JPH0121109Y2 - - Google Patents

Description

[Detailed description of the invention] The invention provides an orifice in the supply passage that feeds the working fluid supplied from the fluid pump to the power steering device, and the working fluid is increased before and after the orifice by increasing the pump rotation speed. The present invention relates to a flow rate control device for a power steering device that allows surplus working fluid to flow back to the suction side of a fluid pump through a bypass passage in response to a pressure difference caused by an increase in supply amount.

Conventionally, in a flow rate control device having the above function, a throttle passage is formed upstream of the orifice in the supply passage, and a control spool that is displaced according to the pressure difference generated before and after the throttle passage is coaxially disposed upstream of the orifice. A device has been proposed in which the orifice's throttling action is variably controlled by the shaft end of the control spool.

The flow rate control device having such a configuration has a pump rotation speed N
It has a flow rate characteristic shown in graph A in Figure 1, and when a large steering torque is required, such as when the power steering device is stationary or when the vehicle is running at low speed, a
The range of flow characteristics from ~b (supply flow rate Q ₁ ) is used, and when a large steering torque is not required, such as when the vehicle is running at high speed, the range of flow characteristics after c (supply flow rate Q 1 ) in which the flow rate is reduced is used. ₂ ) is becoming increasingly used. Therefore, when the vehicle is running at high speed, the reduction in the supply flow rate allows the driver to enjoy steering reaction force, improving high-speed stability, and reducing power loss to save energy.

However, in the above conventional device, the orifice is composed of an orifice center hole and an orifice side hole formed around the orifice center hole, and on the other hand, the control spool has a hole in the center that closes the orifice center hole. Since it has a structure in which a contact surface is formed and flow holes are opened on both sides of this contact surface, the flow path resistance differs due to the difference in phase between the flow hole and the orifice side hole. As shown, there was a problem in which there was a difference between flow rate characteristic A when the phases of both holes matched and flow rate characteristic B when a 90 degree phase difference occurred between both holes.

The present invention was devised to eliminate such conventional problems, and its purpose is to provide a control spool or a contact member that contacts the control spool with a center hole located on the same axis as the orifice center hole. In addition, a communication hole is formed in which communication with the orifice side hole is cut off by the contact between the two, thereby making it possible to obtain constant flow rate characteristics regardless of changes in the phase of the control spool. be.

The present invention will be explained below based on the drawings.

FIG. 2 shows an embodiment of a flow rate control device according to the present invention. In this embodiment, a flow rate control device 20 is incorporated in a pump housing 10 of a fluid pump, and the flow rate control device 20 is a union 21, a spool valve 22 for flow rate adjustment, a control spool 23, and a contact member 24 are the main components.

This pump housing 10 is provided with a storage hole 11 passing through it, a union 21 is screwed into one end of the storage hole 11 in a fluid-tight manner, and a stopper 25 is attached to the other end of the storage hole 11. are fitted in a liquid-tight manner. The union 21 has a substantially cylindrical shape, and its inner end is loosely fitted into the storage hole 11, and the supply passage 12 provided in the pump housing 10 is accommodated between the outer periphery of the inner end and the inner periphery of the storage hole 11. A throttle passage 31 is formed that constantly communicates with the inside of the hole 11. This throttle passage 31 is designed so that when the discharge flow rate of the working fluid supplied to the supply passage 12 increases, a pressure difference is generated between the upstream side and the downstream side, that is, between the supply passage 12 and the storage hole 11 due to the passage resistance. It acts on
The outer end opening 21a of the union 21 is connected to a normally open servo valve device of a power steering device, and the supply passage 12 is communicated with a discharge chamber of a fluid pump.

The spool valve 22 is connected to the union 2 in the storage hole 11.
1 and the stopper 25, and a first valve chamber 32 and a second valve chamber 33 are provided in the storage hole 11.
is formed. Further, the spool valve 22 is biased by a spring 26 interposed in the second valve chamber 33 and elastically abuts on a control spool 23 (described later), so that the spool valve 22 is connected to the supply passage 12 and the bypass passage 13 provided in the pump housing 10. communication is cut off. Note that the bypass passage 13 communicates with the suction chamber of the fluid pump.

The control spool 23 is slidably inserted into the inner hole of the union 21, and is supported by a spring 27 interposed between the control spool 23 and the contact member 24 fitted to the outer end of the inner hole of the union 21. It is biased and resiliently abuts against the inner end step 21b of the inner hole of the union 21. This control spool 23 has a first valve chamber 3
2 and a cavity 34 between the control spool 23 and the contact member 24 are formed.
The first valve chamber 32 and the outer end opening 21a of the union 21 are communicated through the orifice center hole 24a and the orifice side hole 24b.
Further, on the end surface of the stepped portion 23b of the control spool 23,
A pressure introduction hole 21c provided in the union 21 is open. This pressure introduction hole 21c communicates with the supply passage 12, and causes the control spool 23 to slide against the spring 27 when the supply pressure exceeds a predetermined pressure.

The contact member 24 includes an orifice center hole 24a and an orifice side hole 24b, which will be described later, as well as a control nozzle 24c.
1 and a communication hole 2 provided in the pump housing 10
It communicates with the second valve chamber 33 through 1d and 14. As a result, a part of the downstream fluid of the orifice center hole 24a and the orifice side hole 24b is guided into the second valve chamber 33, and the orifice center hole 24b and the orifice side hole 24b are formed on both end surfaces of the spool valve 22. Front and rear pressures act, and the spool valve 22 moves in the axial direction according to this differential pressure, adjusting the opening degree of the bypass passage 13 to maintain the differential pressure constant.

As shown in FIG.
is formed, and a plurality of orifice side holes 2 are formed on the outer periphery of the orifice center hole 24a.
4b is formed. On the other hand, the control spool 23
A protrusion 23c is formed at the shaft end, and the communication hole 23a is opened in this protrusion 23c. The opening 23d of the communication hole 23a is opened so as to face the orifice center hole 24a and align with the axis of the orifice center hole 24a,
Further, the area around the opening 23d of the communication hole 23a is in contact with the orifice forming member 24,
An annular contact surface 23e is formed that blocks communication between the orifice side hole 24b and the orifice side hole 24b.

In the flow control device configured in this way,
When the fluid pump is driven by the vehicle engine,
The working fluid is supplied from the discharge chamber of the fluid pump to the supply passage 12
is supplied to The supplied working fluid is supplied to the first valve chamber 32 through the throttle passage 31, and from the first valve chamber 32 to the circulation hole 23a and the orifice center hole 24.
It is fed from the outer end opening 21a of the union 21 to the power steering device via the orifice side hole 24b.

By the way, when the rotational speed of the fluid pump is low, the discharge flow rate of the working fluid is small, so the spool valve 22 closes the bypass passage 13 and directs the entire amount of working fluid to the power steering through the orifice center hole 24a and the orifice side hole 24b. When the discharge flow rate of the working fluid increases as the rotational speed of the fluid pump increases, the spool valve 22 slides to keep the differential pressure before and after the orifice center hole 24a and orifice side hole 24b constant. The bypass passage 13 is moved to open the bypass passage 13 and the excess flow of working fluid is returned through the bypass passage 13 to the suction chamber of the fluid pump. As a result, the working fluid supplied to the power steering device is maintained at a predetermined amount _Q1 shown in FIG. 1 determined by the orifice center hole 24a and the orifice side hole 24b.

Further, when the rotational speed of the fluid pump further increases as the vehicle moves to high-speed running, and the discharge flow rate of the working fluid supplied to the supply passage 12 increases, the flow resistance in the throttle passage 31 causes the inside of the supply passage 12 to increase. The fluid pressure of the supply passage 12 and the first valve chamber 3 increases.
A differential pressure is generated between the two, and the pressure in the supply passage 12 is transferred to the control spool 23 through the pressure introduction hole 21c.
acts as a pressing force that causes the spring 27 to slide against the spring 27. Therefore, the pressure in the supply passage 12 is increased by the spring 27 in response to an increase in the discharge flow rate of the working fluid.
When the force increases until it overcomes the biasing force of , the control spool 2
3 gradually slides against the spring 27, and finally the annular contact surface 23e contacts the contact member 24 to cut off communication between the flow hole 23a and the orifice side hole 24b. As a result, the working fluid supplied to the power steering system is maintained at a reduced flow rate _Q2 shown in FIG. 1 determined by the orifice center hole 24a.

Therefore, according to the flow control device, when the vehicle is running at high speed, the flow rate of the working fluid supplied to the power steering device can be reduced, allowing the driver to enjoy the steering reaction force, and improving high speed stability. .

When performing such flow rate control, since the working fluid flows out from the flow hole opening 23d that is opened coaxially with the orifice center hole 24a, the passage resistance is reduced depending on the assembly phase of the control spool 23. does not change, and a constant flow rate characteristic can always be obtained as shown in FIG. 1A.

Note that the present invention is not limited to the above-mentioned embodiment, and for example, as shown in FIG. A hole 24f may be formed. Also in this embodiment, the flow hole 24f is the orifice center hole 23f.
Since the control spool 23 is formed on the same axis as the control spool 23, the characteristics do not change depending on the assembly phase of the control spool 23.

As explained above, the flow rate control device of the present invention is
Since the flow hole and the orifice center hole are coaxially opened, the relationship between the flow hole and the orifice side hole does not change at all even if the control spool is assembled at any angular phase, keeping the flow characteristics constant. It has the advantage of being able to maintain

[Brief explanation of the drawing]

FIG. 1 is a graph showing the flow rate characteristics with respect to the pump rotation speed in a flow rate control device, FIG. 2 is a sectional view showing an embodiment of the flow rate control device according to the present invention, and FIG. 3 is a sectional view taken along the - line in FIG. FIG. 4 is a partially sectional view showing another embodiment of the present invention. 10...Pump housing, 11...Storage hole,
12... Supply passage, 13... Bypass passage, 20
...Flow control device, 21...Union, 22...
Spool valve, 23... Control spool, 23a...
Flow hole, 23d...opening, 23e...annular contact surface, 24...orifice forming member, 24a...orifice center hole, 24b...orifice side hole, 31...throttle passage, 32, 33...valve Room.

Claims (1)

[Scope of utility model registration request] An orifice interposed on a supply passage for feeding working fluid supplied from a fluid pump to a power steering device; and an orifice slidably fitted into a storage hole to generate fluid before and behind the orifice. a bypass passage that is divided into first and second valve chambers into which pressure is introduced, and is displaced according to the pressure difference between the first and second valve chambers to circulate excess working fluid to the suction side of the fluid pump; A flow control device comprising a flow rate adjustment spool that adjusts the opening degree of the orifice, and a control spool that is displaced according to the pressure difference before and after the throttle passage on the upstream side of the orifice. The orifice center hole is formed in the center of the control spool or one of the contact members that comes into contact with the control spool, and the orifice side is formed on the circumference around the orifice center hole. A hole is formed in the other of the control spool or the contact member, and the control spool or the contact member has a hole located on the same axis as the orifice center hole, and communicates with the orifice side hole by contact between the control spool and the contact member. A flow control device characterized by forming a flow hole that is blocked.