JPH10181619A - 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, in the load-sensitive flow control device 1 for a power steering device, the excess pressure fluid is returned to the suction side 3b of the pump 3 by the flow rate adjustment spool valves 4 and 5 for adjusting the opening degree of the bypass passage 7. A load sensing valve 37 is provided in a return passage 36 that connects the bypass passage 7 to a downstream side of the fixed throttle passage 14 in the supply passage, and the load sensing valve 37 is connected to the pressure of the pressure fluid downstream of the fixed throttle passage 14. The load-responsive flow control device for a power steering device is characterized in that the return passage 36 is adjusted to open and close by operating the return passage.

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 increase in the number of revolutions is supplied to the power steering device of the vehicle according to the load through the fixed throttle passage in the supply passage, and the excess pressure fluid is bypassed. In a load-responsive flow control device for a power steering device, wherein a flow is adjusted to return to a suction side of a pump by a flow adjustment spool valve that adjusts an opening degree of a passage, a downstream side of a fixed throttle passage in the supply passage is connected to the downstream side. A load sensing valve is provided in a return passage connecting to 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-sensitive flow controller for power steering apparatus according to.

According to the first aspect of the present invention, the return passage connecting the downstream side of the fixed throttle passage and the bypass passage in the pressure oil supply passage is formed of the fixed throttle passage. The pressure of the pressure fluid on the downstream side of the fixed throttle passage is adjusted by a load sensing valve operated by the pressure of the pressure fluid on the downstream side. Load), when pressure fluid for power assist is needed in the power steering device (when a steering load is generated), the load is sensed as a pressure fluctuation of the pressure fluid. A load sensing valve closes the return passage, and all of the pressure fluid that has passed through the fixed throttle passage 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. It is kept open, and a part of the pressure fluid that has passed through the fixed throttle passage flows into the bypass passage through the return passage, and is returned to the pump suction side. 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. The control of the supply amount of the pressure fluid to the power steering device by the load sensing valve operated by the pressure sensor is performed more accurately than the similar control by the load sensing valve operated by the pressure of the pressure fluid upstream of the fixed throttle passage.

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, and is a partially cutaway view, and FIG. FIG. 3 is a diagram showing a case where 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.

Further, the connection portion 35 between the fixed throttle passage 14 and the pressure oil supply pipe 32 and the suction port 3b of the hydraulic pump 3 at the downstream end of the bypass passage 7 are communicated via a return passage 36, and the return is performed. A load sensing valve 37 is provided in the middle of the passage 36, and the return passage 36 is opened and closed by the operation of the load sensing valve 37, whereby a part of the pressure oil passing through the fixed throttle passage 14 is removed. It is possible to return to the suction port 3b of the hydraulic pump 3 via the return passage 36 without flowing through the pressure oil supply pipe 32.

In the load sensing valve 37, a sub-spool valve body 41 is housed in a sub-spool housing hole 40, and a sub-spool housing hole partitioned by the sub-spool valve body 41.
One of the control hydraulic chambers 42 is provided with a communication passage 38 which is a portion of the return passage 36 upstream of the load sensing valve 37 via a communication passage 47.
And the other hydraulic chamber 43 is connected to the connecting portion 35 via the communication passage 38, and the other hydraulic chamber 43 is connected to the return passage 36 via the communication passage 48 at a downstream side of the load sensing valve 37. aisle
The hydraulic pump 3 is communicated with the hydraulic pump 3 through the communication passage 39.
To the suction port 3b. In addition, a suction port 44 and a discharge port 45 are formed in the sub-spool housing hole 40, and the suction port 44 communicates with the connecting portion 35 through the communication passage 38. , The communication passage 39
Through the suction port 3b of the hydraulic pump 3.
Further, an annular groove 41a is formed in the sub-spool valve element 41, and when the sub-spool valve element 41 moves up and down in the drawing, communication between the suction port 44 and the discharge port 45 is established by the annular groove 41a. It is designed to be shut off or open.

A fixed orifice 49 is provided downstream of the connection between the communication passage 38 and the communication passage 47, and a part of the pressure oil in the connection portion 35 is substantially hydraulically fixed by the fixed orifice 49. The pressure is reduced to the suction pressure of the pump 3, and the pressure can be returned to the suction port 3 b of the hydraulic pump 3 via 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 the pressure (the pressure in the pressure oil supply pipe 32) is the same as 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, and the suction port 44 by an annular groove 41a The communication with the discharge port 45 is cut off, thereby
The communication between the hydraulic pump 35 and the suction port 3b of the hydraulic pump 3 is interrupted, and the return of the pump discharge fluid through the return passage 36 connecting them 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 is cut off, and the connection portion 35 and the suction port 3b of the hydraulic pump 3
The connection is made through a return passage 36.

In this state, when the hydraulic pump 3 rotates at a predetermined low-speed rotation speed Na 'which is lower than a predetermined low-speed rotation speed Na (substantially idling rotation speed), the pressure oil generated by the hydraulic pump 3 Flows into the first valve chamber 10 of the spool housing hole 5 through the discharge passage 6, and the pressure oil in the first valve chamber 10 passes through the fixed throttle passage 14 having the fixed orifice 13 and is connected to the connection portion 35. Flows into. Then, the pressure P ₄ of the pressure oil in the connection portion 35 still causes the sub-spool valve body 41 to
Since the suction port 44 and the discharge port 45 communicate with each other in a downward direction against the spring force of 46, a part of the pressure oil in the connection portion 35 passes through the return passage 36. To the suction port 3b of the hydraulic pump 3 via the
Only the remaining portion of the pressure oil inside is supplied to the power steering device via the pressure oil supply pipe 32. During this time, the pressure P ₂ of the pressurized oil in the first valve chamber 10 and the pressure P ₃ of the pressurized oil in the second valve chamber 11 (when the pressure oil does not flow in the communication passage 34, most equal pressure oil pressure P ₄ of the 35.) and the pressure difference is small between, not enough to move to the left the flow regulating spool 4 against the spring force of the spring 12, thus, the discharge Since the passage 6 and the bypass passage 7 remain shut off, the entire amount of the pressure oil generated by the hydraulic pump 3 flows from the first valve chamber 10 through the fixed throttle passage 14 into the connection portion 35 (FIG. 3).

As a result, the amount of the remaining pressure oil in the connection portion 35 supplied to the power steering device via the pressure oil supply pipe 32 is as follows:
As shown by 0-a 'in FIG. 7, the value increases in proportion to the increase in the rotation speed of the hydraulic pump 3.

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. Therefore, the sub-spool valve element 41 maintains the initial state, the suction port 44 and the discharge port 45 communicate with each other, and a part of the pressure oil in the connection portion 35 is supplied to the hydraulic pump 3 through the return passage 36. Only the remaining pressure oil in the connection portion 35 is returned to the suction port 3b and 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 valve chamber 11
Since the pressure difference from the pressure P ₃ of the internal pressure oil increases rapidly,
The flow rate adjusting spool 4 moves to the left against the spring force of the spring 12, and connects the discharge passage 6 and the bypass passage 7 (see FIG. 4).

As a result, a part of the pressure oil generated in the hydraulic pump 3 is returned to the suction port 3b of the hydraulic pump 3 through the bypass passage 7, and only the remaining part flows from the first valve chamber 10 through the fixed throttle passage 14 to the fixed throttle passage 14. Then, it flows into the connection part 35. Here, the amount returned to the suction port 3b of the hydraulic pump 3 through the bypass passage 7 increases in proportion to the increase in the rotation speed of the hydraulic pump 3, so that the pressure oil flowing into the connection portion 35 The amount is substantially constant irrespective of the increase in the rotation speed of the hydraulic pump 3. Then, a part of the pressure oil in the connection portion 35 having a substantially constant inflow is returned to the suction port 3b of the hydraulic pump 3 through the return passage 36 as described above, and only the remaining portion is supplied to the pressure oil supply pipe 32. Through the power steering device. For this reason, the remaining amount of the pressure oil supplied to the power steering device is maintained at a substantially constant low level regardless of the increase in the rotation speed of the hydraulic pump 3 as shown by a′-d in FIG. Will be maintained.

On the other hand, in a situation in which 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 a 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 and moves rightward, again interrupting the communication between the discharge passage 6 and the bypass passage 7. 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 element 41 downward against the spring force of the spring 46, the sub-spool valve body 41, the communication passage 38 into the connecting 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,
The communication between the discharge passage 6 and the bypass passage 7 is blocked (FIG. 5).
reference).

As a result, the pressure oil generated by the hydraulic pump 3 flows from the first valve chamber 10 through the fixed throttle passage 14 into the connection portion 35, and the entire amount of the oil flows therefrom via the pressure oil supply pipe 32. The oil is supplied to the steering device, and the amount of supplied oil is controlled by the hydraulic pump 3 as shown by a'-a in FIG.
Increases substantially in proportion to the increase in the number of revolutions.

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
(See FIG. 6).

As a result, the increase in the pressure oil generated in the hydraulic pump 3 is returned to the suction port 3b of the hydraulic pump 3 through the bypass passage 7, and the amount thereof is proportional to the increase in the rotation speed of the hydraulic pump 3. The first valve chamber 10, fixed throttle passage
14, the amount of pressure oil supplied to the power steering device via the connection portion 35 and the pressure oil supply pipe 32 depends on the further increase in the rotation speed of the hydraulic pump 3, as shown in ae of FIG. And maintained at an almost constant high level.

Assuming that 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 the 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 rotational speed of the hydraulic pump 3 is higher than the rotational speed near the high-speed rotational speed Nc and is in the 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 upstream end of the return passage 36 (the upstream end of the communication passage 38) communicates with the connecting portion 35, and the control hydraulic chamber 42, which is one of the chambers in the sub-spool housing hole 40, is connected. The communication with the connecting portion 35 through the communication passage 47 and the communication passage 38 is not limited to this, but any communication may be used as long as it is connected to 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, since the pressure of the pressure oil introduced into the control hydraulic chamber 42 directly reflects the power assist 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 pressure of the pressure oil is performed by controlling the pressure in the first valve chamber 10 upstream of the fixed orifice 13, for example, in the spool housing hole 5. It is more accurate than the same control by the load sensing valve 37 operated by the oil pressure.

In the present embodiment, the return passage 36
Is connected to the suction port 3b of the hydraulic pump 3 at the downstream end of the bypass passage 7, but if it is in the bypass passage 7, its position can be selected as appropriate. .

[Brief description of the drawings]

FIG. 1 is a view for explaining the overall configuration of a load-sensitive flow control device for a power steering device according to an embodiment of the present invention described in claims 1 and 2; 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. A load-sensitive flow control device for a power steering device, wherein a surplus pressure fluid is returned to a suction side of a pump by a flow control spool valve for adjusting an opening degree of a bypass passage; a fixed throttle passage in the supply passage; A load sensing valve is provided in a return passage connecting the more downstream side 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-sensitive flow control device for a power steering device, characterized in that the flow control device is configured as described above. 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 supply passage is communicated to the downstream side of the fixed throttle passage, and 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. The load-responsive flow control device for a power steering device according to claim 1, wherein