JPS61108070A - Four-wheel steering device for car - Google Patents

Abstract

PURPOSE:To improve the running stabily by proventing the extreme variation of an oscillating member that controls the steering force even if a malfunction is generated in a controller that controls the steering ratio. CONSTITUTION:An oscillating shaft 23 is stretched on a horizontal level and supported by an oscillating support shaft 24 that is stretched vertically. An oscillating gear 25 within a gear 25a on the tip is fixed to this support shaft 24 and the oscillating shaft 23 is oscillated by the oscillation of this oscillating gear 25. The gear 25a of the oscillating gear engages with a worm 26 and this worm 26 is rotated by a stepping motor 29 through gears 28 and 26. The rotation of the stepping motor is controlled based on a control signal coming from an electric controller 32 which receives the signals coming from an electric controller 32 which receives the signals coming from an angle of oscillation angle 30 that senses the angle of oscillation of the oscillating shaft 23 provided on the oscillating support shaft 24 and a car speed sensor 31 that detects the car speed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a four-wheel steering device that can also steer the rear wheels in accordance with the steering of the front wheels. The present invention relates to a four-wheel steering device that can variably control the ratio according to vehicle speed and the like.

(Prior art) Conventionally, four-wheeled vehicles were typically steered by using a steering wheel to steer only the front wheels. However, steering only the front wheels may cause the rear wheels to skid depending on the driving conditions, or the turning radius may be affected. Problems have been pointed out in terms of maneuverability and steering, such as the limited ability to make small turns, and in light of this, a four-wheel steering system that steers the rear wheels as well as the front wheels has recently been proposed and researched. .

In other words, with a four-wheel steering system, when driving at relatively high speeds, if the rear wheels are steered in the same direction as the front wheels (this is called in-phase steering), lateral forces are applied to the front and rear wheels at the same time. Because of this, there is no phase lag from the steering wheel steering, and the attitude of the vehicle can be maintained almost on the tangent to the turning circle, allowing smooth lane changes, for example, when driving at high speeds. Also, if the rear wheels are steered in the opposite direction to the front wheels when driving at very low speeds (this is called reverse phase steering), the direction of the vehicle can be changed significantly, which is convenient for parallel parking or parking in a garage.

Furthermore, considering that the front wheels are not steered significantly at relatively high speeds, and the front wheels are steered significantly when driving at relatively low speeds, the rear wheels are also steered within the range where the front wheels are steered small. It can be seen that a four-wheel steering system is required that steers the rear wheels in the same direction and steers the rear wheels in the opposite direction when turning a large amount.

For this reason, we have provided a mechanism that can arbitrarily variably control the ratio of the steering angle of the rear wheels to the steering angle of the front wheels, that is, the steering ratio, and adjust the steering ratio according to vehicle speed, front wheel steering angle, etc. It has been proposed to perform variable control to improve maneuverability, driving stability, etc. For example, as disclosed in Japanese Patent Application Laid-Open No. 59-26364, one end of a connecting condo is connected to a steering force transmission shaft from a front wheel steering device, and the other end is connected to a tie rod for rear wheel steering. There is a device in which the rotor is also connected to an arm member and the arm member is swung through a worm gear mechanism, thereby making it possible to vary the rotation locus of the other end of the connected condo and control the steering ratio. Furthermore, the applicant has proposed a connecting condo in which the direction of the swinging surface is variable via a swinging member operated by a bevel gear mechanism connected to a steering force transmission shaft from a front wheel steering device and a worm gear mechanism. proposed a device that can variably control the steering force using the following method (this device will be described later).

In such a device that can variable control the steering ratio,
The steering ratio is adjusted according to the size of the swing angle by swinging the swing arm or the swing member.This swing is performed by an external drive means such as a step motor, and depending on the size of the swing angle. Based on detection signals such as vehicle speed and front wheel steering angle,
It is controlled by an electric controller or the like. Therefore, in the event of a failure of the external drive means, malfunction of the controller, etc., it becomes impossible to control the swing angle, which immediately deteriorates maneuverability and running stability, which is undesirable from a safety point of view. There's a problem.

(Purpose of the Invention) The present invention has been made in view of the above-mentioned problems, and is intended to solve the problem when a malfunction of the controller for adjusting the steering ratio or a failure of the drive means for swinging the swinging member occurs. Another object of the present invention is to provide a four-wheel steering system for a vehicle that can prevent extreme fluctuations in the rocking angle and prevent extreme deterioration of maneuverability and running stability, thereby improving safety. That is.

(Structure of the Invention) The four-wheel steering device of the present invention transmits a part of the steering force of the steering mechanism that steers the front wheels to the rear wheel steering member via the power transmission system, and steers the rear wheels as well as the front wheels. This is an @ placement that allows you to do this.

A variable steering ratio mechanism that changes the transmission ratio of the steering force to the rear wheels is placed in the middle of the power transmission system, and this variable steering ratio mechanism meshes with the drive gear of this mechanism to achieve high speed steering. A swing gear that changes the steering ratio by moving a member that changes the steering ratio, and a stopper that is provided in a case that supports the drive gear and restricts the swing gear from swinging beyond a predetermined amount. This is a characteristic feature.

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

FIG. 1 is a schematic diagram showing one embodiment of a four-wheel steering system according to the present invention. The steering wheel 1 is connected to a first pinion 2 via a steering shaft 1a, and the first pinion 2 meshes with a rack of a first rack shaft 3 that is slidable in the vehicle width direction. Right and external tie rods 4a, 4b are connected to both ends of the first rack shaft 3, and the tie rods 4a, 4
Reference numeral b denotes a knuckle 5a that supports the right and left front wheels 6a to the vehicle body so as to be steerable.

Connect with arm 5b (note that the left tie rod 4b, knuckle 5b, and front wheel 6b are not shown because they are symmetrical)
. Therefore, the first rack shaft 3 moves in the vehicle width direction in response to the operation of the steering wheel 1, and this movement moves to the knuckle 5a via the tie rods 4a and 4b.

5b, and the front wheels 6a and 6b are steered.

On the other hand, the first rack shaft 3 has a second rack parallel to the first rack shaft 3.
A rack shaft 7 is integrally connected via a connecting portion 1a, and a second
A second pinion 8 is meshed with the rack of the rack shaft 7 to obtain steering force to be transmitted to the rear wheels. Therefore, when the first rack shaft 3 is moved in the vehicle width direction, the second rack shaft 7 is also moved in the same direction, and the second pinion 8 is rotated.

The rotation of the second pinion 8 is transmitted to the variable steering ratio mechanism 10 via a power transmission shaft 9 connected to the second pinion 8, and the rear wheels are steered according to the steering ratio adjusted here. Ru. In this way, the rear wheels can be steered in accordance with the front wheels steered.

Next, the variable steering ratio mechanism 10 will be explained. The front end of the power transmission shaft 9 is connected to the second pinion 8. The I end of the power transmission shaft 9 is connected to the third pinion 11, and the third pinion 11 is connected to the rotation shaft 1.
2b meshes with a bevel gear 12 supported by the vehicle body. At one location on the circumference of the bevel gear 12, there is a condo support hole 12a.
is formed, and the connecting rod 1 is inserted into this rod support hole 12a.
3 is rotatably inserted into the bevel gear 12 and slidably in the axial direction of the rod 13. One end 13a of the rod 13
are connected by a ball joint to connecting arms 14a and 14b which are connected to the third rack shaft 11 for steering the rear wheels via a control valve 15 for power steering. The third rack shaft 17 is held slidably in the rear wheel gear box 1 in the vehicle width direction, and both ends of the third rack shaft 17 are connected to the right and left knuckles 19a via right and left circular tie rods 18a and 18b. , 19b. Since the right knuckles 19a and 19b support the rear wheels 20a and 20b so as to be steerable relative to the vehicle body, the rear wheels are steered by movement of the third rack shaft 17 in the vehicle width direction. Note that the tie rod, knuckle, and rear wheel are symmetrical, so only the right side is shown. Third rack shaft 11
Movement in the vehicle width direction is carried out by the movement of one end 13a of the connecting rod 13 in the vehicle width direction accompanying the rotation of the bevel gear 12 being transmitted to the third rack shaft 17 via the connecting arms 14a, 14b. At this time, the connecting arms 14a, 14
By the action of the control valve 15 installed on the rear wheel b, pressure oil from the pump 21 is appropriately sent into the cylinder in the rear wheel gear box 16 to assist the movement of the third rack shaft 11.

Next, a mechanism for moving one end 13a of the connecting rod 13 in the vehicle width direction in accordance with the rotation of the bevel gear 12 will be described. The other end 13b of the connecting rod 13 is connected to the tip of a pendulum arm 22 via a ball joint, and this pendulum arm 22 is connected to a swing shaft 23 that is perpendicular to this arm 22. It can be rotated freely. The swing shaft 23 extends and is supported in a horizontal plane by a swing support shaft 24 extending vertically, and swings in the horizontal plane in accordance with the rotation of the swing support shaft 24. Since the rotating surface of the pendulum arm 22 is tilted in accordance with the swinging of the swing shaft 23, the rate at which the one end 13a of the connecting rod 13 is moved in the vehicle width direction varies in accordance with the rotation of the bevel gear 12.

This operation will be explained using a schematic plan view of the variable steering ratio mechanism shown in FIG. First, consider the case where the swing shaft 23 extends in the vehicle width direction and is located on the same straight line as the rotation shaft 12b of the bevel gear 12. Note that the connecting rod 13 is 9113.
a is also located on the rotation axis of the bevel gear 12. At this time, when the bevel gear 12 is rotated, the connecting rod 13 moves and moves on a conical surface with one end 13a as the apex and the connecting rod 13 as the ridgeline, and the pendulum arm 22 moves on the bottom surface of this cone. Therefore, even if the bevel gear 9 rotates, the one end 13a does not move. That is, at this time, the rear wheels are not steered while the front wheels are steered. From this state, the swing support shaft 24 is rotated, and the swing support shaft 24 is rotated as shown in the figure.
When the pendulum is tilted counterclockwise by "e" in the horizontal plane, the surface of rotation of the pendulum no. 6220 is also tilted by "θ" with respect to the base of the cone. For this reason, for example, by rotating the bevel gear 12,
In FIG. 2, if the angle between the connecting rod 13 and the rotating shaft 12b of the hevel gear 12 is set to be αl, the other end 13b of the connecting rod 13 will be at the position 13b' at a distance #dl.
Therefore, one end 13a also moves approximately the same distance to the position 13a'. As a result of this movement, the third rack shaft 17 is similarly moved and the rear wheels are steered. As can be seen from this figure, the ratio of the rear wheel medium-long steering angle to the front wheel steering angle, that is, the steering ratio, is the same as the amount of movement of the - end 13a of the connecting rod 13 with respect to the rotation of the bevel gear 12, and the swing shaft 23 The steering ratio can be changed depending on the magnitude of the inclination "θ゛'" in the horizontal plane.Furthermore, the swing shaft 23 can be tilted not only counterclockwise as described above but also clockwise. In this case, the moving direction of -rA13a of the connecting rod 13 with respect to the rotation of the bevel gear 12 is opposite to the above case.Thereby, the rear wheels can be steered in the same phase or in the opposite phase with respect to the front wheels. I can do it.

Next, a mechanism for swinging the swing shaft 23 in a horizontal plane will be explained. The swing shaft 23 extends in a horizontal plane and is supported by a swing support @24 extending vertically, and a swing gear 25 having a gear 25a at the tip is fixed to the swing support shaft 24. The swinging of the swinging gear 25 about the swinging support shaft 24 rotates the swinging support shaft 24, and the swinging shaft 23 swings. The gear 25a of the swing gear 25 meshes with a worm 26, and the worm 26 meshes with a first bevel gear 28 provided on the output shaft 29a of the step motor 29 and a first bevel gear 28 provided on the same axis as the worm 26. Step motor 29 via two skewers 27
Rotated by The rotation of this step motor 29 is
Based on control signals from an electric controller 32 that receives detection signals from a swing angle sensor 30 provided on the swing support shaft 24 to detect the swing angle of the swing shaft 23 and a vehicle speed sensor 31 to detect vehicle speed. controlled.

The third example shows an example of control by the electric controller 32.
In this way, the rear wheel steering angle relative to the steering wheel steering angle (front wheel steering angle), that is, the steering ratio, is changed according to the vehicle speed. In this example, in the low speed range, the rear wheels are steered in opposite phases to improve turning performance.
At high speeds, the wheels are steered in the same phase to improve driving stability.

FIG. 4 is a sectional view showing a portion of the variable steering ratio mechanism 10 in which the swing gear 25 is swung by the step motor 29, and this portion will be described in detail. A step motor 29 is fixed to the casing 34 of the variable steering ratio mechanism 10, and the step motor 29 protrudes into the casing 34.
A first bevel gear 28 is fixed to the output shaft 29a. The second bevel gear 21 meshing with the first hooked gear 28 is fixed to a worm shaft 26a, and the worm shaft 26a is supported by the casing 34 via bearings 35 and 37. The worm 26 attached to this worm shaft 26a
meshes with the gear 25a of the swing gear 25, and the swing gear 25 swings about the swing support shaft 24 in accordance with the rotation of the worm 26.

Therefore, when the step motor 29 is driven based on the control signal from the electric controller 32 as described above,
The swing gear 25 swings via the bevel gears 27, 28, the worm 26, etc., and as a result, the swing @23 swings via the swing support shaft 24, thereby performing variable control of the steering ratio. At this time, the swing gear 25 responds to the rotation of the step motor 29.
If there is any play in the rocking of the oscillating gear, the rear wheel steering angle will be undesirably deviated from the front wheel steering. We must try to make it as small as possible. For this reason, a spring 36 is arranged on the side surface of a bearing 35 (upper side in the figure) that supports the worm shaft 26a.
This is to eliminate play in the axial direction. Furthermore, as shown in FIG. 5, which is a cross-sectional view taken along the arrow A-A, the outer race 38 of the other bearing 37 has a diameter of 180 mm.
A bearing 37 is configured to be able to slide freely in the left and right directions in the figure along a guide member 40, 40 that forms two planes 38a, 38a separated by 38 degrees, and that these planes come into contact with. It is biased to the right by a spring 39. As a result, the worm 26 is urged against the gear 25a, and the worm 26 due to backlash is
This suppresses the occurrence of play between the gear 25a and the gear 25a.

On the other hand, the steering ratio is controlled within a certain range as explained in FIG. The lJ range is also limited to a certain range. Therefore, two stopper bins 33a, 3 are provided to prevent the swing gear 25 from swinging beyond this certain range.
3b is fixed to the casing 34.

For this reason, for example, if the step motor breaks down or the electric controller 32 goes out of control, the I! ! ! Even if the moving gear 25 attempts to swing beyond the above-mentioned certain range, the stopper pin 33a
, 33b restricts further rocking, so the steering ratio does not fluctuate indefinitely, and safety can be ensured. Also, when assembling this device, the swing angle sensor 3
When positioning the swing gear %y25 relative to 0, for example, the swing gear 25 is held in a position against the stopper pin 33a as shown by the chain line in FIG.
By setting the value of , positioning can be performed without using a positioning jig or the like, and the ease of assembly is improved.

(Effects of the Invention) As explained above, according to the present invention, in the variable steering ratio mechanism, the swinging mechanism meshes with the drive gear and swings, and the swinging motion moves the member that changes the steering ratio. A stopper is provided to prevent the gear from swinging more than a predetermined amount, so even if the drive means (for example, a step motor) that drives the drive gear fails or the controller that controls the amount of swing goes out of control, It is possible to maintain the steering ratio within a predetermined range and prevent extreme deterioration of maneuverability and running stability. Therefore, stability can be ensured even if the above-mentioned failure occurs while the vehicle is running.

Furthermore, since the stopper can be used for positioning during assembly, positioning and assembly can be easily performed without the need for a special positioning jig, thereby improving assembly efficiency.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a four-wheel steering device according to the present invention, FIG. 2 is a schematic plan view of a variable steering ratio mechanism used in the four-wheel steering device according to the present invention, and FIG. 3 is a schematic diagram showing an example of a four-wheel steering device according to the present invention. A graph showing an example of steering ratio control by the four-wheel steering device according to the invention, FIG. 4 is a sectional view of a variable steering ratio mechanism used in the four-wheel steering device according to the invention, and FIG. FIG. 2 is a cross-sectional view taken along arrow A-A of 1... Steering wheel 3... First rack shaft 7... Second rack shaft 8... Second binion 9... Power transmission shaft 10... Variable steering ratio mechanism 12... Bevel gear 13... Connecting rod 16... Rear wheel gear box 22... Pendulum arm 23... Rocking shaft 24... Rocking support shaft 25... Rocking gear 26... Worm 29. - Step motor 30... Rocking angle sensor 31... Vehicle speed sensor 32...
Controller 34...Casing Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] A four-wheel steering system for a vehicle in which the front wheels and the rear wheels are steered by a steering operation, in which a part of the steering force in the steering mechanism that steers the front wheels is transferred to the rear wheel steering member. A variable steering ratio mechanism that changes the transmission ratio of the steering force is disposed in the middle of the power transmission system, and the variable steering ratio mechanism is connected to a drive means for driving the mechanism. a drive gear that meshes with the drive gear and swings to move a steering ratio changing member to change the steering ratio; 1. A four-wheel steering device for a vehicle, characterized in that a stopper is provided to restrict rocking beyond a predetermined amount.