JP3285373B2 - 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 for controlling steering.

[0002]

2. Description of the Related Art Conventionally, lateral acceleration and yaw rate are generated by turning a steering wheel provided on a vehicle.

[0003]

When such a vehicle is driven, the lateral acceleration and the yaw rate generated by the vehicle speed are different even if the driver steers the steering at the same steering angle (see FIG. 11). The vehicle may become unstable. Conventionally, in order to avoid an unstable state of the vehicle, the driver has to perform additional steering and return steering by sensing the lateral acceleration and the yaw rate sensuously. Therefore, there is a problem that not only the driver is required to be used and highly skilled, but also the steering operation itself is a heavy burden.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle steering control device capable of reducing a driver's steering operation load.

[0005]

In order to achieve the above object, a steering control device for a vehicle according to the present invention comprises a vehicle speed detecting means for detecting a vehicle speed, and a wheel steering angle for generating a wheel steering angle in response to a steering operation of the steering. Generating means, a steering gear for transmitting steering operation of the steering wheel at a predetermined ratio to the wheel steering angle generating means, and changing the ratio of the steering gear according to the vehicle speed, thereby changing the behavior during turning of the vehicle. The vehicle's lateral acceleration, which is the state quantity that occurs
Setting means for setting the yaw rate to a predetermined condition, wherein the setting means sets the steering speed regardless of the vehicle speed.
The lateral acceleration of the vehicle or the yaw
The steering gear so that the rate is uniquely determined.
And set the steering angle of the steering.
Equipped with limiting means for limiting the steering angle so that the vehicle can run stably
Rukoto is referred to as the gist thereof.

[0006]

[0007]

According to the above construction, by changing the ratio of the steering gear according to the vehicle speed to the wheel steering angle corresponding to the steering operation of the steering, the lateral acceleration or the yaw rate generated by the change in the behavior at the time of turning the vehicle becomes irrelevant. Therefore, in order to avoid the unstable state of the vehicle, the driver may perform the steering operation without considering the vehicle speed. At this time, the limiting means is a lateral acceleration with respect to the steering amount.
Or the unique relationship between the yaw rate generation value and the vehicle speed
Within the area where Therefore, the stable area of the vehicle
Can be maintained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. As shown in FIG. 1, the steering control device 1
A steering wheel 2, a snearing gear device 5 in which the rotation of the steering wheel 2 is input via a handle shaft 3 and an intermediate shaft 4, and a tie rod for transmitting the left and right steering wheels 6.6 by the output of the gear device 5 8 and the like.

Between the handle shaft 3 and the intermediate shaft 4,
A variable steering gear ratio mechanism that changes the ratio (steering gear ratio: N = θ / δ) of the rotation angle (steering angle: θ) of the steering wheel 2 to the steering angle (wheel steering angle: δ) of the wheels 6.6. 10 are provided.

An actuator 7 for operating the variable steering gear ratio mechanism 10 and an electronic control unit (hereinafter referred to as “ECU”) 11 for controlling the actuator 7 are provided. This actuator 7
Specifically, an electric motor, a hydraulic motor, a hydraulic cylinder, a pneumatic cylinder, or the like can be used. The ECU 11 stores a vehicle speed V from a vehicle speed sensor 12 that detects the vehicle speed of the vehicle.
And signals S ₁ indicating a is adapted to be input.

The structure of the above-described variable mechanism 10 is disclosed, for example, in JP-A-63-240476. Here, the ECU 11 sets the steering gear ratio N in accordance with the vehicle speed V indicated by the signal S ₁ from the vehicle speed sensor 12 based on a predetermined control map shown in FIG.
The drive signal S ₃ is output to the actuator 7 so that 0 becomes the set steering gear ratio N.

In this case, the reciprocal characteristic of the steering gear ratio N with respect to the vehicle speed V is set so that the reciprocal of the steering gear ratio N decreases as the vehicle speed V increases. Is uniquely determined regardless of the vehicle speed V. That is, by setting the steering gear ratio N according to the control map shown in FIG.
Can be obtained.

Next, control processing by the ECU 11 will be described with reference to the flowchart of FIG.
Then, at step S2, a target steering gear ratio corresponding to the vehicle speed V is calculated from a steering gear ratio control map (see FIG. 2). In step S3, the operation amount of the actuator 7 corresponding to the target steering gear ratio and the drive signal S ₄ output to the actuator 7
Is calculated. In step S4 outputs a drive signal S ₄ calculated in step S3 to the actuator 7.

With the above control, the steering gear ratio N changes according to the vehicle speed V. This results in the same steering angle θ
However, the wheel steering angle δ is different, and the lateral acceleration G generated in the vehicle does not depend on the vehicle speed V, and the lateral acceleration G can be represented by a function of only the steering angle θ. Therefore, it is very easy for the driver to predict an appropriate steering angle at the time of turning. Furthermore, if the driver uses the lateral acceleration G as feedback information, the steering angle θ
Since the information itself can be used as feedforward information, it is possible to reduce the time required for judgment and delay in transmitting information, greatly improve the responsiveness and controllability (positioning accuracy) of steering operations, and reduce the load on the driver. Can be. In addition, since the turning limit can be easily predicted, safety can be improved.

In this embodiment, the vehicle speed sensor 1
2 corresponds to the vehicle speed detecting means, the variable steering gear ratio mechanism 10 corresponds to the wheel steering angle detecting means, and the flowchart of FIG. 4 corresponds to the setting means.

Next, a second embodiment will be described. First
In the embodiment, by changing the steering gear ratio N according to the vehicle speed V, the lateral acceleration G generated in the vehicle is changed to the vehicle speed V.
The second embodiment is characterized in that the purpose is achieved by making the tire air pressure variable.

FIG. 5 is a schematic diagram showing the configuration of the second embodiment. The configuration of the second embodiment is partially the same as that of the first embodiment, and the same components are denoted by the same reference numerals and description thereof is omitted.

Referring to FIG. 5, the tire characteristic variable actuator 14 has a pressure source and a tire pressure control valve as disclosed in, for example, Japanese Patent Application Laid-Open No. 2-169310. By changing the air pressure of a certain tire 15, the lateral force characteristics of the tire 15 are changed. This tire characteristic variable actuator 14 is provided with an ECU
13 is controlled by a signal.

The ECU 13 sets the tire pressure in accordance with the vehicle speed V indicated by the signal S ₁ from the vehicle speed sensor 12 based on a predetermined control map.
Air pressure of 5 is set pneumatically as to output a driving signal S ₃ to the tire characteristic variable actuator 14.

In this case, the air pressure characteristic of the tire 15 with respect to the vehicle speed V is set so that the air pressure increases as the vehicle speed V increases. As a result, during high-speed running, the air pressure of the tire 15 increases and the lateral force generated by the tire 15, that is, the lateral acceleration G generated by steering is reduced, so that the lateral acceleration G generated even when the steering is large is small. On the other hand, when the vehicle is running at a low speed, the air pressure of the tire 15 decreases to increase the lateral acceleration G generated by the steering.
The lateral acceleration G that occurs even when the steering is small is large.

Next, the control process by the ECU 13 will be described with reference to the flowchart of FIG.
In step S12, the vehicle speed V is read, and then in step S12, the vehicle speed V is read.
Is calculated according to the target air pressure of the tire 15. The operation amount of the tire varying actuator 14 corresponding to the target pressure calculated in step S13, step S12 and calculates a drive signal S ₃ to be output to the tire varying actuator 14. In step S14 outputs a drive signal S ₃ calculated in step S13 the tire varying actuator 14.

Thus, the air pressure of the tire 15 changes according to the vehicle speed V. Therefore, as in the first embodiment, it is easy to predict an appropriate steering angle at the time of turning, and the responsiveness and controllability of the driver's steering operation are greatly improved, so that the steering load can be reduced.

In this embodiment, the vehicle speed sensor 1
2 corresponds to vehicle speed detecting means, the tire characteristic variable actuator 14 corresponds to wheel steering angle detecting means, and the flowchart in FIG. 6 corresponds to setting means.

Next, a third embodiment will be described. The configuration of the third embodiment is also partially similar to the first embodiment, and the same components are denoted by the same reference numerals and description thereof will be omitted. 7 and 8 show the configuration of the third embodiment. FIG. 7 shows the third
FIG. 7 is a schematic view showing the configuration of the embodiment, and FIG. 7 is a sectional view taken along the line AA of FIG.

The steering angle sensor 17 detects the steering angle θ of the steering handle 2 and outputs a steering angle signal S ₄ to the ECU 18.
Output to The steering angle limiting mechanism 16 includes a steering angle control pin 16b attached to the handle shaft 3, a plate 16c fixed to the vehicle body (not shown) and not rotating, and a stopper 1 that is provided on the plate 16c and can protrude in the handle shaft 3 direction.
6d, a solenoid 16e for projecting the stopper 16d in the direction of the handle shaft 3. And ECU
When the steering angle limiting mechanism 16 is driven by a signal from 18, the stopper 16d protrudes in the direction of the handle shaft 3 as shown in FIG. 11, and the rotation of the handle shaft 3 allows the steering angle control pin 16b and the stopper 16d to abut. It becomes a state. This prevents the steering handle 2 from being rotated from the neutral position by θ _L or more. Here, θ _L is a limit steering angle at which the vehicle can run stably, and is about 162 ° in the present embodiment.

The ECU 18 changes the steering gear ratio N in accordance with the vehicle speed V indicated by the signal S ₁ from the vehicle speed sensor 12 as shown in FIG.
And sets on the basis of a predetermined control map shown in, and outputs a drive signal S ₃ to the actuator 7 as the steering variable mechanism portion 10 is set the steering gear ratio N. Further, it is determined whether or not to drive the steering angle limiting mechanism 16 in accordance with the steering angle θ indicated by the signal S ₄ from the steering angle sensor 17.

Next, control processing by the ECU 18 will be described with reference to a flowchart. The control process for the actuator 7 by the ECU 18 is as shown in FIG. 4 as in the first embodiment. Steering angle limiting mechanism 1 by ECU 18
FIG. 9 shows a control process for No. 6.

First, in step S21, the steering angle θ is read, and then, in step S22, the steering angle θ becomes (θ _L -Δθ).
It is determined whether or not this is the case. If NO is determined in step S22, the control ends. On the other hand, if YES is determined in step S22, the process proceeds to step S23. In step S23, a drive signal is output to the steering angle limiting mechanism 16. Then, the solenoid 16d of the steering angle limiting mechanism 16
And the stopper 16c projects. As a result, the rotation of the handle shaft 3 is stopped, and the driver cannot steer the steering handle 2 from the neutral position beyond the steering angle θ _L.

As described above, in the third embodiment, in addition to the configuration of the first embodiment, the steering angle sensor 17 and the steering angle limiting mechanism 16 for preventing a steering input exceeding the limit of the vehicle are provided. In the steering prohibited area where the driver has set the angle θ _L or more from the neutral position of the steering wheel 2 (see FIG. 10).
Can not steer, and an accident due to excessive steering can be prevented.

In the third embodiment described above, the steering angle limiting mechanism 16 corresponds to limiting means. In the third embodiment, the stopper 16c may be always protruded, instead of being protruded by the control of the ECU 18. In the case of this configuration, the steering angle sensor 17 can be omitted.

Although the first to third embodiments have been described above, the present invention is not limited to the above-described embodiment.
Various modifications can be made as follows, for example, without departing from the spirit of the invention.

In the control map shown in FIG. 2, the relationship between the steering angle θ and the yaw rate may be uniquely determined regardless of the vehicle speed V. In the first embodiment, the variable steering gear ratio mechanism 10 may be a continuously variable transmission such as a CVT or a ring cone.

In the first embodiment, an auxiliary steering actuator, a steering angle sensor, a mechanism for transmitting a steering angle to the auxiliary steering actuator, etc. are provided instead of changing the steering gear ratio, and the wheels are assisted by the auxiliary steering actuator. The same effect can be obtained by steering.

A wheel speed sensor, an engine speed sensor or the like may be used as the vehicle speed sensor. In the second embodiment, not only the tire pressure but also the contact area with the road surface, wheel alignment, and the like may be changed.

[0035]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a first embodiment.

FIG. 2 is a steering gear ratio control map.

FIG. 3 is a characteristic diagram showing a relationship between a steering angle and a vehicle lateral acceleration.

FIG. 4 is a flowchart showing a control process by an ECU 11;

FIG. 5 is a schematic diagram showing a configuration of a second embodiment.

FIG. 6 is a flowchart showing a control process by the ECU 13.

FIG. 7 is a schematic diagram showing a configuration of a third embodiment.

FIG. 8 is a sectional view taken along line AA of FIG. 10;

FIG. 9 is a flowchart showing a control process by the ECU 18.

FIG. 10 is a characteristic diagram illustrating a relationship between a steering angle and a vehicle lateral acceleration.

FIG. 11 is a characteristic diagram illustrating a relationship between a steering angle and a vehicle lateral acceleration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Steering gear ratio variable mechanism part 11 ECU 12 Vehicle speed sensor 13 ECU 14 Tire characteristic variable actuator 16 Steering angle limiting mechanism part 18 ECU

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Nomura 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (72) Inventor Kazunori Shimokawa 1-1-1, Showa-cho, Kariya-shi, Aichi Nihon Denso Co., Ltd. (56) References JP-A-3-7663 (JP, A) JP-A-1-104864 (JP, U) JP-A-58-68371 (JP, U)

Claims (1)

(57) [Claims] 1. A vehicle speed detecting means for detecting a vehicle speed; a wheel steering angle generating means for generating a wheel steering angle in response to a steering operation of a steering; Setting means for setting a lateral acceleration or a yaw rate of a vehicle, which is a state quantity generated by a change in behavior at the time of turning a vehicle, to a predetermined condition by changing a ratio of the steering gear to be transmitted by the steering gear according to the vehicle speed. And the setting means is configured to control the stearing regardless of the vehicle speed.
The vehicle's lateral acceleration or yaw
The steering gear ratio is set so that the speed
And the steering angle of the steering
Equipped with a limiting means for limiting the steering angle to allow the vehicle to travel stably.
And a steering control device for a vehicle.