JPH0624944B2 - Flow control valve - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flow rate control device applied to a power steering device or the like of an automobile and adjusting a flow rate of a working fluid supplied from a power source to the power steering device or the like to a predetermined flow rate. .

(Prior Art) An oil pump as a power source that supplies a working fluid to a power steering device that assists a manual steering torque by using a fluid as a working medium is usually rotationally driven by an internal combustion engine mounted on a vehicle, The discharge flow rate increases due to the increase in the rotation.

However, the flow rate required for power steering operation needs to be ensured in a relatively low speed region of the engine because the operation is sufficient if the operation is sufficiently performed when the vehicle is stopped or running at low speed. It doesn't need much. Therefore, it is usual to bypass the excess flow rate generated by the high speed rotation by the flow rate control valve and return it to the reservoir tank or the like.

As a flow control valve of this kind, the applicant of the present application, as shown in FIG. 1, is a variable orifice sub-orifice in which a main orifice 3 communicating with an introduction passage 2 for guiding the discharge oil from the pump 1 is arranged in series therewith. 4 to communicate with the power steering device 5 via the sensitive orifice 6 and the passage 7 to cause the sub-spool 8 to use the pressure before and after the main orifice 3, respectively, so that the sub-spool 8 is generated before and after the main orifice 3. While controlling the sub-orifice 4 by responding to the differential pressure, a main spool 9 that responds to the differential pressure generated before and after the sub-orifice 4 is fitted with a drain passage 10 communicating with a reservoir tank (not shown). is suggesting.

The discharge flow rate characteristic of this flow control device is as shown in FIG. 5 (b). The hydraulic oil discharged from the pump 1 passes through the main orifice 3 and the sub-orifice 4 while flowing into the sub-orifice 4. Due to the increase in the differential pressure before and after passing through the sub-orifice 4 due to the increase in the operating oil, the main spool 9 is moved to the right against the spring force of the balance spring 11 to open the drain passage 10, and a part of it is drained. aisle
Escape to 10. Thus, the hydraulic oil delivered to the power steering device 5 is maintained at a constant flow rate Q2 under the control of the main orifice 3 and the sub-orifice 4. When the pump discharge rate further increases, the sub spool 8 is actuated against the spring force of its balance spring 12 due to the further rightward movement of the main spool 9 and the increase in the differential pressure generated before and after the main orifice 3. , Sub-orifice 4
Squeeze. With this series of operations, the power steering device 5
The flow rate delivered to the air flow rate is gradually reduced from the constant flow rate Q2, and is mainly caused by passing through the sub-orifice 4.
1, so-called flow-down control is performed.

By the way, in the above-mentioned conventional example, when the main spool 9 is moved, the pump discharge is a main orifice 3 having a fixed throttle.
Since it is configured to pass through and escape to the drain passage, the pressure in the introduction passage 2 due to the resistance generated by the main orifice 3 rises and the pump 1 is forced to perform unnecessary work, that is, energy loss and oil deteriorate. There was a problem.

(Object of the Invention) The present invention has been made in view of the above problems,
A flow control valve is provided in which the opening area of the orifice through which the entire amount of the fluid flowing into the introduction passage passes is variable according to the flow rate of the fluid flowing into the introduction passage, and the pressure loss of the fluid circuit due to this flow control valve is reduced. At the same time, the purpose is to prevent an increase in fluid temperature due to an increase in fluid pressure.

(Structure of the Invention) A flow control valve according to the present invention is slidably housed in a housing hole 21a formed in a housing 23, and the inside of the housing hole is divided into a primary pressure chamber 36 and a secondary pressure chamber 37. Main spool 35
And an introduction passage 23a formed in the housing for introducing oil discharged from the pump 24 into the primary pressure chamber via the introduction orifice 30, and communicating with the primary pressure chamber via the main orifice 32. A discharge passage 23c for supplying hydraulic oil to the side, and feedback passages 22c, 21b, 35b, 38 for connecting the discharge passage and the secondary pressure chamber,
A drain passage 23b for discharging the working oil of the primary pressure chamber to a low pressure side in accordance with the sliding amount of the main spool that slides according to the pressure difference between the primary pressure chamber and the secondary pressure chamber, The main spool is driven according to the pressure increase in the primary pressure chamber accompanying the increase in the discharge amount, and the discharge amount from the primary pressure chamber to the drain passage is increased to control the supply amount of hydraulic oil from the main orifice to the discharge passage. A sub-spool that is a flow control valve and has a large diameter portion on the outer periphery and is formed in a tubular shape as a whole.
28 is slidably fitted in the housing hole of the housing, and a control chamber 31 is defined between the step portion having a large diameter and the housing to communicate the control chamber with the introduction passage. ,
It is made variable by the movement of the sub spool accompanying the pressure increase in the control chamber.

(Operation) In the flow control valve of the present invention, in the high flow rate region of the fluid flowing into the introduction passage, the opening area of the introduction orifice increases as the flow rate of the fluid flowing into the introduction passage increases.
Therefore, the pressure loss of the fluid circuit due to the flow control valve is reduced, the pump load is reduced, and the rise in fluid temperature due to the rise in fluid pressure is prevented.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention applied to a power steering device for a vehicle and is a sectional view of a flow control valve.

First, the structure will be described. In the figure, reference numeral 21 is a casing in which a housing hole 21a extending in the left-right direction in which the left end is opened is formed, and 22 is a hollow connector in which a hole 22a is formed. 22 is screwed into the opening end of the housing hole 21a of the casing 21, and together with the casing 21, the valve housing
Functions as 23. The casing 21 is formed with an introduction passage 23a and a drain passage 23b which open to the accommodation hole 21a,
The introduction passage 23a is connected to the discharge port of the pump 24, and the drain passage 23b is connected to the suction port of the pump 24.
The pump 24 is driven by an on-vehicle engine (not shown) to pressurize and discharge the fluid in the reservoir 25, and discharges a fixed amount of fluid per one rotation of its rotating shaft. Connector 22
Has a discharge passage 23c at the left end of the hole 22a in the figure,
The discharge passage 23c is connected to an actuator of a power steering device (not shown) via a control valve (four-way switching valve).

The connector 22 is fitted with an introduction orifice forming member 26 having a hollow hole 26a formed at the right end in the figure. The introduction orifice forming member 26 has a protrusion 26b formed on the inner peripheral surface at the right end in the drawing, which engages with a sub spool described later, and also has a through hole 26c penetrating the inner surface and the outer surface and a left-right direction in the drawing. An extending notch 26d is formed. Further, a plug 27 having a through hole 27a formed on the left side of the drawing is fitted into the hole 22a of the connector 22, and a substantially cylindrical sub spool 28 having a communication hole 28a is slidable. A spring 29 is inserted between the plug 27 and the sub-spool 28 so as to urge the sub-spool 28 to the right in the figure. The sub-spool 28 has a right end in the figure slidably inserted into the protrusion 26b to form an introduction orifice 30 together with the notch 26d, and also to form a control chamber 31 with the peripheral wall of the hole 22a of the connector 22. Is defined. The introduction orifice 30 is
Located between the introduction passage 23a and the discharge passage 23c, the opening area changes in accordance with the displacement of the sub spool 28, and the right end portion of the sub spool 28 is inserted into the protrusion 26b (the position shown in FIG. 2). ), Has an opening area determined by the notch 26d, and when the right end of the sub spool 28 is separated from the protrusion 26b, a gap and a notch formed between the right end of the sub spool 28 and the protrusion 26b. It has an open area determined by 26d. The control chamber 31 has a pressure introducing hole formed in the connector 22.
It communicates with the introduction passage 23a through 22b and the through hole 26c.

The sub-spool 28 has a main orifice 32 communicating with the communication hole 28a at one end on the right side in the drawing which is slidably inserted into the protrusion 26b and faces a primary pressure chamber 36 described later, and the other end on the left side is It has a large diameter and is formed in a cylindrical shape as a whole, and is slidably fitted in the accommodation hole 21a of the housing 23 as described above. A control chamber 31 is defined between the large-diameter stepped portion at the other end and the peripheral wall of the hole 22a of the connector 22, that is, the valve housing 23. The control chamber 31 is a pressure introducing hole formed in the connector 22. 22b and introduction orifice forming member 26
It communicates with the introduction passage 23a through the through hole 26c. Then, when the discharge amount of the pump 24 increases and the pressure in the control chamber 31 is increased, the sub spool 28 moves to the left against the spring 29, and the right end portion of the sub spool 28 separates from the protrusion 26b. As described above, a gap is formed between them. That is, the introduction orifice 30 is configured to be variable by the movement of the sub spool 28 due to the pressure increase in the control chamber 31.

A main spool 35 is slidably inserted in the accommodation hole 21a of the casing 21 on the right side of the drawing, and the primary pressure chamber is provided at both ends thereof.
36 and a secondary pressure chamber 37 are defined. The primary pressure chamber 36 is
The introduction orifice forming member 26 communicates with the introduction passage 23a through the notch 26d and the through hole 26c, and also communicates with the discharge passage 23c through the main orifice 32. Therefore,
The introduction passage 23a is an orifice for introducing the oil discharged from the pump 24.
It has a function of being introduced into the primary pressure chamber 36 via 30 and the discharge passage 23c is connected to the primary pressure chamber 36 via the main orifice 32.
It has the function of communicating hydraulic fluid to the actuator outside the system. In addition, the secondary pressure chamber 37 is
A hole 22 downstream of the main orifice 32 passes through a hole 38 formed in a land 35 (described later), a guide hole 21b formed in the casing 21, and a guide hole 22c formed in the connector 22.
It communicates with the inside of a. In this secondary pressure chamber 37, a spring 39 for urging the main spool 35 to the left in the drawing is contracted.

The main spool 35 has a groove 35a opened in the drain passage 23b and a groove 35a opened in the guide hole 21b of the casing 21.
35b is formed, and three lands 35c, 35d and 35e are set. The land 35c on the left side of the drawing is the drain passage 23.
A drain orifice 40 is configured between the drain orifice 40 and the shoulder 21c of the casing 21 set by b. The drain orifice 40 is located between the primary pressure chamber 36 and the drain passage 23b, and changes the opening area according to the displacement of the main spool 35. That is, this drainon orifice 40 increases the opening area of the drain passage 23b as the main spool 35 moves to the right in the figure, and the drain passage 23b of the introduction passage 23a is displaced via the primary pressure chamber 36 to the displacement of the main spool 35. Communication is performed with the appropriate opening area. The land 35e on the right side of the figure has a groove
The aforementioned pores 38 that communicate the 35b and the secondary pressure chamber 37 are formed. As described above, the fine holes 38, together with the guide hole 22c of the connector 22, the guide hole 21b of the casing 21, and the groove 35b, form a feedback passage that connects the secondary pressure chamber 37 to the discharge passage 23c.

The drain passage 23b is provided with the primary pressure chamber 36 and the secondary pressure chamber 36.
It has a function of discharging the hydraulic oil in the primary pressure chamber 36 to the low pressure side, that is, the suction side of the pump 20, in accordance with the sliding amount of the main spool 35 that slides according to the pressure difference with the 37. The flow rate control valve in the present embodiment configured drives the main spool 35 in accordance with the pressure increase in the primary pressure chamber 36 that accompanies an increase in the discharge amount of the pump 24, and the drain passage 23 from the primary pressure chamber 36 is driven.
The discharge amount to b is increased to control the supply amount of hydraulic oil from the main orifice 32 to the discharge passage 23c.

Next, the operation will be described.

In this flow control valve, the main spool 35 has the second orifice.
It moves according to the fluid pressure difference before and after 34 (the fluid pressure difference between the primary pressure chamber 36 and the secondary pressure chamber 37), and the opening area of the drain orifice 40, that is, the opening area of the drain passage 23b is changed to the introduction passage 23a. Part of the inflowing fluid is discharged from the drain passage 23b, and further, the sub-spool 28 moves in the control chamber 31 as the pressure increases, so that the fluid supplied from the discharge passage 23c to the power steering device is shown in FIG. 5 (b). The flow rate characteristics shown in are maintained. That is, a pump driven by an in-vehicle engine
24 has a discharge amount that is substantially proportional to the engine speed. The flow rate control valve recirculates a part of the fluid flowing from the introduction passage 23a to the pump 24 from the drain passage 23b and supplies the fluid supplied from the discharge passage 23c to the power steering device with a predetermined flow rate characteristic (Fig. 5 (b)). ).

The operation of the flow control valve will be described below with reference to FIGS. 5 (a) and 5 (b). In the following explanation, the introduction passage 23
The fluid pressures of c, the primary pressure chamber 36 and the discharge passage 23c are indicated by symbols p ₁ , p ₂ and p ₃ , respectively.

First, when the pump 24 has a low speed and a low flow rate and the fluid flow rate N flowing into the introduction passage 23a is less than the predetermined value N ₁ shown in FIG. 5 (b), the main spool 35 is urged by the spring 39 to Located in the center left, and similarly, the sub spool
28 is also biased by the spring 29 and is located on the right side in the figure (the position shown in FIG. 2). Therefore, the introduction orifice 30
Has an opening area determined by the notch 26d of the introduction orifice forming member 26, and the drain orifice 40 is in a state where the land 35c of the main spool 35 closes the drain passage 23b. Therefore, the fluid that has flowed into the introduction passage 23a flows through the introduction orifice 30, the primary pressure chamber 36 and the main orifice 32 into the communication hole 28a, and then further passes through the communication hole 27a so that the entire amount of the fluid is discharged from the discharge passage 23c. Supplied to the device.

Next, the flow rate N of the fluid flowing into the introduction passage 23a is the predetermined amount N ₁
When increased above (N ₁ ≦ N <N ₂ ), the fluid pressure difference ΔP ₂ = P ₂ −P ₃ before and after the main orifice 32 increases,
The main spool 35 opens the drain passage 23b in response to a pressure difference ΔP ₂ before and after the main orifice 32, that is, a fluid pressure difference between the primary pressure chamber 36 and the secondary pressure chamber 37. That is,
The main spool 35 moves rightward in response to the differential pressure ΔP ₂ between the primary pressure chamber 36 and the secondary pressure 37 against the elastic force of the spring 39 to open the drain orifice 40. Therefore, the introduction passage 23a
A part of the fluid that has flowed into the primary pressure chamber 36 passes through the introduction orifice 30 and is then discharged from the drain passage 23b, and the fluid flow rate Q supplied from the discharge passage 23c to the power steering device becomes a constant amount Q ₂ . .

Further, the flow rate N of the fluid flowing into the introduction passage 23a has a predetermined value N ₂
When it increases up to N ₃ (N ₂ ≦ N <N ₃ ), the fluid pressure difference ΔP before and after the main orifice 32 further increases. For this reason, the pressure difference between the primary pressure chamber 36 and the secondary pressure chamber 37 also increases, and the opening of the drain passage 23b becomes large.
The flow rate Q of the fluid supplied to the power steering device from 23c decreases. As a result, in the power steering device, the steering assist force generated by the power cylinder is reduced, and traveling stability during high-speed traveling can be achieved.

Thereafter, further the fluid flow rate N that flows into inlet passage 23a is increased (N ≧ N ^- _4), the sub-spool 28 is displaced to the larger left, the opening area of the inlet orifice 30 is increased.
That is, when the sub-spool 28 is displaced further, the right end portion of the sub-spool 28 is located on the left side of the ridge 26b in the figure,
An annular gap is formed between the right end of the sub spool 28 and the protrusion 26b. Therefore, the introduction orifice 30 has an opening area determined by the notch 26d of the first orifice forming member 26 and the gap, and the opening area is increased with the increase in the flow rate N of the fluid flowing into the introduction passage 23a. Corresponding to the left movement of the. Therefore, as shown in FIG. 5 (a), the fluid pressure p ₁ in the introduction passage 23a maintains a substantially constant value Po even if the flow rate N increases, reducing the load on the pump 24 and reducing the fluid pressure p ₁ To prevent the fluid temperature from rising due to

By the way, for example, when the fluid flow rate Q ₁ supplied from the discharge passage 23c to the power steering device is maintained at a predetermined value (normally, the fluid flow rate N flowing into the introduction passage 23a when the vehicle is traveling at high speed is a predetermined value). When the power steering device is operated in the case of N ₃ or more), the fluid pressure p _{3 in the} discharge passage 23c increases (the increased pressure is ΔP), so the sub spool 28 is pressed to the right in the figure. However,
The flow rate control valve acts to keep the differential pressure across the main orifice 32 constant in order to maintain the discharge flow rate Q ₁ constant.

That is, the increased amount ΔP of the discharge pressure acts on the secondary pressure chamber 37 to move the main spool 35 to the left, and the drain orifice 40c.
The opening area is reduced to increase the pressure in the primary pressure chamber 36 by ΔP.

Since the pressure in the primary pressure chamber 36 increases by ΔP, the upstream pressure of the introduction orifice also increases by ΔP and the pressure in the control chamber 31 also increases by ΔP.

Therefore, the front-rear surface pressure of the sub spool 28 is increased by ΔP, and therefore the sub-orifice 33 is not opened and the flow rate characteristic shown in FIG. 5 (b) is maintained unchanged.

FIG. 3 shows another embodiment of the present invention. The same parts as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the flow control valve of this embodiment, as shown in FIG. 3, the right end portion of the sub spool 28 in the drawing is loosely fitted into the projection 26b integrally formed with the connector 22 to form the introduction orifice 30. , Also snap ring locked to connector 22
A spring 29, which is contracted between 41 and the sub spool 28, urges the sub spool 28 to the right in the figure. That is,
The introduction orifice 30 is set by an annular gap formed by the outer peripheral surface of the right end of the sub spool 28 in the drawing and the inner peripheral surface of the protrusion 26b, and is opened as the sub spool 28 is displaced leftward in the drawing. The area increases.

Even in such a flow control valve, as described above, the fluid flow rate N is a predetermined amount N that flows into the introduction passage 23a ^- ₄ above reaches the displacement of the drawing in the left of the sub-spool 28 is increased to it Along with this, the area of the introduction orifice also increases, and it is possible to reduce the pressure loss as a flow control valve.

FIGS. 4 (a) and 4 (b) show another embodiment of the present invention.
It should be noted that the same parts as those in each of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

The flow control valve according to this embodiment is configured such that the opening area of the introduction orifice 30 changes according to the displacement of the main spool 35. That is, as shown in FIG. 4 (a), the sub spool 28 is provided at the left end of the main spool 35 in the figure.
An introduction orifice forming portion 42 in which the right end of is inserted slidably is integrally formed. This introduction orifice forming part 42
Has a tapered surface 42a and a flat surface 42b on its outer peripheral surface, and is loosely inserted into the connector 22 to form an annular gap between the tapered surface 42a or the flat surface 42b and the inner peripheral surface of the connector 22, that is, the introduction orifice 30. Is formed. In the introduction orifice 30, the relative position between the inner peripheral surface of the connector 22 and the tapered surface 42a and the flat surface 42b changes with the displacement of the main spool 35, and the opening area thereof changes. That is, the introduction orifice 30 has a constant opening area when the flat surface 42b is located radially inward of the inner peripheral surface of the connector 22 (FIG. 4 (a)), and FIG. As shown in, when the tapered surface 42a is located radially inward of the inner peripheral surface, the opening area of the tapered surface 42a changes as the main spool 35 moves to the right. In addition,
A communication hole 35f is formed in the main spool 35 and connects the introduction orifice 30 and the main orifice 32.

In such a flow rate control valve, the opening area of the introduction orifice 30 increases with the displacement of the main spool 35 to the right in the figure, and the same effect as in the above-described embodiment can be obtained.

In addition, in each of the above-described embodiments, the sub-spool 28 includes the upstream fluid pressure p ₁ of the introduction orifice 30 and the main orifice.
The sub-spool 28 is configured to respond to the pressure difference (p ₁ -p ₃ ) with the downstream fluid pressure p _{3 of} 32, but to respond to the fluid pressure difference (p ₁ -p ₂ ) before and after the introduction orifice 30. It is also possible to do so.

(Effects of the Invention) As described above, according to the flow control valve of the present invention, in the high flow rate region of the fluid flowing into the introduction passage, the opening area of the introduction orifice increases as the flow rate of the fluid flowing into the introduction passage increases. Increase. Therefore, the pressure loss of the fluid circuit due to the flow control valve can be reduced, the pump load can be reduced, and the rise in fluid temperature due to the rise in fluid pressure can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view showing a conventional flow control valve. 2 to 4 are views showing a flow control valve according to the present invention, FIG. 2 is a sectional view showing one embodiment, FIG. 3 is a sectional view showing another embodiment, and FIG. (a) is a sectional view showing another embodiment, FIG. 4 (b) is an enlarged view of a main part of FIG. 4 (a), and FIG. 5 (a).
Is a diagram showing the relationship between the flow rate and pressure of the fluid flowing into the inlet port, and FIG. 5 (b) is a diagram showing the flow rate characteristic. 21a ... accommodating hole, 23 ... valve housing, 23a ... introduction passage, 23b ... drain passage, 23c ... discharging passage, 24 ... pump, 28 ... sub spool, 30 ... introduction orifice, 31 ... Control chamber, 32 ... main orifice, 35 ... main spool, 36 ... primary pressure chamber, 37 ... secondary pressure chamber, 21b, 22c ... guide hole (feedback passage). 35b: Line groove (feedback passage). 38 ... Pore (feedback passage).

Claims (3)

[Claims] 1. A main spool 35 slidably accommodated in a housing hole 21a formed in a housing 23 and separating the interior of the housing hole into a primary pressure chamber 36 and a secondary pressure chamber 37, and the housing. An orifice that is formed and introduces the oil discharged from the pump 24
An introduction passage 23a introduced into the primary pressure chamber via 30;
Communicating with the primary pressure chamber via the main orifice 32,
Discharge passage 23 that supplies hydraulic oil to the actuator side outside the system
c, feedback passages 22c, 21b, 35b, 38 for communicating the discharge passage with the secondary pressure chamber, and sliding of the main spool that slides according to the differential pressure between the primary pressure chamber and the secondary pressure chamber. A drain passage 23b for discharging the hydraulic oil in the primary pressure chamber to the low pressure side in accordance with the dynamic amount, and driving the main spool in response to the pressure increase in the primary pressure chamber accompanying the increase in the pump discharge amount. A flow control valve that controls the amount of hydraulic oil supplied from the main orifice to the discharge passage by increasing the discharge amount from the chamber to the drain passage, and has a large diameter portion on the outer circumference, and is formed into a tubular shape as a whole. The sub-spool 28 is slidably fitted in the accommodation hole of the housing, and a control chamber 31 is defined between a step portion having a large diameter and the housing, and the control chamber is communicated with the introduction passage, The orifice is connected to the sub-split that accompanies the increase in pressure Flow control valve, characterized in that the variable expansion direction by the movement of the Le. 2. The flow control valve according to claim 1, wherein the introduction orifice is formed between one end of the sub spool and the housing. 3. The flow control valve according to claim 1, wherein the introduction orifice is formed between one end of the sub spool and the main spool.