JPH022703Y2 - - Google Patents

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 response to the steering of the front wheels. This invention relates to a four-wheel steering device that steers both the front wheels and the rear wheels by transmitting information to the wheels.

(Prior art) Conventionally, four-wheeled vehicles were typically steered by turning only the front wheels using a steering wheel.
It has been pointed out that steering only the front wheels causes problems in terms of maneuverability and steering, such as skidding of the rear wheels depending on the driving situation and a limit to the turning radius, making it impossible to make small turns. In view of this, four-wheel steering devices that steer both the front wheels and the rear wheels have 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 vehicle's attitude 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. steer in the same direction,
When making a large turn, steer the rear wheels in the opposite direction 4
It can be seen that a wheel steering device is required.

In principle, the four-wheel steering system described above can be realized using various methods, and although many systems using electrical means and hydraulic means have been proposed, these tend to have complex structures and are relatively difficult to implement. The price is high;
Furthermore, problems tend to arise in terms of maintenance and reliability such as safety in the event of failure. For this reason, the structure is simple, in which the control force that controls the operation of the front wheel steering device and the operation of the rear wheel steering device is transmitted by mechanical means, and the rear wheel steering device is actuated by this control force. A highly reliable four-wheel steering system has also been proposed. For example, as disclosed in Japanese Patent Application Laid-open No. 58-214466, a front wheel steering mechanism and a rear wheel steering mechanism are mechanically connected by a transmission rod, and the front wheel steering operation is performed by rotation of the transmission rod. There is a device that transmits the information to a rear wheel steering mechanism and steers the rear wheels along with the front wheels.

In such cases, the front wheel steering mechanism and the rear wheel steering mechanism are placed near the front and rear wheel axles, respectively, so the length of the transmission rod that connects the two mechanisms and transmits the steering force becomes longer. , it is often desirable to support the transmission rod in an intermediate section. In particular, when placing a transmission rod, in order to avoid interference with other parts, the rod is often divided into several parts and each rod is connected by a conversal joint. becomes essential. The transmission rod is supported by the vehicle body using bearings so that the rod can rotate, but when supporting this at multiple locations, errors in the mounting position of the bearings may cause the transmission rod and bearing to There is a problem in that it causes problems such as prying. In other words, if the mounting position of the bearing deviates from its normal position due to dimensional errors in the mounting parts, assembly errors, etc., the transmission rod will also deviate from its normal position, and the mounting angle of the transmission rod will deviate, causing the transmission rod and bearing to deviate. There is a problem in that the durability of the rods and bearings is reduced due to prying that occurs during the process.

Furthermore, even if the bearings are installed correctly, the external forces applied to the car body while driving will cause the car body to undergo elastic deformation to some extent, and this deformation may result in the bearings being misaligned, causing the same problem as above. be.

(Purpose of the invention) The present invention was developed in view of the above-mentioned problem, and is designed to solve the problem when the mounting position of the support bearing of the transmission rod that mechanically transmits steering operation from the front wheel steering mechanism to the rear wheel steering mechanism is misaligned. It is an object of the present invention to provide a four-wheel steering device for a vehicle that prevents excessive force such as prying from being applied between a transmission rod and a support bearing.

(Structure of the invention) The four-wheel steering device of the invention supports a transmission rod that transmits front wheel steering operation to a rear wheel steering mechanism on the underside of the floor via at least two bearings, The radial support stiffness of the bearing to the bottom surface of the floor is
It is characterized by having lower radial support rigidity than other bearings.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

1 and 2 are a plan view and a front view showing an example of a four-wheel steering system according to the present invention, in which the direction of arrow F indicates the front of the vehicle. The steering wheel 1 is connected to the first steering wheel via the steering shaft 1a.
1st pinion in pinion case 2 (not shown)
The first pinion rotates when the steering wheel 1 is operated. The first pinion meshes with a rack of a first rack shaft (not shown) disposed slidably in the vehicle width direction within the first gearbox 3, and rotation of the first pinion causes the first rack shaft to move in the vehicle width direction. move in the direction. Both ends of the first rack shaft are connected to right and left tie rods 4a and 4b, respectively,
Therefore, due to the movement of the first rack shaft in the vehicle width direction, the tie rods 4a, 4b are connected to each other via the tie rods 4a, 4b.
Front wheel steering is performed by moving the knuckle arm connected to the knuckle 4b and steering the front wheel 5 rotatably supported by the knuckle. Note that a known power cylinder mechanism may be provided in the first gear box 3 to reduce the steering force of the steering wheel 1.

Further, a second gear box 8 is integrally connected to the first gear box 3 via a connecting wall 6, and a second gear box 8 is provided in the second gear box 8, which is parallel to the first rack axis and located at the rear and lower part of the first rack axis. Two rack shafts (not shown) are arranged to be slidable in the vehicle width direction. Note that the first gearbox 3 is fixed to the vehicle body by mounting members 10a, 10b on brackets 11a, 11b of the vehicle body 11, so that the first gearbox 3
The second gearbox 8, which is integrally coupled with the second gearbox 8, is also fixedly held. The first rack shaft and the second rack shaft are connected by a connecting arm 7, and when the first rack shaft is moved in the vehicle width direction by operating the steering wheel 1, the second rack shaft is also moved together. A second pinion (not shown) rotatably disposed within the second pinion case 9 meshes with the rack of the second rack shaft, and rotates the second pinion in response to movement of the second rack shaft.

The output shaft 9a of this second pinion protrudes rearward from the second pinion case 9, and this output shaft 9a connects the first to third propeller shafts 16 to 18 and the first to fourth universal joints 12 to 15 that connect these. It is connected to the input shaft 41 of the variable steering ratio mechanism 40 via. Although it is possible to use a single propeller shaft for this connection, in order to prevent interference between the propeller shaft and other parts, it is possible to divide the shaft into three parts, connect each part with a universal joint, and connect the shaft, etc. This increases the degree of freedom in placement. If this continues, the propeller shaft will hang downward, so the second propeller shaft 17 is rotatably supported by the vehicle body 11 by the two support bearings 20 and 30.
Of these, the front support bearing 20 is indicated by the arrow A-
As shown in FIG. 2, which is a sectional view taken along line A, it is attached to the vehicle body 11 via a support plate 19a that is fixed to the vehicle body 11 and supports the support bearing 20, while the rear support bearing 30 is attached to the vehicle body 11 via a bracket 19b fixed to the lower surface of the floor of the vehicle body 11.

The rotation of the second pinion is transmitted to the variable steering ratio mechanism 40 via the first to third propeller shafts 16 to 18, thereby rotating the input shaft 41 of this mechanism 40. The variable steering ratio mechanism 40 controls the ratio of the rear wheel steering angle to the front wheel steering angle (steering ratio) according to vehicle speed, etc., and uses signals from a vehicle speed sensor (not shown) and an angle sensor 42, etc. Based on this, the steering ratio is variably controlled by driving the step motor 43. For example, when driving at low speeds, the rear wheels are steered in the opposite phase to the front wheels to improve turning performance, and when driving at high speeds, they are steered in the same phase to improve driving stability during lane changes, etc., to improve turning performance at low speeds. This makes it possible to satisfy both stability at high speeds. For this reason, the steering ratio variable mechanism 40
, the input shaft 41 is controlled to increase, decelerate, or reverse the rotation, and then engages with a third rack shaft (not shown) disposed in the third gear box 51 so as to be slidable in the vehicle width direction. The rotation after the above control is transmitted to a third pinion (not shown). Therefore, the third rack shaft is moved in the vehicle width direction based on the steering ratio that is variably controlled by the variable steering ratio mechanism 40.
The rear wheel 53 is steered by rotating the knuckle through right and left tie rods 52a and 52b connected to both ends of the third rack shaft. In this case, the steering angle of the rear wheels 53 with respect to the steering angle of the front wheels 5 will differ depending on the steering ratio controlled by the variable steering ratio mechanism 40. Note that a known power sling mechanism may be disposed within the third gear box 51.

4 and 5 show support bearings 20, 30 supporting the second propeller shaft 17 of FIG.
FIG. The support bearing 20 on the front side of the vehicle body is supported by the support plate 19a via a thin rubber layer 21 that wraps around the outer periphery of the outer race 22, and a needle roller 23 is disposed between the outer race 22 and the outer peripheral surface of the second propeller shaft 17. be done. That is, the second propeller shaft 17 also serves as an inner race of this bearing, and therefore the shaft 17 is rotatable and slidable in the axial direction with respect to the support bearing 20. Oil seals 24a and 24b are arranged on both sides of the needle roller 23 to prevent lubricating grease from the needle roller 23 from escaping. In addition,
A yoke 13a for the second universal joint 13, fixed in the axial direction by a pin 13b, is attached to the tip of the shaft 17 and connected to a spline.

On the other hand, the support bearing 30 on the rear side of the vehicle body is supported by the bracket 19b via a thick cylindrical rubber body 31 disposed around the outer periphery of the outer race 33 and a retaining ring 32 surrounding the rubber body 31. Similar to the support bearing 20 on the front side of the vehicle body, this support bearing 30 also has a needle roller 34 sandwiched between the outer peripheral surface of the second propeller shaft 17 and the inner peripheral surface of the outer race 33. is rotatable and slidable in the axial direction, and oil seals 35a and 35b for sealing in lubricating grease are arranged on both sides of the needle roller 34. Further, a yoke 14a for the third universal joint 14, which is fixed in the axial direction by a pin 14b, is attached to the rear end of the shaft 17 by spline connection.

In the four-wheel steering system for a vehicle configured as described above, the propeller shaft that transmits steering operation from the front wheels to the rear wheels is supported by two support bearings 20 and 30. The side support bearing 30 is attached to the vehicle body via a thick cylindrical rubber body 31. Therefore, even if the support bearing is misaligned due to assembly errors, deformation of the vehicle body, etc., this misalignment can be absorbed by the deformation of the rubber body 31, which prevents straining between the bearing and the shaft. There aren't many things.

From the point of view of absorbing misalignment of the bearings, both bearings 20 and 30 may be attached to the vehicle body through thick rubber bodies, but in this case, the support of the shaft becomes unstable and the Problems such as increased vibration of the shaft due to vibration tend to occur, and the support rigidity of one of the support bearings needs to be increased. Therefore, in the embodiment described above, the support bearing 20 on the front side of the vehicle body is provided with a thin rubber layer 21 so as to have high support rigidity. Although this rubber layer 21 may be omitted, it is preferable to provide it in order to absorb vibrations and prevent noise generation. Further, in the embodiment described above, the support rigidity of the support bearing on the front side of the vehicle body is increased, and the reason for this will be explained below. As can be seen from FIG. 2, on the front side of the vehicle body, the propeller shaft is arranged in a tunnel in the floor, and the front support bearing is also arranged in the tunnel. On the other hand, engine exhaust pipes are often placed inside this tunnel.
For this reason, the front support bearing is supported through a thin rubber layer to avoid thermal deterioration of the rubber due to the heat of the exhaust pipe.

(Effects of the invention) As explained above, according to the invention, the shaft that transmits steering operation from the front wheels to the rear wheels is supported on the lower surface of the vehicle floor by a plurality of bearings, and the radius of any one bearing is Since the directional support rigidity is lower than the radial support rigidity of other bearings, dimensional errors of parts,
If the mounting position of the support bearing shifts due to assembly errors, or if the bearing shifts due to deformation of the vehicle body due to external force applied to the vehicle body while driving,
This positional shift can be absorbed by the bearing with low support rigidity, and it is possible to prevent straining between the bearing and the shaft. As a result,
The durability of shafts and bearings can be improved. Furthermore, since the support rigidity of the other bearings is high, the support of the shaft will not become unstable and the shaft will not vibrate greatly due to vibrations of the vehicle body.

[Brief explanation of drawings]

1 and 2 are a plan view and a front view showing an example of a four-wheel steering device according to the present invention, FIG. 3 is a sectional view taken along arrow A-A in FIG. 2, and FIGS. FIG. 5 is a sectional view showing two bearing parts for supporting the propeller shaft in the four-wheel steering system of the present invention. 1... Steering wheel, 3... First gear box, 5... Front wheel, 8... Second gear box, 12, 13, 14, 15... Universal joint, 16, 17, 18... Propeller shaft, 20, 21...Support bearing, 22, 33
... Outer race, 23, 34 ... Needle roller, 40 ... Steering ratio variable mechanism, 51 ... Third gear box.

Claims (1)

[Scope of Claim for Utility Model Registration] In a four-wheel steering system for a vehicle in which the front wheels and the rear wheels are steered by a steering operation, the steering operation includes at least two
The rotation of the transmission rod supported on the lower surface of the floor by two bearings is transmitted to the rear wheel steering mechanism, and the radial support rigidity of any one of the bearings with respect to the lower surface of the floor is the same as the radial direction of the other bearing. A four-wheel steering device for a vehicle, characterized in that the stiffness is lower than that of a support.