JPH05185943A - Rear-wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To provide a sufficient turning-round characteristic by providing a construction in which, at the time of rapid turn, an instantaneous antiphase steer angle is set with respect to a rear wheel, and causing this instantaneous antiphase steer angle when a lateral acceleration is high to be increased correspondingly. CONSTITUTION:A controller 9 is connected thereto with a handle angle sensor 10, a vehicle speed sensor 11, and a power steering pressure sensor 12. A road surface muis estimated in a road surface mu estimation section 9A on the basis of the information obtained from those sensors, and a lateral acceleration (lateral G) is calculated in a lateral G calculation section 9B on the basis of that mu value, the steering wheel angle QH determined by the power steer pressure sensor 12, and a vehicle speed V. The rear-wheel steering device further comprises an instantaneous antiphase steer angle setting means G for subjecting a rear wheel to an instantaneous antiphase control on the basis of the vehicle speed V at the time when the vehicle is rapidly turned, and a correction means 9F for increasing the instantaneous steer angle, for correction, when the lateral acceleration G is great. Accordingly, even when the vehicle turning- round characteristic using front wheels is lowered at the time of large lateral G, it is possible to enhance the turning-round characteristic through increase in the instantaneous antiphase steer angle.

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 rear wheels in phase with front wheels.

[0002]

2. Description of the Related Art In recent years, a four-wheel steering device for steering not only front wheels but also rear wheels has been developed as a steering device for automobiles. The rear wheel steering means in such a four-wheel steering device is a tie rod for the rear wheels. There is a configuration in which such a steering shaft is provided and the steering shaft is driven in the axial direction by, for example, hydraulic pressure to steer the rear wheels.

Further, such steering of the rear wheels includes reverse-phase steering that steers in the opposite direction to the front wheels and in-phase steering that steers in the same direction as the front wheels. Generally, the reverse steering is performed so that the vehicle can make a small turn when the vehicle speed is low. In-phase steering is performed so that at medium and high speeds, in-phase steering is performed so that the vehicle can turn or change lanes without losing the running posture of the vehicle. In particular, in general, the steering angle (hereinafter abbreviated as steering angle) θ _r of the in-phase steering at the middle and high speeds starts the in-phase steering when the vehicle speed reaches a predetermined speed, and after the in-phase steering starts. The steering angle θ _r is increased as the vehicle speed increases, and the increase in the steering angle θ _r with respect to the vehicle speed increase is gradually reduced so that the steering angle θ _r is set to be constant regardless of the vehicle speed increase in the high speed range. There is.

On the other hand, as a matter of course, since the rear wheel steering angle θ _r needs to correspond to the front wheel steering angle, generally, the rear wheel steering angle θ _r is proportional to the steering wheel angle θ _H corresponding to the front wheel steering angle. θ
Set _r . Therefore, for in-phase steering at medium and high speeds, for example, the in-phase coefficient K ₁ for the vehicle speed is set as follows, and the value (K ₁ × θ _H ) obtained by multiplying the in-phase coefficient K ₁ by the steering wheel angle θ _H is calculated. The wheel steering angle can be set as θ _r .

The in-phase coefficient K ₁ is 0 until the vehicle speed reaches a predetermined magnitude, rises from the point where the vehicle speed reaches a predetermined magnitude, and increases as the vehicle speed increases, and the vehicle speed increases as the vehicle speed increases. and gradually reducing the increase in the steering angle with respect to, in the high speed range is set to be substantially constant steering angle theta _r.

[0006]

By the way, as described above, it is usual to steer the rear wheels in the same phase at medium and high speeds. However, considering the turning ability of the vehicle (and eventually the steering transient response), the rear wheels are Reverse-phase steering is effective. However, this reverse-phase steering is for assisting the turning of the vehicle, and may be instantaneously performed at the start of turning. Therefore, a momentary anti-phase steering control is considered in which the rear wheels are instantaneously anti-phase steered at the start of turning of the vehicle.

Regarding this momentary reverse-phase steering, the in-phase control is not performed in the low speed range, and the required degree of turning is generally secured. However, in the middle and high speed ranges, the in-phase control is performed together with the sufficient turning ability. The reverse-phase steering becomes effective for a moment. However, in a certain high speed range, if priority is given to the stable behavior of the vehicle, it is better not to perform the reverse phase steering for a moment.

Therefore, it is conceivable to perform reverse phase steering for a moment in a speed range from a medium speed range to a high speed range with a control amount according to the speed. For example, traveling in which a lateral acceleration (lateral G) generated in a vehicle is high. When the steering wheel is steered during high-speed (high G traveling), the cornering force of the front wheels becomes saturated, and sufficient turning performance may not be obtained even when the steering wheel is momentarily out of phase.

The present invention was devised in view of the above-mentioned problems, and it is possible to realize a momentary reverse-phase steering so that a sufficient turning performance can be obtained even when the steering wheel is turned during high lateral acceleration. An object is to provide a rear wheel steering device for a vehicle.

[0010]

Therefore, a vehicle rear wheel steering system according to the present invention is a vehicle rear wheel steering system capable of controlling the rear wheels of a vehicle in phase with the front wheels. Lateral acceleration detection means for detecting the vehicle speed, vehicle speed detection means for detecting the vehicle speed of the vehicle, instantaneously the rear wheel based on the vehicle speed information detected by the vehicle speed detection means when the vehicle is about to make a sharp turn. And a momentary anti-phase steering angle setting means for setting a momentary anti-phase steering angle for reverse-phase control, wherein the momentary anti-phase steering angle setting means is based on the lateral acceleration information detected by the lateral acceleration detecting means. It is characterized in that correction means is provided for increasing and correcting the reverse phase steering angle for a moment when the lateral acceleration is large.

[0011]

In the above-described vehicle rear wheel steering system according to the present invention, the momentary reverse-phase steering angle setting means instantaneously changes the rear wheels based on the vehicle speed information detected by the vehicle speed detecting means when the vehicle is about to make a sharp turn. A momentary reverse-phase steering angle is set for reverse-phase control, and the momentary reverse-phase steering angle is large in lateral acceleration of the vehicle based on the lateral acceleration information detected by the lateral acceleration detecting means by the correcting means. Sometimes, it is corrected so as to momentarily increase the anti-phase steering angle. Therefore, when the lateral acceleration of the vehicle is large, even if the turning ability of the vehicle due to the front wheels is reduced, the turning ability is enhanced through the rear wheels due to the momentary increase in the antiphase steering angle.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 5 show a vehicle rear wheel steering system as a first embodiment of the present invention, and FIG. FIG. 2 is a block diagram schematically showing the configuration of the main part of FIG. 2, FIG. 2 is a schematic configuration diagram showing the configuration corresponding to the plan view state of the vehicle,
FIG. 3 is a block diagram schematically showing the overall configuration of the control means, FIG. 4 is a characteristic diagram illustrating a phenomenon required for the control, FIG. 5 is a diagram showing the control characteristic, and FIG. FIG. 7 is a block diagram schematically showing a main part configuration of a control means of a vehicle rear wheel steering system as a second embodiment of the present invention, and FIG. 7 is a control of a vehicle rear wheel steering system as a third embodiment of the present invention. FIG. 9 is a block diagram schematically showing a main part configuration of means, FIG. 8 is a block diagram schematically showing a main part configuration of a modification of the first embodiment, and FIG. 9 is a modification of the second embodiment. It is a block diagram which shows the principal part structure typically.

First, the first embodiment will be described. In FIG. 2, 1 and 2 are front wheels, 3 and 4 are rear wheels, and 5 is a steering wheel (hereinafter referred to as a steering wheel). Front wheels 1,2
In addition to a mechanical drive mechanism (not shown) such as a rack and pinion, a hydraulic cylinder 6 for power steering is attached to the front wheel steering tie rod arranged so as to be connected to each other. The hydraulic cylinder 6 is provided with a phase advancing valve 13 that supplies and discharges hydraulic pressure according to the steering state of the handle 5. Further, a hydraulic cylinder 7 for steering the rear wheels is attached to the tie rod for steering the rear wheels arranged so as to connect the rear wheels 3 and 4, and a valve 8 for steering the rear wheels is also attached to the hydraulic cylinder 7. It is provided.

The phase advancing valve 13 and the rear wheel steering valve 8 are controlled by the controller 9 by the steering wheel angle θ _H , the vehicle speed V, the power steering pressure (power steering pressure), the rear wheel steering angle (hereinafter, steering angle is referred to as steering angle). (Abbreviated) and L of alternator
It is controlled based on the terminal output and the like. Therefore, the controller 9 has a steering wheel angle sensor 10,
Vehicle speed sensor (vehicle speed detecting means) 11, power steering pressure sensor 1
2, the rear wheel steering angle sensor 14 and the L terminal output (not shown in FIG. 2) of the alternator, etc. are connected, and respective detection information of these is input to the controller 9.

A schematic configuration of steering of the front and rear wheels of the controller 9 will be described. As shown in FIG. 3, the steering wheel angle sensor 10, the vehicle speed sensor 11, and the L terminal output 15 of the alternator are inputted as digital signals. 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 analog signals ( Road surface μ) is estimated, and based on the determined rear wheel steering mode, the estimated road surface μ value, and each information from the steering wheel angle sensor 10, the vehicle speed sensor 11, and the rear wheel steering angle sensor 14 described above. Then, the control amount of each control is set, and this is digital-to-analog converted, and output to the front-phase advancing valve 13 and the rear-wheel steering valve 8. There is.

The rear-wheel steering performed through the controller 9 includes a reverse-phase steering for steering in the opposite direction to the front wheels and an in-phase steering for steering in the same direction as the front wheels. The reverse-phase steering allows the vehicle to make a small turn when the vehicle is low speed. Steering is performed, and in-phase steering is performed so that the vehicle can turn or change lanes without disturbing the running posture of the vehicle at medium and high speeds. In addition, in this device, when the vehicle starts to turn at medium and high speeds, momentary reverse-phase steering control for instantaneously performing reverse-phase steering of the rear wheels is performed. Therefore, the components of the controller 9 for the in-phase steering and the reverse-phase steering of the rear wheels for a moment will be described.

As shown in FIG. 1, the controller 9 includes
A road surface μ estimation unit 9A that estimates the road surface μ from the steering wheel angle sensor 10, the vehicle speed sensor 11, the steering wheel angle θ _H from the power steering pressure sensor 12, the vehicle speed V, and the power steering pressure information, and the estimated road surface μ and the steering wheel angle. A lateral G calculating section (lateral acceleration detecting means) 9B for calculating a lateral acceleration (hereinafter referred to as lateral G) generated in the vehicle from each information of θ _H and vehicle speed V, and an in-phase coefficient K _{1 for} the value of the pseudo steering wheel angle θ _TH. And rear wheel steering angle θ _r
(= K ₁ × θ _TH ) and the in-phase steering angle setting unit (rear wheel steering angle setting means) 9D that outputs a control signal corresponding to the rear wheel steering angle θ _r to the rear wheel steering valve 8; A steering wheel angular velocity calculation unit (differential unit) 9E that calculates the steering wheel angular velocity θ _H ′ (dθ _H / dt) from the steering wheel angle information, and a coefficient that corrects the momentary anti-phase coefficient (a momentary anti-phase coefficient correction coefficient) α are set. A correction coefficient setting section (correction means) 9F, a momentary anti-phase steering angle setting section (momentary anti-phase steering angle setting means) 9G that sets the momentary anti-phase steering angle θ _r of the rear wheels from the momentary anti-phase coefficient, and an in-phase steering. Corner setting section 9
A rear wheel steering angle determination unit 9H that adds the rear wheel steering angle determined by D and the rear wheel steering angle determined by the momentary antiphase steering angle setting unit 9G is provided.

The lateral G calculation unit 9B calculates the lateral G at the time of steady turn, lateral G: GY, vehicle speed: V, and 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 following equation (1) or (1) ′ which is this function. 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) + (a · L · ρ / μ)] ··· (1) ' However, in the -1 ≦ GY ≦ 1-phase steering angle setting section 9D, as described above The detected steering wheel angle θ _H is multiplied by the in-phase coefficient K ₁ to determine the rear wheel steering angle θ _r . The in-phase coefficient K ₁ is the in-phase steering angle setting unit 9D in FIG.
As shown in the block of, the vehicle speed rises from reaching the predetermined speed and increases as the vehicle speed increases, but the increase amount with respect to the vehicle speed gradually decreases,
At high speed, it is almost constant.

The control of the reverse phase steering for a moment will be described.
This momentary out-of-phase steering is a control for promptly turning the vehicle by steering the rear wheels momentarily out of phase with the front wheels when the driver desires a sharp turn, such as when the steering wheel is suddenly operated. is there. Whether the driver wants a sharp turn,
The steering wheel angular velocity θ _H ′ calculated by the steering wheel angular velocity calculation unit 16E can be used for the determination, and the opposite-phase steering is performed momentarily according to the steering wheel angular velocity θ _H ′.

The momentary reverse phase steering angle at this time is set according to the vehicle speed V in addition to the steering wheel angular velocity θ _H ′, but is corrected according to the state of the lateral G occurring in the vehicle.
That is, in the correction coefficient setting unit 9F, as shown in the map of FIG. 4, in a region where the lateral G is small (for example, lateral G <0.2),
When the correction coefficient for the momentary anti-phase coefficient (hereinafter referred to as the momentary anti-phase correction coefficient) α is set to a constant value (α = 1) and the lateral G becomes larger than this (for example, 0.2 <horizontal G <0.6). , The anti-phase correction coefficient α is momentarily increased (here, linearly), and when the lateral G reaches a predetermined value (for example, lateral G = 0.6), the anti-phase correction coefficient α is momentarily reversed again (for example, a constant value). α = 2.5)
And As a result, the lateral G is increased to some extent (0.
When the cornering force of the front wheels approaches the saturation state (2 <horizontal G), the correction coefficient α is increased so that the amount of reverse phase is momentarily increased according to the lateral G. However, there is a limit to the increase of the correction coefficient α.

On the other hand, in the momentary reverse-phase steering angle setting section 9G, as shown in the map of FIG. 5, the reverse-phase control is performed momentarily around the medium speed range of the vehicle speed, and the momentary reverse-phase amount is set. The momentary anti-phase coefficient K ₃ rises from 0 when it enters the middle speed range and increases to become a constant value in the middle speed range, and then it decreases to 0 at an appropriate speed when going from the middle speed range to the high speed range. Is set.

Thus, the reason why the reverse phase control is not executed for a moment in the low speed range is that it is possible to obtain a sufficient turning ability only by the cornering force of the front wheels without performing the in-phase control in the low speed range. The reason why the reverse phase control is not performed for a moment in the high speed range is that the stable behavior of the vehicle is prioritized in the high speed range. Instantaneous reverse phase steering angle setting unit 9G
So for such a moment opposite phase coefficient K _3, the correction coefficient momentarily reversed phase coefficients already corrected obtained by multiplying the alpha K ₃ above '(=
α × K ₃ ) is multiplied by the steering wheel angular velocity θ _H ′ from the steering wheel angular velocity calculation unit (differential unit) 9E, and a momentary reverse phase amount (rear wheel steering angle) (= K ₃ ′ × θ _H ′) is output. ..

In the rear wheel steering angle determining section 9H, the in-phase steering angle from the in-phase steering angle setting section 9D and the instantaneous anti-phase steering angle from the momentary anti-phase steering angle setting section 9G are added to obtain a final rear wheel steering angle. θ _r is determined. In this case, the steering angle velocity θ _H ′
Therefore, it occurs before the in-phase steering angle corresponding to the steering wheel angle θ _H. That is, when steering is performed from the straight running state, the steering angle θ _H increases and the in-phase steering amount increases after the rear wheels are steered to the in-phase steering at the initial stage of steering, and the rear wheels shift to the in-phase steering. It will be.

The rear wheel steering system for a vehicle as the first embodiment of the present invention is constructed as described above, and therefore, at the middle and high speeds, the in-phase control of the rear wheels allows the vehicle to turn or turn without disturbing the running posture of the vehicle. You will be able to change lanes. Further, at the beginning of steering in the medium speed range, momentary reverse-phase control is performed to steer the wheels in opposite phase to the front wheels, so that the vehicle can be swiftly turned and a sharp turn can be made. When the lateral G becomes high to some extent and the cornering force of the front wheels approaches saturation, the amount of reverse phase is momentarily increased and corrected, so that the cornering forces of the rear wheels can be properly taken out. The above-described improvement in the turning ability of the vehicle can be realized in a wider range.

Next, the second embodiment will be described. In the device of this embodiment, the portion related to the rear wheel in-phase steering of the controller is constructed as shown in FIG. As shown in FIG. 6, the controller 9 has a steering wheel angle θ from a steering wheel angle sensor 10, a vehicle speed sensor 11, and a power steering pressure sensor 12.
_H, the vehicle speed V, and the road surface μ estimation part 9A which road μ is estimated from the information of the power steering pressure, the estimated road surface μ and the steering wheel angle theta _H, lateral acceleration generated from the information of the vehicle speed V of the vehicle (hereinafter, horizontal G), and a pseudo steering wheel angle that sets a steering wheel angle (pseudo steering wheel angle) θ _TH corresponding to the value of the cornering force from each of the calculated lateral G and steering wheel angle θ _H information. The setting unit 9C and the value of the pseudo steering wheel angle θ _TH are multiplied by the in-phase coefficient K ₁ to determine the rear wheel steering angle θ _r (= K ₁ × θ _TH ). In addition to the in-phase steering angle setting unit 9D that outputs a control signal according to the angle θ _r , a steering wheel angular velocity calculation unit (differential unit) that calculates the steering wheel angular velocity θ _H ′ (dθ _H / dt) from the steering wheel angle information. 9E and a coefficient for correcting the instantaneous anti-phase coefficient (for the instantaneous anti-phase coefficient supplement A correction coefficient setting unit 9F for setting a coefficient) alpha, and anti-phase steering angle setting unit 9G momentarily to set the anti-phase steering angle theta _r a moment of the rear wheels from the reverse phase coefficients moment, is determined in phase steering angle setting section 9D Further, a rear wheel steering angle determination unit 9H that selects either the rear wheel steering angle or the rear wheel steering angle determined by the reverse phase steering angle setting unit 9G is provided.

The road surface μ estimating section 9A and the lateral G calculating section 9 described above.
B, the in-phase steering angle setting unit 9D, the steering wheel angular velocity calculation unit (differential unit) 9E, the correction coefficient setting unit 9F, the momentary antiphase steering angle setting unit 9G, and the rear wheel steering angle determination unit 9H are the same as those in the first embodiment. The description is omitted. Explaining the pseudo steering wheel angle setting unit 9C, the pseudo steering wheel angle θ _TH set by the pseudo steering wheel angle setting unit 9C is a steering wheel angle corresponding to the value of the cornering force. The non-linear behavior has begun to occur,
An increase in the cornering force generated in the front wheel is smaller than the increase of the steering wheel angle theta _H, such that the actual steering wheel angle theta _H corresponding to cornering force of the front wheels is obtained, the steering wheel angle theta _H detected here Correcting.

That is, the larger the lateral G, the steering wheel angle θ _H
Is larger than that corresponding to the cornering force, and is set corresponding to the steering wheel angle θ _H.
As shown in FIG. 4, _r should be increased so as to be almost proportional to the lateral G generated on the vehicle body by the cornering force generated by the steering of the front wheels. When the size is increased to some extent (for example, larger than 0.5 G), the lateral acceleration gradually increases with an increase in the front wheel steering angle.

Therefore, with respect to the vehicle lateral G (virtual lateral G) that can be calculated as linearly corresponding to the steering wheel angle θ _H , this virtual lateral G has a certain height (for example, 0.5 G).
Until the steering wheel angle θ _H is reached, the steering wheel angle θ _H is linearly increased with the virtual lateral G, and the virtual lateral G is at a certain height (for example, 0.5 G)
Then, the steering wheel angle θ _H is gradually corrected to be smaller than the linear relationship with the virtual lateral G. The steering wheel angle θ _{H in} this case becomes the pseudo steering wheel angle θ _TH , and the in-phase steering angle setting unit 9D determines the in-phase steering angle of the rear wheels based on this pseudo steering wheel angle θ _TH .

Such virtual lateral G and pseudo handle angle θ _TH
In order to set the relationship with the horizontal direction G in this embodiment, as shown in the block of the pseudo steering wheel angle setting unit 9C in FIG.
1 until it reaches a certain height (eg 0.5G)
Then, when the lateral G reaches a certain height (for example, 0.5 G), the coefficient K '(output / input) becomes gradually smaller than 1.
Is multiplied by the detected value of the steering wheel angle θ _H to obtain K ′ × θ
_The pseudo steering wheel angle θ _TH is _calculated as _H.

Since the vehicle rear wheel steering system according to the second embodiment of the present invention is constructed as described above, the lateral G is increased to some extent and the cornering force of the front wheels is increased as in the first embodiment. When the saturation state is approached, the amount of reverse phase is momentarily increased and corrected, so that the cornering force of the rear wheels can be properly taken out, and the above-mentioned improvement of the turning ability of the vehicle can be realized in a wider range. The following actions and effects can be obtained.

That is, the steering wheel angle θ _H increases as the lateral G increases.
Is larger than the cornering force of the front wheels, the steering wheel angle θ _H that determines the in-phase steering angle corresponds to the cornering force of the front wheels in consideration of the lateral G of the vehicle. Since the pseudo steering wheel angle θ _TH is used, the rear wheels can be properly steered.

That is, in the region where the lateral G of the vehicle is large,
The non-linear behavior of the tire increases the steering wheel angle θ _H relative to the cornering force of the front wheels, while the rear wheels have a smaller steering angle than the front wheels, which affects the nonlinear characteristics of the tire. The rear-wheel steering angle corresponds to the cornering force of the rear wheels without being received, and even in such an area, if the in-phase steering angle of the rear wheels is set simply in proportion to the steering wheel angle θ _H , the understeer tendency is promoted. Will be done.

On the other hand, in consideration of this, the above-mentioned pseudo steering wheel angle θ _TH applied in this embodiment is corrected so as to cancel out the influence of the behavior on the non-linearity of this tire. The wheel steering angle θ _r is set to correspond to the actual steering angle (front wheel steering angle). As a result, it is possible to prevent the understeer characteristic of the vehicle from increasing due to excessive in-phase steering of the rear wheels in a region where the lateral G of the vehicle is large, and to secure a stable steer characteristic. As the information of the steering wheel angle θ _H that determines the in-phase steering angle θ _r of the rear wheels, the pseudo steering wheel angle θ _TH in consideration of the influence of the lateral G of the vehicle is used, and the steering of the rear wheels is properly performed. In the region where the lateral G of the vehicle is large, an increase in the understeer characteristic of the vehicle, which is likely to occur due to excessive in-phase steering of the rear wheels, is prevented, and stable steering characteristics can be secured.

Next, the third embodiment will be described.
In this embodiment, in the device of this embodiment, a portion of the controller involved in rear wheel in-phase steering is configured as shown in FIG. That is, in the third embodiment, the momentary reverse-phase steering angle setting unit 9G sets the momentary reverse-phase steering amount based on the vehicle speed V and the pseudo steering wheel angular velocity θ _TH ′.

The pseudo steering wheel angular velocity θ _TH ′ is set by the pseudo steering wheel angular velocity setting unit 9J in consideration of the steering wheel angular velocity θ _TH ′ and the lateral G generated in the vehicle. That is, as in the map in the block showing the pseudo steering wheel angular velocity setting unit 9J in FIG. 7, the lateral G is 1 until the lateral G reaches a certain height (for example, 0.5 G), and the lateral G is a certain height (for example, 0.5 G). 0.
Coefficient K ″ that gradually becomes larger than 1 when reaching 5G)
By multiplying (output / input) by the steering wheel angular velocity θ _H ′ calculated by the steering wheel angular velocity calculation unit 9E, K ″ ×
The pseudo handle angular velocity θ _TH ′ is obtained as θ _H ′.

Then, in the momentary reverse-phase steering angle setting section 9G,
The pseudo steering wheel angular velocity θ _TH ′ is momentarily multiplied by the antiphase coefficient K ₃ to obtain the antiphase steering angle for a moment. In addition,
The momentary anti-phase coefficient K ₃ is adapted to perform momentary anti-phase control centering around the medium speed range of the vehicle speed as in the map in the block showing the momentary anti-phase steering angle setting unit 9G, but the pseudo steering wheel angular velocity Since the lateral G is added to θ _TH ′, this map is constant regardless of the lateral G.

Since the vehicle rear wheel steering system according to the third embodiment of the present invention is constructed as described above, substantially the same actions and effects as those of the first and second embodiments can be obtained. The setting of the momentary antiphase steering angle using the pseudo steering wheel angular velocity θ _TH ′ of the third embodiment can also be applied to the first embodiment.
Further, as shown in FIGS. 8 and 9, the rear wheel steering angle determination unit 9H in the above-described first and second embodiments is momentarily changed to the rear wheel steering angle determined by the rear wheel steering angle determination unit 9D. A configuration in which one of the rear wheel steering angles determined by the reverse phase steering angle setting unit 9G is set to be selected is also conceivable. Further, a configuration may be considered in which the rear wheel steering angle determination unit 9H in the third embodiment is set so as to select either one of the rear wheel steering angle.

Further, since the lateral G (lateral acceleration) is calculated from the lateral G, the vehicle speed, the steering wheel angle, and the road surface μ as described above, the lateral G sensor is not necessary, which is advantageous in terms of cost. It is also possible to provide a lateral G sensor in and to obtain the lateral G directly from the lateral G sensor.

[0039]

As described in detail above, according to the vehicle rear wheel steering system of the present invention, in the vehicle rear wheel steering system capable of controlling the rear wheels of the vehicle in the same phase as the front wheels, the lateral wheels generated in the vehicle are Lateral acceleration detecting means for detecting acceleration, vehicle speed detecting means for detecting the vehicle speed of the vehicle, and instantaneously moving the rear wheel based on the vehicle speed information detected by the vehicle speed detecting means when the vehicle is about to make a sharp turn. The momentary anti-phase steering angle setting means for setting the momentary anti-phase steering angle for reverse phase control, and the momentary anti-phase steering angle setting means provides the lateral acceleration information detected by the lateral acceleration detection means. When the lateral acceleration is large, the correction means for correcting the reverse-phase steering angle for a moment is provided so that the lateral-acceleration becomes high to some extent and the cornering force of the front wheels becomes saturated. Since the large-corrected, will be able to do to retrieve cornering force of the rear wheels properly, it can be realized to improve the turning performance of the vehicle in a wider range.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing a main configuration of a control means of a vehicle rear wheel steering system as a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a configuration of a vehicle rear wheel steering system as a first embodiment of the present invention in correspondence with a state of the vehicle in a plan view.

FIG. 3 is a block diagram schematically showing the overall configuration of the control means of the vehicle rear wheel steering system as the first embodiment of the present invention.

FIG. 4 is a diagram showing the control characteristics of the vehicle rear wheel steering system according to the first embodiment of the present invention.

FIG. 5 is a diagram showing the control characteristics of the vehicle rear wheel steering system according to the first embodiment of the present invention.

FIG. 6 is a block diagram schematically showing a main part configuration of a control means of a vehicle rear wheel steering system as a second embodiment of the present invention.

FIG. 7 is a block diagram schematically showing a main configuration of a control means of a vehicle rear wheel steering system as a third embodiment of the present invention.

FIG. 8 is a block diagram schematically showing a main part configuration of a modified example of the control means of the vehicle rear wheel steering system according to the first embodiment of the present invention.

FIG. 9 is a block diagram schematically showing a main part configuration of a modified example of the control means of the vehicle rear wheel steering system as the second embodiment of the present invention.

[Explanation of symbols]

1, 2 front wheels 3, 4 rear wheels 5 steering handle (handle) 6 hydraulic cylinder for power steering 7 hydraulic cylinder for steering rear wheels 8 rear wheel steering valve 9 controller 9A road surface μ estimation unit 9B lateral G calculation unit (horizontal) Acceleration detection means) 9C Pseudo steering wheel angle setting section 9D In-phase steering angle setting section (rear wheel steering angle setting means) 9E Steering wheel angular velocity calculation section (differential section) 9F Correction coefficient setting section (correction means) 9G Instantaneous reverse phase steering angle setting section (Instantaneous anti-phase steering angle setting means) 9H Rear wheel steering angle determination section 9J Pseudo steering wheel angular velocity setting section 10 Steering wheel angle sensor 11 Vehicle speed sensor (vehicle speed detecting means) 12 Power steering pressure sensor 13 Phase advancing valve 14 Rear wheel steering angle sensor 15 Alternator L terminal output

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Claims (1)

[Claims] 1. A vehicle rear wheel steering system capable of controlling the rear wheels of a vehicle in phase with the front wheels, lateral acceleration detecting means for detecting lateral acceleration occurring in the vehicle, and vehicle speed detecting means for detecting the vehicle speed of the vehicle. And a momentary anti-phase steering for setting a momentary anti-phase steering angle for momentarily anti-phase controlling the rear wheels based on the vehicle speed information detected by the vehicle speed detecting means when the vehicle is about to make a sharp turn. With corner setting means,
The momentary reverse-phase steering angle setting means is provided with correction means for increasing and correcting the momentary reverse-phase steering angle when the lateral acceleration is large based on the lateral acceleration information detected by the lateral acceleration detection means. A rear wheel steering device for a vehicle.