JP3909220B2 - Power steering device for vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle power steering device, and more particularly to a vehicle power steering device having an improved structure of a hydraulic passage for supplying and discharging hydraulic pressure to and from a power cylinder.
[0002]
[Prior art]
As this type of power steering device, for example, one described in Japanese Patent Application Laid-Open No. 59-118569 is known.
[0003]
The outline thereof will be described with reference to FIG. 6. A steering shaft 2 having a steering wheel 1 attached to the upper end, an output shaft 3 connected to the steering shaft 2 via a torsion spring (not shown), and the output shaft. 3, a rack 4 a and a pinion 4 b provided at the lower end, a rack 4 a formed at one end of the piston rod 5, a power cylinder 6 operated by hydraulic pressure, and a reversible hydraulic pump 8 operated by a motor 7, The first passage 12a and the second passage 12b connecting the two ports 9a and 9b of the hydraulic pump 8 to the first working chamber 11a and the second working chamber 11b in the power cylinder 6 separated by the piston 10; A torque detection mechanism 13 for detecting a steering torque from a torsion angle of a torsion spring between the steering shaft 2 and the output shaft 3, and a detection signal of the torque detection mechanism 13. And a controller 14 for controlling the rotational direction and the discharge pressure of the hydraulic pump 8 based on. Reference numeral 15 denotes a bypass passage that bypasses the hydraulic pump 8 to connect the first working chamber 11a and the second working chamber 11b of the power cylinder 6, and 16 is a bypass passage 15 when the steering torque is equal to or less than a predetermined value. Is an electromagnetic switching valve that closes the bypass passage 15 when the steering torque exceeds a predetermined value.
[0004]
Since the power steering device is configured as described above, when the steering wheel 1 is steered while the vehicle is running, the controller 14 controls the hydraulic pump 8 according to the torque detected by the torque detection mechanism 13 at that time. An assist force is applied to the steering mechanism by controlling the rotation direction and the discharge pressure, thereby relatively supplying a hydraulic pressure corresponding to the torque to each of the working chambers 11a and 11b.
[Problems to be solved by the invention]
However, in this conventional power steering device, the hydraulic pump 8 that is a hydraulic source and the working chambers 11a and 11b of the power cylinder 6 are in direct communication with each other. When the reaction force from the road surface and the pressure of the power cylinder 6 are substantially balanced and the hydraulic pump 8 rotates at a low speed so as to compensate for the leakage, the discharge pulsation of the hydraulic pump 8 is generated as shown in FIG. The vibration is transmitted to the power cylinder 6 as it is, and the vibration of the power cylinder 6 due to the pulsation may be input to the steering 1 to deteriorate the steering feeling.
[0006]
Accordingly, the present invention is intended to provide a power steering apparatus for a vehicle that can eliminate the vibration of the power cylinder caused by the pulsation of the hydraulic power source and can improve the steering feeling.
[0007]
[Means for Solving the Problems]
As means for solving the above-described problems, the present invention includes a power cylinder that applies hydraulic assist force to a steering mechanism, a reversible hydraulic pump that selectively supplies hydraulic oil to the power cylinder, and the reversible In a vehicle power steering apparatus comprising a first passage and a second passage for connecting two intake / exhaust ports of a hydraulic pump of a type to a first working chamber and a second working chamber in the power cylinder separated by a piston A discharge valve that opens when the pressure on the reversible hydraulic pump side exceeds the set pressure on the working chamber side, and hydraulic oil from the working chamber side to the reversible hydraulic pump. A one-way valve that allows only inflow of the first passage and the second passage in parallel, and the valve opening pressure of the discharge valve is set larger than the valve opening pressure of the one-way valve. The reversible hydraulic port It is characterized by reducing the pulse pressure variation of the flop.
[0008]
In this invention, since each working chamber from reversible hydraulic pump, provided with a discharge valve the pressure of reversible hydraulic pump side is only opened when the increased set pressure than the pressure of the working chamber side When the discharge valve is opened, the pressure on the reversible hydraulic pump side is higher than the pressure on the working chamber side by the valve opening pressure of the discharge valve. Therefore, activated when the pressure of the reversible side of the hydraulic pump is decreased from this state until the pressure of the hydraulic pump side of the reversible type is reduced by the opening pressure of the discharge valve includes a hydraulic pump side of the reversible The one-way valve opens only after the pressure of the discharge valve is reduced by the valve opening pressure, and the hydraulic oil is returned from the working chamber to the reversible hydraulic pump side. Therefore, when varying the pressure of the reversible hydraulic pump side by the discharge pulsation of the reversible hydraulic pump can dead zone of the valve-opening pressure of the discharge valve to the low pressure side from the peak pressure variation of the fluid pressure actuated It becomes difficult to be transmitted to the room side.
[0009]
The valve opening pressure of the discharge valve is preferably set to be larger than the pulse pressure fluctuation range of the reversible hydraulic pump . In this case, since the width of the dead zone becomes larger than the pulsation fluctuation range of the pressure source, the pulsation on the reversible hydraulic pump side is not transmitted to the working chamber side at all.
[0010]
Further, it is desirable that the valve opening pressure of the discharge valve is set by a spring force of a spring member that urges the valve body of the discharge valve in the closing direction.
Further, the reversible hydraulic pump is preferably driven by a motor.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, a first embodiment and a second embodiment of the present invention will be described with reference to FIGS.
[0012]
FIG. 1 shows an overall schematic configuration of a power steering device according to a first embodiment. As shown in FIG. 1, the power steering device according to this embodiment includes a steering shaft 21 having a steering wheel 20 connected to an upper end portion. An output shaft 22 connected to the steering shaft 21, a rack 23 and a pinion 24 provided at the lower end of the output shaft 22 to form a steering mechanism, and a steering wheel 20 provided near the lower end of the output shaft 22. A detection means 26 for detecting torque and road surface input from the steering wheels 25a, 25b, a power cylinder 27 linked to the rack 23, and a hydraulic circuit 28 for supplying and discharging hydraulic pressure to the power cylinder 27 are provided. In the power cylinder 27, a piston rod 30 connected to the rack 23 passes through a cylindrical cylinder portion 29 extending in the vehicle body width direction. Rutotomoni, piston 31 slides is fixed a cylindrical cylinder portion 29 to the piston rod 30. In addition, the inside of the cylinder portion 29 is divided into a left and right first working chamber 32 a and a second working chamber 32 b by a piston 31.
[0013]
The hydraulic circuit 28 includes a reversible hydraulic pump 34 driven by a motor 33, a first passage 36a connecting one port 35a of the hydraulic pump 34 and the first working chamber 32a, and the other of the hydraulic pump 34. A second passage 36b for connecting the port 35b to the second working chamber 32b, and a reservoir 37 for replenishing insufficient hydraulic oil in the circuit through the hydraulic pump 34. The first passage 36a and the second passage A supply path 38 and a discharge path 39 are provided in parallel in 36b, respectively, and a discharge valve 40 and a one-way valve 41, which will be described later, are interposed in the supply path 38 and the discharge path 39, respectively. The motor 33 that drives the hydraulic pump 34 is controlled by a controller 42, and a signal from the detection means 26 is input to the controller 42. In this embodiment, the hydraulic source is constituted by a motor 33, a hydraulic pump 34, and the like.
[0014]
The discharge valve 40 opens the supply passage 38 when the pressure on the hydraulic pump 34 side becomes equal to or higher than a set valve opening pressure larger than the pressure on the working chamber 32a (or 32b) side, and the one-way valve 41 is in the working chamber 32a ( Alternatively, the inflow of hydraulic oil from the 32b) side to the hydraulic pump 34 side is always allowed. Specifically, the discharge valve 40 and the one-way valve 41 are close to and away from the valve body 45 having a passage hole 43 and a conical valve seat 44, as shown in FIGS. A spherical valve body 46 that opens and closes the passage hole 43 and a frame-like retainer 47 that accommodates the valve body 46 are provided, and the valve body 46 is attached to the valve seat 44 with a predetermined force only on the retainer 47 side on the discharge valve 40 side. A spring 48 that is a spring member that biases in the direction (the valve closing direction) is accommodated.
[0015]
Here, the valve opening pressure P _s of the discharge valve 40, can be arbitrarily changed by the setting adjustment of the spring stiffness of the spring 48, in this first embodiment, the valve opening pressure P _s is 4 It is set to a value slightly smaller than the pulse pressure variation width P _a of the hydraulic pump 34 as shown in.
[0016]
In the above configuration, when the steering wheel 1 is operated, the steering torque and road surface input of the steering wheel 1 at that time are detected by the detection means 26, and the controller 42 drives and rotates the motor 33 based on this detection signal. The torque is controlled, thereby adjusting the operating pressure of the power cylinder 27. As a result, the steering wheel receives an assist force corresponding to the steering condition from the power cylinder 27 and is steered by an angle corresponding to the operation of the steering wheel 1.
[0017]
When the reaction force from the road surface input to the power cylinder 1 and the operating pressure of the power cylinder 1 are balanced, such as when the vehicle is traveling while maintaining a constant steering angle, the hydraulic pump 34 Operates continuously or intermittently at low speed to compensate for leaks. Under such conditions, the discharge pulsation of the hydraulic pump 34 is easily transmitted to the working chamber 32a (32b) through the passage 36a (36b). In the case of this power steering apparatus, the hydraulic pump is provided in each passage 36a (36b). After the pressure on the 34 side rises, the pressure on the hydraulic pump 34 side becomes higher than the pressure on the working chamber 32a (32b) side by the opening pressure of the discharge valve 40 as shown in FIG. The pulsation is hardly transmitted to the side 32b).
[0018]
That is, once the pressure on the hydraulic pump 34 reaches the peak value of the pulsation, the pressure on the hydraulic pump 34 side is the working chamber until the pressure drops from the peak value by the valve opening pressure P _s of the discharge valve 40. It is higher than the pressure on the 32a (32b) side. Therefore, a dead zone corresponding to the valve opening pressure P _s of the discharge valve 40 is created at this time, and the one-way valve 41 is opened as long as the hydraulic pressure is in this dead zone, and the hydraulic oil is moved from the working chamber 32a (32b) side to the hydraulic pump 34 side. Will not flow. Accordingly, the pressure on the working chamber 32a (32b) side is maintained at a constant pressure at this time.
[0019]
However, when the pressure on the hydraulic pump 34 side decreases from the peak value to the valve opening pressure P _s or more of the discharge valve 40 (out of the dead zone), the pressure on the working chamber 32a (32b) side is higher than the pressure on the hydraulic pump 34 side. Therefore, the one-way valve 41 opens and hydraulic oil flows out from the working chamber 32a (32b) to the hydraulic pump 34, and the pressure on the working chamber 32a (32b) decreases with the pulsation on the hydraulic pump 34. . When the pressure of the hydraulic pump 34 side is increased again, the pressure in the working chamber 32a (32 b) side is increased to lower the pressure only valve opening pressure P _s content with respect to the peak value, where it is maintained at a constant pressure.
[0020]
The power steering apparatus of this embodiment, it is possible to cut off most of the components of the pulsation of the hydraulic pump 34 side about to be transmitted in this way the working chamber 32a (32 b) side, the hydraulic pressure in the power cylinder 27 The vibration caused by the pulsation on the pump 34 side hardly occurs, and the steering feeling is not lowered.
[0021]
FIG. 5 shows the hydraulic characteristics on the hydraulic pump side and the working chamber side in the second embodiment of the present invention. The basic structure of the power steering apparatus of this embodiment is the first embodiment. When is substantially similar, except that differs by greater than pulse pressure variation width P _a of the hydraulic pump valve opening pressure P _s of the discharge valve.
[0022]
Therefore, in this embodiment, the dead zone does not operate the one-way valve is larger than the pulse pressure variation width P _a of the hydraulic pump side, the pressure of the working chamber side is not completely under the influence of pulsation. Therefore, in this embodiment, it is possible to completely eliminate the deterioration of the steering feeling due to the pulsation of the hydraulic pump.
[0023]
【The invention's effect】
As described above, according to the present invention, the pressure on the reversible hydraulic pump side changes from increasing to decreasing by providing the discharge valve and the one-way valve in parallel in the passage connecting the reversible hydraulic pump and each working chamber. Since a dead zone corresponding to the valve opening pressure of the discharge valve is created at this time, the pulsation of the reversible hydraulic pump is not transmitted to the working chamber side at least in the pressure width range corresponding to the valve opening pressure of the discharge valve. Therefore, according to the present invention, it is possible to improve the steering feeling by preventing the vibration of the power cylinder caused by the pulse pressure of the reversible hydraulic pump .
[0024]
Further, the valve opening pressure of the discharge valve, when larger than the pulse pressure variation width of the reversible hydraulic pump, completely eliminate the pulsations of the hydraulic pump side of the reversible is transmitted to the working chamber side Thus, the steering feeling can be improved more reliably.
[0025]
Furthermore, when the valve opening pressure of the discharge valve is set by the spring force of the spring member that urges the valve body of the discharge valve in the valve closing direction, it can be opened arbitrarily by changing the spring rigidity of the spring member. The valve pressure can be easily set.
[Brief description of the drawings]
FIG. 1 is an overall schematic configuration diagram showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a discharge valve showing the same embodiment.
FIG. 3 is a cross-sectional view of a one-way valve showing the embodiment.
FIG. 4 is a view showing pressure characteristics on the hydraulic pump side and the working chamber side of the embodiment.
FIG. 5 is a diagram showing pressure characteristics on a hydraulic pump side and a working chamber side according to another embodiment of the present invention.
FIG. 6 is an overall schematic configuration diagram showing a conventional technique.
FIG. 7 is a view showing pressure characteristics on the hydraulic pump side and the working chamber side showing the technique.
[Explanation of symbols]
27 ... Power cylinder 31 ... Piston 32a ... First working chamber 32b ... Second working chamber 34 ... Hydraulic pump 36a ... First passage 36b ... Second passage 40 ... Discharge valve 41 ... One-way valve

Claims (4)

A power cylinder that applies hydraulic assist force to the steering mechanism;
A reversible hydraulic pump that selectively supplies hydraulic oil to the power cylinder;
A power steering for a vehicle comprising a first passage and a second passage for connecting two intake / exhaust ports of the reversible hydraulic pump to a first working chamber and a second working chamber in the power cylinder separated by a piston. In the device
A discharge valve that opens when the pressure on the reversible hydraulic pump side exceeds the set pressure on the working chamber side, and the hydraulic fluid from the working chamber side to the reversible hydraulic pump. A one-way valve allowing only inflow is provided in parallel in each of the first passage and the second passage;
A vehicular power steering apparatus, wherein a valve opening pressure of the discharge valve is set larger than a valve opening pressure of the one-way valve to reduce a pulse pressure fluctuation of the reversible hydraulic pump . 2. The vehicle power steering apparatus according to claim 1, wherein a valve opening pressure of the discharge valve is set to be larger than a pulse pressure fluctuation range of the reversible hydraulic pump .   2. The vehicle power steering apparatus according to claim 1, wherein the valve opening pressure of the discharge valve is set by a spring force of a spring member that urges the valve body of the discharge valve in the valve closing direction.   The vehicular power steering apparatus according to claim 1, wherein the reversible hydraulic pump is driven by a motor.

Images