JPH04292265A - Steering force controller for power steering - Google Patents

Abstract

PURPOSE:To set a relationship between a valve operating angle and pressure in a power cylinder down to be linear as shown in the illustration, and also to make it possible the fabrication for that is easy. CONSTITUTION:A length L2 of a chamfering part 37 of each of second control parts 5-8 is longer than length L1 of a chamfering part 33 of each of first control parts 1-4. In addition, an underlap U2 of the second control part is made longer in full than an underlap U1 of the first control part. Moreover, each of third control parts 9, 10 is made so as to constitute a variable throttle 40 being overlapped at all times.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering force control device for controlling steering force in accordance with the steering angle of a steering wheel.

0002

2. Description of the Related Art In the conventional device shown in FIGS. 6 to 10, a pinion shaft 22 and a stub shaft 23 are coaxially inserted into a casing 21, and both shafts 22 and 23 are connected via a torsion bar 24. are connected.

[0003] The pinion shaft 22 has a pinion 2.
5, and this pinion 25 is engaged with a rack 27 formed on a rod 26 of the steering system. Therefore, when the pinion shaft 22 rotates and the pinion 25 rotates, the rod 26 moves accordingly to steer the front wheels (not shown).

The stub shaft 23 is configured to rotate integrally with a steering wheel (not shown), and a rotary valve V is provided around the stub shaft 23. The rotary valve V consists of a rotary spool 28 integrated with the stub shaft 23, and a sleeve 29 fitted to the rotary spool 28 so as to be relatively rotatable. This sleeve 29 is connected to the pinion shaft 22 via a pin 30, so that the two rotate together.

The rotary valve V thus constructed has a supply groove 101 in its rotary spool 28 that is always in communication with the pump P, and a tank return groove 102 adjacent to the supply groove 101. Furthermore, a cylinder communication groove 103 is formed in the sleeve 29 . This cylinder communication groove 103 is located on both sides of the supply groove 101 and between the supply groove and the tank reflux groove 102.

When the rotary valve V is in the neutral position as shown in FIG. 7, the supply groove 101 and the cylinder communication groove 103 underlap, and the cylinder communication groove 103 and the tank return groove 102 also underlap. I have to.

[0007] Now, when the rotary valve V is in the neutral position, the discharge fluid of the pump P flows from the supply groove 101 to the tank passage 104 via the cylinder communication groove 103 and the tank return groove 102. C is also kept in a neutral position.

When the steering wheel is operated from this state, the stub shaft 23 rotates, and the rotational force is also transmitted to the pinion shaft 22 via the torsion bar 24. However, pinion shaft 22
Since rotation is hindered by the ground resistance of the wheels, the torso bumper 24 is twisted by that amount. Therefore, the stub shaft 23 rotates more than the pinion shaft 22 by the twist angle of the torsion bar 24. That is, the shafts 22 and 23 rotate relative to each other, and the rotary spool 28 and sleeve 29 also rotate relative to each other, thereby switching the rotary valve V and operating the power cylinder C.

In this type of device, when the load on the tire side is small, such as when driving at medium to high speeds, the assist force of the power cylinder C is reduced, and when the load on the tire side is large, such as when driving at low speeds, the assist force of the power cylinder C is reduced. It is necessary to increase the assisting power of C. However, when the amount of operation of the steering wheel is small, generally a large assist force is not required. For example, when driving at medium to high speeds, the steering wheel is rarely turned significantly, and the amount of operation is usually small. On the other hand, when driving at low speeds, the steering wheel is often turned significantly.

[0010] Therefore, in this type of device, the power assist force is controlled according to the amount of operation of the steering wheel, that is, the valve operating angle. There is. In other words, Figure 8
As shown in FIG. 2, chamfered portions are formed at the edges of each of the supply groove 101 and the tank return groove 102 of the rotary spool 28. This chamfered part consists of a horizontal part h cut horizontally from the tip of the edge, and an inclined part i extending outward from this horizontal part h.

By doing this, for example, in FIG. 8, when the rotary spool 28 rotates relatively in the direction of the arrow, the opening area of the opening m in the underlapping state gradually becomes smaller. FIG. 9 shows the relationship between the operating angle of the rotary valve V and the opening area of the opening m. As is clear from FIG. 9, as the rotary spool 28 rotates in the direction of the arrow above, the opening area of the opening m gradually decreases along the characteristic of the straight line (2). and,
When the horizontal portion h and the inclined portion i overlap, the opening area becomes smaller along the straight line ■. The control characteristics of the operating pressure of power cylinder C according to this change in opening area are shown in Figure 10.
As shown by the solid line.

0012

According to the conventional steering force control device as described above, the control pressure of the power cylinder C has the characteristics shown by the solid line in FIG. , the pressure change becomes too large when the valve operating angle is small. However, ideally, the characteristics shown by the dashed line in FIG. 10 can be obtained. In other words, it is ideal that the control pressure rises slowly in a range x where the valve operating angle is small, and that the control pressure rises rapidly once the range x is exceeded. However, in the above-mentioned conventional steering force control device, since pressure changes are severe in the range x where the valve operating angle is small, there is a problem in that it is difficult to maintain steering stability especially when driving at medium and high speeds. An object of the present invention is to provide a steering force control device that can obtain the ideal control characteristics shown by the dashed line in FIG.

[0013]

[Means for Solving the Problems] The present invention provides a stub shaft that rotates integrally with a steering wheel, a pinion shaft that has a pinion that engages with a rack formed on a rod of a steering system, and a torsion bar that connects these two shafts. The present invention is based on a power steering steering force control device that includes a rotary valve consisting of a rotary spool and a sleeve that switches according to the relative rotation of the two shafts, and a power cylinder that operates according to the switching position of the rotary valve. It is something to do.

The first valve portion of the rotary valve includes a first supply groove formed in the rotary spool and constantly communicating with the pump, and a sleeve side corresponding to both sides of the first supply groove and connected to the power cylinder. It consists of a pair of cylinder communication grooves that communicate with the cylinders, and a tank groove that constantly communicates with the tank passage. Similarly, the second valve part provided in the rotary valve includes a second supply groove formed on the sleeve side and constantly communicating with the pump, and a pair of communication grooves formed on the rotary spool side corresponding to both sides of the second supply groove. and a tank return groove formed on the sleeve side adjacent to the communication groove. Furthermore, it includes a tank groove formed on the rotary spool side corresponding to the middle between the tank reflux groove and the cylinder communication groove, and a tank passage constantly communicating with the tank groove and formed in the axial direction of the rotary spool. There is.

[0015] Moreover, the first control section consisting of the first supply groove, the cylinder communication groove and the tank groove is configured to underlap at the neutral position of the rotary valve, and
The edge portion of the first supply groove is chamfered, and the second control section consisting of the second supply groove, communication groove, and tank return groove forms an underlap at the neutral position and controls the amount of underlap by the first control section. The edge of the communication groove is chamfered, and the length of the chamfered part is shorter than the length of the chamfered part of the first control part. The third control section consisting of the grooves constitutes a variable diaphragm that overlaps at the neutral position and opens at the neutral position.

[0016]

[Operation] Since the present invention is constructed as described above, when the steering wheel is kept in the neutral position, the discharge fluid of the pump is able to overcome the underlap of the first and second control sections and the variable throttle of the third control section. It is returned to the tank via the When the steering wheel is operated to the left or right, the opening area of the first valve portion first becomes smaller. However, the second control section does not perform pressure control at this stage because the underlap is large. Therefore, in the low pressure range used in the medium to high speed range, the pressure is controlled by the first control section and the third control section. Further, when the steering wheel is turned significantly, the opening degree of the second control section becomes smaller, and the opening degree of the third control section also becomes smaller, so that the supply pressure to the power cylinder increases. After all, in the medium to high speed range, the supply pressure to the power cylinder is reduced to reduce the power assist force, and in the low speed range, the supply pressure is increased to increase the assist force.

[0017]

[Embodiment] In the embodiment shown in FIGS. 1 to 7, the casing 2
1 is equipped with a rotary valve V internally, which is the same as in the conventional case. Therefore, the same reference numerals are given to the same components as in the prior art in the following description.

The rotary valve V of this embodiment includes two sets of first valve parts V1 and two sets of second valve parts V2. The first valve part V1 includes a first supply groove 31 formed in the rotary spool 28 and a first supply groove 31 formed in the rotary spool 28.
A pair of cylinder communication grooves 32a and 32b formed on the sleeve 29 side corresponding to both sides of 1, and this cylinder communication groove 3
It consists of tank grooves 38a and 38b formed on the rotary spool 28 side corresponding to both sides of the grooves 2a and 32b. Also,
The edge portion of the first supply groove 31 and the cylinder communication grooves 32a, 3
The edge portions of cylinder communication grooves 32a, 32b and the edge portions of tank grooves 38a, 38b constitute first control portions 3, 4. There is. As is clear from FIG. 3, the first control portions 1 to 4 form a chamfered portion 33 having a length L1. Furthermore, when the rotary valve V is in the neutral position, the first control units 1 to 4 maintain the underlap U1 as shown in FIG. 3.

The second valve portion V2 includes a second supply groove 34 formed in the sleeve 29, a pair of communication grooves 35a and 35b formed on the rotary spool 28 side corresponding to both sides of the second supply groove 34, and It consists of a pair of tank return grooves 36a, 36b formed on the sleeve 29 side corresponding to the outside of the communication grooves 35a, 35b, and the tank grooves 38a, 38b. In addition, the edge portion of the second supply groove 34 and the communication groove 35
The edge portions of the connecting grooves 35a, 35b constitute the second control portions 5, 6, and the edge portions of the communication grooves 35a, 35b and the tank return grooves 36a, 36b constitute the second control portion 7,
8. As is clear from FIG. 3, the second control portions 5 to 8 form a chamfered portion 37 having a length L2. Further, the first control units 1 to 4 maintain the underlap U2 as shown in FIG. 3 when the rotary valve V is in the neutral position.

The underlap U2 of the second control sections 5 to 8 is made sufficiently larger than the underlap U1 of the first control sections 1 to 4, and the underlap U2 of the first control sections 1 to 4 is
The length L1 of the chamfered portion 33 of the second control portions 5 to 8
The length L2 of the chamfered portion 37 is increased.

Furthermore, the tank grooves 38a and 38b are the tank passages 3 formed in the axial direction of the rotary spool 28.
It is connected to 9. The tank groove 38a thus constructed,
38b is connected to one edge of the tank reflux groove 36a.
, 36b constitute a third control section 9, 10. The third control sections 9 and 10 maintain the overlapping state as shown in FIG.
, 38b are chamfered to form the variable aperture portion 40.

Next, the operation of this embodiment will be explained. When the rotary valve V is in the neutral position, the fluid discharged from the pump P flows through the first and second control units 1 to 8 and the third control unit 9.
, 10 to the tank passage 39, the power cylinder C is also maintained neutral.

When the rotary spool 28 is turned slightly clockwise in FIG. 1, the first control sections 1 and 3 are gradually closed. However, when the valve operating angle is small, the underlap U2 of the second control parts 5 to 8 maintains a sufficient size, so the second control parts 5 to 8 hardly control the pressure, and the second supply groove 3 It functions only as a relay flow path between the variable throttle section 40 of the third control section 9 and 10. Therefore, in this case, the first control sections 1, 3 and the third control sections 9, 1
However, since a predetermined flow rate is returned to the tank passage 39 from the third control sections 9 and 10, the rate of pressure increase becomes low, as shown in the range x in FIG. Therefore, if this range x is used as a medium-high speed range,
Stability in medium and high speed ranges can be ensured.

When the rotary spool 28 is further turned clockwise, the first control sections 1 and 3 are closed, so the second control section 1 and 3 are closed.
The pressure is controlled by the control units 6 and 8 and the third control units 9 and 10. In this state, the opening degrees of the third control parts 9 and 10 become smaller, and the opening degrees of the second control parts 6 and 8 also become smaller, so that the rate of pressure increase increases. Therefore, if this range is used as a low speed range, sufficient power assist force can be obtained.

Note that the length L1 of the chamfered portion 33 of the first control portions 1 to 4 and its underlap U1, the second control portions 5 to
Length L2 of the chamfered portion 37 of No. 8 and its underlap U2
, and the opening degree of the variable aperture 40 of the third control sections 9 and 10, the control characteristics shown in FIG. 5 can be obtained. If the characteristics shown in FIG. 5 are to be obtained using the conventional structure, the shape of the chamfered portion must be as shown in FIG. 10. That is, the shape of the chamfered portion 41 must be such that the tip of the edge portion is concave. However, in practice, there is a problem in that such processing is extremely difficult. However, according to the structure of this embodiment, it is sufficient to process the first to third control sections by simply scraping off their edges, which simplifies the process.

[0026]

According to the steering force control device of the present invention, the opening area of the device is controlled via the first control section, the second control section, and the third control section, so that the control pressure for the power cylinder is controlled. becomes an ideal characteristic. Therefore, steering stability is improved during high-speed driving when the valve operating angle is small. Moreover, the chamfering of each control section for this purpose is simple, and the construction is improved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram specifically showing a connection situation of a rotary valve.

FIG. 2 is a circuit diagram.

FIG. 3 is a partial cross-sectional view showing the relative relationship between first to third control sections.

FIG. 4 is a graph showing the relationship between the valve operating angle and the opening area of the first and second valves.

FIG. 5 is a graph showing the relationship between valve operating angle and power cylinder pressure.

FIG. 6 is a sectional view of a conventional device.

FIG. 7 is an explanatory diagram specifically showing the connection status of a conventional rotary valve.

FIG. 8 is a partially enlarged sectional view of a control section of a conventional rotary valve.

FIG. 9 is a graph showing the relationship between the conventional valve operating angle and the opening area of the control section.

FIG. 10 is a graph showing the relationship between the conventional valve operating angle and the power cylinder pressure.

FIG. 11 is an enlarged sectional view of another conventional control unit.

[Explanation of symbols]

22 Pinion shaft 23 Stub shaft 24 Torsion bar 25 Pinion V rotary valve 28 Rotary spool 29 Sleeve C Power cylinder V1 1st valve part V2 2nd valve part 31 First supply groove 32a Cylinder communication groove 32b Cylinder communication groove 1 to 4 First control section 33 Chamfered part 34 Second supply groove 35a Communication groove 35b Communication groove 36a Tank reflux groove 36b Tank reflux groove 5-8 Second control section 37 Chamfered part 9, 10 Third control section 38a Tank groove 38b Tank groove 39 Tank passage 40 Variable aperture part

Claims (1)

[Claims] 1. A stub shaft that rotates integrally with a steering wheel, a pinion shaft that has a pinion that engages with a rack formed on a rod of a steering system, a torsion bar that connects these two shafts, and a relative rotation of the two shafts. In a power steering steering force control device comprising a rotary valve consisting of a rotary spool and a sleeve that switches according to the switching position of the rotary valve, and a power cylinder that operates according to the switching position of the rotary valve, the rotary valve has a first valve section. and a second valve part, and the first valve part includes a first supply groove formed in the rotary spool and constantly communicating with the pump;
It consists of a pair of cylinder communication grooves formed on the sleeve side corresponding to both sides of the first supply groove and communicating with the power cylinder, and a tank groove constantly communicating with the tank passage, and the second valve part is formed on the sleeve side. a second supply groove formed and constantly communicating with the pump; a pair of communication grooves formed on the rotary spool side corresponding to both sides of the second supply groove; and a tank formed on the sleeve side adjacent to the communication groove. Further, a tank groove is formed on the rotary spool side corresponding to the middle between the tank reflux groove and the cylinder communication groove, and a tank groove is formed in the axial direction of the rotary spool and is always in communication with the tank groove. On the other hand, the first control section consisting of the first supply groove, the cylinder communication groove, and the tank groove is configured to underlap at the neutral position of the rotary valve, and the first control section includes a first supply groove, a cylinder communication groove, and a tank passage. Chamfered, second supply groove,
The second control section, which is composed of a communication groove and a tank return groove, underlaps in the neutral position and makes the amount of underlap larger than the amount of underlap of the first control section, and also has an underlap at the edge part of the communication groove. The chamfering process is performed, and the length of the chamfered part is made longer than the length of the chamfered part of the first control part, and the third control part consisting of the tank return groove and the tank groove overlap at the neutral position, and A steering force control device for power steering comprising a variable diaphragm that opens at its neutral position.