JP3031772B2 - Vehicle rear wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering apparatus for steering a rear wheel in accordance with steering of a front wheel (steering of a steering wheel).

[0002]

2. Description of the Related Art Generally, a rear wheel steering device for a vehicle includes a steering mechanism for steering a rear wheel, a vehicle speed sensor for detecting a vehicle speed, and a front wheel, as disclosed in Japanese Patent Application Laid-Open No. 2-27463. And a control unit that receives the detection signals from the two sensors and controls the operation of the rear wheel steering mechanism. There are various modes of rear wheel steering control.For example, at low vehicle speeds, the rear wheels are steered in the opposite phase to the steering direction of the front wheels, and at high vehicle speeds, the rear wheels are steered by the front wheels. It is generally well known that steering is performed in the same direction in the same direction as the direction to ensure both turning performance at a low vehicle speed and steering stability at a high vehicle speed.

[0003]

In the conventional rear wheel steering apparatus, when the rear wheels are steered in the opposite phase to the front wheels, the turning center point of the vehicle approaches the side of the vehicle, but the rear seat of the vehicle does not move. For the occupant who sits on the vehicle, the turning center point is closer to the front side, so that when the rear wheels are largely steered in the opposite phase, there is a problem that the driver feels discomfort and feels bad.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve steering comfort by restricting steering of the rear wheels to the opposite phase when an occupant is seated on the rear seat. It is intended to provide a rear wheel steering device for a vehicle that can achieve the following.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, an invention according to a first aspect of the present invention is directed to a vehicle for rearwardly steering a rear wheel at least in an opposite phase to a direction opposite to a steering direction of a front wheel in response to steering of a front wheel. In the wheel steering device, seating state detecting means for detecting a state in which the occupant is seated on the rear seat, and a signal from the detecting means, and when the occupant is seated on the rear seat, the rear wheels are in opposite phases. And a correcting means for correcting so as to reduce the steering amount.

The second and third aspects of the present invention are all dependent on the first aspect of the invention, and particularly when the rear wheels are largely steered in the opposite phase, this is suppressed. Things. That is, the invention described in claim 2 is
The correction means is configured to perform correction to reduce the amount of steering of the rear wheels to the opposite phase only at an extremely low vehicle speed. Further, the invention according to claim 3 is configured such that the correction means performs correction for reducing the amount of steering of the rear wheels to the opposite phase only when the steering angle of the front wheels is large.

According to a fourth aspect of the present invention, in order to enhance the ease of use by the driver, in addition to the constituent elements of the first aspect of the invention, a cancel switch for regulating the correction by the correction means is provided.

[0008]

According to the above-mentioned structure, according to the first aspect of the present invention,
When the occupant is seated in the rear seat, this is detected by the seating state detection means, and the correction means receiving a signal from the detection means corrects the rear wheel to reduce the steering amount to the opposite phase. Is performed. Thus, the rear wheels are not largely steered in the opposite phase to the front wheels, and it is possible to prevent the occupant on the rear seat from feeling uncomfortable.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic structure of a drive system and a steering system of a vehicle provided with a rear wheel steering device according to an embodiment of the present invention, wherein 1L and 1R denote left and right front wheels, 2L and 2R denote left and right rear wheels, 3 is an engine mounted horizontally on the front of the car body, 4
Is a transmission disposed on the left side of the engine 3. The output of the engine 3 is changed by the transmission 4
The left and right front wheels 1L, via the differential device 5 and the drive shafts 6, 6
1R to drive the front wheels 1L and 1R. Therefore, this vehicle is an FF (front engine / front drive) type vehicle, in which front wheels 1L and 1R are driving wheels, and rear wheels 2L and 2R are driven wheels.

Reference numeral 11 denotes a steering device for steering the left and right front wheels 1L, 1R.
1 is a steering shaft 13 having one end connected to the steering handle 12, a rod 14 extending in the vehicle width direction, and moving in the axial direction (that is, the vehicle width direction) by rotation of the steering shaft 13, and one end. Are connected to the rod 14, and a pair of left and right tie rods 15, 15 are connected to the front wheels 1L, 1R at the other end.

Reference numeral 21 denotes a rear wheel steering device that steers the left and right rear wheels 2L and 2R when the steering device 11 steers the front wheels 1L and 1R. The rear wheel steering device 21 extends in the vehicle width direction. The right and left ends receive pressure oil from a rod 23 connected to the left and right rear wheels 2L, 2R via tie rods 22, 22 and a hydraulic pump 24, respectively.
An actuator 25 that moves the rod 23 in the axial direction (that is, the vehicle width direction) and a rear wheel steering controller 26 that controls the operation of the actuator 25 are provided.

Reference numerals 31, 32, 33 and 34 denote left front wheel 1L, right front wheel 1R, left rear wheel 2L and right rear wheel 2 respectively.
Four wheel speed sensors for detecting the rotational speed (wheel speed) of R, and front wheel steering angle sensors 35 for detecting the steering angles of the front wheels 1L and 1R from the axial displacement of the rod 14, are detected by these sensors 31 to 35. The signal is input to the controller 26. The controller 26 receives the detection signal from the rear wheel steering angle sensor 36 that detects the steering angle of the rear wheels 2L, 2R from the axial displacement of the rod 23, and performs feedback control of the steering of the rear wheels 2L, 2R. ing.

Reference numeral 41 denotes a rear seat switch as seating state detecting means for detecting a state in which a passenger is seated on a rear seat (not shown) at the rear part of the passenger compartment. The rear seat switch 41 is provided on the rear seat, for example. A detection signal of the rear seat switch 41 is also input to the controller 26, and is used for steering control of the rear wheels 2L, 2R by the controller 26. Reference numeral 42 denotes a cancel switch provided around the driver's seat in the front part of the vehicle compartment. The cancel switch 42 regulates correction by the correction means 51 described later in the controller 26.

The rear wheels 2L, 2 by the controller 26
In the steering control of R, the target steering angle θR is calculated according to the flowchart shown in FIG. 2 and using the map stored in advance shown in FIG.

In the target steering angle setting map shown in FIG. 3, the target steering angle θR of the rear wheels is calculated according to the steering angle θH of the front wheels and the vehicle speed V. At low vehicle speeds, the target steering angle θR is set to have the opposite phase to increase the turning performance of the vehicle, and at medium and high vehicle speeds, the target steering angle θR is set to be in phase to increase the steering stability of the vehicle. Is set. Further, as a feature of the present invention, the vehicle speed V is 0 to 10 km.
At the time of extremely low vehicle speed within the range of / h, there are two types of characteristics A and B. The characteristic A indicates that the steering angle θH of the front wheels is a predetermined value θ
In the region below H2, the target steering angle θR linearly increases in the opposite phase direction with the increase of the steering angle θH, and in the region where the front wheel steering angle θH is equal to or larger than the predetermined value θH2, the target steering angle θR is in opposite phase. It is set to be a constant value. Characteristic B is
In a region where the front wheel steering angle θH is equal to or smaller than a predetermined value θH1 (<θH2), the characteristic is the same as the characteristic A.
In the above range, the target steering angle θR has a constant value in the opposite phase, and the constant value is set smaller than that of the characteristic A.

In the flow chart shown in FIG. 2, after starting, first, detection signals from various sensors are read in step S1 and, in step S2, when the vehicle speed V is extremely low at 10 km / h or less. It is determined whether or not there is. Here, the vehicle speed V is obtained from the wheel speeds of the rear wheels 2L, 2R, which are driven wheels, detected by the wheel speed sensors 33, 34.

Then, the determination in step S2 is YES.
When the vehicle speed is extremely low, it is determined in step S3 whether the rear seat switch 41 is ON, that is, whether the occupant is seated on the rear seat. If the determination in step S3 is YES in the seated state, then step S4
To determine whether or not the cancel switch 42 is ON. If the determination is NO, the characteristic B is determined in step S6.
After that, the process proceeds to step S7. When the determination in step S3 is NO in the non-seated state, or when the determination in step S4 is YES, the cancel switch 42
Is ON, the characteristic A is commanded in step S5, and then the process proceeds to step S7. In step S7, the target steering angle θR of the rear wheels is calculated based on the characteristic A or B in the map shown in FIG.

On the other hand, when the determination in step S2 is NO, that is, when the vehicle speed V is equal to or higher than 10 km / h, the process immediately proceeds to step S7, and among the other characteristics in the map shown in FIG. The target steering angle .theta.R of the rear wheels is calculated based on the characteristics according to the vehicle speed of the vehicle, and the process returns.

In the above control flow, steps S3,
By means of S4 and S6, the correcting means 51 for correcting the steering amount to the reverse phase of the rear wheels by changing from the characteristic A to the characteristic B when the occupant is seated on the rear seat to reduce the steering amount to the opposite phase.
Is configured.

Therefore, according to such control, the rear wheels 2L, 2R are out of phase in the direction opposite to the steering direction of the front wheels 1L, 1R at a low vehicle speed based on the characteristics in the map shown in FIG. The turning performance of the vehicle is enhanced, and at middle and high vehicle speeds, the rear wheels 2L, 2R are in-phase in the same direction as the steering direction of the front wheels 1L, 1R, thereby improving the steering stability of the vehicle.

Here, when the vehicle speed V is extremely low at a speed of 10 km / h or less and the steering angle θH of the front wheels is large, the characteristic A
If the target steering angle θR of the rear wheel is set based on the target steering angle θR, the target steering angle θR has a large value of the opposite phase, but when the occupant is seated in the rear seat, the selection of the characteristic is changed from the characteristic A. The target steering angle θR is changed to the characteristic B and the target steering angle θR of the rear wheel is calculated based on the characteristic B, so that the target steering angle θR becomes smaller than that in the non-seated state.
Therefore, the rear wheels 2L and 2R are prevented from being largely steered in the opposite phase, and the occupant on the rear seat feels uncomfortable due to the large steering of the rear wheels 2L and 2R to the opposite phase. Can be prevented beforehand, and the riding comfort can be improved.

In addition, in this embodiment, the correction for reducing the steering amount of the rear wheels to the opposite phase due to the change from the characteristic A to the characteristic B can be freely regulated by the cancel switch 42. , The usability can be improved.

In the above embodiment, a map as shown in FIG. 3 is used to steer the rear wheels according to the steering angle θH of the front wheels and the vehicle speed V. However, the present invention uses the map shown in FIG. As described above, the present invention can be applied to the case where the rear wheels are steered based on the steering ratio (θR / θH) between the front wheels and the rear wheels. In this case, when the occupant is seated on the rear seat, the steering of the rear wheels may be controlled using the characteristic B instead of the characteristic A.

[0025]

As described above, according to the rear wheel steering apparatus of the present invention, when the occupant is seated on the rear seat, the correction is performed so as to reduce the amount of steering of the rear wheels to the opposite phase. As a result, the rear wheels can be prevented from being largely steered in the opposite phase to the front wheels, so that the occupants on the rear seats can be prevented from feeling uncomfortable,
Riding comfort can be improved.

In particular, according to the second and third aspects of the present invention, the steering amount of the rear wheels to the opposite phase is reduced only at an extremely low vehicle speed where the rear wheels are largely steered in the opposite phase or at a large steering angle of the front wheels. Since such correction is performed, it is possible to effectively achieve compatibility between turning performance and riding comfort.

According to the fourth aspect of the present invention, the above-described correction can be freely regulated by the cancel switch, so that the usability by the driver can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a drive system and a steering system of a vehicle according to an embodiment of the present invention.

FIG. 2 is a flowchart for setting a target steering angle in rear wheel steering control.

FIG. 3 is a diagram showing a map for setting a target steering angle.

FIG. 4 is a diagram showing a map for setting another target steering angle.

[Explanation of symbols]

 1L, 1R Front wheel 2L, 2R Rear wheel 41 Rear seat switch (seating state detection means) 42 Cancel switch 51 Correction means

Continuation of the front page (72) Inventor Tatsuya Akita 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (56) References JP-A-2-27463 (JP, A) JP-A-62-128883 ( JP, A) JP-A-2-262472 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/00 B62D 7/14

Claims (4)

(57) [Claims] 1. A seating state for detecting a state in which an occupant is seated on a rear seat in a rear wheel steering device of a vehicle that steers a rear wheel at least in an opposite phase to a direction opposite to a steering direction of a front wheel in accordance with steering of a front wheel. Detection means, and correction means for receiving a signal from the detection means and correcting the steering amount of the rear wheel to the opposite phase when the occupant is seated in the rear seat. Rear wheel steering system for vehicles. 2. The rear wheel steering apparatus according to claim 1, wherein the correction means is configured to perform a correction for reducing a steering amount of the rear wheels to the opposite phase only at an extremely low vehicle speed. 3. The rear wheel steering of a vehicle according to claim 1, wherein said correction means is configured to perform a correction to reduce a steering amount of the rear wheels to the opposite phase only when a front wheel steering angle is large. apparatus. 4. The rear wheel steering apparatus according to claim 1, further comprising a cancel switch for restricting the correction by said correction means.