JPH0686225B2 - Car steering device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering device capable of changing a transmission ratio (reduction ratio) of a wheel steering angle to a steering wheel steering angle of an automobile.

(Prior Art) Generally, a steering device of an automobile converts a rotational motion of a steering handle into a lateral displacement motion of a tie rod through a steering gear device such as a rack and pinion, and is connected to both ends of the tie rod. Although the direction of the left and right steered wheels is changed, the rotation amount of the steering wheel (steering wheel steering angle) and the steering angle of the wheel (wheel steering angle) are normally held in a fixed correspondence relationship. However, for example, when a vehicle is traveling at high speed, it is desirable to secure traveling stability by increasing the transmission ratio of the wheel steering angle to the steering wheel steering angle to reduce the size of the wheel steering angle with respect to a constant steering wheel steering angle. On the other hand, when driving at low speed, from the viewpoint of speeding up the behavior of the vehicle to obtain a good driving feeling, or facilitating garage entry, the above transmission ratio is reduced to the contrary, and the wheel steering for a constant steering wheel steering angle is reduced. Larger corners are desirable.

Therefore, in order to meet such a demand, conventionally, for example, as disclosed in JP-A-58-224852, the transmission ratio of the wheel steering angle to the steering wheel steering angle is changed according to the vehicle speed of the automobile. Has proposed a speed-sensitive steering device. This is provided with a speed change mechanism composed of a pair of variable pitch pulleys facing each other and a V belt wound between the pulleys between the steering handle and the steering column, and the vehicle speed is controlled by the pitch diameter of the driven pulley. It is controlled by a stepping motor so that it becomes larger as it rises. According to this, the rotation transmission ratio from the steering wheel to the steering column increases as the vehicle speed increases, and as a result, the steering angle of the wheel with respect to a fixed steering angle decreases at high speeds and increases at low speeds. Good steering characteristics can be obtained.

(Problems to be Solved by the Invention) By the way, the transmission ratio variable system for variably controlling the transmission ratio of the wheel steering angle to the steering wheel steering angle of the steering handle according to the vehicle speed or the like is applied to a steering device having a power steering mechanism. In this case, the control characteristic of the transmission ratio is usually set in consideration of the output of the power steering mechanism. However, in that case, if the power steering mechanism is in a failed state due to a failure or the like and its output is stopped, the control characteristics of the transmission ratio set as described above may change, and in order to ensure higher safety. There is room for further improvement.

The present invention has been made in view of the above points, and an object of the present invention is to apply a system for changing a transmission ratio of a wheel steering angle to a steering wheel steering angle to a steering device including a power steering mechanism as described above. In this case, when the power steering mechanism fails, the transmission ratio can be kept constant to improve the safety of the steering device.

(Means for Solving the Problem) In order to achieve the above object, in the solution means of the present invention, a steering handle is mechanically coupled to a wheel through a steering gear device having a power steering mechanism, and a steering handle is provided. A transmission ratio variable means is provided in the steering amount transmission path for transmitting the steering amount to the wheel, and the transmission ratio variable means changes the transmission ratio of the wheel steering angle to the steering wheel steering angle. The transmission ratio varying means is composed of, for example, a planetary gear mechanism or a differential gear mechanism, and an actuator such as a stepping motor that controls the operation of the gear mechanism.

The transmission ratio varying means is controllable so that the transmission ratio becomes a preset target transmission ratio when the power steering mechanism is operating, while the target transmission ratio is controlled when the power steering mechanism is not operating. The control to the ratio is disabled and the change in the transmission ratio is restricted.

(Operation) Therefore, according to the present invention, when the power steering mechanism in the steering gear device is operated, when the steering wheel is steered to steer the wheels, the power steering mechanism operates in accordance with the steering of the steering wheel. Then, the wheels are steered while the steering force is assisted, and the transmission ratio varying means operates to variably control the transmission ratio of the wheel steering angle to the steering wheel steering angle to the target transmission ratio.

Further, the transmission ratio varying means is configured such that when the power steering mechanism is not operated, the control to the target transmission ratio is disabled and the change in the transmission ratio is restricted, so that the power steering mechanism is When the vehicle is in a failed state due to a failure or the like, the operation of the transmission ratio varying means is blocked, the transmission ratio of the wheel steering angle to the steering wheel steering angle is not controlled to the target transmission ratio, and the transmission ratio is kept constant to maintain normal steering. This is similar to the device, which improves the safety in the event of failure of the power steering mechanism.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 1 shows the overall configuration of a steering apparatus for an automobile according to an embodiment of the present invention, in which 1 is a steering wheel, 3 is a rack and pinion type for converting the rotational movement of the steering wheel 1 into the steering movement of wheels 8,8. Steering gear device. The steering gear device 3 has a pinion (not shown) in the steering gear box 3a, and a rack that meshes with the pinion and extends in the vehicle body width direction. The pinion is connected to the handle 1 via the first and second intermediate shafts 4, 5 and the handle shaft 2, while the rack is connected to the wheels 8 via the tie rods 6 and knuckle arms (not shown). It is connected.

The steering device 3 is equipped with a power steering mechanism 7 for assisting the steering force transmitted from the steering wheel 1 to the wheels 8, 8. The power steering mechanism 7 is provided continuously with the hydraulic power cylinder 7a interposed between the rack and one (left side in the figure) tie rod 6 and the steering gear box 3a, and the handle 1
The rotary type control valve 7b is provided for controlling the pressure of the hydraulic oil supplied from the hydraulic pump (not shown) to the power cylinder 7a according to the steering of the hydraulic cylinder 7a. Pressure oil is supplied to the power cylinder 7a while being controlled by the control valve 7b according to the steering input of the steering wheel 1, and the power cylinder
The output to 7a assists the steering force to steer wheels 8 and 8.

Further, a transmission ratio variable means 9 for changing the transmission ratio R to the wheel steering angle θ _W with respect to the steering wheel steering angle θ _H is provided in the middle of the steering amount transmission path between the steering wheel 1 and the steering gear device 3. There is. The transmission ratio varying means 9 is provided with the first intermediate shaft 4 as shown in the enlarged detail of FIGS. 2 to 4.
An input shaft 12 that is disposed on the same axis as the opposite side and is drivingly connected to the handle shaft 2 via input gears 10 and 11 that mesh with each other at the end opposite to the intermediate shaft 4; It is provided with a planetary gear type differential gear mechanism 13 arranged between the shaft 4 and the shaft 4. The differential gear mechanism 13 has a sun gear 14 as an input gear element fixed to the input shaft 12 connected to the handle 1 side and an output fixed to the intermediate shaft 4 connected to the wheels 8 and 8. A ring gear 15 as a gear element and, for example, three planetary pinions 16, 16, as reaction force gear elements interposed at equal angular intervals so as to mesh with the gears 14, 15 between the gears 14, 15 ,. Consists of. The pinions 16, 16, ... Are attached to the pinion carrier 18 which is rotatably fitted on the input shaft 12, and the pinion shafts 17, 17 ,.
It is carried through. In addition, the above pinion carrier
A sector gear 19 is formed at 18, and a pinion 21 fixed to a rotation output shaft 20a of a stepping motor 20 is meshed with the sector gear 19. .. as the reaction force gear element of the differential gear mechanism 13 are differentially controlled by the rotation of the stepping motor 20, that is, the pinion carrier 18 is rotated around the input shaft 12 to cause the carrier 18 to rotate. The planetary pinions 16, 16, ... carried on the pinion 1 are rotated by rolling between the sun gear 14 and the ring gear 15.
6,16, by increasing or decreasing control of the amount of rotation extending from the handle shaft 2 to the sun gear 14 by ... rolling of the ring gear 15 and the intermediate shaft 4, the wheel steering angle theta _W for steering angle theta _H
Is configured to change the transmission ratio R of.

On the other hand, 33 is a stepping motor of the transmission ratio varying means 9.
It is a controller consisting of a computer that outputs a control signal to 20 and differentially controls it. Output signals of a steering wheel steering angle sensor 30 for detecting a steering wheel steering angle θ _H of the steering wheel 1 and a vehicle speed sensor 31 for detecting a vehicle speed V of an automobile are input to the controller 33. As shown in detail in FIG. 5, the controller 33 sets the steering wheel steering angle θ _H and the vehicle speed V respectively detected by the steering wheel steering angle sensor 30 and the vehicle speed sensor 31 in advance as shown in FIG. A target transmission ratio calculation unit 35 for calculating a target transmission ratio R to be controlled by the transmission ratio variable unit 9 by collating and comparing with the characteristic map stored in the characteristic storage unit 34, and the calculation unit 35.
And a motor drive unit 36 for driving the stepping motor 20 so as to match the rotation angle corresponding to the calculated target transmission ratio R based on the output signal of The characteristic map is set so that the transmission ratio R of the wheel steering angle θ _{W to} the steering wheel steering angle θ _H increases as the vehicle speed V increases, as shown in the figure.

As a feature of the present invention, the output torque of the stepping motor 20 in the transmission ratio varying means 9 is limited to the drive load torque of the steering gear device 3 during the operation of the power steering mechanism 7, that is, the change in the vehicle speed, the road surface condition, and the like. Instead, by setting the load torque applied to the transmission ratio varying means 9 to drive the steering gear device 3 when the power steering mechanism 7 is activated, the transmission ratio varying means 9 is used when the power steering mechanism 7 is activated. It is possible to variably control the transmission ratio R so that the transmission ratio R becomes the preset target transmission ratio.
On the other hand, when the power steering mechanism 7 is not operated, the change of the transmission ratio R by the transmission ratio varying means 9 is restrained by stopping the transmission ratio variable control by the motor 20.

Therefore, in the above embodiment, while the vehicle is running,
When the steering wheel 1 is steered, its movement is transmitted to the input shaft 12 of the transmission ratio varying means 9 via the handle shaft 2 and the sun gear 14 of the differential gear mechanism 13 rotates. Further, the steering wheel angle θ _H that changes with the steering of the steering wheel 1 is detected by the steering wheel angle sensor 30, and the vehicle speed V at that time is detected by the vehicle speed sensor 31, and the outputs of both sensors 30, 31 are detected. A control signal is output from the controller 33 that receives the signal to the stepping motor 20 that controls the operation of the differential gear mechanism 13 to control the rotation of the motor 20, and the rotation of the motor 20 causes the pinion to pass through the pinion 21 and the sector gear 19. The carrier 18 is rotationally driven. That is, in the differential gear mechanism 13, the sun gear 14 rotates by an angle proportional to the steering angle θ _H of the steering wheel 1, and at the same time, the pinion carrier 18 is rotated according to the rotation angle of the stepping motor 20 controlled by the controller 33. Become so. Therefore, the ring gear of the differential gear mechanism 13 is
15 and the intermediate shaft 4 integrated therewith rotate by an angle obtained by increasing or decreasing the rotation angle of the pinion carrier 18 with respect to the steering angle θ _{H of the} steering wheel, and the rotation of the intermediate shaft 4 causes the wheels 8, 8 to rotate.
Is steered, whereby the transmission ratio R of the wheel steering angle θ _{W to} the steering wheel steering angle θ _H is variably controlled.

Further, the power steering mechanism 7 of the steering gear device 3 is operated in accordance with the rotation of the intermediate shafts 4 and 5 which are interlocked with the steering of the steering wheel 1, and the steering force from the steering wheel 1 to the wheels 8 is assisted.

In that case, the output torque of the stepping motor 20 is
Since it is larger than the drive load torque of the steering gear device 3 during the operation of the power steering mechanism 7,
When the power steering mechanism 7 is operated, the stepping motor 20 operates smoothly, and the transmission ratio R of the wheel steering angle θ _{W to} the steering wheel steering angle θ _H becomes the target transmission ratio according to the vehicle speed V as described above. It is variably controlled. on the other hand,
When the power steering mechanism 7 fails due to a failure or the like, the motor 20 stops driving the steering gear device 3, and as a result, variable control of the transmission ratio R by the transmission ratio varying means 9 becomes impossible. The ratio R is kept constant at the transmission ratio when the power steering mechanism 7 fails, so that the steering device can be made to function in the same manner as a normal one and its safety can be improved.

(Effects of the Invention) As described above, according to the present invention, a power steering system is provided for a steering apparatus of an automobile, which includes a transmission ratio varying unit that changes a transmission ratio of a wheel steering angle to a steering wheel steering angle and a power steering mechanism. By restraining the change of the transmission ratio in the transmission ratio varying means to the target transmission ratio when the mechanism is not operating, the wheel steering with respect to the steering angle of the steering wheel can be operated without operating the transmission ratio varying means when the power steering mechanism fails. The angle transmission ratio can be kept constant, and thus the safety of the steering device can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment of the present invention, FIG. 1 is a perspective view showing the overall construction of a steering device, FIG. 2 is a sectional view showing the construction of a transmission ratio varying means, FIG. FIG. 4 is a sectional view taken along the lines III-III and IV-IV of FIG. 2, FIG. 5 is a block diagram showing the configuration of the controller, and FIG. 6 is a characteristic diagram of a map read by the controller. 1 ... Steering handle, 3 ... Steering gear device, 7 ... Power steering mechanism, 8 ... Wheels, 9
...... Transmission ratio varying means, 13 ...... Differential gear mechanism, 14 ...... Sun gear, 15 ...... Ring gear, 16 ...... Planetary pinion,
18 …… Pinion carrier, 20 …… Stepping motor,
30 …… Handle steering angle sensor, 31 …… Vehicle speed sensor, 33 ……
controller.

Front page continuation (72) Inventor Norio Tsukaana 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) Reference JP-A-60-80967 (JP, A) , U) Japanese Patent Publication Sho 49-49542 (JP, B1)

Claims (1)

[Claims] 1. A transmission ratio varying means in a steering amount transmitting path for mechanically connecting a steering handle to a wheel through a steering gear device having a power steering mechanism and transmitting a steering amount of the steering handle to the wheel. Is provided to change the transmission ratio of the wheel steering angle to the steering wheel steering angle, wherein the transmission ratio varying means has a transmission ratio set in advance when the power steering mechanism operates. The target transmission ratio can be controlled so that the target transmission ratio cannot be controlled when the power steering mechanism is inactive, and changes in the transmission ratio are restricted. A steering device for an automobile.