JPH0438622B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a steering device for an automobile that changes the transmission ratio of the steering angle to the wheels depending on the vehicle speed and the steering angle.

(Prior Art) An automobile steering device converts the rotation of a steering wheel into a lateral displacement of a tie rod via a steering gear device such as a rack and pinion.
The direction of the left and right wheels connected to both ends of the tie rod is changed, but in this case, the amount of rotation of the steering wheel (handle steering angle) and the turning angle of the wheels (wheel steering angle) always have a constant correspondence. It is usually held in a relationship. However, for example, when driving at high speeds, it is desirable to increase the reduction ratio from the above-mentioned steering wheel steering angle to the wheel steering angle to reduce the wheel steering angle for a constant steering wheel steering angle in order to ensure driving stability, and when driving at low speeds, it is desirable to It is desirable to reduce the reduction ratio and increase the wheel steering angle with respect to a constant steering wheel steering angle in order to make the behavior of the automobile more agile and obtain a good driving feeling, and to make it easier to park the vehicle in a garage. This also applies to the size of the steering wheel angle; the smaller the steering wheel angle is (generally at high vehicle speeds), the larger the reduction ratio is, and the smaller the wheel steering angle is for a constant steering wheel angle. As the steering wheel angle increases (generally at low vehicle speeds), it is desirable to decrease the reduction ratio and increase the wheel steering angle with respect to a constant steering wheel angle.

Therefore, as disclosed in, for example, Japanese Unexamined Patent Publication No. 58-224852, a speed-sensitive steering device has been proposed in which the ratio of the wheel steering angle to the steering wheel steering angle is changed depending on the vehicle speed. As shown in Fig. 6, a transmission mechanism F consisting of a pair of variable pitch pulleys C and D and a V-belt E wound between both pulleys is interposed between the handle A and the steering column B. In addition, the pitch diameter of the driven pulley D is controlled by the stepping motor G so that it becomes larger as the vehicle speed increases. According to this, handle A
The reduction ratio of the transmission of rotation from the motor to the steering column B becomes larger at higher speeds, and as a result, the steering angle of the wheels for a given steering angle becomes smaller at high speeds and larger at low speeds, resulting in good steering characteristics that correspond to the vehicle speed. will be obtained. However, if the reduction ratio of the wheel steering angle to the steering wheel angle is changed according to the vehicle speed as described above, even if the steering wheel angle is constant during a turn, the wheel steering angle will change due to changes in vehicle speed. Especially when making a sharp turn with a large steering wheel angle, if the wheel steering angle changes greatly due to a change in vehicle speed, driving stability will deteriorate significantly.

(Object of the Invention) The present invention addresses the above-mentioned problems related to automobile steering devices, and aims to change the reduction ratio of rotational transmission in the steering force transmission path from the steering wheel to the wheels according to the vehicle speed and the steering angle. In addition, by appropriately setting the rate of change of the reduction ratio with respect to the vehicle speed in that case according to the size of the steering wheel steering angle, the amount of change in the wheel steering angle due to changes in vehicle speed can be reduced, especially during sharp turns where the steering wheel steering angle is large. The purpose is to improve the running stability of the vehicle during such sharp turns by making the diameter smaller.

(Structure of the Invention) That is, the steering device for an automobile according to the present invention is provided with a transmission ratio variable mechanism that changes the reduction ratio of the wheel steering angle to the steering wheel steering angle in the steering force transmission path between the steering wheel and the tie rod. In addition, a vehicle speed detection means for detecting the vehicle speed, a steering wheel angle detection means for detecting the steering angle of the steering wheel, a controller that receives signals from these detection means and outputs a control signal, and control from the controller. and an actuator that receives a signal and controls the variable transmission ratio mechanism. Then, the controller changes the reduction ratio of the wheel steering angle to the steering wheel steering angle so that it increases as the vehicle speed increases and decreases as the steering wheel angle increases, and also changes the reduction ratio in that case. The variable transmission ratio mechanism is configured to be operated via the actuator so that the rate of change with respect to vehicle speed becomes smaller as the steering angle becomes larger.

(Effects of the Invention) According to the steering device configured as described above, when driving at high speed or when the steering wheel angle is small, the reduction ratio of the wheel steering angle to the steering wheel steering angle is increased to obtain good running stability. When driving at low speeds or when the steering wheel angle is large, the reduction ratio is reduced to obtain agility and the wheel turning angle is reduced for a constant steering angle. Good steering characteristics can be obtained depending on vehicle speed and steering angle, such as by increasing the steering angle. In particular, since the rate of change of the reduction ratio with respect to the vehicle speed becomes smaller as the steering wheel steering angle increases, when the steering wheel steering angle is large, the amount of change in the wheel steering angle due to a change in vehicle speed becomes small, and as a result, The driving stability of the vehicle, especially when making sharp turns, will be improved.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

1 to 3 show a variable transmission ratio mechanism that is provided in the steering force transmission path and changes the reduction ratio of the wheel steering angle to the steering wheel steering angle, and the mechanism 1 is a steering wheel (hereinafter referred to as a steering wheel). 2
a handle shaft 3 with one end fixed to the center of the handle shaft 3; an input shaft 6 disposed parallel to the handle shaft 3 and with a pair of input gears 4, 5 interposed between the shaft 3;
Output shaft 7 arranged on the same line as this input shaft 6
and a planetary gear type differential gear mechanism 8 provided between the input shaft 6 and the output shaft 7. The output shaft 7 is connected to a steering gear device (not shown), and further connected to left and right wheels via a link mechanism such as a tie rod.

The differential gear mechanism 8 includes a sun gear 9 fixed to the input shaft 6, a ring gear 10 fixed to the output shaft 7, and a plurality of gears arranged at equal angular intervals between the two gears 9 and 10 (in the illustrated example). 3) planetary pinions 11...11 are rotatably fitted onto the input shaft 6 to connect the pinions 11...11 to the pinion shaft 1, respectively.
2... Pinion carrier 13 supported via 12
It is made up of. A sector gear 14 is integrally provided on the carrier 13, and a pinion 16 fixed to the rotating shaft of a stepping motor 15 is meshed with the sector gear 14.

On the other hand, this steering device is equipped with a controller 17 that controls the rotation of the stepping motor 15. This controller 17
inputs the vehicle speed signal a from the vehicle speed sensor 18 and the steering angle signal b from the steering angle sensor 19 that detects the steering angle of the steering wheel 2, and controls the stepping motor 15 based on these signals a and b. The amount of rotation (including the direction of rotation) is set, and this is sent to the stepping motor 1 as a control signal c when steering the steering wheel 2.
It is designed to output to 5.

According to the above configuration, when the steering wheel 2 is rotated while the automobile is running, the rotation is transmitted from the steering wheel shaft 3 to the input shaft 6 via the pair of input gears 4 and 5.
and the sun gear 9 in the differential gear mechanism 8
Rotate. At this time, a control signal c is outputted to the stepping motor 15 from the controller 17 into which signals a and b from the vehicle speed sensor 18 and steering angle sensor 19 are input, and the vehicle speed and steering angle indicated by the signals a and b are adjusted. Accordingly, the motor 15 is rotated, and in conjunction with this, the pinion carrier 13 in the differential gear mechanism 8 is rotated via the pinion 16 and sector gear 14. Therefore,
In the differential gear mechanism 8, the sun gear 9 is rotated by an amount proportional to the amount of steering of the steering wheel 2, and at the same time, the pinion carrier 13 is rotated according to the amount of rotation of the stepping motor 15.
Therefore, the ring gear 10 in the differential gear mechanism 8
The output shaft 7 is rotated by an amount proportional to the amount of steering of the handle 2, which is increased or decreased depending on the amount of rotation of the pinion carrier 13. Then, depending on the amount of rotation of the output shaft 7, the wheels are steered via a steering gear device. As a result, the reduction ratio of the wheel steering angle to the steering wheel steering angle is changed in accordance with the amount of rotation of the stepping motor 15.

However, the amount of rotation of the stepping motor 15 is set so that the reduction ratio changes with the characteristics shown in FIG. 4 with respect to the vehicle speed and steering angle. In other words, the reduction ratio increases as the vehicle speed increases and decreases as the steering angle increases.As is clear from comparing curves () and (), the reduction ratio with respect to the vehicle speed changes. The rate of change decreases as the steering angle increases. Therefore, the higher the vehicle speed or the smaller the steering wheel angle, the smaller the wheel steering angle with respect to a constant steering angle, resulting in better running stability.The lower the vehicle speed or the larger the steering angle, the smaller the wheel steering angle. As the size increases, the behavior of the car will become more agile. In particular, since the rate of change of the reduction ratio with respect to vehicle speed decreases as the steering angle increases, the amount of change in wheel steering angle due to a change in vehicle speed when turning at a constant steering angle increases as the steering angle increases. case is smaller. This eliminates the problem of the wheel steering angle changing greatly with changes in vehicle speed, which deteriorates stability, especially when making a sharp turn with a large steering wheel angle.

Here, the characteristics of the reduction ratio with respect to the vehicle speed and steering angle may vary linearly as shown in FIG. 5, but as shown in the characteristics shown in FIG.
In particular, if the rate of change of the reduction ratio with respect to vehicle speed is made smaller in the high vehicle speed range indicated by the symbol x than in the low vehicle speed region indicated by the symbol y, the following advantages can be obtained. In other words, if the wheel steering angle changes due to a change in vehicle speed during a turn, the vehicle body will behave more greatly at higher speeds, but if the rate of change in the reduction ratio relative to the vehicle speed is reduced in the high speed range, the wheel steering angle will change due to changes in vehicle speed. The amount of change in the steering angle also decreases,
The behavior of the vehicle body becomes approximately the same as at low vehicle speeds, which improves ride comfort and driving operability when turning.

Incidentally, the characteristics of the reduction ratio with respect to the vehicle speed and steering angle as shown in FIG. 4 are, for example, the characteristics expressed by the following equation.

R=αV ⁿ +β−γθ ^m Here, R: Reduction ratio, V: Vehicle speed, θ: Steering wheel angle, α, β, γ: Positive constants, 0<n<1, and m=aV ^K +b>0(a,b,k,>0)
It is.

[Brief explanation of drawings]

1 to 5 show embodiments of the present invention, in which FIG. 1 is a cross-sectional plan view showing the configuration of the main parts of the steering device and the accompanying control circuit, and FIGS. 2 and 3 are respectively similar to FIG. 1. A sectional view taken along the - line and the - line, FIG. 4 is one control characteristic diagram, and FIG. 5 is another control characteristic diagram. Moreover, FIG. 6 is a schematic configuration diagram showing a conventional example. DESCRIPTION OF SYMBOLS 1... Variable transmission ratio mechanism, 2... Steering handle, 15... Actuator (stepping motor), 17... Controller, 18... Vehicle speed detection means (vehicle speed sensor), 19... Handle steering angle detection means (steering angle sensor).

Claims (1)

[Claims] 1. A variable transmission ratio mechanism that is provided in the steering force transmission path between the steering handle and the tie rod and changes the reduction ratio of the wheel steering angle to the steering wheel steering angle, a vehicle speed detection means that detects the vehicle speed, and a vehicle speed detection means that detects the vehicle speed; A steering wheel angle detection means for detecting a steering angle, a controller for inputting signals from these detection means and outputting a control signal, and an actuator for operating the variable transmission ratio mechanism in response to an output signal from the controller. and the controller changes the reduction ratio so that it increases as the vehicle speed increases and decreases as the steering angle increases, and changes the rate of change of the reduction ratio with respect to the vehicle speed according to the steering angle. A steering device for an automobile, characterized in that the control signal is outputted in such a manner that the control signal decreases as the value increases.