JPH0571652A - Flow controller - Google Patents

Abstract

PURPOSE:To get such a characteristic that a delivery quantity to the destination becomes lessened contrariwise when a supply flow rate is much, stably in a simple structure. CONSTITUTION:A throttle plate 4 (second fixed throttle), where supply oil flows, is set up in and around the opening end of a supply oil passage 10 for a supply chamber A, and another throttle plate 4 (second fixed throttle), where delivery oil flows, in an interval between the supply chamber A and a delivery chamber B, respectively, and then there is provided a sub spool 5 responding to hydraulic pressure F0 at a front side of the throttle plate 3. A main spool 2, distributing the supply oil for the supply chamber A to the delivery chamber B and a reflux oil passage 11 according to the motion, is made up of installing both first and second lands 21, 22 with a large area and a third land 23 with a small area. In addition, a front side of the throttle plate 4, namely, internal pressure P1 in the supply chamber A is always received by the first land 21, while a rear side of the throttle plate 4, namely, the receiving range of internal pressure P2 in the delivery chamber B is varied in a range from the whole surface of the second land 22 to that of the third land 23 according to the operation of the sub spool.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate control device which is interposed between a discharge side of a pump and a delivery destination of a delivery fluid to control a delivery flow rate to the delivery destination, and more particularly to a flow control device for the pump. The present invention relates to a flow rate control device that performs an operation of reducing the delivery flow rate conversely according to the increase of the discharge flow rate.

[0002]

2. Description of the Related Art In many fluid pressure circuits, a pump serving as a pressure generation source unilaterally discharges an amount of fluid according to its driving condition, while supplying this fluid causes a predetermined operation. Since the destination to perform only needs the amount of fluid corresponding to the operating condition at that time, a part of the discharge fluid of the pump is transferred to the suction side between the discharge side of the pump and the destination. A flow rate control device for recirculating and controlling the delivery flow rate to the delivery destination is attached.

For example, an automobile configured to supply hydraulic oil to a hydraulic actuator arranged in a steering mechanism in response to an operation of a steering wheel (steering) and obtain a steering assist force by the generated force of the hydraulic actuator. In the power steering apparatus (power steering apparatus), the hydraulic pump, which is the source of hydraulic oil, is generally driven by the engine, and the amount of oil discharged from the hydraulic pump increases as the vehicle speed increases. The road surface reaction force applied to the wheels during steering is large during stoppage and low-speed traveling and small during high-speed traveling. Therefore, the hydraulic actuator needs to generate a steering assist force that becomes large or small according to the slow speed of the vehicle.

That is, in the power steering apparatus, regardless of the amount of oil discharged from the hydraulic pump that is the source of hydraulic pressure, the amount of oil that is sent to the hydraulic actuator that is the destination of this hydraulic pressure is approximately It is required to maintain a constant amount, and more desirably, to secure a sufficient amount of oil to be delivered at the time of stop and low speed traveling with a small amount of discharged oil, and conversely to reduce the amount of delivered oil during high speed traveling with a large amount of discharged oil. The hydraulic pump is provided with a flow rate control device for enabling such automatic adjustment of the delivered oil amount.

As a typical configuration of this type of flow rate control device, there are flow rate control devices disclosed in Japanese Patent Publication No. 1-27308 and Japanese Patent Publication No. 3-550. FIG. 7 is a schematic diagram of this flow rate control device.

As shown in the figure, in this flow control device, a flow rate adjusting spool 7 is fitted inside a valve hole 1 formed in a housing of a hydraulic pump so as to be slidable in the axial direction, and a valve is provided. A pressing spring 70 interposed between the bottom surface of the hole 1 and the opening side (left side in the drawing) urges the spool housing 8 into a cylindrical shape on the opening side of the valve hole 1. Disc-shaped diaphragm plates 9 are fitted and fixed on the opening side, respectively, and further, the spool spool 8 is slidable in the axial direction in the spool housing 8.
Is internally fitted, and is biased toward the inner depth side (right side in the figure) of the valve hole 1 by a push spring 81 interposed between the spool plate 8 and the throttle plate 9. The structure is such that it is pressed against the stopped stopper 82.

The diaphragm plate 9 is formed with a diaphragm hole 90 penetrating the central portion in the thickness direction, and a plurality of diaphragm holes 91, 91 ... Which are equally arranged around the diaphragm hole and also penetrate in the thickness direction. I am doing it. Further, the throttle spool 80 includes a flow rate adjusting spool 7
Oil passage hole that is open to the diaphragm plate 9 side by being branched into a pair of inclined holes that are open at the axial center portion and that are inclined outward in the radial direction.
83 is formed, and a projection 84 is provided at the axial center of the diaphragm plate 9 so as to face the diaphragm hole 90 at the center thereof.

A discharge oil passage 10 connected to the discharge side of the hydraulic pump and a return oil passage 11 connected to the suction side of the valve hole 1 are opened at an appropriate distance in the axial direction, and the discharge oil passage 10 is formed. The open end of is always closed by the peripheral wall of the spool housing 8,
Further, the open end of the return oil passage 11 is adapted to open in response to the sliding of the flow rate adjusting spool 7 which is generated against the biasing force of the push spring 70.

Thus, the oil supplied from the discharge oil passage 10 into the valve hole 1 passes through the throttle hole 85 formed through the peripheral wall of the spool housing 8 and the supply chamber A inside the spool housing 8.
To the return oil passage 11 which opens according to the sliding of the flow rate adjusting spool 7 and the oil passage hole 83 formed in the throttle spool 80. The former flows back to the suction side of the hydraulic pump, the latter flows into the front side of the throttle plate 9 through the oil passage hole 83, and further passes through the throttle holes 90 and 91, 91 ... The oil flows into the delivery chamber B on the rear side and is delivered to a predetermined oil destination connected to the delivery chamber B.

A pressure guiding hole 86 is formed on the peripheral wall of the spool housing 8 so as to communicate with an annular chamber C formed inside the spool housing 8 between the throttle spool 80 and the stopper 82. The internal pressure of the chamber B is guided to the back side of the flow rate adjusting spool 7 on the bottom surface of the valve hole 1, that is, the accommodating chamber of the pushing spring 70 by the communication passage 12 arranged in parallel along the longitudinal direction of the valve hole 1. ing.

Therefore, the throttle spool 80 has a discharge oil passage 10
When the total amount of the oil supplied from the tank flows into the supply chamber A through the throttle hole 85, the pressure difference generated between the annular chamber C and the supply chamber A, that is, between the discharge oil passage 10 and the supply chamber A is received. Then, it slides to the left in the figure against the urging force of the push spring 70, and the projection 84 provided at the axial center portion closes the throttle hole 90 in the center of the diaphragm plate 9, It serves to reduce the total area of the peripheral throttle holes 91, 91 ....

That is, this flow rate control device constitutes a fixed throttle through which a throttle hole 85 penetrating the spool housing 8 allows almost the entire amount of the supplied oil to flow, and the throttle spool 80 and the throttle plate 9 constitute the fixed throttle. The throttle area is reduced in accordance with the increase in the pressure difference between the front and rear to form a variable throttle in which only the delivery oil flows, and the flow rate adjusting spool 7 is slid by the pressure difference between the front and rear of the variable throttle, and this sliding is performed. Due to the increase in the opening area of the return oil passage 11 due to the above, the amount of oil recirculated from the supply chamber A to the suction side is increased, and the amount of oil delivered through the delivery chamber B is relatively reduced.

Therefore, in the hydraulic pump equipped with this flow rate control device, in the range where the pump rotational speed is small, the amount of delivered oil increases proportionally as the rotational speed increases, but due to the pressure difference before and after the variable throttle. After the flow rate adjusting spool 7 starts sliding, the amount of return oil to the return oil passage 11 increases as the amount of oil supplied from the discharge oil passage 10 increases, and the amount of oil delivered to the destination is substantially constant. Maintained at.

When the amount of oil supply further increases and the throttle spool 80 starts sliding due to the pressure difference before and after the fixed throttle, the throttle area of the variable throttle is reduced due to this sliding, and the flow resistance increases. The rate of increase in the amount of recirculating oil due to the sliding of the flow rate adjusting spool 7 exceeds the rate of increase in the amount of supplied oil, and the amount of delivered oil decreases conversely as the rotational speed of the pump increases.

After the amount of oil supplied is further increased and the projection 84 at the tip of the throttle spool 80 closes the throttle hole 90 in the center of the diaphragm plate 9, the throttle area of the variable throttle is constant (peripheral throttle holes 91, 91). (Total area of ...), and the amount of oil delivered to the oil destination is kept constant at a smaller amount than in a certain range in the range where the pump rotation speed is small. That is, a change mode of the delivered oil amount as shown in FIG. 8 is obtained, and such a change of the delivered oil amount is
It meets the requirements on the hydraulic actuator side of the power steering apparatus.

[0016]

However, in the conventional flow rate control device having the above-described structure, in order to configure the variable throttle, the spool housing 8, the throttle plate 9, the throttle spool 80, the pressing spring 81 and the stopper 82 are provided. As a result, a large number of parts that require precision processing are required, and a large number of processing man-hours and assembling man-hours are required.

Further, since the entire amount of the delivered oil flows through the oil passage hole 83 formed in the axial center of the throttle spool 80, the throttle spool 80 is actuated by the action of dynamic pressure particularly in the range where the delivered oil amount is large. Shows unstable behavior, and there is a problem that it is difficult to stably obtain the reduced portion of the delivered oil amount shown in FIG. This can be solved by increasing the area of the oil passage hole 83 to reduce the internal flow velocity, but in order to increase this area,
The diameters of the throttle spool 80, the spool housing 8 and the valve hole 1 need to be increased, which leads to an increase in the size of the entire flow rate control device.

Further, the shape of the flow path from the supply chamber A to the delivery chamber B connected to the oil destination is complicated, and for example, at the time of starting the hydraulic pump in cold regions, it prevents the passage of oil having high viscosity. Due to the high surge pressure that accompanies it, an unpleasant noise (gurgling noise) continues for a long time, and there is a further drawback. In addition, the hydraulic pressure reaching each part of the hydraulic pump on the upstream side and the oil destination on the downstream side. There was even a risk of damaging the piping.

The present invention has been made in view of such circumstances, and it is possible to stably obtain the same characteristics as the conventional one with a simple structure having no variable throttle, and to simplify surge pressure by simplifying the flow path. An object of the present invention is to provide a flow rate control device capable of preventing damage to the pump and piping system due to the above, and generation of ginger noise.

[0020]

A flow rate control device according to the present invention includes a first fixed throttle through which a supply fluid from a pump flows, and a delivery fluid to a delivery destination located downstream of the first fixed throttle. The second fixed throttle through which the air flows and the pressure difference generated before and after the second fixed throttle responds to the force balance between the second fixed throttle and the constantly acting biasing force, and the amount of supply fluid corresponding to this operation is supplied. A main spool that recirculates to the suction side of the pump to control the delivery flow rate to the delivery destination; and a sub spool that responds to the pressure on the upstream side of the first fixed throttle and changes the force balance. Is characterized by.

Further, the operation of the sub-spool adjusts the pressure receiving area of the pressure difference in the main spool or the urging force acting on the main spool.

[0022]

In the present invention, the fluid supplied from the pump is
First, a pressure difference is generated before and after flowing through the first fixed throttle, and is distributed to the delivery side and the reflux side according to the position of the main spool at this time, and the fluid on the delivery side is then fed to the second fixed throttle. A pressure difference is generated before and after passing through, and is delivered to a predetermined destination. The position of the main spool is determined according to the force balance between the urging force that constantly acts on it and the pressure difference before and after the second fixed throttle. This force balance is determined by the first fixed flow through which the entire amount of the supply fluid flows. Due to the operation of the auxiliary spool in response to the pressure on the upstream side of the throttle, the delivery flow rate is changed depending on the supply flow rate, for example, by changing the area for receiving the pressure difference or by adjusting the biasing force. The characteristics of are obtained.

The delivery flow rate Q delivered through the second fixed throttle is expressed by the following equation.

[0024]

[Equation 1]

In the prior art, the characteristic of the delivery flow rate Q is changed by changing the throttle area A in the equation (1) by the operation of the variable throttle, whereas in the present invention, the force in the main spool is changed by the operation of the auxiliary spool. The characteristics of the delivery flow rate Q are changed by changing the balance and changing the term of ΔP in the equation (1).

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. 1, 2 and 3 are schematic diagrams showing a first embodiment of a flow rate control device according to the present invention (hereinafter referred to as the device of the present invention), which show different operating states, respectively.

Reference numeral 1a in the drawing denotes a main spool hole having a circular cross section and having an opening on one side connected to an oil destination (not shown).
A discharge oil passage 10 connected to the discharge side of the hydraulic pump is provided on the opening side of the main spool hole 1a, and a return oil passage 11 also connected to the suction side is provided on the inner back side of the main spool hole 1a with a proper distance from each other. In addition, a small-diameter portion processed to have a smaller diameter than the other portion is formed on the inner depth side of the main spool hole 1a over a predetermined length range.

Further, reference numeral 2 in the drawing is a main spool provided with three lands 21, 22, 23 arranged in parallel in the axial direction, and the first land 21 and the second land 22 at the center on one side in the arranging direction. The outer diameter is set to be substantially equal to the inner diameter on the opening side of the main spool hole 1a, and the outer diameter of the third land 23 on the other side is smaller than that of the first and second lands 21 and 22, and the inner diameter of the small diameter portion is small. Is set almost equal to.

The main spool 2 is fitted in the main spool hole 1a slidably in the axial direction with the third land 23 on the back side, and is fitted into the bottom surface of the small diameter portion and the small diameter portion. Third
A push spring 24 interposed between the land 23 and the land 23 biases the main spool hole 1a toward the opening side. Push spring 24
The sliding of the main spool 2 in the urging direction (leftward in the figure) of
When the stop ring 25 engaged between the opening position of the discharge oil passage 10 and the opening position of the return oil passage 11 and the end surface of the first land 21 come into contact with each other, sliding in the opposite direction is prevented. The tips of the stoppers 26 projecting from the end surfaces of the three lands 23 and the bottom of the main spool hole 1a come into contact with the stoppers 26, respectively, so that they are restricted.

A throttle plate 3 (first fixed throttle) having a small-diameter throttle hole in the center is provided in the vicinity of the end of the discharge oil passage 10, and similarly in the center in the vicinity of the opening end of the main spool hole 1a. Diaphragm plates 4 (second fixed diaphragms) having small-diameter diaphragm holes are respectively fitted.

The diaphragm plate 4 has two chambers between the opening end of the main spool hole 1a and the main spool 2, that is, the main spool 2.
Side supply chamber A and open end side delivery chamber B are divided into
The opening position of the discharge oil passage 10 is set so as to be in the supply chamber A regardless of the sliding position of the main spool 2, and the opening position of the return oil passage 11 is as shown in FIG. When the main spool 2 is in the position in contact with the retaining ring 25, the main spool 2 does not open into the supply chamber A, and as shown in FIGS. 2 and 3, the main spool 2 slides against the bias of the push spring 24. The opening area into the supply chamber A is set to increase according to the movement.

In the main spool hole 1a, a sub spool hole 1b having a circular cross section is arranged in parallel along the main spool hole 1a. The sub spool hole 1b is slidable in the axial direction. The sub spool 5 is fitted inside. The sub spool 5 includes a first land 51 and a second land 52 that are arranged side by side in the axial direction, and is interposed between the one side bottom portion of the sub spool hole 1b and the second land 52 on the same side. It is urged in one direction (leftward in the figure) by the mounted push spring 53. The sliding of the sub spool 5 in the urging direction is caused by the contact between the stopper 54 projecting from the end surface of the first land 51 and the bottom of the sub spool hole 1b. The stopper 55 protruding from the end surface of the second land 52 and the bottom portion of the sub spool hole 1b come into contact with each other, so that the stopper 55 and the stopper 55 are limited.

The main spool hole 1a and the sub spool hole 1b are connected by a communication passage 13. On the main spool hole 1a side, the opening position of the communication passage 13 is always the second position of the main spool 2.
It is set between the third lands 22 and 23, and on the side of the sub spool hole 1b, it is always set between the first and second lands 51 and 52 of the sub spool 5.

Further, in the middle of the sub spool hole 1b, a pressure guide passage 14 communicating with the delivery chamber B and a drain passage 15 opened to the oil tank T maintained at a low pressure are provided in a predetermined axial direction. It is opened long apart. The pressure guide passage 14 is the sub spool 5
Is in the sliding position shown in FIG. 1, the first and second lands 51,
Opened between 52, the opening area is reduced in accordance with the sliding of the sub spool 5 that is generated against the bias of the push spring 53, and finally closed by the first land 51 as shown in FIG. It is like this. On the contrary, the drain path 15 is shown in FIG.
When it is in the sliding position shown in FIG. 3, it is in a state of being closed from the second land 52, and opens between the first and second lands 51 and 52 in response to the sliding of the sub spool 5.

The pressure guiding passage 14 is also communicated with the small diameter portion on the inner side of the main spool hole 1a.
The hydraulic pressure introduced via the
The main spool 2 is pressed in the same direction as the biasing direction of the pressing spring 24 (leftward in the figure) by the force obtained by multiplying the area of the third land 23 by the hydraulic pressure.

The drain passage 15 has a sub spool hole 1b.
The other side of the second land 52 inside is also communicated, and the same side is always kept in a low pressure state. Further, the other side of the first land 51 inside the sub spool hole 1b is connected to the discharge oil passage 10. It communicates with the upstream side of the diaphragm plate 4 via a pressure guiding path 16. That is, the sub spool 5 receives the hydraulic pressure introduced into the sub spool hole 1b through the pressure guiding path 16 on the end surface of the first land 51, and slides leftward in the figure against the bias of the push spring 53. At this time, the pressure between the first and second lands 51 and 52 of the sub spool 5 inside the sub spool hole 1b changes according to the open / closed state of the pressure guiding path 14 and the drain path 15 associated with the sliding. But this pressure is
Since the first and second lands 51 and 52 respectively act on the opposing surfaces having the same area, they do not contribute to the sliding of the sub spool 5 and go through the communication passage 13 opened between the lands 51 and 52. ,
The second and third main spool 2 inside the main spool hole 1a
Guided between lands 22 and 23.

The hydraulic pressure introduced to the second and third lands 22 and 23 by the communication passage 13 acts on these opposing surfaces, but the third land 23 has a smaller diameter than the second land 22 as described above. The main spool 2 is pressed in the same direction as the biasing direction of the pressing spring 24 (leftward in the figure) by the force obtained by multiplying the area difference between the second and third lands 21 and 22 by the hydraulic pressure.

The operation of the apparatus of the present invention constructed as above will be described below. The oil discharged from the hydraulic pump flows into the supply chamber A through the discharge oil passage 10, a part of the oil is discharged to a predetermined oil destination via the discharge chamber B, and the remaining portion is introduced into the return oil passage 11 to be supplied to the hydraulic pump. It is returned to the suction side. At this time, the ratio of the amount of delivered oil and the amount of recirculated oil to the total amount of oil supplied to the supply chamber A is determined according to the opening area of the recirculated oil passage 11 that opens as described above as the main spool 2 slides. It

When the internal pressure of the discharge oil passage 10 is P ₀ , the internal pressure of the supply chamber A is the diaphragm plate 3 (first
P ₁ lower than P ₀ due to the pressure drop caused by the flow of the fixed throttle), and the internal pressure of the delivery chamber B is the same as that of the oil delivery chamber B.
Due to the pressure drop caused by the flow of the throttle plate 4 (second fixed throttle) that separates the supply chamber A from the supply chamber A, the pressure P ₂ becomes lower than the pressure P ₁ . That is, a pressure difference of (P ₀ -P ₁ ) is generated before and after the diaphragm plate 3, and a pressure difference of (P ₁ -P ₂ ) is generated before and after the diaphragm plate 4.

The hydraulic pressure introduced into the sub spool hole 1b through the pressure guide passage 16 is the internal pressure of the discharge oil passage 10 on the upstream side of the throttle plate 3, that is, the above-mentioned P ₀ , and the sub spool for receiving this P _0. 5
Tends to slide to the right in the figure against the biasing force of the push spring 53, but in the region where the rotational speed of the hydraulic pump is low, its discharge pressure, that is, the internal pressure P ₀ is also low,
Since the urging force of the push spring 53 is dominant, the auxiliary spool 5 moves to the position where the stopper 54 protruding from the first land 51 is pressed against the end surface of the auxiliary spool hole 1b, that is, the sliding position shown in FIG. is there.

At this time, the pressure guiding path 14 is opened between the first and second lands 51, 52 of the sub spool 5, and the internal pressure P _{2 of the} delivery chamber B is introduced through the pressure guiding path 14. This introduced hydraulic pressure P ₂ is further introduced between the second and third lands 22 and 23 of the main spool 2 via the communication passage 13, while the third hydraulic pressure P ₂ is introduced.
The internal pressure P ₂ of the delivery chamber B is also introduced to the back side of the land 23 via the pressure guiding path 14. Therefore, the main spool 2 receives the internal pressure P ₂ on the entire surface of the second land 22, and is pressed leftward in the figure by this and the urging force of the push spring 24, and also on the entire surface of the first land 21. The internal pressure P ₁ of the supply chamber A is received and pressed rightward in the drawing.

That is, the main spool 2 slides to the right in the figure due to the force balance between the pressure difference (P ₁ -P ₂ ) generated before and after the throttle plate 4 and the urging force constantly applied by the pressing spring 24. become. The sliding of the main spool 2 is started when the pressure difference (P ₁ -P ₂ ) exceeds the urging force of the push spring 24. Before this, the flow returns into the supply chamber A as shown in FIG. The oil passage 11 is not open, and the supply chamber A
The total amount of oil supplied to the pump is sent through the sending chamber B, and the sent oil amount increases proportionally as the pump rotation speed increases.

The pressure difference (P ₁ -P ₂ ) before and after the throttle plate 4 also increases in accordance with the increase in the amount of delivered oil, so that after the main spool 2 starts sliding, it is accompanied by this sliding. As a result of the increase in the opening area of the return oil passage 11 into the supply chamber A, the increase in the supply oil amount to the supply chamber A is offset by the increase in the return oil amount that is returned to the suction side via the return oil passage 11. The amount of oil delivered from the delivery chamber B is maintained substantially constant regardless of the pump rotation speed.

Meanwhile, during this period, the internal pressure P ₀ of the discharge oil passage 10 on the upstream side of the throttle plate 3 also increases with an increase in the pump rotation speed, and the auxiliary spool 5 that receives this internal pressure P ₀ is a push spring.
It has started sliding to the right in the figure against the biasing force of 53,
After sliding for a predetermined length, as shown in Figure 2,
The drain path together with the pressure guiding path 14 between the first and second lands 51, 52
15, the opening amount of the drain passage 15 opened to the oil tank T gradually increases as the sliding amount of the sub spool 5 increases, that is, as the internal pressure P ₀ on the upstream side of the throttle plate 3 increases. ..

That is, after the passages 14 and 15 are opened, the hydraulic pressure between the first and second lands 51 and 52 decreases as the internal pressure P ₀ increases with the increase in the pump rotation speed. Goes through the communication passage 13 to the second and third lands of the main spool 2.
As a result of being introduced between 22 and 23, the pressure difference (P ₁ -P ₂ )
The pressure receiving area of is gradually reduced. That is, after the sub spool 5 slides for the predetermined length, the force balance described above relating to the sliding of the main spool 2 changes, and the increase rate of the amount of oil flowing through the throttle plate 4 and the main spool 2 change. As the result of the latter exceeding the former, the amount of oil delivered to the oil destination will decrease conversely with the increase in the amount of oil supplied as the pump speed increases. Become.

After the pump rotational speed further increases and the pressure guiding path 14 is closed by the first land 51 of the sub spool 5, the sub spool 5 is connected between the first and second lands 51 and 52 and the main spool 2. As shown in FIG. 3, between the second lands 22 and 23 of
The drain passage 15 communicates with the oil tank T and maintains the same pressure as the internal pressure of the oil tank T.

That is, in this state, the main spool 2
Is the internal pressure P _{1 of} the supply chamber A acting on the entire surface of the first land 21.
And the internal pressure P _{2 of} the delivery chamber B acting on the entire surface of the third land 23.
Due to the difference between and, it slides against the biasing force of the push spring 24. Therefore, the rate of increase of the pressure difference (P ₁ -P ₂ ) generated before and after the throttle plate 4 through which the entire amount of the delivered oil flows and the rate of increase of the sliding amount of the main spool 2 again correspond, and The amount of oil delivered to the destination is maintained constant at a smaller amount than a constant region in the range where the pump rotation speed is small.

The amount of oil delivered to the oil destination through the delivery chamber B by the operation of the apparatus of the present invention as described above increases in proportion to the increase of the rotational speed in the range where the rotational speed of the hydraulic pump is small, In the medium speed range, it is kept substantially constant regardless of the increase of the rotation speed, and in the larger rotation speed range, it decreases in proportion to the increase of the rotation speed. The characteristic of the delivered oil amount as shown in 8 is obtained. As described above, such characteristics are desirable in the hydraulic oil delivery system to the power steering apparatus.

In the device of the present invention, the above-mentioned characteristics of the amount of delivered oil are the first and second fixed throttles (throttle plate 3 and throttle plate 4) and the sub spool 5 which is not arranged in the oil passage of the delivered oil. Since it is realized by, it is possible to eliminate the variable throttle that causes the unstable operation, stably obtain the reduced portion of the delivered oil amount in FIG. 8, and reduce the number of parts requiring high dimensional accuracy. As a result, the number of processing and assembling steps can be significantly reduced.

Further, the oil supplied to the device of the present invention is turned from the discharge oil passage 10 at a substantially right angle and flows into the supply chamber A,
Further, it is only linearly flown into the delivery chamber B to be delivered, and due to such simplification of the flow path, for example, when pressure oil having a high viscosity is supplied at the time of starting the hydraulic pump in a cold region. Even if there is, the flow of the oil is not obstructed, and the generation of surge pressure due to this obstruction is suppressed, causing damage to the upstream hydraulic pump and the hydraulic piping leading to the oil destination, as well as annoyance. It is obvious that the generation of such abnormal noise (garbage noise) is prevented.

FIGS. 4, 5 and 6 are schematic views showing a second embodiment of the present invention. In this structure, the main spool 2 having the two lands 21 and 22 is used, and the spring support spool 6 having the two lands 61 and 62 inside the main spool hole 1a is located on the inner side of the main spool 2. Is slidably fitted inside, and a pressing spring 24 is interposed between the facing surfaces of the spring support spool 6 and the main spool 2 to urge them in directions away from each other, while the same as in the first embodiment. Further, the sub spool 5 is fitted in the sub spool hole 1b arranged in parallel with the main spool hole 1a so as to be slidable in the axial direction.

The pressure guiding path 16 which is open to the upstream side of the diaphragm plate 3 is communicated with the end surface of the sub spool hole 1b on the side of the first land 51, as in the first embodiment. The pressure guiding path 14 is also communicated with the first land 51 side between the second lands 51, 52 (the opening position of the pressure guiding hole 14 in the first embodiment) and has one end opened in the delivery chamber B. The other end is directly communicated with the rear side of the main spool 2 inside the main spool hole 1a, that is, with the spring support spool 6 without passing through the inside of the sub spool hole 1b.

Further, the communication passage 13 connects between the first and second lands 51 and 52 inside the sub spool hole 1b and the back side of the spring support spool 6, that is, near the bottom of the main spool hole 1a. And the drain path 15
Is similar to the first embodiment, the first and the first inside the sub spool hole 1b.
The second land 52 side between the second lands 51 and 52 and the second land 52
Of the spring support spool 6, and also between the first and second lands 61, 62 of the spring support spool 6.

In this structure, the main spool 2 responds to the pressure difference (P ₁ -P ₂ ) before and after the diaphragm plate 4, the sub spool 5 responds to the pressure P ₀ on the upstream side of the diaphragm plate 3, and the spring. The internal pressure P ₂ of the delivery chamber B introduced between the support spool 6 and the main spool 2 and the hydraulic pressure introduced between the first and second lands 51 and 52 of the auxiliary spool 5 through the communication passage 13. In response to the pressure difference, the separation distance from the main spool 2 changes according to this operation, and the urging force of the push spring 24 interposed between the spools 2 and 6 changes, and the main spool 2 slides. Changes occur in the balance of forces involved in movement.

FIG. 4 is similar to FIG. 1 in the first embodiment.
This shows a state in which the pump rotational speed is in a small range. In this case, the sub spool 5 is at the sliding position shown in the drawing, and the internal pressure P ₀ of the discharge oil passage 10 is introduced to the back side of the spring support spool 6. And the spring support spool 6 is pressed by the pressure at P _0.
Is close to the main spool 2, and the biasing force of the push spring 24 is large.

On the other hand, similarly to FIG. 2 in the first embodiment, in FIG. 5 showing the state at a medium pump speed, the discharge between the first and second lands 51, 52 of the auxiliary spool 5 is made. The oil tank T is in communication with the oil passage 10 as well as the oil passage T, and the oil tank T is moved in accordance with the sliding of the sub spool 5 as the discharge amount increases.
The communication area with the side increases, and the hydraulic pressure introduced to the back side of the spring support spool 6 gradually decreases, resulting in an increase in the separation distance between the spool 6 and the main spool 2. The decrease in the urging force of changes the above-mentioned force balance relating to the sliding of the main spool 2. Therefore,
The rate of increase in the amount of oil flowing through the diaphragm plate 4 and the rate of increase in the amount of sliding of the main spool 2 no longer correspond to each other, and the latter exceeds the former. As a result, the amount of oil delivered to the oil destination is increased by the number of pump revolutions. It will decrease conversely with the increase in the amount of oil supplied.

Further, as the pump speed further increases and the discharge hydraulic pressure P ₀ increases accordingly, sliding of the sub spool 5 advances, and only the drain path 15 is opened between the first and second lands 51 and 52. If the spring support spool 6 as shown in FIG.
Reaches the position where it comes into contact with the bottom surface of the main spool hole 1a, and the biasing force due to the push spring 24 does not change thereafter. Therefore, the increase rate of the pressure difference before and after the diaphragm plate 4 and the increase of the sliding amount of the main spool 2 are increased. When the pump rotation speed is small, the amount of oil delivered to the oil destination is maintained constant at a smaller amount than the constant region in which the pump rotation speed is small.

In the above embodiment, the sliding area of the sub spool 5 causes the pressure receiving area of the main spool 2 (first embodiment) or the urging force acting on the main spool 2 (second embodiment).
However, it goes without saying that the force balance in the main spool 2 may be changed by other means.

Further, in the above embodiments, the application example of the device of the present invention to the hydraulic pump which is the source of the operating hydraulic pressure of the power steering device has been described, but the applicable range of the device of the present invention is not limited to this. Needless to say, it can be applied to all kinds of fluid delivery circuits.

[0060]

As described in detail above, in the device of the present invention, the force balance involved in the operation of the main spool that adjusts the delivery flow rate depends on the operation of the sub spool that responds to the pressure on the upstream side of the first fixed throttle. The characteristic that is changed and the delivery flow rate decreases conversely in the range where the supply flow rate is high is obtained by the simple configuration without the variable throttle, and the unstable part of the characteristic obtained in the past due to the behavior of the variable throttle. Is eliminated, and the number of processing steps and assembly steps can be reduced with the simplification of the configuration. Also, the simplification of the flow path causes a gutter noise due to the surge pressure, and the risk of damage to the pump and the piping system. The present invention has excellent effects, such as eliminating the above problems.

[Brief description of drawings]

FIG. 1 is a schematic view showing an operating state at a small flow rate in the first embodiment of the device of the present invention.

FIG. 2 is a schematic diagram showing an operating state at a medium flow rate in the first embodiment of the device of the present invention.

FIG. 3 is a schematic diagram showing an operating state at a large flow rate in the first embodiment of the device of the present invention.

FIG. 4 is a schematic diagram showing an operating state at a small flow rate in the second embodiment of the device of the present invention.

FIG. 5 is a schematic view showing an operating state at a medium flow rate in the second embodiment of the device of the present invention.

FIG. 6 is a schematic diagram showing an operating state at a large flow rate in the second embodiment of the device of the present invention.

FIG. 7 is a schematic diagram showing a configuration of a conventional flow rate control device.

FIG. 8 is a graph showing the characteristic of the amount of delivered oil obtained by the operation of the device of the present invention and the conventional flow control device.

[Explanation of symbols]

 1a Main spool hole 1b Sub spool hole 2 Main spool 3 Throttle plate 4 Throttle plate 5 Sub spool 6 Spring support spool 10 Discharge oil passage 11 Return oil passage 13 Communication passage 14 Pressure passage 15 Drain passage 16 Pressure passage A Supply chamber B Delivery room T oil tank

Claims (3)

[Claims] 1. A first fixed throttle through which a supply fluid from a pump flows, a second fixed throttle located downstream of the fixed throttle and through which a delivery fluid to a delivery destination flows, and a second fixed throttle. The pressure difference generated before and after the fixed throttle responds to the force balance between this and the constantly acting biasing force, and the amount of the supplied fluid is circulated to the suction side of the pump to the destination. And a sub-spool that responds to the pressure on the upstream side of the first fixed throttle to change the force balance. 2. The flow control device according to claim 1, wherein the pressure receiving area of the pressure difference in the main spool is adjusted by the operation of the sub spool. 3. The flow control device according to claim 1, wherein the urging force acting on the main spool is adjusted by the operation of the sub spool.