JPH0585379A - Power steering - Google Patents

Abstract

PURPOSE:To obtain travel stability, facilitate corrective steering and reduce force required for steering by providing an assisting torque control means for reducing the assisting torque in the case of the product of the detected steering angular velocity and steering torque being positive whereas enlarging the assisting torque in the case of being negative. CONSTITUTION:There are provided a steering angular velocity sensor 42 for detecting the steering angular velocity of a steering wheel 28, a steering torque sensor 40 for detecting steering torque with the same direction as the steering angular velocity as the same code, and a power steering computer 100 serving as an assisting torque control means for reducing assisting torque in the case of the product of the detected steering angular velocity and steering torque being positive whereas enlarging assisting torque in the case of being negative. Accordingly, when the directions of the steering angular velocity and steering torque are the same, the product is made positive to reduce assisting torque, and negative in the reverse case to enlarge assisting torque. When the steering wheel 28 is not rotated and thereby the angular velocity is zero, the product becomes zero, so that assisting torque is not changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering device, and more particularly to determination of assisting torque based on steering angular velocity and steering torque.

[0002]

2. Description of the Related Art A power steering apparatus has an assisting means for assisting a steering torque applied to a steering wheel and is configured to reduce a steering load on a driver. The power steering device described in Japanese Patent Application Laid-Open No. 2-31973 is an example of the power steering device. In this device, the higher the vehicle speed, the smaller the assisting torque is, and the running stability is ensured.

[0003]

However, in this way, a large force is required to keep the steering wheel in the rotational operation position when traveling on a curve at high speed, and the unevenness of the road surface and the friction coefficient When torque is applied from the steering wheel to the steering wheel due to a disturbance such as a change, a large steering torque is required to perform the correction steering.

[0004]

In order to solve the above problems, the present invention provides a power steering apparatus including (a) steering angular velocity detecting means for detecting a steering angular velocity of a steering wheel, and (b) a steering wheel. Steering torque detecting means for detecting the steering torque with the same sign as the steering angular velocity and (c) the assisting torque is reduced when the product of the detected steering angular velocity and the steering torque is positive, and when the product is negative, Is to provide an assisting torque control means for increasing the assisting torque.

[0005]

In the power steering device configured as described above, when the direction of the steering angular velocity and the direction of the steering torque are the same, the product thereof becomes positive and the assisting torque is reduced, and in the opposite case, it becomes negative. Therefore, the assisting torque is increased. When the steering wheel is not rotating and the angular velocity is 0, the product becomes 0, and the assisting torque is neither increased nor decreased.

[0006]

Therefore, when the vehicle turns as the driver operates and the direction of the steering angular velocity and the direction of the steering torque are the same, the assisting torque is reduced and the product is negative or 0. As a result, steering resistance is large and running stability can be obtained. In addition, when the steering wheel is rotated by the disturbance of the road surface and the driver rotates the steering wheel to correct it, the steering torque applied from the steering wheel is opposite to the steering torque applied by the driver. When the steering torque is rotated in the opposite direction, the direction of the steering torque and the direction of the steering angular velocity are opposite to each other, and the product thereof becomes negative to increase the assisting torque, so that the correction steering can be easily performed. Further, when the steering wheel is kept at a constant rotational operation position when traveling on a curve at high speed, the product of the steering torque and the steering angular velocity is 0, and the assisting torque is neither large nor small. It is larger than when rotating and requires less force to hold the steering.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. This power steering device is a rack and pinion type, and in FIG. 2, reference numeral 10 is a steering gear box. A rotary valve 12, a steering gear 14, and a hydraulic reaction device 16 are provided inside the steering gear box 10, and a power cylinder 18 is provided at a rack tube.

In the gear housing 20 that constitutes the steering gear box 10, the input shaft 22 is a bearing 24.
It is rotatably supported by. The input shaft 22 has a cylindrical shape, a steering wheel 28 is connected thereto via a rod 26, and a torsion bar 30 is arranged inside thereof. One end of the torsion bar 30 is fixed to the input shaft 22, while the other end is fixed to the output shaft 32.

A pinion gear 36 is formed on the output shaft 32 and meshes with a rack 38 to form the steering gear 14. Steering wheels are connected to both ends of the rack 38 via tie rod ends and knuckle arms (not shown). When the input shaft 22 is rotated by the steering wheel 28,
The torsion bar 30 elastically deforms and the input shaft 22
Is transmitted to the output shaft 32. And
The pinion gear 36 is rotated and the rack 38 is
Moves, and the direction of the steering wheel is changed to the steering wheel 28.
It can be changed to the same direction as the operating direction of.

The steering torque applied to the steering wheel 28 is detected by a steering torque sensor 40 as steering torque detecting means, and the angular velocity of the steering angle of the steering wheel 28 is detected by a steering angular velocity sensor 42 as steering angular velocity detecting means. These sensors 40, 42
Are provided on the rod 26, and in the present embodiment, the sensors 40 and 42 have positive detection values when turning the steering wheel to the right, and negative values when turning the steering wheel to the left. Configured to be a value.

Both ends of the rack 38 that are out of mesh with the pinion 36 are axially movably fitted to the rack tube, and the power piston 46 is concentric between one end and the tie rod end. The power cylinder 18 is fixed in a fixed shape.

The input shaft 22 and the gear housing 2
A sleeve 50 is rotatably fitted between the rotary valve 1 and the output shaft 32, and is fixed to the output shaft 32 by a pin (not shown).
Make up 2. The rotary valve 12 has a liquid passage 5
4, the vane pump 56 is connected, the liquid passage 58 is connected to the reservoir tank 60, the liquid passage 62 is connected to the first hydraulic chamber 66 formed on one side of the power piston 46, and the liquid passage 68 is connected. It is connected to a second hydraulic chamber 70 formed on the other side.

The rotary valve 12 normally connects the vane pump 56, the first and second hydraulic pressure chambers 66 and 70 to the reservoir tank 60, and the first and second hydraulic pressure chambers 6 are connected to each other.
No hydraulic pressure difference occurs between 6 and 70, and the power piston 46 does not move, so that no assisting torque is generated. On the other hand, when the steering wheel 28 is operated to rotate the steered wheels, the input shaft 22 rotates, and the torsion bar 30 is twisted by the rotation resistance of the output shaft 32. The phases are out of phase. Therefore, the first hydraulic chamber 66 or the second hydraulic chamber 70
Is communicated with the vane pump 56, and the power piston 4
6 moves to assist the steering torque. The rotary valve 12, the power cylinder 18, and the vane pump 56 constitute an assisting means.

The rotary valve 12 of the gear housing 20
A hydraulic reaction force device 16 is provided between the steering gear 14 and the steering gear 14. Torsion bar 3 on output shaft 32
The portion to which 0 is fixed is a large-diameter disc portion 74, which is fitted in the gear housing 20 so as to be liquid-tight and rotatable. On the disc part 74, four plungers 76 are provided on the input shaft 2.
It is fitted so as to be slidable in a direction perpendicular to the axis of the shaft 2. Of these four plungers 76, two pairs of plungers 76 are fitted concentrically and at positions deviated from the axial center of the input shaft 22, and are formed on the input shaft 22 in a radially outward direction. The projections 78 and 80 are sandwiched from both sides, and are urged toward the projections 78 and 80 by the hydraulic pressure supplied to the reaction force chamber 82 formed on the back surface thereof.

The reaction force chamber 82 is connected to the reservoir tank 60 by a liquid passage 86, and the liquid passage 86 is also provided.
And the liquid passage 54 connecting the rotary valve 12 and the vane pump 56 to each other, a diversion valve 88 is provided, and the working fluid discharged by the vane pump 56 is separately supplied to the rotary valve 12 and the reaction force chamber 82. It is supposed to do. A solenoid valve 90 is provided in a portion of the liquid passage 86 closer to the reservoir tank 60 than the flow dividing valve 88.
The solenoid valve 90 restricts the flow rate of the liquid passage 86 according to the magnitude of the exciting current of the solenoid.

The opening degree of the solenoid valve 90 increases as the exciting current of the solenoid increases, and the hydraulic fluid separated from the flow dividing valve 88 to the reaction force chamber 82 side is stored in the reservoir tank 6.
Since the pressure is easily returned to 0, the hydraulic pressure applied to the reaction force chamber 82 is reduced, the reaction force applied to the input shaft 22 by the plunger 76 is reduced, and the assisting torque of the steering torque is not reduced, resulting in agility. A good steering feeling can be obtained. On the contrary, as the exciting current of the solenoid becomes smaller, the opening becomes smaller, the hydraulic pressure supplied to the reaction force chamber 82 becomes higher, the reaction force applied to the input shaft 22 increases, the assisting torque is reduced, and it is heavy and stable. The steering feeling can be obtained.

The power steering computer 100 controls the power steering system.
The power steering computer 100 includes a steering torque sensor 40, a steering angular velocity sensor 42, and a vehicle speed sensor 10.
The detected value of 4 is input, and the solenoid exciting current of the solenoid valve 90 is output based on the input. The ROM stores a map defining the relationship between the vehicle speed shown in FIG. 3 and the excitation basic current of the solenoid valve 90. As is apparent from the figure, the higher the vehicle speed is, the smaller the solenoid excitation basic current is. As a result, as shown in FIGS. 5 and 6, when the vehicle speed is high, the hydraulic pressure of the power cylinder 18 is increased. Is low, the steering torque is heavy, and a stable steering feeling is obtained. On the other hand, when the vehicle speed is low, the hydraulic pressure of the power cylinder 18 is high and the steering torque is low, and a light steering feeling is obtained. .

As shown in FIG. 4, the ROM further defines the relationship between the value X calculated based on the steering torque and the steering angular velocity (this value X will be described later) and the solenoid excitation correction current Y. The map to be stored is stored,
The solenoid valve control routine shown by the flowchart in FIG. 1 is stored. The control of the solenoid valve 90 will be described below based on this flowchart.

First, in step S1 (hereinafter abbreviated as S1; the same applies to other steps), the vehicle speed V is read from the vehicle speed sensor 104. Next, S2 is executed, and the solenoid excitation basic current Ab for the vehicle speed V is calculated from the map which defines the relationship between the vehicle speed V and the solenoid excitation basic current Ab stored in the ROM. Subsequently, S3 is executed, the steering torque T is read, and the steering angular velocity S is read in S4. Then, in S5, the product of the steering torque T and the steering angular velocity S is multiplied by a negative constant k to obtain the solenoid excitation correction current. A value X for calculating Y is calculated.

The steering wheel 28 rotates in the direction intended by the driver, and the steered wheels move to the steering wheel 2.
When turning in the same direction as the rotation direction of 8, the steering torque T and the steering angular velocity S are in the same direction, and the positive and negative signs of the respective values of the steering torque T and the steering angular velocity S are the same. Therefore, the product has a positive value, but since the constant k has a negative value, X has a negative value.

When the steered wheels rotate to the position intended by the driver and the steering wheel 28 is held in the rotational position, the steering angular velocity S becomes 0 and the value of X becomes 0.

Further, when the steering wheel 28 rotates against the driver's intention, the value X becomes a positive value. When the steered wheels are rotated against the driver's intention due to unevenness of the road surface, changes in the friction coefficient of the road surface, the presence of obstacles, etc., the steering wheel 28 is driven by the driver's intention due to the torque applied from the steering wheel side. Rotates contrary to.
When the steered wheels rotate contrary to the driver's intention, when the steered wheels rotate in the direction opposite to the steering direction intended by the driver,
In some cases, the steering wheel 28 rotates in the same direction as the steered wheels due to the torque applied from the steered wheel side, while the driver prevents the rotation in the steering direction. Carry out corrective steering as much as possible,
The steering torque T and the steering angular velocity S are applied in order to apply the steering torque for rotating the steering wheel 28 in the opposite direction.
The directions of and are reversed, the signs of the respective detected values are reversed and the product becomes negative, and the value X becomes positive.

When the value X is calculated, S6 is executed,
The solenoid excitation correction current Y is calculated based on a map that defines the relationship between the value X and the solenoid excitation correction current Y stored in the ROM. Then, in S7, the solenoid excitation correction current Y is added to the solenoid excitation basic current Ab previously calculated in S2 to calculate the solenoid excitation current, which is output to the solenoid valve 90. Note that the solenoid excitation current has a lower limit of 200 mA,
It is calculated with 0 mA as the upper limit.

When the steering wheel 28 is rotated as intended by the driver, the value X is a negative value, so the solenoid excitation correction current Y is a negative value, and the solenoid excitation current is the solenoid excitation basic value. It is made smaller than the current Ab. The solenoid excitation basic current Ab is set to such a magnitude that the assisting torque corresponding to the vehicle speed V can be obtained by the subtraction of the correction current Y, and the steering wheel 28 can be operated with an appropriate response.

Further, when the steering wheel is turned to a desired position to stop the operation of the steering wheel 28 and the steering is held at that position, the value X becomes 0, so the solenoid excitation basic current Ab is corrected. Instead, it is directly supplied to the solenoid valve 90. At the time of holding the steering wheel 28 in the rotating position, an exciting current larger than that during the rotating operation is supplied to the solenoid valve 90, and the assisting torque is increased, so that the force required for holding the steering is small.
At the time of holding the steering wheel, the steered wheels try to return to the original position and apply a torque to the steering wheel 28 in the direction to return it to the neutral position. Therefore, a force is required to keep the steering wheel 28 in the rotating position. It will be reduced.

Further, when the steering wheel 28 rotates against the driver's intention and the value X becomes a positive value, the solenoid excitation correction current Y becomes a positive value. Therefore, the solenoid exciting current becomes larger than the solenoid exciting basic current Ab, and a large assisting torque is obtained, and the correction steering becomes easy.

As is apparent from the above description, in the present embodiment, the portion of the power steering computer 100 for storing S1 to S7 of the ROM and the portion of the CPU for executing those steps constitute the assisting torque control means. There is.

The solenoid excitation correction current may be changed according to the vehicle speed, the friction coefficient of the road surface, and the like. For example, when the vehicle speed is low, the response at the time of steering may be small, it is less affected by the unevenness of the road surface, etc., and even if correction steering is performed, the force thereof is small. In the graph shown, the scale value of the solenoid excitation correction current is reduced, and the scale value is increased when the vehicle speed is high. Further, when the friction coefficient of the road surface is small, the steering resistance becomes small, so the scale value of the solenoid excitation correction current is increased.

Further, in the above embodiment, the relationship between the value X and the solenoid excitation correction current Y is continuously defined by a curve, but may be defined stepwise by a straight line as shown in FIG.

In addition, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art without departing from the scope of the claims.

[Brief description of drawings]

FIG. 1 is a flowchart showing a solenoid valve control routine stored in a ROM of a computer that controls a power steering system according to an embodiment of the present invention.

FIG. 2 is a diagram showing the power steering device.

FIG. 3 is a graph showing a relationship between an excitation basic current for exciting a solenoid valve of the power steering device and a vehicle speed.

FIG. 4 is a graph for defining an excitation correction current for correcting the basic current of the solenoid valve.

FIG. 5 is a graph showing the relationship between the steering torque obtained in the power steering apparatus and the hydraulic pressure of the power cylinder, which is divided according to the vehicle speed.

FIG. 6 is a graph showing the relationship between vehicle speed and steering torque obtained in the power steering device.

FIG. 7 is a graph showing another aspect of defining a solenoid excitation correction current.

[Explanation of symbols]

 12 rotary valve 18 power cylinder 28 steering wheel 40 steering torque sensor 42 steering angular velocity sensor 56 vane pump 100 power steering computer

Claims (1)

[Claims] 1. A power steering apparatus comprising: an assisting means for assisting a steering torque applied to a steering wheel; a steering angular velocity detecting means for detecting a steering angular velocity of the steering wheel; and a steering torque of the steering wheel for the steering angular velocity. And a steering torque detecting means for detecting the same direction as the same sign, and the assisting torque is decreased when the product of the detected steering angular velocity and the steering torque is positive, and the assisting torque is increased when the product is negative. A power steering apparatus comprising: a torque control unit.