In a motor-driven steering apparatus structured such that a motor-driven steering assist unit is interposed between a steering shaft in a handle side and a wheel side steering member, and an input shaft connected to the steering shaft of the motor-driven steering assist unit and an output shaft connected to the wheel side steering member are coupled by a torsion bar and arranged on the same center axis, reference angle position marks are applied to portions existing at the same angle position around the same center axis of the input shaft and the output shaft, in a neutral steering state in which a steering force is not applied to the input shaft of the motor-driven steering assist unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a motor-driven steering apparatus.

2. Description of the Related Art

For a motor-driven steering apparatus for a saddle riding type vehicle such as a buggy vehicle or the like, there has been a structure in which a motor-driven steering assist unit is interposed between a steering shaft of a handle side and a wheel side steering member, as described in Japanese Patent Application Laid-open No. 2004-231011 (patent document 1). The structure is made such that a steering force applied to the handle by a driver is assisted by a generated torque of an electric motor.

A conventional motor-driven steering apparatus is structured such that a steering shaft in a handle side is attached to a position at a proper mounting angle with respect to an input shaft of a motor-driven steering assist unit, a wheel side steering member is attached to a position of a proper mounting angle with respect to an output shaft, and a motor-driven steering assist unit is thereafter attached to a vehicle body frame. At this time, if the mounting position of the motor-driven steering assist unit with respect to the vehicle body frame is deviated, a torsion bar coupling an input shaft and an output shaft of the motor-driven steering assist unit is ineffectively twisted, and it is impossible to set the mounting position of the handle to a proper neutral position.

However, in the prior art, the mounting position of the motor-driven steering assist unit with respect to the vehicle body frame is shifted from a correct position at a mounting state of the motor-driven steering assist unit to the vehicle body frame, and it is impossible to easily discriminate whether or not the torsion bar coupling the input shaft and the output shaft of the motor-driven steering assist unit is twisted ineffectively. Even if it is found after an assembly of the vehicle is finished that the actual mounting position of the handle is deviated from the proper neutral position, it is hard to correct the deviation because of the other auxiliary machines attached to the vehicle body frame.

SUMMARY OF THE INVENTION

An object of the present invention is to easily discriminate whether or not a mounting position of a motor-driven steering assist unit with respect to a vehicle body frame is deviated from a correct position in a mounting stage of the motor-driven steering assist unit to the vehicle frame, and a torsion bar coupling an input shaft and an output shaft of the motor-driven steering assist unit is twisted ineffectively.

The present invention relates to a motor-driven steering apparatus structured such that a motor-driven steering assist unit is interposed between a steering shaft in a handle side and a wheel side steering member, and an input shaft connected to the steering shaft of the motor-driven steering assist unit and an output shaft connected to the wheel side steering member are coupled by a torsion bar and arranged on the same center axis. Reference angle position marks are applied to portions existing at the same angle position around the same center axis of the input shaft and the output shaft, in a neutral steering state in which a steering force is not applied to the input shaft of the motor-driven steering assist unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A saddle riding type vehicle100inFIG. 1is used as a rough road traveling vehicle such as a four-wheeler, buggy vehicle, snowmobile or the like, and has a motor-driven steering apparatus1. The motor-driven steering apparatus1is structured such that a handle stay3provided with a bar handle2serving as a steering handle is fixed to a steering shaft4in the manner mentioned below, and a motor-driven steering assist unit10is interposed between the steering shaft4and a tire wheel side steering member5.

The motor-driven steering apparatus1is structured, as shown inFIG. 2, such that the steering shaft4is rotatably supported to a support member6A of an upper vehicle body side stay6via a bearing. The tire wheel side steering member5is rotatably supported to a support member7A of a lower vehicle body side stay7via a bearing, and a pitman arm8A is fixed to an intermediate portion thereof. The pitman arm8A is coupled to right and left front wheels9via right and left tie rods8. The upper and lower vehicle body side stays6and7are supported to a vehicle body frame.

The motor-driven steering assist unit10is structured by a single unit body10A covered by first housing11(upper housing or upper cover), second housing (main housing), and third housing (lower housing or lower cover)13, as shown inFIGS. 2 and 3. The unit body10A has an input shaft21, an output shaft22, a torque sensor23, an electric motor24, a worm gear25and a worm wheel26built-in.

The motor-driven steering assist unit10is structured such that an upper end portion of the input shaft21to which the steering shaft4is connected by a connecting device4A is supported to the first housing11(FIG. 3) by the bearing31. Upper and lower end portions of the output shaft22to which the tire wheel side steering member5is connected by a connecting device5A are supported to the second housing12and the third housing13by upper and lower bearings32A and32B (not shown). The input shaft21is provided with a serration21A for connection to the connecting device4A in an upper end outer peripheral portion. The output shaft22is provided with a serration22A for connecting to the connecting device5A in a lower end outer peripheral portion. A torsion bar27is inserted to a hollow portion of the input shaft21. One end of the torsion bar27is coupled to the input shaft21by serration, and the other end of the torsion bar27is inserted in a hollow portion of the output shaft22so as to be connected by a coupling pin27A. The motor-driven steering assist unit10is structured such that the input shaft21connected to the steering shaft4and the output shaft22connected to the wheel side steering member5are coupled by the torsion bar27so as to be coaxially arranged.

A torque sensor23is provided with two detecting coils23A and23B surrounding a cylindrical core23C engaged with the input shaft21and the output shaft22, in the first housing11, as shown inFIG. 3. The core23C is provided with a vertical groove23E engaging with a guide pin23D of the output shaft22so as to be movable only in an axial direction, and is provided with a spiral groove23G engaging with a slider pin23F of the input shaft21. Accordingly, when a steering torque applied to the steering wheel is applied to the input shaft21, and a relative displacement in a rotation direction is generated between the input shaft21and the output shaft22on the basis of an elastic torsional deformation of the torsion bar27, the displacement in the rotation direction of the input shaft21and the output shaft22displaces the core23C in an axial direction. An inductance of the detecting coils23A and23B caused by a magnetic change around the detecting coils23A and23B due to the displacement of the core23C is changed. In other words, when the core23C moves close to the input shaft21, the inductance of the detecting coil23A to which the core23C moves close is increased, and the inductance of the detecting coil23B from which the core23C moves apart is reduced, whereby it is possible to detect the steering torque on the basis of the change of the inductance.

The electric motor24is attached and supported to the second housing12by a mounting bolt28, and is driven by a controller (not shown) in correspondence to the detected torque of the torque sensor23. A worm gear25is coupled to a rotation shaft of the electric motor24by a joint, and the worm wheel26engaging with the worm gear25is fixed to the output shaft22. The worm gear25is supported at both ends to the second housing12by right and left bearings (not shown). The worm wheel26is fixed to the output shaft22just below an upper bearing32A in the output shaft22, in an inner portion of the second housing12.

Accordingly, in the motor-driven steering assist unit10, an integral unit body10A is structured by supporting the upper end portion of the input shaft21and the torque sensor23to the first housing11. The upper end portion of the output shaft22, the electric motor24, the worm gear25and the worm wheel26are supported by the second housing12. The lower end portion of the output shaft22is supported by the third housing13. The first housing11and the second housing12are coupled by the mounting bolt14, and the second housing12and the third housing13are coupled by the mounting bolt15. An oil seal33is attached in a sealing manner to an upper opening portion of the bearing31in the first housing11, and an oil seal34is attached in a sealing manner to a lower opening portion of the bearing32B in the third housing13.

Further, the motor-driven steering assist unit10is structured such that the second housing12can be attached to the vehicle body side. The motor-driven steering assist unit10is structured, as shown inFIG. 2, such that elastic members51and52such as a rubber bush or the like are provided in both sides of attaching bosses12A provided at a plurality of positions, for example, three positions, in a peripheral direction of an outer periphery of the second housing12. The attaching bosses12A are pinched between upper and lower support pieces of forked support portions18provided at a plurality of positions corresponding to the attaching bosses12A of the vehicle body side attaching stay17via the elastic members51and52. The attaching boss12A is pinched in a floating fixed state between the upper and lower support pieces via the elastic members51and52by the support pieces of the forked support portion18, the elastic members51and52, and an attaching bolt16(a nut) inserted and attached to a bolt hole provided in each of the attaching bosses12A. The vehicle body side bracket17is supported to the vehicle body frame.

In the motor-driven steering apparatus1, the steering torque applied to the bar handle2is detected by the torque sensor23, the electric motor24is driven on the basis of the detected torque, and the torque generated by the electric motor24is transmitted to the output shaft22via the worm gear25and the worm wheel26. Accordingly, the torque generated by the electric motor24can be used as an assist force for the steering force which the driver applies to the bar handle2.

Accordingly, in the motor-driven steering apparatus1, as shown inFIG. 3, reference angle marks21B and22B are applied to portions at the same angular positions around the same center axis of the input shaft21and the output shaft22, in a neutral steering state (a free state) in which the steering force is not applied to the input shaft21of the motor-driven steering assist unit10. The reference angle position mark21B of the input shaft21corresponds to one differentiated or snaggly tooth portion formed in the serration21A of the input shaft21, as shown inFIG. 4. The reference angle position mark22B of the output shaft22corresponds to one differentiated or snaggly tooth portion formed in the serration22A of the output shaft22, as shown inFIG. 5. In a front view of the neutral steering state (the free state) shown inFIG. 3of the motor-driven steeling assist unit10, the reference angle position mark21B of the input shaft21and the reference angle position mark22B of the output shaft22are positioned on the same line along the same center axis of the input shaft21and the output shaft22.

A description will be given below of a mounting procedure of the motor-driven steering apparatus1.

(1) The steering shaft4in the handle2side is attached to the proper mounting angle position with respect to the input shaft21of the motor-driven steering assist unit10. The wheel side steering member5is attached to the proper mounting angle position with respect to the output shaft22of the motor-driven steering assist unit10. At this time, the motor-driven steering apparatus1can position the steering shaft4, and the bar handle2by extension to the proper neutral position.

(2) The motor-driven steering apparatus1mentioned above (1) is attached to the vehicle body frame (the upper end lower vehicle body side stays6and7, and the vehicle body side bracket17). In other words, the steering shaft4is attached to the upper vehicle body side stay6, the wheel side steering member5is attached to the lower vehicle body side stay7, and the motor-driven steering assist unit10is attached to the vehicle body side bracket17.

(3) In the mounting stage of the motor-driven steering apparatus1mentioned above (2) to the vehicle body frame, the reference angle position mark21B of the input shaft21and the reference angle position mark22B of the output shaft22are set such that their angle positions are identical with each other around the same center axis. It is checked on the basis of a visual observation by a worker or a measured result by a measuring device.

Therefore, in accordance with the present embodiment, the following operations and effects can be obtained.

(a) In the neutral steering state in which the steering force is not applied to the input shaft21of the motor-driven steering assist unit10, the reference angle position marks21B and22B are attached to the positions existing at the same angle position around the same center axis of the input shaft21and the output shaft22. Accordingly, it may be recognized on the basis of the visual observation by the worker or the measured result by the measuring device that the reference angle position mark21B of the input shaft21and the reference angle position mark22B are different from each other in their angle positions around the same center axis. This may occur in the stage in which the steering shaft4in the bar handle2side is attached to the proper mounting angle position with respect to the input shaft21of the motor-driven steering assist unit10, the wheel side steering member5is attached to the proper mounting angle position with respect to the output shaft22, and the motor-driven steering assist unit10is thereafter attached to the vehicle body frame. It is possible to discriminate that an inadequacy exists in the mounted state of the motor-driven steering assist unit10to the vehicle body frame, and an application of an unnecessary external force exists between the input shaft21and the output shaft22. In other words, it may be determined that the mounted position of the motor-driven steering assist unit10to the vehicle body frame is deviated from the correct position. In the case mentioned above, it is possible to immediately correct the deviation of the mounted position of the motor-driven steering assist unit10to the vehicle body frame in its mounting stage. In accordance with this structure, it is possible to set the actual mounted position of the bar handle2to the proper neutral position in the stage in which the assembly of the vehicle is finished.

(b) It is possible to easily form the reference angle position mark21B of the input shaft21and the reference angle position mark22B of the output shaft22mentioned in the item (a) by the differentiated or snaggly tooth portions formed in the serrations21A and22A.

(c) The laterally extending length of the bar handle2is long. Accordingly, when the mounted position of the motor-driven steering assist unit10to the vehicle body frame is deviated from the correct position, and the torsion bar coupling the input shaft21and the output shaft22of the motor-driven steering assist unit10is twisted ineffectively, the deviation of the mounted position of the bar handle2from the correct neutral position is enlarged by both end grip portions so as to be distinguished. In the present invention, it is possible to set the actual mounted position of the bar handle2to the proper neutral position.

(d) In the saddle riding type vehicle100, it is possible to advantageously achieve the items (a) to (c) mentioned above.

As heretofore explained, embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configurations of the present invention are not limited to the illustrated embodiments but those having a modification of the design within the range of the presently claimed invention are also included in the present invention. For example, in the present invention, the reference angle position mark of the input shaft and the reference angle position mark of the output shaft may be constituted by a paint mark, an engraved mark or the like.

Although the invention has been illustrated and described with respect to several exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made to the present invention without departing from the spirit and scope thereof. Therefore, the present invention should not be understood as limited to the specific embodiment set out above, but should be understood to include all possible embodiments which can be encompassed within a scope of equivalents thereof with respect to the features set out in the appended claims.