JP2006335297A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device capable of efficiently performing filling of an operation oil. <P>SOLUTION: The power steering device is provided with a reversible pump provided with a pair of delivery port for feeding an oil pressure to both pressure chambers of a hydraulic power cylinder through first and second passages; a first one-way valve provided in the first passage and only allowing a flow of the operation oil from a reservoir tank side to the first passage side; a second one-way valve provided on the second passage and only allowing the flow of the operation oil from the reservoir tank side to the second passage side; a third one-way valve provided in the first passage and only allowing the flow of the operation oil from the first passage side to the reservoir tank side; a fourth one-way valve provided on the second passage and only allowing the flow of the operation oil from the second passage side to the reservoir tank side; a pump control means for rotating/driving the reversible pump in a direction for feeding the operation oil to the pressure chamber at the side where the reversible pump is stopped or the volume is reduced when filling work of the operation oil is performed. <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, a power cylinder chamber, a reversible pump connected to the power cylinder chamber, and a motor that drives the reversible pump to rotate forward and backward, Steering assist force is obtained by selectively supplying hydraulic pressure to the left and right pressure chambers of the power cylinder chamber.

In such a power steering device, when working oil is filled in a maintenance shop or the like without a vacuum evacuation device, the steering wheel is first rotated left and right, and the piston in the power cylinder chamber is moved left and right. Then, the cylinder chamber on the side where the volume increases becomes negative pressure, and the hydraulic oil in the reservoir tank is supplied to this cylinder chamber. By repeating this operation on the left and right, the hydraulic oil can be filled into the left and right cylinder chambers and other hydraulic circuits.
JP 2004-306721 A

  However, in the above-described prior art, air existing in the cylinder chamber on the volume decreasing side is supplied to the cylinder chamber on the volume increasing side through the reversible pump simultaneously with the hydraulic oil. Therefore, even if the steering wheel rotation operation is repeated on the left and right, there is a problem that the air contained in the apparatus alternately moves back and forth between the left and right cylinder chambers and the hydraulic oil cannot be efficiently filled.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a power steering device capable of efficiently performing a hydraulic oil filling operation.

  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. Steering load detection for detecting or estimating a steering load of a reversible pump having a pair of discharge ports for supplying hydraulic pressure, a motor for rotating the reversible pump forward and backward, and a steering wheel for steering control of the steered wheels Means, a reservoir tank for storing hydraulic oil, a first one-way valve provided in the first passage and allowing only the flow of hydraulic oil from the reservoir tank side to the first passage side, and the second A second one-way valve provided in the passage and allowing only a flow of hydraulic oil from the reservoir tank side to the second passage side; and provided in the first passage, from the first passage side to the reservoir tank side. What A third one-way valve that allows only the flow of hydraulic oil; a fourth one-way valve that is provided in the second passage and that allows only the flow of hydraulic oil from the second passage side to the reservoir tank; When performing the hydraulic oil filling operation, the reversible pump is stopped or provided with pump control means for rotationally driving the hydraulic oil in the direction of supplying the hydraulic oil to the pressure chamber whose volume is reduced.

  Therefore, it is possible to provide a power steering apparatus that can efficiently mix the hydraulic oil while avoiding air mixing.

  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. When the driver steers the steering wheel 2, the pinion 4 is driven through the shaft 3, and the rack shaft 5 is moved in the axial direction by a so-called rack and pinion mechanism to steer the front wheels. The shaft 3 is provided with a torque sensor 6 that detects the steering torque of the driver, and outputs a torque signal to the control unit 7.

  The rack shaft 5 is provided with a power steering mechanism that assists the movement of the rack shaft 5 according to the steering torque of the driver. This power steering mechanism is provided with a reversible pump 1 driven by a motor M and a cylinder chamber 8 for moving the rack shaft 5 to the left and right. A piston 83 that can move in the axial direction is provided inside the cylinder chamber 8, and a first cylinder chamber 81 and a second cylinder chamber 82 are defined by the piston 83.

  The first cylinder chamber 81 is connected to the first passage 21, and the first passage 21 is connected to the pump 1. The second cylinder chamber 82 is connected to the second passage 22, and the second passage 22 is connected to the pump 1.

  The first and second passages 21 and 22 are provided with first and second check valves 31 and 32, respectively, to prevent backflow of hydraulic oil to the reservoir tank 9, and in the first and second passages 21 and 22, respectively. When the hydraulic oil is insufficient, the hydraulic oil can be supplied from the reservoir tank 9.

  The first and second passages 21 and 22 are connected to each other at the connection portion 27, and the connection portion 27 is connected to the reservoir tank 9 via the electromagnetic switching valve 40. As a result, the connecting portion 27 is communicated / blocked with the reservoir tank 9 by the electromagnetic switching valve 40. Furthermore, the first and second passages 21 and 22 are respectively provided with third and fourth check valves 33 and 34 that allow only the flow to the electromagnetic switching valve 40.

  The first and second passages 21 and 22 communicate with the spool valve 50, and the spool valve 50 is connected to the reservoir tank 9 via the return passage 60. When the first passage 21 and the return passage 60 are communicated by the spool valve 50, the second passage 22 and the return passage 60 are blocked, and when the second passage 22 and the return passage 60 are communicated. The first passage 21 and the return passage 60 are configured to be blocked.

  The return passage 60 is provided with a return passage check valve 35 that allows only the flow from the spool valve 50 to the reservoir tank 9 to prevent backflow from the reservoir tank 9. Further, a normally open electromagnetic switching valve 40 is provided between the first and second passages 21 and 22 to perform communication / blocking.

  In addition to the torque signal from the torque sensor 6, the control unit 7 receives a switch signal from the ignition switch, an engine speed signal from the engine speed sensor, a vehicle speed signal from the vehicle speed sensor, and the like. The steering assist force is determined, and a command signal is output to the motor M and the electromagnetic switching valve 40. In addition, at the time of hydraulic oil filling, a command is output by an electric signal so as to restrain the rotation of the motor M (pump control means).

  The normally open electromagnetic switching valve 40 is normally closed and is opened at the time of failure to ensure manual steering.

[Filling hydraulic fluid]
FIG. 2 is a schematic diagram of a hydraulic circuit at the time of hydraulic oil filling. The bold line indicates the flow of hydraulic oil, and the alternate long and short dash line indicates the flow of air. When the hydraulic oil is filled, the rotation of the motor M is restricted by a command from the control unit 7.

  The rotation restriction of the motor M may be performed by a command from the control unit 7 or may be performed by connecting another control device to the motor M during the filling operation, and is not particularly limited.

  Further, the spool valve 50 communicates the low pressure side of the first and second passages 21 and 22 with the reservoir tank 9 and shuts off the high pressure side and the reservoir tank 9 only when the hydraulic oil is filled.

  When the rack shaft 5 is moved in the left direction in the figure, the first cylinder chamber 81 becomes positive pressure and the second cylinder chamber 82 becomes negative pressure. In addition, the electromagnetic switching valve 40 shall be opened at the time of hydraulic fluid filling.

  Accordingly, the air in the first cylinder chamber 81 is pushed out to the first passage 21. Here, since the motor M is restricted in rotation, the pump 1 does not rotate, and the air in the first passage 21 does not move to the second passage 22 via the pump 1. The air leaking in the pump 1 is introduced into the return passage check valve 35 and discharged to the reservoir tank 9.

  The air pushed out into the first passage 21 also acts on the first check valve 31 and the third check valve 33. Since the flow from the first passage 21 to the reservoir tank 9 side is blocked by the first check valve 31 and allowed by the third check valve 33, the air is discharged to the reservoir tank 9 through the third check valve 33. .

  Furthermore, since the spool valve 50 shuts off the high-pressure side and the reservoir tank 9, the first passage 21 and the reservoir tank 9 are shut off, and air is not discharged to the reservoir tank 9 via the spool valve 50.

  On the other hand, the second cylinder chamber 82 has a negative pressure as its volume increases, and the second passage 22 communicating with the second cylinder chamber 82 also has a negative pressure. As described above, since the rotation of the motor M is restricted, the air in the first passage 21 does not move to the second passage 22 via the pump 1 even if the second passage 22 has a negative pressure. .

  In addition, since the flow from the reservoir tank 9 to the second passage 22 is permitted by the second check valve 32 and is blocked by the fourth check valve 34, the second passage 22 is negative with respect to the reservoir tank 9 released to the atmosphere. When the pressure is reached, the hydraulic oil in the reservoir tank 9 is introduced into the second passage 22 only through the second check valve 32, and no hydraulic oil is supplied from the fourth check valve 34.

  Further, since the spool valve 50 shuts off the high pressure side and the reservoir tank 9, the second passage 22 and the reservoir tank 9 are communicated with each other. Therefore, hydraulic oil is supplied to the second passage 22 from the spool valve 50 in addition to the second check valve 32.

  Thus, when the hydraulic oil is filled, the motor M is restrained from rotating, the spool valve 50 shuts off the high-pressure side and the reservoir tank 9, and the third and fourth check valves 33 and 34 are provided. The first and second passages 21 and 22 do not directly communicate with each other, and the air discharged from the first cylinder chamber 81 and the hydraulic oil supplied to the second cylinder chamber 82 do not mix.

  Therefore, by moving the rack shaft 5 in the left direction in the figure, the air in the first cylinder chamber 81 is discharged to the reservoir tank 9 and is operated without mixing air from the reservoir tank 9 into the second cylinder chamber 82. Oil can be supplied. Conversely, if the rack shaft 5 is moved in the right direction in the figure, the hydraulic oil is supplied to the first cylinder chamber 81 and the air in the second cylinder chamber 82 is discharged without mixing the hydraulic oil and air. Can do.

  In this way, by alternately moving the rack shaft 5 to the left and right, air discharge from the first and second cylinder chambers 81 and 82 and hydraulic oil supply are performed alternately. While each cylinder chamber 81, 82 is not completely filled with hydraulic oil, air and hydraulic oil are mixed in each cylinder chamber, and the hydraulic oil mixed with air is discharged as the volume decreases due to movement of the piston 83. As described above, since the communication between the first and second passages 21 and 22 is completely cut off, only the hydraulic oil from the reservoir tank 9 is supplied to the cylinder chamber on the hydraulic oil supply side (volume increase side). The By repeating this, all the air in the cylinder chamber 8 is discharged and the hydraulic oil is efficiently filled.

[Contrast of effects of conventional example and first embodiment]
FIG. 3 is a schematic view showing hydraulic oil filling in the prior art. In a conventional power steering device, when working with hydraulic oil at a maintenance shop or the like without a vacuum evacuation device, the piston of the power cylinder chamber is moved to the left and right, and the cylinder chamber on the side where the volume is increased is negatively pressurized. The hydraulic oil is supplied to the cylinder chamber on the negative pressure side.

  However, in the above prior art, when hydraulic fluid is supplied to the cylinder chamber on the volume increase side, air in the cylinder chamber on the volume decrease side is also supplied simultaneously via the reversible pump. Therefore, even if the piston is moved to the left and right, there is a problem that the air contained in the apparatus alternately moves between the left and right cylinder chambers, so that the working oil cannot be efficiently filled.

  On the other hand, in the first embodiment of the present application, first and second check valves 31 and 32 that allow only the flow from the reservoir tank 9 are provided in the first and second passages 21 and 22, and the third and fourth checks are further performed. Only the flow from the passages 21 and 22 to the reservoir tank 9 is allowed by the valves 33 and 34.

  Further, the bidirectional pump 1 driven by the motor M is provided between the first and second check valves 31 and 32, and the motor M is restricted from rotating when the hydraulic oil is filled. Further, in the hydraulic circuit in the present application, the reservoir tank 9 is connected between the third and fourth check valves 33 and 34.

  Thus, the first and second passages 21 and 22 are not directly communicated when the hydraulic oil is filled, and the air discharged from the high-pressure side cylinder chamber and the hydraulic oil supplied to the low-pressure side cylinder chamber are filled when the hydraulic oil is filled. It becomes possible to avoid mixing, and hydraulic oil can be filled efficiently.

  In addition, by opening the electromagnetic switching valve 40 while the hydraulic oil is being filled, the hydraulic oil containing a large amount of air is discharged from the pipe to the reservoir tank 9, and the electromagnetic switching valve 40 is closed during normal assist. The pump pressure can be prevented from leaking to the reservoir tank 9. Furthermore, the valve can be opened at the time of failure, and can also be used as a switching valve for securing manual steering for communicating the first and second passages 21 and 22, thereby simplifying the apparatus.

  In addition, since the rotation of the motor M is restricted by an electric signal command from the control unit 7 when the hydraulic oil is filled, the rotation of the motor M can be controlled without adding or changing the mechanical configuration.

  The second embodiment will be described with reference to FIGS. Since the basic configuration is the same as that of the first embodiment, only different points will be described. In the first embodiment, only the rotation of the motor M is restricted, but in the second embodiment, the motor M is positively rotated, and the cylinder chamber on the side where the volume of the first and second cylinder chambers 81 and 82 decreases. The first embodiment is different from the first embodiment in that the pump 1 is driven in the direction in which the hydraulic oil is supplied.

  FIG. 4 is a schematic diagram showing the flow of hydraulic oil and air when the volume of the first cylinder chamber 81 decreases. As in Example 1, hydraulic oil is indicated by a bold line, and air is indicated by a one-dot chain line.

  The steering wheel 2 is rotated to move the piston 83 in the left direction in the figure, so that the first cylinder chamber 81 has a positive pressure and the second cylinder chamber 82 has a negative pressure. At the same time, the motor 1 is rotated to drive the pump 1 in a direction to supply hydraulic oil to the second cylinder chamber 82.

  Since the first and second cylinder chambers 81 and 82 have positive and negative pressures, respectively, the first and second passages 21 and 22 also have positive and negative pressures, respectively. The air is introduced from the first cylinder chamber 81 and discharged from the third check valve 33 to the reservoir tank 9, and the second passage 22 is supplied with hydraulic oil from the reservoir tank 9.

  At this time, the hydraulic oil supplied from the reservoir tank 9 via the second check valve 32 is also supplied to the first passage 21 side by driving the pump 1. Therefore, the air discharged from the first cylinder chamber 81 to the first passage 21 does not enter the second passage 22 side via the pump 1, and the hydraulic oil not mixed with air is reliably supplied to the second passage 22. And it becomes possible to supply to the second cylinder chamber 82.

When supplying the hydraulic oil to the first cylinder chamber 81, the piston 83 is moved rightward in the drawing as shown in FIG. 5, and the pump 1 is driven in a direction to supply the hydraulic oil to the first cylinder chamber 81. Thereby, hydraulic fluid can be supplied to the 1st cylinder chamber 81, without mixing air.
By moving the piston 83 alternately left and right and changing the driving direction of the pump 1 alternately left and right accordingly, hydraulic oil is supplied to both the cylinder chambers 81 and 82 without mixing air. Similar effects can be obtained.

  Further, since the pump 1 is driven in a direction in which the hydraulic oil is supplied to the cylinder chamber on the side of which the volume is reduced among the first and second cylinder chambers 81 and 82, the air discharged from the cylinder chamber on the volume reduction side is pumped. It is possible to reliably avoid entering the cylinder chamber on the volume increase side through 1, and air mixing can be further suppressed as compared with the first embodiment.

  A third embodiment will be described with reference to FIGS. The third embodiment is different from the first embodiment in that a pressure relief valve 200 is provided as a pressure control means.

  Here, in the case where a pair of relief valves are provided in each of the oil passages communicating with the suction / discharge ports of the bidirectional pump, two relief valves are required, which increases the cost of the apparatus.

  Therefore, in the third embodiment, one pressure relief valve 200 is connected to both sides of the suction / discharge port of the pump 1, and the pressure relief valve 200 avoids excessive pressure in the oil passage communicating with the suction / discharge port. . When the hydraulic pressure in the apparatus becomes equal to or higher than a predetermined value, the pressure can be reduced by the pressure relief valve 200, so that it is possible to avoid malfunction of the apparatus.

  FIG. 6 is a hydraulic circuit diagram of the power steering apparatus of the present application when the pump 1 is not operated. The pressure relief valve 200 is provided in the fourth passage 24 that connects the switching valve 100 and the reservoir tank 9, and the switching valve 100 is provided on the third passage 110 that connects the first and second passages 21 and 22. It has been. The switching valve 100 selects the high pressure side of the first and first passages 21 and 22 to communicate with the pressure relief valve 200.

  Since the pump pressure is not generated when the pump is not operated, the pressure difference between the first and second passages 21 and 22 connected to the bidirectional pump 1 does not occur. Therefore, the switching valve 100 is neutral, and both the first and second passages 21 and 22 are disconnected from the reservoir tank 9.

  FIG. 7 is a hydraulic circuit diagram when the second cylinder chamber 82 is pressurized. The hydraulic oil is pumped from the first cylinder chamber 81 by the pump 1 and supplied to the second passage 22 and the second cylinder chamber 82. Accordingly, the hydraulic pressure in the second passage 22 is higher than that in the first and third passages 31 and 33, and the hydraulic pressure in the second cylinder chamber 82 is selected by the switching valve 100 and acts on the pressure relief valve 200.

  At this time, when the hydraulic pressure in the second cylinder chamber 82 becomes excessive, the pressure relief valve 200 is opened, the second cylinder chamber 82 and the reservoir tank 9 are communicated, and the excessive hydraulic pressure is discharged. When the excessive hydraulic pressure is eliminated and the pressure becomes an appropriate pressure, the pressure relief valve 200 is closed, and the hydraulic pressure in the second cylinder chamber 82 is maintained appropriately.

  FIG. 8 is a hydraulic circuit diagram when the first cylinder chamber 81 is pressurized. As in FIG. 7, the hydraulic pressure in the first cylinder chamber 81 pressurized by the pump 1 acts on the pressure relief valve 200 by the switching valve 100, and when the hydraulic pressure becomes excessive, the pressure relief valve 200 is opened and the first cylinder chamber 81 is opened. Keep the pressure at an appropriate level.

[Details of switching valve]
FIG. 9 is a cross-sectional view of the switching valve 100. The switching valve 100 includes a housing 101, a valve body 120, a valve seat 130, and a spring 140. A third passage 110 is provided inside the housing 101, and the third passage 110 is formed by a valve body housing portion 111 and valve seat housing portions 112 provided at both ends of the valve body housing portion 111.

  The valve body 120 is housed in the valve body housing part 111 so as to be movable in the axial direction, and is urged toward the center of the valve body housing part 111 by a pair of springs 140. The third passage 110 and the valve body 120 have a circular cross section so that the third passage 110 can be easily formed by drilling.

  Two valve seats 130 are provided on both sides of the valve body 120, and are fitted to the valve seat housing portion 112 while restricting axial movement. The valve seat housing portion 112 is provided with a larger diameter than the valve body housing portion 111.

  Therefore, a step at the boundary between the valve body housing portion 111 and the valve seat housing portion 112 is formed, and the first and second locking portions 115 and 116 to which the first and second sealing materials 113 and 114 are locked are formed. . Sealing performance is improved by sandwiching the sealing materials 113 and 114 between the valve seat 130 and the first and second locking portions 115 and 116.

  Further, when the valve body 120 moves in the axial direction, it comes into contact with the sealing materials 113 and 114, and the collision noise is suppressed. Therefore, the sealing materials 113 and 114 also function as a cushioning material for the valve body 120.

  The valve seat 130 is substantially cup-shaped, and the spring 140 is inserted from the opening 131. The opening 131 fits together with the valve body accommodating portion 111 together with the bottom 132, and the outer peripheral cylindrical portion 133 between the opening 131 and the bottom 132 is provided with a smaller diameter than the opening 131 and the bottom 132.

  Accordingly, the valve seat 130 and the valve seat housing portion 112 do not come into contact with each other in the outer cylindrical portion 133. Further, first and first passages 21 and 22 (see FIGS. 6 to 8) are opened at positions corresponding to the outer cylindrical portion 133 in the valve seat accommodating portion 112, and the outer cylindrical portion 133, the valve seat accommodating portion 112, and the like. This gap becomes the first and second oil chambers 150 and 160 where the hydraulic pressures of the first and second passages 21 and 22 act.

  The outer cylindrical portion 133 is provided with a radial through hole 134, and third and fourth oil chambers between the valve body 120 and the valve seat 130 via the inner peripheral portion 135 of the substantially cup-shaped valve seat 130. Communicate with 170,180. Thus, the first and second passages 21 and 22 communicate with the third and fourth oil chambers 170 and 180, and the hydraulic pressures of the first and second cylinder chambers 81 and 82 are the third and fourth oil chambers 170 and 180. Is also applied to the first pressure receiving surface 121 of the valve body 120.

  When hydraulic oil is supplied to the first cylinder chamber 82 by the pump 1, the third oil chamber 170 becomes higher than the fourth oil chamber 180, and the valve body 120 is shown in the figure if the differential pressure exceeds the urging force of the spring 140. The third oil chamber 170 and the fourth passage 24 (see FIGS. 6 to 8) communicate with each other by moving to the right, and the hydraulic pressure in the first cylinder chamber 81 is pressured through the first and third oil chambers 150 and 170. It acts on the relief valve 200.

  Conversely, when hydraulic fluid is supplied to the second cylinder chamber 82, the valve body 120 is biased at the second pressure receiving surface 122. For this reason, the valve body 120 moves leftward in the figure, and the hydraulic pressure in the second cylinder chamber 82 acts on the pressure relief valve 200 via the second and fourth oil chambers 160 and 180. As a result, it is possible to release the excessive pressure in the first and second cylinder chambers 81 and 82 with one pressure relief valve 200.

  Further, when the hydraulic pressure difference between the first and second passages 21 and 22 is not generated, the pair of springs 140 urge the valve body 120 to maintain the axial position of the valve body 120 at the neutral position. The first and second passages 21 and 22 do not communicate with the fourth passage. Therefore, the pressure balance between the first passage 21 and the second passage 22 is maintained in a state where no hydraulic pressure is applied to the valve body 120.

  Further, when one side in the axial direction of the switching valve 100 is high pressure, the operability of the valve body 120 can be improved by communicating the other side with the low pressure side. In addition, the hydraulic oil pushed out by the movement of the valve body 120 can be discharged to the reservoir tank 9.

[Contrast of effects of the conventional example and the third embodiment of the present application]
Conventionally, in a hydraulic circuit of a power steering apparatus, two pressure relief valves are provided and communicated with the left and right cylinder chambers, respectively, to avoid excessive pressure in the circuit. However, this technique requires two pressure relief valves, which increases the number of parts and the complexity of the apparatus, resulting in an increase in cost.

  Further, as shown in FIG. 10, it is possible to provide two passages 24a and 24b from the switching valve 100 ′ to the pressure relief valve 200 so that only one pressure relief valve 200 is provided. It is not preferable.

  On the other hand, in the third embodiment of the present invention, the third passage 110 connecting the first passage 21 and the second passage 22, the fourth passage 24 branched from the third passage 110, and the fourth passage 24 are connected. The pressure relief valve 200 and the first pressure receiving surface 121 are provided so as to be movable in the third passage 110 and receive the hydraulic pressure from the first passage 21 and the hydraulic pressure from the second passage 22 at both axial ends. And a second pressure receiving surface 122, which are moved by a pressure difference between the first pressure receiving surface 121 and the second pressure receiving surface 122, and the communication between the first passage 21 and the fourth passage 24, the blocking and the second passage 22. And the switching valve 100 for switching between communication and blocking with the fourth passage 24.

  As a result, it is not necessary to provide the pressure relief valve 200 (pressure control means) in each of the first passage 21 and the second passage 22, so that the cost of the apparatus can be reduced. In addition, since only the fourth passage 24 is the communication passage connecting the third passage 110 and the pressure relief valve 200, the hydraulic circuit can be simplified.

  A fourth embodiment will be described with reference to FIGS. The basic configuration is the same as that of the third embodiment. In the third embodiment, the pressure relief valve 200 is used as the pressure control means. However, the fourth embodiment is different in that an accumulator 300 is used.

  FIG. 11 is a hydraulic circuit diagram when the pump 1 is not in operation. As in FIG. 6 of the third embodiment, since no pump pressure is generated, a pressure difference between the first and second passages 21 and 22 connected to the bidirectional pump 1 does not occur. Accordingly, the switching valve 100 is neutral and both the first and second passages 21 and 22 are disconnected from the reservoir tank 9, so that the hydraulic pressures of the first and second passages 21 and 22 do not act on the accumulator 300.

  FIG. 12 is a hydraulic circuit diagram when the second cylinder chamber 82 is pressurized. The hydraulic pressure in the second passage 22 is higher than the hydraulic pressure in the first and third passages 31 and 33, and the hydraulic pressure in the second cylinder chamber 82 is selected by the switching valve 100 and acts on the accumulator 300. When the second cylinder chamber 82 becomes an excessive hydraulic pressure, the excessive hydraulic pressure is accumulated in the accumulator 300, and the hydraulic pressure in the second cylinder chamber 82 is maintained appropriately.

  FIG. 13 is a hydraulic circuit diagram when the first cylinder chamber 81 is pressurized. Similar to FIG. 12, the hydraulic pressure in the first cylinder chamber 81 is applied to the accumulator 300 by the switching valve 100, and when it becomes an excessive hydraulic pressure, it is accumulated to keep the first cylinder chamber 81 at an appropriate pressure.

In this way, by using the accumulator 300 as the pressure control means connected to the switching valve 100, it is not necessary to provide the accumulator 300 in each of the first passage 21 and the second passage 22, and the same effects as in the third embodiment can be obtained. Obtainable. Further, since the pulsation of the discharge pressure of the pump is generated in the pressure side oil passage, the pulsation caused by the pump 1 can be reduced by controlling the switching valve 100 so that the pressure side oil passage and the accumulator 300 are communicated. .
(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 reservoir tank side of the third one-way valve and the reservoir tank side of the fourth one-way valve are connected, and a switching valve is further provided on the reservoir tank side than this connection,
The switching valve is opened when hydraulic oil is charged, and closed in the assist state of the power steering device.

  During the filling operation, by opening the switching valve, the hydraulic oil containing a large amount of air can be discharged from the pipe to the reservoir tank side. Further, by closing the valve in the assist state, it is possible to prevent the assist pressure from leaking to the reservoir tank.

(B) In the power steering device described in (a) above,
The switching valve is opened when the above occurs in the power steering device.

  When the apparatus is abnormal, the apparatus can be simplified by using the switching valve that communicates the first passage and the second passage.

(C) In the power steering device according to claim 1,
The power steering apparatus according to claim 1, wherein the pump control means is an electric signal command for controlling a motor connected to the reversible pump.

  The rotation of the reversible pump can be controlled without adding or changing the mechanical configuration.

(D) a hydraulic power cylinder for assisting the steering force of the steering mechanism coupled 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 third passage connecting the first passage and the second passage;
A fourth passage branched from the third passage;
Pressure control means connected in the fourth passage;
A first pressure-receiving surface and a second pressure-receiving surface, which are movably provided in the third passage, and respectively receive the hydraulic pressure from the first passage and the hydraulic pressure from the second passage at both axial ends; A switching valve that moves due to a pressure difference between the first pressure receiving surface and the second pressure receiving surface and switches between communication and blocking between the first passage and the fourth passage and switching between communication and blocking between the second passage and the fourth passage. A power steering apparatus comprising:

  Since it is not necessary to provide pressure control means in each of the first passage and the second passage, the cost of the apparatus can be reduced. Further, since the only communication path that communicates the third path and the pressure control means is the fourth path, the hydraulic circuit can be simplified.

(E) In the power steering apparatus described in (d) above,
The power steering device, wherein the pressure control means is a pressure relief valve.

  When the hydraulic pressure in the apparatus becomes equal to or higher than a predetermined value, the pressure can be reduced by the pressure relief valve, so that failure of the apparatus can be avoided.

(F) In the power steering device described in (d) above,
The power steering device, wherein the pressure control means is an accumulator.

  The fluid pressure fluctuation in the apparatus can be absorbed by the accumulator. In particular, since the pulsation of the discharge pressure of the pump is generated in the pressure side oil passage, the pulsation due to the pump can be reduced by controlling the switching valve so as to communicate the pressure side oil passage and the accumulator.

(G) In the power steering apparatus described in (d) above,
The switching valve includes a pair of urging means at both ends of a valve body.

  The pair of urging means urges the valve body to maintain the axial position of the valve body at the neutral position. Therefore, in a state where no hydraulic pressure is applied to the valve body, the pressure balance between the first passage and the second passage can be maintained.

(H) In the power steering device described in (d) above,
A first locking portion and a second locking portion provided on both sides in the axial direction of the switching valve, and a third passage provided between the switching valve and the first locking portion. 1. A power steering apparatus, further comprising: a first seal member; and a second seal member provided between the switching valve and the second locking portion.

  By providing the first (second) seal member between the switching valve and the first locking portion (or the second locking portion), the switching valve and the locking portion sandwich the seal member, The sealing performance of the passage can be improved.

(L) In the power steering apparatus described in (D) above,
The power steering device, wherein the third passage and the switching valve have a circular cross section.

  The third passage can be formed by drilling.

(Nu) In the power steering apparatus described in (d) above,
The power steering device further comprising a first cushioning material and a second cushioning material provided on both sides in the axial direction of the switching valve in the third passage.

  When the switching valve moves due to the hydraulic pressure from the first passage or the second passage, the collision noise of the switching valve can be suppressed by contacting the buffer member.

(Le) In the power steering device described in (d) above,
When the first passage and the fourth passage communicate with each other, the second passage communicates with the low pressure side, and when the second passage and the fourth passage communicate with each other, the first passage communicates with the low pressure side. A power steering device.

  When one side in the axial direction of the switching valve is at high pressure, the operability of the switching valve can be improved by communicating the other side with the low pressure side.

(W) In the power steering device described in (L) above,
The power steering apparatus according to claim 1, wherein the low-pressure side is a reservoir tank.

  The hydraulic oil pushed out by the movement of the switching valve can be discharged to the reservoir tank.

It is a system configuration diagram of a power steering device to which the present power steering device is applied. FIG. 3 is a hydraulic circuit diagram when hydraulic oil is charged in the first embodiment. It is a hydraulic circuit figure at the time of hydraulic oil filling in a prior art. It is a schematic diagram which shows the flow of hydraulic oil and air when the volume of a 1st cylinder chamber reduces. It is a schematic diagram which shows the flow of hydraulic oil and air when the volume of a 2nd cylinder chamber reduces. FIG. 6 is a hydraulic circuit diagram when the pump is not operated in the third embodiment. FIG. 10 is a hydraulic circuit diagram when a second cylinder chamber is pressurized in the third embodiment. FIG. 6 is a hydraulic circuit diagram at the time of pressurization of a first cylinder chamber in Embodiment 3. 6 is a sectional view of a switching valve in Embodiment 3. FIG. It is sectional drawing of a switching valve in the case of connecting a switching valve and a pressure relief valve by two passages. FIG. 10 is a hydraulic circuit diagram when the pump is not operated in the fourth embodiment. FIG. 10 is a hydraulic circuit diagram when a second cylinder chamber is pressurized in the fourth embodiment. FIG. 6 is a hydraulic circuit diagram when a first cylinder chamber is pressurized in Embodiment 4.

Explanation of symbols

1 Pump 2 Steering Wheel 3 Shaft 4 Pinion 5 Rack Shaft 6 Torque Sensor 7 Control Unit 8 Cylinder Chamber 9 Reservoir Tanks 21 and 22 First and Second Passages 24 Fourth Passage 27 Connections 31 to 34 First to Fourth Check Valves 35 Return passage check valve 40 Electromagnetic switching valve 50 Spool valve 60 Return passages 81 and 82 First and second cylinder chambers 83 Piston 100 Switching valve 101 Housing 110 Third passage 111 Valve body housing portion 112 Valve seat housing portion 120 Valve body 121 , 122 First and second pressure receiving surfaces 130 Valve seat 131 Opening portion 132 Bottom portion 133 Outer cylindrical portion 134 Radial through hole 135 Inner peripheral portion 140 Spring 150 to 180 First to fourth oil chambers 200 Pressure relief valve 300 Accumulator M Motor

Claims (2)

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;
A motor for rotating the reversible pump forward and backward, and
Steering load detection means for detecting or estimating a steering load of a steering wheel for steering control of the steered wheels;
A reservoir tank for storing hydraulic oil;
A first one-way valve provided in the first passage and allowing only a flow of hydraulic oil from the reservoir tank side to the first passage side;
A second one-way valve provided in the second passage and allowing only the flow of hydraulic oil from the reservoir tank side to the second passage side;
A third one-way valve provided in the first passage and allowing only the flow of hydraulic oil from the first passage side to the reservoir tank side;
A fourth one-way valve provided in the second passage and allowing only a flow of hydraulic oil from the second passage side to the reservoir tank side;
And a pump control means for rotating the reversible pump in a direction to supply the hydraulic oil to the pressure chamber on the side where the volume of the reversible pump is stopped or reduced in volume when performing the hydraulic oil filling operation. The power steering apparatus according to claim 1, wherein
The hydraulic power cylinder is divided into two left and right cylinder chambers by a piston,
The first step of reducing the volume of the left cylinder chamber and increasing the volume of the right cylinder chamber by moving the piston to the left, and the volume of the right cylinder chamber by moving the piston to the right The power steering device is characterized in that the hydraulic oil is charged by alternately repeating the second step of decreasing and increasing the volume of the left cylinder chamber.

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