JPH0427672A - Rear wheel steering device for four-wheel steering vehicle - Google Patents

Abstract

PURPOSE:To ensure safety during fail by bringing a rod body into a rotatable state by dislocating a rod rotation regulating means during fail, such as runaway of a motor, racing the rod body also togetherwith a means to be transmitted when the means to be transmitted is rotated, and producing the non-steering state of rear wheels. CONSTITUTION:An engaging groove 23 is formed in a large diameter part 2a formed to a part of a rod body 2 with which a part of the steering link mechanism of a rear wheel is formed, and an engaging pin 25 being a rod rotation regulating means engageable with the engaging groove is formed in a manner to be capable of being driven by means of an electromagnetic solenoid 24. During ordinary operation, the engaging pin 25 is engaged with the engaging groove 23 of the rod body 2 to regulate rotation thereof, a steering force for rear wheels is converted through a ball screw mechanism 21 by means of a large gear 20 to which rotation is transmitted and transmitted to the rod body 2, and given control of steering of rear wheels is practicable. Meanwhile, during fail, such as runaway of a motor 11, by releasing the engaging pin 25 from engagement, the rod body 2 is brought into a rotatable state, and even when the large gear 20 is rotated, the rod body 2 is raced togetherwith the large gear and the non-steering state of rear wheels is produced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a rear wheel steering device for a four-wheel steered vehicle that steers the rear wheels in opposite phase or in the same phase as the front wheels in response to a steering operation. I am inspired by the improvement.

[Conventional technology]

For example, when driving at low speeds, the steering directions of the front and rear wheels are set in opposite phases to reduce the turning radius of the vehicle to improve tight turning performance, or when driving at high speeds, the steering directions of the front and rear wheels are set in the same phase to stabilize the vehicle's running. Four-wheel steering vehicles with improved performance are attracting attention. Rear wheel steering devices for such four-wheel steering vehicles include, for example, a mechanical type as disclosed in Japanese Patent Laid-Open No. 59-26364, a hydraulic type as disclosed in Japanese Patent Laid-Open No. 59-81261, etc. Furthermore, JP-A-61
Various configurations have been proposed in the past, including an electric type as shown in Japanese Patent No. 202977. In other words, in order to steer the rear wheels according to the steering angle of the front wheels, the front and rear wheels may be mechanically connected through a steering force transmission port, etc. The angle is detected and the resulting hydraulic or electrical signal is used to drive the rear wheel hydraulic power steering device, or the front wheel steering angle is used as an electrical signal to drive the rear wheel electric power steering device. It was configured to transmit information to a motor.

By the way, a problem with this type of four-wheel steering vehicle is that the rear wheels, which are steerably supported by the steering link mechanism, may fail in the drive mechanism or its control system that steers the rear wheels. There is a need for a structure that protects the vehicle from runaway, etc., and prevents the rear wheels from turning unnecessarily or wobbling in the event of a failure. In other words, many rear wheel steering devices that control the steering of the rear wheels use electrical components such as electric motors and controllers because they can be configured independently from the front wheels and can be easily controlled. If these electrical components break down or malfunction, the necessary steering control cannot be performed, which poses a problem in ensuring maneuverability and running stability.

As a fail-safe against this kind of problem, all electrical control signal systems are turned off, a centering spring is installed in a part of the rear wheel steering system, and the rear wheels are always kept neutral by resisting various external forces. It is being considered that by attaching a mechanical locking mechanism or the like to maintain the rear wheel steering system in the neutral position, it is possible to maintain the rear wheel steering system in a neutral position, that is, in a non-steering state, and to put the front wheels in a two-wheel steering state. .

The present applicant has previously proposed a centering spring mechanism with a locking mechanism as shown in Japanese Utility Model Application Publication No. 1-1.44278 as a seven ale safe for such a rear wheel steering system.

[Problem to be solved by the invention]

However, according to the rear wheel steering device using the above-mentioned centering spring mechanism with a locking mechanism, it is possible to return the rear wheels to the neutral position and maintain a non-steerable state in the event of a failure such as a failure of the electrical control system. Although the necessary functions can be obtained, the following problems arise. That is,
For example, if an electric motor or the like that serves as the device's drive source runs out of control and its rotational driving force is transmitted via the transmission system to a part of the rear wheel steering system that makes up the steering link mechanism, the above-mentioned centering spring will prevent the electric motor from running out of control. The restraint retention function etc. of the F11 cannot be expected at all, and this cannot be completely avoided even if the movement of the steering system is restricted using a locking mechanism, and furthermore, the side of such a lock F11 will be damaged. There is a risk of causing problems such as such problems, and there is a need for some kind of solution that can meet the demands of protecting the rear wheel steering system and ensuring its safety in the event of a failure of each component, including such runaway. It is hoped that countermeasures will be taken.

[Means to solve the problem]

In order to meet such demands, a rear wheel steering device for a four-wheel steering vehicle according to the present invention constitutes a part of a rear wheel steering link mechanism, and is supported movably in the axial direction within a cylindrical housing. a rod body, a transmission means that is rotatably supported within the cylindrical housing and is rotatably mounted on a part of the rod body via a screw mechanism, and transmits the rear wheel steering force as rotational power; The rod rotation regulating means is provided with a rod rotation regulating means that can freely move forward and backward and protrudes from a direction perpendicular to the axial direction so as to be able to engage with an engaging part provided in a part of the rod body in the axial direction. , is normally engaged with the engaging portion of the rod body, and the rod body is made movable in the axial direction by the screw mechanism by rotation transmission to the transmitted means, and in the event of a failure, the engaging portion of the rod body The structure is such that the engagement state with respect to the handle is released.

[Effect]

According to the present invention, during normal operation, the rod rotation regulating means engages with the engaging portion of the rod body to regulate its rotation, and the transmitted means that receives the rotation transmits the rear wheel steering force through the mechanism b. is converted and transmitted to the rod body, and the required rear wheel steering control can be performed.In addition, in the event of a failure such as a runaway motor, the rod rotation regulating means is removed to allow the rod body to rotate, thereby reducing the Even when the transmission means rotates, the rod body also rotates idly, thereby maintaining the non-steerable state of the rear wheels.

〔Example〕

FIG. 1 shows an embodiment of a rear wheel steering device for a four-wheel steering vehicle according to the present invention, and in the figure, in this embodiment, an electric motor 11. A case will be described in which an electric power steering device W10 using the following is adopted. In the figure, first, the rear wheel steering device, which is designated as a whole by reference numeral 1, includes a rod body 2 (not shown) that is horizontally suspended between left and right rear wheels and constitutes a rear wheel side steering link mechanism, and this rod body 2. (bracket)-3a) is installed through the vehicle body (not shown) at both ends in the axial direction.
, 3b, and a device body portion 5 of the electric power steering device 10 that is integrally connected to a part of the cylindrical housing portion 4.
The steering body includes a steering body, and an electric motor 11 that is disposed substantially parallel to the side of the body, is fixedly attached to the device body portion 5 side, and applies rear wheel steering force to the rod body 2.

Note that both ends of the rod body 2 are connected to tie rods (not shown) for transmitting rear wheel steering force to the left and right rear wheels, for example, via ball joints or the like.

Further, reference numeral 6 denotes a flange member 6 which is disposed facing the rod body 2 at a predetermined interval using a fitting device, and whose outer end side is locked by a stop ring so that the flange member 6 can slide only inwardly.
By pressing the flange members 6a and 6b interposed between a and 6b against the stopper parts 7a and 7b formed on the housing part 4 side, the rod body 2 and the rear wheel are returned to a neutral state and held at that position. It is a centering spring that prevents movement.

Furthermore, 12 is provided on the motor shaft 11a of the motor 1-1 and meshes with a large gear 20 which is a transmitted gear described later, thereby reducing the speed and transmitting the rotational power for steering the rear wheels from the motor 11. This is a small gear that makes up a gear mechanism. Here, although not shown in the drawings, the electric motor 11- of the electric power steering device W10 is configured to control the steering direction of the front wheels by the steering operation.
Needless to say, it is rotated as appropriate in response to control signals from a controller, which inputs various driving conditions such as the steering angle and vehicle speed, and also inputs feedback signals from rear wheel steering angle sensors and the like.

Now, according to the present invention, in the rear wheel steering bag W1 of the four-wheel steering vehicle configured as described above, it constitutes a part of the rear wheel steering link mechanism and is movable in the axial direction within the housing portion 4. A large gear 20 as a transmitted gear that receives rotational transmission as a rear wheel steering force from the small gear 12 via a ball screw mechanism 21 is mounted on a part of the supported rod body 2. 20 is rotatably supported in the housing part 4 (!l) by a bearing 22, and is formed along the axial direction in a part of the circumferential direction of the large diameter part 2a provided in a part of the rod body 2 in the axial direction. An engagement pin 25 as a rod rotation regulating means that can move forward and backward and is protruded from a direction perpendicular to the axial direction of the engagement groove 23 as an engagement portion can be driven by an electromagnetic solenoid 24. The engagement pin 25 is normally projected and engaged with the engagement groove 23 of the rod body 2, and the rotation is transmitted to the large gear 20, which is the transmitted gear, so that the rod body 2 is connected to the rod body 2 by the ball screw 8!11121. The rod body 2 is configured to be able to slide appropriately in the axial direction and in the left-right direction, and in the event of a failure, the engagement state of the rod body 2 with the engagement groove 23 is released by pulling out the engagement pin 25. It has certain characteristics.

Note that the engagement structure of the engagement pin 25 by the engagement groove 23 and the solenoid 24 described above is illustrated in FIG. 2(a), for example.
Although it is preferable to adopt a shape as shown in (b), the shape is not limited to this. In short, it is preferable to restrict the rotation of the rod body 2 and to allow it to move in the axial direction.

According to such a configuration, during normal operation, the engagement pin 25 serving as the rod rotation regulating means is connected to the engagement groove 23 of the rod body 2.
The rear wheel steering force is converted to the rod body 2 via the ball screw mechanism 21 by the large gear 20, which is a transmitted gear that receives rotation transmission, and is transmitted to the rod body 2 to achieve the required rear wheel rotation. In addition to performing rudder control, in the event of a failure such as runaway of the motor 11, the rod body 2 is made rotatable by disengaging the engagement pin 25,
As a result, even when the large gear 20 rotates, the rod body 2 also idles, thereby maintaining the non-steerable state of the rear wheels.

Therefore, according to such a configuration, when controlling the rear wheels, the required rear wheel steering force is properly and reliably transmitted when necessary, and the movement of the rod body 2 in the axial direction allows the rear wheels to be steered. The control can be performed in the required state, and on the other hand, in the event of a fail, by allowing the rotation of the rod body 2, the function of the ball screw mechanism 21 prevents rotation transmission, and the rear wheel is brought into a neutral state by a centering spring mechanism or the like. The steering wheel can be held and not steered, thereby improving the running stability and maneuverability of the vehicle.

Note that the present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part of the rear wheel steering device W1 may be modified and changed as appropriate. For example, in the embodiment described above, the electric power steering device 10 is used as a rear wheel steering system for steering the rear wheels.
However, the present invention is not limited to this, and any suitable actuator including a hydraulic cylinder etc. can be used as long as it is configured to generate rear wheel steering force. For example, an actuator equipped with a hydraulic power steering device can be used. It can be applied to even a rear wheel steering device with a similar effect, and in short, it only needs to be configured so that the rod body 2 can be moved in the axial direction using rotational power, and the arrangement position, etc. It goes without saying that the structure is not limited to the structure of the embodiment.

Furthermore, in the embodiment described above, in order to convert the rotation from the motor 11 into movement in the axial direction of the rod body 2, a large gear 20 as a transmitted gear is mounted on the rod body 2 via a ball screw mechanism 21. However, the present invention is not limited to this; for example, the transmission mechanism means may be a screw mechanism using a trapezoidal screw or the like, and the transmission means may also be a screw mechanism using a trapezoidal screw or the like. Needless to say, there is no limitation, and for example, a toothed belt or the like may be used.

〔Effect of the invention〕

As explained above, according to the rear wheel steering device for a four-wheel steering vehicle according to the present invention, the rear wheel steering device constitutes a part of the rear wheel steering link mechanism and is supported movably in the axial direction within the cylindrical housing. A rod body and a part in the axial direction of the rod body, such as a transmitted means that is rotatably supported within the housing and is rotatably supported within the housing through a screw mechanism, and transmits the rear wheel steering force as rotational power. The rod rotation regulating means is provided with a rod rotation regulating means that is movable forward and backward and is protruded so as to be able to engage from a direction perpendicular to the axial direction with respect to the engaging portion provided on the rod body. The rod body can be moved in the axial direction by a screw mechanism by engaging and transmitting rotation to the transmitted means, and the engagement with the rod body can be released in the event of a failure, making it simple and inexpensive. Despite this configuration, during normal operation, the rear wheel steering force is properly and reliably transmitted to the rod body to enable the required rear wheel steering control, and in the event of a failure such as motor runaway, the rod rotation is restricted. By releasing the engagement state by the means, the rod body is put in a rotatable state, and even if the transmitted means rotates, the rod body idles together with it, making it possible to maintain the unsteered state of the rear wheels. This has various excellent effects such as improving stability and maneuverability when the vehicle is running.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of the entire device showing an embodiment of the rear wheel steering device for a four-wheel steering vehicle according to the present invention, and FIGS. 2(a) and (b)
) is a schematic diagram illustrating a regulating means for regulating the rotation of the rod body. DESCRIPTION OF SYMBOLS 1... Rear wheel steering device, 2... Rod body, 4... Cylindrical housing part, 6... Centering spring,
10... Electric power steering device, 11... Electric motor, 12... Small gear, 20... Transmitted means (
Large gear), 21...Ball screw [2 @ side (screw mechanism)
, 23...Engagement groove (engaging portion), 24...Electromagnetic solenoid, 25...-Engagement pin rod rotation regulating means) 9 Patent applicant Jidosha Kiki Co., Ltd.

Claims (1)

[Claims] A rod body that constitutes a part of a steering link mechanism that supports the rear wheels in a steerable manner and is supported movably in the axial direction within a cylindrical housing, and a screw mechanism attached to a part of this rod body. a transmission means that is mounted on a shaft and is rotatably supported within the cylindrical housing to transmit rear wheel steering force as rotational power; The rod rotation regulating means is provided with a rod rotation regulating means that is protruded so as to be engageable from a direction orthogonal to the axial direction and is movable back and forth, and the rod rotation regulating means is normally engaged with the engaging portion of the rod body and The rod body is made movable in the axial direction by the screw mechanism by transmission of rotation to the means, and the rod body is configured to be disengaged from the engaging portion in the event of a failure. Rear wheel steering device for four-wheel steering vehicles.