JP2938599B2 - Vehicle steering control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering control device capable of changing a gear ratio which is a ratio of a wheel steering angle to a steering wheel steering angle.

[0002]

2. Description of the Related Art Conventionally, a steering control device for a vehicle of this type has been provided in a steering force transmission path between a steering handle and a tie rod as disclosed in, for example, Japanese Patent Application Laid-Open No. 61-12076. A gear ratio variable mechanism for changing a gear ratio (steering wheel steering angle / wheel turning angle), a vehicle speed detecting means for detecting a vehicle speed, and a controller (control means) for inputting a signal from the vehicle speed detecting means and outputting a control signal; An actuator that receives the output signal of the controller to operate the variable gear ratio mechanism, so that the rate of change of the gear ratio with respect to the vehicle speed in the low vehicle speed range is larger than that in the high vehicle speed range under the control of the controller. What has been known is known.

[0003]

In the prior art, the boundary between the low vehicle speed region and the high vehicle speed region is determined by empirical rules and the like, and the turning characteristics in the low vehicle speed region and the high vehicle speed region are determined by the boundary. There is a uniform demand for the conflicting nature of stability in vehicles.However, drivers may place emphasis on turning performance or stability based on their own driving experience. Couldn't answer enough. Further, since the driver usually wants the vehicle to respond more quickly as the steering speed of the steering wheel is higher, it is desirable to change the magnitude of the gear ratio according to the steering wheel speed even at the same vehicle speed.

The present invention has been made in view of the above point, and a first object of the present invention is to appropriately change the gear ratio in accordance with the steering speed of a steering wheel together with the vehicle speed, and to reduce the gear ratio in a low vehicle speed range. It is an object of the present invention to provide a vehicle steering control device capable of ensuring a high degree of turning performance and stability in a high vehicle speed range.

A second object of the present invention is to improve the turning performance in a low vehicle speed range and the stability in a high vehicle speed range while allowing a driver to have a choice of a gear ratio. Is provided.

[0006]

SUMMARY OF THE INVENTION In order to achieve the first object, a first aspect of the present invention is a steering control apparatus for a vehicle which turns a wheel at a predetermined gear ratio with respect to a steering angle during steering. A vehicle speed detecting means for detecting a vehicle speed, a steering speed detecting means for detecting a steering speed of a steering wheel, a wheel turning means for turning a wheel, and at least two high and low values defined as a function expression using the vehicle speed as a parameter. A gear ratio characteristic that is lower than a first predetermined vehicle speed, a lower gear ratio characteristic at a second predetermined vehicle speed higher than the first predetermined vehicle speed, and a higher gear ratio characteristic at a second predetermined vehicle speed higher than the first predetermined vehicle speed; A gear ratio selecting means for selecting a gear ratio characteristic in accordance with the steering speed of the steering wheel detected by the steering speed detecting means between the second predetermined vehicle speed and the selecting means; A configuration and control means for controlling the wheel steering means based on the-option has been gear ratio characteristics.

According to a second aspect of the present invention, in accordance with the first aspect of the present invention, the gear ratio selecting means operates the steering wheel between a first predetermined vehicle speed and a second predetermined vehicle speed. The lower gear ratio characteristic is selected when the speed is higher than a predetermined steering wheel steering speed, and the higher gear ratio characteristic is selected when the steering wheel speed is lower than the predetermined steering wheel steering speed. According to a third aspect of the present invention, in the second aspect, the predetermined steering wheel steering speed is set to a larger value as the vehicle speed increases.

In order to achieve the second object, the invention according to a fourth aspect of the present invention is a steering control device for a vehicle that turns a wheel at a predetermined gear ratio with respect to a steering angle when steering a steering wheel. A vehicle speed detecting means for detecting, a wheel turning means for turning the wheel, and at least two high and low gear ratio characteristics defined as a function formula using the vehicle speed as a parameter, and a lower gear ratio below a first predetermined vehicle speed. The characteristic is a higher gear ratio characteristic at a second predetermined vehicle speed higher than the first predetermined vehicle speed, and a higher gear ratio characteristic according to a manual switch selection signal between the first predetermined vehicle speed and the second predetermined vehicle speed. A configuration including gear ratio selecting means for selecting gear ratio characteristics, and control means for controlling the wheel steering means based on the gear ratio characteristics selected by the selecting means. To.

[0009]

According to the above-mentioned structure, according to the first aspect of the present invention,
In a low vehicle speed range equal to or lower than the first predetermined vehicle speed, the lower gear ratio characteristic is selected by the gear ratio selection means, and the control means controls the wheel steering means based on the selected gear ratio characteristic, whereby the steering wheel The wheels are steered quickly with respect to steering, and the turning performance of the vehicle is enhanced. Further, in a high vehicle speed range equal to or higher than the second predetermined vehicle speed, a higher gear ratio characteristic is selected by the gear ratio selection means, and the control means controls the wheel steering means based on the selected gear ratio characteristic, The wheels are steered gently in response to the steering of the steering wheel, thereby increasing the stability of the vehicle.

Further, in a middle vehicle speed range between the first predetermined vehicle speed and the second predetermined vehicle speed, a gear ratio characteristic is selected according to the steering speed of the steering wheel. By controlling the rudder means, the turning of the wheels is performed with a gear ratio corresponding to both the vehicle speed and the steering wheel steering speed, and the turning performance and the stability are further enhanced. In this case, in particular, when the steering speed of the steering wheel is higher than the predetermined steering wheel steering speed, the lower gear ratio characteristic is obtained when the steering ratio of the steering wheel is higher than the predetermined steering wheel steering speed. Since the characteristics are selected, the turning performance can be enhanced according to the driver's requirements.

According to the present invention, in a middle vehicle speed range between the first predetermined vehicle speed and the second predetermined vehicle speed, a gear ratio characteristic is selected according to a selection signal of a manual switch. When the control means controls the wheel turning means based on the characteristic, the steering of the wheels is performed with emphasis on turning characteristics or stability in accordance with the driver's request.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an overall configuration of a steering device of a vehicle provided with a steering control device according to an embodiment of the present invention, wherein 1 is a steering handle, and 2 is a steering shaft having one end connected to the steering handle 1. The other end of the steering shaft 2 is linked to a steering rod 4 extending in the vehicle width direction via a rack & pinion 3, and the rotational force of the steering shaft 2 is controlled by the rack & pinion 3. It is converted as a direction (vehicle width direction) movement. Left and right ends of the steering rod 4 are connected to left and right wheels 6 via tie rods 5 and 5, respectively.
L, 6R, and both wheels 6L, 6R are steered left and right by the axial movement of the steering rod 4.

The steering rod 4 is provided with a steering actuator 11 composed of a hydraulic cylinder using the rod 4 as an operating rod. The steering actuator 11 has a left-turning hydraulic chamber 13 and a right-turning hydraulic chamber 14 partitioned by a piston 12. The two hydraulic chambers 13, 14 are respectively connected via oil passages 15, 16. It is connected to the servo valve 17. The servo valve 1
Reference numeral 7 denotes an electromagnetic type 4-port 3-position switching valve. The servo valve 17 has an oil supply passage 18 and a drain passage 19 for introducing pressure oil discharged from an oil pump (not shown).
Is connected. When the servo valve 17 is switched from the neutral position to the position a, the pressure oil from the oil pump is supplied to the left-turning hydraulic chamber 13 through the oil supply passage 18 and the oil passage 15, and the right-turning hydraulic chamber 13 is turned on. When the pressure oil in the hydraulic chamber 14 is drained, the steering rod 4 moves to the right as viewed in the traveling direction of the vehicle, and the left and right wheels 6L and 6R are steered to the left. On the other hand, when the servo valve 17 is switched from the neutral position to the position b, the pressure oil from the oil pump is supplied to the right turning hydraulic chamber 14 via the oil supply passage 18 and the oil passage 16,
When the hydraulic oil in the left steering hydraulic chamber 13 is drained, the steering rod 4 moves to the left as viewed in the traveling direction of the vehicle, and the left and right wheels 6L and 6R are steered rightward.

The steering shaft 2 is divided into two parts 2a and 2b at an intermediate portion in the axial direction, while the two divided shafts 2a and 2b
1 are connected so as to be freely connected and disconnected. The column lock 21 switches connection and disconnection by supplying and discharging pressure oil. The column lock 21 is connected to an electromagnetic three-port two-position switching valve 23 via an oil passage 22. Supply passage 1
8 and the drain passage 19 are connected. When the switching valve 23 is at the position a shown in the drawing, the pressure oil in the column lock 21 is drained, so that the column lock 21 is separated and the rotational force between the divided shafts 2a and 2b is reduced. Transmission is interrupted. On the other hand, when the switching valve 23 is switched to the position “b”, the pressure oil from the oil pump is supplied into the column lock 21 via the oil supply passage 18 and the oil passage 22 so that the column lock 21 is locked. Transmission of rotational force is performed between the divided shafts 2a and 2b. With the above-described configuration, the wheel steering unit 24, which is a mechanical component of the steering device that steers the left and right wheels 6L and 6R, is configured.

The servo valve 17 and the switching valve 23 are
Switching is controlled by a control signal from the control unit 31, respectively. The control unit 31 includes a steering angle signal θ from a steering angle detecting means (steering angle sensor) 32 for detecting a steering angle of the steering wheel 1 and a vehicle speed signal from a vehicle speed detecting means (vehicle speed sensor) 33 for detecting a vehicle speed. V and a yaw rate signal か ら from a yaw rate detecting means 34 for detecting the yaw rate of the vehicle.

FIG. 2 is a gear ratio characteristic diagram used for the switching control of the servo valve 17 and the switching valve 23 by the controller unit 31. In this figure, the gear ratio characteristic is provided with two high and low gear ratio characteristics A and B defined as a linear function equation with the vehicle speed V as a parameter, and the lower gear ratio characteristic below the first predetermined vehicle speed V1. B is a higher gear ratio characteristic A at a second predetermined vehicle speed V2 higher than the first predetermined vehicle speed V1.
However, the steering speed (dθ / d) of the steering wheel 1 is between the first predetermined vehicle speed V1 and the second predetermined vehicle speed V2.
t, hereinafter simply referred to as dθ), one of the two gear ratio characteristics A and B is selected, and the control valve of the wheel steering means 24 is selected based on the selected gear ratio characteristics A or B. 17, 23 are controlled. Here, as the selection of the gear ratio characteristics A and B according to the steering speed (dθ) of the steering wheel between the first predetermined vehicle speed V1 and the second predetermined vehicle speed V2, for example, as shown in FIG.
When the steering speed (dθ) of the steering wheel is higher than the predetermined steering speed, the lower gear ratio characteristic B is selected,
When the vehicle speed is lower than the predetermined steering wheel speed, the higher gear ratio characteristic A is selected. The steering speed (dθ) of the steering wheel 1 is obtained by differentiating the steering angle θ detected by the steering angle sensor 32 with a differentiating circuit 35 built in the control unit 31. And steering angle sensor 3
2 constitutes a steering speed detecting means 36 for detecting the steering wheel steering speed.

FIG. 4 is an example of a flowchart for selecting the gear ratio characteristics A and B as described above. In this selection flow, first, after starting, step S1
It is determined whether the actual vehicle speed Vn is equal to or lower than the first predetermined speed V1. If the determination is YES or lower, the gear ratio characteristic B is selected in step S2 and the routine returns. On the other hand, if the determination is NO or more than the predetermined speed V1, it is determined in step S3 whether or not the actual vehicle speed Vn is less than or equal to the second predetermined speed V2. At S5, the gear ratio characteristic A is selected and the routine returns.

If the determination in step S3 is YES
, Ie, when the actual vehicle speed Vn is between the first predetermined speed V1 and the second predetermined speed V2, step S
In step 4, it is determined whether or not the absolute value (| dθHn |) of the actual steering wheel speed is higher than a predetermined steering wheel speed (dθHV) determined corresponding to the current vehicle speed Vn shown in FIG. Is greater than YES in step S2
The gear ratio characteristic B is selected at step S5, and when the determination is NO, the gear ratio characteristic A is selected at step S5. The gear ratio selection means 37 is configured by the above selection flow, and the gear ratio selection means 37 is built in the control unit 31 and the control unit 31 includes the gear ratio selection means 3
A control means 38 for controlling the wheel turning means 24 based on the gear ratio characteristic selected in 7 is built in.

Therefore, in the above embodiment, when the actual vehicle speed Vn is in the low vehicle speed range below the first predetermined vehicle speed V1, the lower gear ratio characteristic B is selected by the gear ratio selection means 37, and the selected gear ratio is selected. The control valves 17 and 23 of the wheel turning means 24 are controlled based on the characteristic B, so that the steering wheel 1
L and 6R are quickly steered, and the turning performance of the vehicle can be improved. When the actual vehicle speed Vn is higher than the second predetermined vehicle speed V2, the higher gear ratio characteristic A is selected by the gear ratio selection means 37, and the wheel steering means is selected based on the selected gear ratio characteristic A. Since the steering wheel 24 is controlled, the wheels 6L and 6R are gently steered by the steering of the steering handle 1, and the stability of the vehicle can be improved.

Further, when the actual vehicle speed Vn is in the middle vehicle speed range between the first predetermined vehicle speed V1 and the second predetermined vehicle speed V2, the lower the gear ratio characteristic B is, the higher the steering speed dθHn of the steering wheel 1 is. Selected and the steering speed dθHn
Is slower, the higher gear ratio characteristic A is selected.
Steering characteristics according to the driver's intention can be obtained, and it is possible to achieve both turning performance and stability at a high level.

It should be noted that the present invention is not limited to the above-described embodiment, but includes various other modifications.
For example, in the above embodiment, when the vehicle speed is in the middle vehicle speed range between the first predetermined vehicle speed V1 and the second predetermined vehicle speed V2, the gear ratio selection means 37 sets the steering speed dθ of the steering wheel 1
When Hn is fast, the lower gear ratio characteristic B is selected, and when Hn is slower, the higher gear ratio characteristic A is selected. In the present invention, the selection of the gear ratio characteristics A and B is performed according to a selection signal from a manual switch. That is, a configuration may be adopted in which any selection can be made by manual operation. In this case, the driver can change the selection of the gear ratio characteristic, and the usability can be improved.

[0023]

As described above, according to the first aspect of the present invention, the lower gear ratio characteristic in the low vehicle speed range, the higher gear ratio characteristic in the high vehicle speed region, and the steering wheel speed in the middle vehicle speed region. The gear ratio characteristics are automatically selected accordingly, and the wheels are steered in accordance with the steering angle based on the selected gear ratio characteristics, thereby achieving high turning performance and stability at a high level. be able to.

In particular, in the case of the invention according to claims 2 and 3,
In the middle vehicle speed range, high and low gear ratio characteristics are automatically selected according to the steering speed of the steering wheel, so that turning performance can be effectively improved in response to a driver's request.

According to the fourth aspect of the present invention, the lower gear ratio characteristic is automatically selected in a low vehicle speed range, and the higher gear ratio characteristic is automatically selected in a high vehicle speed range. The gear ratio characteristic is selected, and the wheel is steered in accordance with the steering angle based on the selected gear ratio characteristic.This ensures both turning performance in a low vehicle speed range and stability in a high vehicle speed range. However, it is possible to change the gear ratio characteristics and improve the usability.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a vehicle steering apparatus according to an embodiment of the present invention.

FIG. 2 is a gear ratio characteristic diagram.

FIG. 3 is a map diagram used for selecting a gear ratio characteristic.

FIG. 4 is a flowchart used for selecting a gear ratio characteristic.

[Explanation of symbols]

 24 Wheel turning means 33 Vehicle speed detecting means 36 Steering speed detecting means 37 Gear ratio selecting means 38 Control means

Continuation of the front page (56) References JP-A-62-15172 (JP, A) JP-A-61-193969 (JP, A) JP-A-61-232963 (JP, A) JP-A-60-78869 (JP) JP-A-60-71372 (JP, A) JP-A-63-247168 (JP, A) JP-A-63-240476 (JP, A) JP-A-62-46774 (JP, A) (58) Surveyed field (Int. Cl. ⁶ , DB name) B62D 6/00

Claims (4)

(57) [Claims] 1. A steering control device for a vehicle that turns a wheel at a predetermined gear ratio with respect to a steering angle during steering of a steering wheel, a vehicle speed detecting means for detecting a vehicle speed, and a steering speed for detecting a steering speed of a steering wheel. Detecting means, wheel turning means for turning the wheels, and having at least two high and low gear ratio characteristics defined as a function formula using the vehicle speed as a parameter, and a lower gear ratio characteristic at a first predetermined vehicle speed or less, A higher gear ratio characteristic is obtained at a second predetermined vehicle speed higher than the first predetermined vehicle speed, and a steering wheel speed detected by the steering speed detection means between the first predetermined vehicle speed and the second predetermined vehicle speed. A gear ratio selecting means for selecting a gear ratio characteristic according to the steering speed; and a control means for controlling the wheel steering means based on the gear ratio characteristic selected by the selecting means. Steering control apparatus for a vehicle characterized by comprising a means. 2. The steering system according to claim 1, wherein the gear ratio selecting means is configured to switch a steering wheel speed between a first predetermined vehicle speed and a second predetermined vehicle speed.
Is smaller than the specified steering wheel speed
Gear ratio characteristics, the steering speed of the steering wheel
If the steering speed is lower than the
2. The vehicle steering control device according to claim 1, wherein said steering characteristic is selected . 3. The steering wheel speed as set forth in claim 1, wherein the predetermined steering wheel speed is high.
The contract is characterized in that the
The vehicle steering control device according to claim 2. 4. A steering control device for a vehicle that turns a wheel at a predetermined gear ratio with respect to a steering angle during steering of a steering wheel, the vehicle speed detecting means detecting a vehicle speed, and the wheel turning means turning the wheel. And at least two high and low gear ratio characteristics defined as a function expression having the vehicle speed as a parameter, and a lower gear ratio characteristic at a first predetermined vehicle speed or less, and a second gear ratio characteristic higher than the first predetermined vehicle speed. A gear ratio selecting means for selecting a gear ratio characteristic higher than the vehicle speed and a gear ratio characteristic corresponding to a selection signal of a manual switch between the first predetermined vehicle speed and the second predetermined vehicle speed; And a control means for controlling the wheel steering means based on the gear ratio characteristics obtained.