JPH0221341Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a steering device for an automobile that drives a steering mechanical system of a steered wheel by a driver's rotational operation of a steering wheel.

This type of steering device for automobiles is usually of the front wheel steering type, and is also a mechanism that creates a certain difference in the deflection angle between the inner and outer front wheels in order to allow the vehicle to turn smoothly. It is becoming. However, although four-wheel steering systems have been put into practical use for special vehicles, the above-mentioned relationship between the inner and outer wheels remains the same, making the mechanical system complex and expensive, as well as increasing the weight, so it is not recommended for use in regular vehicles in particular. is difficult.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a steering device for an automobile that is lightweight and inexpensive and allows switching between a plurality of steering modes.

In order to achieve this objective, the present invention provides a steering mechanical system that is independently driven by an electric motor for each of the front, rear, left, and right wheels.
A steering wheel that is rotated, a steering command signal generator that outputs a steering command direction signal and a steering command angle signal in response to the rotation of the steering wheel, and a steering command signal generator that outputs a steering command direction signal and a steering command angle signal in response to the rotation of the steering wheel; a reaction force actuator attached to a rotating mechanism rotatably driven by the steering wheel; and a reaction force actuator configured to generate a reaction force corresponding to the steering angle and vehicle speed by inputting steering direction, steering angle, and vehicle speed signals. A reaction force drive control means for driving and controlling the actuator, a motor drive control means for receiving the output signal of the steering command signal generator and operating the electric motors belonging to each mechanical steering system, and a steering command signal generator that are identical to each other. A steering mode changeover switch is provided for switching the output of at least some of the motor drive control means in response to the output signal.

Accordingly, when a steering wheel independent of the steering system is rotated, the electric motor drives and controls the steering system in response to a steering command direction signal and a steering command angle signal output from the steering command signal generator. At this time, the reaction force actuator applies a reaction force to the steering wheel that increases accordingly as one or both of the steering angle and vehicle speed increases.
The four wheels are independently steered by their own electric motors, and a plurality of steering modes can be operated by switching the steering mode changeover switch.

Next, the present invention will be explained based on the illustrated embodiments.

In FIG. 1, 1 and 1' are linear steering actuators that respectively drive the front right wheel and the front left wheel via links 2, 2' and knuckle arms 3, 3', and 4 and 4' are drive shafts.
5 and 5' are linear steering actuators that similarly drive the rear right wheel and the rear left wheel, respectively, via links 6, 6' and knuckle arms 7, 7'. These actuators 1, 1', 5,
5' can be formed, for example, as a rod linearly driven by a ball screw which is rotationally driven by an electric motor. 10 is a steering column attached to a dart board, for example, and includes a steering wheel 11, a gear system 12 rotationally driven by the steering column, and a gear system 12 serving as a rotation mechanism that rotates the steering column to generate a steering command direction signal and a steering command angle. ( ₁ ) A steering signal generator 13 that outputs a steering command signal a consisting of a signal and ( ₁ ) a steering correction command angle corrected for the Atskermann-Giant geometry and the outer wheel; and ( ₂ ) a steering wheel that is about to rotate. The motor 11 is provided with a DC motor 14, which together with a gear system 12 constitutes a reaction force actuator, so as to increase or decrease the steering force required by the driver according to vehicle speed, wheel deflection angle, and other operating conditions. 20
is a reaction force drive control circuit, which reduces the centripetal acceleration generated on a curve by operating the steering wheel to a certain level or less with respect to the steering command angle output from the steering command signal generator 13 and the vehicle speed v detected by the vehicle speed sensor 21. For example, a drive input corresponding to ₁ v ² is applied to the DC motor 14 with a polarity opposite to the direction of rotation of the steering wheel so as to generate a reaction force proportional to ₁ v ² . The steering command signal a is conveyed by an electric wire or an optical fiber provided with a photoelectric converter at the transmitting and receiving ends. 30, 30',
31, 31' are steering actuators ₁ , 1 _' , 5,
This is a drive control circuit that operates the electric motors belonging to 5'. As shown in Fig. 2, S1 has two modes: Mode 1, in which the front wheels are steered based on the Atskermann-Giant geometry as in the past; Mode 2, in which the rear wheels are also steered by the Atskermann-Giant to reduce the turning radius; This is a steering mode changeover switch that switches between Mode 3, which steers the wheels in the same direction at the same deflection angle, and enables width-aligning. S2 is a switching circuit for discriminating the steering command direction based on the steering command direction signal and supplying the steering command signal a for the outer wheel ₂ during steering, and S3 is the selection from the steering mode changeover switch S1 in mode 2. A switching circuit S4 is a switching circuit for supplying steering command signals ₁ and ₂ to the rear wheel drive control circuits 31 and 31' according to the signal, and a switching circuit S4 connects both inputs of the front wheel drive control circuits 30 and 30' in mode 3. This is a switching circuit for making a steering command signal of ₁ and outputting a steering command signal of - by passing the inputs of the drive control circuits 31 and 31' for the rear wheels through an inverting amplifier 32.

The polarity of the steering command signal generator 13 changes depending on the direction of rotation with respect to the reference position of the steering wheel 11, and the level changes depending on the amount of rotation.
In the case of a potentiometer that outputs a DC voltage corresponding to ₁ and ₂ , the reaction force drive control circuit 20 is, for example, entirely of an analog circuit type, and as shown in FIG. A squaring unit 22 that squares, a multiplication unit 23 that calculates ₁ v ² between the absolute value of the steering command angle ₁ and v, a rotation direction identification unit 24 that identifies the direction of change of 1, and a rotation direction identification unit 24 that determines the direction of change of ₁ , and a The power amplifier 25 outputs a polar drive input to the DC motor 14. On the other hand, the electric motors of each steering actuator 1, 1', 5, 5' are DC servo motors with tachodynamics, and as shown in Fig. 4, the shock absorber rods 8 of each wheel are coupled to rotate in the direction of rotation from the reference position. A potentiometer-type steering angle sensor 9 is installed that outputs a DC voltage whose polarity changes according to the steering angles ′ ₁ and ′ ₂ (corresponding to the wheel deflection angles α and β), and whose level changes according to the steering angles ′ 1 and ′ 2 (corresponding to the wheel deflection angles α and β). The drive control circuit uses a well-known servo control method to compare the steering command angles ₁ and ₂ with the steering angles ' ₁ and ' ₂ which are the outputs of the sensor 9, and a power amplification part in which a taxi energy feedback is added to amplify the power of the error signal. Consists of. As a result, when the driver operates the steering wheel 11, the steering command signal generator 13 sends a steering command signal a, which is a direct current with a polarity corresponding to the rotational position from the reference position and a level corresponding to the rotation amount, to an electric wire or optical fiber. to each motor drive control circuit. When the steering mode selector switch S1 is set to mode 1, one or _two steering command signals a are sent to the front wheel drive control circuits 30, 30' based on whether the wheels are inner wheels or outer wheels by the operation of the switching circuit _S2 . Supplied.
As a result, the steering command angles ₁ , ₂ and the steering angles ′ ₁ , ′ ₂
Since there is no tachodynamic feedback at first, a large drive input is supplied to the DC servo motors of the front wheel steering actuators 1, 1', and the associated steering mechanical systems 2, 3 and 2', 3' is
Respond quickly to follow ₁ and ₂ . At this time, the steering command signal a is also supplied to the reaction force drive control 20 at the same time, and the DC motor 14 is driven with a drive input corresponding to ± ₁ v ² , giving the corresponding torque to the steering wheel 11 and preventing excessive steering. be done. During this time, the drive control circuit 3 is switched on by the switching circuit S3.
The inputs at 1 and 31' are zero, and the rear wheels are locked at the reference position.

When the switch S1 is set to mode 2, the switching circuit S3 is activated, and the rear wheel control drive circuit 31, 31'
A steering command signal a is also supplied to the rear wheels, causing the rear wheels to swing in the opposite direction to the front wheels. When set to mode 3, the switching circuit S4 operates and all drive control circuits 30, 30',
Since a steering command angle signal of ₁ is given to the rear wheel drive control circuits 31 and 31' and the polarity is reversed, the deflection direction of the rear wheels is the same as that of the front wheels. The deflection angles of all wheels are the same.

FIG. 5 shows another embodiment of the present invention, in which the steering command signal generator 13 is connected to the steering wheel 1.
In order to identify the direction of rotation of the rotary encoder 1, a rotary encoder is used that generates a pulse for each unit rotation amount using 2 bits.
1', which utilizes a particularly high-speed microcomputer. That is, 35 is a reversible counter that reversibly counts one of the 2-bit steering command signal a and holds the steering command angle ₁ ; 36 is a 1-bit clock;
This is a flip-flop that uses the other 1 bit as data and discriminates between data 0 and 1 at the rising edge of the clock to identify the direction of rotation of the steering wheel 11. The microcomputer 37 periodically reads the contents of the reversible counter 35 and sets the steering command angle _{to 1} .
Further, the direction of the steering command relative to the reference position of the steering wheel 11 is determined by looking at the counting direction and the output of the flip-flop 36. Then, by checking the selection mode of switch S1, the correction command angle is determined as described above.
₂ calculation and turning on/off the output signal to the rear wheels.
The front wheel drive units 38, 38' and the rear wheel drive units 39, 3 perform turning off, reversing the polarity of the output signal, determining whether the outer wheel is an inner wheel, etc., and perform steering as shown in FIG.
9'. The microcomputer 37 includes, for example, links 2, 2',
External force load sensors 40, 40', 41, 4 which are strain gauges affixed to 6, 6', respectively
By taking in the external load F detected through the bridge circuit 1' and the number of pulses per unit time of the photoelectric pulse type vehicle speed sensor 21 as the vehicle speed v, more precise steering can be performed. The external load F is the stepping force in response to the centrifugal force when the vehicle turns, and in order to increase the cornering force when turning a corner at high speed, the slip angle of the wheels is increased to improve posture balance. need to take. Therefore, when F increases for the same steering command angles ₁ and ₂ , both become larger apparently, and v
To prevent the wheels from swinging too much when
Make ₁ and ₂ smaller in appearance. Furthermore, the microcomputer 37 inputs the vehicle speed v to another computer.
And the reaction force is ₁ v ² from the count value ₁ of the reversible counter 35.
It is also possible to calculate

As described above, according to the present invention, the steering mechanical system is driven by an electric motor, and the drive is controlled via electric wires or optical fibers from the steering wheel equipped with a reaction force device that applies a reaction force that increases or decreases depending on the steering condition. It becomes possible to realize an electric power steering device that independently operates each wheel without a steering shaft, which is safe and practical in terms of steering wheel operation. The advantages of not having a steering shaft, such as improved assembly work efficiency, improved usability of the engine compartment, and increased freedom in body and interior design, are more effectively demonstrated by the electric type. In addition, even a four-wheel independent steering system can be constructed more easily and inexpensively than a hydraulic system, and the steering mode can be easily switched.

[Brief explanation of the drawing]

Figure 1 shows an example of the basic configuration of the four-wheel independent steering system according to the present invention, Figures 3 to 5 show more specific examples of the configuration, and Figure 2 is an explanatory diagram of the steering mode using the system shown in Figure 1. show. 1, 1', 5, 5'... Steering actuator, 1
0... Steering column, 11... Steering wheel, 12... Gear system, 13... Steering command signal generator, 14... DC motor.

Claims (1)

[Scope of Claim for Utility Model Registration] Each of the front, rear, left, and right wheels is provided with a steering mechanical system that is independently driven by an electric motor, and a steering wheel that is rotatably operated independently of these steering mechanical systems; a steering command signal generator that outputs a steering command direction signal and a steering command angle signal in response to the steering command; and a rotation mechanism rotationally driven by the steering wheel so as to apply a reaction force in a direction opposite to the rotational operation of the steering wheel. With the reaction force actuator attached to the steering direction, steering angle, and vehicle speed signals as input,
reaction force drive control means for driving and controlling the reaction force actuator to generate a reaction force corresponding to the steering angle and vehicle speed; and receiving the output signal of the steering command signal generator and belonging to each of the mechanical steering systems. A steering mode changeover switch that switches the output of at least some of the motor drive control means in response to the same output signal of the steering command signal generator. An automobile steering device characterized by: