JP3793318B2 - Hydraulic power steering device flow control valve - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a hydraulic power steering apparatus provided with a flow control valve.
[0002]
[Prior art]
Conventionally, the present applicant has filed Japanese Patent Application No. 7-115052 as a hydraulic power steering apparatus provided with this type of flow control valve.
[0003]
FIG. 6 (A) shows a pump in which the pump flow control valve FV according to the application is assembled into one body. Here, a vane pump VP is used as a pump.
In the vane pump VP, a shaft hole 12 is formed in a housing H including a pump body 10 and a cover 11, and a shaft 14 is rotatably supported by a bearing 13 provided in the shaft hole 12. The shaft 14 serves as a drive shaft for a rotor 15 provided in the pump body 10, and a plurality of vanes 16 are radially incorporated in the rotor 15.
[0004]
Further, a cam ring 17 having an elliptical inner wall is provided around the rotor 15 as shown in FIG. 6B, which is a view taken along the line XX in FIG. When the shaft 14 is driven, the rotor 15 also rotates. At this time, the vane 16 comes out and enters along the inner wall of the cam ring 17. In other words, the vanes 16 rotate while the tips of the vanes 16 are in close contact with the cam ring 17, and each of the vanes 16 forms an independent chamber.
[0005]
When each chamber enters the contraction stroke, the hydraulic oil is discharged from the discharge port, and when each chamber enters the expansion stroke, the hydraulic oil is sucked.
A side plate 18 is provided on the side surfaces of the rotor 15 and the cam ring 17. A high pressure chamber 19 is formed on the back side of the side plate 18, and pump discharge pressure is guided to the high pressure chamber 19. The side plate 18 is pressed against the rotor 15 by the pressure of the hydraulic oil in the high-pressure chamber 19 to maintain the loading balance.
Further, the pump body 10 is integrally provided with a pump flow control valve FV. That is, the pump body of the pump flow control valve FV is shared with the pump body 10 of the vane pump VP.
[0006]
Next, the operation of this power steering apparatus will be described. The shaft 14 of the vane pump VP is connected to an engine (not shown). When the engine is started, the rotor 15 connected to the shaft 14 rotates. Accordingly, the discharge amount of the vane pump VP increases as the engine speed increases. The discharged hydraulic oil is guided to the pressure chamber 8a of the flow control valve FV shown in FIG. 4A and is supplied from the actuator port 20a to the power steering circuit PS.
[0007]
At this time, a pressure difference is generated before and after the variable throttle 3 shown in FIG. The upstream pressure acts on the left end surface of the spool 7 on the pressure chamber 8 a side, while the downstream pressure acts on the right end surface of the spool 7 on the pilot chamber 8 b side via the pilot passage 29.
[0008]
However, the spool 7 may move to the right until the thrust obtained by multiplying the differential pressure across the variable throttle 3 by the pressure receiving area of the spool 7 exceeds the initial load of the spring 9, that is, until a certain pump discharge amount is reached. The pump port 4 and the drain port 5 are kept shut off. Therefore, all the pump discharge amount is supplied to the power steering circuit PS (section a of the characteristic line K in FIG. 3C).
[0009]
When the engine speed increases, the pump discharge amount increases, and the differential pressure across the variable throttle 3 exceeds a certain level, the spool 7 moves to the right against the spring 9. The spool 7 stops at a position where the thrust acting on the spool 7 and the spring force of the spring 9 are balanced, and the pump port 4 and the drain port 5 are communicated with each other at an opening degree corresponding to this position.
[0010]
According to the pump flow control valve FV, the supply amount Q to the power steering circuit PS decreases as the engine speed increases. This is for the following reason. That is, as the pump discharge amount increases, the differential pressure across the variable throttle 3 increases, so that the spool 7 moves further to the right. If the spool 7 moves in this way, the large diameter portion 23a of the throttle member 23 enters the throttle hole 22b, so that the opening of the variable throttle 3 is further reduced. In addition, when a part of the large-diameter portion 23a enters the throttle hole 22b and when all of the large-diameter portion 23a enters the throttle hole 22b, the throttling effect is different. The more you enter, the greater the pressure difference across it.
[0011]
In this way, as indicated by the section b of the characteristic line K in FIG. 3C, when the engine speed N becomes higher than a predetermined value, the flow rate supplied to the power steering circuit PS decreases, and the power assist is reduced. Reduce power. Moreover, since the engine speed N is proportional to the vehicle speed, a power assist force corresponding to the vehicle speed can be applied after all. The maximum supply amount Qm may be set based on the maximum required power assist force.
[0012]
The maximum pressure supplied to the power steering circuit PS is determined by a relief valve. That is, when the load pressure of the power steering circuit PS rises abnormally, the pressure in the first pilot chamber 8 b increases and this pressure acts on the ball poppet 33. When this pressure becomes higher than the relief set pressure determined by the spring 32, the ball poppet 33 is pushed open to connect the first pilot chamber 8b and the drain port 5.
[0013]
When the pilot chamber 8b and the drain port 5 communicate with each other as described above, a flow is generated in the pressure sensing hole 24, and a pressure loss is generated there. As a result, the pressure in the pilot chamber 8b rapidly decreases, and the spool 7 moves to the right as shown in FIG. 5 to increase the opening degree of the pump port 4 and the drain port 5, thereby lowering the pump supply pressure. . When the circuit pressure of the power steering circuit PS becomes smaller than the relief set pressure, the ball poppet 33 is seated again on the seat surface 34, so that the maximum pressure of the power steering circuit PS can be regulated.
[0014]
The conventional example shown in FIGS. 4 and 5 is characterized in that a piston 35 is provided facing the spool 7 and a switching spool 36 is provided in the piston 35.
3B is a circuit diagram, FIG. 4A and FIG. 4B, which is a partially enlarged view thereof, show a state where the vane pump VP is stopped, and FIG. FIG. 5B, which is an enlarged view, shows a steering state in which the vane pump VP is driven. In the conventional example, the pump flow rate control valve FV is configured such that the spool 7 and the piston 35 are opposed to each other in the first pilot chamber 8b connected to the downstream side of the variable throttle 3 through the passage 29, and a spring is interposed between the two. 9 is interposed.
[0015]
The piston 35 is formed with a flange portion 37 at the center thereof, and the flange portion 37 defines a second pilot chamber 38 and a drain chamber 39. A stop step portion 39a is formed in the drain chamber 39 so that the collar portion 37 cannot move any more in contact with the stop step portion 39a.
The second pilot chamber 38 is provided on the opposite side of the first pilot chamber 8b across the piston 35. Further, the drain chamber 39 is communicated with a tank passage (not shown) and the communication with the first pilot chamber 8b is blocked. Then, the pressure receiving area of the other pressure receiving surface 35b (including the pressure receiving surface of the flange 37) facing the second pilot chamber is made larger than the one pressure receiving surface 35a of the piston facing the first pilot chamber 8b side. ing.
[0016]
The piston 35 has a spool hole 40 formed on the axis thereof, and the left end of the spool hole 40 is opened and the right end is closed on the first pilot chamber 8b side. The switching spool 36 is slidably incorporated in the spool hole 40 thus configured. Therefore, the pressure of the first pilot chamber 8 b acts on the left end surface of the switching spool 36.
[0017]
Further, an annular groove 41 is formed in the piston 35, and the annular groove 41 and the second pilot chamber 38 are communicated with each other through a through hole 42.
The switching spool 36 is formed with two land portions 43 and 44 as shown in FIG. 4B and an annular recess 45 between the land portions 43 and 44. The spring force of the spring 46 is applied to the right land portion 44 side of the switching spool 36.
[0018]
The annular recess 45 always communicates with the drain chamber 39 via the passage 47 regardless of the movement position. Further, a communication hole 48 is formed in the switching spool 36, and the chamber containing the spring 46 is communicated with the drain chamber 39 via the annular recess 45. In the normal position shown in FIG. 4A, the switching spool 36 configured as described above shuts off the communication between the first pilot chamber 8b and the annular groove 41 at the land portion 43, while the second pilot chamber 38 is The drain chamber 39 communicates with the annular recess 45 and the passage 47.
[0019]
When the vane pump VP is driven, the pressure oil is guided to the pressure chamber 8 a via the pump port 4 and also to the power steering circuit PS via the variable throttle 3. When the vehicle is not steered, the power steering circuit PS is in a neutral state, and the pressure oil is returned to the tank. Therefore, the load pressure of the power steering circuit PS, in other words, the pressure downstream of the variable throttle 3 is low, and the spring 46 The set pressure set in is not exceeded. Therefore, the piston 35 maintains the normal position of FIG. 4A, and the load of the spring 9 in the first pilot chamber 8b is kept small.
[0020]
As a result, the thrust obtained by multiplying the pressure difference between the pressure chamber 8a and the first pilot chamber 8b by the pressure receiving area of the spool 7 overcomes the spring force of the spring 9 in the first pilot chamber 8b. Move to the right until balanced. If the spool 7 moves, the pump port 4 communicates with the drain port 5, so that the supply flow rate to the power steering circuit PS is reduced accordingly.
FIG. 3C shows the supply flow rate at the time of non-steering compared with that at the time of steering, and shows that the supply flow rate Qn at the time of non-steering is smaller than the maximum supply flow rate Qm at the time of steering.
[0021]
In the steering state, when the pressure in the first pilot chamber 8b exceeds the set pressure determined by the spring 46, the switching spool 36 moves to the right against the spring 46, and the first pilot chamber 8b, the annular groove 41, To communicate. Since the annular groove 41 communicates with the second pilot chamber 38 via the through hole 42, the first pilot chamber 8 b and the second pilot chamber 38 communicate with each other. Accordingly, the downstream pressure of the variable throttle 3 is guided to each of the first pilot chamber 8b and the second pilot chamber 38, and the piston 35 springs due to the area difference between the left pressure receiving surface 35a and the right pressure receiving surface 35b of the piston 35. Move to the left against 9 The maximum amount of movement of the piston 35 at this time is until it comes into contact with the stop step portion 39a.
[0022]
If the piston 35 moves in this way, the load of the spring 9 increases. If the load increases, the amount of movement of the spool 7 until the thrust based on the pressure difference between the pressure chamber 8a and the first pilot chamber 8b balances with the load of the spring 9 also becomes relatively small. Outflow to port 5 is reduced. As a result, the supply flow rate to the power steering circuit PS increases, and the flow rate characteristic of the characteristic line K shown in FIG.
[0023]
As is apparent from the above, according to this embodiment, the maximum supply flow rate Qm is ensured during steering so that the power steering circuit PS side does not run out of power, while the supply flow rate Qn of the vane pump VP is not used during non-steering. Is less than the maximum supply flow rate Qm during steering, so that energy loss during non-steering can be reduced.
[0024]
[Problems to be solved by the invention]
In the case of the above prior art, the opening area of the variable throttle 3 is such that the throttle hole 22b fixed to the pump body 10 via the connector 20 and the fitting position of the throttle member 23 fixed to the left end of the spool 7 as a whole. That is, the area is determined by the large diameter portion 23 a or the small diameter portion 23 b, and is an area uniquely determined by the balance position of the spool 7.
[0025]
Consider a case in which the pressure on the power steering circuit PS side changes corresponding to the power assist force in this state. If the characteristic of K in FIG. 3C is selected when the pressure on the power steering circuit PS side is an average load pressure Pm, when the pressure on the PS side becomes Pu higher than Pm, the first pilot chamber 8b As the pressure increases, the spool 7 moves to the left from the state shown in FIG. As a result, the opening area of the drain port 5 decreases, the pressure Pp of the pump port 4 increases, and at the left end of the spool 7 one Since the fitting length between the large-diameter portion 23a of the throttle member 23 fixed physically and the throttle hole 22b is shortened, the passage resistance of the variable throttle 3 is reduced, as indicated by Ku in FIG. The supply flow rate to the PS side increases.
[0026]
On the other hand, when the pressure on the power steering circuit PS side becomes Pd lower than the average load pressure Pm, the pressure in the first pilot chamber 8b decreases, and the spool 7 moves to the right from the state shown in FIG. As a result, the opening area of the drain port 5 increases, the pressure Pp of the pump port 4 decreases, and at the left end of the spool 7 one Since the fitting length between the large-diameter portion 23a of the throttle member 23 fixed physically and the throttle hole 22b becomes longer, the passage resistance of the variable throttle 3 increases, as indicated by Kd in FIG. The supply flow rate to the PS side decreases. Since this phenomenon affects the steering feeling of the power steering apparatus, even if the pressure on the power steering circuit PS side fluctuates, the supply flow rate characteristic to the power steering circuit PS side does not fluctuate with respect to the preset engine speed. There is a persistent demand for it.
[0027]
The present invention has been made in view of the circumstances as described above. The purpose of the present invention is to supply a sufficient flow rate to the power steering circuit PS side even in a region where the engine speed is low at the time of steering. Even if the pressure on the steering circuit PS side fluctuates, the supply flow rate characteristic to the power steering circuit PS side with respect to a preset engine speed is prevented from fluctuating.
[0028]
[Means for Solving the Problems]
The means taken by the present invention to solve the above problem is that the flow control valve for power steering is urged to the pump port side by a large-diameter spring with a large set load housed on the power steering circuit side. The plunger is slidably incorporated in the body and is similarly urged toward the pump port by a small-diameter spring with a small set load housed inside the large-diameter spring on the power steering circuit side, and is screwed into the pump body. It consists of a rod that is slidably mounted on a support that is fixed to the connector. Against the pressing force of the small diameter spring On the other hand, in the region where the engine speed is high, the plunger further Against the pressing force of the large-diameter spring Acting to control the opening area of the annular passage formed by engagement with a rod having a step difference in diameter from the inner diameter of the plunger.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Next, portions of the embodiment of the present invention that are different from the conventional example will be described. FIG. 1 shows a non-steering state when the engine speed is low and the discharge amount of the vane pump VP is small. The illustrated switching spool 106 is provided with apertures 106A and 106B. When the throttle 106A is switched from the non-steering state to the steering state, the pressure in the first pilot chamber 101A increases as the load pressure of the power steering circuit increases, and the switching spool 106 resists the spring force of the spring 105. Moving upward, the passage area when the first pilot chamber 101A and the second pilot chamber 101B communicate with each other via the annular groove 102B and the through hole 102C is limited. As a result, the piston 102 slowly moves downward, so that the change in the supply pressure to the power steering circuit PS, in other words, the change in the power assist force also becomes gradual, thereby preventing the driver from feeling uncomfortable.
[0030]
Similarly, when the throttle 106B is switched from the steering state to the non-steering state, the pressure in the first pilot chamber 101A decreases, and the switching spool 106 moves downward by the spring force of the spring 105, as shown in FIG. Further, by restricting the passage area when the second pilot chamber 101B communicates with the drain chamber 101C, a rapid change in the power assist force is prevented. The apertures 106A and 106B can be easily formed by drilling with a drill or the like at right angles to the axis of the switching spool 106, and the above effects can be obtained at a low processing cost.
[0031]
The piston case 101 threadedly engaged with the pump body 100 guides the piston 102 to the central portion thereof in a slidable manner, and the piston 102 partitions the second pilot chamber 101B and the drain chamber 101C. A stop step portion 101D is formed in the drain chamber 101C so that the piston 102 cannot move further downward after contacting the stop step portion 101D.
[0032]
The second pilot chamber 101B is provided on the opposite side of the first pilot chamber 101A across the piston 102 by inserting a stopper 103 with a seal attached to the upper end of the piston case 101 and preventing it from being removed by the C pin 104. ing. The drain chamber 101C communicates with a tank passage (not shown) via the communication passage 101F and the volume chamber 100G, and communication with the first pilot chamber 101A is blocked by a seal 109. Then, the pressure receiving area of the upper pressure receiving surface 102E facing the second pilot chamber 101B and including the pressure receiving area 102F of the upper end of the piston is made larger than the pressure receiving surface 102D below the piston 102 facing the first pilot chamber 101A side. ing.
[0033]
When the vane pump VP is driven, the pressure oil is guided to the pressure chamber 100A via the pump port 4 and also to the power steering circuit PS side via the power steering flow control valve FCV. In the non-steering state shown in FIG. 1, since the power steering device is in a neutral state, the load pressure on the power steering circuit PS side, in other words, the pressure on the downstream side of the power steering flow control valve FCV is It is guided to the first pilot chamber 101A side through the pilot passage 100C. Since this pressure is low, the set pressure determined by the spring 105 is not exceeded. Therefore, the piston 102 maintains the normal position shown in FIG. 1, and the set load of the spring 108 in the first pilot chamber 101A is reduced.
[0034]
In this state, the upward thrust obtained by multiplying the pressure difference between the pressure chamber 100A and the first pilot chamber 101A by the pressure receiving area of the spool 107 slidably incorporated in the pump body 100 is added to the spring force of the spring 108. It overcomes and moves upward until the spool 107 balances the load of the spring 108. If the spool 107 moves upward in this way, the pump port 4 communicates with the drain port 5, and accordingly, the burden on the pump is reduced.
[0035]
In the non-steering state described above, since the pressure on the power steering circuit PS side is low, the piston 102 maintains the normal position shown in FIG. 1, and the set load of the spring 108 in the first pilot chamber 101A is small. Inner diameter side small diameter portion of plunger 115 slidably incorporated in body 122 Orifice 115A The differential pressure before and after the annular gap W formed by the engagement gap of the large-diameter portion 116B of the rod 116 is smaller than that during steering. As a result, the plunger 115 maintains the state of FIG. 1 pushed up by the large diameter spring 119.
[0036]
Similarly, in the non-steering state, the rod 116 slidably incorporated in the support 112 secured to the connector 121 is pushed upward by the small-diameter spring 118 via the E-ring 117 fitted to the rod, and The portion 116C is kept in the state of FIG. Accordingly, the annular gap W has a small area. Here, the washer 120 is interposed in order to evenly transmit the load of the small-diameter spring 118 to the E-ring 117. In the non-steering state, since the pressure on the power steering circuit PS side is low, the pressure difference before and after the annular clearance W of the power steering flow control valve FCV is kept substantially constant, so the supply flow rate Qo is as shown in FIG. As indicated by the broken line in (A), the energy loss can be reduced because the flow rate is maintained at a substantially constant low flow rate independent of the pump rotation speed.
[0037]
In the steering state shown in FIG. 2, the load pressure of the power steering circuit PS increases, but the increased pressure Pu is supplied to the first pilot of the pump flow control valve FV via the pilot passages 100B, 100C, 100D. It is also led to the chamber 101A. Therefore, the thrust obtained by multiplying the pressure in the first pilot chamber 101A by the pressure receiving area of the switching spool 106 overcomes the load of the set spring 105, the switching spool 106 moves upward, and the throttle 106A opens into the annular groove 102B. The first pilot chamber 101A and the second pilot chamber 101B communicate with each other through the aperture 106A.
[0038]
As a result, the piston 102 moves in the direction in which the spring 108 is contracted due to the pressure receiving area difference between the pressure receiving surfaces 102D and 102E, but the moving speed is moderated by the restrictor 106A. Even if the pressure in the first pilot chamber 101A pulsates, the pressure in the second pilot chamber 101B is buffered by the restrictor 106A and the pulsation is not transmitted as it is, so that the piston 102 can be prevented from vibrating in the axial direction. it can. The maximum amount of movement at this time is until the piston 102 contacts the stop step portion 101D.
[0039]
When the piston 102 moves, the load of the spring 108 increases. When the load increases, the stroke in which the spool 107 moves upward due to the pressure action in the pressure chamber 101A is also relatively reduced, the flow rate flowing out from the pump port 4 to the drain port 5 is reduced, and the pump port 4 The pressure Pp also increases.
[0040]
At the time of steering, since the pressure on the PS side is high, the piston 102 is pushed down as shown in FIG. 2, and the set load of the spring 108 in the first pilot chamber 101A becomes large. 115 The differential pressure before and after the annular gap W formed by the engagement gap between the inner diameter side orifice 115A and the rod 116 increases as compared with the non-steering state. As a result, the rod 116 moves downward by pressing the small-diameter spring 118 having a small set load through the E-ring 117 fitted to the rod itself. As the flange portion 116C moves away from the support 112, the small diameter portion on the plunger inner diameter side and the small diameter portion 116A of the rod engage with each other, and thus the annular clearance W formed by the engagement clearance has a large area.
[0041]
Therefore, the thrust Ap (Pp-Pu) obtained by multiplying the pressure receiving area Ap of the plunger 115 by the differential pressure (Pp-Pu) between the pressure Pp of the pump port and the pressure Pu on the power steering circuit PS side is obtained from the set load of the large-diameter spring 119. Since the plunger 115 does not operate in a small pump rotation speed region, the supply flow rate to the PS side increases up to the maximum supply flow rate Qs as shown by the solid line in FIG. 3A, and the power steering circuit PS side does not run out of power. Like that.
[0042]
When the engine speed increases and enters the region b in FIG. 3A, the differential pressure across the annular gap W increases, so that the rod 116 moves downward until the small-diameter spring 118 reaches the maximum compression state. . When the differential pressure across the annular gap W is further increased, the plunger 115 having a larger pressure receiving area than the rod 116 overcomes the set load of the large-diameter spring 119 and moves downward, and the large diameter of the rod 116 which is in the most compressed state It gradually engages with the portion 116B. As a result, since the opening area of the annular gap W is gradually reduced, the supply flow rate to the power steering circuit PS is also gradually reduced as shown by the supply flow rate characteristic J indicated by the solid line in FIG.
[0043]
As is apparent from the above, according to this embodiment, in the region where the engine speed during steering is low, the rod 116 first pushes the small-diameter spring 118 and moves downward to reduce the opening area of the annular gap W. By increasing the value, the maximum supply flow rate Qs is secured, so that the power steering circuit PS does not run out of power. When the engine speed increases and the differential pressure across the annular gap W increases, the plunger 115 overcomes the set load of the large-diameter spring 119 and moves downward, and the opening area of the annular gap W gradually decreases. The supply flow rate to the circuit PS side is reduced, and energy loss can be reduced.
[0044]
On the other hand, at the time of non-steering, the pump supply flow rate Qo is made smaller than the maximum supply flow rate Qs at the time of steering regardless of the engine speed, so that energy loss can be reduced. Moreover, since the power steering flow control valve FCV is separated from the pump flow control valve FV and is a pressure compensation type, even if the pressure on the power steering circuit PS side fluctuates, a predetermined engine speed is set. Since the supply flow rate characteristic J to the power steering circuit PS with respect to the number does not fluctuate, a good steering feeling can be maintained.
[0045]
【The invention's effect】
According to the present invention, in a region where the engine speed during steering is low, the rod 116 of the power steering flow control valve FCV first pushes the small-diameter spring 118 and moves downward to increase the opening area of the annular gap W. Thus, the maximum supply flow rate Qs is ensured so that the power steering circuit PS side does not run out of power. When the engine speed increases and the differential pressure across the annular gap W increases, the plunger 115 overcomes the set load of the large-diameter spring 119 and moves downward, and the opening area of the annular gap W gradually decreases. The supply flow rate to the circuit PS side is reduced, and energy loss can be reduced.
On the other hand, at the time of non-steering, the supply flow rate Qo is made smaller than the maximum supply flow rate Qs at the time of steering regardless of the engine speed, so that energy loss can be reduced. Moreover, since the power steering flow control valve FCV is separated from the pump flow control valve FV and is a pressure compensation type, even if the pressure on the power steering circuit PS side fluctuates, a preset engine is set. Since the supply flow rate characteristic J to the power steering circuit PS with respect to the number of rotations does not fluctuate, a good steering feeling can be maintained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a non-steering state of a flow control valve of a power steering device of the present invention.
FIG. 2 is a cross-sectional view showing a steering state of a flow control valve of the power steering device of the present invention.
FIG. 3A is a graph showing supply flow rate characteristics of a power steering apparatus according to the present invention.
(B) It is a circuit diagram of the power steering device which concerns on a prior art.
(C) It is a graph which shows the supply flow volume characteristic of the power steering apparatus which concerns on a prior art.
FIG. 4A is a cross-sectional view of a flow control valve according to the prior art when stopped.
(B) It is an expanded sectional view of the piston part of the above-mentioned flow control valve.
FIG. 5A is a cross-sectional view during steering of a flow control valve according to the prior art.
(B) It is an expanded sectional view of the piston part of the above-mentioned flow control valve.
FIG. 6A is a cross-sectional view of a vane pump.
(B) It is an XX line end view of the vane pump.
[Explanation of symbols]
Flow control valve for FV pump
PS power steering circuit
PV vane pump
Flow control valve for FCV power steering
1 pump
2 Channel
4 Pump port
5 Drain port
100 pump body
100A pressure chamber
101A 1st pilot room
101B 2nd pilot room
107 spool
108 spring
112 Support
115 Plunger
116 Rod
118 Small diameter spring
119 Large diameter spring
121 connector
122 Valve body

Claims (1)

A hydraulic power steering device that includes a power steering flow control valve provided in the middle of a flow path connecting a pump whose discharge amount changes in accordance with the engine speed to a power steering circuit, and that controls the return flow rate from the pump to the tank. In the flow control valve for pump ,
The pump flow control valve includes a pump body, a pressure chamber in which pressure oil from the pump is guided through a pump port , connected to the upstream side of the power steering flow control valve, a drain port communicating with the tank, a spool incorporating slidably on the pump body and the a first pilot chamber which is provided on the opposite side of the pressure chamber across the spool, by the action of the spring force to the spool provided in the first pilot chamber spring And a piston case screwed into the pump body, and a piston slidably disposed in the piston case to vary the set load of the spring, and the pressure on the upstream side of the pump flow control valve a pressure chamber, also leads to pressure on the downstream side in the first pilot chamber through the pilot passage, the pressure difference before and after the power steering flow control valve is given When the pressure exceeds the force, the pressure in the pressure chamber overcomes the spring force of the spring and the pressure action of the first pilot chamber to move the spool and open the pressure chamber to the drain port with an opening according to the position of the spool. the configuration in which,
The flow control valve for power steering is urged to the pump port side by a large-diameter spring with a large set load housed on the power steering circuit side, and similarly to a plunger slidably incorporated in the valve body. It is biased to the pump port side by a small diameter spring of the circuit-side set load that is housed inside the large diameter spring, a rod incorporated in slidably support which is anchored to the connector to be screwed to the pump body In the region where the engine speed is low, the rod first operates against the pressing force of the small-diameter spring, while in the region where the engine speed is high, the plunger further operates against the pressing force of the large-diameter spring. Formed by engagement with a rod having a step difference in diameter from the inner diameter of the plunger. Pump flow control valve of the hydraulic power steering apparatus characterized by controlling the opening area of the annular passage that.

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