JPS6192964A - Steering device for car - Google Patents

Abstract

PURPOSE:To improve the steering stability when shifted to the reverse side by providing a control section correcting so that the ratio of the wheel turning angle against the steering angle of a steering wheel is increased during a reverse operation of a car than during an advance operation. CONSTITUTION:The said steering device calculates the turning angle of a turning wheel 17 based on the input signal from a steering angle detection sensor 5 and the input signal from a car speed sensor 8 in a control section 7 when a steering wheel is steered. This turning angle is compared with the actual turned angle from a turned angle sensor 6, then the opened/closed conditions of a solenoid servo valve 24 are duty-controlled in response to the turning angle deviation to control the operation of a power cylinder 18. In this case, when a reverse condition is detected by a shift position detection sensor 9, the control signal fed to the valve 24 is multiplied by K (K<1) via a gear ratio changing means 30, and the flow quantity of the pressure oil fed from an hydraulic source 19 to the power cylinder 18 is controlled to be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a steering system for a vehicle, and relates to an improvement in a steering system that is provided with a mechanism capable of adjusting the ratio of the wheel steering angle to the steering angle of the steering wheel.

BACKGROUND ART Traditionally, vehicle steering systems have mechanically connected an input shaft connected to a steering wheel and a steering control mechanism, and the steering wheels are directly steered by operating the steering wheel. In addition to this method, the input shaft and the steering control mechanism are mechanically separated, and an actuator for driving this steering control mechanism and a controller for controlling the operating state of this rotary unit are provided (hereinafter referred to as A steering control system (referred to as a steering wire device) is known. Among these, examples of steering devices have been proposed that have the function of maintaining an appropriate steering feel by varying the ratio of the wheel steering angle to the steering wheel steering angle depending on the vehicle running condition. Jitsukai 59-24
Publication No. 665 "Control device for hydraulic steering system" discloses an example of the device arranged below. That is, the target heavy wheel steering angle is calculated based on the signals from the angular displacement detector of the steering wheel and the vehicle speedometer, and the control signal obtained as a result is sent to the control valve of the hydraulic steering system to operate the hydraulic piston. The actual steering angle is calculated based on the piston displacement signal from the hydraulic piston displacement detector, and the result and the target wheel 9
An example of a control device for a hydraulic control system is not shown, which includes a control unit that corrects the control signal by comparing the 19 angles. According to the above device M, the target wheel angle is first calculated according to the vehicle speed and the amount of displacement of the steering wheel, and the actual steering angle is calculated by detecting the displacement of the piston of the hydraulic steering system. The optimum wheel steering angle can be determined by comparison with the target wheel steering angle.

Problems to be Solved by the Invention However, the means for determining the wheel steering angle in such conventional steer-by-wire devices is a control system that mainly determines the actual steering angle from the vehicle speed and the angular displacement of the steering wheel. Therefore, the ratio r of the steering wheel steering angle to the title wheel steering angle (=steering wheel steering angle/wheel steering angle, hereinafter abbreviated as gear ratio for convenience) during driving is the same regardless of whether the vehicle is moving forward or backward. ,
Since they are set in the same way, there is a problem in that the gear ratio becomes a predetermined small value, making it difficult for the driver to get a feel for the vehicle, especially when the vehicle is running backwards at a low speed.

That is, generally speaking, when the vehicle is running at high speed, the gear ratio is increased to improve running stability, while when the vehicle is running at low speed, the gear ratio is decreased to increase the steering gain and increase the steering effect. This is desirable. Furthermore, when comparing the cases when the vehicle is moving forward and when the vehicle is moving backward, if the vehicle speed is the same, by making the gear ratio larger when moving backward than when moving forward, the gain is slightly lower when moving backward; It is desirable to increase the ease of steering. However, in the conventional example described above, the wheel steering angle is determined based on factors such as the steering angle of the steering wheel and the vehicle speed, and it is not possible to determine whether the vehicle is traveling forward or backward. Since these considerations have not been taken into account, the gain is the same when moving forward and when moving backward, which poses a problem particularly in terms of steering safety when moving backward.

An object of the present invention is to eliminate the problems of the conventional steer-by-wire type steering device as described above, and to improve steering safety mainly when traveling in reverse.

Means for Solving the Problems In order to achieve the above object, the present invention includes a steering angle detection sensor that detects the steering angle of a steering wheel, a vehicle speed sensor that detects vehicle speed, and the steering angle detection sensor. a control circuit that calculates a target turning angle of a steering single wheel based on a steering angle signal from a vehicle speed sensor and a vehicle speed signal from a vehicle speed sensor, and generates a target turning angle signal; In a vehicle steering system having a drive means for steering wheels, a shift position detection sensor is provided to detect whether the vehicle is moving forward or backward, and based on a shift position signal from the shift position Ik detection sensor, a shift position signal from the shift position Ik detection sensor is used. The present invention provides a steering system for a vehicle comprising a steering gear ratio changing means for setting the target steering angle smaller than the actual steering angle.

Function: The vehicle steering device according to the present invention having such a configuration has the following features:
A target steering angle of the single steered wheel is calculated based on input signals of a steering angle detection sensor and a vehicle speed sensor, and the steered single wheel is controlled by a drive means to reach the target value,
Based on the forward or reverse traveling state of the vehicle detected by the shift position detection sensor, the gear ratio is made larger when traveling backward at the same vehicle speed than when traveling forward, thereby providing an effect that improves the steering feel.

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

FIG. 1 shows an example in which the present invention is applied to a steer-by-wire system of a hydraulic steering system. In the figure, 1 is a steering wheel, 2 is an input shaft connected to the steering wheel 1, 3 is an output shaft connected to a wheel steering control mechanism, and a clutch is located between the human power shaft 2 and the output shaft 3. Means 4 are inserted.

5 is a steering angle detection sensor that detects the rotational state of the input shaft 2;
6 is the output shaft 3. That is, it is a steering angle detection sensor that detects the steering angle of a single steered wheel, and each detection signal is input to the control 117. The control section 7 (control circuit) receives production signals from a vehicle speed sensor +8 and a shift position detection sensor +9 for gear change, respectively. 1o indicates a total of 1,000 units for connecting and disconnecting the means 4 between /) and y. Output shaft 3 is a universal joint 11.12
The rack 14 is connected to the pinion 13 via the linkage 15 to move the rack 14, and the knuckle arm 16 interlocked with the linkage 15 is operated to control the steering state of the steering wheel 17. 18 is a power cylinder (driving means), which supplies and discharges pressure oil into oil chambers jsa and tsb formed in the power cylinder 18,
Said linkage 15. Steering control of the steering wheel 17 is performed based on the operation of the knuckle arm 16.

On the other hand, reference numeral 19 indicates a hydraulic source as actuator driving means, and a hydraulic pump 21 operated by the action of a motor 20.
% It has a relief valve 22 and a tank 23. 2
Reference numeral 4 indicates an electromagnetic servo valve, which controls the flow rate of pressure oil from the hydraulic cylinder 19 to the power cylinder 8. Eventually, as an input signal to the control unit 7, the vehicle speed sensor 8 and the shift position 1te are input.
t output +9. Steering angle detection sensor 5% Steering angle detection sensor +
There are various output signals from 6, and the control unit 7 controls the operating state of the magnetic valve 24 and the rotor valve 10 based on the above input signals.

The operation of the vehicle steering system having the above configuration is as follows. Normally, the clutch means 4 is "disengaged".

The pressure oil generated by the hydraulic pressure +11ij19 is passed through the electromagnetic servo valve 24 to the oil chambers 18a and I8b of the power tank 18.
The steering wheel 17 is in a state where the steering wheel 17 is controlled by flowing into or out of the steering wheel 17. Now, assume that the driver is steering the steering wheel 1. Then, the steering angle detection sensor 4-5
A signal proportional to the rotation angle of the input shaft 2 is generated and input to the control section 7. The control section 7 controls the steering angle detection sensor 5.
The angle e of the steered wheels 17 is calculated based on the input signal from the vehicle speed sensor 8 that detects the vehicle speed at that time, and the steering angle detection sensor 6 calculates the angle e of the steered wheels 17. emit a control signal that corrects the steering angle of the steering wheel 17 by comparing it with the actual steering angle calculated based on the input signal from;
The opening and closing conditions of the electromagnetic servo valve 24 from the control lines 25 and 261 determine the amount of pressure oil flowing into and out of the knee control power cylinder 18. In this manner, the gear ratio during steering is determined, and this gear ratio is changed as needed based on factors such as the steering angle and vehicle speed, and the optimal gear ratio is always selected to continue steering the vehicle.

When the shift position detection sensor +9 detects that the transmission of the vehicle has shifted seven steps into the reverse state, the gear ratio changing means 30 sends a signal from the control section 7 to the electromagnetic servo valve 24. By multiplying the control signal by a factor of 1 (k<1), the amount of pressure oil flowing from the hydraulic source 19 into the power cylinder 18 is controlled to be reduced. As a result, when the vehicle is moving forward and backward, the steering angle of the steering wheel (θ) at the same speed is found to be
The ratio of the wheel angle (θT) to the vehicle angle (θT) increases, and the steering characteristics during reverse movement change. In other words, the "sharpness" of the steering wheel when moving backwards at the same speed is slower than when moving forward, and the safety during steering can be increased by that much. In other words, when the vehicle is moving backwards, it is difficult for the driver to get a sense of how the vehicle is moving than when it is moving forward, so it is easier to steer the steering wheel if the steering wheel is not so sharp when moving backwards. It is advantageous. The main focus of the present invention is to improve the ease of steering by intentionally lowering the "sharpness" of the steering wheel when moving backwards than when moving forward at the same speed. .

The clutch means 4 is configured to "close" the clutch means 4 based on the action of the automatic controller 10 when an abnormality occurs in the hydraulic power source or the like for some reason during operation, and to close the electromagnetic servo valve 24. This provides a fail-safe function in which the steering force of the steering wheel 1 is directly transmitted to the steering mechanism of the steering wheel 17 by switching the steering wheel 1 to a free state.

FIG. 2 shows another example of a device using the present invention.
Components that are the same as those shown in FIG. 1 are designated by the same reference numerals. This embodiment is characterized in that an electric motor is used in place of the hydraulic unit of the previous embodiment. In other words, the boo 112 provided midway on the output shaft 3
A toothed belt 31 is hung between a pulley 30 projected from a clutch means 29 attached to an electric motor 28 and a toothed belt 31 to transmit the rotational force of the electric motor 28 to the output shaft 3 side. The control unit 7 determines the steering angle of the steered wheels 17 based on detection signals from the steering angle detection sensors 1-5 and the vehicle speed sensor +8.

The actual steering angle calculated based on the input signal of the steering angle detection sensor +6 and the steering angle of the steering wheel 17 are compared.

While correcting the steering angle of the steering wheels 17, the shift position detection sensor 9 detects the shift position of the transmission. The electric motor 28 is set by the gear ratio changing means 30 so that the ratio of
By controlling the rotational state of , it is possible to obtain an operating state similar to that of the embodiment shown in FIG. According to the embodiment shown in FIG. 2, it is clear that the device of the present invention is applicable not only to hydraulic but also to a stay-by-wire type steering device using an electric actuator.

In both of the embodiments shown in FIGS. 1 and 2, the actual steering angle of the steered wheels is fed back to the control unit, but it is not necessary to feed it back, and open control may also be possible. Needless to say.

FIG. 3 is an example of a characteristic graph obtained by the vehicle steering system according to the present invention. In the figure, the Y axis indicates the ratio of the steering angle θ- of the steering wheel to the wheel steering angle θT, that is, the gear ratio, and the X axis indicates the vehicle speed V. Vehicle speed V from zero to vo
In the normal low speed range, for example θ~20k@/h, and in the range where the vehicle speed is from zero to V(, the gear ratio when going backwards is held constant at a value about 6 higher than the gear ratio when going forwards. The gear ratio increases sequentially when the vehicle speed is 70 or higher, both when moving forward and when reversing, but when comparing cases at the same vehicle speed, the gear ratio when moving backward is always about 6 higher than when moving forward. It is clear that from this characteristic curve,
Regardless of the vehicle speed, the object of the present invention can be achieved by always keeping the gear ratio during reverse travel slightly higher than the gear ratio during forward travel.

What are the values of gear ratios 12 to 14 when moving forward at zero vehicle speed?

This was determined experimentally based on the steering feeling evaluation, and the gear ratio of 18 to 20 when traveling in reverse is the same as the gear ratio of 12 to 20 when traveling forward.
It is set about 6 times higher than 14.

Effects of the Invention As explained in detail above, the present invention has the advantage that when the forward and reverse states of the vehicle are compared at the same speed, the ratio of the wheel steering angle to the steering wheel angle is lower when the vehicle is traveling backward than when it is traveling forward. Since the vehicle is equipped with a control unit that adjusts the speed to increase, when the driver shifts the transmission to reverse, the gear ratio is automatically increased, resulting in the effect of improving steering stability.

Furthermore, regardless of the vehicle speed when traveling forward, the above steering characteristics can be obtained by shifting the transmission to reverse, and the above effects can be obtained regardless of the vehicle speed when traveling backward.

Therefore, the "cutting" of the steering wheel when going backwards is slower than when moving forward, and the /% handling characteristics when going backwards are improved accordingly, making it easier to steer, regardless of the vehicle's driving conditions. ] It has the effect of being able to utilize the most precise gear ratio.

Note that the present invention is not limited to the feedback control based on the actual steering angle detection sensor disclosed in the embodiments, but can also be applied to a steer-by-wire type steering device based on normal open control.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the main parts of a vehicle steering system according to the present invention, and Fig. 2 is a schematic diagram showing another embodiment of the present invention. This is a graph showing. 1... Steering wheel, 2... Input shaft, 3...
... Output shaft, 5... Steering angle detection sensor, 6... Steering angle detection sensor, 7... Control section (control circuit), 8... Vehicle speed sensor, 9... Shift position 11 detection sensor , 17...
・Steering wheel, 18...Bawan cylinder (driving means), 1
9... Hydraulic source, 20... Motor, 21... Hydraulic pump, 24... Electromagnetic servo valve, 28... Electric motor, 311 - Gear ratio f changing means.

Claims (1)

[Claims] (1) A steering angle detection sensor that detects the steering angle of the steering wheel, a vehicle speed sensor that detects the vehicle speed, and a steering angle signal from the steering angle detection sensor and a vehicle speed signal from the vehicle speed sensor. In a vehicle steering system that includes a control circuit that calculates a target steering angle and issues a target steering angle signal, and a drive means that steers steering wheels based on the target steering angle signal, the vehicle is moved forward or backward. A shift position detection sensor for detecting the state is provided, and steering gear ratio changing means is provided for setting the target steering angle to be smaller when traveling in reverse than when traveling forward, based on a shift position signal from the shift position detection sensor. A vehicle steering device characterized by: