JPH0899647A - Steering assisting device for vehicle - Google Patents

Abstract

PURPOSE: To propose a steering assisting device for a vehicle that can obtain maneuverablity corresponding to the demand of a driver during turning travel or the like. CONSTITUTION: A steering assisting device having a steering assisting means 20 for assisting steering operation performed by a driver is provided with steering state detecting means 41, 42 for detecting the steering state of the driver, and a control means 40 for controlling the steering assist force of the steering assisting means 20 on the basis of the detection results T, θ of the steering state detecting means 41, 42. In the case of the steering state being the specified value or more, the steering assist force is controlled by the steering assisting means 20, and the steering assist starting time of the steering assisting means 20 is controlled on the basis of the steering state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering assist device, and more particularly to a vehicle steering assist device for controlling a steering assist start timing based on a steering operation of a driver.

[0002]

2. Description of the Related Art A conventional steering assist device is generally provided with an assisting means connected to a steering wheel transmission path for assisting steering of the steering wheel and a control means for controlling the assisting means. Automatically controls the assisting force of the assisting means based on the steering state of the driver and the traveling state of the vehicle.

As such a steering assist device, for example,
As disclosed in Japanese Unexamined Patent Publication No. 1-175569, there is one in which the assist force is set to be larger as the steering torque of the driver is larger, and the increase rate thereof is made smaller to improve the running stability as the vehicle speed is higher. . Specifically, the steering assist force target value in the steering direction corresponding to the steering force applied to the steering wheel and the return assist force target in the return direction corresponding to the steering angle given to the steering wheel and the frictional condition of the road surface. Values are set individually, and the command value is calculated based on the steering assist force target value and the return assist force target value, and accurate steering assist control is performed regardless of the frictional condition of the road surface. It is known that the movement of the steering makes it difficult to cause a dangerous operation such as the movement of the steering being too fast contrary to the driver's expectation.

Further, as disclosed in Japanese Patent Application Laid-Open No. 61-81866, there is one provided with a control circuit for increasing the dead zone in which the auxiliary torque in the power steering is not generated as the vehicle speed increases.

[0005]

However, in the conventional power steering device, for example, assisting by the assist torque is not performed during high-speed turning of the vehicle, and accordingly, the steering force increases and the driver operates the steering wheel. There is a drawback that it makes you feel uncomfortable, such as becoming heavy.

Therefore, the present invention has been proposed in order to solve the above-mentioned drawbacks of the prior art, and an object of the present invention is to meet a driver's request during turning or the like in a vehicle equipped with a steering assist device. The present invention proposes a steering assist device for a vehicle that can obtain appropriate maneuverability.

[0007]

In order to solve the above problems and achieve the object, a vehicle steering assist device of the present invention has the following configuration. That is, a steering assist device for a vehicle having steering assist means for assisting a steering operation by a driver, the steering state detecting means detecting the steering state of the driver, and the detection result by the steering state detecting means. A control means for controlling the steering assisting force by the steering assisting means based on the above, when the steering state is a predetermined value or more,
The steering assist force is controlled by the steering assist means, and the start timing of the steering assist by the steering assist means is controlled based on the steering state.

Further, preferably, the steering state is a steering speed based on a steering torque generated by a steering operation. Further, it is preferable that the steering state is a steering speed based on a steering angle generated by a steering operation.

[0009]

As described above, since the vehicle steering assist system of this embodiment is constructed, the steering steering torque or steering angle of the driver is detected during turning and the like, and the steering assist is performed based on the detected steering steering torque or steering angle. By controlling the dead zone in which steering assistance is not performed in accordance with the steering state of the driver, maneuverability according to the driver's request, such as during turning, can be obtained.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. <Common Embodiment> The common part of each embodiment described below will be described below. FIG. 1 is a diagram showing details of a steering assist mechanism of an embodiment based on the present invention. In FIG. 1, the steering assist mechanism 20 includes a tie lot 2 that gives a turning angle to the left and right front wheels 1 according to a steering angle of a steering wheel 2 by a driver.
1, a rack 22 provided on the tie lot 21, and a steering mechanism including a pinion 23 for transmitting the steering angle of the steering wheel 2 to the wheels by being meshed with the rack 22 by being attached to the tip of the steering shaft 24. The electric power steering mechanism is provided with 30, and a driving force of the electric motor is used to give an auxiliary rotational force to the steering operation. This electric motor 30 has a clutch 3
The rotational force is transmitted to the gear 31 via 2 and the gear 31 is meshed with the vicinity of the tip of the steering shaft 24 to transmit the rotational force of the motor. The driving of the motor 30 and the engagement of the clutch 32 are controlled by the steering assist control unit 40. When the clutch 32 is engaged, the steering holding state is established, and when the clutch 32 is released, the so-called power steering release state is established. Further, the steering assist control unit 40 receives the steering torque T and the steering rudder angle θ from the steering torque sensor 41 and the steering rudder angle sensor 42 provided coaxially with the steering shaft 24, and detects the vehicle speed from the vehicle speed sensor 39. Signals are input, and the engagement of the clutch 32 and the drive torque of the electric motor 30 are controlled based on these signals. Further, in each of the embodiments described below, as shown in FIG. 11, steering assist is performed by matching the limit position A of control by the assisting device with the stopper position (mechanical limit position) of the torsion bar. Is configured as follows.

<First Embodiment> FIG. 2 shows a steering assist mechanism 20.
3 is a block diagram showing the control circuit configuration of FIG. In FIG. 2, a steering assist control unit 4 as a control means
0 calculates a steering steering speed Δθ based on a torque detection signal T input from the steering torque sensor 41,
A predetermined drive current A of the electric motor 30 as the assisting means is calculated based on the calculated value Δθ, the motor is driven with a predetermined torque, and steering assist of the left and right wheels is executed by the steering mechanism including the rack 22 and the pinion 23. .

FIG. 3 shows a control flow of the steering assist control unit 40 described in FIG. In FIG.
When the processing is started, the steering assist control unit 40 reads the steering torque T from the steering torque sensor 41 in step S2, and differentiates the steering torque in step S4 to calculate the steering speed Δθ. In step S6, it is determined whether the steering speed is equal to or higher than the first predetermined value θ ₁ . In step S6, if the first predetermined value θ ₁ or more (step S6
If YES, the process proceeds to step S8. In step S8, it is determined whether or not the steering speed is equal to or higher than a _second predetermined value θ ₂ (θ ₁ <θ ₂ ). When it is equal to or larger than the _second predetermined value θ _{2 in} step S8 (YES in step S8), the process proceeds to step S10. In step S10, the function map C of the current A and the steering torque T shown in FIG. 6 is selected based on the determination result of the steering speed Δθ. Then, in step S12, the map C
The drive current A of the electric motor 30 is set by using this. After that, in step S14, the drive current A is not supplied to the motor,
Steering Steering assistance is executed. On the other hand, step S6
If it is not equal to or larger than the first predetermined value θ ₁ (NO in step S6), the process proceeds to step S18. In step S18, the function map A of the current A and the steering torque T shown in FIG. 4 is selected based on the determination result of the steering speed Δθ, and the process proceeds to step S12. In step S8, the second predetermined value θ ₂
If not (NO in step S8), the process proceeds to step S16. In step S16, the function map B of the current A and the steering torque T shown in FIG. 5 is selected based on the determination result of the steering speed Δθ, and the process proceeds to step S12.

The function maps shown in FIGS. 4 to 6 are stored in a ROM (not shown) provided in the steering assist control unit. Further, the steering torque at which the assist is started is set to 15, 10, and 5 kgcm, and the steering torque at which the assist is started is set to be smaller as the steering angular velocity is faster than a predetermined value. In the function maps shown in FIGS. 4 to 6, the limit torque of the assist control is 70, 65, 6 depending on the set value of the steering torque for starting the assist.
Although it is changed to 0 kgcm, for example, as shown in FIG. 7, the steering torque for starting the assist may be changed to a predetermined value T _1, and if it is equal to or more than that value, a common function map may be used. By doing so, the steering can be turned in the same manner regardless of whether the steering torque is large or small, and thus it is possible to prevent the driver from excessively turning the steering.

<Second Embodiment> FIG. 8 is a block diagram showing a control circuit configuration of a steering assist mechanism 20 of a second embodiment. In FIG. 8, the steering assist control unit 40 according to the second embodiment uses the steering steering angle θ input from the steering angle sensor 42 instead of the torque detection signal T input from the steering torque sensor 41 to change the steering steering speed. Δ
θ is calculated, a predetermined drive current A of the electric motor 30 as an assisting means is calculated based on the calculated value Δθ, the motor is driven with a predetermined torque, and the steering mechanism including the rack 22 and the pinion 23 is used to control the left and right wheels. Execute steering assist.

FIG. 9 shows a control flow of the steering assist control unit 40 described in FIG. In FIG.
When the process is started, the steering assist control unit 40 detects the steering angle θ from the steering angle sensor 42 in step S20.
Is read and the steering angle Δθ is calculated by differentiating the steering angle θ in step S22. In step S24, it is determined whether the steering speed is equal to or higher than the first predetermined value θ ₁ . When it is equal to or larger than the _first predetermined value θ _{1 in} step S24 (step S24
If YES, the process proceeds to step S26. Step S2
At 6, it is determined whether the steering speed is equal to or higher than a _second predetermined value θ ₂ (θ ₁ <θ ₂ ). In step S26, the second predetermined value θ ₂
In the above case (YES in step S8), step S
Proceed to 28. In step S28, the function map C of the current A and the steering angle θ shown in FIG. 10 is selected based on the determination result of the steering speed Δθ. Then, in step S30, the drive current A of the electric motor 30 is set using the map C.
Then, in step S32, the drive current A is supplied to the motor to execute steering steering assistance. On the other hand, if it is not equal to or larger than the first predetermined value θ ₁ in step S24 (step S24).
If NO in step 24), the process proceeds to step S34. Step S
At 34, the function map A shown in FIG. 10 is selected based on the determination result of the steering speed Δθ, and the process proceeds to step S30. If it is not equal to or greater than the second predetermined value θ _{2 in} step S26 (NO in step S26), the process proceeds to step S36. In step S36, the function map B shown in FIG. 10 is selected based on the determination result of the steering speed Δθ.
Proceed to 30.

(Effects of Embodiment) According to the steering assist device of this embodiment described above, the steering torque or the steering angle generated by the steering operation of the driver is detected, and the steering assist mechanism is operated based on the detection result. Since the steering assist force is controlled and the start timing of the steering assist by the steering assist mechanism is controlled based on the steering state of the driver, it is possible to obtain maneuverability according to the driver's request during turning. It is possible to prevent the steering wheel from being cut too much.

Further, as described with reference to FIG. 11, since the steering assist is performed by matching the limit position of the control by the assisting means and the mechanical limit position, it is assumed that the driver turns the steering at a large steering angle. It is possible to eliminate the feeling of strangeness, such as the handle suddenly becoming heavy during the operation. Modifications The present invention can be variously modified without departing from the spirit thereof.

For example, the present invention is not limited to electric power steering, but hydraulic power steering is also applicable. In this case, the hydraulic pressure introduced into the power cylinder for controlling the hydraulic pressure may be changed by the flow rate control valve to generate the assist force, which can be realized by replacing the motor drive current value A with the target flow rate value V. Further, the number of function maps used in the first embodiment is not limited to three, and three or more function maps may of course be prepared.

[0019]

As described above, according to the vehicle steering assist system of the present invention, the steering steering torque or steering angle of the driver is detected during turning, and the steering assist is performed based on the detected steering steering torque or steering angle. By controlling the dead zone in which steering assistance is not performed in accordance with the steering state of the driver, maneuverability according to the driver's request, such as during turning, can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing details of a steering assist mechanism according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a control circuit configuration of a steering assist mechanism of the first embodiment.

FIG. 3 is a control flowchart of the steering assist control unit described in FIG.

FIG. 4 is a diagram showing a function map A of steering torque T and motor drive current A.

5 is a diagram showing a function map B of steering torque T and motor drive current A. FIG.

FIG. 6 is a diagram showing a function map C of steering torque T and motor drive current A.

FIG. 7 is a diagram showing a modified example of a function map of steering torque T and motor drive current A.

FIG. 8 is a block diagram showing a control circuit configuration of a steering assist mechanism of a second embodiment.

9 is a control flowchart of the steering assist control unit of the second embodiment described in FIG.

10 is a diagram showing a function map of a steering angle θ and a motor drive current A used in the control flow of FIG.

FIG. 11 is a steering torque T and a motor drive current A of this embodiment.
It is a figure which shows the function map of.

[Explanation of symbols]

 1 ... Front tire 2 ... Steering wheel 20 ... Steering assist mechanism 30 ... Electric motor 39 ... Vehicle speed sensor 40 ... Steering assist control unit

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area B62D 119: 00

Claims (3)

[Claims] 1. A steering assist device for a vehicle having steering assist means for assisting a steering operation by a driver, the steering condition detecting means detecting a steering condition of the driver, and the steering condition detecting means. Control means for controlling the steering assist force by the steering assist means based on the detection result by the steering assist means, and when the steering state is a predetermined value or more, the steering assist force is controlled by the steering assist means and A steering assist device for a vehicle, which controls a start timing of steering assist by an assisting device based on the steering state. 2. The steering assist device for a vehicle according to claim 1, wherein the steering state is a steering speed based on a steering torque generated by a steering operation. 3. The steering assist device for a vehicle according to claim 1, wherein the steering state is a steering speed based on a steering angle generated by a steering operation.