JP2007099037A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device capable of avoiding contaminants from being sucked in a reversible pump again, and efficiently removing the contaminants in working oil. <P>SOLUTION: This device comprises a filter provided to a reservoir tank, and filtering a working oil. First and second bi-direction valves are controlled to be opened or closed by a forward and backward differential pressure. Under a first condition that a pressure on the pump side is higher than the pressure on the power cylinder side, a reversible pump side and a power cylinder side of a first passage are communicated with each other. Under a second condition that the pressure on the pump side is smaller than the pressure on the power cylinder side, the reversible pump side and the power cylinder side of the first passage are shielded, and the first path and the reservoir tank on the power cylinder side are communicated with each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power steering device that assists steering force.

Conventionally, in a power steering apparatus as disclosed in Patent Document 1, steering assist is provided by selectively supplying hydraulic pressure from a reversible pump driven by an electric motor to left and right cylinder chambers of a power cylinder, respectively. Gaining power. While the hydraulic pressure discharged from the reversible pump is supplied to the power cylinder, it acts on a bidirectional valve provided in the middle of the piping. The bi-directional valve switches the communication between the left and right passages connecting the reversible pump and the power cylinder to the reservoir tank and shuts off the reservoir tank. When the hydraulic pressure from the reversible pump is applied, the passage and the reservoir are switched. While shutting off the tank, the opposite bidirectional valve is opened. Therefore, the passage on the side where the hydraulic pressure from the reversible pump is not supplied communicates with the reservoir tank, and hydraulic oil from the power cylinder is discharged to the reservoir tank.
JP 2003-137117 A

  However, in the above prior art, when a reversible pump is provided with a filter in a passage for sucking hydraulic oil from the reservoir tank to remove contamination in the piping, for example, the hydraulic oil discharged from the left cylinder chamber Part of the oil is discharged to the reservoir tank, but the remaining hydraulic oil is sucked into the reversible pump and supplied again to the right cylinder chamber, so there is a risk that contamination in the piping cannot be removed sufficiently. There was a problem that there was.

  The present invention has been made paying attention to the above-mentioned problem, and the purpose thereof is to prevent the contamination from being sucked into the reversible pump again and to efficiently remove the contamination in the hydraulic oil. The object is to provide a steering device.

  In order to achieve the above-described object, in the present invention, a hydraulic power cylinder for assisting a steering force of a steering mechanism coupled to a steering wheel, and both pressure chambers of the hydraulic power cylinder via first and second passages. A reversible pump having a pair of discharge ports for supplying hydraulic pressure, an electric motor for rotating the reversible pump forward and backward, steering assist force detecting means for detecting a steering assist force to be applied to the steered wheels, and the steering Based on the steering assist force detected by the assist force detection means, motor control means for outputting a drive signal to the electric motor in order to generate a desired hydraulic pressure in the electric motor, and a first passage provided in the first passage A bidirectional valve, a second bidirectional valve provided in the second passage, a reservoir tank for storing hydraulic oil, and a filter provided in the reservoir tank for filtering the hydraulic oil And the first passage between the reversible pump and the first bidirectional valve, and is provided between the first passage and the reservoir tank, and flows from the reservoir tank to the first passage. A first one-way valve that allows only the first passage, and the second passage between the reversible pump and the second bidirectional valve, and is provided between the second passage and the reservoir tank. A second one-way valve that allows only flow from the tank to the second passage, and the first bidirectional valve is controlled to open and close by a differential pressure across the first bidirectional valve, and at least the reversible pump In a first state where the pressure on the side is higher than the pressure on the power cylinder side, the reversible pump side and the power cylinder side of the first passage communicate with each other, and at least the pressure on the reversible pump side In the second state smaller than the pressure on the power cylinder side, the reversible pump side and the power cylinder side of the first passage are shut off, and the first passage on the power cylinder side and the reservoir tank are In the first state, the second bidirectional valve is controlled to open and close by the differential pressure across the second bidirectional valve, and at least the pressure on the reversible pump side is higher than the pressure on the power cylinder side. The reversible pump side of the second passage communicates with the power cylinder side, and at least in the second state where the pressure on the reversible pump side is smaller than the pressure on the power cylinder side, The reversible pump side and the power cylinder side are shut off, and the second passage on the power cylinder side and the reservoir tank are connected. I decided to let it pass.

  Therefore, it is possible to provide a power steering device that avoids contamination from being sucked into the reversible pump again and can efficiently remove contamination in the hydraulic oil.

  Hereinafter, the best mode for realizing the power steering apparatus of the present invention will be described based on an embodiment shown in the drawings.

[System configuration of power steering system]
Example 1 will be described with reference to FIGS. FIG. 1 is a system configuration diagram of the power steering apparatus of the present application. The direction of the rack shaft 4 is defined as the x-axis, and the first passage 21 side is defined as the positive direction.

(System configuration)
When the driver steers the steering wheel 1, the pinion 3 is driven through the shaft 2, and the rack shaft 4 is moved in the axial direction by a so-called rack and pinion mechanism to steer the front wheels. The shaft 2 is provided with a torque sensor 5 (steering assist force detecting means) and outputs a torque signal to the control unit 8 (electric motor control means).

  The rack shaft 4 is provided with a power steering mechanism that assists the movement of the rack shaft 4 according to the steering torque of the driver. The power steering mechanism includes a motor M (electric motor), a bidirectional pump P (reversible pump), and a power cylinder 6.

  The power cylinder 6 is defined in a first cylinder chamber 61 and a second cylinder chamber 62 by a piston 63 provided so as to be movable in the axial direction, and the first and second cylinder chambers 61, 62 are in the first and second passages 21. , 22 to connect to the pump P. The motor M is driven based on a command from the control unit 8, the pump P is rotated forward / reversely to supply hydraulic oil to the first and second cylinder chambers 61, 62, and the rack shaft 4 is moved in the axial direction to be steered. Generate assist force.

(Hydraulic circuit)
The first and second passages 21 and 22 are connected to the reservoir tank 7 via the first and second supply oil passages 28 and 29, and hydraulic oil is supplied by driving the pump. The first and second passages 21 and 22 are provided with first and second bidirectional valves 100 and 200, respectively.

  The first and second bidirectional valves 100 and 200 are valves that are mechanically opened / closed by a pressure difference between the first and second passages 21 and 22, and of the first and second passages 21 and 22, The downstream side of the low-pressure side passage communicates with the reservoir tank 7 via the reservoir tank communication passage 27.

  That is, the first and second bidirectional valves 100 and 200 allow the low-pressure side and the reservoir tank 7 to communicate with each other on the downstream sides 21 b and 22 b of the first and second passages 21 and 22. On the other hand, if the first and second passages 21 and 22 are at equal pressure, the upper / downstream 21a and 21b of the first passage 21 and the upper / downstream 22a and 22b of the second passage 22 are communicated.

  The first and second passages 21 and 22 have first and second passage check valves 31 (third and fourth one-way) that connect the first and second bidirectional valves 100 and 200 respectively upstream and downstream. Valves) are provided, respectively, and allow only the flow from the upstream to the downstream of the first and second bidirectional valves 100, 200.

  Third and fourth passages 23 and 24 are provided on the downstream sides 21b and 22b of the first and second passages 21 and 22, respectively. The pressures of the first and second passage downstream sides 21b and 22b are introduced into the first and second bidirectional valves 100 and 200 to assist the opening and closing of the valves 100 and 200 (see FIG. 4 for details). .

  The first and second supply oil passages 28 and 29 are provided with first and second suction check valves 53 and 54 (first and second one-way valves) to prevent backflow to the reservoir tank 7. Further, first and second filters 51 and 52 are provided so as to cover the bidirectional ports of the pump P in the first and second supply oil passages 28 and 29, respectively.

  The first and second filters 51 and 52 are separate members on the hydraulic circuit, but actually the first and second supply oil passages 28 and 29 are filtered by one filter 50 (FIGS. 2, 3). reference). In FIG. 1, the first and second filters 51 and 52 are shown for convenience of explanation.

  If the filters 51 and 52 are provided in the reservoir tank communication path 27, contamination may remain in the hydraulic circuit. However, by providing the filters 51 and 52 immediately before suction from the reservoir tank 7 to the pump P, the hydraulic circuit can be entered. To prevent the entry of contamination.

Filter details
FIG. 2 is a radial sectional view in the vicinity of the filter 50 in the pump P, and FIG. 3 is an axial partial sectional view. 3 shows a II cross section of FIG. 2, and FIG. 2 shows a II-II cross section of FIG. In FIG. 3, only the vicinity of the first and second suction check valves 53 and 54 is a sectional view. In addition, let the axial direction reservoir tank 7 side of the pump P be the z-axis positive direction.

  The first and second supply oil passages 28 and 29 which are the supply passages for the hydraulic oil to the pump P are provided in the pump housing 9, and reservoir tanks are provided in openings 28 a and 29 a provided on the radial side surfaces of the pump housing 9. Open to 7. First and second suction check valves 53 and 54 are provided in the openings 28 a and 29 a to prevent backflow from the pump to the reservoir tank 7.

  The filter 50 has a bottomed cup shape, and is provided with filtration portions 50a on the bottom and side surfaces to cover the radial direction and the z-axis positive direction side of the pump housing 9. Thus, the hydraulic oil sucked in both the two openings 28a and 29a is filtered by one filter 50, and contamination entry into the pump P is prevented.

[Details of bidirectional valves]
FIG. 4 is an axial sectional view of the first bidirectional valve 100. The axial pump P side of the first bidirectional valve 100 is the ξ axis positive direction, and the axis orthogonal to the ξ axis and parallel to the drawing is the η axis. The first bidirectional valve 100 is accommodated in the valve hole 11 provided in the first housing 101. Since the second bidirectional valve 200 is the same as the first bidirectional valve 100, only the first bidirectional valve 100 will be described.

  The first bidirectional valve 100 includes a first spool 110, a first poppet valve 120, and a first passage check valve 31. The first passage check valve 31 is formed by a ball valve 130 and a first spring 140.

  The first spool 110 is a cylindrical member and is accommodated in the valve hole 11 so as to be movable in the axial direction. The first poppet valve 120 has a bottomed cup shape, is provided on the negative side of the first spool 110 in the ξ axis, and locks the first spring 140 at the bottom 121.

  A first oil chamber D1 is formed between the first spool 110 and the first poppet valve 120, and the first ball valve 140 is disposed in the first oil chamber D1. The first ball valve 140 moves in the ξ-axis direction within the first oil chamber D1, and switches between communication / blocking between the valve hole 11 and the first oil chamber D1.

(Valve hole)
The valve hole 11 is a hole provided in the first and second housings 101, 102, the ξ axis positive direction side is connected to the upstream side 21 a of the first passage 21 leading to the pump P, and the ξ axis negative direction side is the reservoir It connects with a reservoir tank communication path 27 that reaches the tank 7.

  Further, the first housing 101 is provided with a downstream passage 21b of the first passage 21 from the η positive direction side, opens to the valve hole 11, and the downstream passage 21b of the valve hole 11 communicates. The oil passage that opens to the negative direction side of the η axis of the valve hole 11 is a third passage 23 that introduces the pressure on the first passage downstream side 21 b to the first spool 110.

  The valve hole 11 has a spool housing portion 14 and a poppet valve housing portion 15 for housing the first spool 110 and the first poppet valve 120, respectively. The ξ axis positive direction side 14a of the spool housing portion 14 is provided with a smaller diameter than the negative direction side 14b to form a step portion 14c, and the opening portion 23a of the third passage 23 is provided in the step portion 14c. The opening 21c on the downstream side 21b of the first passage 21 is provided between the spool housing portion 14 and the poppet valve housing portion 15 and communicates with the first oil chamber D1.

(spool)
The first spool 110 is accommodated in the valve hole 11 so as to be movable in the axial direction, and the positive and negative movements in the ξ axis are restricted by a predetermined amount of movement by the locking portions 12 and 13 provided in the valve hole 11.

  Further, the ξ axis positive direction outer peripheral portion 111 of the first spool 110 is provided with a smaller diameter than the negative direction side outer peripheral portion 112 to form a stepped portion 113. The ξ-axis positive and negative direction side outer peripheral portions 111 and 112 are provided with substantially the same diameter as the ξ-axis positive and negative direction side spool housing portions 14a and 14b of the valve hole 11, respectively.

  Therefore, a gap is formed between the ξ axis negative direction side spool receiving portion 14b of the valve hole 11 and the ξ axis positive direction side outer peripheral portion 111 of the first spool 110, and the working hydraulic pressure of the third passage 23 is introduced. A spool drive oil chamber D2 is formed. Accordingly, the step 113 of the first spool 110 functions as a pressure receiving surface on which the hydraulic pressure of the third passage 23 acts.

  Even when the movement amount of the first spool 110 in the positive direction of the ξ axis is maximized, the first spool step 113 and the spool receiving portion step 14c of the valve hole 11 are provided so as not to contact each other. Therefore, the first spool drive oil chamber D2 and the third passage 23 are always in communication, and the hydraulic pressure of the third passage 23 is always applied to the first spool step 113.

  Further, a seal 111a is provided on the outer peripheral portion 111 on the first spool ξ-axis positive direction side, and the first passage upstream side 21a and the first spool driving oil chamber D2 are liquid-tightly defined. Even when the first spool 110 moves in the axial direction, the seal 111a is always provided at a position in contact with the ξ-axis positive direction side spool housing portion 14a.

  Further, the first spool 110 has an axial through hole 116 having a stepped inner periphery. The ξ-axis negative direction side inner peripheral portion 118 of the through hole 116 is provided with a larger diameter than the positive direction side inner peripheral portion 117, and a step portion 119 is formed. The ball valve 130 is inserted into the inner circumferential portion 118 on the ξ-axis negative direction side, and the ball valve 130 is locked in the ξ-axis positive direction by the step portion 119.

(Poppet valve)
As described above, the first poppet valve 120 has a bottomed cup shape and is accommodated in the valve hole 11 so as to be movable in the axial direction like the first spool 110. A spring 140 is inserted on the inner diameter side of the first poppet valve 120, and the inner bottom portion 121 locks the negative ξ axis direction of the spring 140.

  A rib 122 is provided on the radially outer peripheral side of the first poppet valve 120, and the first poppet valve 120 contacts the valve hole 11 at the rib 122. In addition, a contact portion 124 with the second housing 102 is provided on the outer peripheral portion of the outer bottom portion 123, and the first oil chamber D1 and the reservoir tank communication passage 27 are connected by contacting the pedestal portion 103 of the second housing 102. Cut off.

  Since the rib 122 is provided, even if the first poppet valve 120 moves in the positive ξ axis direction, the opening 21c on the first passage downstream side 21b is not closed, and the first passage downstream side 21b and the first passage One oil chamber D1 is always in communication.

(Ball valve)
The first ball valve 140 is disposed between the first spool 110 and the first poppet valve 120, and is biased in the positive ξ axis direction by the spring 130 to form the first passage check valve 31. Further, the first ball valve 140 is restricted from moving in the positive ξ axis direction by the step portion 119 of the first spool 110. Since the first spool 110 serves also as the valve seat of the first passage check valve 31, the number of parts can be reduced.

  Further, the first ball valve 140 completely closes the ξ-axis negative direction opening 116a of the through hole 116 of the first spool 110 when contacting the step portion 119, so that the through hole 116 and the first oil chamber D1 are closed. Block communication. When the differential pressure across the first passage check valve 31 is small, the hydraulic oil is prevented from flowing from the first cylinder chamber 61 side to the reversible pump P side by closing with the spring 130.

[Flow of hydraulic oil in bidirectional valve]
(When the pump side is high pressure)
FIG. 5 is a cross-sectional view in the axial direction of the first bidirectional valve 100 when the pump P side has a high pressure in the first passage 21. FIG. 6 shows the time when the first cylinder 61 is pressurized. At the time of steering assist, the discharge pressure P1 is introduced from the pump P to the first passage upstream side 21a and acts on the ξ axis positive direction side of the ball valve 140 through the through hole 116 of the first spool 110 to cause the ball valve 140 to move to the ξ axis. Energize in the negative direction.

  On the other hand, the cylinder pressure P2 in the first cylinder 61 is introduced into the first oil chamber D1 via the first passage downstream side 21b and acts on the negative ξ axis side of the ball valve 140. The ball valve 140 is biased by the spring 130 toward the ξ axis positive direction.

  Therefore, when the urging force due to the discharge pressure P1 of the pump P exceeds the sum of the urging force of the cylinder pressure P2 and the spring 130, the ball valve 140 moves in the negative ξ axis direction. Thereby, the through hole opening 116a of the first spool 110 is opened, and the first passage upstream side 21a communicates with the first oil chamber D1. Since the first oil chamber D1 and the downstream side 21b are always in communication, the discharge pressure P1 is introduced into the first cylinder chamber 61 via the first oil chamber D1 and the first passage downstream side 21b.

  Since the outer bottom 123 of the first poppet valve communicates with the reservoir tank 7, the discharge pressure P <b> 1 acts on the inner bottom 121 on the ξ axis positive direction side, and the atmospheric release pressure Po acts on the outer bottom 123. Since the discharge pressure P1> atmospheric release pressure Po, the first poppet valve 120 is urged toward the negative side of the ξ axis and comes into contact with the pedestal 103 of the second housing 102, and the first oil chamber D1 and the reservoir tank communication path 27 is blocked.

  During manual steering, the rack shaft 4 is moved by the steering wheel 1, and the volume of the first cylinder chamber 61 is manually increased. In this case, the first cylinder chamber 61 has a negative pressure P2, and the atmospheric release pressure Po is introduced to the upstream side 21a of the first passage 21 connected to the reservoir tank 7 via the first suction check valve 53.

  Therefore, even during manual steering, the pump P side (upstream side 21a) of the bidirectional valve 100 has a higher pressure than the cylinder 6 side (downstream side 21b), and the movement of the bidirectional valve 100 and the flow of hydraulic oil are as shown in FIG. This is the same as when the pump is pressurized.

(When the cylinder side is high pressure)
FIG. 6 is an axial cross-sectional view of the first bidirectional valve 100 in the first passage 21 at the time of high pressure on the cylinder 6 side. FIG. 6 shows the first cylinder chamber 61 when the pressure is reduced. When the first cylinder 61 is depressurized, the pressurization to the first passage upstream side 21a is stopped both when the pump is driven and during manual steering, and the pressure on the pump P side decreases due to leakage from the pump P. Accordingly, the hydraulic pressure P2 on the first cylinder 61 side (downstream side 21b) is higher than the hydraulic pressure P1 on the pump P side (upstream side 21a).

  A downstream pressure P2 acts on the first oil chamber D1 of the first bidirectional valve 100, and an upstream pressure P1 acts on the through hole 116 of the first spool 110. Accordingly, the high pressure P2 acts on the negative side of the ξ axis of the ball valve 140, and the low pressure P1 acts on the positive side, so that the ball valve 140 moves to the positive side of the ξ axis and the opening 116a of the through hole 116 is closed. Thus, the through hole 116 and the first oil chamber D1 are blocked.

  The open bottom pressure Po of the reservoir tank 7 acts on the outer bottom 123 of the first poppet valve 120, and the first poppet valve 120 is urged by the spring 140 in the negative ξ axis direction. On the other hand, the cylinder pressure P2 acts on the contact portion 124 provided on the outer peripheral portion of the outer bottom portion 123 via the rib 122, and urges the first poppet valve 120 to the ξ axis positive direction side.

  Therefore, when the cylinder pressure P2 becomes larger than the sum of the atmospheric release pressure Po and the biasing force of the spring 140, the first poppet valve 120 moves in the positive direction of the ξ axis, and the first passage downstream side 21b and the reservoir tank communication passage 27 communicates. As a result, the hydraulic oil in the first cylinder 61 is discharged to the reservoir tank 7.

  At that time, low pressure P1 acts on the first spool 110 from the ξ-axis positive direction end portion 114, and high pressure P2 acts on the negative direction end portion 115 and the step portion 119. In addition, a biasing force in the positive ξ axis direction by the spring 130 is received via the ball valve 140. A high pressure P2 is introduced into the spool drive oil chamber D2 through the third passage 23, but the pressure receiving area of the step 113 serving as the pressure receiving portion of D2 is smaller than the pressure receiving areas of the negative direction end 115 and the step 119. Therefore, the first spool 110 is biased in the positive ξ axis direction.

  Since the first spool 110 is accommodated in the valve hole 11 so as to be movable in the axial direction, the first spool 110 moves in the positive direction of the ξ axis by this urging force and is locked to the locking portion 12 of the valve hole 11. Therefore, when the first cylinder 61 side (downstream side 21b) has a higher pressure than the pump P side (upstream side 21a), the first spool 110 moves in the positive ξ axis direction together with the first poppet valve 120.

  Therefore, the urging force of the spring 130 acting on the first poppet valve 120 is relaxed, and the positive movement of the first poppet valve 120 in the ξ axis direction is performed smoothly. This improves the valve opening response of the first poppet valve 120.

[Flow of hydraulic oil]
(Hydraulic assist)
7 and 8 are diagrams showing the flow of hydraulic oil in the system at the time of hydraulic assist. 7 shows the case where the rack shaft 4 is assisted in the negative x-axis direction, and FIG. 8 shows the case where the rack shaft 4 is assisted in the positive x-axis direction.

  When assisting the rack shaft 4 in the negative x-axis direction, hydraulic oil is pumped from the reservoir tank 7 via the second filter 52 and the second suction check valve 54 by the pump P, and the hydraulic oil is supplied to the first passage 21.

  At this time, the first passage 21 has a higher pressure than the second passage 22, and the upstream / downstream of the first passage 21 communicates with the first bidirectional valve 100, and hydraulic oil is supplied into the first cylinder chamber 61. On the other hand, in the second bidirectional valve 200, the upstream passage 22a of the second passage 22 is blocked from the downstream passage 22b, and the downstream passage 22b communicates with the reservoir tank communication passage 27.

  Accordingly, all the hydraulic oil discharged as the volume of the second cylinder chamber 62 is reduced is introduced into the reservoir tank 7 by the second bidirectional valve 200 and filtered by the second filter 52 when pumped up again by the pump P. Return to the hydraulic circuit.

  When assisting the rack shaft 4 in the x-axis positive direction, the pump P pumps hydraulic oil from the reservoir tank 7 via the first filter 51 and the first suction check valve 53 and supplies the hydraulic oil to the second passage 22. . The high-pressure second passage 22 is connected upstream / downstream by the second bidirectional valve 200. In the first bidirectional valve 100, the upstream passage 21a of the first passage 21 is blocked, and the downstream passage 21b is a reservoir. It communicates with the tank 7.

  Therefore, all the hydraulic oil discharged as the volume of the first cylinder chamber 61 decreases is introduced into the reservoir tank 7 by the first bidirectional valve 100, filtered by the first filter 51, and returned to the hydraulic circuit. Even when the rack shaft 4 is moved in either the positive or negative direction of the x-axis, all of the hydraulic oil discharged from the power cylinder 6 is introduced into the reservoir tank 7 and is supplied by the first and second filters 51 and 52. Filtered back to the hydraulic circuit.

(Manual steer)
FIG. 9 is a diagram illustrating the flow of hydraulic oil when performing manual steering (addition). FIG. 9 shows a case where the rack shaft 4 is moved in the x-axis negative direction. Since the steering in the positive x-axis direction is performed in the same manner, the description thereof is omitted.

  When the steering wheel 1 is steered to move the rack shaft 4 in the negative x-axis direction, the volume of the first cylinder chamber 61 increases and the volume of the second cylinder chamber 62 decreases. Along with this, the downstream side 21b of the first passage 21 becomes negative pressure, and the upstream 21a, which is the atmospheric release pressure, becomes higher pressure than the downstream 21b. Accordingly, in the first bidirectional valve 100, the upstream 21 a and the downstream 21 b of the first passage 21 communicate with each other, and hydraulic oil is introduced into the first cylinder 62 via the first suction check valve 53.

  On the other hand, as the volume of the second cylinder chamber 62 decreases, the downstream 22b of the second passage 22 becomes high pressure, and in the second bidirectional valve 200, the first passage downstream 22b and the reservoir tank communication passage 27 communicate with each other so that manual steering is performed. Secured. Since all the hydraulic oil discharged from the second cylinder chamber 62 is discharged to the reservoir tank 7, all contamination is captured by the second filter 52.

(Cut back)
During assist and manual steering, the cylinder chamber side on the volume reduction side has a higher pressure than the pump P side when switching back in the positive x-axis direction, and the bidirectional valves 100 and 200 operate in the same manner as in FIG. When switching back in the negative direction of the x-axis, the same operation is performed only by reversing the left and right.

  As described above, even when the assist by the pump P is not performed, the bidirectional valves 100 and 200 that do not use the electromagnetic valve can be increased by turning the steering wheel 1 and switched back. Accordingly, the bidirectional valves 100 and 200 function as fail-safe valves when the system fails.

[Contrast of the effects of the conventional example and the embodiment of the present application]
In the conventional power steering device, the hydraulic pressure discharged from the reversible pump is supplied to the power cylinder, while the passage on the side where the hydraulic pressure from the reversible pump is not supplied by the bidirectional valve is connected to the reservoir tank. The hydraulic oil from the power cylinder is discharged to the reservoir tank.

  However, in the above prior art, a part of the hydraulic oil discharged from one cylinder chamber is discharged to the reservoir tank, so the remaining hydraulic oil is not discharged to the reservoir tank, and is reversible. Inhaled by the pump. Therefore, even if a filter is provided in the suction oil passage from the reservoir tank, there is a problem that the contamination in the pipe may not be sufficiently removed.

  On the other hand, in the present embodiment, the first and second bidirectional valves 100 and 200 are provided in the first and second passages 21 and 22 for connecting the reversible pump P and the power cylinder 6, respectively. The two passages 21 and 22 are connected to the reservoir tank 7 between the pump P and the first and second bidirectional valves 100 and 200, respectively.

  Further, first and second filters 51 and 52 for filtering hydraulic oil are provided between the first and second passages 21 and 22 and the reservoir tank 7, and the first and second passages 21 and 52 are further provided from the reservoir tank 7. First and second suction check valves 53 and 54 that allow only the flow to 22 are provided.

  The first bidirectional valve 100 is controlled to open and close by the differential pressure across the first bidirectional valve 100, that is, the differential pressure between the upstream side 21a and the downstream side 21b of the first passage 21, and at least the pressure P1 on the reversible pump P side. In the first state, in which the pressure is higher than the pressure P2 on the first cylinder chamber 61 side, the reversible pump P side of the first passage 21 and the first cylinder chamber 61 side communicate with each other, and at least the pressure on the reversible pump P side In the second state where P1 is lower than the pressure P2 on the first cylinder chamber 61 side, the first passage upstream side 21a and the downstream side 21b are blocked, and the downstream side 21b and the reservoir tank 7 are communicated with each other. did.

  Similarly, the second bidirectional valve 200 is also controlled to open and close by the differential pressure difference between the upstream side 22a and the downstream side 22b of the second passage 22, and at least the pressure P1 on the reversible pump P side is the pressure P2 on the second cylinder chamber 62 side. In the second higher state, the second passage upstream side 22a and the downstream side 22b communicate with each other, and at least in the second state where the upstream pressure P1 is lower than the downstream pressure P2, the second passage 22 upstream. The side 22a and the downstream side 22b are blocked, and the downstream side 22b and the reservoir tank 7 are communicated with each other.

  Thus, during normal steering assist, the hydraulic oil discharged from the volume decreasing side of the first or second cylinder chamber 61, 62 is discharged to the reservoir tank 7 while the first or second cylinder chamber 61, 62 is discharged. The hydraulic oil filtered by the first or second filter 51, 52 can be supplied to the volume expansion side. Therefore, it is possible to prevent the hydraulic oil discharged from the power cylinder 6 from being supplied as it is without being filtered, and to improve the hydraulic oil filtration performance.

  In addition, first and second filters 51 and 52 are provided so as to cover the bidirectional ports of the pump P in the first and second supply oil passages 28 and 29, respectively. If the filters 51 and 52 are provided in the reservoir tank communication path 27, contamination may remain in the hydraulic circuit. However, by providing the filters 51 and 52 immediately before suction from the reservoir tank 7 to the pump P, the hydraulic circuit can be entered. It is possible to reliably prevent the entry of contamination.

  The first and second bidirectional pumps 100 and 200 are provided with first and second passage check valves 31 and 32 that allow only the flow from the pump P side to the cylinder 6 side. The first and second passage check valves 31 and 32 are formed by ball valves 140 and 240 and springs 140 and 240. When the differential pressure across the front and rear is small, the first and second passage check valves 31 and 32 are reversible from the cylinder 6 side by closing them. It is possible to prevent the hydraulic oil from flowing to the pump P side.

  The first spool 110 is accommodated in the valve hole 11 so as to be movable in the axial direction. Accordingly, when the cylinder 6 side is higher than the pump P side, the first spool 110 and the first spool 110 are moved in the positive ξ axis direction, so that the biasing force of the spring 130 acting on the first poppet valve 120 is reduced. The valve opening response of the first poppet valve 120 can be improved by relaxing.

  Further, in the first and second bidirectional valves 100 and 200, the ball valves 140 and 240 are restricted from moving in the positive ξ axis direction by the step portions 119 and 219 of the spools 110 and 210, respectively. Since the spools 110 and 210 also serve as valve seats for the first and second passage check valves 31 and 32, the number of parts can be reduced.

In addition, the mechanical two-way valves 100 and 200 can perform a fail-safe valve function. Therefore, manual steering can be secured without using a solenoid valve.
(Other examples)

  The best mode for carrying out the present invention has been described based on the embodiments. However, the specific configuration of the present invention is not limited to each embodiment, and the scope of the invention is not deviated. Design changes and the like are included in the present invention.

  Further, technical ideas other than the claims that can be grasped from the above embodiments will be described below together with the effects thereof.

(A) In the power steering apparatus according to claim 1,
The power steering device according to claim 1, wherein the filter is provided so as to cover a suction port through which the reversible pump sucks hydraulic oil from the reservoir tank.

  When a filter is provided at the discharge port from which the reversible pump discharges hydraulic oil to the reservoir tank, there is a risk that contamination will remain in the pump. Can be discharged. Further, when the reversible pump sucks the hydraulic oil from the reservoir tank again, the contamination in the hydraulic oil is removed by the filter.

(B) In the power steering device according to claim 1,
The first bidirectional valve is provided with a third one-way valve that allows only the flow of hydraulic oil from the reversible pump side to the power cylinder side of the first passage, and the third one-way valve is provided in a valve closing direction. An urging means for energizing,
The second bidirectional valve is a fourth one-way valve that allows only the flow of hydraulic oil from the reversible pump side to the power cylinder side of the second passage, and the fourth one-way valve is provided in the valve closing direction. And a biasing means for biasing the power steering device.

  When the differential pressure across the third and fourth one-way valves is small, the hydraulic oil can be prevented from flowing from the power cylinder side to the reversible pump side by closing the valve with the urging means.

(C) In the power steering device according to claim 1,
The first bidirectional valve and the second bidirectional valve include valve accommodating holes formed in the first passage and the second passage,
A spool valve that is movably accommodated in the valve accommodation hole and has an axial through hole;
A one-way valve that is provided closer to the power cylinder than the spool valve and allows only a flow from the reversible pump side to the power cylinder side of the hydraulic oil passing through the axial through hole;
A power steering device comprising: a poppet valve provided integrally with the spool valve and switching communication / blocking between the power cylinder and the reservoir tank.

  The spool valve is operated by the hydraulic pressure when the hydraulic oil returns from the power cylinder side, and the poppet valve can be opened at the same time using this operating force. it can.

(D) In the power steering device described in (c) above,
The one-way valve of the first bidirectional valve and the second bidirectional valve comprises a valve seat formed on the spool valve and a ball member seated on the valve seat. apparatus.

  Since the spool valve also serves as the valve seat of the one-way valve, the number of parts can be reduced.

(E) In the power steering device according to claim 1,
The bidirectional steering valve is a mechanical valve.

  Since the bidirectional valve also functions as a fail-safe valve when the system fails, manual steering can be ensured without using an electromagnetic valve.

It is a system configuration figure of this application power steering device. It is radial direction sectional drawing of the filter vicinity in a pump. It is an axial direction fragmentary sectional view of the filter vicinity in a pump. It is an axial sectional view of the first bidirectional valve. It is an axial sectional view of the 1st bidirectional valve at the time of pump side high pressure. It is an axial sectional view of the 1st bidirectional valve at the time of cylinder side high pressure. It is a figure which shows the flow of the hydraulic fluid in a system at the time of x-axis negative direction assist. It is a figure which shows the flow of the hydraulic fluid in a system at the time of x-axis positive direction assist. It is a figure which shows the flow of the hydraulic fluid at the time of performing a manual steer (addition).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Shaft 3 Pinion 4 Rack shaft 5 Torque sensor 6 Cylinder 7 Reservoir tank 8 Control unit 9 Pump housing 11 Valve hole 12, 13 Locking part 14 Spool receiving part 14c Spool receiving part step part 14a, 14b ξ axis Positive and negative direction side spool accommodating portion 14c Step portion 15 Poppet valve accommodating portion 21, 22 First and second passages 21a and 21b First and second upstream passages 22a and 22b First and second downstream passages 23 , 24 Third and fourth passages 23a Third passage opening 27 Reservoir tank communication passages 28 and 29 First and second supply oil passages 28a and 29a Openings 31 and 32 First and second passage check valves 50 Filter 50a Filtration Portions 51 and 52 First and Second Filters 53 and 54 First and Second Suction Check Valves 61 and 62 First and Second Cylinder Chamber 63 Stone 100, 200 First, second bidirectional valve 101, 102 First, second housing 103 Base 110 110 Spool 111a Seal 111, 112 ξ positive, negative outer peripheral 113 Spool step 114, 115 ξ Axial positive and negative direction end portion 116 Through hole 116a Through hole opening portion 117 Positive direction side inner peripheral portion 118 Axis negative direction side inner peripheral portion 119 Step portion 120 First poppet valve 121 Inner bottom portion 122 Rib 123 Outer bottom portion 124 Contact portion 140 First ball valve

Claims (1)

A hydraulic power cylinder for assisting the steering force of the steering mechanism connected to the steering wheel;
A reversible pump comprising a pair of discharge ports for supplying hydraulic pressure to both pressure chambers of the hydraulic power cylinder via first and second passages;
An electric motor for rotating the reversible pump forward and reverse;
Steering assist force detecting means for detecting a steering assist force to be applied to the steered wheels;
Motor control means for outputting a drive signal to the electric motor in order to generate a desired hydraulic pressure on the electric motor based on the steering assist force detected by the steering assist force detecting means;
A first bidirectional valve provided in the first passage;
A second bidirectional valve provided in the second passage;
A reservoir tank for storing hydraulic oil;
A filter provided in the reservoir tank for filtering hydraulic oil;
Opening in the first passage between the reversible pump and the first bidirectional valve;
A first one-way valve provided between the first passage and the reservoir tank and allowing only a flow from the reservoir tank to the first passage;
Opened in the second passage between the reversible pump and the second bidirectional valve, and is provided between the second passage and the reservoir tank, and only flows from the reservoir tank to the second passage. A second one-way valve to allow,
The first bidirectional valve is controlled to open and close by the differential pressure across the first bidirectional valve. At least in the first state, the pressure on the reversible pump side is higher than the pressure on the power cylinder side. The reversible pump of the first passage is in a second state where the reversible pump side of the passage and the power cylinder side communicate with each other and at least the pressure on the reversible pump side is lower than the pressure on the power cylinder side Shutting off the power cylinder side and the power cylinder side, and communicating the first passage on the power cylinder side and the reservoir tank,
The second bidirectional valve is controlled to open and close by the differential pressure across the second bidirectional valve, and at least in the first state, the pressure on the reversible pump side is higher than the pressure on the power cylinder side, the second The reversible pump of the second passage is in a second state in which the reversible pump side of the passage and the power cylinder side are communicated, and at least the pressure on the reversible pump side is smaller than the pressure on the power cylinder side The power steering device is characterized in that the side of the power cylinder and the side of the power cylinder are shut off, and the second passage on the side of the power cylinder and the reservoir tank are communicated.

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