JPS62214059A - Automobile steering device - Google Patents

Abstract

PURPOSE:To improve operability, by providing a differential gear unit comprising a sun gear, a planetary gear and an internal gear, making the internal gear an output gear, and controlling a steering angle ratio by a motor for rotating a support member of the planetary gear. CONSTITUTION:A control circuit 11 determines an optimum steering angle ratio based on signals from an input angle sensor 7 and a traveling mode sensor 9 for rotating a motor 5. The motor 5 drives to cause a differential gear box 34 to rotate, then a ratio of a rotating angle of an input shaft 21 to a rotating angle of an output shaft 22 is controlled accordingly for obtaining an optimum steering angle ratio. Therefore, a steering angle ratio can be variably controlled to an optimum value at all times by changing a rotating direction and a rotating angle of the motor 5 with respect to a rotating direction and a rotating angle of a steering wheel 1 in accordance with a change in a traveling mode, whereby operability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a steering device for a motor vehicle.

2. Description of the Related Art In general, steering devices for automobiles use a gear device to convert the rotational operation of the steering wheel into an axial displacement of a shaft proportional to the rotation angle of the steering wheel. Wheel)
In the past, devices in which the steering operation is performed have been widely used (see, for example, Japanese Utility Model Application Publication No. 57-55671, Japanese Utility Model Application Publication No. 57-74876, etc.).

In addition, in a steering device having a gear device as described above, by devising the tooth profile of the gear, for example, the gear ratio is reduced in a small range of the steering wheel rotation angle, that is, near the straight-ahead state, and the gear ratio is reduced when the steering wheel rotation angle is large. Various so-called barrier pull gear ratio steering devices have been developed in the past, in which the ratio of the steering wheel rotation angle to the actual steered wheel angle is non-linear, such as by increasing the angle of rotation of the steering wheel.
It is disclosed in the specification of No. 3 or Japanese Utility Model Application Publication No. 59-16269.

Problems to be Solved by the Invention As mentioned above, the conventional device in which the ratio of the steering wheel rotation angle to the actual steered wheel angle, that is, the steering angle ratio, is in a proportional relationship, and the conventional device in which the nonlinear characteristic is used, are both gear devices. Steering output can only be obtained at an angle uniquely determined by the design.

Generally, one of the biggest factors that determines the steering stability of a car is the steering angle ratio (steering wheel rotation angle/actual steering angle of the steering wheel), and the preferred steering angle ratio varies depending on the driving mode such as vehicle speed and road surface conditions. Therefore, in a steering system in which the steering angle ratio is uniquely determined by the design of the gear system, whether it is a proportional characteristic as in the past or a nonlinear characteristic, the optimal In consideration of the steering angle ratio, it is inevitable to design a compromise by selecting an appropriate steering angle ratio.

The main object of the present invention is to provide a device that can finely control the steering angle ratio depending on the driving mode such as vehicle speed.

Means for Solving the Problems The present invention provides a steering system for an automobile in which steering wheels are steered through a gear device of a steering gear box by rotational operation of the steering wheel. A differential gear device consisting of a sun gear or a gear equivalent to it, a planetary gear or a gear equivalent to it, and an internal gear or a gear equivalent to it is interposed in the middle of the steering system leading to the gear device of the steering gear box, and the sun gear or an equivalent gear as an input gear rotated by the steering wheel,
An internal gear or an equivalent gear is used as an output gear to rotate the gear device of the steering gear box, and an electric motor is used to rotate a support member that supports the rotating shaft of the planetary gear or an equivalent gear, and the input gear is rotated. By changing the ratio of the rotation angle of the support member rotated by the electric motor to the angle, the rotation angle ratio between the input gear and the output gear is changed, and the steering angle ratio between the steering wheel rotation angle and the actual steered wheel angle is determined. and a driving mode in which the input angle signal of the input angle sensor that detects the rotation angle of the input gear and generates the input angle signal and the driving mode such as vehicle speed are detected and generates the driving mode signal. The present invention is characterized in that a control circuit is provided which determines the optimum steering angle ratio for the current driving mode from the driving mode signal of the sensor and generates an output corresponding to the optimum steering angle ratio to rotationally drive the electric motor.

As described above, as the driving mode changes due to vehicle speed, road surface conditions, etc., the control circuit rotates the electric motor by determining the optimum steering angle ratio based on the steering angle ratio characteristics for the driving mode, since the settings are stored in advance. output, and controls the rotation angle ratio of the internal gear or its equivalent gear to the rotation angle of the sun gear or its equivalent gear rotated by the steering wheel, thereby adjusting the steering angle ratio to the above-mentioned optimum steering angle ratio. It is to match.

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

In the figure, 1 is a steering wheel, 2 is a steering shaft, 4 is a steering gear box,
A pinion gear is rotatably supported within the steering gear box 4, and a rack shaft that meshes with the pinion gear is supported so as to be movable in the axial direction. is configured to move in the axial direction and steer the steering wheel via tie rods, knuckle arms, etc., and the gear device installed in the steering gear box 4 and the steering wheel from the gear device Since the steering mechanism and the like leading up to this point are the same as those commonly used in conventional steering devices for automobiles, detailed illustrations and explanations will be omitted.

The steering shaft 2 is divided into an input shaft 21 connected to the steering wheel 1 and an output shaft 22 connected to the pinion gear supported within the steering gear box 4. The input shaft 21 rotates using a bevel gear system. Output shaft 2 via differential gearing 3
2.

The bevel gear type differential gear device 3 includes a pair of front and rear large differential gears 31 and 32 made of bevel gears, and a small differential gear 33 made of bevel gears that straddles and meshes with the large differential gears 31 and 32. is assembled into the differential gear box 34, and the rotating shaft 3 of the differential pinion 33 is assembled into the differential gear box 34.
3a is supported by the differential gear box 34,
The input shaft 21 is connected to one large differential gear 31, the other large differential gear 32 is connected to the output shaft 22, and the differential gear box 34 supporting the rotating shaft 33a of the differential small gear 33 is The rotation of the electric motor 5 causes the worm gear 6a,
It is configured to be rotated via a speed reduction mechanism 6 consisting of a worm wheel 6b or the like.

7 is an input angle sensor that detects the rotation angle of the steering wheel l and emits an input angle signal according to the rotation angle; 8 is an output angle sensor that detects the rotation angle of the output shaft 22 and emits an output angle signal according to the rotation angle; 9 is a driving mode This is a driving mode sensor that detects the vehicle speed and issues a driving mode signal.As the driving mode sensor 9, only a vehicle speed sensor that detects the vehicle speed and issues a vehicle speed signal corresponding to the vehicle speed is used, or the vehicle speed sensor is connected to a throttle valve opening, etc. A combination of part or all of an engine load sensor that detects engine load, a road condition sensor that detects road conditions such as whether the road is good or slippery, and issues a signal is used. .

10 is a differential gear box 34 rotated by the electric motor 5
This is an intermediate angle sensor that detects the rotation angle of the motor and generates an intermediate angle signal corresponding to the rotation angle.

11 is a control circuit, and the control circuit ti calculates the rotation angle at which the differential gear box 34 should be rotated based on the input angle signal of the input angle sensor 7 and the drive mode signal of the drive mode sensor 9. It generates the output that should drive the electric motor 5 to rotate. The rotation of the electric motor 5 is determined by the output angle signal of the output angle sensor 8 and the intermediate angle sensor 1.
Feedback control is performed by an intermediate angle signal of 0.

In the above, when the steering wheel 1, that is, the input shaft 21 is rotated by an angle of 01 degrees, and the differential gear box 34 is rotated by an angle of φ through the reduction mechanism 6 due to the rotational drive of the electric motor 5, the differential gear box 32, that is, the output shaft 22 is rotated by an angle of φ. Suppose that the rotation angle θ2 of the output shaft 22 is expressed by the following equation since φ=+(01+02).

θ2 =-(θ1-2φ) ・・・・・・・・・・・・
(1) From this equation (1), if the electric motor 5 does not rotate and the differential gear box 34 is fixed, φ=O, so θ2−−
01, and the output shaft 22 rotates in the opposite direction by the same rotation angle relative to the rotation angle of the input shaft 21. In this case, even if the output shaft 22 rotates in the opposite direction with respect to the input shaft 21, the combination structure of the gear device in the steering gear box 4, or whether the knuckle arm is installed forward or backward with respect to the rotation axis of the steering wheel, etc. The steering direction of the steering wheel can be easily matched with the rotational direction of the steering wheel l, that is, the input shaft 21, by conventionally known measures, and the gear device in the steering gear box 4 has a proportional characteristic. From, the rotation angle θ1 of the input shaft 21 and the rotation angle 0 of the output shaft 22
The ratio between the steering wheel rotation angle and the actual steered wheel angle (steering wheel rotation angle/actual steered wheel angle) is variably controlled by changing the absolute value 1θ1/θ21 of the rotation angle ratio with respect to . Therefore, as mentioned above, the differential gear box 3
If 4 is fixed, output shaft 21 to input shaft 2
The rotational angle transmission ratio to 2 is Iθ1/θ21=1.

When the electric motor 5 rotates the differential gear box 34 in the same direction as the rotation direction of the steering wheel 1, that is, the input shaft 21, that is, when φ>O, from the above equation (1), 1θ21 x 1θl 1 becomes 1θ1/ θ21〉1, the steering angle ratio becomes large, and conversely, the differential gear box 3
When 4 is rotated in the opposite direction to the direction of rotation of the steering wheel, that is, when φ is 0, 1θ21>1θl 1 becomes lθ1/θ21×l, and the steering angle ratio becomes small. Therefore, by changing the rotation direction and rotation angle of the electric motor 5 with respect to the rotation direction and rotation angle of the steering wheel 1 according to changes in the driving mode, such as the vehicle speed, the steering angle ratio can always be optimized to correspond to the driving mode. The value can be variably controlled.

The control circuit 11 is configured to increase the steering angle ratio to suppress rudder effectiveness when driving at extremely low speeds, and to reduce the steering angle ratio to improve rudder effectiveness and perform agile steering at low to medium speeds. Differential gears should be adjusted to the steering wheel rotation angle θl to obtain the optimum steering angle ratio depending on the vehicle speed, such as using a slightly thicker steering angle ratio since excessive steering is dangerous when driving at high speeds. The ratio of the rotation angle φ (φ/θ1) of the box 34 can be set and memorized, or in addition to the above, the steering angle ratio can be adjusted depending on the road surface condition, such as increasing the steering angle ratio since agile steering is dangerous on slippery roads. The optimum steering angle ratio φ/θ1 to obtain the optimum steering angle ratio is set and stored, and the optimal steering angle ratio is determined based on the input angle signal of the input angle sensor 7 and the driving mode signal of the driving mode sensor 9 based on the various data set and stored above. Since the value of φ to obtain the steering angle ratio is determined and an output is generated to rotate the electric motor 5, the steering angle ratio is always finely and automatically controlled to the optimum value adapted to the driving mode.

As described above, an operation section is provided that allows the rate of change of φ/θ1 stored in the control circuit 11 to be manually changed, so that the control mode of the steering angle ratio for the driving mode can be adjusted according to the driver's preference. It is desirable to keep it as such.

In the illustrated embodiment, a differential gear device 3 is used in which a pair of front and rear differential gears 31 and 32 have the same diameter. It is also possible to use a differential gear device consisting of bevel gears with different diameters, and it is not limited to bevel gear type differential devices. A planetary gear type differential gear device including an internal gear having meshing internal teeth may also be used. In this case, one large differential gear 31 of the bevel gear type differential gear device 3 corresponds to a sun gear of a planetary gear type differential gear device, and the other large differential gear 32 corresponds to an internal gear, Since the gear 32 corresponds to a planetary gear, the input shaft 21 is connected to the sun gear so that the output shaft 22 is rotated by the internal gear, and a planetary gear arm ( By configuring the drive gear box 34 (corresponding to the illustrated operating gear box 34) to be rotated at a reduced speed by the electric motor 5, the same function as in the illustrated embodiment can be achieved. The rotation control mechanism of the electric motor 5 is the same as in the illustrated embodiment when a bevel gear type differential gear with different diameters of the front and rear differential gears is used, or when a planetary gear type differential gear is used. Needless to say, in these cases, the gear coupled to the input shaft 21 and the output shaft 2
Since the diameters of the gears connected to 2 and 2 are different from each other, when the electric motor 5 does not rotate, the output angle θ2 with respect to the input angle θ1
The angular ratio is not l=1 as in the illustrated embodiment, but the above angular ratio is determined by the ratio of the diameters of the input side gear and the output side gear. Therefore, the optimum steering angle for each driving mode is determined. Of course, the rotation angle of the electric motor 5 for obtaining the ratio is different from that of the illustrated embodiment.

Effects of the Invention As described above, according to the present invention, for example, the steering angle ratio that provides optimal steering stability at high speeds is set as a standard, and while agile handling is required, the steering angle ratio is reduced at low speeds, and the steering angle ratio is reduced at extremely low speeds. The steering angle ratio can be finely and automatically adjusted in response to changes in driving mode such as vehicle speed, such as by increasing the steering angle ratio to provide a light steering force at times. Even if the electric motor fails and stops working, the differential gear system has a fail-safe function that transmits the rotation of the input shaft to the output shaft at a predetermined rotation angle ratio, allowing sufficient maneuverability. It is possible to improve safety, and together with the fact that the structure as a whole is simple and the cost is relatively low, it can bring about great practical effects.

[Brief explanation of drawings]

The accompanying drawing is a vertical sectional side view of a main part showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Steering wheel, 2... Steering shaft, 21... Input shaft, 22... Output shaft, 3... Differential gear device, 4... Steering gear box, 5... Electric Motor, 6... Reduction mechanism, 7... Input angle sensor, 8... Output angle sensor, 9...
... Traveling mode sensor, 10... Intermediate angle sensor, ii
...Control circuit. that's all

Claims (2)

[Claims] (1) In an automobile steering system in which the steering wheels are steered via the gear system of the steering gear box by the rotational operation of the steering wheel, from the steering wheel to the gear system of the steering gear box. A differential gear device consisting of a sun gear or a gear equivalent to it, a planetary gear or a gear equivalent to it, and an internal gear or a gear equivalent to it is interposed in the middle of the steering system, and the sun gear or a gear equivalent to it is connected to the steering wheel. The input gear is rotated by an internal gear or an equivalent gear, the output gear is an output gear that rotates the gear device of the steering gear box, and the support member that supports the rotating shaft of the planetary gear or an equivalent gear is an electric motor. By changing the ratio of the rotation angle of the support member rotated by the electric motor to the rotation angle of the input gear, the rotation angle ratio between the input gear and the output gear is changed, thereby changing the steering wheel rotation angle and steering. The steering angle ratio with the actual steering angle of the wheels can be variably controlled, and the input angle signal of the input angle sensor that detects the rotation angle of the input gear and generates the input angle signal and the driving mode such as the vehicle speed are controlled. A control circuit is provided which calculates the optimum steering angle ratio for the current driving mode from the driving mode signal of the driving mode sensor which detects the driving mode signal and generates the driving mode signal, and generates an output corresponding to the optimum steering angle ratio to rotationally drive the electric motor. Characteristic automobile steering device. (2), the differential gear device is a bevel gear type differential gear device,
The gears corresponding to the sun gear and the internal gear are front and rear large differential gears each made of a bevel gear, and the gear corresponding to the planetary gear is a small differential gear that meshes with the front and rear large differential gears. Claim 1, wherein the supporting member is a differential gear box that houses the front and rear differential large gears and differential small gears and supports the rotating shaft of the differential small gears. A steering device for an automobile as described in paragraph.