JP2643685B2 - Rear wheel steering system for vehicles - 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 rear wheel steering system capable of controlling a rear wheel in the same phase as a front wheel.

[0002]

2. Description of the Related Art In recent years, a four-wheel steering device which steers not only front wheels but also rear wheels has been developed as a steering device for an automobile. There is a configuration in which a steering shaft as described above is provided, and the rear wheel is steered by driving the steering shaft in the axial direction by, for example, hydraulic pressure.

[0003] Such rear-wheel steering includes reverse-phase steering in which the front wheels are steered in the opposite direction and in-phase steering in which the front wheels are steered in the same direction. Generally, when the vehicle is running at a low speed, the reverse is performed so that the vehicle can make a small turn. In-phase steering is performed so that the vehicle can turn or change lanes without changing the running posture of the vehicle at medium to high speeds.

[0004] In particular, in general, the steering angle θr of the in-phase steering at the time of middle to high speed (hereinafter referred to as the steering angle) θr starts when the vehicle speed reaches a predetermined speed and starts the in-phase steering. After the start, the steering angle θr is increased with an increase in the vehicle speed, and the increase in the steering angle θr with respect to the increase in the vehicle speed is gradually reduced, so that the steering angle θr is set to be constant at a high speed region regardless of the increase in the vehicle speed. .

On the other hand, of course, since the rear wheel steering angle θr has to correspond to the front wheel steering angle, generally, the rear wheel steering angle to be proportional to the steering wheel angle theta _H corresponding to the front wheel steering angle theta
Set r.

Accordingly, for in-phase steering at middle and high speeds, for example, the in-phase coefficient K ₁ with respect to the vehicle speed is set as follows, and the value obtained by multiplying the in-phase coefficient K ₁ by the steering wheel angle θ _H (K ₁ × θ _H). ) Can be set as the rear wheel steering angle θr.

The in-phase coefficient K ₁ is 0 until the vehicle speed reaches a predetermined value, rises when the vehicle speed reaches a predetermined value, increases with the vehicle speed, and increases as the vehicle speed increases. Is set so that the steering angle θr is substantially constant in the high-speed range.

[0008]

The above-described steering control of the rear wheels is usually performed on the assumption that the vehicle speed is in a steady state.

That is, the steering angle of the rear wheels is set in accordance with the vehicle speed. For example, when the vehicle speed is low, the rear wheels are set in a reverse phase with a relatively large steering angle, and as the vehicle speed increases, the steering to the opposite phase is performed. The steering angle of the rear wheels is reduced to 0 in the middle speed range, and when the vehicle speed further increases, the steering angle is increased toward the same phase and the steering angle toward the same phase is increased as the vehicle speed increases. Things are going on.

However, at present, no consideration is given to a change in vehicle speed, that is, control according to the acceleration / deceleration state. Therefore, for example, a problem that the vehicle is over-steered when sudden braking is performed during turning is a problem. The in-phase control of the rear wheels corresponding to the vehicle speed cannot cope.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a vehicle rear wheel steering device capable of obtaining good and stable steering characteristics even during deceleration during turning of a vehicle. Aim.

[0012]

SUMMARY OF THE INVENTION Therefore, a vehicle rear wheel steering device according to the present invention is a vehicle rear wheel steering device capable of controlling a rear wheel of a vehicle in the same phase as a front wheel, and detects the deceleration of the vehicle. a deceleration detecting means for, Ru includes an in-phase steering angle setting means for setting a phase steering angle as detected deceleration above deceleration detecting means for phase controlling the rear wheel is greater than a predetermined value Along with the lateral acceleration of the vehicle
Output lateral acceleration detecting means, wherein the in- phase steering angle setting means detects the deceleration of the vehicle detected by the deceleration detecting means and the lateral deceleration of the vehicle detected by the lateral acceleration detecting means.
The present invention is characterized in that the in-phase steering angle can be set so that the in-phase steering angle of the rear wheel increases as the acceleration increases.

[0013]

[Action] In the vehicular electric rear wheel steering apparatus of the present invention, when the detected deceleration with the deceleration detecting means is greater than a predetermined value, phase steering angle setting means, which is detected by the deceleration detecting means the Detected by the vehicle deceleration and lateral acceleration detection means
The in- phase steering angle is set such that the in-phase steering angle of the rear wheels increases in accordance with the increase in the lateral acceleration of the vehicle, and the in- phase control of the rear wheels is performed according to the set in-phase steering angle. .

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram schematically showing the structure of a main part of a control means of a vehicle rear wheel steering apparatus according to an embodiment of the present invention; FIG. FIG. 3 is a block diagram schematically showing the overall configuration of the control means, and FIGS. 4 and 5 are diagrams showing the control characteristics thereof. FIG. 6 shows a specific example of the control amount.

First, the first embodiment will be described. In FIG. 2, reference numerals 1 and 2 denote front wheels, 3 and 4 denote rear wheels, and 5 denotes a steering handle (hereinafter referred to as a steering wheel). Front wheels 1, 2
A hydraulic cylinder 6 for power steering is provided in addition to a mechanical drive mechanism (not shown), such as a rack and pinion, on the tie rod for steering the front wheel, which is disposed so as to connect the tie rods. The hydraulic cylinder 6 is provided with a phase advance valve 13 that supplies and discharges hydraulic pressure according to the steering state of the handle 5. A rear wheel steering hydraulic cylinder 7 is attached to a rear wheel steering tie rod arranged so as to connect the rear wheels 3 and 4, and a rear wheel steering valve 8 is also provided on this hydraulic cylinder 7. Is provided.

The phase advance valve 13 and the rear wheel steering valve 8 are controlled by a controller 9 by a steering wheel angle θ _H , a vehicle speed V, a power steering pressure (power steering pressure), and a rear wheel steering angle (hereinafter the steering angle is referred to as a steering angle). Abbreviated) and L of the alternator
It is controlled based on terminal output and the like.

For this purpose, the controller 9 includes a steering wheel angle sensor 10, a vehicle speed sensor (vehicle speed detecting means) 11, a power steering pressure sensor 12, a rear wheel steering angle sensor 14, and an L terminal output of an alternator (not shown in FIG. 2). Is connected,
These pieces of detection information are input to the controller 9.

The general structure of the controller 9 for steering the front and rear wheels will be described. As shown in FIG. 3, each of the steering angle sensor 10, the vehicle speed sensor 11, and the L terminal output 15 of the alternator, which are input as digital signals, is provided. While the rear wheel steering mode is determined based on the information, the road surface roughness (based on the information from the power steering pressure sensor 12 and the information from the steering wheel angle sensor 10 and the vehicle speed sensor 11 input as an analog signal) is determined. The road surface μ) is estimated, and the determined rear wheel steering mode, the estimated value of the road surface μ, and the information from the steering wheel angle sensor 10, the vehicle speed sensor 11, and the rear wheel steering angle sensor 14 are used. The control amount is set for each control, and the control amount is converted from digital to analog and output to the front-wheel advance valve 13 and the rear-wheel steering valve 8. I have.

Rear wheel steering performed through the controller 9 includes reverse phase steering in which the front wheels are steered in the opposite direction and in-phase steering in which the front wheels are steered in the same direction. Steering is performed, and in-phase steering is performed so that the vehicle can turn or change lanes without deteriorating the running posture of the vehicle at medium to high speeds.

In addition, in this device, the rear wheel steering control corresponding to acceleration / deceleration is performed so that the rear wheel is steered in phase when the vehicle is decelerated during turning, and the rear wheel is steered in reverse phase when accelerated during the turning, in addition to the steering corresponding to the vehicle speed. Has become.

The rear wheel steering control corresponding to acceleration / deceleration is performed in addition to the vehicle speed corresponding steering control. That is,
A rear wheel steering angle corresponding to the vehicle speed is set, and a rear wheel steering angle corresponding to the acceleration / deceleration is set. The acceleration / deceleration rear wheel steering angle is set as an additional steering amount with respect to the vehicle speed corresponding rear wheel steering angle. The final rear wheel steering angle is determined by adding to the corresponding rear wheel steering angle, and the rear wheel steering is performed.

The portion around the controller 9 related to the acceleration / deceleration-compatible rear wheel steering is configured as shown in FIG.

That is, as shown in FIG. 1, the controller 9 estimates the road surface μ from the steering wheel angle sensor 10, the vehicle speed sensor 11, and the power steering pressure sensor 12 from each information of the steering wheel angle θ _H , the vehicle speed V, and the power steering pressure. Road surface μ estimating section 9A
And the lateral acceleration (hereinafter referred to as lateral G) generated in the vehicle from the information of the estimated road surface μ, the steering wheel angle θ _H , and the vehicle speed V.
G calculation unit (lateral acceleration detection means) 9B for calculating the acceleration and deceleration (that is, the longitudinal acceleration of the vehicle) V ′ (dV / dt) obtained by differentiating the information from the vehicle speed V. Calculation unit (deceleration detection means and acceleration detection means)
9E ', the in-phase steering angle θr of the rear wheel at the time of deceleration or the reverse-phase steering angle θr of the rear wheel at the time of acceleration based on the information from the acceleration / deceleration calculating unit 9E' and the information from the lateral G calculating unit 9B. An angle setting section (in-phase steering angle setting means and anti-phase steering angle setting means) 9J is provided.

The lateral G is calculated by the lateral G calculating section 9B at the time of steady turning, the lateral G: GY, the vehicle speed: V, and the steering wheel angle:
Since it is given as a function of θ _H and the road surface μ: μ, the lateral G is obtained from the function (1) or (1) ′ below. GY = V ² · θ _H / [{1+ (A / μ) V ² ｝ · L · ρ] (1) where A: stability factor L: wheel base ρ: steering gear ratio From this, GY = Θ _H / [(L · ρ / V ² ) + (AL · ρ / μ)] (1) ′ where −1 ≦ GY ≦ 1

The steering angle setting section 9J includes an acceleration / deceleration calculating section 9
The acceleration / deceleration V ′ calculated by E ′ and the above-described lateral G calculation unit 9
The in-phase steering angle θr of the rear wheels at the time of acceleration / deceleration is set from the lateral G calculated in B. Specifically, the steering angle setting unit 9J shows the steering angle setting unit 9J as shown in FIGS. Such a map is provided, and the in-phase steering angle θr of the rear wheels is set by the steering angle setting unit 9J based on any of these maps.

In the map of FIG. 4, (a) shows a case where the horizontal G is small, (b) shows a case where the horizontal G is medium, and (c) shows a case where the horizontal G is large. belongs to. As shown in the figure, in any region where the longitudinal acceleration (hereinafter, referred to as longitudinal G) is small, the steering corresponding to the acceleration / deceleration of the rear wheel is not performed, but when the longitudinal acceleration (hereinafter, longitudinal G) becomes larger than the set value. The steer characteristics are stabilized by controlling the rear wheels in phase during deceleration and controlling the rear wheels in reverse during acceleration.

In particular, when the lateral G is small, the boundary value before and after the start of acceleration / deceleration corresponding to acceleration of the rear wheel is large, and as the lateral G increases, the acceleration / deceleration corresponding steering is started. The boundary value between the front and rear G is small. Also,
When performing acceleration / deceleration-based steering of the rear wheels, the steering angle linearly increases with an increase in the front and rear G, but this increase rate (the slope of the characteristic line in the map) increases as the lateral G increases. Therefore it is getting bigger.

Therefore, the in-phase control of the rear wheels at the time of deceleration and the reverse phase control of the rear wheels at the time of acceleration are performed from the smaller front and rear G stages as the lateral G acting on the vehicle is large. Is larger, the in-phase control amount (in-phase steering angle) or the in-phase control amount (negative-phase steering angle) accompanying the increase of the front-back G
Is rapidly increasing.

The steering angle setting section 9J outputs a corresponding signal to the rear wheel steering valve 8 so that the in-phase steering angle or the reverse-phase steering angle set as described above is realized.

In order to ensure the running stability at middle and high speeds, the total steering angle (control amount) obtained by adding the above-described acceleration / deceleration-compatible rear wheel steering angle, vehicle speed-related steering angle, and the like is in-phase. To the opposite side (for example, 0.8
°) to limit the rear wheel steering angle for acceleration / deceleration, etc., and to decrease (turn back direction) of the time change (steering angular velocity) of the rear wheel steering angle for acceleration / deceleration. A certain limit (for example, 0.8 ° / sec each)
Is set to perform the degree of decrease clipping.

Since the rear wheel steering device for a vehicle according to one embodiment of the present invention is configured as described above, of the rear wheel steering performed through the controller 9, reverse control is performed when the vehicle is running at a low speed by controlling the vehicle speed. With the phase steering, the vehicle can make a small turn. At the time of middle and high speeds, the vehicle can turn or change lanes without disrupting the running posture of the vehicle by the same phase steering.

In addition, when the vehicle performs braking or acceleration when turning, the rear wheels are controlled in phase during deceleration and in reverse phase during acceleration according to the acceleration / deceleration.
Steering characteristics of the vehicle are stabilized.

That is, for example, when sudden braking is performed during a turn, if the front and rear G (in this case, deceleration) increases to some extent, the in-phase control of the rear wheels is performed. Is avoided by the in-phase steering of the rear wheels, and the steering characteristics of the vehicle can be stabilized within a certain range.

In particular, the larger the lateral G acting on the vehicle (ie, the smaller the turn or the higher the speed of the turn), the more the in-phase control of the rear wheels is performed from the smaller front and rear G stages. As the lateral G acting on the vehicle increases, the in-phase control amount (in-phase steering angle) increases sharply with the increase in the front-back G, so that when the lateral G increases during sudden braking during turning, the vehicle becomes over-steered. Can respond appropriately.

On the other hand, when the vehicle is suddenly accelerated during a turn or the like, the reverse phase control of the rear wheels is performed when the front-rear G (in this case, acceleration) becomes large to some extent. As a result, the steering characteristics of the vehicle can be stabilized within a certain range.

In this case as well, the larger the lateral G acting on the vehicle (ie, the smaller the turn or the higher the speed of the turn), the smaller the front and rear G stages in the in-phase control of the rear wheels. As the lateral G acting on the vehicle increases, the in-phase control amount (in-phase steering angle) increases rapidly as the longitudinal G increases. Appropriately respond to understeering of vehicles.

As described above, even if sudden braking or sudden acceleration is performed during turning, the rear wheels are controlled in phase or in opposite phases by an appropriate amount, and the steering characteristics of the vehicle are stabilized within a certain range. Because

Further, in the region where the front and rear G is small, the rear wheels are not steered in response to acceleration / deceleration, so that control is not performed unnecessarily during normal non-rapid deceleration or acceleration, and the stability of control is ensured. .

Here, an embodiment of the steering corresponding to the deceleration of the rear wheels will be described. As shown in FIG. 6, if the deceleration G occurs within a certain time as shown by the bending line a, the vehicle speed decreases during this time. The rear wheel steering angle corresponding to the vehicle speed decreases in response to the occurrence of a certain deceleration G as indicated by a bending line b shown by a chain line. On the other hand, the steering angle corresponding to the deceleration is added to the bending line b in correspondence with the bending line a, and greatly protrudes like a bending line c shown by a broken line.

However, the steering angle is limited to a certain limit by the upper limit clip, the decreasing speed of the steering angle is limited to a certain limit by the decreasing speed clip, and the steering angle corresponding to the deceleration is represented by a bending line shown by a solid line. As shown in FIG. 4D, since the vehicle speed changes without becoming excessive and gradual decrease, the control can be performed while stabilizing the behavior of the vehicle body and maintaining a good steering feeling.

Further, as shown in FIG. 4, the map relating to the setting of the in-phase steering angle θr performed by the steering angle setting section 9J includes a case where the lateral G is small, a case where the lateral G is medium and a case where the lateral G is large. Only three types are prepared, but this map is
To be more specific about the size of
It is also conceivable to prepare only two cases, a case where the horizontal G is small and a case where the horizontal G is large.

Further, the setting of the in-phase steering angle θr performed by the steering angle setting section 9J may be performed based on a map as shown in FIG. In other words, the boundary value before and after the start of the acceleration / deceleration steering of the rear wheel is constant regardless of the size of the lateral G. When the front and rear G becomes larger than the boundary value, the magnitude of the acceleration / deceleration corresponding steering angle of the rear wheel linearly increases with the increase of the front and rear G, but the rate of increase (the inclination of the characteristic line in the map) Is increased as the lateral G increases.

Even with such setting of the steering angle corresponding to acceleration / deceleration,
It is possible to cope to some extent with understeering of the vehicle that occurs as the lateral G increases during sudden acceleration during turning.

As described above, since the lateral G (lateral acceleration) is calculated from the lateral G, the vehicle speed, the steering wheel angle, and the road surface μ, the lateral G sensor becomes unnecessary, which is advantageous in terms of cost. May be provided, and the lateral G may be obtained directly from the lateral G sensor.

[0045]

As described above in detail, according to the vehicle rear wheel steering apparatus of the present invention, in the vehicle rear wheel steering apparatus capable of controlling the rear wheels of the vehicle in the same phase as the front wheels, the vehicle deceleration A deceleration detecting means for detecting the in-phase steering angle, and an in-phase steering angle setting means for setting an in-phase steering angle so as to control the in-phase control of the rear wheel when the deceleration detected by the deceleration detecting means is larger than a predetermined value. provided Rutotomoni, the lateral acceleration of the vehicle
A lateral acceleration detecting means for detecting the vehicle deceleration detected by the deceleration detecting means and the vehicle deceleration detected by the lateral acceleration detecting means.
The configuration is such that the in-phase steering angle of the rear wheel can be set so that the in-phase steering angle of the rear wheel increases with an increase in the lateral acceleration. Only the in-phase control of the rear wheels is performed, the steering characteristics of the vehicle are stabilized within a certain range, and a good steering feeling is maintained.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically illustrating a main configuration of a control unit of a vehicle rear wheel steering device as one embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a configuration of a vehicle rear wheel steering device as one embodiment of the present invention, corresponding to a state of the vehicle in a plan view.

FIG. 3 is a block diagram schematically showing an entire configuration of a control unit of the vehicle rear wheel steering device as one embodiment of the present invention.

FIG. 4 is a diagram showing control characteristics of a vehicle rear wheel steering device as one embodiment of the present invention.

FIG. 5 is a diagram showing a modified example of the control characteristics of the vehicle rear wheel steering device as one embodiment of the present invention.

FIG. 6 is a diagram showing a specific example of a control amount of the vehicle rear wheel steering device as one embodiment of the present invention.

[Explanation of symbols]

1, front wheel 3, 4 rear wheel 5 steering handle (handle) 6 hydraulic cylinder for power steering 7 hydraulic cylinder for rear wheel steering 8 valve for rear wheel steering 9 controller 9A road surface μ estimating section 9B lateral G calculating section (lateral) 9E 'acceleration / deceleration calculation unit (deceleration detection unit and acceleration detection unit) 9J steering angle setting unit (in-phase steering angle setting unit and antiphase steering angle setting unit) 10 steering wheel angle sensor 11 vehicle speed sensor (vehicle speed detection unit) ) 12 Power steering pressure sensor 13 Advance valve 14 Rear wheel steering angle sensor 15 Alternator L terminal output

Claims (1)

(57) [Claims] 1. A deceleration detecting means for detecting a deceleration of the vehicle, wherein the deceleration is detected by the deceleration detecting means. detect but Rutotomoni includes an in-phase steering angle setting means for setting a phase steering angle to phase controls the rear wheel is greater than a predetermined value, the lateral acceleration of the vehicle
Lateral acceleration detecting means, wherein the in- phase steering angle setting means detects the deceleration of the vehicle detected by the deceleration detecting means.
And the lateral acceleration of the vehicle detected by the lateral acceleration detecting means.
A rear wheel steering device for a vehicle, wherein the in-phase steering angle is set so that the in-phase steering angle of the rear wheel increases as the speed increases.