JP5553105B2 - Electric power steering device - Google Patents

Description

  The electric power steering apparatus according to the present invention is used as a steering apparatus for an automobile, and reduces the force required for the driver to operate the steering wheel by using an electric motor as an auxiliary power source. It is. The present invention is a torque coupling portion provided at a connection portion between a base end portion of a worm shaft of a reduction gear constituting such an electric power steering device and a distal end portion of an output shaft of the electric motor. The present invention was invented to sufficiently suppress the generation of abnormal noise accompanying rattling over a long period of time.

  A power steering device is widely used as a device to reduce the force required for the driver to operate the steering wheel when giving a steering angle to the steered wheels (usually the front wheels except for special vehicles such as forklifts) Has been. In addition, an electric power steering apparatus that uses an electric motor as an auxiliary power source in such a power steering apparatus has begun to spread in recent years. Various structures of such an electric power steering apparatus are known, but in any structure, a rotating shaft that is rotated by the operation of the steering wheel and gives a steered angle to the steered wheels as it rotates. Auxiliary power of the electric motor is applied through a speed reducer. In general, a worm reducer is used as the reducer. In the case of an electric power steering device using a worm speed reducer, a worm that is rotationally driven by the electric motor and a worm wheel that rotates together with the rotating shaft are engaged with each other, and auxiliary power of the electric motor is applied to the rotating shaft. Communicate freely.

  For example, Patent Document 1 describes an electric power steering device as shown in FIGS. A front end portion of a steering shaft 2 that is a rotating shaft that is rotated in a predetermined direction by the steering wheel 1 is rotatably supported inside the housing 3, and the worm wheel 4 is fixed to this portion. A worm tooth 5 that meshes with the worm wheel 4 is provided at an axially intermediate portion of the worm shaft 6, and both ends of the worm 8 that is rotationally driven by the electric motor 7 are connected to a pair of rolling bearings 9 a such as a deep groove ball bearing, 9b is rotatably supported in the housing 3.

  In order to rotationally drive the worm 8 by the output shaft 10 of the electric motor 7, a spline hole 11 is formed in the proximal end portion of the worm shaft 6 so as to open to the proximal end surface of the worm shaft 6. A spline shaft 12 is formed at the tip of the output shaft 10. Then, the spline shaft portion 12 and the spline hole 11 are spline-engaged so that the output shaft 12 and the worm shaft 6 are freely coupled to transmit rotational force. The term “spline” used in this specification includes what is called “serration” with a fine pitch.

  Further, in the case of the conventional structure shown in FIG. 12, in order to eliminate backlash at the meshing portion between the worm wheel 4 and the worm tooth 5, the tip portion (the right end portion in FIG. 12) of the worm shaft 6 is connected to the worm wheel. The wheel 4 is elastically pressed toward the wheel 4. That is, the pressing piece 13 is externally fitted to a portion protruding from the leading end side rolling bearing 9 a at the tip of the worm shaft 6, and an elastic member such as a coil spring 14 is provided between the pressing piece 13 and the housing 3. Provided. The worm teeth 5 are pressed against the worm wheel 4 by the coil spring 14 via the pressing piece 13. With such a configuration, backlash between the worm teeth 5 and the worm wheel 4 is suppressed, and the teeth at the meshing portion of the worm wheel 4 and the worm teeth 5 are converted when the rotation direction of the electric motor 7 is changed. Suppressing the sound of hitting.

  By the way, in the case of the structure shown in FIG. 12 as described above, a torque joint portion between the output shaft 10 and the worm shaft 6, that is, a spline engaging portion between the spline hole 11 and the spline shaft portion 12, If the spline hole 11 and the spline shaft portion 12 can be spline-engaged without any circumferential clearance (without backlash), the spline engagement portion (torque joint portion) will have rattling in the rotational direction. Absent. However, in the actual case, a backlash exists in the spline engaging portion. The backlash of the spline engaging portion is necessary in order to facilitate the work of spline engaging the spline hole 11 and the spline shaft portion 12.

  Further, as long as the center axis of the output shaft 10 and the center axis of the worm shaft 6 are slightly shifted, it is necessary to rotate the output shaft 10 so that the spline engagement portion is not distorted. The backlash is also necessary to prevent the torque from increasing. In particular, a structure for eliminating backlash between the worm teeth 5 and the worm wheel 4 by pressing the worm teeth 5 provided on the worm shaft 6 against the worm wheel 4 by an elastic member such as the coil spring 14. In this case, it is essential to provide a backlash for the spline engaging portion. For such backlash, that is, the circumferential clearance, instead of the spline engaging portion as a torque joint portion, a torque joint portion of another mechanism such as a non-circular fitting portion such as an oval cross section is adopted. It is necessary in the same way.

  However, if backlash (circumferential clearance) exists in the spline engaging portion, that is, if there is a backlash in the rotational direction between the output shaft 10 and the worm shaft 6 (with the output shaft 10). If the worm shaft 6 can be relatively rotated relative to the worm shaft 6), there is a possibility that abnormal noise may be generated at the spline engaging portion based on this rattling. That is, for example, at the moment when the electric motor 7 starts to start or when the rotation direction is changed, the circumferential side surface of the male spline teeth provided on the outer peripheral surface of the spline shaft portion 12 and the spline hole 11 There is a possibility that an abnormal sound called a rattling noise may be generated by vigorously colliding with the circumferential side surface of the female spline teeth provided on the inner peripheral surface.

  Such a rattling noise becomes more significant as the backlash (rattle, relative rotation) of the spline engaging portion increases. Conventionally, this backlash can be assembled into the spline engaging portion. In such a range, further, the backlash between the worm teeth 5 and the worm wheel 4 can be eliminated, and the range is reduced. However, if the backlash of the spline engaging portion is reduced, the spline shaft portion 12 is less likely to be inserted into the spline hole 11, the assembly workability is reduced, and the manufacturing cost of the electric power steering device is increased. Cause. Further, unless the accuracy of assembly between the output shaft 10 and the worm shaft 6 is increased, the problem of torque increase due to the galling is likely to occur, which also causes an increase in manufacturing cost of the electric power steering apparatus.

  For example, a structure described in Patent Document 2 is known as a technique for preventing the rattling noise (shaking in the rotation direction) as described above. In the case of the structure described in Patent Document 2, an elastic member is provided at the torque joint portion of the output shaft and the worm shaft, and the ratchet sound (rotation) is generated at the torque joint portion based on the elastic force of the elastic member. (Shaking of direction) is prevented from occurring. However, in the case of the structure described in Patent Document 2, torque is transmitted between the output shaft and the worm shaft through the elastic member. For this reason, the torque is always applied to the elastic member during torque transmission, and the elastic member cannot apply the desired elastic force with long-term use (the initial elastic force cannot be applied over a long period of time) It may be easier). If the desired elastic force cannot be applied in this manner, the above-mentioned rattling noise (shaking in the rotational direction) cannot be sufficiently prevented, which is not preferable.

  On the other hand, Patent Document 3 describes a structure for preventing the output shaft of the electric motor and the worm shaft from shaking in the axial direction in order to stabilize the operation of the electric power steering device as described above. Has been. That is, in the case of the structure described in Patent Document 3, the O-ring is sandwiched between the output shaft and the worm shaft in an elastically compressed state. Then, the output shaft and the worm shaft are given elastic forces in directions away from each other to prevent the output shaft and the worm shaft from rattling in the axial direction. However, in the case of such a structure described in Patent Document 3, it is intended to prevent the generation of abnormal noise (tooth rattling sound) accompanying backlash in the rotational direction as described above. Not.

  That is, in the case of the structure described in Patent Document 3, the O-ring is sandwiched between the output shaft and the worm shaft while being compressed in the axial direction as described above, and the elastic force in the axial direction is held by this O-ring. Is granted. In the case of a structure in which the O-ring is clamped in the axially compressed state in this way, almost no resistance force in the rotational direction is obtained, or even if it is obtained, it becomes unstable based on the frictional force. Therefore, in the structure in which the O-ring is incorporated as described in Patent Document 3, the generation of abnormal noise (tooth rattling sound) accompanying backlash in the rotational direction as described above is generated for a long time. It cannot be prevented stably.

JP 2004-306898 A JP 2006-177505 A JP 2002-255047 A

  In view of the circumstances as described above, the present invention is a torque joint portion for transmitting torque between the output shaft of the electric motor and the worm of the worm speed reducer, while ensuring a necessary clearance (backlash), The present invention has been invented to realize a structure that can sufficiently prevent the generation of abnormal noise (tooth rattling sound) due to the rattling (relative rotation) in the rotational direction due to the existence of this gap over a long period of time.

The electric power steering device of the present invention is similar to the electric power steering device described in the above-mentioned Patent Document 1 or the like and has been conventionally known, for example, a housing, a rotating shaft, a worm wheel, a worm, An electric motor and a torque coupling part are provided.
Of these, the housing is supported by fixed parts such as the steering column and the case of the steering gear unit and does not rotate.
The rotating shaft is rotatably provided with respect to the housing, and is rotated by an operation of a steering wheel, and gives a steering angle to the steered wheels in accordance with the rotation. As such a rotating shaft, when the fixed portion is the steering column, a steering shaft or a shaft provided coaxially with the steering shaft is used when the fixed portion is a case of a steering gear unit. Corresponds to the pinion axis.
The worm wheel is supported on a part of the rotating shaft inside the housing, concentrically with the rotating shaft, and rotates together with the rotating shaft.

The worm is formed by providing a worm tooth at an intermediate portion in the axial direction of the worm shaft. With the worm tooth meshed with the worm wheel, the axial end portion of the worm shaft is formed by a rolling bearing to form the housing. Is supported in a freely rotatable manner.
The electric motor is for rotationally driving the worm.
The torque coupling portion is provided between the distal end portion of the output shaft of the electric motor and the proximal end portion of the worm, and enables transmission of torque from the output shaft to the worm. It is comprised by a joint receiving hole and a joint axial part.
Among these, the joint receiving hole is opened at the axial end surface of one of the output shaft and the worm, and the cross-sectional shape of the inner peripheral surface is non-circular.
Further, the joint shaft portion is an end portion of the other member of the output shaft and the worm, and an outer peripheral surface for engaging the inner peripheral surface of the joint receiving hole with a joint so as to allow torque transmission. The cross-sectional shape is non-circular.
Various shapes can be adopted as long as the cross-sectional shapes of the joint receiving hole and the joint shaft portion are non-circular, such as a chip shape, an oval shape, a polygonal shape, etc. And a spline hole and a spline shaft portion, respectively.

In particular, in the electric power steering apparatus of the present invention , a recess is provided in the end surface of the joint shaft portion so as to be recessed from the end surface.
Further, the joint radially inward of the engaging portion and the rolling bearing of the joint receiving hole and the joint shaft portion, these joints receiving hole, in a state that is superimposed on the joint shaft and the rolling bearing and the radial direction and these Compressed in the axial direction between the back end surface of the joint receiving hole and the bottom surface of the concave portion of the joint shaft, and engaged with the joint receiving hole and the joint shaft in a manner that prevents relative displacement in the rotational direction. in, for example nitrile rubber, provided silicone rubber, urethane rubber, rubber such as acrylic rubber, or such as polyurethane elastomers, the elastic member made of an elastic material such as synthetic resin.
By such an elastic member, a force in a direction away from each other in the axial direction and a resistance force (torsional rigidity) against relative rotation are applied between the output shaft and the worm. In order to apply such a force, for example, the axial dimension of the elastic member in the free state is set to be larger than the interval between the opposing surfaces in contact with both axial end surfaces of the elastic member in the assembled state. Enlarge.

Further, when carrying out the invention of the electric power steering apparatus of the present invention, preferably, as in the invention described in claim 2, a cylindrical member having a noncircular cross-sectional shape on the outer peripheral surface is provided. The joint shaft portion is configured by being externally fitted and fixed to the output shaft or the end portion of the worm. And the said recessed part is comprised by the internal peripheral surface of this cylindrical member, and the said output shaft or the end surface of a worm.

When the electric power steering apparatus according to the present invention is implemented, for example , as in the third aspect of the present invention, it is disengaged in the axial direction from the joint engaging portion between the joint receiving hole and the joint shaft portion. For example, a second elastic member made of an elastic material such as rubber such as nitrile rubber, silicon rubber, urethane rubber, or acrylic rubber, elastomer such as polyurethane, or synthetic resin is provided at the position. And, such a second elastic member is provided on the output shaft side protruding portion provided on the output shaft (including a member rotating with the output shaft) and on the worm side provided on the worm (including a member rotating with the worm). In a state of being engaged with the protrusions and elastically deforming in a direction to apply a resistance force (torsional rigidity) against relative rotation between the output shaft and the worm based on the engagement. Provide.

Further, when the invention of the electric power steering apparatus described in claim 3 is carried out, preferably, the output shaft (including a member that rotates together with the output shaft is included ) as in the invention described in claim 4. ) Is provided with at least one (more preferably, a plurality of) output shaft side protrusions. At the same time, at least one (more preferably a plurality of) worm side protrusions are provided on the worm (including a member that rotates together with the worm). Then, the second elastic member is disposed between the output shaft side protruding portion and the worm side protruding portion, and the second elastic member, the output shaft side protruding portion, and the worm side protruding portion have a diameter of the output shaft. Provided in a state of overlapping in the direction.
Preferably, as in the invention described in claim 5 , the output shaft side protrusion is integrally provided on the output shaft (including a member that rotates together with the output shaft), and the worm side protrusion is Provided integrally with the worm (including a member that rotates together with the worm).
Preferably, as in the invention described in claim 6 , a part in the radial direction of the output shaft side protruding part and a part in the radial direction of the worm side protruding part are overlapped in the circumferential direction. .

According to the electric power steering device of the present invention as described above, the torque joint portion secures a necessary gap (backlash), and the rotation in the rotational direction caused by the existence of the gap (relative rotation). ) Can be sufficiently prevented over a long period of time.
That is, in the case of the present invention, the elastic member provided in an axially compressed state between the output shaft of the electric motor and the worm shaft causes the elastic force in the direction away from each other between the output shaft and the worm shaft. A resistance force (torsional rigidity) against relative rotation is also applied while applying a force (elastic force in the axial direction). Therefore, based on this resistance force (torsional rigidity), at the moment when the electric motor starts to start or at the moment when the rotation direction is changed, the torque joint between the output shaft and the worm shaft Torque transmission surfaces can be prevented from colliding vigorously (momentum can be dulled). In addition, since the elastic member is provided on the radially inner side of the joint engaging portion between the joint receiving hole and the joint shaft portion so as to overlap the joint receiving hole and the joint shaft portion in the radial direction, Torque can be transmitted based on the direct engagement (contact) between the joint receiving hole and the joint shaft portion (the torque is not transmitted via the elastic member). For this reason, regardless of the use over a long period of time, the elastic member can always provide the desired elastic force (the initial elastic force can be applied over a long period of time and can be difficult to sag). As a result, while ensuring the necessary gap (backlash) at the torque joint part, the generation of abnormal noise (tooth rattling sound) due to rattling (relative rotation) in the rotational direction due to the existence of this gap. It can be sufficiently prevented over a long period of time.

In the case of the invention described in claim 3 , the second shaft provided in a state of being engaged with the output shaft side protruding portion provided on the output shaft of the electric motor and the worm side protruding portion provided on the worm, respectively. A resistance force (torsional rigidity) against relative rotation is applied between the output shaft and the worm by the elastic member. Therefore, based on this resistance force (torsional rigidity), at the moment when the electric motor starts to start or at the moment when the rotation direction is changed, the torque joint between the output shaft and the worm shaft Torque transmission surfaces can be prevented from colliding vigorously (momentum can be dulled). In addition, since the second elastic member is provided at a position that is axially disengaged from the joint engaging portion between the joint receiving hole and the joint shaft portion, direct engagement between the joint receiving hole and the joint shaft portion is achieved. Torque can be transmitted based on (contact) (the torque is not transmitted via the second elastic member). For this reason, regardless of the use over a long period of time, the desired elastic force can always be imparted by the second elastic member (the initial elastic force can be imparted over a long period of time, making it difficult to sag). As a result, while ensuring the necessary gap (backlash) at the torque joint part, the generation of abnormal noise (tooth rattling sound) due to rattling (relative rotation) in the rotational direction due to the existence of this gap. It can be sufficiently prevented over a long period of time.

The partial cutting side view which shows the 1st example of the reference example regarding this invention. The fragmentary sectional view seen from the same direction as Drawing 1 showing the state where the 2nd elastic member is assembled between a worm and an output shaft. The figure which took out the 2nd elastic member and was seen from the left of FIG. The figure similar to FIG. 3 which shows the 2nd example of the reference example regarding this invention. The partial cutting side view which shows the 3rd example. The fragmentary sectional view seen from the same direction as Drawing 5 showing the state where the 2nd elastic member is assembled between a worm and an output shaft. Similarly a partial enlarged perspective view. The figure which took out the 2nd elastic member and was seen from the left of FIG. The partial cutting side view which shows one example of embodiment of this invention. The A section enlarged view of FIG. The partially cut side view which shows an example of a prior art structure. The expanded BB sectional drawing of FIG.

[First example of reference example of the present invention]
1-3 have shown the 1st example of the reference example regarding this invention. The electric power steering apparatus according to this embodiment is characterized by a spline engagement between a spline hole 11 opened at the base end surface of the worm shaft 6 and a spline shaft portion 12 formed at the distal end portion of the output shaft 10 of the electric motor 7. In this structure, a gap (backlash) between parts is secured, and the generation of noise (tooth rattling sound) due to the rattling (relative rotation) in the rotational direction due to the existence of the gap is prevented. In addition, since the structure and operation of the entire electric power steering apparatus are the same as those of the conventional structure described above, illustrations and explanations regarding the same parts as the conventional structure are omitted or simplified. The description will focus on the characteristic part. 11 to 12 and FIG. 1 are different in the mounting direction of the electric motor 7 with respect to the housing 3, but this point is appropriately changed in design according to the vehicle to be installed. It has nothing to do with the features of the invention.

  In the case of this reference example, a spline hole 11 corresponding to the joint receiving hole described in the claims is opened at the base end portion of the worm shaft 6 in a state where the spline hole 11 is opened at the base end surface of the worm shaft 6. It is formed concentrically with the shaft 6. Further, a spline shaft portion 12 which is a joint shaft portion described in the claims is formed concentrically with the output shaft 10 at the tip portion of the output shaft 10 of the electric motor 7. Then, the spline shaft portion 12 and the spline hole 11 are engaged with each other by spline engagement which is a joint engagement described in the claims, whereby the output shaft 10 and the worm shaft 6 are transmitted with rotational force. Is possible to combine. A gap (backlash) is interposed in the spline engagement portion between the spline shaft portion 12 and the spline hole 11 so that the spline engagement between the spline hole 11 and the spline shaft portion 12 can be easily performed. In addition, the central axis of the worm shaft 6 can be allowed to be slightly inclined with respect to the central axis of the output shaft 10.

  Further, in the case of the present reference example, the rolling bearing is provided on the outer peripheral surface of the base end portion of the worm shaft 6 at a portion protruding to the base end side in the axial direction from the rolling bearing 9b that rotatably supports the worm shaft 6. A holding member 16 is externally fixed to prevent the inner ring 15 constituting 9b from coming out of the worm shaft 6. And it is in the state which protrudes toward the axial direction one side from this one side surface to the axial direction one side surface (the right side surface of FIG. 1, 2 and the surface on the opposite side to the spline hole 11) of this holding member 16, and circumference. A plurality of (three in the illustrated example) worm-side protrusions 17 and 17 are provided integrally with the holding member 16 in a state of being equally spaced with respect to the direction.

  Further, at the distal end portion of the output shaft 10, it protrudes radially outward from the outer peripheral surface of the output shaft 10 to the proximal end side with respect to the spline shaft portion 12, and at equal intervals in the circumferential direction. A plurality (three in the illustrated example) of output shaft side protrusions 18 and 18 are provided integrally with the output shaft 10 in a separated state. That is, in the case of this reference example, the output shaft side protrusions 18 and 18 and the worm side protrusions 17 and 17 are positioned in the axial direction away from the spline shaft portion 12 and the spline hole 11. Provided. The second elastic member 19 is connected between the output shaft side protrusions 18 and 18 and the worm side protrusions 17 and 17, the second elastic member 19 and the output shaft side protrusion 18, 18 and the worm side protrusions 17 and 17 are provided so as to overlap with the radial direction of the output shaft 10 (however, at a position deviated in the circumferential direction for each of the protrusions 18 and 17).

  In the case of this reference example, the second elastic member 19 has an oil resistance selected from rubbers such as nitrile rubber, silicon rubber, urethane rubber, and acrylic rubber, elastomers such as polyurethane, and synthetic resins. The whole is made into an annular shape (substantially cylindrical) by the elastic material, and has elasticity that can expand and contract at least in the circumferential direction. And the outer diameter side engaging recessed part engaged with each said worm | warm side protrusion part 17 and 17 in the state which is dented in radial direction inward from this outer peripheral surface to the outer peripheral surface of such a 2nd elastic member 19 20 and 20 are provided. Similarly, the inner diameter side engagement of the second elastic member 19 is engaged with the output shaft side protrusions 18 and 18 while being recessed radially outward from the inner peripheral surface. Recesses 21 and 21 are provided.

  The inner diameter side engaging recesses 21 and 21 are engaged with the output shaft side protruding portions 18 and 18 of the output shaft 10 and the outer diameter side engaging recesses 20 and 20 are The second elastic member 19 is assembled between the output shaft 10 and the worm shaft 6 while being engaged with the worm-side protrusions 17 and 17 of the holding member 16 fixedly coupled to the worm shaft 6. ing. Further, in this assembled state, the second elastic member 19 is based on the engagement between the outer diameter side and inner diameter side engaging recesses 20 and 21 and the worm side and output shaft side protrusions 17 and 18. Are elastically deformed in a direction in which a resistance force to relative rotation is applied between the output shaft 10 and the worm 8 (the protrusions 17 and 18 are press-fitted into the engagement recesses 20 and 21). Yes. Therefore, in the case of this reference example, the distance between the inner side surfaces of the inner and outer diameter side engaging recesses 20 and 21 in the circumferential direction in the free state of the second elastic member 19. Is made larger than the distance between the side surfaces in the circumferential direction of the protrusions 17 and 18 on the worm side and the output shaft side. The spline shaft portion 12 and the spline hole 11 are engaged with the projections 17 and 18 on the worm side and the output shaft side and the engagement recesses 20 and 21 on the inner diameter side and the outer diameter side. A resistance to relative rotation (in both directions) is applied between the output shaft 10 and the worm 8 so that the relationship is in a neutral state (a state where backlash of the same size exists on both sides in the rotational direction). Like.

In the case of such an electric power steering device of this reference example, a spline is formed by a spline hole 11 opened in the base end surface of the worm shaft 6 and a spline shaft portion 12 formed at the distal end portion of the output shaft 10 of the electric motor 7. While ensuring the necessary gap (backlash) at the engaging part, the generation of abnormal noise (tooth rattling sound) due to the rattling (relative rotation) in the rotation direction due to the existence of this gap over a long period of time It can be prevented sufficiently.
In other words, in the case of this reference example, the output shaft side protrusions 18 and 18 provided on the output shaft 10 and the worm 8 (the holding member 16 coupled to the base end portion of the worm shaft 6 constituting the fixing member 16) are provided. The second elastic member 19 provided in a state of being engaged with each of the worm side protrusions 17 and 17 provides a resistance force (torsional rigidity) against relative rotation between the output shaft 10 and the worm 8. Give. For this reason, on the basis of this resistance force (torsional rigidity), at the moment when the electric motor 7 is started or when the rotation direction is changed, the torque coupling portion (between the output shaft 10 and the worm shaft 6 ( The spline engagement portion) can prevent the torque transmitting surfaces from colliding with each other (the momentum can be dulled).

  Moreover, since the second elastic member 19 is provided at a position axially disengaged from the spline engaging portion between the spline hole 11 and the spline shaft portion 12, the spline hole 11 and the spline shaft portion 12 Torque can be transmitted based on the direct engagement (direct contact between the side surfaces of the spline teeth). That is, at the moment from the neutral state until the side surfaces of the spline teeth come into contact with each other, the second elastic member 19 is elastically deformed and very little torque is transmitted. The torque can be prevented from being transmitted through the elastic member 19 (except for the portion corresponding to this very small amount of torque). For this reason, the desired elastic force can always be imparted by the second elastic member 19 regardless of the use over a long period of time (the initial elastic force can be imparted over a long period of time, and it is difficult to sag). As a result, while the necessary clearance (backlash) is secured in the spline engaging portion, abnormal noise (tooth rattling noise) due to rattling (relative rotation) in the rotational direction due to the presence of this clearance is generated. Can be sufficiently prevented over a long period of time.

  In addition, in the case of this reference example, the second elastic member 19 is connected to the output shaft 10 from the base end portion of the worm shaft 6, which is a portion having a space (particularly radial space). Since the second elastic member 19 is disposed in a close portion (a portion adjacent to the holding member 16 fixedly coupled to the base end portion of the worm shaft 6), the second elastic member 19 has a large size (large volume, radial size). Large size) can be easily incorporated, and the elastic force by the second elastic member 19 can be easily secured. Further, the output shaft side protrusions 18 and 18 are provided integrally with the output shaft 10, and the worm side protrusions 17 and 17 are provided integrally with a holding member 16 coupled and fixed to the base end portion of the worm shaft 6. Therefore, the manufacturing cost can be reduced by reducing the number of parts.

[Second Example of Reference Example of the Present Invention]
FIG. 4 shows a second example of a reference example relating to the present invention. In the case of the first example of the reference example described above, the number of the outer diameter side engaging recesses 20 and 20 and the inner diameter side engaging recesses 21 and 21 (the worm side protruding portions 17 and 17 and the output shaft side protruding portion 18, In the case of the present reference example, the number is different. That is, in the case of the present reference example, the inner diameter side engaging recesses 21a and 21a are provided at two positions on the radially opposite side of the inner circumferential surface of the elastic member 19a, and four circumferentially equally spaced positions on the outer circumferential surface are also provided. Are provided with respective outer diameter side engaging recesses 20a, 20a. Correspondingly, the worm side protrusions 17 and 17 are arranged at four circumferentially equidistant positions on one side of the holding member 16 coupled and fixed to the base end portion of the worm shaft 6, and the intermediate portion outer peripheral surface of the output shaft 10. Output shaft side protrusions 18 and 18 (see FIGS. 1 and 2) are provided at two positions opposite to the radial direction, respectively.
Since the configuration and operation of other parts are the same as those in the first example of the reference example described above, overlapping illustrations and descriptions are omitted.

[Third example of reference example of the present invention]
FIGS. 5-8 has shown the 3rd example of the reference example regarding this invention. In the case of this reference example, the cylindrical member 22 is fitted and fixed to the distal end portion of the output shaft 10, and output shaft side protruding portions 18 a and 18 a are provided at the proximal end portion of the cylindrical member 22. In the case of the present reference example, each worm provided on one side surface of the holding member 16 coupled and fixed to a part of the radial direction of each of the output shaft side protruding portions 18a and 18a and the proximal end portion of the worm shaft 6 is used. A part of the side protrusions 17a, 17a in the radial direction is overlapped in the circumferential direction.

  In the case of this reference example, the portion between the inner diameter side engaging recesses 21b, 21b and the outer diameter side engaging recesses 20b, 20b in the circumferential direction of the second elastic member 19b is Compressed in the circumferential direction by the side surfaces of the output shaft side protrusions 18a and 18a and the side surfaces of the worm side protrusions 17a and 17a (a compressive load is applied to the portion indicated by the diagonal grid in FIG. 8). ). For this reason, for example, as shown in FIG. 3 described above, a part in the radial direction of each output shaft side protrusion 18, 18 and a part in the radial direction of each worm side protrusion 17, 17 are circumferential. As in the case of a structure that does not overlap with each other, a shearing force (arrows α, α in FIG. 3) is applied to a portion between each inner diameter side engagement recess 21, 21 and each outer diameter side engagement recess 20, 20. Can be prevented. For this reason, compared with the structure shown in FIG. 3 as described above, the durability and elastic force of the second elastic member 19b can be more easily ensured.

Further, in the case of this reference example, at the base end portion of the cylindrical member 22, the base end side rather than the portion where the output shaft side projecting portions 18 a, 18 a are provided, over the entire circumference, outward in the radial direction. The flange portion 25 is provided in a protruding state. The second elastic member 19b is compressed in the axial direction by the side surface of the flange portion 25 and the side surface of the restraining member 16 that face each other. In the case of this reference example, an elastic force (an axial elastic force) in a direction away from each other can be applied between the output shaft 10 of the electric motor 7 and the worm shaft 6. For this reason, it is possible to prevent the output shaft 10 and the worm shaft 6 from rattling in the axial direction, and to more reliably prevent the generation of abnormal noise at the spline engaging portion.
Since the configuration and operation of other parts are the same as those of the first and second examples of the reference example described above, overlapping illustrations and descriptions are omitted.

[Example of Embodiment]
9 to 10 show an example of an embodiment of the present invention corresponding to claims 1 to 6. FIG. In the case of the third example of the reference example described above, the second elastic member 19b is provided only at the proximal end portion of the cylindrical member 22 that is externally fitted and fixed to the distal end portion of the output shaft 10 (see, for example, FIG. 5). . On the other hand, in the case of this example, in addition to the second elastic member 19b, in addition to the second elastic member 19b, it corresponds to the elastic member described in claim 1 of the claims. The first elastic member 23 is provided. That is, in the case of this example, the spline hole 11 and the spline shaft portion 12 are overlapped with the spline hole 11 and the spline shaft portion 12 in the radial direction inside the spline engagement portion, and this The first elastic member 23 is provided in a state compressed in the axial direction by the back end surface of the spline hole 11 and the bottom surface of the recess 24 provided on the inner diameter side of the spline shaft portion 12 (tip surface of the output shaft 10). ing. The first elastic member 23 is made of an elastic material having oil resistance, which is selected from rubbers such as nitrile rubber, silicon rubber, urethane rubber and acrylic rubber, elastomers such as polyurethane, and synthetic resins. Is made in the shape of a solid cylinder, and has elasticity that allows the axial dimension to be expanded and contracted. Such a first elastic member 23 provides a force in a direction away from each other in the axial direction and a resistance force against relative rotation between the output shaft 10 and the worm 8.

  For this reason, in the case of this example, the concave portion 24 is provided in the end surface of the spline shaft portion 12 so as to be recessed from the end surface. In order to form such a recess 24, in this example, a cylindrical member 22 having the spline shaft portion 12 formed on the outer peripheral surface thereof is externally fitted and fixed to the tip end portion of the output shaft 10. The recess 24 is formed by the inner peripheral surface of the cylindrical member 22 and the tip surface of the output shaft 10. The first elastic member 23 is compressed in the axial direction between the bottom surface of the recess 24 (the front end surface of the output shaft 10) and the back end surface of the spline hole 11. In order to provide the first elastic member 23 in a compressed state in the axial direction in this way, in this example, the axial dimension in the free state of the first elastic member 23 is set in the assembled state. The distance between the back end surface of the spline hole 11 and the bottom surface of the recess 24 (the front end surface of the output shaft 10) is larger.

  Also, in this assembled state, both side surfaces of the first elastic member 23 in the axial direction are over the entire surface, and the back end surface of the spline hole 11 and the bottom surface of the recess 24 (tip surface of the output shaft 10). , Each is in contact. It is also preferable that the outer peripheral surface of the end of the first elastic member on the output shaft 10 side is in contact with the inner surface (inner peripheral surface) of the recess 24 over the entire circumference. In addition, when the relationship between the spline shaft portion 12 and the spline hole 11 is in a neutral state (a state in which there is a backlash of the same size on both sides in the rotational direction), the first elastic member 23 is also in a neutral state (not twisted). ). Such a first elastic member 23 causes a force in a direction away in the axial direction between the output shaft 10 provided with the spline shaft portion 12 and the worm shaft 6 provided with the spline hole 11. And resistance to relative rotation.

  If necessary, among the back end surface of the spline hole 11, the inner surface or bottom surface of the recess 24 (tip surface of the output shaft 10), and the axial end surface or outer peripheral surface of the first elastic member 23. At least one of the surfaces is roughened to increase the coefficient of static friction. And by roughening in this way, the axial side surface of the first elastic member 23 and the mating surface {the back end surface of the spline hole 11, the inner surface and the bottom surface of the recess 24 (the front end surface of the output shaft 10)} are mutually connected. It prevents slipping and prevents the reduction or loss of the resistance (torsional rigidity) associated with the slipping. In addition, the axially opposite side surfaces or outer peripheral surfaces of the first elastic member 23 are rotated in the rotational direction on the back end surface of the spline hole 11 and the inner surface or bottom surface of the concave portion 24 (the front end surface of the output shaft 10). It is also possible to engage in a state where the relative displacement is prevented. For this purpose, for example, the axial side surface or outer peripheral surface of the first elastic member 23 and the mating surface {the back end surface of the spline hole 11, the inner surface or the bottom surface of the recess 24 (the front end surface of the output shaft 10)} are engaged with each other. By providing a free, non-circular or eccentric concave portion and a convex portion separately and engaging the concave portion with the convex portion, the relative displacement in the rotational direction can be prevented. If necessary, the first elastic member 23 is bonded, for example, to at least one of the back end surface of the spline hole 11 and the inner surface or the bottom surface of the recess 24 (the front end surface of the output shaft 10). It is also possible to bond the parts inseparably by seizure.

In any case, in the case of the electric power steering device of this example, the spline hole 11 opened in the base end surface of the worm shaft 6 and the spline shaft portion 12 formed at the distal end portion of the output shaft 10 of the electric motor 7. While securing the necessary gap (backlash) at the spline engaging part, the generation of abnormal noise (tooth rattling noise) due to the rattling (relative rotation) in the rotational direction due to the existence of this gap is long-lasting. It is possible to prevent it enough.
That is, in the case of this example, this output is provided by the first elastic member 23 provided between the back end surface of the spline hole 11 and the bottom surface of the recess 24 which is the tip surface of the output shaft 10 of the electric motor 7. A resistance force (torsional rigidity) against relative rotation can be applied between the shaft 10 and the worm shaft 6 while applying an elastic force in a direction away from each other (axial elastic force). For this reason, on the basis of this resistance force (torsional rigidity), at the moment when the electric motor 7 is started or when the rotation direction is changed, the torque coupling portion (between the output shaft 10 and the worm shaft 6 ( The spline engagement portion) can prevent the torque transmitting surfaces from colliding with each other (the momentum can be dulled).

  In addition, the first elastic member 23 is provided on the radially inner side of the spline engagement portion between the spline hole 11 and the spline shaft portion 12 so as to overlap the spline hole 11 and the spline shaft portion 12 in the radial direction. Therefore, torque can be transmitted based on the direct engagement between the spline hole 11 and the spline shaft portion 12 (direct contact between the side surfaces of the spline teeth). That is, at the moment from the neutral state until the side surfaces of the spline teeth come into contact with each other, the first elastic member 23 is elastically deformed and very little torque is transmitted. The torque can be prevented from being transmitted through the elastic member 23 (except for the portion responsible for the extremely small torque). For this reason, regardless of the use over a long period of time, the first elastic member 23 can always provide the desired elastic force (the initial elastic force can be applied over a long period of time and can be difficult to sag). As a result, while the necessary clearance (backlash) is secured in the spline engaging portion, abnormal noise (tooth rattling noise) due to rattling (relative rotation) in the rotational direction due to the presence of this clearance is generated. Can be sufficiently prevented over a long period of time.

In the case of this example, the first elastic member 23 is provided on the radially inner side of the spline hole 11 and the spline shaft portion 12 so as to overlap the spline hole 11 and the spline shaft portion 12 in the radial direction. Therefore, it is possible to secure a portion for incorporating the first elastic member 23 without increasing the axial dimension of the entire apparatus. In addition, it is possible to easily incorporate the first elastic member 23 having a large axial dimension. In the case of this example, the cylindrical member 22 having the spline shaft portion 12 is fitted and fixed to the distal end portion of the output shaft 10 to thereby form a recess 24 for assembling the first elastic member 23. Since it is configured, the forming operation of the recess 24 can be easily performed. That is, the machining can be performed easily and the manufacturing cost can be reduced as compared with the case where the recess 24 is formed by drilling the tip surface of the output shaft 10. Moreover, even if the depth of the spline hole 11 is not increased (without increasing the depth more than necessary), a portion for incorporating the first elastic member 23 can be secured. I can plan. In addition, the depth of the spline hole 11 (the position of the back end surface) can be regulated with high accuracy because the depth of the spline hole 11 does not need to be increased. For this reason, the dimension (dimension in the compressed state) of the first elastic member 23 in the assembled state can be accurately regulated, and the axial elastic force and the resistance force applied by the first elastic member 23 are predetermined. It can be easily regulated to the value of. For this reason, generation | occurrence | production of the noise (tooth rattling sound) accompanying the shakiness (relative rotation) of a rotation direction can be prevented more reliably.

In the case of this example, two elastic members, the second elastic member 19b and the first elastic member 23, are provided. However, the second elastic member 19b is omitted, and resistance to relative rotation between the output shaft 10 of the electric motor 7 and the worm shaft 6 is based on the elastic force of only the first elastic member 23. Force (torsional rigidity) can also be applied.
Since the configuration and operation of the other parts are the same as in the first to third examples of the reference example described above, overlapping illustrations and descriptions are omitted.

  It should be noted that although both the above-described embodiment and the reference example are provided with the spline hole 11 on the worm 6 side and the spline shaft portion 12 on the output shaft 10 side, they can be reversed. . That is, although not shown, a spline shaft portion can be provided on the worm side and a spline hole can be provided on the output shaft side.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Housing 4 Worm wheel 5 Worm tooth 6 Worm shaft 7 Electric motor 8 Worm 9a, 9b Rolling bearing 10 Output shaft 11 Spline hole 12 Spline shaft part 13 Pressing piece 14 Coil spring 15 Inner ring 16 Holding member 17, 17a Worm side protruding portion 18, 18a Output shaft side protruding portion 19, 19a, 19b Second elastic member 20, 20a, 20b Outer diameter side engaging concave portion 21, 21a, 21b Inner diameter side engaging concave portion 22 Cylindrical member 23 First Elastic member 24 concave part 25 collar part

Claims (6)

A housing that is supported by a fixed part and does not rotate;
A rotating shaft provided rotatably with respect to the housing, rotated by an operation of a steering wheel, and giving a steering angle to a steered wheel in accordance with the rotation;
A worm wheel that is supported concentrically with the rotating shaft and rotates together with the rotating shaft inside a part of the rotating shaft inside the housing;
A worm tooth is provided in the middle part of the worm shaft in the axial direction, and the worm tooth is meshed with the worm wheel, and the end of the worm shaft in the axial direction is rotatably supported with respect to the housing by a rolling bearing. Warm and
An electric motor for rotationally driving the worm,
A torque coupling portion provided between the distal end portion of the output shaft of the electric motor and the proximal end portion of the worm and capable of transmitting torque from the output shaft to the worm;
The torque joint portion includes a joint receiving hole that is open on an axial end surface of one of the output shaft and the worm and has a noncircular cross-sectional shape on the inner peripheral surface, the output shaft, and the worm. Of the other member of the joint, and the joint peripheral portion of the joint receiving hole and the joint shaft portion having a non-circular cross-sectional shape on the outer peripheral surface that engages with the joint so as to allow torque transmission In the electric power steering device,
A concave portion is provided on the end surface of the joint shaft portion so as to be recessed from the end surface.
Radially inside the joint engaging portion and the rolling bearing of the joint receiving hole and the joint shaft portion, these joints receiving hole, in a state that is superimposed on the joint shaft and the rolling bearing and the radial direction and these joints receiving While compressing in the axial direction between the back end surface of the hole and the bottom surface of the concave portion of the joint shaft portion, the joint receiving hole and the joint shaft portion are engaged in a manner that prevents relative displacement in the rotational direction , An elastic member made of an elastic material is provided,
An electric power steering apparatus characterized in that a force in a direction away from each other in the axial direction and a resistance force against relative rotation are applied between the output shaft and the worm by the elastic member. A cylindrical member whose outer peripheral surface has a non-circular cross-section is fitted and fixed to the end of the output shaft or worm to form a joint shaft, and the inner peripheral surface of the cylindrical member and the output shaft or worm Constructed a recess with the end face,
The electric power steering apparatus according to claim 1 . The second elastic member is disposed at a position that is axially disengaged from the joint engaging portion between the joint receiving hole and the joint shaft portion, and the output shaft side projecting portion provided on the output shaft and the worm side projecting portion provided on the worm, respectively. in a state where the engaged and, based on this engagement, it is provided in a state in which the resistance to relative rotation and is elastically deformed in a direction to impart between the output shaft and the worm, according to claim 1 to 2 The electric power steering apparatus described in any one of the above. The output shaft is provided with at least one output shaft side protruding portion, the worm is provided with at least one worm side protruding portion, and a second elastic member is provided between the output shaft side protruding portion and the worm side protruding portion. The second elastic member, the output shaft side protruding portion, and the worm side protruding portion are provided in a state of overlapping in the radial direction of the output shaft.
The electric power steering apparatus according to claim 3 . The output shaft side protrusion is provided integrally with the output shaft, and the worm side protrusion is provided integrally with the worm.
The electric power steering apparatus according to any one of claims 3 to 4 . A part in the radial direction of the output shaft side protrusion and a part in the radial direction of the worm side protrusion are overlapped in the circumferential direction.
The electric power steering apparatus according to any one of claims 3 to 5 .

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