JPH0664491B2 - Flow controller - Google Patents

Description

The present invention is applied to a power steering device of an automobile and the like, and adjusts a flow rate of a working fluid supplied from a power source to the power steering device to a predetermined flow rate. Regarding the control device.

(Prior 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 rotationally driven by an internal combustion engine mounted on a vehicle, and an oil pump increases its rotational speed. The discharge flow rate increases.

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 sufficient when the vehicle is stopped or running at low speed. Does not need much. Therefore, it is usual to bypass the excess flow rate generated by high-speed rotation by the flow rate control device and return it to the reservoir tank or the like.

As a flow rate control device of this kind, the applicant of the present application, as shown in FIG. 4, introduces a discharge passage 2 for introducing oil from the pump 1.
To the power steering device 5 via a variable orifice sub-orifice 4 arranged in series with the main orifice 3, which communicates with the main orifice 3. The pressure before and after the main orifice 3 is sub-spooled via the sensitive orifice 6 and the passage 7. 8 to control the sub-orifice 4 by reacting the sub-spool 8 with the differential pressure generated before and after the main orifice 3, while the main spool 9 that responds to the differential pressure generated before and after the sub-orifice 4 is connected to the reservoir. A flow control device adapted to a drain passage 10 leading to a tank (not shown) is proposed.

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 amount further increases, the sub spool 8 moves leftward against the spring force of the balance spring 12 due to an increase in the differential pressure generated before and after the main orifice 3 along with the further right movement of the main spool 9 associated therewith. Then, the sub-orifice 4 is narrowed. 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.

(Problems to be Solved by the Invention) By the way, in the above-mentioned conventional example, when the main spool 9 is moved, the pump discharge oil is a main orifice 3 of 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,
There is a problem that the pump load increases and energy loss occurs, and the heat generation causes the oil temperature of the pump discharge oil to rise, which accelerates the deterioration of the discharge oil. Furthermore, if the oil temperature rises,
Since many rubber parts are used for the pump 1 and the power steering device 5, deterioration of these rubber parts is promoted, and cavitation is likely to occur, so that the pump 1 and the power steering device 5 are not damaged. There was also the problem that it would increase.

(Means for Solving Problems) The present invention has been made in view of the above-mentioned problems, and a main spool is slidably inserted into a housing hole formed in a housing and the main spool is A primary pressure chamber is defined on one side and a secondary pressure chamber is defined on the other side, while an accommodation passage communicating with the primary pressure chamber via a first orifice and a sliding movement of the main spool in the accommodation hole. From the primary pressure chamber to the drain passage whose opening area is increased or decreased according to
A discharge passage communicating with an orifice is formed, and the discharge passage is communicated with the secondary pressure chamber, so that the main spool is responsive to a pressure difference between the primary pressure chamber and the secondary pressure chamber. In a flow rate control device for controlling the discharge amount from the discharge passage to a predetermined flow rate characteristic in response to fluctuations in the introduction flow amount from the introduction passage by slidingly controlling the drain flow rate from the drain passage, A control spool is provided at the opening of the introduction passage to the accommodation hole, and is displaced according to the pressure difference across the first orifice to change the opening area of the first orifice itself.

(Operation) According to the flow rate control device of the present invention, in the low flow rate region of the fluid flowing into the introduction passage, the first orifice communicates the introduction passage and the discharge passage with a relatively small opening area, and In the high flow rate range of the fluid flowing into the introduction passage, the control spool responds to the fluid pressure difference before and after the first orifice and increases the opening area of the first orifice as the flow rate of the fluid passing through the first orifice increases. Let Therefore, the pressure loss of the fluid circuit due to the flow rate control device is reduced, the pump load is reduced, and the rise of the fluid temperature due to the rise of the fluid pressure is prevented.

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

1 (a), (b), 2 and 3 (a),
(B) and (c) show an embodiment of the present invention applied to a vehicle power steering apparatus.

First, the structure will be described. In FIGS. 1A and 1B, reference numeral 21 denotes a housing hole 21 extending in the left-right direction in the drawing and having a left end opened.
A casing in which a is formed, 22 is a hollow connector in which a hole 22a is formed, and the connector 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 which open to the accommodation hole 21a, the introduction passage 23a is connected to a discharge port of the pump 24, and the drain passage 23b is connected to a suction port of the pump 24. The pump 24 is driven by an in-vehicle engine (not shown) to pressurize and discharge a fluid in a reservoir (not shown), and discharges a fixed amount of fluid per one revolution of its rotating shaft. A discharge passage 23c is provided at the left end in the drawing of the hole 22a of the connector 22, and the discharge passage 23c is connected to a control valve (four-way switching valve) of a power steering device (not shown). Further, the hole 22a of the connector 22 has a small diameter portion 25 and first, second, and third large diameter portions in order from the right adjacent to the discharge passage 23c.
The third large diameter portion 28 has a through hole 29 that connects the hole 22a and the introduction passage 23a. Reference numeral 31 is a hollow control spool fitted in the third large diameter portion 28 so as to be slidable in the axial direction. This control spool 31 has its shaft hole 31a.
And the through hole 29 that communicates with the through hole 29, and the control spool 31 slides out of the third large diameter portion 28 so as to come out of the third large diameter portion 28, and an introduction passage between the end of the inner peripheral surface of the third large diameter portion 28. 23a and a flange portion 33 that forms a gap that communicates the accommodation hole 21a. The flange portion 33 is formed through the through hole 29 of the connector 22 and the control spool.
The first orifice 34 is configured with the through hole 32 of 31.
Reference numeral 35 denotes a limiting passage for axially forming an initial differential pressure formed on the wall surface of the shaft hole 31a of the control spool 31 in the axial direction. Also, 37 is the third
It is contracted between the flat washer 38 diametrically installed on the large diameter portion 28 and the shoulder portion of the shaft hole 31a of the control spool 31, and the flange portion 33 of the control spool 31 is connected to the hole 22a of the connector 22. It is a coil spring that is constantly urged in a direction (leftward in the drawing) located in the third large diameter portion 28. The control spool
A notch 31b for inserting the washer 38 is formed in the 31 so as not to interfere with the washer 38 when sliding. The first
The orifice 34 is located between the introduction passage 23a and the discharge passage 23c, the opening area changes according to the displacement of the control spool 31, and the flange portion 33 of the control spool 31 is located inside the third large diameter portion 28. At this time, the opening area is determined by the through holes 29, 32. Further, when the flange portion 33 of the control spool 31 comes out of the third large diameter portion 28, the flange portion 33 of the control spool 31.
And an opening area determined by the gaps and the through holes 29 and 32 formed between the inner peripheral surface of the third large diameter portion 28 and the end portion.
40 is a hole 22a of the connector 22 and a shaft hole 31a of the control spool 31.
Numeral 39 is a substantially cylindrical sub-spool that is slidably fitted in the inside thereof, and 39 is one end surface of the second large diameter portion 27 and the sub-spool 40.
Is a coil spring that is compressed between the large-diameter portion and the sub-spool 40 and constantly biases the sub-spool 40 in the direction of the control spool 31 (to the right in the drawing). The sub spool 40 has a communication hole 42 having a main orifice 41 at one end (the left end in the figure), and a hole 22 that is orthogonal to the communication hole 42 near the main orifice 41.
It has a hole 43 opening to the first large diameter portion 26 of a. Therefore, the upstream side and the downstream side of the main orifice 41 communicate with each other through the hole 43 and the gap between the first large diameter portion 26 and the outer peripheral surface of the sub spool 40. The outer peripheral surface of the end of the sub spool 40 on the discharge passage 23c side constitutes a sub orifice 44 together with the shoulder portion between the small diameter portion 25 and the first large diameter portion 26 of the hole 22a. Is closed and the opening area changes with the displacement of the sub spool 40 to the left in the figure.
That is, the sub-orifice 44 has an opening area corresponding to the relative position between the connector 22 and the sub-spool 40. The sub-orifice 44 and the main orifice 41 are located in parallel between the communication hole 42 and the discharge passage 23c, and are located in the second orifice 45.
Are configured. Then, the opening area of the second orifice 45 changes according to the change of the opening area of the sub-orifice 44. On the other hand, a main spool 47 is slidably fitted to the right side of the accommodation hole 21a of the casing 21 in the figure, and a primary pressure chamber 48 and a secondary pressure chamber 49 are defined at both ends thereof. The primary pressure chamber 48 includes the shaft hole 31a of the control spool 31 and the through hole 3
It communicates with the introduction passage 23a via 2 and 29, and also communicates with the discharge passage 23c via the second orifice 45. That is, the primary pressure chamber 48 is located on the upstream side of the second orifice 45, and the second orifice 45 communicates with the introduction passage 23a via the first orifice 34. In addition, the secondary pressure chamber 49 is a fine hole formed in a land (described later) of the main spool 47.
50, guide hole 21b formed in casing 21 and connector 2
It communicates with the hole 22a on the downstream side of the second orifice 45 through the guide hole 22c formed in the second hole. Reference numeral 51 is a coil spring that is contracted in the secondary pressure chamber 49 and biases the main spool 47 to the left in the drawing. On the outer peripheral surface of the main spool 47, a groove 47a opened to the drain passage 23b and a groove 47b opened to the guide hole 21b of the casing 21 are formed.
c, 47d, 47e are formed. Land 47c on the left side of the figure
Forms a drain orifice 52 between the drain passage 23b and the opening edge of the accommodation hole 21a. The drain orifice 52 is located between the primary pressure chamber 48 and the drain passage 23b, and changes the opening area according to the displacement of the main spool 47. That is, the drain orifice 52 increases the opening area of the drain passage 23b with the right movement of the main spool 47 in the figure, and the introduction passage 23a and the drain passage 23b are displaced via the primary pressure chamber 48 into the displacement of the main spool 47. Communication is performed with the appropriate opening area. Also, on the land 47e on the right side of the figure, the groove 4
The aforementioned pores 50 that connect 7b and the secondary pressure chamber 49 are formed. As described above, the small hole 50 communicates the secondary pressure chamber 49 with the guide hole 22c of the connector 22, the guide hole 21b of the casing 21, and the groove 47b into the hole 22a downstream of the second orifice 45. . Inside the shaft hole 53 formed in the main spool 47, the ball valve body 54 together with the pressing rod 55 is biased by the check spring 56 and seated on the valve seat of the hollow tail plug 57 fixed to the opening end of the shaft hole 53. A relief valve 58 is provided. The relief valve 58 includes the guide hole 22c, the guide hole 21b, and the groove 47.
b) The pressure excess of the discharge passage 23c introduced into the secondary pressure chamber 49 through the fine hole 50 is released to the drain passage 23b.

Next, the operation will be described.

In this flow rate control device, the main spool 47 has a fluid pressure difference (a primary pressure chamber 48 and a secondary pressure chamber 49) before and after the second orifice 45.
The fluid pressure difference between the discharge passage 23a and the drain passage 23b is changed so that the opening area of the drain orifice 52, that is, the opening area of the drain passage 23b is changed, and a part of the fluid flowing into the introduction passage 23a is discharged from the drain passage 23b. Further, the sub spool 40 responds to the differential pressure before and after the second orifice 45, and more specifically, the secondary pressure in the discharge passage 23c from one side of the sub spool 40 from the other side (the primary pressure chamber 48 side). By supplying the pressure before the first orifice 34 (introduction pressure) and the primary pressure which is the rear pressure, the pressure is supplied from the discharge passage 23c to the power steering device by moving to a position where the forces from both sides are balanced. The fluid to be maintained is maintained at the flow rate characteristic shown in FIG. 5 (b). That is, the pump 24 driven by the vehicle-mounted engine
Since the discharge amount thereof has a substantially proportional relationship with the engine speed, the flow rate control device recirculates a part of the fluid flowing from the introduction passage 23a from the drain passage 23b to the pump 24, and the discharge passage 23c. The fluid supplied from the power steering device to the power steering device is maintained at a predetermined flow rate characteristic (Fig. 5 (b)).

The operation of the flow rate control device will be described below with reference to FIGS. 5 (a) and 5 (b). In the following explanation,
The fluid pressure from the introduction passage 23a to the first orifice 34, the fluid pressure from the first orifice 34 to the second orifice 45, and the fluid pressure from the second orifice 45 to the discharge passage 23c are denoted by symbols P ₁ , P ₂ , and P ₃ , respectively. Display with.

First, when the flow rate N of the fluid flowing into the introduction passage 23a is less than the predetermined value N1, the main spool 47 is urged by the spring 51 to be located on the left side in the figure, and the sub spool 40 is also urged by the spring 39. It is located on the right side of the figure. Further, the control spool 31 is also urged by a spring 37 as shown in FIGS. 1 (a) and 2 so that the flange portion 33 is fitted into the third large diameter portion 28 of the hole 22a. It is in the position. Therefore, the first orifice 34 has an opening area determined by the through holes 29 and 32, and
45 has an opening area determined by the sum of the opening areas of the main orifice 41 and the sub-orifice 44, and
The drain orifice 52 is a land 47c of the main spool 47.
Is closed because the drain passage 23b is closed. Therefore, the fluid that has flowed into the introduction passage 23a flows into the communication hole 42 via the first orifice 34 and the primary pressure chamber 48, and further passes through the main orifice 41 and the sub-orifice 44, and the entire amount from the discharge passage 23c to the power steering device. Supplied.

Next, when the fluid flow rate N flowing into the introduction passage 23a increases to a predetermined amount N ₁ or more (N ₁ ≦ N <N ₂ ), the fluid pressure difference (ΔP ₂ ) before and after the second orifice 45 (ΔP ₂ = P ₂₋ P ₃ ), the main spool 47 has a pressure difference ΔP ₂ before and after the second orifice 45.
That is, the drain passage 23b is opened in response to the fluid pressure difference between the primary pressure chamber 48 and the secondary pressure chamber 49. That is, the main spool 47 moves rightward to open the drain orifice 52 against the elastic force of the spring 51 so that the fluid pressure difference ΔP ₂ before and after the second orifice 45 becomes constant. Therefore, the introduction passage 23
A part of the fluid that has flown into a flows into the primary pressure chamber 48 through the first orifice 34, and then is discharged from the drain passage 23b.
The flow rate Q of the fluid supplied from the discharge passage 23c to the power steering device becomes a constant amount Q ₂ . At this time, the introduction passage
Since the first orifice 34, the main orifice 41 and the sub-orifice 44 in parallel with the first orifice 34 communicate with each other between the discharge passage 23c and the discharge passage 23a, it is possible to control the fluid flow rate to a large Q _2. . That is, since the sub-orifice 44 provided in parallel with the main orifice 41 communicates between the communication hole 42 and the discharge passage 23c, the second orifice 45 is formed.
This is because the area of is larger.

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 total flow rate of the fluid flowing into the introduction passage 23a is before and after the first orifice 34. The fluid pressure difference (ΔP ₁ ) (ΔP ₁ = P ₂ −P ₁ ) increases, and the fluid pressure difference ΔP ₂ before and after the second orifice 45 also increases. Therefore, the sub-spool 40 moves left against the elastic force of the spring 39 and closes the sub-orifice 44, so that the sub-orifice 44 has an opening area corresponding to the displacement of the sub-spool 40 (the opening area decreases. To). Therefore, the discharge passage 23
Flow rate Q of fluid supplied from c to the power steering device
Is reduced. As a result, the power steering system
The steering assist force generated by the power cylinder is reduced,
The running stability can be achieved during high-speed running.

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 40
Is further displaced to the left in the figure, and the sub-orifice 44 is completely closed. Therefore, the introduction passage 23a and the discharge passage 23c
Between the first orifice 34 and the main orifice 41.
The main spool 47 is displaced so that the fluid pressure difference ΔP ₂ before and after the main orifice 41 becomes constant. Therefore, as shown in FIG. 5B, the flow rate Q of the fluid supplied from the discharge passage 23c to the power steering device becomes a substantially constant amount Q1. In the above case, the control spool 31 is at the left end position due to the urging force of the coil spring 37, and the flange portion 33 of the control spool 31 is fitted in the third large diameter portion 28 of the hole 22a. The opening area of the one orifice 34 does not change.

After that, when the flow rate N of the fluid flowing into the introduction passage 23a further increases (N ≧ N ₄ ), the control spool 31 causes the first orifice to move.
As the fluid pressure difference ΔP ₁ before and after 34 increases, the fluid is displaced to the right as shown in FIG. 1B, and the opening area of the first orifice 34 increases. That is, when the control spool 31 is displaced to the right, the flange portion 33 of the control spool 31 projects rightward from the third large diameter portion 28 of the hole 22a, and the flange portion 33 of the control spool 31.
An annular gap is formed between the inner peripheral surface of the third large diameter portion 28 and the end portion of the third large diameter portion 28. Therefore, the first orifice 34 has an opening area determined by the through hole 32 and the gap, and the opening area corresponds to the right movement of the control spool 31 as the flow rate N of the fluid flowing into the introduction passage 23a increases. And increase. Therefore, as shown by the solid line in FIG. 5 (a), the fluid pressure P ₁ in the introduction passage 23a becomes extremely gentle even if the flow rate N increases, and the load on the pump 24 is reduced. ,
Prevents an increase in fluid temperature due to an increase in fluid pressure P ₁ .

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, the fluid flow rate N flowing into the introduction passage 23a when the vehicle is traveling at high speed is a predetermined value). N ₃ or more), when the power steering device operates, the fluid pressure P _{3 in the} discharge passage 23c
Is increased (the increased pressure is ΔP), the sub spool 40 is pressed rightward in the drawing. However, the flow rate control device works to keep the differential pressure across the second orifice 45 constant in order to keep the discharge flow rate Q ₁ constant.

That is, the increased amount ΔP of the discharge pressure acts on the secondary pressure chamber 49 to move the main spool 47 to the left, and the drain orifice 52.
The opening area of is reduced and the pressure in the primary pressure chamber 48 is increased by ΔP.

Therefore, the front-rear surface pressure of the sub spool 40 is increased by ΔP, and therefore the sub orifice 44 is not opened, and the flow rate characteristic shown in FIG. 5 (b) is maintained unchanged.

When the fluid pressure P ₃ in the discharge passage 23c becomes abnormally high, the relief valve 58 is used to prevent the excess pressure.
You can escape to 23b.

(Effects of the Invention) As described above, according to the flow rate control device of the present invention, the opening of the second orifice is provided between the introduction passage and the discharge passage in the low flow rate range of the fluid flow rate flowing into the introduction passage. The area increases, and in the high flow rate region, the opening area of the first orifice increases due to the action of the control spool, so that the overall resistance decreases and the pump is not forced to do unnecessary work. That is, since the load of the pump is reduced, energy loss and heat generation are eliminated, and the temperature of the fluid (working oil) is also reduced, so that deterioration of the fluid and rubber parts can be prevented, and the occurrence of cavitation can also be suppressed. . As a result, pump and power steering device failures are reduced.

[Brief description of drawings]

1 (a), (b) to 3 (a), (b),
FIG. 1 (c) is a diagram showing an embodiment of a flow rate control device according to the present invention, and FIGS. 1 (a) and 1 (b) are front sectional views showing different operating states, and FIG. 2 is FIG. (A) A
-A arrow sectional view, FIG. 3 (a) is a BB arrow sectional view of FIG. 2, FIG. 3 (b) is a CC sectional view of FIG.
2 (c) is a sectional view taken along the line DD in FIG. 2, FIG. 4 is a front sectional view showing a conventional flow rate control device, and FIG. 5 (a) is a flow rate and pressure of a fluid flowing into an introduction passage. Figure showing the relationship between
FIG. 6B is a diagram showing the flow rate characteristic. 23 …… Valve housing, 23a …… Introduction passage, 23b …… Drain passage, 23c …… Discharge passage, 31 …… Control spool, 34 …… First orifice, 40 …… Sub spool, 45 …… Second orifice, 47 …… Main spool, 52 …… Drain orifice.

Claims (1)

[Claims] 1. A main spool is slidably fitted in a housing hole formed in a housing to define a primary pressure chamber on one side of the main spool and a secondary pressure chamber on the other side of the main spool. The hole has an introduction passage communicating with the primary pressure chamber via a first orifice, a drain passage having an opening area increased or decreased according to sliding of the main spool, and a secondary orifice from the primary pressure chamber. And a discharge passage communicating with the secondary pressure chamber, and the main spool is slid in accordance with a pressure difference between the primary pressure chamber and the secondary pressure chamber. In the flow rate control device, the flow rate controller controls the discharge amount from the discharge passage to have a predetermined flow rate characteristic in response to the fluctuation of the flow rate introduced from the introduction passage by controlling the flow rate of the drain from the drain passage. The accommodation hole of The provided openings, the flow control device, characterized in that a control spool to vary the opening area of the first orifice itself displaced in response to differential pressure across said first orifice.