JPS6382877A - Control valve for power steering device - Google Patents

Abstract

PURPOSE:To avoid a danger that steering becomes abruptly heavier on sudden steering at high speed by making a restriction whose opening degree is controlled by a factor other than steering load change opening degrees of the other restrictions. CONSTITUTION:A control valve has a first system 11 and a second system 12 through which hydraulic fluid from a pump 10 flows divergently, and a power cylinder 13 has chambers 13a, 13b which are respectively connected to the first system 11 and the second system 12 connected in parallel to each other. There are provided in the systems and passages connecting the systems first restrictions 1a, 1b, second restrictions 2a, 2b, third restrictions 3a, 3b, fourth restrictions 4a, 4b and fifth restrictions 5a, 5b. The first, second, third and fourth restrictions have opening degrees which can be reduced in accordance with steering load during the steering. The opening degree of the fifth restrictions is controlled by a factor other than steering load, such as traveling speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control valve for a power steering device.

(Prior art) A power steering link device enables power assist in the steering direction and light power steering by making a power cylinder respond to the assist pressure generated by a control valve according to the steering load. It is.

For this purpose, the control valve is provided with a first system and a second system through which the working fluid from the pump is diverted, to which two chambers of the power cylinder are respectively connected, and the control valve is located upstream from the power cylinder connection point of the first system. and a first throttle whose opening degree decreases according to the unidirectional steering load, downstream from the power cylinder connection point of the second system, and a first throttle, which decreases the opening depending on the unidirectional steering load, and a first throttle connected to the power cylinder connection point of the second system, and upstream of the power cylinder connection point of the second system. It is common to have a configuration in which a second throttle is provided downstream of the point, the opening degree of which decreases depending on the steering load in the other direction.

However, in this case, the control valve has only one type of assist pressure change characteristic with respect to the dry steering load, and for example, the control valve has only one type of assist pressure change characteristic depending on the vehicle speed.

It does not match the required characteristics, which are said to be good if they change like b and c.

Therefore, in the past, flow control type power steering devices such as those described in the June 29, 1980 Society of Automotive Engineers of Japan ``Symposium on Recent Chassis Technology and Vehicle Dynamic Performance'', page 24 of the middle box, and those manufactured by Mitsubishi Motors Q@ A hydraulic reaction force control type power steering device employed in a gear run and a power steering system as disclosed in Japanese Patent Application Laid-open No. 139563/1983 have been proposed. Both of these are the 11th
The system meets the required characteristics shown in the figure, and enables stable steering by reducing the steering force when stationary and increasing the steering force as the vehicle speed increases.

(Problem to be Solved by the Invention) However, in a system that controls the steering force by increasing or decreasing the amount of working fluid supplied at a predetermined ratio corresponding to the vehicle speed, such as the above-mentioned flow rate control type, it is difficult to control the steering force at high vehicle speeds. If the amount of working fluid supplied is reduced in accordance with the required steering force, it is a problem that during sudden steering at high vehicle speeds, the amount of working fluid supplied becomes less than the required flow rate of the control valve, and the steering force suddenly becomes heavy. On the other hand, if the amount of working fluid supplied is increased in accordance with this required flow rate, the amount of working fluid supplied during stationary operation will increase excessively due to proportional control, and the capacity of the working fluid pump will increase. In this case, the amount of heat generated by the entire device increases, necessitating excessive heat countermeasures, and increasing costs.

In addition, in the hydraulic reaction force control type power steering link device, in addition to the control valve, there are parts that serve as the seventh purpose for the reaction force chamber and reaction force piston for generating hydraulic reaction force, and for controlling the reaction pressure. This requires a separate hydraulic switching valve, making the structure and piping system large and complicated, resulting in high costs and requiring a large space for the equipment.

Furthermore, the device disclosed in JP-A-61-139563 arranges two sets of control valves in parallel, and controls the characteristics of one valve independently of the steering human torque. Variable characteristics are achieved by changing and adding the opening degree of a variable throttle, and in order to provide two sets of control valves independently, the grooves of the rotary valve as a control valve are arranged in series in the axial direction. It is very difficult to process the grooves, especially the grooves provided on the inner diameter of the cylindrical valve body, and the number of processing steps increases. Furthermore, since the centers of the corresponding grooves of the groove groups constituting the two control valves must coincide, the two groove groups are required to have an accurate relative positional relationship in the circumferential direction. Processing costs will increase. Furthermore, as described above, since the two groups of grooves are arranged in series in the axial direction of the rotary valve, the axial dimension increases and the rotary valve becomes large.

(Means for Solving the Problems) The present invention proposes a control valve for a power steering device that can obtain the required characteristics without causing these problems. At least one of the fluid intake section and the working fluid outlet section is provided with a third throttle whose opening degree decreases in conjunction with the adjacent first throttle and a fourth throttle whose opening degree decreases in conjunction with the adjacent second throttle; It is characterized by a configuration in which the third diaphragm and the adjacent first diaphragm and the fourth diaphragm and the adjacent second diaphragm are connected by a fifth diaphragm whose opening is controlled by factors other than the steering load.

(Function) During one-way steering operation, the opening degree of the first throttle of the first system and the second system decreases according to the steering load. As a result, assist pressure is generated upstream of both box 1 throttles and is supplied to the corresponding chambers of the power cylinder, allowing the power cylinder to perform power steering by power assisting in the steering direction. 1st during other direction steering operation
The opening degree of the second throttle of the system and the second system decreases in accordance with the steering load. As a result, assist pressure is generated upstream of the two throttles in both boxes and supplied to the corresponding chambers of the power cylinder, and the power cylinder enables power steering by power assisting in the steering direction.

During one-way steering operation, the opening of the third throttle decreases in conjunction with the adjacent first throttle, and if the opening of the fifth throttle is controlled by a factor other than the steering load, the opening of the third throttle and the fifth throttle decrease. The assist pressure can be controlled with the characteristics determined by the composite equivalent opening, that is, by the above factors. During steering operation in the other direction, the opening of the fourth throttle decreases in conjunction with the adjacent second throttle, and if the opening of the fifth throttle is controlled using the above factors, the combined equivalent opening of the fourth and fifth throttle is The assist pressure can be controlled with determined characteristics, that is, with the above factors. By setting the above-mentioned factor to, for example, vehicle speed, it is possible to match the assist pressure to the required characteristics for each vehicle speed.

By the way, in order to obtain such required characteristics, we adopted a throttle opening control system using the fifth throttle whose opening is controlled only by the above factors, so even if the amount of working fluid supplied is small,
There is no danger that the working fluid supply volume will drop below the required volume during sudden steering at high vehicle speeds, causing the steering force to suddenly become heavier. In addition, a pump with a small discharge volume is sufficient, so noise and heat countermeasures are not required. In addition to being advantageous in terms of cost, the structure can be simplified and downsized.

(Example) Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 shows an embodiment of the control valve of the present invention as a fluid circuit.
system 12, the first system 11 and the second system are parallel to each other.
The system 12 includes chambers 13a and 13b of the power cylinder 13, respectively.
Connect.

A first throttle la whose opening degree decreases in accordance with the right steering load on the upstream side of the power cylinder connection point 11a of the first system 11 and on the downstream side of the power cylinder connection point 12a of the second system 12.
, lb. Further, second throttles 2a and 2b are provided upstream from the power cylinder connection point 12a of the second system 12 and downstream from the power cylinder connection point 11a of the first system 11, respectively, the opening of which decreases in accordance with the left steering load.

A third throttle 3 is provided in series with the first throttle 1b and a fourth throttle 4 is provided in series with the second throttle 2b at the working fluid outlet portions of the first system 11 and the second system 12. 1st aperture 1
It is assumed that the opening degree of the fourth diaphragm 4 decreases in conjunction with the second diaphragm 2b, and the opening degree of the fourth diaphragm 4 decreases in conjunction with the adjacent second diaphragm 2b. Also, between the third aperture 3 and the first aperture Ib, and between the fourth aperture 4 and the second aperture 2
The fifth aperture 5 communicates between the

As is clear from the above description, the opening degrees of the first apertures la, lb, the second apertures 2a, 2b, the third aperture 3, and the fourth aperture 4 are reduced according to the steering load during the steering operation using the steering wheel 14. However, the respective aperture opening change characteristics are determined as shown in FIG. In other words, the first aperture 1a and the second aperture
Although the directions of the steering loads are opposite to each other as shown in FIG. 2(a), the apertures 2a are designed to be fully closed with a relatively small steering load Tc, and the first aperture 1b and the second aperture 2b are respectively as shown in FIG. Although the direction of the steering load is reversed as shown in b), the steering load is completely closed with a relatively large steering load Tc', and the third aperture 3 and the fourth aperture 4 are used for steering as shown in FIG. Although the direction of the load is opposite, it is assumed that the steering load Tc' is larger than TC and smaller than TC'.

However, the fifth throttle 5 is affected by factors other than the steering load, for example, the first
The opening degree is controlled according to the vehicle speed in accordance with the required characteristics shown in FIG. 1, and as shown in FIG. 2(d), it is fully opened when the vehicle is stopped at zero speed, and the opening degree is increased as the vehicle speed increases.

The operation of the above embodiment will be explained next.

When the steering wheel 14 is not being steered, the working fluid from the pump 10 flows through the pump 10 because the opening degrees of the throttles la and 2a are the same, the opening degrees of the throttles Ib and 2b are the same, and the opening degrees of the throttle 3.4 are the same. The flow is equally divided into the first system 11 and the second system 12 and returned to the pump 10. Therefore, the power cylinder chamber 13a,
The inside of the steering wheel 13b is equally maintained in an unpressurized state, and a non-steering state can be maintained without generating any assist force.

If the steering wheel 14 is now steered to the right, the openings of the apertures la, lb, and 3 decrease in accordance with the characteristics shown in FIG. 2, and the apertures of the apertures 2a, 2b, and 4 increase. Thus the aperture l
Assist pressure is generated upstream of a and lb and is supplied to the power cylinder chamber 13b, and the assist pressure is supplied to the other power cylinder chamber 13a.
is kept under no pressure. As a result, the power cylinder provides power assist for the right steering, thereby enabling power steering.

Next, considering the assist pressure change characteristics, first of all, when the vehicle is stopped and the vehicle speed is 0, the throttle 5 is fully closed as is clear from FIG. 2(d).

At this time, the composite equivalent opening of the diaphragm 3.5 is equal to the opening S3 of the diaphragm 3 because the diaphragm 5 is fully closed, and the difference between this and the composite equivalent opening of the diaphragm 1b is 82, assuming that the opening of the diaphragm 1b is 82. , is expressed as .

To explain this theoretically, the pressure drop P due to the throttle 1b is
2 is the amount of working fluid passing through this, Q, and the specific gravity of the working fluid is ρ.
, if the acceleration of gravity is g, then P2=2・Q2/S2
2 g , and the pressure drop P3 due to the restriction 3 is expressed as ρ P3=-Q2/S3' g . Therefore, the pressure drop P due to both throttles 1b and 3
=P2+P, which shows that the above is true.

Finally, the composite equivalent opening S of this equation and the opening Sl of the aperture la is S+Sl since both are parallel. By the way, while driving, the aperture 5 changes as the vehicle speed increases (see Fig. 2).
Increase the opening degree S5 as shown in d). At this time, the composite equivalent opening S8 of the diaphragm 3.5 becomes SR=33+35, and the composite equivalent opening SA of this and the diaphragm 1b is expressed as follows. Therefore, the overall synthetic equivalent opening S is 5=SA +
It becomes S+.

As is clear from the comparison of equations (1) and (2), the composite equivalent opening S is larger when the vehicle is moving than when the vehicle is stopped, and as the vehicle speed increases, S5 increases and the composite equivalent opening S becomes larger. Therefore, the assist pressure characteristic during right steering is as shown in Fig. 11.
As shown in the quadrant, it decreases as the vehicle speed increases, and can match the required characteristics.

Note that when steering the steering wheel 14 to the left, the openings of the apertures 2a, 2b, and 4 are reduced according to the steering load, and in conjunction with the opening degree control of the aperture 5 according to the vehicle speed,
Power steering similar to the above-described right steering and assist pressure control as shown in the second quadrant of FIG. 11 are possible.

3 and 4 show a specific example in which the above embodiment is configured as a rotary type control valve for a rack and pinion type steering gear, and FIGS. A specific example of a spool-type control valve for use is shown below.

In the example shown in FIGS. 3 and 4, a torsion bar 21 is provided protruding from a pinion 20 that can steer the wheels by meshing with a rack (not shown) and stroking it in the longitudinal direction. An inner sleeve 23 of a control valve is loosely fitted into the torsion bar 21 with a gap 22, and the torsion bar 21 and the inner sleeve 23 are bolted together with a pin 24. Control valve outer sleeve 25
When fitted rotatably between the inner sleeve 23 and the valve body 26, it is coupled to the pinion 2o at a hinge 27. Inf IJ-bu 23 is steering wheel 1
4 (see FIG. 1) to input the steering force, and this steering force is transmitted to the pinion 2o through the version 21 to enable steering.

During such steering, the torsion bar 21 is twisted in accordance with the steering load to produce relative rotation in the steering direction between the sleeves 23 and 25, and the above-mentioned throttles la, lb, 2a.

2b, 3.4 (see FIG. 1) are provided between the two sleeves 23.25 as clearly shown in FIG.

In FIG. 4, solid line arrows indicate the rotation direction when steering to the right, and dotted line arrows indicate the rotation direction when steering to the left. In this example, the configuration includes three sets of the first system 11 and the second system I2 shown in FIG. 1. did. For this reason, three ports 25a for receiving the working fluid from the pump 10 are bored in the outer sleeve 25° at equal intervals in the circumferential direction, and three vertical ports 25a are bored on the outer periphery of the inner sleeve 23 to be located between these ports 25a. Grooves 23a are provided, and these vertical grooves pass through the gap 22 into the drain chamber 28 (see Figure 3).
This shall serve to return the working fluid to the pump IO.

The outer circumference of the inner sleeve 23 further includes adjacent vertical grooves 23.
A vertical groove 23b is provided between the vertical grooves 25a and 25a, and vertical grooves 23c are provided on both sides of the vertical groove 23b.

23d is provided. The inner periphery of the outer sleeve 25 includes a vertical groove 25b that overlaps the vertical grooves 23b and 23c in the circumferential direction to form apertures la and 2b;
The aperture 2a overlaps the diaphragm 23d in the circumferential direction,
A vertical groove 25C forming a diameter lb, and vertical grooves 25d and 25e overlapping in the circumferential direction with respect to adjacent vertical grooves 23a to form an aperture 3.4 are provided.

Each vertical groove 25b is connected to the power cylinder chamber 13a, and multiple vertical grooves 2
5G to the power cylinder chamber 13b, and each vertical groove 2
5d to one end of the aperture 5, and the multi-vertical grooves 25e to the other end of the aperture 5, the first system 11 and the second system in FIG.
This means that three sets of systems 11 have been formed.

The opening of the throttle 5 is increased by an electromagnetic force proportional to the drive current of the solenoid 29, and this current is controlled by the controller 3.
It is assumed that 0 increases as the vehicle speed increases. Thus, the opening degree of the throttle 5 increases as the vehicle speed increases, as shown in FIG. 2(d), and this specific example can also achieve the same effect as described above.

In this specific example, as shown in FIG. 4, the vertical grooves 25b to 25e formed on the inner circumference of the outer sleeve 25 are arranged so that the center surfaces in the groove width direction are adjacent to each other, and the longitudinal grooves 25b to 25e formed on the inner periphery of the outer sleeve 25 are located in the center of these surfaces, If configured so that they are parallel to the center plane passing through them, the adjacent vertical grooves 25t1.゛25e and 25C and 25d can be processed simultaneously with one cutter. In this case, even if the number of vertical grooves is large, the number of machining steps can be halved, and the machining accuracy of the vertical grooves can be improved since there is no shift in machining position between adjacent vertical grooves.

In addition, in the above-mentioned example, in order to specifically satisfy the requirements shown in FIG. 11, the opening of the fifth throttle 5 was controlled according to the vehicle speed.
Other controlling factors include the following:

(1) In conjunction with the wiper switch, as the wiper speed increases, that is, as the amount of rain increases, the solenoid drive current increases and the steering force becomes heavier, thereby preventing the danger associated with sudden steering in rainy weather.

(2) As the rotational difference between the driving wheels and non-driving wheels increases,
In other words, as the road surface becomes more slippery, the solenoid drive current is increased to increase the steering force, thereby preventing the danger associated with sudden steering on snowy or frozen roads.

(3) Allow the driver to freely select the solenoid drive current so that the steering force can be obtained according to the driver's preference.

(4) Determine the driving condition from the frequency of occurrence of vehicle body acceleration/deceleration,
This changes the aperture opening change characteristic shown in FIG. 2(d).

[5] Change the aperture opening change characteristic shown in FIG. 2(d) from the steering angle and steering angular velocity.

(6) The throttle opening change characteristic shown in FIG. 2(d) is changed according to the steered wheel (front wheel) load.

In the specific example of the spool-type control valve shown in FIGS. 5 and 6, the pinion 20 meshing with the rack 31 moves to the right in FIG. A spool 32 is provided which moves to the left in FIG. 6 in response to the steering load during left steering rotation, as indicated by a dotted line in FIG. , 2b,
3.4 is formed, and the working fluid from the pump 10 is supplied between the throttles la and 2a, and the return fluid from the control valve is returned to the pump 10 from between the throttles 3.4. or,
The space between the throttles la and 2b is connected to the power cylinder chamber 13a, the space between the throttles lb and 2a is connected to the power cylinder chamber 13b, the space between the throttles 1b and 3 is connected to one end of the throttle 5, and the space between the throttles 2a and 4 is connected to the other end of the throttle 5. Connect to.

As described above, a circuit similar to that shown in FIG. 1 is realized, and the same effect as described above can be achieved in this example as well.

FIG. 7 shows another example of the present invention, in which the third aperture 3 is provided upstream of the first aperture 1a of the first system 11, and the fourth aperture 4 is provided at the second aperture 2a of the second system 12. The fifth aperture 5 is provided on the upstream side, so that the fifth aperture 5 communicates between the apertures 1a and 3 and the apertures 2a and 4.

In this case, the opening change characteristics of the apertures la and 2a and the aperture 1b
.

The same effect can be obtained by reversing the opening degree change characteristics of 2b from those shown in FIGS. 2(a) and (b), as shown in FIGS. 8(a) and (b). However, the opening change characteristics of the apertures 3 and 4.5 are the same as in FIGS. 2(C) and 2(d).

FIG. 9 shows still another example of the present invention, in which the first system 1
1 and the working fluid port of the second system 12, the aperture 3 shown in FIG.
, 4.5 are provided with apertures 3a, 4a, and 5a corresponding to
At the working fluid outlet of the first system 11 and the second system 12 there are throttles 3b, 4b corresponding to the throttles 3.4.5 in FIG.

5b is provided.

In this case, the opening change characteristics of the apertures la, lb and 2a, 2b are the same as in Fig. 2(b) as shown in Fig. 10(a),
Aperture 3a.

The opening change characteristics of diaphragms 3b, 4a, and 4b are the same as in FIG. 2(C), as shown in FIG. ) can have the same effect.

(Effects of the Invention) Thus, as described above, the control valve of the present invention has the fifth throttle 5 (5a) whose opening degree is controlled by factors other than the steering load.
, 5b) and other apertures 3 (3a, 3b) or 4 (4a
, 4b), the composite equivalent opening degree is changed according to the above factors, so the required assist pressure characteristics according to the factors can be obtained by throttle opening control, and the conventional flow rate control type is not required. In comparison, even if the amount of working fluid supplied is small, there is no danger that the amount of working fluid supplied becomes less than the required amount and the steering force suddenly increases during sudden steering at high vehicle speeds, and Since the pump 10 only needs to have a small discharge volume, there is no need for noise or heat countermeasures, which is advantageous in terms of cost. Since there is no need for a hydraulic switching valve or the like for force control, it is possible to reduce costs, simplify the structure, and downsize. Furthermore, compared to the one disclosed in Japanese Patent Application Laid-Open No. 61-139563, variable steering force characteristics can be obtained with just one set of control valves, making it possible to reduce processing costs and downsize the control valve. be.

[Brief explanation of the drawing]

Fig. 1 is a fluid circuit diagram showing one embodiment of the control valve of the present invention, Fig. 2 (a) to (d) are characteristic diagrams of opening degree changes of various throttles in the same example, and Fig. 3 shows the same side as a rotor. Fig. 4 is a cross-sectional view taken along I'V-IV in Fig. 3, and Fig. 5 is a longitudinal cross-sectional view of a specific example configured as a spool-type control valve in the example shown in Fig. 1. 6 is a sectional view taken along Vl-0-■ in FIG. 5, FIG. 7 is a fluid circuit diagram showing another example of the present invention, and FIGS. Fig. 9 is a fluid circuit diagram showing still another example of the present invention;
Figures (a) to (C) are characteristic diagrams of opening degree changes of various throttles in the same example, and Figure 11 is a diagram illustrating ideal assist pressure control characteristics of the power steering device. la, lb...first aperture 2a, 2b...second
Throttle 3.3a, 3b...Third throttle 4.4a, 4b...Fourth throttle 5.5a, 5b -...Fifth throttle lO...Pump 11...First system 12...
・Second system 13...Power cylinder 14...Steering wheel Patent applicant Nissan Motor Co., Ltd. Representative Patent Attorney Hidetoshi Sugimura Akira Sugimura Patent Attorney Kosaku Sugimura Figure 2 (a), -b) (C ) (d) Figure 3 Figure 5 Figure 15 Figure 8 (a) (b) Figure 3 (, a)

Claims (1)

[Claims] 1.Equipped with a first system and a second system that separate the working fluid from the pump, two chambers of the power cylinder are connected to the first system and the second system, respectively, and the system is located upstream from the power cylinder connection point of the first system. and a first throttle whose opening degree decreases according to the unidirectional steering load, downstream from the power cylinder connection point of the second system, and a first throttle, which decreases the opening depending on the unidirectional steering load, and a first throttle connected to the power cylinder connection point of the second system, and upstream of the power cylinder connection point of the second system. In the control valve of the power steering device, the control valve of the power steering device is provided with a second throttle whose opening degree decreases according to the steering load in the other direction on the downstream side of the point, and the working fluid inlet and the working fluid outlet of the first and second systems are At least one of the third throttle openings decreases in conjunction with the first throttle.
A diaphragm is provided in series with the first diaphragm, and a fourth diaphragm whose opening degree decreases in conjunction with the second diaphragm is provided in series with the second diaphragm, and between these third diaphragms and the first diaphragm adjacent thereto. A control valve for a power steering device, characterized in that the fourth throttle and the second throttle adjacent thereto are connected through a fifth throttle whose opening is controlled by factors other than the steering load.