JPH0773997B2 - Flow control valve - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control valve which is applied to a power steering device of an automobile and adjusts a flow rate of a working fluid supplied from a power source to the power steering device to a predetermined flow rate.

[0002]

2. Description of the Related Art An oil pump as a power source for supplying a working fluid to a power steering device for assisting a manual steering torque by using a fluid as a working medium is usually driven to rotate by an internal combustion engine mounted on a vehicle. , The discharge amount increases due to the increase in the rotation.

However, the flow rate required for the 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 at low speed. It doesn't need much difference at high speed. 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 type, the applicant of the present application, as shown in FIG. 1, is a variable throttle 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. By communicating with the power steering device 5 through the sub-orifice 4 and applying pressures before and after the main orifice 3 to the sub-spool 8 through the sensitive orifice 6 and the passage 7, the sub-spool 8 is forward and backward of the main orifice 3. While controlling the sub-orifice 4 in response to the differential pressure generated in the
A flow control valve is proposed in which the main spool 9 that responds to the differential pressure generated before and after is matched with the drain passage 10 that communicates with a reservoir tank (not shown).

The discharge flow rate characteristic of this flow rate control valve device is shown in FIG.
As shown in (b), the hydraulic fluid discharged from the pump 1 passes through the main orifice 3 and the sub-orifice 4, while passing through the sub-orifice 4 due to the increase of the hydraulic fluid flowing into the sub-orifice 4. Due to the increase in the differential pressure, 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 the drain passage 10 escapes to the drain passage 10. Thus, the hydraulic oil sent out from the power steering device 5 is transferred to the main orifice 3
And a constant flow rate Q2 under the control of the sub-orifice 4.
To maintain. When the pump discharge amount further increases, the right movement of the main spool 9 further increases, and the differential pressure generated before and after the main orifice 3 increases, and the sub spool 8 increases.
To the left against the spring force of the counterbalance spring 12,
The sub-orifice 4 is narrowed down. In this series of operations, the flow rate sent to the power steering device 5 is gradually reduced from the constant flow rate Q2, and is controlled to the flow rate Q1 mainly caused by passing through the sub-orifice 4, which is so-called flow-down control.

[0006]

By the way, in the above-mentioned conventional example, when the main spool 9 is moved, the pump discharge oil passes through the main orifice 3 of the fixed throttle and escapes to the drain passage. There is a problem that the pressure in the resistance introducing passage 2 generated by 3 rises and the pump 1 is forced to perform unnecessary work, that is, energy loss and oil deteriorate.

[0007]

A flow control valve according to the present invention is slidably housed in a housing hole 21a formed in a housing 23, and a primary pressure chamber 36 and a secondary pressure chamber 37 are housed in the housing hole. And a main spool 35 that is separated from the main spool, and an introduction passage 2 that is formed in the housing and that introduces the discharge oil from the pump 24 into the primary pressure chamber through the introduction orifice 30.
3a, a discharge passage 23c that communicates with the primary pressure chamber via the main orifice 32 and supplies hydraulic oil to the actuator side outside the system, and a feedback passage 22c that communicates the discharge passage with the secondary pressure chamber. 21b, 35, 38
And a drain passage 23b for discharging the working oil of the primary pressure chamber to the 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 of the primary pressure chamber accompanying the increase of the pump discharge amount, and the discharge amount from the primary pressure chamber to the drain passage is increased to increase the supply amount of hydraulic oil from the main orifice to the discharge passage. A flow rate control valve for controlling, wherein the main orifice is provided at one end facing the primary pressure chamber, and the other end has a large diameter, and a sub spool 28 formed in a cylindrical shape as a whole is slid into an accommodation hole of the housing. The control chamber 31 is movably fitted and defined between a large-diameter step portion and the housing to connect the control chamber to the introduction passage, and the introduction orifice is provided on a cylindrical side wall of the sub spool. , Primary pressure chamber and A bypass orifice 33 that bypasses the orifice and directly connects the introduction passage and the discharge passage is formed, and the bypass orifice is closed by the movement of the sub-spool due to the pressure increase in the control chamber. Is.

[0008]

In the flow control valve of the present invention, the sub-orifice opens in the low flow region of the fluid flowing into the introduction passage, bypasses the introduction orifice, the primary pressure chamber and the main orifice, and is in parallel with these flow paths. In addition, the introduction passage and the discharge passage are directly communicated with each other, and in the high flow rate region of the fluid flowing into the introduction passage, the sub-orifice is closed and the pressure difference between the primary pressure chamber and the secondary pressure chamber increases. , The drain passage opening area 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.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional view of a flow control valve, showing an embodiment of the present invention to which a power steering device for a vehicle is applied. 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 the drawing and having a left end opened is formed, and 22 is a hollow connector in which a hole 22a is formed. 22 is screwed to the open end of the accommodation hole 21a of the casing 21, and functions as the valve housing 23 together with the casing 21.
The casing 21 is formed with an introduction passage 23a and a drain passage 23b opening to the accommodation hole 21a.
3 a is connected to the discharge port of the pump 24, and the drain passage 23 b 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 2
2, the discharge passage 23c is set at the left end of the hole 22a in the drawing, and 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 that engages with a sub spool, which will be described later, formed on the inner peripheral surface at the right end in the drawing, and also has a through hole 26c penetrating the inner surface and the outer surface and the left and right direction in the drawing. A notch 26b that extends and forms the introduction orifice 30 is formed. Also,
The hole 22a of the connector 22 has a through hole 27 on the left side of the drawing.
The plug 27 having the a formed therein is fitted, and the sub-spool 28 having the substantially cylindrical shape having the communication hole 28a formed therein is slidably fitted thereinto.
A spring 29 for urging the sub spool 28 to the right in the drawing is contracted between the spring 29 and the valve 8. The sub spool 28
Is provided with 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 has a large diameter, It 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. Also, the large-diameter stepped portion at the other end and the hole 2 of the connector 22
2a peripheral wall, that is, between the valve housing 23,
A control chamber 31 is defined, and the control chamber 31 communicates with the introduction passage 23a through a pressure introduction hole 22b formed in the connector 22 and a through hole 26c of the introduction orifice forming member 26. Further, a sub-orifice 33 that penetrates the inner peripheral surface and the outer peripheral surface is formed on the cylindrical side wall of the sub spool 28. Bypass, the introduction passage 23a is directly communicated with the discharge passage 23c through the through hole 26c and the communication hole 28a. 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 a part of the opening of the sub orifice 33 becomes the right end of the connector 22. It is configured so that it is blocked by the shoulder portion and its opening area is gradually reduced, and finally it is closed.

A main spool 35 is slidably fitted to the right side of the housing hole 21a of the casing 21 in the figure, and a primary pressure chamber 36 and a secondary pressure chamber 37 are defined at both ends thereof. . The primary pressure chamber 36 includes the introduction orifice forming member 26.
It 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
Has a function of introducing the discharge oil from the pump 24 into the primary pressure chamber 36 through the introduction orifice 30, and the discharge passage 23C has a function of introducing the primary pressure chamber 36 through the main orifice 32.
It has the function of communicating hydraulic fluid to the actuator outside the system. Further, the secondary pressure chamber 37 includes a pore 38 formed in a land (described later) of the main spool 35, a guide hole 21b formed in the casing 21, and the connector 2.
It communicates with the hole 22a on the downstream side of the main orifice 32 through the guide hole 22c formed in the No. 2. 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 is provided with a groove 35a opened to the drain passage 23b and a groove 35b opened to the guide hole 21b of the casing 21, and three lands 35c, 35d and 35e are set. . The land 35c on the left side of the drawing forms a drain orifice 40 between itself and the shoulder portion 21c of the casing 21 set by the drain passage 23b. This drain orifice 40 is
It 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, the drain orifice 40 increases the opening area of the drain passage 23 b as the main spool 35 moves to the right in the figure, and the introduction passage 23 is expanded through the primary pressure chamber 36.
a and the drain passage 23b communicate with each other with an opening area corresponding to the displacement of the main spool 35. The land 3 on the right side of the figure
5e is formed with the above-described pore 38 that communicates the groove 35b with the secondary pressure chamber 37. As described above, the pore 38 is formed in the guide hole 22c of the connector 22 and the casing 21.
Together with the guide hole 21b and the groove 35b of the secondary pressure chamber 37
To form a feedback passage that communicates with the discharge passage 23c. The drain passage 23b allows the hydraulic oil in the primary pressure chamber 36 to flow to the low pressure side, that is, in the pump, depending on the sliding amount of the main spool 35 that slides in accordance with the differential pressure between the primary pressure chamber 36 and the secondary pressure chamber 37. The flow rate control valve in the present embodiment having the function of discharging to the suction side of 24 is the primary pressure chamber 3 with the increase in the discharge amount of the pump 24.
The main spool 35 is driven in response to the pressure increase of No. 6 to increase the discharge amount from the primary pressure chamber 36 to the drain passage 23b to control the supply amount of hydraulic oil from the main orifice 32 to the discharge passage 23c. ing.

Next, the operation will be described. In this flow control valve, the main spool 35 moves according to the fluid pressure difference before and after the second orifice 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, By changing the opening area of the discharge passage 23c, a part of the fluid flowing into the introduction passage 23a is discharged from the drain passage 23b, and further, the sub-spool 28 moves along with the increase in pressure of the control chamber 31, so that the discharge passage 23c is discharged. The fluid supplied to the power steering device is maintained at the flow rate characteristic shown in FIG. That is, since the pump 24 driven by the vehicle-mounted engine has a discharge amount that is substantially proportional to the engine speed, the flow control valve is
Part of the fluid flowing in from a is returned to the pump 24 from the drain passage 23b, and the fluid supplied to the power steering device from the discharge passage 23c has a predetermined flow rate characteristic (see FIG. 3).
(B)).

The operation of the flow control valve will be described below with reference to FIGS. 3 (a) and 3 (b). In the following description, the fluid pressures of the introduction passage 23C, the primary pressure chamber 36, and the discharge passage 23C will be 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. 3B, the main spool 35 is urged by the spring 39 to The sub spool 28 is located on the center left side, and similarly, the sub spool 28 is also biased by the spring 29 to be located on the right side in the drawing (the position shown in FIG. 2). For this reason,
The sub-orifice 33 is fully open, and the drain orifice 40 is closed by the land 35c of the main spool 35 closing the drain passage 23b. Therefore, the fluid that has flowed into the introduction passage 23a is introduced into the introduction orifice 30, the primary pressure chamber 36, and the main orifice 3.
After flowing into the communication hole 28a via 2 and flowing into the communication hole 28a via the sub-orifice 33,
The entire amount is supplied from the discharge passage 23c to the power steering device through the through hole 27a. Therefore, when the pump 24 has a low flow rate, the sub-orifice 33 opens, bypasses the introduction orifice 30, the primary pressure chamber 36, and the main orifice 32, and in parallel with these passages, directly introduces the passage 23a and the discharge passage. 23c can be communicated.
Therefore, it is possible to reduce the pressure loss of the fluid circuit due to the flow control valve and to reduce the pump load while securing the discharge amount required for operating the power steering device.

Next, when the flow rate N of the fluid flowing into the introduction passage 23a increases to a predetermined amount N ₁ or more (N ₁ ≤N <N ₂ ),
Fluid pressure difference before and after the main orifice 32 ΔP ₂ = p ₂ −
p ₃ increases, and the main spool 35 responds to the pressure difference ΔP ₂ before and after the main orifice 32, that is, the fluid pressure difference between the primary pressure chamber 36 and the secondary pressure chamber 37, and the drain passage 23
Open b. That is, the main spool 35 is moved rightward according to the pressure difference ΔP ₂ between the primary pressure chamber 36 and the secondary pressure chamber 37 against the elastic force of the spring 39 to open the drain orifice 40. Therefore, a part of the fluid that has flowed into the introduction passage 23a passes through the introduction orifice 30 and then flows into the primary pressure chamber 36.
And then discharged from the drain passage 23b and supplied from the discharge passage 23c to the power steering device at a constant flow rate Q ₂ . At this time, the introduction passage 23
Since the introduction orifice 30 and the main orifice 32 are communicated in series between a and the discharge passage 23c through the sub-orifice 33, the fluid flow rate can be controlled to a large Q _2. It is possible.

When the flow rate N of the fluid flowing into the introduction passage 23a increases to a predetermined amount N ₂ or more (N ₂ ≤N <N ₃ ), the entire flow rate of the fluid flowing into the introduction passage 23a passes through the introduction orifice 30. And the fluid pressure difference after the main orifice 32, that is, the pressure difference ΔP ₁ = p ₂ −p ₁ between the introduction passage 23a and the discharge passage 23c increases, so that the sub spool 2
8 is moved to the left against the elastic force of the spring 29 by the fluid pressure p ₁ introduced into the control chamber 31, and the sub-orifice 33 is closed by the right end of the connector 22 according to the displacement of the sub-spool 28. It has an opening area corresponding to the displacement of the spool 28. That is, the opening area of the sub-orifice 33 is reduced corresponding to the left movement of the sub-spool 28.
Therefore, the flow rate Q of the fluid supplied from the discharge passage 23c to the power steering device 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.

Next, when the flow rate N of the fluid flowing into the introduction passage 23a increases above the predetermined amount N ₃ (N ₃ ≤N <
N ₄ ), the sub spool 28 is further displaced to the left in the drawing, and the sub orifice 33 is completely closed by the connector 22. Therefore, the introduction passage 23a and the discharge passage 23
With respect to c, the introduction orifice 30 and the main orifice 32 are interlocked only in series, and the main spool 35
Fluid pressure difference before and after the main orifice 32
It further moves in accordance with P ₂ , the opening area of the drain passage 23b increases, and the discharge amount from the primary pressure chamber 36 increases.
Therefore, as shown in FIG. 3 (b), the fluid flow rate Q supplied from the discharge passage 23c to the power steering device becomes a substantially constant amount Q ₁ .

After that, it further flows into the introduction passage 23a.
When the fluid flow rate N increases (N ≦ N_Four) Sub orifice 3
3 is closed and the main orifice is in front of the introduction orifice 30.
The pressure differential after the refis 32 increases and therefore the primary pressure
Pressure difference between force chamber 36 and secondary pressure chamber 37 ΔP₁Will increase
It Therefore, the main spool 35 moves further to the right,
The opening area of the drain passage 23b is further increased to increase the primary pressure chamber.
Emissions from 36 increase. Therefore, the power
The flow rate Q of the fluid supplied to the aligning device is constant Q ₁In
And the fluid pressure p in the introduction passage 23a₁Is shown in FIG.
As shown in (a), even if the flow rate N increases, a substantially constant value P
₀To maintain the load, reduce the load on the pump 24, and
Pressure p₁The rise of the fluid temperature is prevented due to the rise of.

By the way, for example, when the fluid flow rate Q ₁ supplied to the power steering device from the discharge passage 23c is maintained at a predetermined value (normally, when the vehicle is running at high speed, the fluid flow rate N flowing into the introduction passage 23a is for more than a predetermined value N _3), the power steering system is activated, the fluid pressure for p ₃ increases (the increase pressure amount △ P of the discharge passage 23c), the sub-spool 28 is pressed into the right side in the drawing It 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 to narrow the opening area of the drain orifice 40 and increase the pressure of the primary pressure chamber 36 by ΔP. . Since the pressure in the primary pressure chamber 36 increases by ΔP, the pressure on the upstream side of the introduction orifice 30 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. 3B is maintained unchanged. It In the above-described embodiment, the sub spool 28 responds to the pressure difference (p ₁ −p ₃ ) between the upstream fluid pressure p ₁ of the introduction orifice 30 and the downstream fluid pressure p ₃ of the main orifice 32. It is also possible to configure the sub spool 28 to respond to a fluid pressure difference (p ₁ -p ₂ ) before and after the introduction orifice 30.

[0022]

As described above, according to the flow control valve of the present invention, the sub-orifice is opened in the low flow rate region of the fluid flowing into the introduction passage, and the introduction orifice, the primary pressure chamber and the main orifice are opened. Bypassing these in parallel with the flow path and directly connecting the introduction passage and the discharge passage, and in the high flow rate region of the fluid flowing into the introduction passage, the sub-orifice is closed and the secondary pressure chamber and the secondary pressure chamber are closed. The pressure difference from the next pressure chamber increases, and the drain passage opening area increases. As a result, the overall resistance is reduced and the pump is not forced to do unnecessary work. That is, the loss of energy and the deterioration of oil due to heat generation can be prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a conventional flow control valve.

FIG. 2 is a sectional view showing an embodiment of a flow control valve according to the present invention.

FIG. 3 (a) is a diagram showing a relationship between a flow rate and pressure of a fluid flowing into an inlet port, and FIG. 3 (b) is a diagram showing a flow rate characteristic.

[Explanation of symbols]

 21a accommodation hole 21b, 22c guide hole (feedback passage) 23 valve housing 23a introduction passage 23b drain passage 23c discharge passage 24 pump 28 sub spool 30 introduction orifice 31 control chamber 32 main orifice 33 sub orifice 35 main spool 35b groove (feedback passage) ) 36 primary pressure chamber 37 secondary pressure chamber 38 pores (feedback passage)

Claims (1)

[Claims] 1. A housing hole 21a formed in a housing 23.
A main spool 35 that is slidably accommodated in the housing and is divided into a primary pressure chamber 36 and a secondary pressure chamber 37 in the accommodation hole; and an orifice 30 for introducing oil discharged from the pump 24, which is formed in the housing. An introduction passage 23a for introducing the primary pressure chamber into the primary pressure chamber, the primary pressure chamber and the main orifice 3
2, a discharge passage 23c for communicating hydraulic oil to the actuator side outside the system, and feedback passages 22c, 21b, 3 for communicating the discharge passage with the secondary pressure chamber.
5b, 38 and a drain passage 23b for discharging the working oil of the primary pressure chamber to the 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.
With, the primary pressure chamber of the
A flow control valve that drives the main spool in response to an increase in pressure to increase the discharge amount from the primary pressure chamber to the drain passage to control the supply amount of hydraulic oil from the main orifice to the discharge passage. A sub-spool 28, which is provided with the main orifice at one end facing the chamber and has a large diameter at the other end and is formed in a tubular shape as a whole, is slidably fitted into the accommodation hole of the housing to form a large-diameter step portion. A control chamber 31 is defined between the housing and the control chamber to communicate with the introduction passage, and the cylindrical side wall of the sub spool bypasses the introduction orifice, the primary pressure chamber and the main orifice. A bypass orifice 33 that directly communicates the introduction passage and the discharge passage is formed, and the bypass orifice is closed by the movement of the sub spool accompanying the pressure increase in the control chamber. Flow rate system valve, characterized in that.