JPS61146682A - Front and rear wheel steering device for car - Google Patents

Abstract

PURPOSE:To prevent the swing of rear wheels by feedback-controlling the revolution of a motor by a rear-wheel steering-angle signal so that the actual steering-angle for the rear-wheels and the ideal steering-angle coincide with each other and locking the input supplied into a rear-wheel steering mechanism from the rear-wheel side when no electric current flows in the motor. CONSTITUTION:In a control circuit 4, the ideal rear-wheel steering angle is calculated on the basis of the front-wheel steering-angle of a front-wheel steering-angle sensor 2 and the car-speed signal of a car-speed sensor 3, and the actual rear-wheel steering- angle obtained from the rear-wheel steering-angle signal of a rear-wheel steering-angle sensor 10 and the ideal steering angle are comparison-calculated, and an electric motor 5 is driven, and the revolution of the motor 5 is controlled so that the ideal rear-wheel steering-angle and the actual rear-wheel steering-angle always coincide. Since a worm gear which consists of a cylindrical worm 6 and a worm wheel 7 and is provided with a unidirectional torque transmission function for the output of the motor 5 and has a small lead angle is provided, an external force applied into a rear-wheel steering apparatus from the rear-wheel 14 side is locked by a worm gear, and the generation of swing of rear wheels 14 in the case when no electric current flows in the motor 5 is prevented.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a front and rear wheel steering device for an automobile.

Conventional technology In automobiles, in order to improve the dynamic performance of the vehicle body with respect to steering during steering operation, the rear wheels are configured to be able to rotate in a kingpin rotation similar to the -J wheels, and the rear wheels are configured to rotate in a kingpin rotation manner in conjunction with the steering of the front wheels. Front and rear wheel steering devices that perform rear wheel steering have been developed over the years, and have already been disclosed, for example, in Japanese Patent Application Laid-Open No. 59-26363.

Problems to be Solved by the Invention The conventional front and rear wheel steering devices as described above transfer the steering operation of the front wheels based on the steering operation of the steering wheel to the rear wheel steering mechanism using a mechanical transmission means such as an operating shaft. Generally, the structure is such that the rear wheels are steered by this transmission.

Normally, in front and rear wheel steering systems, the ideal steering direction and steering angle of the rear wheels relative to the steering direction and steering angle of the driving wheels differ depending on the vehicle speed. It is said that it is better to steer the rear wheels in the opposite direction to improve the turning ability of the vehicle body, and in high-speed driving ranges to steer the rear wheels in the same direction as the front wheels to improve responsiveness to steering.

Therefore, in the above-mentioned conventional device in which the front wheel steering operation is transmitted to the rear wheels by a mechanical transmission means such as an operating shaft, and thereby υ rear wheel steering is performed, the mechanical transmission means is In addition, a transmission mechanism must be provided to change the transmission ratio, and a rear wheel steering direction control mechanism must be provided to change the transmission direction depending on the vehicle speed, making the structure of the mechanical transmission means extremely complicated. However, it has the disadvantage that space constraints are too severe, and it is also extremely expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a front and rear wheel steering device that can solve the conventional problems as described above.

Means for Solving All Problems The present invention uses an electric motor as a power source for steering operation of the rear wheels, and uses a steering angle signal of the front wheels and a vehicle speed signal of a vehicle speed sensor, which are operated by rotation of the steering wheel, to operate the steering operation. a flit control circuit which calculates the ideal rear wheel steering angle by and compares the actual rear wheel steering angle obtained based on the rear wheel steering angle signal of the rear wheel steering angle sensor with the ideal rear wheel steering angle and outputs the result. The output is configured to control the rotational drive of the electric motor, and a one-way torque transmission function that locks the load from the rear wheel side in a power transmission system connecting the electric motor to the rear wheel steering mechanism. It is characterized by intervening a ψ ohm gear with a The control circuit calculates an ideal rear wheel steering angle using the front wheel steering angle signal and the vehicle speed signal, outputs an output to the 11-motor, and rotates the electric motor. The rotation of the motor is feedback-controlled so that the actual rear wheel steering angle always matches the ideal rear wheel steering angle.
When the electric motor is controlled by 15G and no current is flowing through the electric motor, the external force applied to the rear wheel steering mechanism from the rear wheel side is locked by the worm gear to prevent the rear wheels from wobbling.

Example An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a steering handle, and by rotating the steering handle 1, a commonly used front wheel steering device (not shown) such as a rack or pinion type is actuated. The wheels are designed to steer to the right or left. Although the front wheel steering device is not shown, any conventionally known mechanism may be employed.

2 is a front wheel steering angle sensor that detects the 10 rotation rotation angle of the steering wheel or the turning operation amount of the front wheel steering device or ff (a front wheel steering angle sensor that detects the actual wheel steering angle and issues a signal according to the front wheel steering angle; 3 detects the vehicle speed The front wheel steering angle signal from the front wheel steering angle sensor 2 and the vehicle speed signal from the vehicle speed sensor 3 are input to a control circuit 4.

5 is an electric motor, and as shown in FIG. 2, the rotational drive of the electric motor 5 is transmitted to a pinion gear 8 through a worm gear consisting of a cylindrical worm 6 and a worm wheel 7 that meshes with the cylindrical worm 6. Rack shaft 9f: The rack shaft 9 is made vertically in the axial direction.
Due to the axial operation of the rear wheels 12, 12 and knuckle arms 13, 1:l, the rear wheels 14, 14 are rotated around the kingpin, and the rear wheels are steered.

The above electric motor 5. The pinion gear 8, rack shaft 9, etc. driven via the worm gear 6.7 are incorporated into the gear box 11 to form one rear wheel steering system.
It consists of

The worm gear consisting of the cylindrical worm 6 and the worm wheel 7 has a one-way torque transmission function in which the rotational drive of the tta motor 5 can be transmitted to the pinion gear 8, but the load from the rear wheel 14 side is locked and not transmitted to the electric motor 5. A worm gear with a small lead angle is used.

A rear wheel steering angle sensor 10 detects a rear wheel steering angle and generates a signal corresponding to the rear wheel steering angle.A rear wheel steering angle signal from the rear wheel steering angle sensor 10 is input to the control circuit 4.

The rear wheel steering angle may be detected by the amount of axial displacement of the rack shaft 9 as shown in FIG.
It may be detected based on the amount of rotational angular displacement of the output shaft, or alternatively, it may be detected based on the actual steering angle of the rear wheels 14.

In the above, the control circuit 4 controls the steering wheel 1
When operating, the ideal rear wheel steering angle at that time is calculated based on the front wheel steering angle signal of the front wheel steering angle sensor 2 and the vehicle speed signal of the vehicle speed sensor 3, and further, based on the rear wheel steering angle signal of the rear wheel steering angle sensor 10. The actual steering angle of the rear wheels determined by the above calculation is compared with the ideal steering angle of the rear wheels, and the result is output as, for example, an electric pulse width signal to drive the electric motor 5, thereby determining the ideal steering angle of the rear wheels. The rotation of the electric motor 5 is controlled so that the actual steering angles of the rear wheels always match.

The ideal steering angle δR of the rear wheels is expressed as δR=θ·f (V) (1), where the front steering angle is θ and the vehicle speed is ■.

In the above, f (V) becomes negative in the low vehicle speed range of about 501b/H or less, as shown in FIG.
It is an increasing function that approaches +1 as the vehicle speed increases from 1 m, /H, and the control circuit 4 calculates the ideal rear wheel steering angle δRt- based on the above equation (1), so that it becomes negative in the low vehicle speed range. The electric motor 5 is rotated by a predetermined number of rotations so as to steer the rear wheel in the direction opposite to the direction in which the front wheels are steered, and the rear wheels are rotated at a predetermined angle in the positive direction, that is, in the same direction as the front wheel steering direction in the vehicle speed range. The ia drive motor 5 can be rotated to effect steering.

In the above, in the present invention, as a means for transmitting the output of the electric motor 5 to the pinion gear 8, a worm gear having a unidirectional torque transmission function and having a unidirectional torque transmission function, which is composed of a cylindrical worm 6 and a worm wheel 7, is adopted, so that the rear wheel 1
The external force applied manually to the rear wheel steering device from the 4 side is locked by the worm gear, and no wobbling of the rear wheel 14 due to the external force occurs when no current flows through the electric motor 5.

Effects of the Invention As described above, according to the present invention, the power source for the steering operation of the rear wheel steering device is 1 yen! Rotation 'fr of the electric motor: The ideal steering angle of the rear wheels is calculated based on the front wheel steering angle signal and the vehicle speed signal at that time, and the output of the control circuit is set to a predetermined output. By performing feedback control on the above output based on the rear wheel steering angle signal, it is possible to obtain a front and rear wheel steering system in which the actual rear wheel steering angle always matches the ideal steering angle. By inserting a worm gear with a unidirectional torque transmission function that locks the load from the rear wheels into the drive power transmission system leading to the wheel steering mechanism, there is no wobbling of the rear wheels when no current is flowing to the electric motor. It is possible to perform stable rear wheel steering angle control without any problems, and has a very simple structure with fewer components as a whole.It is much cheaper than conventional ones, and it also has a control element for rear wheel steering. In addition to the front wheel steering angle and vehicle speed of the above embodiment, for example, it is extremely simple and easy to add elements such as the yaw rate change rate and lateral acceleration of the vehicle body to perform detailed control. Furthermore, since one power source for rear wheel steering is an electric motor, the operating load on the steering wheel is much smaller compared to conventional front and rear wheel steering devices, and this can bring about many valuable effects. .

[Brief explanation of the drawing]

Fig. 1 is a schematic plan view of a rear wheel steering mechanism showing an embodiment of the present invention, Fig. 2 is an enlarged perspective view of the drive power transmission system from the electric motor in Fig. 1 to the rackshaft 7)K, and Fig. 3 is a diagram showing an example of a vehicle speed function for determining the ideal rear wheel steering angle. 1°°° Steering handle, 2... Front wheel steering angle sensor, 3... Vehicle speed sensor, 4... Control circuit, 5...
Electric motor, 6... Cylindrical worm, 7... Worm wheel, 8... Pinion gear, 9... Rack shaft, 10... Rear wheel steering angle sensor, 14... Rear wheel. −
that's all

Claims (1)

[Claims] An electric motor is used as the power source for steering the rear wheels, and the ideal steering angle of the rear wheels is calculated based on the steering angle signal of the front wheels, which is activated by rotation of the steering wheel, and the vehicle speed signal of the vehicle speed sensor. The rotational drive of the electric motor is controlled by the output of a control circuit that compares and calculates the rear wheel ideal steering angle with the rear wheel ideal steering angle determined based on the rear wheel steering angle signal of the steering angle sensor. An automobile characterized in that the driving force transmission system from the electric motor to the rear wheel steering mechanism is provided with a worm gear having a one-way torque transmission function for locking the load from the rear wheels. Front and rear wheel steering device.