JPH0431176A - Steering force control device for power steering - Google Patents

Abstract

PURPOSE:To control the control pressure to have ideal characteristic by constituting first and third control parts out of control projecting parts on the outer circumference of a rotor and control grooves on the inner circumference of a sleeve in a rotary valve which is changed over according to relative rotation of two shafts, and forming a second control part in the sleeve. CONSTITUTION:In a rotary valve V constituted out of a roller 8 in one body with a stub shaft and a sleeve 9 fitted to this roller 8, recessed parts 11 - 18 and control projecting parts 19 - 26 are formed on the roller 8, control grooves 28 - 35 are formed on the sleeve 9, and first control parts I and third control parts III are constituted out of these recessed parts, control projecting parts, and control grooves. By the first control parts I, opening area of respective passages communicated to a tank passage 27 and a power cylinder C are vari able. The third control parts III are connected to a pump P through fixed restrictors 42 as second control parts III are sufficiently opened, the outflow quantity to a tank is controlled with the first and second control parts I, II, and at minifying the opening area of the third control parts III, the flow can be quickly increased.

Description

[Detailed Description of the Invention] (〕♀-Fields of Application of Industry Ten) This invention provides the following features:
The present invention relates to a steering force control device that controls steering force.

(Prior Art) In the conventional device shown in FIGS. 5 to 9, a pinion shaft 2 and a stub shaft 3 are coaxially inserted into a casing 1, and both shafts 2.3 are connected to a torsion bar 4. are connected via.

A pinion 5 is formed on the pinion shaft 2, and the pinion 5 is engaged with a rack 7 formed on a rod 6 of the steering system. Therefore, when the pinion shaft 2 rotates and the pinion 5 rotates, the rod 6 moves accordingly to steer the front wheels (not shown).

The stub shaft 3 is configured to rotate integrally with a steering wheel (not shown), and is provided with a rotary valve (2) around it.

The rotary valve V consists of a rotor 8 integrated with the stub shaft 3, and a sleeve 9 fitted to the rotor 8 so as to be relatively rotatable. This sleeve 9 is connected to the pinion shaft 2 via a pin 1O, so that both rotate together.

Further, as shown in FIG. 6, the rotor 8 has a plurality of concave portions 11 to 18 formed at predetermined intervals in the circumferential direction, and a portion located between these four portions 11 to 18 is a control convex portion.
9 to 26. Of these recesses, every other recess 12, 14, 16, 18 communicates with a tank passage 27 formed in the center of the rotor 8.

Moreover, the same number of control grooves 28 to 35 as the control convex portions are formed on the inner circumference of the sleeve 9. And the control groove 28.
30, 32, and 34 are connected to one pressure chamber 36 of the power cylinder C, and the control grooves 29.31.33.3
5 is communicated with the other pressure chamber 37. Further, supply ports 38 communicating with the pump P are opened L1 between the control grooves 29 and 30, between 31 and 32, between 33 and 34, and between 35 and 28, respectively.

Under the above configuration, when the steering wheel (not shown) is held at the neutral position, the rotary valve V maintains the position shown in FIG. 6. In this state, pump P
The fluid discharged from the supply boat 38 → the recess 11.
13.15.17 → Control grooves 28 to 35 → Recessed portion 12.14
．． 16.18 → It is returned to the tank T via the tank passage 27, and the power cylinder C is also maintained at the neutral position.

When the steering wheel is operated from the above state, the stub shaft 3 rotates, and the rotational force is also transmitted to the pinion shaft 2 via the torsion bar 4. However, since the pinion shaft 2 is prevented from rotating due to ground friction of the wheels, the torsion bar 4 is twisted by that amount. Therefore, the stub shaft 3 rotates more than the pinion shaft 2 by the helix angle of the torsion bar 4. In other words, both shafts 2.3 rotate relative to each other.

As the shafts 2.3 rotate relative to each other in this way, the rotor 8 and sleeve 9 also rotate relative to each other, so if the rotary valve (■) is switched or, for example, the rotor 8 rotates to the right in Figure 6, then It will look like this:

When the rotor 8 rotates clockwise from the state shown in FIG. 6, the passage connecting the supply port 38 and the control grooves 28.30.32.34 expands, and
2.34 and the recess 12.14.16.18 are reduced in size. Therefore, the discharge fluid from the pump P is supplied to one pressure chamber 36 of the power cylinder via the supply boat 38 → recess 11.13.15.17 → control groove 28.30.32.34.

At this time, the control groove 29.31.33.35 and the recess 12.1
4.16.18 Since the passage that communicates with Enlarged 1-B,
The working fluid in the other pressure chamber 37 of the power cylinder C is
Control groove 29.31.33.35 → recess 12.14.16
．． 18 → returned to the tank via the tank passage 27.

Therefore, the piston rod 39 of the power cylinder C moves in the direction of -F in the drawing, and the rod 6 of the surface steering system moves.
Move the surface to change the surface width. If the steer link wheel continues to rotate, the pinion shaft 2 and stub shaft 3 rotate integrally without maintaining the relative rotation angle, and are transferred over the pinion 5 or the rack 7. Even if the steering wheel is stopped in this state, rotary valve V remains inactive, so power cylinder C continues to operate. As the power cylinder C operates, the binion 5 also continues to rotate, so it catches up with the sleeve 9 or the rotor 8.
Place the rotary valve ■ in the neutral position. Rotary valve V
When the power cylinder C returns to the neutral position, the power cylinder C stops and maintains the switching position.

If the steering wheel is turned in the returning direction from the above state, the rotary valve V is also switched in the opposite direction, and the power cylinder 'C is also returned to the neutral position.

In this type of device, when the steering angle is small, in other words, when the operating angle of the rotary valve V is small, the pressure in the power cylinder C is kept low to reduce the power assist force. In other words, when the steering angle is small,
Even at low speeds, you can turn the steering wheel with a small amount of force. On the other hand, when driving at high speeds, it is dangerous to turn the steering wheel too far, so this rarely happens. Therefore, the power assist force is reduced to improve steering stability.

Furthermore, when the steering wheel is turned significantly, the pressure in the power cylinder C is increased when the operating angle of the rotary valve V is large, since the vehicle is traveling at low speed.

In order to keep the pressure of the power cylinder 'C low and suppress the power assist force to a small level when the valve operating angle is small as described above, conventionally, the edges of the control convex parts 19 to 26 of the rotor 8 are used as shown in FIG. A chamfered portion is formed on the surface. This chamfered portion has a horizontal portion cut horizontally from the tip of the edge, and an inclined portion i from this horizontal portion toward the center portion of the control convex portion.

By doing this, for example, when the rotor 8 relatively rotates in the direction of the arrow in FIG. 7, the opening area of the opening m formed by the control convex portion and the control groove gradually becomes smaller. FIG. 'fJ8 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. 8, as the rotor 8 rotates and the edge portions of the control convex portions 19 to 26 approach the control grooves 28 to 35, they open along the characteristic of the straight line (1) [1 area or smaller]. Become. If the horizontal portion and the inclined portion i come off the control groove and overlap with the sleeve, the opening area becomes smaller in accordance with the characteristics of the straight line (2).

The control characteristics of the operating pressure of the power cylinder C in response to the change in the opening area are as shown by the solid line in FIG.

(Problems to be Solved by the Invention) According to the conventional steering force control device as described above, since the control pressure of the power cylinder C has the characteristics shown by the solid line in FIG. 9, when the valve steering angle is small, For example, the pressure change within the range of drawing X becomes too large. In reality, it is ideal to obtain the characteristics shown by the single point 3n line in FIG. 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 from the point at which the valve operating angle exceeds the range X.

However, in the above-mentioned conventional steering force control device, since the pressure changes drastically in the range X where the valve steering angle is small, there is a problem in that it is difficult to maintain steering stability especially when driving at high speed.

An object of the present invention is to provide a steering force control device that can obtain the ideal control characteristics shown by the one-point line 3n in FIG.

(Means for Solving the Problem) This invention provides a stub shaft that rotates integrally with a steering link wheel, a pinion shaft that has a pinion that engages with a rack formed on a rod of a steering system, and a system that connects these two shafts. It comprises a torsion bar, and a rotary valve consisting of a rotor and a sleeve that switch according to the relative rotation of the two shafts, and the rotor of the rotary valve has a plurality of four parts at a predetermined interval in the circumferential direction. and the portion located between these concave portions is a control convex portion, and the sleeve also has the same number of control grooves as the control convex portions at a predetermined interval in the circumferential direction of the sleeve. This is based on a steering force control system.

While the above-mentioned device is used as a travel device, the present invention forms a chamfered portion on the edge portion of the control convex portion, and configures a first or third control portion with the control convex portion and the control groove, and the first control portion The configuration is such that the fluid supplied from the pump is divided into a flow rate to be supplied to the power cylinder and a flow rate to be returned to the tank,
A second control section consisting of a throttle is formed in the sleeve on the upstream side of the third control section, and the third control section controls the switching amount when the operating angle of the rotary valve exceeds a certain level. It is characterized by a structure that exhibits a proportional throttling effect to reduce the amount of flow into the tank.

(Operation of the present invention) Since the present invention is configured as described above, by switching between the port and the tally valve, the opening area of the flow path of the first control section leading to the tank is first reduced at the desired stage. However, at the initial stage, the third control part is fully open, so that the outflow to the tank will be controlled by the first and second control parts.

From this state, if you roughly increase the switching amount of the rotary valve, the opening area of the third control section will become smaller, so the flow rate supplied to the power cylinder will suddenly increase.
The control pressure increases rapidly.

(Effects of the present invention) According to the steering force control device of the present invention, the first control section, the second
Since the opening area of the device is controlled via the control section and the third control section, the control pressure for the power cylinder has ideal characteristics. Therefore, the steering stability during high-speed driving when the valve operating angle is small is improved.

(Embodiment of the present invention) A rotary valve is also used in the embodiment shown in Figs. 1 to 4, but the switching principle is exactly the same as that of the conventional one, so the same reference numerals are used for the same components as the conventional one. and explain
The details will be omitted.

In the rotary valve V, concave portions 11 to 18 and control convex portions 19 to 26 are formed in the rotor 8, and control grooves 28 are formed in the sleeve 9.
35, and these four parts, the control convex part and the control groove, together constitute the first control part and the third control part 2, as shown in FIG.

The first control part (1) chamfers the edge part of the control convex part as shown in FIG. Saori is doing. When the valve V is in the neutral position, the distance from the edge of the chamfered portion 40 to the end of the control groove of the sleeve 9, that is, the amount of underlap, is determined by Ul.
It is said that

By switching the rotary valve V in either direction, the opening area of the passage leading to the tank passage 27 is reduced, while the opening area of the passage leading to the power cylinder C is increased.

As shown in FIG. 3, a chamfered portion 41 is also formed on the edge portion of the control convex portion of the third control portion (2), and the length of this chamfered portion 41 is set to L2. Further, when the valve (1) is in the neutral position, the distance from the edge portion of the chamfered portion 41 to the end of the control groove of the sleeve 9, that is, the amount of underlap is defined as U2.

The length L2 of the chamfered portion 41 is made sufficiently smaller than the length of the chamfered portion 40, and the underlap amount U2 is made sufficiently larger than the underlap amount U1.

The third control section (2) thus constructed is connected to the pump P via a fixed throttle 42 which is formed on the sleeve 9 and serves as a second control section (2).

Next, the operation of this embodiment will be explained.

If the steering link wheel is kept in the neutral position, the rotary valve ■ will also be kept in the neutral position shown, and the fluid discharged from the pump P will flow from the supply port 38 via the first control unit ■ and the tank passage 27. returned to the tank. Therefore, as shown in FIG. 4, almost no pressure is generated in the power cylinder C.

If the rotary valve V is switched by turning the steering wheel from the above state, the following will occur.

Now, when the valve operating angle is small, such as when driving at medium to high speeds, the opening area of the 751 control part becomes smaller, or the third
The opening area of the control section (2) is reduced only to the extent that it does not affect the aperture effect. Therefore, at this time, the pressure is controlled by the first control section and the second control section (2), or a predetermined flow rate flows out into the tank from the fixed throttle 42 that constitutes the second control section (2). Therefore, the characteristics of the valve operating angle and power cylinder pressure are shown in Figure 4■
become that way.

Furthermore, when the steering wheel is turned significantly as when driving at low speeds, the opening degree of the third control section (■) becomes smaller, so the flow rate returned to the tank decreases, as shown in Figure 4 (■).
As shown in the figure, the pressure in the power cylinder C increases rapidly.

In this way, in range (2), which is when the vehicle is traveling straight or in a micro-steering state, the valve operating angle is small, so almost the entire discharge amount of the pump P is returned to the tank via the first control section.
The pressure in cylinder C hardly increases.

As described above, according to the device of this embodiment, the pressure in the power cylinder C increases gradually until the steering torque reaches a certain level, so the steering characteristics are stable when driving straight or at medium-high speeds. .

[Brief explanation of the drawing]

Drawings 1 to 4 show embodiments of this invention.
The figure is a sectional view, Figure 2 is a circuit diagram specifically showing the rotary valve, Figure 3 is an explanatory diagram showing the relative relationship between the first to third control parts, and Figure 4 is the steering torque and power cylinder pressure. Graphs showing the relationship between Figure 8 is a graph showing the relationship between the valve operating angle and the opening area of the passage communicating with the tank, and Figure 9 is a graph showing the relationship between steering torque and power cylinder pressure. It is a graph. 2... Pinion shaft, 3... Stub shaft,
4... Torsion bar 5... Pinion, 6-...
Rod, 7...Rack, ■--Rotary valve, 8
...Rotor, 9-...Sleeve, 11-18...Four parts, 19-26...Control protrusion, 28-35...Control groove, P...Pump, ■...First Control unit, n-...second control unit, m-...third control unit, 40.41...control unit, 42...fixed diaphragm as second control unit.

Claims (1)

[Claims] A stub shaft that rotates integrally with the steering wheel, a pinion shaft that has a pinion that engages with a rack formed on a rod of the steering system, a torsion bar that connects these two shafts, and a torsion bar that switches according to the relative rotation of the two shafts. The rotary valve is equipped with a rotary valve consisting of a rotor and a sleeve. In the power steering steering force control device, the sleeve also has control grooves formed in the same number as the control protrusions at a predetermined interval in the circumferential direction thereof, the sleeve having an edge portion of the control protrusion. While the chamfered portion is formed, the control convex portion and the control groove constitute a first or third control portion, and the first
The control section is configured to divide the supply fluid from the pump into a flow rate to be supplied to the power cylinder and a flow rate to be returned to the tank, and a second control section consisting of a throttle is installed in the sleeve on the upstream side of the third control section. In addition, the third control section is configured to reduce the amount of flow into the tank by exerting a throttling effect proportional to the switching amount when the operating angle of the rotary valve exceeds a certain level. Steering force control device.