JPH0740850A - Hydraulic control valve for power steering device - Google Patents

Abstract

PURPOSE:To constitute a hydraulic control valve capable of changing a rising gradient of output to steering force according to electrification current in a power steering device having a hydraulic reaction force mechanism capable of changing an output characteristic to steering force by a controller. CONSTITUTION:A pain of variable orifices 3a and 3c wherein the opening areas of them are changed according to the output of an electric actuator 2 are provided in series and they are connected between the upstream and downstream of an output hydraulic control valve and also reaction force control pressure between them is led to a hydraulic reaction force mechanism. Moreover a reaction force control pressure restricting means is provided wherein the increase of reaction force control pressure is restrained when the reaction force control pressure becomes to a giving value or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a power steering device mainly used in vehicles such as automobiles.

[0002]

2. Description of the Related Art FIG. 1 shows the basic construction of an apparatus according to the present invention. Working oil discharged from an oil pump is guided to an output hydraulic control valve, where it flows into a power cylinder in response to steering, and The remaining hydraulic oil is returned to the oil reservoir and circulates. On the other hand, a part of the hydraulic oil discharged from the oil pump is guided to the reaction force control valve to control the hydraulic pressure that acts on the hydraulic reaction force mechanism provided in the output hydraulic pressure control valve section, and the surplus flow to the oil reservoir. I'm back. The reaction force control valve has a structure in which its control pressure can be changed by an electric actuator, and is controlled by a controller based on information from various sensors such as vehicle speed so that an optimum steering force characteristic can be obtained. Conventionally, a device of this type has been devised as shown in, for example, Japanese Utility Model Application No. 46-61598, and the structure of the reaction force control valve is shown in FIG. 2 and its operation is outlined below. In FIG. 2, Ps is an oil pump discharge pressure, Pf is a reaction force control pressure, and the port 7c is a return oil passage. Ps becomes the reaction force control pressure Pf via the port 8a, the variable throttle 17, and the port 8b, and is further connected to the return oil passage via the fixed throttle 18. On the other hand, the main spool 8 is provided with a pressure receiving surface 20, and when Pf becomes larger than a predetermined value, the main spool 8 is moved to the left in the figure and the variable throttle 17 is throttled to increase Pf. Restrict. On the other hand, the sub spool 11
Since the opening of the variable throttle 17 can be adjusted according to the current of the solenoid 15, it is possible to change the pressure that limits the Pf according to the solenoid current. FIG. 3 shows how the reaction force control pressure changes at this time. As described above, the reaction force control pressure changes according to the solenoid currents I1 to I4, but it is well understood that the pressure gradient from the rising to the time when the reaction force is limited does not change. Also,
FIG. 4 illustrates the steering force and output characteristics of the conventional device having the reaction force control pressure characteristic. Especially solenoid currents I2 to I4
In this case, when the steering force reaches a predetermined value, the output suddenly increases,
At the same time as you can see clearly that the increase in steering force is suppressed,
It also shows that the output gradient from the rise of the output to this steering force suppression point is constant regardless of the change in the solenoid current.

[0003]

The conventional device shown in FIG. 2 has a drawback in that the steering force suddenly changes at the point where the reaction force is suppressed, which gives an operator an uncomfortable feeling. Therefore, in the present invention, as shown in FIG. 5, the output can be changed according to the change of the solenoid current, and the output characteristic is convex downward even in the range from the rising to the point where the steering force is suppressed, and the output with respect to the steering force is changed. It is intended to be configured so that the gradient can be changed.

[0004]

In order to solve the problems, the present invention proposes a reaction force control valve having the following basic structure. (1) A pair of variable orifices whose opening area changes according to the output of the electric actuator are provided in series, and the variable orifices are connected between the upstream and downstream oil passages of the output hydraulic control valve. The reaction force control pressure between the variable orifices is guided to the hydraulic reaction mechanism. (2) The pair of variable orifices is configured such that when one increases (or decreases) its opening area, the other decreases (or increases) its opening area. (3) The reaction force control pressure is provided with a reaction force control pressure limiting unit that suppresses the increase when the reaction force control pressure is equal to or higher than a predetermined value.

[0005]

The operation of the reaction force control valve having the above-mentioned basic structure will be outlined below. (1) When pressure is generated upstream of the output hydraulic pressure control valve by steering, this pressure is also applied to the pair of variable orifices, so reaction force control is performed according to the open area ratio of the upstream and downstream variable orifices. Pressure is generated between the variable orifices,
Moreover, if the output hydraulic pressure increases, the reaction force control pressure also increases proportionally. (2) Since the opening area ratio of the variable orifice is determined according to the output of the electric actuator driven by the controller whose output current is controlled by the signal such as the vehicle speed, the rising pressure gradient of the reaction force control pressure is determined. Can be changed by the controller currents I1 to I4 as shown in FIG. (3) When the reaction force control pressure exceeds a predetermined value, the reaction force is fed back to the control valve to displace the valve body in a direction to suppress the increase in control pressure, or by using a relief valve, the reaction force It controls the control pressure to prevent the steering force from becoming excessively large.

[0006]

[Embodiment] Next, an embodiment according to the present invention will be described with reference to FIGS. FIG. 7 shows a first embodiment of the present invention. The housing 1 includes a supply port 1a, a control pressure port 1b,
The return port 1c is provided, and the variable orifice 3a.3 is provided by the sleeve 3 fitted in the housing 1 and the spool 4 set so as to be able to slide smoothly in the sleeve.
c is configured. The variable orifice is composed of a plurality of ports having different positions, and the opening area can be gradually changed according to the stroke of the spool 4. The annular groove 12 is an oil passage connecting the variable orifices and communicates with the control pressure port 1b via the port 3b. The annular grooves 11 and 13 are the seals 20, 21 and 22.
It is kept liquid tight by. In FIG. 7, the electric actuator 2 is composed of a stepping motor, and the output shaft 2a
Is controlled by the controller. Output shaft 2a
Is screw-engaged with the spool 4, and the pin 2b fixed to the main body of the stepping motor 2 is fitted with a hole 4d provided in the spool 4 with a clearance, so that the spool 2 rotates as the output shaft 2a rotates. Reference numeral 4 has a basic function of sliding in the axial direction and changing the opening area of the variable orifices 3a and 3c.

When the output pressure of the oil pump increases due to the action of the output hydraulic pressure control valve, the discharge pressure of the oil pump is guided to the supply port 1a, so that the variable orifices 3a and 3c.
The control pressure of the annular groove 12 also increases in accordance with the opening area ratio. This control pressure is guided to the ball 19 forming the relief valve via the oil passage 4c, but if the control pressure is below a predetermined value, the relief valve does not operate. On the other hand, when the control pressure exceeds the predetermined value, the ball 19 is displaced to the right in FIG. 7, and the return port 1 is moved through the oil passage 16a and the chamber 1d.
Since the hydraulic oil flows into the c, it has a structure that exerts the function of a relief valve that suppresses an increase in the control pressure of the annular groove 12. Here, 1e and 3d are oil passages for communicating the chamber 1d and the chamber 14, and 23 is a seal.
6 and 18 are spring seats, and 17 is a relief spring.

FIG. 8 shows a second embodiment of the present invention. First
The point basically different from the embodiment is that the electric actuator 2 is composed of a solenoid valve. According to the current from the controller, the output shaft 2a pushes the spool 4 to the right in FIG. On the other hand, since the reaction spring 5 is interposed between the other end of the spool 4 and the adjusting screw 15 screwed to the housing 1, as a result, the spool 4
Causes a predetermined displacement according to the electric current, so that the opening areas of the variable orifices 3a and 3c can be gradually changed and the pressure introduced to the reaction means can be controlled as in the first embodiment. Adjustment screws are provided to suppress individual characteristic variations with respect to desired characteristics, and 24 indicates a seal. The operation of the relief valve is exactly the same as that of the first embodiment.

FIG. 9 shows a third embodiment of the present invention. The displacement of the spool 4 and the control pressure are determined by the balance between the output of the output shaft 2a of the electric actuator (solenoid valve) 2 and the reaction force of the reaction force spring 5, which is the same as the second embodiment. The difference from the above embodiment is that the control pressure is suppressed by the acting force of the reaction force pin without using the relief valve. In FIG. 9, the spring seat 7 is fitted so that the small diameter portion of the spool 4 can slide smoothly in the axial direction. On the other hand, the spring seat 9 has a snap ring 10
Is fitted so as to prevent the axial movement thereof, and a reaction force spring 8 is incorporated between the spring seats 7 and 9 with a precompression. Further, a reaction force pin 6 is incorporated in a hole 4a provided in the spool 4 so as to be able to slide smoothly in the axial direction with a slight clearance, and one end of the reaction force pin 6 abuts on the spring seat 7. In addition, the control pressure of the chamber 12 acts on the other end.

Further, the outer diameter portion of the spring seat 7 formed in a cylindrical shape extends toward the solenoid valve while bearing the outer diameter portion of the spring seat 9 and when the output shaft 2a moves to the leftmost side in FIG. In addition, one end surface of the spring seat 7 is configured to contact the solenoid valve body. The operation of the control valve in such a configuration is as follows. (1) When an output load is applied to the output shaft 2a by energizing the solenoid valve, the spool 4 is displaced to the right by Xmm in FIG. 9, for example. At this time, assuming that the axial maximum end face distance between the spool 4 and the spring seat 7 is Lmm, the length L at this point does not change before and after the Xmm displacement. At this time, the gap between the end surface of the spring seat 7 and the solenoid valve body is X mm. (2) Then, when the control pressure rises and the axial force acting on the reaction force pin 6 by the control pressure exceeds the precompression load of the reaction force spring 8, the reaction force pin pushes the spring seat 7 to the left in FIG. To start, the gap between the end surface of the spring seat 7 and the solenoid valve body is reduced and becomes zero at a predetermined control pressure. At this time, the maximum distance between the end faces of the spool 4 and the spring seat 7 is L + X mm.
In this process, the displacement X of the spool 4 is kept at the initial value. (3) When the control pressure is further increased, the maximum distance between the end faces of the spool 4 and the spring seat 7 is L + due to the acting force of the reaction force pin 6.
Since it extends beyond Xmm, the displacement of spool 4 is Xmm
Over. As a result, the opening area of the variable orifice on the upstream side is reduced and the opening area of the variable orifice on the downstream side is increased, so that the control pressure is suppressed.

[0011]

According to the present invention, not only can the above-mentioned "problems to be solved by the invention" be rationally solved,
In addition, it also has the following various effects. (1) Since the control pressure between the pair of variable orifices is guided to the reaction force means, the steering force in the vicinity of neutral-output characteristics has a slightly downwardly convex curve, which is mechanically effective for a person who steers. The output characteristics are linear, resulting in a natural and linear steering feel. (2) Since the outer diameters of the spools that make up the variable orifices are the same, theoretically, the thrust in the spool axial direction is not generated by hydraulic pressure, the control characteristics are extremely stable, and even electric actuators with small output can be easily operated. It becomes possible to drive. (3) With the structure using the stepping motor as shown in the first embodiment, not only accurate displacement control is possible, but also a reaction force spring and an adjusting screw are unnecessary, so that a simple and rational control valve structure is obtained. can do. (4) By making the rate of change of the opening area of the upstream variable orifice smaller than the rate of change of the same on the downstream side, the control pressure characteristic with respect to the displacement of the spool can be made more linear. (Since the hydraulic pressure basically shows a secondary rising characteristic with respect to the spool stroke, if the upstream and downstream aperture area change rates are the same, the change in the control pressure with respect to the spool displacement will be biased.) 5) Since the control pressure is obtained by the pair of variable orifices, the load flow rate required for control can be minimized, and the system needs to increase the oil pump capacity.
Does not require any subsequent changes. Further, it is possible to make the flow rate through the orifice almost average in the spool stroke range other than when the variable orifice is fully closed, and it is possible to reduce the oil temperature dependence characteristic of the control characteristic. (6) Since the sleeve has a structure in which a variable orifice port can be machined, highly accurate machining such as port position is extremely easy, and the assembling property is also excellent. (7) The control valve structure in which the relief valve is provided in the spool is rational and compact, and the control pressure characteristic can be made to have very little valve operation hysteresis.

[0012]

[Brief description of drawings]

FIG. 1 is a basic circuit diagram of a hydraulic control valve according to the present invention.

FIG. 2 shows a conventional embodiment.

FIG. 3 shows pump discharge pressure-reaction force control pressure characteristics in a conventional example.

FIG. 4 shows steering force-output characteristics in a conventional example.

FIG. 5 shows steering force-output characteristics in the present invention.

FIG. 6 shows characteristics of pump discharge pressure to reaction force control pressure in the present invention.

FIG. 7 shows a first embodiment of the present invention.

FIG. 8 shows a second embodiment of the present invention.

FIG. 9 shows a third embodiment of the present invention.

[Explanation of symbols]

 1 Housing 1a Supply Port 1b Control Pressure Port 1c Return Port 1d Chamber 1e Communication Passage 2 Electric Actuator 2a Output Shaft 2b Pin 3 Sleeves 3a, 3c Variable Orifice 3b Port 3d Oil Path 4 Spool 4a Hole 4b, 4c Oil Path 4d Hole 5 Force spring 6 Reaction force pin 7 Spring seat 7a, 7b Communication passage 8 Reaction spring 9 Spring seat 10 Snap ring 11, 12, 13, Annular groove 14 Chamber 15 Adjustment screw 16 Spring seat 16a Communication passage 17 Relief spring 18 Spring seat 19 Ball 20,21,22 Seal 23,24 Seal

Claims (7)

[Claims] 1. A hydraulic power source, an output hydraulic pressure control means, an output means, a reaction force means for generating a reaction force with respect to a steering input according to the output hydraulic pressure, and an electronic device for electrically controlling the reaction force, which are used in an automobile or the like. In a power steering apparatus including control means and the like, a reaction force control valve that is driven by an electric actuator to control reaction force hydraulic pressure is provided with a supply port, a return port, and a control pressure port, and each of the ports is connected to the output hydraulic pressure control means. A pair of variable orifices, each of which has an opening area that changes depending on the valve displacement of the reaction force control valve, is provided between the supply port and the return port in communication with the upstream and downstream sides and the reaction force means. If the hole area increases (or decreases), the other decreases (or increases), and the oil passage connecting the variable orifices is connected to the control pressure port. Hydraulic control valve structure characterized. 2. A device provided between the supply port and the return port,
Of the pair of variable orifices whose opening areas change according to the displacement of the reaction force control valve, the rate of change of the opening area of the variable orifice on the upstream side is smaller than that of the variable orifice on the downstream side. The hydraulic control valve structure according to claim 1, wherein: 3. A device provided between the supply port and the return port,
The pair of variable orifices, each of which has an opening area that changes according to the displacement of the reaction force control valve, is constituted by a plurality of circular ports provided at a sleeve and having different positions, and a valve body. 1. The hydraulic control valve structure according to 1. 4. When the control pressure introduced to the reaction force means exceeds a predetermined value, the opening area of the variable orifice on the upstream side is reduced or the opening area of the variable orifice on the downstream side is increased to control the same. The hydraulic control valve structure according to claim 1, wherein the hydraulic control valve structure is configured to suppress an increase in pressure. 5. A valve body is fitted with a pre-compressed spring, a spring seat for supporting the spring, and a reaction force pin for applying a control pressure to the reaction force means to apply the acting force to the spring. 5. When the control pressure becomes equal to or higher than a predetermined value, the total force of the valve body including the spring seat changes due to the acting force on the reaction force pin.
The hydraulic control valve structure described in. 6. The hydraulic control valve structure according to claim 1, further comprising a relief valve that relieves the control pressure when the control pressure introduced to the reaction force means exceeds a predetermined value. 7. A spring pre-compressed, a valve provided at one end of the spring, and a valve seat capable of maintaining a liquid-tight state by contacting the valve with each other. The hydraulic control valve structure according to claim 6, wherein the hydraulic control valve structure is configured in a valve body of the force control valve.