool and the moving body. A second pilot chamber is formed behind the movable body (on the opposite side of the spring), and one pressure receiving surface of the movable body facing the first pilot chamber side is opposed to the other pressure receiving surface facing the second pilot chamber. The pressure receiving area of the pressure receiving surface is increased.

Further, a switching spool is slidably incorporated inside the moving body. The switching spool is operated by the pressure in the first pilot chamber. In a normal position, the second spool chamber is connected to a drain chamber communicating with the tank, and the pressure of the first pilot chamber is set. When the pressure becomes equal to or higher than the pressure, the second pilot chamber is disconnected from the drain chamber and connected to the first pilot chamber.

In the flow control valve described in the above publication, the load pressure of the power steering device, that is, the pressure on the downstream side of the orifice does not increase during non-steering, so that the switching spool does not move and the second pilot chamber is moved. Since the moving body is in communication with the drain chamber, the moving body maintains the normal position, and the initial load of the spring in the first pilot chamber is set small.

Further, during steering, the load pressure of the power steering device increases, and the increased pressure is also guided to the first pilot chamber. When the pressure at this time becomes equal to or higher than the set pressure, the switching spool moves to make the first pilot chamber communicate with the second pilot chamber. When pressure is led to both pilot chambers,
The moving body moves against the spring due to the area difference between the pressure receiving surfaces facing both pilot chambers of the moving body.
When the moving body moves in this manner, the initial load of the spring is set to be large.

[0016]

In any of the flow control devices described in the above publications, the spool is controlled by a spring having a small set load during non-steering, so that the maximum supply flow rate of the pump is reduced. Therefore, during steering, the movement of the spool is controlled by a spring having a large set load during steering, so that the maximum supply flow rate can be increased and the flow rate required for steering can be secured.

However, the device described in the first publication requires the movable spring receiving member (piston) to be provided with a spring member (spring), and the number of parts is large.
There is a problem that the size of the pump is also increased. Further, since a control means for controlling the movement of the movable spring receiving member is required, there has been a problem that the structure is complicated and the cost is high.

In addition, the movable spring receiving member is large because it has a spring member, and its movement requires a large amount of oil. Therefore, the amount of oil supplied to the power steering device during an acute steering is insufficient. However, there is also a problem that the handle may be caught.

Further, the flow control valve described in the second publication also has a spring for pressing a piston in a spring chamber, and has the same problem as the device described in the first publication.

Further, the device described in the third publication is
Since it is necessary to control the pressure acting on the moving body by incorporating the switching spool inside the moving body, the structure is complicated, large, and the cost is high. Also, the moving object is large,
Since the movement requires a large amount of oil, there is also a problem that the amount of oil supplied to the power steering device is insufficient at the time of sudden steering, which may cause the steering wheel to be caught.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. When a fluid device such as a power steering device is not operated, the discharge flow rate to the fluid device is reduced to reduce the energy consumption of the pump. It is another object of the present invention to provide a flow control device which does not catch a steering wheel at the time of sudden steering by recovering a flow rate in response to an increase in the operating pressure when operating a fluid device. It is another object of the present invention to provide a low-cost flow control device which has a simple structure, has a small number of parts, and can exhibit the above functions in a compact shape.

[0022]

According to a first aspect of the present invention, there is provided a flow control device comprising: a valve hole formed in a valve body; a spool slidably fitted in the valve hole; A first pressure chamber defined at one end of the spool, into which the pressure fluid discharged from the pump is introduced, and an orifice provided in the supply passage for the pressure fluid discharged from the pump and fed to the fluid device A second pressure chamber defined at the other end of the spool to receive a pressure downstream of the orifice; and a second pressure chamber housed in the second pressure chamber for urging the spool toward the first pressure chamber. With a spring that operates the spool by the differential pressure across the orifice,
A fluid is returned from the first pressure chamber to the tank, and a stepped piston is disposed on the opposite side of the spool with the spring interposed therebetween, and one end of the spring is brought into contact with a small-diameter end thereof, and Applying a pressure downstream of the orifice to the large-diameter end, and introducing a pressure lower than the pressure downstream of the orifice into a chamber formed at the step between the large-diameter portion and the small-diameter portion of the piston. It is characterized by the following.

In the flow control device according to the present invention, when the fluid device to which the pressure fluid discharged from the pump is supplied is inactive, the piston does not move, and the spool is moved by the spring having the longest set length. Is controlled, the amount of recirculation to the tank is increased to reduce the supply to the fluid device, and when the fluid pressure on the downstream side of the orifice increases due to the operation of the fluid device, the piston moves to compress the spring, By controlling the operation of the spool by the spring having the increased set load, the supply amount to the fluid device is quickly increased.

According to a second aspect of the present invention, a second spring is disposed on the outer peripheral side of the spring, one end of which is in contact with the end surface of the spool, and the other end of which is in contact with the end surface of the valve hole. It is characterized by the following.

Further, according to a third aspect of the present invention, in the flow rate control device, a stepped piston is disposed on the opposite side of the spool with the spring interposed therebetween, and a small-diameter end thereof is extended toward the spool. Applying a pressure downstream of the orifice to the large-diameter end, and introducing a pressure lower than the pressure downstream of the orifice into a chamber formed at the step between the large-diameter portion and the small-diameter portion of the piston, When the piston is moved by the operating pressure of the fluid device, the small-diameter end of the piston is brought into direct contact with the spool to apply an axial thrust.

According to the third aspect of the invention, when the fluid pressure on the downstream side of the orifice increases due to the operation of the fluid device, the piston moves, and the extended small-diameter end directly pushes and pushes the spool back. In addition, the supply amount to the fluid device is promptly increased.

According to a fourth aspect of the present invention, a switching valve is provided at the large diameter end of the piston in the introduction passage for guiding the fluid pressure downstream of the orifice, and when the fluid pressure exceeds a predetermined value. The introduction passage is shut off.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 is a longitudinal sectional view showing a vane type oil pump 4 provided with a flow rate control device (indicated by a reference numeral 1 as a whole) according to an embodiment of the present invention.
2 is a longitudinal sectional view of the flow control device 1. FIG. The oil pump 4 has a pump body 10 formed by abutting a substantially cylindrical front body 6 and a plate-shaped rear body 8.
The pump cartridge 12 is accommodated therein.

A drive shaft 14 is inserted through the front body 6 and is rotatably supported by bearings 16 and 18. 20 is the pump body 1
This is an oil seal that maintains the liquid tightness within 0. A rotor 22 is connected by a spline to a portion of the drive shaft 14 near the distal end inserted into the pump body 10. The drive shaft 14 is driven by an engine (not shown).
Is rotated, the rotor 22 is rotationally driven.

The rotor 22 is provided with radial slits 22a at regular intervals in the circumferential direction.
A vane 24 is fitted in 2a so as to be able to protrude and retract. A cam ring 26 having a substantially elliptical inner peripheral cam surface is disposed on the outer peripheral side of the rotor 22. The rotor 22 and the cam ring 26 are sandwiched between a pressure plate 28 and a rear body 8 disposed in the front body 6, and the rear body 8, the cam ring 26 and the pressure plate 28 are positioned in the rotation direction by a pin 30. I have.

The front body 6 and the rear body 8 are provided with a suction port 32 and suction passages 6a, 8a. Each pump formed by the two adjacent vanes 24, 24 passes through the passages 6a, 8a. Sucked indoors. The hydraulic oil sucked into the pump chamber is discharged into a discharge chamber 34 formed at the bottom of the front body 6 through a discharge passage 28a provided in the pressure plate 28.

A flow control device 1 is provided in the pump body 10 in a direction orthogonal to the drive shaft 14, and pressurized oil discharged from the pump chamber into the discharge chamber 34 is supplied to the supply passage 6b. Through the flow control device 1
Sent to The configuration of the flow control device 1 will be described with reference to FIG. 2 and FIG. The flow control device 1 includes a flow control valve 2 having a conventionally known configuration. First, the flow control valve 2 will be described. Valve body 6A formed integrally with pump body 6
A control spool 38 is slidably fitted in the valve hole 36, and a first pressure chamber 40 on the right side and a second pressure chamber on the left side in FIG. 4
It is divided into two.

The opening 36a of the valve hole 36 has a large diameter, and a connector 44 is screwed into the opening 36a. The inner end of the connector 44 faces the control spool 38, and the outer discharge port 44a is connected to a fluid device (not shown) (power steering device in this embodiment). A control spring 46 is disposed in the second pressure chamber 42 and constantly biases the control spool 38 toward the first pressure chamber 40. When the control spool 38 is not operated (the state shown in FIG. 2), the control spool 38 Is in contact with the tip of the connector 44.

At the tip of the control spool 38, a rod 48
Are provided integrally, and penetrate through a small-diameter hole 44 b formed on the inner surface of the connector 44. Rod 48
The control spool 38 has a large diameter at the tip end 48a.
A tapered portion 48b is formed between the tapered portion 48b and the smaller diameter portion 48c. A variable orifice 50 as a metering orifice is formed by the outer peripheral surface of the rod 48 and the inner surface of the small-diameter hole 44b of the connector 44. When the control spool 38 shown in FIGS. 50 has the largest opening area, and the tapered portion 48b and the large diameter portion 48c of the rod 48 move into the small diameter hole 44b of the connector 44 as the control spool 38 moves, so that the opening area gradually decreases.

In the first pressure chamber 40 in the valve hole 36, a supply passage 6b through which the pressure oil discharged to the discharge chamber 34 of the vane pump 4 is supplied is opened. This supply passage 6b
The pressure oil sent to the first pressure chamber 40 via the
4 enter the inside of the connector 44 through a plurality of radial passages 44c formed at the distal end, and are supplied to the power steering device (not shown) from the discharge port 44a through the variable orifice 50. A space 52 downstream of the variable orifice 50 in the connector 44 is connected to the second pressure chamber 42 via a radial orifice 54 formed in the connector 44 and an internal passage 56 formed in the valve body 6A. ing. Therefore, the differential pressure across the variable orifice 50 acts on both ends of the control spool 38, and when this differential pressure exceeds the spring force of the control spring 46, the control spool 38
Flexes the spring 46 and moves to the left in the figure.

A return passage 6c communicating with the pump suction side (tank 58 side) is open near the first pressure chamber 40 of the valve hole 36, and the control spool 38 is connected to the connector 44.
And the supply passage 6b and the recirculation passage 6c are shut off by the land 38a of the control spool 38, and when the control spool 38 moves due to a differential pressure across the variable orifice 50, the supply passage 6b The recirculation passage 6c communicates, and the degree of opening of the communication between the supply passage 6b and the recirculation passage 6c is controlled according to the movement position.

Further, the flow control device 1 is provided with a mechanism for changing a set load of a control spring 46 for urging the control spool 38 of the flow control valve 2. Next, this mechanism will be described. Control spool 3
8 is slidably fitted to the bottom of the valve hole 36 (second
A substantially cylindrical piston holding member 60 is fitted and fixed in the pressure chamber 42 side end (see FIG. 2; FIG. 3 omits illustration because the structure is shown in a simplified manner). ). A seal member 62 is fitted on the outer periphery of the holding member 60 to partition the space on the second pressure chamber 42 side and the bottom side of the valve hole 36 in a liquid-tight manner.

An inner hole 64 formed through the shaft center of the piston holding member 60 is provided with a large-diameter hole 64a on the bottom side (left side in FIGS. 2 and 3) of the valve hole 36 and the second pressure chamber 42 side. And a stepped piston 66 is fitted in the internal hole 64. Stepped piston 6
6 is slidably fitted in the large-diameter hole 64a of the internal hole 64, and the small-diameter portion 66b is formed in the small-diameter hole 64 of the internal hole 64.
It is slidably fitted in b. Further, a small diameter portion 66c formed at the tip of the small diameter portion 66b of the stepped piston 66
Project from the internal hole 64 of the piston holding member 60 into the second pressure chamber 42.

The tip small diameter portion 66 of the stepped piston 66
c, a control spring 4 for urging the control spool 38 toward the first pressure chamber 40 side.
6 and is supported in contact with one end. Spring support ring 6
The stepped piston 6 is pushed by the spring 46
6 is locked at a step between the small diameter portion 66b and the tip small diameter portion 66c.

The stepped piston 66 is formed with a passage hole 70 penetrating the shaft core. Through this passage hole 70, a chamber 72 (behind the large diameter portion 66a of the stepped piston 66) is formed. The pressure in the second pressure chamber 42, that is, the pressure on the pump discharge side downstream of the variable orifice 50 is introduced into the space (left end space in the drawing). Further, a chamber 74 defined by a stepped portion between the large-diameter portion 66a and the small-diameter portion 66b of the stepped piston 66 and the inner surface of the large-diameter hole 64a of the piston holding member 60 is provided with a passage 7 formed in the valve body 6A.
6 and the like, and connected to the tank 58 side. The pressure introduced into the chamber 74 is not limited to the tank pressure, but may be any pressure lower than the pressure on the downstream side of the variable orifice 50.

The same fluid pressure (fluid pressure on the downstream side of the variable orifice 50, that is, the operating pressure of the power steering device) acts on both end surfaces of the stepped piston 66, and the operating pressure is higher than a predetermined value. Then, the large diameter portion 66a and the small diameter portion 6
6b, the piston 66 flexes the control spring 46 and moves rightward in the figure. In this embodiment, the spring force of the control spring 36 is set so that the piston 58 does not move until the operating pressure of the power steering device reaches, for example, 0.6 MPa (see FIG. 7). When the operating pressure rises, the piston 66 further advances in accordance with the pressure, and the end surface of the large-diameter portion 66a on the small-diameter portion 66b side (the right end surface in the drawing) is formed by the small-diameter hole 64b and the large-diameter hole 64a of the piston holding member 64. When it hits the step 64c (stopper surface) between the steps, it stops. In this embodiment, the piston 66 is set to stop when the operating pressure of the power steering device reaches, for example, 1.5 MPa. Reference numeral 77 in the drawing denotes a passage 5 formed in the valve body 6A.
It is a plug that closes 6,76 openings.

A relief valve 78 is provided inside the spool 38 so that the pressure in the second pressure chamber 42 (the pressure on the downstream side of the variable orifice 50, in other words, the operating pressure of the power steering device) is predetermined. When the fluid pressure rises as described above, the fluid pressure is released and released to the tank 58 side. At the time of relief, a flow velocity is generated, so that a pressure drop is generated by the orifice 54. Then, the pressure difference between both ends of the spool 38 increases, and the spool 38 moves to the left in FIG. 2 to increase the area of communication with the return passage 6c to return most of the fluid to the tank.

Next, the operation of the vane pump 4 having the flow control device 1 will be described. When an engine (not shown) is started, the rotor 22 connected to the drive shaft 14 rotates. Therefore, according to the engine speed,
The vane pump 4 sucks fluid from the suction port 32 and the suction passages 6a and 8a connected to the tank 58, and discharges the fluid from the discharge passage 28a to the discharge chamber 34. Then, the discharge fluid is guided from the supply passage 6b to the first pressure chamber 40 of the flow control valve 2. The fluid introduced into the first pressure chamber 40 is
The connector 44 enters the connector 44 through the radial passage 44c and passes through the variable orifice 50 to the discharge port 44a.
To a power steering device (not shown).

At this time, a pressure difference occurs before and after the variable orifice 50. Then, the pressure on the upstream side acts on the end of the control spool 38 on the first pressure chamber 40 side, and
The downstream pressure acts on the end of the control spool 38 on the second pressure chamber 42 side. However, the spool 38 does not move due to the spring force of the control spring 46 until the pressure difference before and after the variable orifice 50 reaches a certain magnitude, that is, until a certain pump discharge amount is reached. The passage 6c is shut off. Therefore, all of the discharge amount from the pump 4 is supplied to the power steering device.

As the engine speed gradually increases and the pump discharge rate increases, the pressure difference between the front and rear of the variable orifice 50 increases. Figure 2 against
Move to the left of. Then, the spool 38 stops at a position where the pressure difference acting on both ends of the control spool 38 and the spring force of the spring 46 are balanced, and the supply passage 6b and the return passage 6c communicate with each other at an opening corresponding to this position. Become
The discharge fluid from the pump 4 is returned to the return passage 6 according to the opening degree.
c.

When the vehicle is running straight without steering operation, the load pressure on the power steering device is low and the stepped piston 6
2 and 3 is stopped at the position shown in FIGS. 2 and 3, so that the control spring 46 has the longest set length and controls the operation of the control spool 38 with a low spring load. ing. Therefore, the variable orifice 50
When the pressure difference between before and after is small, that is, when the amount of discharge from the pump is small, the control spool 38 operates and balances, and the supply flow rate to the power steering device is made constant. In this embodiment, the supply flow rate when traveling straight ahead is set to 4.5 l / min (see the broken line in FIG. 6).

In this embodiment, since the variable orifice 50 is used as the metering orifice, it has the characteristic that the higher the engine speed, the smaller the flow rate supplied to the power steering device. That is, when the pump discharge amount increases, the differential pressure before and after the variable orifice 50 increases, and the control spool 38 further moves as shown in FIGS.
Move to the left of. Then, the opening degree of the variable orifice 50 decreases, and the differential pressure before and after the opening increases.

When the steering operation is performed, the operating pressure of the power steering device increases. When the operating pressure reaches a predetermined level or more, the large-diameter portion 66 of the stepped piston 66 on which the operating pressure acts.
The piston 66 flexes the spring 46 and moves to the right in the figure due to the area difference between the pressure receiving portion a and the small-diameter portion 66b. In this embodiment, the piston 58 starts moving at about 0.6 Mpa (see FIG. 7). When the control spring 46 is compressed by the movement of the piston 58, the spring load increases, and the differential pressure across the variable orifice 50 that operates the spool 38 increases. Therefore, pump 4
And the flow rate required for steering the power steering device can be secured. The solid line in FIG. 6 shows an example of such a discharge flow rate, which is the maximum flow rate required in sudden steering (in this example, 7 l / min).

When the operating pressure of the power steering device further increases, the front surface (the right end surface in the figure) of the large-diameter portion 66a of the stepped piston 66 becomes the stopper surface 6 of the piston holding member 60.
4c, so that the thrust by the piston 66 is not further transmitted to the control spool 38.
In this embodiment, the piston 66 is set to stop when the operating pressure of the power steering device reaches, for example, 1.5 MPa. Therefore, even if the working pressure (pump discharge oil pressure) of the power steering device further rises, the flow rate does not increase as shown in FIG.

As described above, in the flow control device 1 according to the present embodiment, when the vehicle travels straight, the piston 66 remains stopped at the left end in FIG. Since the load is low, the discharge flow rate to the power steering device can be reduced, and the energy consumption of the pump can be reduced. Moreover, when the steering operation is performed, the discharge flow rate can be quickly recovered by using the generated operating hydraulic pressure of the power steering device, and the flow rate required for steering can be supplied. In particular, as compared with the conventional configuration described in the above-mentioned publication, the piston 66 is pressed by a spring different from the spring that biases the control spool, and the piston 66 accommodates the switching spool inside. Therefore, the size can be significantly reduced, and the weight and cost can be reduced. Further, the downsizing of the piston 66 enables quick operation, allows the flow rate to be recovered in a short time, and prevents the steering wheel from being caught during sudden steering.

FIG. 4 is a diagram showing a flow control device 101 according to the second embodiment. The flow control device 101 according to the first embodiment has the same basic configuration as that of the flow control device 1 according to the first embodiment. Or, corresponding parts are denoted by the same reference numerals, description thereof will be omitted, and only different parts will be described.

In the first embodiment, the spring 4
6 (the right end in FIGS. 2 and 3)
8, while the other end is in contact with a spring receiving ring 68 which is locked to a step between the small diameter portion 66b and the tip small diameter portion 66c of the stepped piston 66. In this embodiment, dual inner and outer springs 146 and 147 are arranged in the spring chamber 42. One end (right end in FIG. 4) of the inner spring 146 is similar to the spring 46 of the first embodiment, and
The other end of the end face 8 is in contact with a spring receiving ring 68 locked to a stepped piston 66. One end (the right end in FIG. 4) of the outer spring 147 has a control spool 38.
The other end is in contact with the bottom surface 36a of the valve hole 36 formed in the valve body 6A (the side surface in the configuration in which the piston holding member 60 is provided as shown in FIG. 2).

The outer spring 147 has a low spring constant so that the variation in set load can be reduced even if the set length varies, and the variation in flow rate during non-steering and the variation in differential pressure in the metering orifice 50 can be reduced. Can be held down. Further, the inner spring 146 is set to a spring constant such that the piston 66 generates a predetermined displacement when the fluid pressure on the power steering device side rises to a predetermined pressure during steering. Other configurations are the same as those of the first embodiment.

In the configuration of this embodiment, the same operation as in the first embodiment is performed, and the same effect can be obtained. Further, in the first embodiment, a single spring 46 sets the differential pressure across the metering orifice 50 for operating the control spool 38, and the thrust of the piston 66 moved by the operating pressure of the power steering device. Is transmitted to the spool 38, so that the set load of the spring 46 is required to be high precision. In this embodiment, as described above, the set load of the springs 146 and 147 is limited. High precision is not required.

FIG. 5 is a view showing a flow control device 201 according to a third embodiment. A stepped piston 266 of this embodiment has a small-diameter portion 266b extending inward of the valve hole 36. The small-diameter portion 266b of the piston faces the end surface of the control spool 38 on the spring 247 side. Further, behind the large diameter portion 266a of the piston 266 (left side in FIG. 5), the small diameter portion 2 on the spring chamber 42 side is provided.
A small diameter portion 266d having the same diameter as 66b is formed, and this rear small diameter portion 266d is slidably fitted into a small diameter hole 264c continuous behind the large diameter hole 264a formed in the valve body 6A. ing.

A through hole 270 is formed in the axis of the stepped piston 266, and a through hole 270 is formed in the second pressure chamber 42 accommodating the spring 247 and the bottom of the small diameter hole 264c in which the rear small diameter portion 266d is fitted. The pressure in the second pressure chamber 42, that is, the pressure on the downstream side of the variable orifice (metering orifice) 50 is introduced into the bottom space 280, and the two ends of the piston 266 are connected to each other. The same pressure is applied.

A space 282 (hereinafter referred to as a working pressure chamber) around a step between a large diameter portion 266a formed at the center of the stepped piston 266 and a rear small diameter portion 266d is provided through an introduction passage 284. Thus, the fluid pressure on the power steering device side is introduced. The tank-side fluid pressure is introduced into the chamber 286 around the step between the large-diameter portion 266a and the front-side small-diameter portion 266b.

In the middle of the introduction passage 284, a switching valve 288 is provided.
Is provided. The switching valve 288 includes a spool valve body 292 slidably fitted in a valve hole 290 formed in the valve body 6A, and a spring 294 for urging the spool valve body 292. The chamber 296 containing the spring 294 is connected to the tank via a passage 276. The chamber 298 at the end (right side in FIG. 5) opposite to the chamber 296 in which the spring 294 is accommodated in the valve hole 290 is located downstream of the introduction passage 284.
The working pressure chamber 282 behind the large-diameter portion 266a of the piston is connected via 84B.

An annular groove 292 a is formed on the outer periphery of the intermediate portion of the spool valve body 292 of the switching valve 288.
a and the end chamber 298 connected to the working pressure chamber 282 communicate with each other through an internal passage 292b. Therefore, FIG.
As shown in (a), when the spool valve body 292 is stopped at the non-operation position by being pushed by the spring 294,
Through the introduction passage 284 (the upstream portion 284A), the valve hole 2
The hydraulic pressure on the power steering device side introduced into the cylinder 90 is passed through the annular groove 292 a of the spool valve body 292, the internal passage 292 b, the end chamber 298, and the downstream portion 284 B of the introduction passage 284, and the piston large diameter portion 266 a Is introduced into the working pressure chamber 282 on the rear side of

When the operating pressure of the power steering device rises above a predetermined value, the spool valve body 292
5b (see FIG. 5B), and the annular groove 292a and the upstream portion 284A of the introduction passage 284 are shut off. Note that the fluid pressure utilization device has a slight pressure loss due to pipe resistance and the like even when there is no load, and this power steering device has a loss of about 0.3 Mpa. The spring 294 force is set so that the spool valve element 292 does not operate until the operating pressure becomes, for example, 0.5 MPa.

In this embodiment, at the time of non-steering, as in the first embodiment, when the pump rotation speed increases and the pressure difference before and after the metering orifice 50 increases, the control spool 38 causes the spring 247 to operate. It bends and moves to the left in the figure, connects the first pressure chamber 40 upstream of the metering orifice and the return passage 6c as described above, and returns the discharge oil from the pump 4 to the tank.

When the steering operation is performed in this state, the pressure on the power steering device side increases. The operating pressure on the power steering device side enters the second pressure chamber 42 containing the spring 247 at the left end of the spool 38 from the internal passage 56 of the valve body 6A, and the upstream portion 28 of the introduction passage 284.
4A, annular groove 292a of spool valve body 292, internal passage 292b, end chamber 298 of valve hole 290 and introduction passage 2
It is also introduced into the working pressure chamber 282 formed behind the large diameter portion 266a of the piston 266 via the downstream portion 284B of the piston 84. When the operating pressure of the power steering device exceeds a predetermined value,
Due to the pressure receiving area difference between the large diameter portion 266a and the small diameter portion 266b of the piston 266 on which this pressure acts, the piston 266
Goes to the right. When the piston 266 moves, the thrust is not applied to the control spool 38 via the springs 46 and 146 as in the above-described embodiments.
6 directly presses the spool 38 and moves it to the right in FIG. 5 to reduce the opening area of the return passage 6c.

In this embodiment, the operation is the same as in each of the above embodiments, and the same effects can be obtained. Further, the spring 247 for urging the control spool 38
The spring constant is reduced, and even when the set length varies, variation in the flow rate during non-steering can be suppressed. Further, since the piston 266 directly pushes the spool 38 without passing through the spring 247, the discharge flow rate can be quickly restored at the time of steering, and the flow rate required for steering can be supplied to the power steering device.

In the flow control device 1 according to the first embodiment (see FIGS. 2 and 3), the passage hole 70 is formed inside the stepped piston 66 so that the passage hole 70 is formed in the large-diameter chamber 72. Although the pressure on the downstream side of the orifice 50 is introduced, this passage hole 70 is not provided, and the large-diameter side of the piston 66 is provided through a switching valve 288 similar to that of the third embodiment (see FIG. 5). The pressure downstream of the orifice 50 can also be introduced into the chamber 72. In this case, when the operating pressure of the power steering device rises to a predetermined value or more, the switching valve 288 operates to cut off the introduction of the pressure fluid to the large diameter side of the piston 66, and
Do not move 6 any further.

Further, the present invention is not limited to the structure described in the above embodiment, and it goes without saying that the shape, structure, etc. of each part can be appropriately modified and changed. Also,
In the above embodiment, the vane pump used as a hydraulic source of the power steering device mounted on the vehicle has been described, but the present invention is not limited to this, and the pressure may be increased or decreased by increasing or decreasing the supply flow rate from the pump as necessary. While ensuring the reliability of the operation of the fluid utilization device, the pump power is reduced,
It is applicable as long as it can exert the energy saving effect.

[0066]

As described above, according to the present invention, a stepped piston is disposed on the opposite side of the spool with the spring interposed therebetween, and one end of the spring is brought into contact with the small-diameter end of the piston. Since the pressure downstream of the orifice is applied to the radial end and a pressure lower than the pressure downstream of the orifice is introduced into the chamber formed at the step between the large-diameter portion and the small-diameter portion of the piston. When the vehicle is traveling straight, the spring load of the spring that biases the spool is reduced to reduce the discharge flow rate to the fluid device,
The energy consumption of the pump can be reduced, and at the time of steering, the generated operating pressure of the fluid device can be used to quickly recover the pump discharge flow rate, thereby ensuring the flow rate required for the operation of the fluid device. In addition, since the stepped piston is directly operated by the pressure receiving area difference to press the spring, the piston can be miniaturized, and the size, weight and cost can be reduced as compared with the conventional flow control device. it can.
In addition, since the piston can be downsized, the amount of fluid required for its operation is small, so that quick operation is possible, and the flow rate can be recovered in a short time. Therefore, for example, it is possible to prevent the steering wheel from being caught at the time of sudden steering of the power steering device.

According to the third aspect of the present invention, a stepped piston is disposed on the opposite side of the spool across the spring, the small-diameter end is extended toward the spool, and the large-diameter end is provided with the stepped piston. A pressure lower than the pressure downstream of the orifice is introduced into a chamber formed at the step between the large diameter portion and the small diameter portion of the piston while applying a pressure downstream of the orifice. When the piston moves, the small-diameter end of the piston is brought into direct contact with the spool to apply an axial thrust.
The same effects as those of the first aspect can be obtained. Further, the spring constant of the spring for urging the spool can be reduced, and even when the set length varies, the variation in the flow rate during non-steering can be suppressed. Further, since the piston directly pushes the spool without using a spring, the steering spool can be quickly and surely pressed during steering to increase the discharge flow rate of the pump.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a vane type oil pump provided with a flow control device according to one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of the flow control device.

FIG. 3 is a schematic structural diagram showing a simplified flow control device of FIG. 2;

FIG. 4 is a schematic structural view showing a simplified flow rate control device according to a second embodiment.

FIG. 5 (a) is a schematic structural view showing a simplified flow control device according to a third embodiment, and FIG. 5 (b) is a diagram showing the flow control device when the switching valve is operated.

FIG. 6 is a diagram showing flow characteristics of the flow control device.

FIG. 7 is an example of a diagram showing a relationship between a discharge oil pressure and a flow rate at a pump rotation speed of 1000 rpm in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow control apparatus 2 Flow control valve 4 Pump 6A Valve body 36 Valve hole 38 Spool 40 1st pressure chamber 42 2nd pressure chamber 46 Spring 50 Orifice 58 Tank 66 Stepped piston

Claims (4)

[Claims] 1. A valve hole formed in a valve body, a spool slidably fitted in the valve hole, and a pressure fluid discharged from a pump defined at one end of the spool. A first pressure chamber to be introduced, an orifice provided in a supply passage of a pressure fluid discharged from the pump and supplied to the fluid device, and a downstream side of the orifice defined at the other end of the spool. And a spring housed in the second pressure chamber and biasing the spool toward the first pressure chamber. The differential pressure across the orifice activates the spool. A flow control device for recirculating fluid from the first pressure chamber to a tank, wherein a stepped piston is disposed on the opposite side of the spool with the spring interposed therebetween, and one end of the spring is brought into contact with a small diameter end thereof; Applying the pressure downstream of the orifice to the large-diameter end, and introducing a pressure lower than the pressure downstream of the orifice into a chamber formed at the step between the large-diameter portion and the small-diameter portion of the piston. Characteristic flow control device. 2. The flow control device according to claim 1, wherein a second spring is disposed on an outer peripheral side of the spring.
A flow control device, wherein one end of the flow control device is in contact with an end surface of the spool, and the other end is in contact with an end surface of a valve hole. 3. A valve hole formed in a valve body, a spool slidably fitted in the valve hole, and a pressure fluid discharged from a pump defined at one end of the spool. A first pressure chamber to be introduced, an orifice provided in a supply passage of a pressure fluid discharged from the pump and supplied to the fluid device, and a downstream side of the orifice defined at the other end of the spool. And a spring housed in the second pressure chamber and biasing the spool toward the first pressure chamber. The differential pressure across the orifice activates the spool. A flow control device for recirculating a fluid from a first pressure chamber to a tank, wherein a stepped piston is disposed on the opposite side of the spool with the spring interposed therebetween, a small-diameter end thereof is extended to the spool side, and a large-diameter end is provided. Before A pressure lower than the pressure downstream of the orifice is introduced into a chamber formed at the step between the large diameter portion and the small diameter portion of the piston while applying a pressure downstream of the orifice. A flow control device characterized in that when the piston moves, a small-diameter end of the piston directly abuts the spool to apply an axial thrust. 4. The flow control device according to claim 1, wherein a switching valve is provided at a large-diameter end of the piston in an introduction passage for guiding fluid pressure downstream of the orifice. A flow control device, wherein the introduction passage is shut off when the pressure becomes equal to or higher than a predetermined value.