JPH10203386A - Load-sensitive flow controller for power steering - Google Patents

Abstract

(57) [PROBLEMS] To provide a flow rate control device for a pump rotation speed-responsive power steering device, wherein a pressure fluid discharged from a pump can be supplied to the power steering device even according to a steering load.
In addition to further energy saving, a stable steering feeling can be obtained even at the time of rapid turning in a high speed range. SOLUTION: A pressure fluid discharged from a pump 3 whose pump discharge flow rate increases in accordance with an increase in the pump rotation speed is supplied to a vehicle power steering device according to a load through a fixed throttle passage 14 in a supply passage. Then, the excess pressure fluid is supplied to the bypass passage 7.
A load-responsive flow control for a power steering device in which a flow is returned to a suction side 3b of a pump 3 through a first valve chamber 10 of the flow control spool valve by a flow control spool valve for adjusting an opening degree of the pump. In the device 1, the first valve chamber 10 and the bypass passage 7
A load sensing valve 37 is provided in a return passage 36 connecting the return passage 36 and the load sensing valve 37 is operated by the pressure of the pressure fluid downstream of the fixed throttle passage 14 so as to open and close the return passage 36. A load-responsive flow control device for a power steering device, characterized in that:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load-sensitive flow control device for a power steering device of a vehicle, and more particularly to a flow control device for a pump speed-sensitive type, that is, an engine speed-sensitive type power steering device. By enabling the pressure fluid discharged from the pump to be supplied to the power steering device according to the steering load, further energy savings can be achieved, and a stable steering feeling can be obtained even when turning sharply in a high-speed range. The present invention relates to a load-responsive flow control device for a power steering device, which is capable of performing the following.

[0002]

2. Description of the Related Art As a conventional flow rate control device for a pump speed-sensitive power steering device, there is one disclosed in Japanese Utility Model Laid-Open Publication No. 7-28779. In this case, as shown in FIG. 8, a hydraulic pump 03 driven by a belt from an engine (not shown) is integrally incorporated into a casing 02 of the flow control device 01, and a discharge flow rate of the hydraulic pump 03 is: It increases and decreases in proportion to the engine speed.

The casing 02 is provided with a spool receiving hole 05 into which a flow rate adjusting spool 04 can be slidably inserted. The spool receiving hole 05 is opened at a predetermined distance in the axial direction. A discharge passage 06 and a bypass passage 07 are formed.
a, and the bypass passage 07 is communicated with a suction port (not shown) of the hydraulic pump 03.

[0004] Further, a cylindrical pressure oil supply hole 08 for supplying pressure oil to a power steering device (not shown) is formed in parallel with the spool storage hole 05 by displacing the center axis of the spool storage hole 05, A connector 09 for connecting a pipe communicating with the power steering device is fitted in the pressure oil supply hole 08.

Further, the spool housing hole 05 is partitioned into a first valve chamber 010 and a second valve chamber 011 by a flow rate adjusting spool 04, and the second valve chamber 011 presses the flow rate adjusting spool 04. A spring 012 is interposed.
When the leading end of the flow adjustment spool 04 abuts on the bottom surface of the spool housing hole 05 due to the spring force, the communication between the discharge passage 06 and the bypass passage 07 is established by the flow adjustment spool 04 in the first valve chamber 010. It is designed to be shut off.

Further, the bottom of the spool housing hole 05 and the upper portion of the pressure oil supply hole 08 are communicated with each other through a fixed throttle passage 014 having a fixed orifice 013, and the bottom of the spool housing hole 05 and the pressure oil supply hole 08 are connected. Is communicated with a lower portion of the lower part by a communication passage 015.

Further, a cylindrical outer barrel (cylindrical valve unit casing) 016 is fitted into the pressure oil supply hole 08, and a control sub-spool 018 is slidably fitted into a center hole 017 of the outer barrel 016. The center hole 017 is closed by the cap 019, and the spring 020 is interposed between the outer barrel 016 and the control sub-spool 018 in the center hole 017 of the outer barrel 016. The control sub-spool 018 is pressed against the cap 019.

[0008] Furthermore, the upper distal end converging portion 021 of the outer barrel 016 is cut off in a plane, and the upper base end 022 is parallel to the center hole 017, and the second valve chamber 011 of the spool accommodating hole 05 and the second valve chamber 011. An engagement hole 023 is formed in the extension of the communication passage 024 that communicates with the upper distal end junction portion 021. The engagement hole 023 is formed by a spring pin 025 formed of a rectangular thin steel plate in a cylindrical shape.
The outer barrel 016 is positioned within the pressure oil supply hole 08 by the spring pin 025.

In addition, a communication hole 026 for communicating the communication passage 015 with the center hole 017 is formed in a lower portion of the outer barrel 016.
In the upper part of the outer barrel 016, two variable orifice holes 027 for communicating the center hole 017 of the outer barrel 016 and the confluent portion 021 are formed side by side in the circumferential direction. The variable orifice hole 027, the center hole 017, and the communication hole 026 form a variable orifice passage.

In the center hole 017 of the outer barrel 016, the control hydraulic chamber 028 sandwiched between the control sub-spool 018 and the cap 019 and the discharge port 03a of the hydraulic pump 03
The oil passage 029 is communicated with the oil passage 03e through the control hydraulic chamber 028.
The high pressure hydraulic P ₁ from the hydraulic P ₂ is adapted to be introduced is guided to the central hole 017 through the communication hole 026 from the first valve chamber 010.

Further, a relief guide valve 030 is provided in the flow rate adjusting spool 04, and when the pressure of the merging portion 021 rises above a predetermined pressure, the increased pressure is formed in the spring pin 025. Throttle passage 025a and communication passage
024 to the second valve chamber 011 and the relief guide valve 03
When 0 is opened, the spool for flow adjustment 04 moves to the left, opening the bypass passage 07 and returning the amount of oil discharged from the hydraulic pump 03 to its suction port.

[0012] Since the conventional pump is configured as described above, when the hydraulic pump 03 is stopped and no hydraulic oil is generated, the flow rate adjusting spool 04 and the control sub-spool 018 are connected to the spring 012 and the spring 012. With the spring force of 020, it is located at the position shown in FIG.
06 and the bypass passage 07 are shut off, and the variable orifice hole 027 is opened.

In this state, when the hydraulic pump 03 rotates at a predetermined low speed Na or less, the hydraulic pump 03
The pressure oil generated in the
05 flows into the first valve chamber 010, and a part of the pressure oil in the first valve chamber 010 is supplied to the fixed throttle passage 01 having the fixed orifice 013.
4 and flows into the junction 021 via the first valve chamber.
The remaining portion of the pressure oil in 010 passes through a communication passage 015, a communication hole 026, a center hole 017, and a variable orifice hole 027 to a junction portion 021.
During this time, the pressure oil pressure in the first valve chamber 010 rises, and the flow control spool 04 moves to the left overcoming the spring 012. Since the communication remains interrupted, the pressure oil merged in the merging portion 021 is supplied to the power steering device through the passage 031 in the connector 09 and a pipe (not shown),
As shown at 0-a in FIG. 9, pressure oil having an oil amount substantially proportional to the rotation speed of the hydraulic pump 03 is supplied to the power steering device.

The hydraulic pump 03 operates at a predetermined low speed N.
a, when the motor rotates in the medium speed region until the rotation speed reaches the predetermined rotation speed Nb, which is larger than the rotation speed Nb.
At elevated pressure oil pressure P ₂ of the first valve chamber 010, moved to the flow rate regulating spool 04 further leftward, the bypass passage 07 communicates with the discharge passage 06, the communication opening area of the hydraulic pump 03 As shown in FIGS. 9A and 9B, the pressure oil is supplied to the power steering device at a substantially constant flow rate so as to increase in response to the increase in the discharge flow rate. As described above, a light feeling of steering of the power steering device at the time of low / medium speed traveling can be obtained.

Furthermore, the hydraulic pump 03 exceeds a predetermined medium-speed rotational speed Nb, the pressure difference between the pressure oil pressure P ₂ of the control hydraulic chamber pressure oil pressure P ₁ and the central bore 017 in 028 is expanded, The leftward pressing force of the control sub-spool 018 due to the pressure difference overcomes the spring force of the spring 020, and the control sub-spool 01
8 moves to the left, the opening area of the variable orifice hole 027 is reduced, and the communication passage 015 and the communication hole 026 extend from the first valve chamber 010.
Since the flow rate of the pressure oil flowing into the confluent portion 021 through the central hole 017 and the variable orifice hole 027 is reduced,
As shown in -c, the amount of oil supplied to the power steering apparatus decreases in response to the increase in the rotation speed of the hydraulic pump 03.

Further, when the hydraulic pump 03 reaches a predetermined high speed Nc, the hydraulic pressure P ₁ in the control hydraulic chamber 028 is increased.
The control sub-spool 018 further moves to the left due to an increase in the pressure difference between the pressure and the hydraulic pressure P ₂ in the center hole 017, the variable orifice hole 027 is completely closed, and a fixed throttle is provided to the power steering device. Only the pressure oil that has passed through passage 014 is supplied, and
In the second valve chamber 011, the pressurized oil in the converging portion 021, which has passed through the fixed orifice 013 and the pressure has decreased to P ₄ , is throttled in an oil passage 025 a.
Since being introduced via the communicating passage 024, increases the pressure difference between the pressure oil pressure P ₂ and P ₃ are further flow regulating spool
04 moves further to the left, the recirculation flow rate in the bypass passage 07 increases again, and thus the amount of oil supplied to the power steering device is low, as shown in FIG. Kept in quantity. As described above, a sense of stability of the steering of the power steering device during high-speed running can be obtained.

[0017]

As described above, in the prior art, the supply of pressure oil to the power steering device is performed depending on the number of rotations of the hydraulic pump 03.
When the rotational speed of 03 is in the middle / low speed range, the power steering device is not steered and the steering load is applied even if the power steering device is steered and the steering load is applied. Even if it is not in a state, a relatively high level of a predetermined amount of pressure oil depending on the rotation speed of the hydraulic pump 03 is supplied from the flow control device to the power steering device, and the power steering device is turned off. Even though the steering is not steered and the steering load is not applied, the hydraulic pump 03 wastes power because the relatively high level of the predetermined amount of pressure oil is supplied to the power steering device. Will be consumed.

When the rotational speed of the hydraulic pump 03 is in a high-speed range, a certain amount of low-level pressure oil is supplied to the power steering device. In a situation where the vehicle is suddenly steered, a considerable load is applied to the power steering device, and the driver may feel a sense of being caught by the steering operation. However, even in such a situation, since only a fixed amount of the low-level pressure oil is supplied to the power steering apparatus, the feeling of the steering operation is not eliminated.

[0019]

SUMMARY OF THE INVENTION The present invention is directed to a load-sensitive flow control device for a power steering device which solves the above-mentioned problems. The pressure fluid discharged from the pump whose pump discharge flow rate increases in accordance with the rotation speed is supplied to the power steering device of the vehicle according to the load via the fixed throttle passage in the supply passage, and the excess pressure fluid is discharged. A load-responsive flow control device for a power steering device, wherein a flow is returned to a suction side of a pump through a first valve chamber of the flow control spool valve by a flow control spool valve for adjusting an opening degree of a bypass passage. At
A load sensing valve is provided in a return passage connecting the first valve chamber and the bypass passage, and the load sensing valve is operated by the pressure of the pressure fluid downstream of the fixed throttle passage to open and close the return passage. A load-responsive flow control device for a power steering device, characterized in that the flow control device is adjusted.

According to the first aspect of the present invention, the return passage connecting the first valve chamber of the flow rate adjusting spool valve and the bypass passage in the pressure oil supply passage is formed as described above. The pressure of the pressure fluid downstream of the fixed throttle passage is adjusted by a load sensing valve operated by the pressure of the pressure fluid downstream of the fixed throttle passage, and the pressure of the pressure fluid downstream of the fixed throttle passage is the power required in the power steering device. Since this reflects the assist force (steering load), when a pressure fluid for power assist is required in the power steering device (when a steering load occurs), the load is changed to the pressure of the pressure fluid. The load sensing valve sensed as fluctuation closes the return passage, and the pressure fluid passing through the flow regulating spool valve and the fixed throttle passage is
The whole amount is supplied to the power steering device.

When the power steering device does not require pressure fluid for power assist (when no steering load is generated), the return passage is not provided because the load sensing valve does not sense the pressure fluctuation of the pressure fluid. A part of the pressure fluid in the first valve chamber of the flow rate adjustment spool valve flows into the bypass passage through the return passage and is returned to the pump suction side by being left open, so that the power steering The amount supplied to the take-off device is reduced.

As a result, the supply of the pressurized fluid is reduced when there is no steering load, especially in the middle / low speed range of the pump rotation speed, so that unnecessary consumption of pump power is suppressed and energy saving is achieved. . Also, in the high-speed range of the pump rotation speed, when the power steering device is suddenly steered and a steering load is generated, the necessary pressure fluid is supplied, so that the feeling that the steering is not caught is not felt, and the stable operation is achieved. A steering feeling can be obtained.

Further, the pressure of the pressure fluid downstream of the fixed throttle passage directly reflects the power assist force (steering load) required in the power steering device. Control of the supply of the pressure fluid to the power steering device by the load sensing valve actuated by the pressure sensing valve operated by the pressure sensing valve actuated by the pressure of the pressure fluid in the first valve chamber upstream of the fixed throttle passage. Done more accurately.

Further, by configuring the invention according to claim 1 as described in claim 2, the configuration of the load sensing valve is simplified.

[0025]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a first embodiment of the present invention; FIG. FIG. 1 is a diagram for explaining the overall configuration of a load-responsive flow control device for a power steering device according to the present embodiment. FIG. FIG. 4 is an enlarged view of a part, in which the apparatus is in a stationary state.

In these figures, a hydraulic pump 3 driven by a belt from an engine (not shown) is integrally incorporated into a casing 2 of the flow control device 1, and the discharge flow rate of the hydraulic pump 3 is reduced by the engine speed. It increases and decreases in proportion.

The casing 2 is provided with a spool receiving hole 5 into which the flow rate adjusting spool 4 can be slidably inserted. The spool receiving hole 5 is opened in the spool receiving hole 5 at a predetermined distance in the axial direction. A discharge passage 6 and a bypass passage 7 are formed, and the discharge passage 6 is connected to the discharge port 3 of the hydraulic pump 3.
a, and the bypass passage 7 is connected to a suction port 3 b of the hydraulic pump 3.

Further, the spool housing hole 5 is partitioned into a first valve chamber 10 and a second valve chamber 11 by a flow control spool 4, and a spring for pressing the flow control spool 4 is provided in the second valve chamber 11. When the distal end of the spool 4 for flow adjustment is in contact with the bottom surface of the spool housing hole 5 by the spring force of the spring 12, the communication between the discharge passage 6 and the bypass passage 7 is established by the first valve chamber. Spool 4 for flow adjustment in 10
Is to be shut off.

The bottom of the spool housing hole 5 and a pressure oil supply pipe 32 for supplying pressure oil to the power steering device communicate with a fixed throttle passage 14 having a fixed orifice 13. The second valve chamber 11 and the pressure oil supply pipe 32 communicate with each other through a communication path 34 having a throttle oil path 33.

Further, a relief guide valve 30 is provided in the flow rate adjusting spool 4, and when the pressure in the pressurized oil supply pipe 32 rises above a predetermined pressure, the increased pressure is transmitted to the communication passage. It is led to the second valve chamber 11 via 34 and the throttle oil passage 33, and when the relief guide valve 30 is opened, the flow adjustment spool 4 moves to the left, opening the bypass passage 7, and
The amount of oil discharged from the hydraulic pump 3 can be returned to the suction port 3b.

As described above, the flow rate adjusting spool 4
The spool accommodation hole 5, the various passages 6, 7, 14, and 34 communicating with the spool accommodation hole 5, the relief guide valve 30, and the like constitute a flow rate adjusting spool valve.

Further, the first of the flow rate adjusting spool valves
The valve chamber 10 and the bypass passage 7 communicate with each other via a return passage 36. A load sensing valve 37 is provided in the middle of the return passage 36, and the return passage 36 is actuated by the operation of the load sensing valve 37. The opening / closing is adjusted, so that a part of the pressure oil in the first valve chamber 10 can return to the bypass passage 7 via the return passage 36.

In the load sensing valve 37, a sub-spool valve element 41 is accommodated in a sub-spool accommodation hole 40, and a sub-spool accommodation hole partitioned by the sub-spool valve element 41 is provided.
One of the control hydraulic chambers 42 in 40 is connected to a communication passage via a communication passage 47.
The throttle oil passage 33 communicates upstream of the throttle oil passage 33, and further communicates with the communication passage.
Connection portion 35 between fixed throttle passage 14 and pressure oil supply pipe 32 via 34
The other hydraulic chamber 43 communicates with the communication passage 39 via the communication passage 48, which is a portion downstream of the load sensing valve 37 of the return passage 36, and further communicates with the bypass passage via the communication passage 39. 7 is connected.

The sub-spool receiving hole of the load sensing valve 37
40 has an opening formed with a suction port 44 and a discharge port 45, and the suction port 44 is connected to a load sensing valve 37 of a return passage 36.
The discharge port 45 is connected to the bypass valve 7 via the communication path 39 via the communication path 38 which is a more upstream side part.

Further, the sub-spool valve element 41 has an annular groove.
When the sub-spool valve element 41 moves up and down in the figure, communication between the suction port 44 and the discharge port 45 is blocked or opened by the annular groove 41a. The sub-spool valve element 41 is
Is always urged upward by a spring 46 disposed at the center.

A fixed orifice 49 is provided in the communication passage 38, and the fixed orifice 49 allows the first valve chamber to be opened.
A part of the pressure oil in 10 is reduced to approximately the suction pressure of the hydraulic pump 3, and is returned to the suction port 3b of the hydraulic pump 3 via the return passage 36, the bypass passage 7 and the return passage 36. .

Since the load sensing valve 37 is configured as described above, the pressure oil in the connection portion 35 is introduced into the control hydraulic chamber 42, and its pressure (this is caused by the pressure in the pressure oil supply pipe 32) equal to the pressure P ₄ of the pressure oil.) becomes higher than a predetermined pressure, moved downward in FIG sub spool valve body 41 against the spring force of the spring 46, the discharge port and the suction port 44 by an annular groove 41a The communication with the first valve chamber 10 is thereby cut off.
The communication between the pump and the bypass passage 7 is interrupted, and the return of the pump discharge fluid via the return passage 36 connecting these is stopped.

Next, the operation of the present embodiment will be described. First, when the hydraulic pump 3 is stopped and no hydraulic oil is generated, the flow rate adjusting spool 4 and the sub-spool valve element 41 are shown in FIGS. 1 and 2 by the spring force of the spring 12 and the spring 46. The communication between the discharge passage 6 and the bypass passage 7 through the first valve chamber 10 is cut off, and the return passage 36 between the first valve chamber 10 and the bypass passage 7 is connected. Communication is open.

In this state, when the hydraulic pump 3 rotates at a predetermined low-speed rotation speed Na 'or lower which is lower than a predetermined low-speed rotation speed Na (substantially idling rotation speed), the pressure oil generated by the hydraulic pump 3 From the discharge port 3a to the discharge passage 6
And a part of the pressure oil flowing into the first valve chamber 10 flows through the fixed throttle passage 14 having the fixed orifice 13 into the connection portion 35. I do.

Here, the pressure P of the pressure oil in the connection portion 35
₄ does not yet move the sub-spool valve element 41 downward against the spring force of the spring 46, and therefore, the suction port 44 and the discharge port 45 communicate with each other.
The remainder of the pressure oil that has flowed into the valve chamber 10 is returned to the suction port 3b of the hydraulic pump 3 through the return passage 36 and the bypass passage 7, and only a part of the pressure oil in the first valve chamber 10 is discharged. As described above, the fluid flows into the connection portion 35 through the fixed throttle passage 14, and is further supplied to the power steering device via the pressure oil supply pipe 32 therefrom.

During this time, the pressure P ₂ of the pressure oil in the first valve chamber 10 and the pressure P ₃ of the pressure oil in the second valve chamber 11 (this pressure is
The almost equal to the pressure P ₄ of the pressure oil in the connection portion 35 when no pressure oil flow within. ), The flow control spool 4 does not move to the left against the spring force of the spring 12, so that the first valve chamber 10 between the discharge passage 6 and the bypass passage 7 does not move. , The communication of the pressure oil is still interrupted, so that a part of the pressure oil is supplied to the power steering apparatus as described above (see FIG. 3).

As a result, part of the pressure oil in the first valve chamber 10
The amount supplied to the power steering device via the fixed throttle passage 14, the connection portion 35, and the pressure oil supply pipe 32 increases as the rotational speed of the hydraulic pump 3 increases, as shown by 0-a 'in FIG. Increase in proportion.

Next, when the hydraulic pump 3 rotates beyond a predetermined low-speed rotation speed Na ', the operation differs as follows according to the steering state of the power steering device. That is, in a situation in which the power steering device is not steered and no steering load is generated, the pressure P ₄ of the pressure oil in the connection portion 35 is determined by the power steering of the hydraulic oil according to the rotation speed of the hydraulic pump 3. The pressure remains low enough to circulate the closed circuit between the device and the reservoir tank, and the increase is slow. Accordingly, the sub-spool valve element 41 maintains the initial state, and the suction port 44 and the discharge port 45
The remaining pressure oil in the valve chamber 10 is returned to the return passage 36 and the bypass passage 7.
Is returned to the suction port 3b of the hydraulic pump 3 via the valve, and only a part of the pressure oil in the first valve chamber 10
5. The power is supplied to the power steering device via the pressure oil supply pipe 32.

However, the pressure P ₂ of the pressure oil in the first valve chamber 10 and the second pressure
Since the pressure difference between the hydraulic fluid pressure P ₃ of the valve chamber 11 increases rapidly, and moved leftward flow regulating spool 4 against the spring force of the spring 12, the discharge passage 6 and the bypass passage 7
Is released through the first valve chamber 10 (see FIG. 4).

As a result, a part of the pressure oil in the first valve chamber 10 is returned from the first valve chamber 10 to the suction port 3b of the hydraulic pump 3 through the bypass passage 7, and the remaining pressure is further reduced. Only part of the oil flows from the first valve chamber 10 through the fixed throttle passage 14 into the connection 35. Here, the amount of recirculation from the first valve chamber 10 to the suction port 3b of the hydraulic pump 3 through the bypass passage 7 increases in proportion to an increase in the rotation speed of the hydraulic pump 3, so that the connection portion 35 Is substantially constant irrespective of an increase in the rotation speed of the hydraulic pump 3.

Then, the entire amount of the pressure oil in the connection portion 35 having the substantially constant inflow amount is supplied to the power steering device via the pressure oil supply pipe 32. For this reason, the amount of pressure oil supplied to this power steering device is, as shown in a′-d of FIG.
Regardless of the increase in the number of revolutions of the hydraulic pump 3, it is maintained at a substantially constant low level.

On the other hand, in a situation where the power steering device is steered and a steering load is generated, the low-speed rotation range until the rotation speed of the hydraulic pump 3 reaches the predetermined low-speed rotation Na at that time. when in the connecting portion pressure oil pressure P ₄ of the 35 rises, the pressure P ₂ of the pressure oil in the first valve chamber 10 on the upstream side beyond fix the throttle passage 14 from which also rises, the Since the pressure P ₃ of the pressure oil in the second valve chamber 11 also increases, the pressure difference between the pressure P ₃ of the pressure oil in the second valve chamber 11 and the pressure P ₂ of the pressure oil in the first valve chamber 10 decreases. The spool 4 for adjusting the flow rate is
It is urged by 12 to move rightward, and again shuts off the communication between the discharge passage 6 and the bypass passage 7 via the first valve chamber 10.

On the other hand, since the pressure P ₄ of the pressurized oil in the connection portion 35 whose pressure has increased is large enough to move the sub-spool valve body 41 downward against the spring force of the spring 46, The sub-spool valve element 41 has a communication passage 34 in the connection portion 35,
Moves downward by being pushed by the pressure P ₄ of the pressure oil control hydraulic chamber 42 which communicates through the communication passage 47, and cuts off the communication between the suction port 44 and discharge port 45, thereby, the first The communication between the valve chamber 10 and the bypass passage 7 via the return passage 36 is cut off (see FIG. 5).

As a result, the entire pressure oil generated by the hydraulic pump 3 is discharged from the discharge passage 6, the first valve chamber 10, and the fixed throttle passage.
14 into the connection 35, from which the pressure oil supply pipe 32
And is supplied to the power steering device through
The supply oil amount increases substantially in proportion to the increase in the rotation speed of the hydraulic pump 3, as shown by a'-a in FIG.

Then, under the same situation, the hydraulic pump 3
When the rotational speed is further increased beyond a predetermined low-speed rotation speed Na, further increases the pressure P ₂ of the pressure oil in the first valve chamber 10,
Since the pressure difference from the pressure P ₃ of the pressure oil in the second valve chamber 11 increases, the flow adjustment spool 4 moves leftward against the spring force of the spring 12, and Passage 7
Is released through the first valve chamber 10 (see FIG. 6).

As a result, the increase in the pressure oil generated in the hydraulic pump 3 is returned from the first valve chamber 10 to the suction port 3b of the hydraulic pump 3 through the bypass passage 7, and the amount of the increase is equal to the rotation of the hydraulic pump 3. The first valve chamber 1
0, the amount of pressure oil supplied to the power steering device via the fixed throttle passage 14, the connection portion 35, and the pressure oil supply pipe 32, as shown in ae of FIG. Despite the further increase in, it remains at a nearly constant high level.

If the steering state fluctuates under the two different steering conditions of the power steering apparatus as described above, for example, the power steering apparatus is not steered and the power is changed from a state where no steering load is generated. Assuming that the steering device is steered to change to a state in which a steering load is generated, the supply amount of the pressure oil to the power steering device at that time increases beyond the amount indicated by a′-d in FIG. Further, for example, if the power steering device is steered to change from a state in which a steering load is generated to a state in which the power steering device is not steered and no steering load is generated, the power steering device at that time is changed. The amount of pressure oil supplied to
In the case of any state change, the supply amount of the pressure oil to the power steering device depends on the rotational speed of the hydraulic pump 3 at that time. According to the magnitude of the steering load, the amount indicated by a'-ae in FIG. 7 is maximized, and the amount indicated by a'-d is minimized, and a'-a
It is given by any point in the area enclosed by -eda '.

On the other hand, the characteristic of the amount of oil supplied to the power steering device in the conventional flow rate control device for a pump rotation speed-responsive power steering device shown in FIG. Since it is given by the broken line of 0-abcd in FIG. 9, when this is compared with the above-described oil supply characteristic in the present embodiment (see FIGS. 7 and 9),
When the rotation speed of the hydraulic pump 3 is in a middle / low speed range equal to or lower than the rotation speed near the predetermined medium speed rotation speed Nb, the characteristic value a'-a-
The supply oil amount is smaller than bc, and from the viewpoint of the pump power, wasteful consumption is suppressed by the reduced supply oil amount, and energy saving is achieved.

When the rotation speed of the hydraulic pump 3 exceeds the rotation speed near the high-speed rotation speed Nc and is in a high-speed range, even if the power steering device is rapidly turned and the steering load increases rapidly, In response to the sudden increase in the load, an amount of pressurized oil that is larger than the characteristic value bcd in the conventional one is supplied to the power steering device. The feeling of snagging of the steering operation is eliminated.

In this embodiment, the control hydraulic chamber 42, which is one of the chambers in the sub-spool housing hole 40, is connected to the connection portion 35 downstream of the fixed throttle passage 14 via the communication passages 47 and 34. The communication is not limited to this, but may be any communication provided that the communication is performed with a passage downstream of the fixed orifice 13 provided in the fixed throttle passage 14. Such a case is also included in the embodiment of the present invention. .

In any case, the pressure of the hydraulic oil introduced into the control hydraulic chamber 42 directly reflects the power assisting force (steering load) required in the power steering device. The control of the supply amount of the pressure oil to the power steering device by the load sensing valve 37 operated by the oil pressure is performed, for example, by controlling the load operated by the pressure of the pressure oil in the first valve chamber 10 upstream of the fixed orifice 13. The same control by the sensing valve 37 is performed more accurately.

In this embodiment, the return passage 36
Although the downstream end (the downstream end of the communication passage 39) is connected to the bypass passage 7, the downstream end may be connected to the suction port 3b of the hydraulic pump 3 instead. Included in the embodiment.

[Brief description of the drawings]

FIG. 1 is a view for explaining the overall configuration of a load-responsive flow control device for a power steering device according to an embodiment of the present invention described in claims 1 and 2, and is a part of the overall configuration. FIG.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a view showing an operation state of the load-sensitive flow control device for a power steering device in the embodiment of FIG. 1;

FIG. 4 shows the embodiment of FIG. 1 with different operating states;
FIG.

FIG. 5 is a view similar to FIG. 3 showing a further different operating state of the embodiment of FIG. 1;

FIG. 6 is a view similar to FIG. 3 showing a further different operating state of the embodiment of FIG. 1;

FIG. 7 is a diagram showing a flow control characteristic of the load-responsive flow control device for a power steering device in the embodiment of FIG. 1 in comparison with a conventional flow control device.

FIG. 8 is a diagram showing a conventional example.

FIG. 9 is a diagram showing flow control characteristics of a conventional example.

[Explanation of symbols]

1. Flow control device 2. Casing 3. Hydraulic pump
3a ... discharge port, 3b ... suction port, 4 ... flow rate adjustment spool, 5 ... spool accommodation hole, 6 ... discharge passage, 7 ... bypass passage, 10 ... first valve chamber, 11 ... second valve chamber, 12 ... spring ,
13 ... fixed orifice, 14 ... fixed throttle passage, 30 ... relief guide valve, 32 ... pressure oil supply pipe, 33 ... throttle oil passage, 34 ... communication passage,
35 connection section, 36 return path, 37 load sensing valve, 38 communication path (upstream side), 39 communication path (downstream side), 40 sub-spool housing hole, 41 sub-spool valve element, 41a ... Annular groove, 42…
Control hydraulic chamber, 43… Hydraulic chamber, 44… Suction port, 45… Discharge port, 46… Spring, 47… Communication passage, 48… Communication passage, 49…
Fixed orifice.

Claims (2)

[Claims] 1. A pressure fluid discharged from a pump whose pump discharge flow rate increases in accordance with an increase in the pump rotation speed is supplied to a power steering device of a vehicle according to a load through a fixed throttle passage in a supply passage. For a power steering device, the excess pressure fluid is returned to the suction side of the pump via a first valve chamber of the flow rate adjusting spool valve by a flow rate adjusting spool valve for adjusting the opening degree of the bypass passage. In the load-responsive flow control device, a load sensing valve is provided in a return passage connecting the first valve chamber and the bypass passage, and the load sensing valve is operated by a pressure of a pressure fluid downstream of the fixed throttle passage. A load-responsive flow control device for a power steering device, wherein the return passage is opened and closed. 2. The load sensing valve according to claim 1, wherein a sub-spool valve body is housed in a sub-spool housing hole, and one chamber in the sub-spool housing hole partitioned by the sub-spool valve body is
The fixed throttle passage in the supply passage is communicated with the downstream side from the fixed throttle passage,
2. The power steering device according to claim 1, wherein the other chamber is communicated with the bypass passage, and an annular groove formed in the sub-spool valve body controls opening and closing of the return passage. Load-responsive flow control device.