JP2951364B2 - Steering force control device for power steering - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a steering force control device that controls a steering force according to a steering angle of a steering wheel.

(Prior Art) The conventional device shown in FIGS.
In addition, a pinion shaft 2 and a stub shaft 3 are coaxially inserted, and these two shafts 2, 3 are connected via a torsion bar 4.

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 a steering system. Therefore, when the pinion shaft 2 rotates and the pinion 5 rotates, the rod 6 moves accordingly, and the front wheel (not shown) is steered.

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

The rotary valve V includes a rotor 8 integrated with the stub shaft 3 and a sleeve 9 fitted to the rotor 8 so as to be relatively rotatable. The sleeve 9 is connected to the pinion shaft 2 via a pin 10 so that the two rotate together.

Further, as shown in FIG. 6, the rotor 8 forms a plurality of recesses 11 to 18 at predetermined intervals in the circumferential direction thereof,
The portions located between these concave portions 11 to 18 are control convex portions 19 to 26. Of the recesses thus formed, every other recess 12, 14, 16, 18 communicates with a tank passage 27 formed at the center of the rotor 8.

Further, on the inner periphery of the sleeve 9, the same number of control grooves 28 to 35 as the control protrusions are formed. And the control grooves 28, 30,
Each of 32 and 34 is connected to one pressure chamber 36 of the power cylinder C
And the control grooves 29, 31, 33, 35 communicate with the other pressure chamber 37. Further, between the control grooves 29, 30, between 31, 32,
A supply port 38 communicating with the pump P is opened between 33 and 34 and between 35 and 28, respectively.

With the above configuration, if the steering wheel (not shown) is held at the neutral position, the rotary valve V
Maintain the position shown in FIG. In this state, the fluid discharged from the pump P is supplied from the supply port 38 to the concave portions 11, 13,
15, 17 → control grooves 28-35 → recesses 12, 14, 16, 18 → returned to tank T via tank passage 27, and power cylinder C is also kept at the neutral position.

When the steering wheel is operated from the above state,
As the stub shaft 3 rotates, its rotational force is also transmitted to the pinion shaft 2 via the torsion bar 4. However, since the rotation of the pinion shaft 2 is hindered by ground friction of the wheels, the torsion bar 4 is twisted by that amount. For this purpose, the stub shaft 3 is fixed to the pinion shaft 2 by the twist angle of the torsion bar 4.
More than spin. That is, both shafts 2 and 3 rotate relatively.

As the shafts 2 and 3 rotate relative to each other, the rotor 8 and the sleeve 9 also rotate relative to each other, so that the rotary valve V is switched.
If rotated to the right in the figure, the result is as follows.

When the rotor 8 rotates clockwise from the state shown in FIG. 6, the passage connecting the supply port 38 to the control grooves 28, 30, 32, and 34 expands, and the control grooves 28, 30, 32, and 34 1
The passage communicating with 2, 14, 16, 18 is reduced. Therefore, the discharge fluid from the pump P is supplied from the supply port 38 to the recess.
11, 13, 15, 17 → supplied to one pressure chamber 36 of the power cylinder via control grooves 28, 30, 32, 34.

At this time, the control grooves 29, 31, 33, 35 and the concave portions 12, 14, 16, 18
Since the passage for communicating with the power cylinder is expanded, the power cylinder C
The working fluid in the other pressure chamber 37 of the control grooves 29, 31, 33,
35 → recesses 12, 14, 16, 18 → returned to the tank via the tank passage 27.

Accordingly, the piston rod 39 of the power cylinder C moves upward in the drawing and moves the rod 6 of the steering system to steer the front wheels. If the steering wheel is continuously rotated, the pinion shaft 2 and the stub shaft 3 rotate integrally while maintaining the relative rotation angle, and the pinion 5 rolls on the rack 7. Even if the steering wheel is stopped in this state, since the rotary valve V is still switched, the power cylinder C continues to operate. Since the pinion 5 continues to rotate with the operation of the power cylinder C, the sleeve 9 catches up with the rotor 8 and the rotary valve V is set to the neutral position. When the rotary valve V returns to the neutral position, the power cylinder C stops and the switching position is maintained.

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

Then, 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 of the power cylinder C is suppressed low, and the power assisting force is reduced. That is, when the steering angle is small, the steering wheel can be turned with a small force even at a low speed. Conversely, when driving at high speed, turning the steering wheel too far is dangerous, so there is almost no such thing. Therefore, the power assisting force is reduced to improve the maneuverability.

Also, when turning the steering wheel greatly,
Since the vehicle is running at low speed, the pressure of the power cylinder C is increased when the operating angle of the rotary valve V is large.

In order to keep the pressure of the power cylinder C low and keep the power assist force small when the valve operating angle is small as described above, conventionally, the edges of the control projections 19 to 26 of the rotor 8 are formed as shown in FIG. A chamfered portion is formed. The chamfered portion includes a horizontal portion h cut horizontally from the edge tip and an inclined portion i extending from the horizontal portion h toward the center of the control convex portion.

By doing so, 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 projection and the control groove gradually decreases. FIG. 8 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 turns and the edge portions of the control projections 19 to 26 approach the control grooves 28 to 35, the opening area decreases along the straight line characteristics. If the horizontal portion h and the inclined portion i are out of the control groove and wrap around the sleeve, the opening area is reduced according to the characteristics of the straight line.

The control characteristic of the operating pressure of the power cylinder C according to the change of the opening area is 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 characteristic shown by the solid line in FIG. 9, when the valve steering angle is small, For example, drawing x
The pressure change within the range becomes too large. Actually, it is ideal that the characteristic shown by the dashed line in FIG. 9 is obtained. That is, in the range x where the valve operating angle is small, the control pressure gradually increases, and ideally, the control pressure sharply increases from the time when the control pressure exceeds the range x.

However, in the conventional steering force control device described above, there is a problem that it is difficult to maintain the steerability especially during high-speed running because the pressure change is severe in a range x where the valve steering angle is small.

An object of the present invention is to provide a steering force control device capable of obtaining ideal control characteristics shown by a dashed line in FIG.

(Means for Solving the Problems) The present invention relates to a stub shaft that rotates integrally with a steering wheel, a pinion shaft that has a pinion that meshes with a rack formed on a steering system rod, and a torsion bar that connects these two shafts. And a rotary valve composed of a rotor and a sleeve that are switched in accordance with the relative rotation of the two shafts. The rotor of the rotary valve forms a plurality of recesses at predetermined intervals in its circumferential direction. In addition, a portion located between these concave portions is used as a control convex portion, and the sleeve is also provided with the same number of control grooves as the control convex portions while maintaining a predetermined interval in a circumferential direction of the sleeve. It is based on a force control device.

On the premise of the above-described device, the present invention forms a chamfered portion at an edge portion of the control convex portion, and forms a first or third control portion with the control convex portion and the control groove. Has a structure in which the supply fluid from the pump is divided and controlled 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 comprising a throttle is formed in the sleeve on the upstream side of the third control section. In addition, the third control unit is characterized in that when the operating angle of the rotary valve is equal to or larger than a certain angle, a throttle effect proportional to the operating angle is exhibited to reduce the amount of outflow to the tank. .

(Operation of the Present Invention) Since the present invention is configured as described above, by switching the rotary valve, the opening area of the flow passage of the first control unit leading to the tank is reduced at an expected stage. Therefore, at the expected stage, the third control unit is sufficiently open, and the outflow amount to the tank is controlled by the first and second control units.

If the switching amount of the rotary valve is further increased from this state, the opening area of the third control unit is reduced, so that the supply flow rate to the power cylinder increases at a stretch, and the control pressure increases rapidly. is there.

(Effect of the Present Invention) According to the steering force control device of the present invention, the opening area of the device is controlled via the first control unit, the second control unit, and the third control unit. Pressure is an ideal characteristic. Therefore, the steerability during high-speed running with a small valve operating angle is improved.

(Embodiment of the present invention) The rotary valve is also used in the embodiment shown in FIGS. 1 to 4. However, since the switching principle is exactly the same as the conventional one, the same reference numerals are used for the same components as the conventional one. And the details are 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 to 35 are formed in the sleeve 9. These concave portions, control convex portions and control grooves are formed. Together, they constitute a first control unit I and a third control unit III as shown in FIG.

The first control unit I includes an edge portion of the control convex portion,
With a chamfered portion 40 that portion chamfered as shown in FIG. 3, the length of the chamfer 40 and L _1. And when the valve V is in the neutral position,
The distance or underlap amount from the edge portion of the chamfered portion 40 to the end portion of the control groove of the sleeve 9 has a U _1.

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.

Above also the edge portion of the control protrusion of the third control unit III, to form a chamfered portion 41 as shown in FIG. 3, the length of the chamfered portion 41 and L _2. The valve V
There when in the neutral position, and the distance or underlap amount from the edge portion of the chamfered portion 41 to the end portion of the control groove of the sleeve 9 as the U _2.

Then, the length L ₁ of the chamfer 40, the chamfered portion
41 of length L ₂ with sufficiently small and sufficiently large underlap amount U ₂ against underlap amount U _1.

The third control unit III thus configured is connected to the pump P via a fixed throttle 42 as the second control unit II formed on the sleeve 9.
Connected to

 Next, the operation of this embodiment will be described.

If the steering wheel is maintained at the neutral position, the rotary valve V also maintains the illustrated neutral position, so the discharge fluid of the pump P flows from the supply port 38 to the tank via the first control unit I and the tank passage 27. Will be returned. Therefore, almost no pressure is generated in the power cylinder C as shown in FIG.

When the rotary valve V is switched by turning the steering wheel from the above state, the following occurs.

Now, when the valve operating angle is small, such as when the vehicle is running at a medium to high speed, the opening area of the first control unit I becomes small.
The opening area of the control unit III is reduced only to such an extent that the aperture effect is not affected. Therefore, at this time, the pressure is controlled by the first control unit I and the second control unit II, but a predetermined flow rate flows out of the fixed throttle 42 constituting the second control unit II into the tank. Therefore, the characteristics of the valve operating angle and the pressure of the power cylinder are as shown in FIG.

Further, when the steering wheel is turned largely as in the case of low-speed running, the opening degree of the third control unit III is reduced this time, so that the return flow to the tank is reduced at a stretch, and as shown in FIG. The pressure in the cylinder C rises sharply.

As described above, since the valve operating angle is small during straight running or in a range in which the vehicle is in a minute steering state, almost the entire discharge amount of the pump P is returned to the tank via the first control unit II, and the cylinder C The pressure hardly rises.

As described above, according to the device of this embodiment, the pressure rise of the power cylinder C is gradual until the steering torque reaches a certain level or more, so that the steering characteristics during straight running or medium-high speed running are stabilized. .

[Brief description of the drawings]

1 to 4 show an embodiment of the present invention.
FIG. 2 is a sectional view, FIG. 2 is a circuit diagram specifically showing a rotary valve, FIG. 3 is an explanatory diagram showing a relative relationship between first to third control units, and FIG. 4 is a steering torque and a pressure of a power cylinder. 5 to 9 show a conventional device, FIG. 5 is a sectional view, FIG. 6 is a circuit diagram specifically showing a rotary valve, and FIG. 7 is a rotary valve. 8 is a graph showing the relationship between the valve operating angle and the opening area of the passage communicating with the tank, and FIG. 9 is a diagram showing the relationship between the steering torque and the pressure of the power cylinder. It is a graph. 2 ... Pinion shaft, 3 ... Stub shaft, 4 ...
... torsion bar, 5 ... pinion, 6 ... rod, 7
... Rack, V ... Rotary valve, 8 ... Rotor, 9
... Sleeve, 11-18 ... Recess, 19-26 ... Control convex,
28 to 35: control groove, P: pump, I: first control unit,
II: second control unit, III: third control unit, 40, 41: chamfering unit, 42: fixed diaphragm as second control unit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-215462 (JP, A) JP-A-59-220458 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B62D 5/083

Claims (1)

(57) [Claims] A stub shaft that rotates integrally with a steering wheel, a pinion shaft having a pinion that meshes with a rack formed on a steering system rod, a torsion bar that connects these two shafts, and a relative rotation between the two shafts. And a rotary valve comprising a sleeve which is switched in accordance with the direction of rotation of the rotary valve. The rotor of the rotary valve forms a plurality of recesses at predetermined intervals in the circumferential direction thereof, and is positioned between the recesses. In the steering force control device for a power steering, the same portion as the control protrusion is formed at a predetermined interval in the circumferential direction of the sleeve. While forming a chamfered portion at an edge portion of the portion, a first or third control portion is constituted by the control convex portion and the control groove, and a first control portion is formed. Has a structure in which the supply fluid from the pump is divided and controlled 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 comprising a throttle is formed in the sleeve on the upstream side of the third control section. Along with
The third control unit is a steering power control device for a power steering, wherein when the operation angle of the rotary valve is equal to or larger than a predetermined angle, a throttle effect proportional to the operation angle is exerted to reduce the outflow to the tank.