JPH0443170A - Rear wheel steering mechanism for vehicle - Google Patents

Abstract

PURPOSE:To suppress the sharp displacement of a driving shaft by installing a damper for gently carrying out restoration operation on the return to a neutral position of the driving shaft by a centering spring, in the constitution in which a clutch is interposed between a rear wheel steering mechanism and a driving source. CONSTITUTION:A rear wheel steering device 20 is equipped with a rear wheel steering mechanism 25 consisting of a rack & pinion type steering gear mechanism 24, servomotor 26 for driving the mechanism 24, reduction gear 27 formed integrally with the servomotor 26, and a clutch 28 installed between the steering gear mechanism 24 and the servomotor 26. A centering spring 29 for holding a rear wheel steering rod 23 at a neutral position is installed on the rod 23. A damper characteristic varying type damper 30 for gently carrying out the restoration operation to a neutral position of the rear wheel steering rod 23 by the centering spring 29 is installed. The characteristic of the damper 30 is made soft by a controller 31 in the low speed operation, and made hard in the high speed operation, and when a trouble is detected, change to the harder characteristic is performed.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a rear wheel steering device for a vehicle, and more particularly, to a vehicle rear wheel steering device that rotates the rear wheels via a drive shaft connected to the left and right rear wheels in response to the steering of the front wheels. The present invention relates to a rear wheel steering device for a vehicle equipped with a rear wheel steering mechanism for steering.

(Prior Art) In a four-wheel steering device that steers the rear wheels in the opposite direction or in the same direction as the front wheels in response to the steering of the front wheels, a configuration in which the rear wheels are steered by a motor is, for example, a special technique. 1977
As is known from Japanese Patent No. 44568, in a rear wheel steering device configured to steer the rear wheels by a motor, there is a return mechanism for returning the rear wheels from the steered position to the neutral position when the device fails. The motor is connected to the rear wheel steering system via a clutch, and in the event of a failure, the clutch is disconnected and the centering spring moves the rear wheels to the steered position. It is designed to return to the neutral position from

(Problem to be Solved by the Invention) As mentioned above, when the centering spring returns the rear wheels from the steering position to the neutral position in the event of a failure, the return to the neutral position due to the action of the centering spring is comparatively difficult. Therefore, depending on the driving condition of the vehicle, there is a possibility that the behavior of the vehicle may become unstable.

Therefore, the present invention provides a rear wheel steering mechanism that steers the left and right rear wheels via a drive shaft connected to the left and right rear wheels in response to the steering of the front wheels, and a link between the steering mechanism and its drive source. A rear wheel steering device for a vehicle, comprising a centering spring that returns the drive shaft to a neutral position when a disposed clutch is disengaged,
It is an object of the present invention to prevent the behavior of the vehicle from becoming unstable by configuring the drive shaft to be able to suppress sudden displacement when the drive shaft is returned to the neutral position by the centering spring.

(Means for Solving the Problems) In order to solve the above problems, the present invention is characterized by the following configuration.

First, the invention according to the first claim of the present application (hereinafter referred to as the first invention) provides for steering the left and right rear wheels via a drive shaft connected to the left and right rear wheels in response to the steering of the front wheels. a rudder mechanism; a clutch disposed between the steering mechanism and its drive source;
A rear wheel steering device for a vehicle comprising a centering spring that returns the drive shaft to a neutral position when the clutch is disengaged, wherein the centering spring is provided between the drive shaft and the vehicle body and returns the drive shaft to the neutral position. The present invention is characterized in that a damper is provided to cause the return operation to be performed slowly when the return operation is performed.

Further, the invention according to the second claim of the present application (hereinafter referred to as the second invention) includes, in addition to the configuration of the first invention, a failure detection means for detecting a failure of the rear wheel steering device, and the failure detection means. The present invention is characterized in that a damper characteristic variable means is provided for making the damper characteristics hard when a failure is detected.

Furthermore, the invention according to the third claim of the present application (hereinafter referred to as the third invention) includes, in addition to the configuration of the first invention, a failure detection means for detecting a failure of the rear wheel steering device, and a failure detection means for detecting the vehicle speed. Vehicle speed detection means; Based on the signal from the vehicle speed detection means, the characteristics of the damper are made soft at low speeds and hard at high speeds, and when a failure is detected by the failure detection means, the characteristics of the damper are set to be even harder than at high speeds. The present invention is characterized in that a damper characteristic variable means is provided.

(Function) According to the first invention, when the drive shaft is returned to the neutral position by the centering spring when the clutch is disengaged, the drive shaft is gently returned to the neutral position by the damper, Sudden displacement of the drive shaft is suppressed, thereby preventing the behavior of the vehicle from becoming unstable.

Further, according to the second invention, when a failure of the rear wheel steering device is detected by the failure detection means, the damper characteristics are set to hard by the damper characteristic variable means, so that when the failure occurs, the damper characteristics are set to hard. When the clutch is disengaged and the drive shaft is returned to the neutral position by centering, the drive shaft is gently returned to the neutral position by the damper, thereby suppressing sudden displacement of the drive shaft. , the behavior of the vehicle is prevented from becoming unstable.

Furthermore, according to the third invention, the characteristics of the damper are varied depending on the driving condition, and at low speeds, the characteristics of the damper are set to be soft, so that the rear wheels are smoothly steered with good responsiveness as the front wheels are steered. At the same time, at high speeds, the damper characteristics are set to hard, which effectively suppresses unnecessary displacement of the drive shaft connected to the left and right rear wheels, thereby preventing disturbances from causing vehicle behavior. This will prevent it from becoming stable. In addition, in the event of a failure of the rear wheel steering device,
The damper characteristics are set even harder than when driving at high speeds, so in the event of a failure, when the clutch is disengaged and the drive shaft is returned to the neutral position by centering, the damper will quickly return the drive shaft to the neutral position. As a result, sudden displacement of the drive shaft is suppressed, and the behavior of the vehicle is prevented from becoming unstable.

(Example) Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 1, the vehicle according to this embodiment includes a front wheel steering device 10 that steers left and right front wheels 2, 2 by operating a steering wheel 1, and a front wheel steering device 10 that steers left and right front wheels 2, 2 by operating a steering wheel 1. Rear wheel steering device F20 that steers the left and right rear wheels 3.3
and has.

The front wheel steering device 10 is arranged in the vehicle width direction, and has tie rods 11.11 and knuckle arms 12 at both ends.
A front wheel steering rod 13 is connected to the left and right front wheels 2.2 through a front wheel 12, and a rack-and-binion type steering gear mechanism 14 displaces the front wheel steering rod 13 in the left-right direction in response to the operation of the handle 1. The front wheel 2 is rotated in the direction of operation of the handle 1 by an angle corresponding to the amount of operation.
．． 2 is designed to be steered.

The rear wheel steering device 20 is arranged in the vehicle width direction and has both ends connected to the left and right rear wheels 3.3 via tie rods 21.21 and knuckle arms 22, 22. A rack-and-nion type steering gear mechanism 2 that displaces the rod 23 and the steering rod 23 in the left-right direction.
4, a servo motor 26 that drives the steering gear mechanism 24 and a reduction gear 27 integrated therewith, and a clutch 28 provided between the steering gear mechanism 24 and the servo motor 26. and has. Actually, the rear wheel steering rod 23 has the rod 2
A centering spring 29 is provided to hold the rear wheel steering rod 23 in the neutral position, and a damper 30 with variable damper characteristics is provided to smoothly return the rear wheel steering rod 23 to the neutral position by the centering spring 29. It is being

The left and right rear wheels 3.3 are steered in a direction corresponding to the direction of rotation of the servo motor 26 by an angle corresponding to the amount of rotation thereof.

Furthermore, this rear wheel steering device 20 includes the servo motor 2.
6. A controller 31 that controls the operation of the clutch 28 and the damper 30 is provided, and the controller 31 receives a signal from the front wheel steering angle sensor 32 that detects the steering angle of the steering wheel 1 (the steering angle of the front wheels 2.2). , a signal from a vehicle speed sensor 33 that detects the vehicle speed, a signal from an encoder 34 that detects the rotational position of the servo motor 26, and a signal that is interlocked with the steering gear mechanism 24 via a pair of gears 35 and 36. Signals from two steering angle sensors 37 and 38 that detect the steering angle of the wheels 3.3 are input. Based on the above input signals, this controller 31 controls the rear wheels 3 and 3 when the front wheels 2.2 are steered.
determines the steering direction and amount of steering, and at low speeds, the front wheels 2 and 2 are steered in the opposite direction (opposite phase), and at high speeds, the front wheels 2 and 2 are steered in the opposite direction (opposite phase).
The servo motor 26 is driven so as to steer the rear wheels 3, 3 in the same direction (same phase) as .degree.2.

Note that the controller 31 includes a servo motor 26, a clutch 28, and a damper 30 based on each input signal.
and an abnormality detection C that detects an abnormality in the control CPU and an abnormality in the rear wheel steering system.
PU is built in, and failures of the rear wheel steering system detected by the abnormality detection CPU include a failure of the servo motor 26, a failure of the clutch 28, a failure of the damper 30, a failure of the encoder 34, and a failure of the rear wheel steering system. There is a failure in the steering angle sensors 37 and 38. Further, a warning lamp 39 is connected to the controller 31 to notify the driver when an abnormality is detected by the abnormality detection CPU.

Here, based on FIG. 2, the structure of the rear wheel steering mechanism 25 and its surroundings will be explained in more detail. The above-mentioned centering spring 29 is installed internally, and the above-mentioned damper 30 is provided on the side of the centering spring 29. This damper 30
A piston 41 provided integrally with the rear wheel steering rod 23, left and right hydraulic chambers 42a, 42b partitioned by the piston 41, and both hydraulic chambers 42a, 42b.
a communication path 43 that communicates with the communication path 43, an orifice 44 provided in the communication path 43, and a solenoid valve 45 that changes the damper characteristics by variably adjusting the passage cross-sectional area of the orifice 44.
and has.

Further, the casing 40 supports a servo motor 26, a reduction gear 27, and a clutch 28, and the output of the servo motor 26 is transmitted to the rear wheel steering rod 23 via the clutch 28 and the steering gear mechanism 24. As a result, the left and right rear wheels 3.3 are steered in the opposite direction or the same direction as the front wheels 2.2 in accordance with the steering of the front wheels 2.2.

Next, the specific operation of steering control of the rear wheels 3, 3 by the controller 31 will be explained according to the flowchart shown in FIG. 3. First, in step S1, the controller 31 determines whether a failure has occurred. If it is determined that there is no malfunction, it is determined in step S2 whether the vehicle is turning based on the signals from the front wheel steering angle sensor 32 and the rear wheel steering angle sensors 37 and 38. If the vehicle is turning,
In step S, the solenoid valve 45 is operated to open the orifice 44.
When the damper 30 is fully open, the characteristics of the damper 30 are set to the softest state W.
Set to IC1, and if not turning, step S
4, it is determined whether the vehicle is traveling at high speed based on the signal from the vehicle speed sensor 33, and if it is not traveling at high speed, step S
3, and if the vehicle is running at high speed, step S5 is executed.
At this point, the solenoid valve 45 is operated to slightly narrow the orifice 44, thereby setting the damper characteristic to a state C2 that is slightly harder than 01. This is to suppress the displacement of the rear wheel steering rod 23 connected to the left and right rear wheels 3, 3 in the left and right direction during high-speed driving, and to prevent the vehicle from becoming unstable due to disturbance elements. be. On the other hand, when it is determined that there is a failure in step S1, step S
6, the alarm lamp 39 is turned on, and in step S7,
Recognize failure mode Next, in step S8, it is determined whether the control CPU built in the controller 31 is out of order based on the recognition result in step S, and if it is out of order, the control CPU of the damper 30 is set in step S9. Characteristics in the hardest condition! After setting B C4, step 81
8, the clutch 28 is disengaged, and the two-wheel steering state is established. Further, when it is determined in step S8 that there is no failure, it is determined in step SIO whether the servo motor 26 is in failure, and if it is failure, step S9
Subsequently, step 81g is executed. Further, when it is determined that there is no failure, the encoder 34 as a rear wheel steering angle detector and the rear wheel steering angle sensors 37 and 38 are activated in step S.
When the determination is NO, that is, when it is determined that there is no failure, the steering position of the rear wheels 3.3 is determined based on the output signal from the rear wheel steering angle detector in step S12. Recognize. Further, in step S11 above, Y
When it is determined to be ES, that is, when it is determined that the rear wheel steering angle detector is malfunctioning, it is determined in step SI3 whether all the signals of the rear wheel steering angle detector are inconsistent, and if YES,
Following step S9, step Sta is executed, and
If No, in step S14, signals from the two normally operating rear wheel steering angle detectors
Recognizes the steering position of the vehicle. After that, the controller 31
Step S1 is executed, and the left and right rear wheels 3, 3 are steered in the opposite direction (in opposite phase) to the front wheels 2, 2 based on the signals from the front wheel steering angle sensor 32 and the rear wheel steering angle sensors 37, 38. If the answer is NO, that is, if the rear wheels 3.3 are being steered in the same direction, the characteristics of the damper 30 are set to the hardest state C4 in step S16,
Further, in the case of YES, that is, when it is determined that the rear wheels 3, 3 are steered in the opposite direction, step SF is executed, and the damper characteristic is changed to a state mci (Ct
<C2<c, <C4). Then step 8
1g, the clutch 28 is disengaged, and the centering spring 29 returns the rear wheels 33 to the neutral state, resulting in a two-wheel steering state.

As described above, when the rear wheel steering device 20 breaks down, the clutch 28 is disengaged and the rear wheel steering rod 23 is displaced by the action of the centering spring 29 to return the rear wheels 3.3 to the neutral position. The return of the rear wheel 3.3 to the neutral position is performed gradually based on the characteristics of the damper 30, and the sudden return of the rear wheel 3.3 to the neutral position is suppressed. This will surely prevent the vehicle from becoming unstable.

Further, the characteristics of the damper 30 are varied depending on the driving condition,
At low speeds, the damper characteristics are set to a soft state *Cs, allowing the rear wheels 3.3 to be steered smoothly and responsively in conjunction with the steering of the front wheels 2.2, while at high speeds, the damper characteristics are set to a soft state *Cs. As a result, displacement of the rear wheel steering rod 23 connected to the left and right rear wheels 3.3 in the left and right direction is suppressed, and the behavior of the vehicle becomes unstable due to external disturbances. This will be prevented.

(Effects of the Invention) As described above, according to the first invention, when the centering spring returns the drive shaft to the neutral position when the clutch is disengaged, the damper gently returns the drive shaft to the neutral position. As a result, sudden displacement of the drive shaft is effectively suppressed, and the behavior of the vehicle is prevented from becoming unstable.

Further, according to the second invention, when a failure of the rear wheel steering device is detected by the failure detection means, the damper characteristic variable means sets the damper characteristics to hard, so that when the failure occurs, the damper characteristic is set to hard.・When the drive shaft is returned to the neutral position by centering after cutting off the brake, the damper gently returns the drive shaft to the neutral position, which effectively prevents sudden displacement of the drive shaft. This prevents the behavior of the vehicle from becoming unstable.

Furthermore, according to the third invention, the characteristics of the damper are varied depending on the driving condition, and at low speeds, the damper characteristics are set to be soft, so that the rear wheels can be smoothly steered with good responsiveness as the front wheels are steered. At the same time, at high speeds, the damper characteristics are made hard, suppressing the displacement of the drive shaft connected to the left and right rear wheels, and preventing the behavior of the vehicle from becoming unstable due to external disturbances. In addition, when the rear wheel steering device fails, the damper characteristics are set even harder than when driving at high speeds, so that when the failure occurs, the clutch is disengaged and the drive shaft is returned to the neutral position by centering. The drive shaft is gently returned to the neutral position by the damper, thereby effectively suppressing sudden displacement of the drive shaft and preventing the behavior of the vehicle from becoming unstable.

[Brief explanation of the drawing]

The drawings show an embodiment common to the first to third inventions, and FIG. 1 is an overall system diagram of a steering device for a vehicle equipped with a rear wheel steering device, and FIG. 2 is a configuration of the rear wheel steering device. FIG. 3 is an enlarged sectional view showing the configuration of the rear wheel steering mechanism and its surroundings, and FIG. 3 is a flowchart showing the control operation by the controller. 2... Front wheel, 3... Rear wheel, 20... Rear wheel steering device, 23... Drive shaft (rear wheel steering rod), 25... Rear wheel steering mechanism, 26... Drive means (servo motor), 2
8...Clutch, 29...Centering spring, 30
. . . damper, 31 . . . failure detection means, damper characteristic variable means (controller), 33 . . . vehicle speed sensor.

Claims (3)

[Claims] (1) A rear wheel steering mechanism that steers the left and right rear wheels via a drive shaft connected to the left and right rear wheels in response to steering of the front wheels, and a rear wheel steering mechanism disposed between the steering mechanism and its drive source. A rear wheel steering device for a vehicle comprising a clutch and a centering spring that returns the drive shaft to a neutral position when the clutch is disengaged, wherein the centering spring is provided between the drive shaft and the vehicle body, and the centering spring controls the drive shaft. A rear wheel steering device for a vehicle, characterized in that a damper is provided to gently perform a return operation when returning to a neutral position. (2) A rear wheel steering mechanism that steers the left and right rear wheels via a drive shaft connected to the left and right rear wheels in response to steering of the front wheels, and a rear wheel steering mechanism disposed between the steering mechanism and its drive source. A rear wheel steering device for a vehicle comprising a clutch and a centering spring that returns the drive shaft to a neutral position when the clutch is disengaged, wherein the centering spring is provided between the drive shaft and the vehicle body, and the centering spring controls the drive shaft. A damper that gently performs a return operation when returning to a neutral position, a failure detection means that detects a failure of the rear wheel steering device, and a damper that hardens the characteristics of the damper when the failure detection means detects a failure. What is claimed is: 1. A rear wheel steering device for a vehicle, characterized in that a characteristic variable means is provided. (3) A rear wheel steering mechanism that steers the left and right rear wheels via a drive shaft connected to the left and right rear wheels in response to steering of the front wheels, and a rear wheel steering mechanism disposed between the steering mechanism and its drive source. A rear wheel steering device for a vehicle comprising a clutch and a centering spring that returns the drive shaft to a neutral position when the clutch is disengaged, wherein the centering spring is provided between the drive shaft and the vehicle body, and the centering spring controls the drive shaft. A damper that performs the return operation slowly when returning to the neutral position, a vehicle speed detection means that detects the vehicle speed, a failure detection means that detects a failure of the rear wheel steering device, and a signal from the vehicle speed detection means. Based on this, the damper characteristic is set to be soft at low speeds and hard at high speeds, and damper characteristic variable means is provided for making the characteristics of the damper even harder than at high speeds when a failure is detected by the failure detection means. A rear wheel steering device for a vehicle, characterized by: