JPH11245836A - Steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve deflection restraint performance during application of turbulence and adequately set a steering feeling during a normal turning, by judging a steering condition of a driver, and by changing an auxiliary steering torque value and/or an auxiliary reaction torque value step-like or continuously over specific steps according to the judged steering condition. SOLUTION: A steering condition judging means 18 is connected with an auxiliary torque determining means 17a. This steering condition judging means 18, based on each signal output from a steering angular velocity sensor 11 and a torque sensor 12, estimates whether a driver holds or steers a wheel with retaining a steering wheel or with releasing it. The auxiliary torque determining means 17a changes a ratio of an auxiliary steering torque and an auxiliary reaction torque step-like or continuously over two steps according to the driver's steering condition so that the ratio is set high to improve deflection restraint performance during application of turbulence in the release condition, and is set to provide an adequate steering feeling in the normal condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering apparatus for a vehicle, and more particularly to a steering apparatus configured to perform appropriate steering assist during steering by an electric motor and to generate a steering torque for suppressing vehicle behavior when disturbance occurs. It is about.

[0002]

2. Description of the Related Art As a so-called power steering device for reducing a driver's steering force, for example, Japanese Patent Publication No. 50-33
A type as described in Japanese Patent No. 584 is known. This is configured to assist the steering force of the steering wheel with the output torque of the electric motor.In order to reduce the steering torque applied by the driver to the steering wheel, the vehicle speed and the like are determined from the detection result of the steering torque. Accordingly, an auxiliary steering torque (assist torque) for reducing the steering torque and a steering angular velocity for suppressing a steep rotation of the steering wheel, giving an appropriate sense of resistance to the driver and improving the convergence of the steering. , An auxiliary reaction torque (damping torque) as a reaction force component corresponding to the vehicle speed or the like is generated from the detection result.

[0003]

When the vehicle travels on a rutted road or irregular road surface, a moment may be generated around the king bin (disturbance input), but depending on the degree, the steering wheel may be removed.

In such an electric power steering apparatus as described above, when such a disturbance input occurs, a torque sensor detects the torque due to the steering wheel being picked up, and generates an assist torque to counter the disturbance. The generated steering angular velocity is detected, and a damping torque is generated in a direction to suppress the steering wheel being removed.

However, in the conventional electric power steering apparatus, since the assist torque and the damping torque are set only to make the steering feeling appropriate, the effect of preventing the steering wheel from being released when the hand is released is not sufficient. was there.

[0006] The effect of restraining the steering wheel from being taken can be enhanced by setting the assist torque and the damping torque as large as possible. However, if the assist torque is set too large, the steering torque during normal steering becomes lighter than necessary. In addition, if the damping torque is set too large, a strong viscous feeling is generated at the time of steering, and there is a problem that the steering feeling becomes unnatural in any case.

On the other hand, the steering feeling is important when the driver intends to steer actively, but its importance is low in a situation close to letting go. Conversely, the effect of suppressing the steering wheel is more important when the driver is close to letting go than when the driver is actively steering. This is due to the fact that the driver's corrective steering is delayed when the steering wheel is steered closer to the release.

The present invention has been devised in order to improve such disadvantages of the prior art. It is an object of the present invention to enhance the deflection suppressing performance during disturbance and appropriately improve the steering feeling during normal turning. It is an object of the present invention to provide a vehicle steering device that can be set.

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided a manual steering device for manually turning a steered wheel of a vehicle, and a method for detecting a steering torque applied to the manual steering device. Steering torque detecting means, a steering angular velocity detecting means for detecting a steering angular velocity, a vehicle speed detecting means, and an auxiliary steering torque based on the detected values of the vehicle speed detecting means and the steering torque detecting means. An auxiliary torque determining unit that determines an auxiliary reaction torque based on a detection value of the detection unit and the steering angular velocity detection unit, and determines an auxiliary torque value from the determined auxiliary steering torque value and the determined auxiliary reaction torque value; A vehicle steering device having an electric motor for applying an auxiliary torque based on the determined auxiliary torque value to the wheels, comprising: means for determining a steering state of a driver; And the auxiliary steering torque value and / or the auxiliary reaction force torque value according to the steering state of the driver 2
This is achieved by providing a vehicular steering system characterized by being changed stepwise or continuously more than stepwise.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of a vehicle steering system according to a first embodiment to which the present invention is applied. This device includes a pinion 4 connected to a steering shaft 2 integrally connected to a steering wheel 1 via a connection shaft 3 having a universal joint, and can reciprocate in the vehicle width direction by meshing with the pinion 4 and a tie rod 5. And a rack and pinion mechanism having a rack shaft 8 having both ends connected to knuckle arms of left and right front wheels 6 serving as steered wheels via the steering wheel. Further, in order to add an auxiliary torque, which is obtained by subtracting an auxiliary reaction torque from an auxiliary steering torque described later, to the manual steering force via the rack and pinion mechanism, the electric motor 9 constituting the electric power steering apparatus is mounted on a rack. It is arranged coaxially in the middle of the shaft 8.

In the vicinity of the pinion 4 of the rack and pinion mechanism, a steering angular velocity sensor 11 as a steering angular velocity detecting means for detecting the steering angular velocity from the rotation angle of the steering wheel 1 and a steering torque acting on the pinion 4 are provided. A torque sensor 12 is provided as a steering torque detecting means for detecting, and a vehicle speed sensor 13 is provided as a vehicle speed detecting means for outputting a signal corresponding to the traveling speed of the vehicle. It is connected to a steering control unit 17 for controlling the output of the electric motor 9 based on this.

As shown in FIG. 2, an auxiliary torque determining means 1 for calculating an auxiliary torque as an electric power steering device is provided in the steering control unit 17 described above.
7a is provided. The detection signals of the steering angular velocity sensor 11, the torque sensor 12, and the vehicle speed sensor 13 are input to the auxiliary torque determining means 17a, and the auxiliary steering torque (assist torque) for performing the normal assist control according to the respective detection signals. ) And the auxiliary reaction torque (damping torque). A steering state determination unit 18 for determining a driver's steering state is connected to the auxiliary torque determination unit 17a, and driving is performed by an algorithm described later based on each signal output from the steering angular velocity sensor 11 and the torque sensor 12. It is estimated (detected) whether the person is holding or steering the steering wheel while holding the steering wheel or almost in a released state.

In the steering control unit 17, a target current determining means 1 for setting a target current for the electric motor 9 in accordance with the auxiliary torque value output from the auxiliary torque determining means 17a.
7b, and an output current control means 17c for controlling a current flowing to the electric motor 9 in accordance with the target current. Then, the current control signal from the output current control means 17c is
The driving circuit 19 is input to a driving circuit 19 provided between the steering control unit 17 and the electric motor 9, and the driving circuit 19 drives the electric motor 9 by, for example, PWM control. The feedback control of the output current is performed between these steps.

In the assist torque determining means 17a in the steering control unit 17, the processing shown in the flowchart of FIG. 3 is repeatedly executed at a predetermined cycle. First, the signal output of each sensor is read (Step 1), the auxiliary steering torque value T1 and the auxiliary reaction torque value T2 are determined in Step 2 (Step 2), and the auxiliary reaction torque value T2 is calculated from the auxiliary steering torque value T1. Is subtracted (step 3) and output to the target current determining means 17b as an auxiliary torque value T (step 4).

This processing will be described in more detail with reference to FIGS. First, in step 1 above,
As shown in the flowchart of FIG. 4, the vehicle speed V (step 11), the steering angular velocity ω (step 12), the steering torque T
s (step 13) is read.

Next, in step 2, as shown in the flowchart of FIG. 5, first, in step 21, the steering torque Ts is used as an address, and two types of data set to different characteristics for each vehicle speed V are set. Table (Fig. 7
(A) and FIG. 7 (b)), the auxiliary steering torque values (assist torque values) T1 and T1 'are obtained. Here, FIG.
The coefficient of the data table of FIG. 7B is steeper than that of the data table of FIG. Therefore,
T1 'than when T1 is adopted as the auxiliary steering torque value
The auxiliary steering torque component with respect to the steering torque Ts is larger when is adopted.

Next, at step 22, the steering angle velocity ω is used as an address, and the auxiliary data is obtained from two types of data tables (FIGS. 7 (c) and 7 (d)) which are set to have different characteristics for each vehicle speed V. The force torque values (damping torque values) T2 and T2 'are determined. Here, the coefficient of the data table of FIG. 7D has a steeper slope than the data table of FIG. 7C. Accordingly, when T2 'is employed as the auxiliary reaction torque value, the auxiliary reaction torque component with respect to the steering angular velocity ω is larger when T2' is employed.

Next, the steering state of the driver is determined by the steering state determination means 18 (steps 23 and 24). Here, the steering state of the driver is detected based on the following equation. First, the equation of motion around the steering wheel is

[0020]

(Equation 1)

When the entire expression is integrated over time,

[0022]

(Equation 2)

By transforming this,

[0024]

(Equation 3)

Here, TS (kg · cm) is a torque sensor value, TH (kg · cm) is steering or steering torque, ω
(Deg · sec) is the steering angular velocity, and JH (kg · m) is the inertia of the steering wheel.

TH is obtained from the fact that the measured values of TS and ω are obtained. That is, if the calculation result on the left side of the equation (3) is 0, the driver has almost released the steering wheel, and if not 0, it is determined that the driver is holding or steering the steering wheel. I do.

Actually, the calculation of equation (3) is performed from time t = 0 to time t = X.

[0028]

(Equation 4)

Where ωX is the steering angular velocity at time X.

At this time, since the integration from the time t = 0 is affected by the offset, the first term of the equation (4) is divided into two at the time t = X−N.

[0031]

(Equation 5)

Then, the first term of the equation (5) is changed to time t = X
-N at the steering angular velocity ωX-N,

[0033]

(Equation 6)

Thus, from time t = X−N to time t
TH is obtained by performing integration up to X.

In step 24, it is determined whether or not the driver is holding or steering the steering wheel, or has almost released the steering wheel, based on whether TH obtained in step 23 is 0 or not. Then, when it is determined that the steering force is low (at the time of light steering) or not generated (at the time of releasing the hand), T1 'obtained at step 21 is adopted as the auxiliary steering torque value T1, and at step 22 Is used as the auxiliary reaction torque value T2, and used for the subsequent processing (step 25). If it is determined that the driver is performing steering or steering, T1 and T2 obtained in steps 21 and 22 are used as they are for subsequent processing (step 2).
6).

Then, an auxiliary torque value T is obtained by subtracting the auxiliary reaction torque value T2 from the auxiliary steering torque value T1 (step 27).

FIG. 6 is a control block diagram of the above step 2, and steps 21 to 27 correspond to the respective blocks in FIG.

The auxiliary torque value T thus determined
Is converted into a current value by the target current determining means 17b and supplied to the electric motor 9 to generate an auxiliary torque.

As shown in FIGS. 8 (a) and 8 (b), for example, when the vehicle 20 is traveling on a rutted road 21 having a V-shaped cross section, the braking force is applied when the wheels 6 are in contact with the slope 21a. When B acts, a moment I is generated around the kingpin axis O because the ground point P is displaced from the kingpin axis O. In particular, when the steering force is low or no steering force is generated, the steering wheel is taken as it is, but the steering angular velocity ω caused by the steering wheel is generated. The force torque value T2 is generated in a direction in which the steering angular velocity ω decreases, that is, so as to maintain the neutral position. At the same time, since the steering torque Ts is generated while the steering torque Ts is small due to the inertia and sliding resistance of each part, the auxiliary steering torque value T1 larger than usual is reduced so that the steering torque Ts is reduced, that is, the neutral position is maintained. Occurs. Thus, the electric motor 10 is driven in such a direction that the deflection of the vehicle 20 is prevented. Then, the driver notices the deflection of the vehicle and returns to the normal assist torque when the driver grips the steering wheel, so that the driver does not hinder the steering operation. In addition, the wheel 6 is the slope 21a.
It goes without saying that the same applies when a driving force is applied instead of the braking force when the vehicle is in contact with the ground.

In the above configuration, two types of data tables are used for obtaining the auxiliary steering torque value T1 and the auxiliary reaction torque value T2, but three or more types of tables are used.
The switching may be performed according to the degree of steering maintained by the driver.

FIG. 9 shows a modification of the above embodiment.
The same reference numerals are given to the same parts as in the above embodiment, and the detailed description thereof will be omitted. In this example,
In step 23 ′ corresponding to step 24 in FIG. 5, the degree y of the driver's steering or steering force is set to 0 (steering or steering).
In step 24 ', y.T1' + (1-y) .T1 is set to the auxiliary steering torque value T1, and y.T2 '+ (1-y) .T2 is set to the auxiliary steering torque. The force torque value T2 is used in the subsequent processing (steps 25 and 26 are deleted).

That is, if the degree of steering or steering is large, the auxiliary steering torque value T1 and the auxiliary reaction force torque value T2 are reduced, and the feeling of strangeness in steering at high speed or the like is reduced, and the degree of steering or steering is reduced. The auxiliary steering torque value T1 and the auxiliary reaction force torque value T2 are increased in accordance with the degree, so that the disturbance suppressing effect is enhanced. The corresponding portion is shown in FIG. 9 as steps 24 ′ and 25 ′ surrounded by a broken line. Other configurations, operations and effects are the same as those of the above embodiment.

In each of the above embodiments, the auxiliary steering torque value T1 and the auxiliary reaction force torque value T2 are changed stepwise or continuously in two or more steps according to the steering state of the driver by the steering state determination means. However, the assist steering torque value T1
Alternatively, only one of the auxiliary reaction torque value T2 and the auxiliary reaction torque value T2 may be changed.

For example, when only the auxiliary steering torque value T1 is changed in accordance with the driver's steering state by the steering state determination means, if the steering wheel is about to be pulled, the inertia of each part, the sliding resistance, etc. As a result, since the steering torque Ts is generated while being small, an auxiliary steering torque value T1 larger than usual is generated so that the steering torque Ts is reduced, that is, the neutral position is maintained. As a result, the electric motor 10 is driven in a direction that hinders the deflection of the vehicle 20. And the driver notices the deflection of the vehicle,
When the steering wheel is grasped, the normal auxiliary torque is restored.

When only the auxiliary reaction torque value T2 is changed in accordance with the driver's steering state by the steering state determination means, the steering angular velocity ω is generated when the steering wheel is about to be taken. , An auxiliary reaction force torque value T2 larger than usual is generated in a direction in which the steering angular velocity ω decreases, that is, so as to maintain the neutral position. As a result, the electric motor 10 is driven in a direction that hinders the deflection of the vehicle 20. And the driver notices the deflection of the vehicle,
When the steering wheel is grasped, the normal auxiliary torque is restored.

[0046]

As described above, according to the vehicle steering system of the present invention, in the release state or the lightly held state, the ratio of the auxiliary reaction torque based on the auxiliary steering torque and / or the steering angular velocity is increased so that the external force is not affected. By increasing the ratio of auxiliary steering torque and / or auxiliary reaction torque during normal driving, the ratio of auxiliary steering torque and / or auxiliary reaction torque is set so that an appropriate steering feeling can be obtained. Accordingly, it is possible to obtain the deflection suppressing performance at the time of disturbance and the appropriate steering feeling at the time of normal turning.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram schematically showing a vehicle steering system according to a first embodiment to which the present invention is applied.

FIG. 2 is a circuit block diagram of a control system of the steering device.

FIG. 3 is a flowchart showing a control process of the steering device.

FIG. 4 is a flowchart showing control processing of the steering device.

FIG. 5 is a flowchart showing control processing of the steering device.

FIG. 6 is a circuit block diagram of a control system of the steering device and a data table used for the control processing.

FIGS. 7A and 7B are enlarged views of a data table used for the control processing; FIG.

8A is a plan cross-sectional view schematically showing the movement of a wheel when a braking force is received during running on a rutted road, and FIG. 8B is a view taken along line bb of FIG. 8A.

FIG. 9 is a circuit block diagram of a control system of a vehicle steering system according to a second embodiment to which the present invention is applied.

[Explanation of symbols]

 Reference Signs List 1 steering wheel 2 steering shaft 3 connecting shaft 4 pinion 5 tie rod 6 front wheel 8 rack shaft 9 electric motor 11 steering angular velocity sensor 12 torque sensor 13 vehicle speed sensor 17 steering control unit 17a auxiliary torque determining means 17b target current determining means 17c output current controlling means 18 Steering state determination means 19 Drive circuit 20 Vehicle 21 Rutted road 21a Slope

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazushige Sumatama 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside Honda R & D Co., Ltd. (72) Hiroyuki Kawagoe 1-4-chuo Chuo, Wako-shi, Saitama No. 1 In Honda R & D Co., Ltd. (72) Inventor Tatsuya Nishikawa 1-4-1 Chuo, Wako-shi, Saitama Pref.

Claims (1)

[Claims] 1. A manual steering means for manually turning a steered wheel of a vehicle, a steering torque detecting means for detecting a steering torque applied to the manual steering means, and a steering for detecting a steering angular velocity. Angular speed detecting means, vehicle speed detecting means, and auxiliary steering torque are determined based on the detected values of the vehicle speed detecting means and the steering torque detecting means, and assisting is performed based on the detected values of the vehicle speed detecting means and the steering angular speed detecting means. An auxiliary torque determining means for determining a reaction torque, determining an auxiliary torque value from the determined auxiliary steering torque value and the determined auxiliary reaction torque value, and adding an auxiliary torque based on the determined auxiliary torque value to the steered wheels. And a means for determining a driver's steering state, wherein the auxiliary steering torque is determined according to the detected driver's steering state. And / or the auxiliary stepwise reaction force torque value in two or more stages or that have become so continuously changed, the vehicle steering apparatus according to claim.