JP5157666B2 - Elastic shaft coupling and electric power steering device - Google Patents

Description

  Of the elastic shaft coupling and the electric power steering apparatus that are the subject of the present invention, the electric power steering apparatus is used as a steering apparatus for an automobile. By using an electric motor as an auxiliary power source, the driver can This is intended to reduce the force required to operate the steering wheel. In addition, the elastic shaft coupling is incorporated in the torque transmission part between the output shaft of the electric motor constituting such an electric power steering device and the worm shaft of the speed reducer, for example, to prevent the driver from feeling uncomfortable during steering. However, the auxiliary power is transmitted from the output shaft to the worm shaft.

  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. Also, in such a power steering device, an electric power steering device using an electric motor as an auxiliary power source has been widely implemented. 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. However, in the case of a worm reducer, if no measures are taken, it is called a rattling sound when changing the rotation direction of the rotating shaft based on the backlash existing in the meshing portion of the worm and the worm wheel. Unpleasant noise may occur.

Conventionally, as described in Patent Documents 1 to 3, it is considered that the worm is elastically pressed toward the worm wheel by an elastic member such as a spring as a structure that can suppress the generation of such rattling noise. ing. 5 to 6 show an example of the electric power steering apparatus described in Patent Document 2 among them. 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. Worm teeth 5 meshing with the worm wheel 4 are provided in the axial direction intermediate portion of the worm shaft 6, and both ends of the worm 8 driven to rotate by the electric motor 7 are paired with a pair of rolling bearings 9 a such as a deep groove ball bearing, 9b is rotatably supported in the housing 3. Further, a pressing piece 10 is externally fitted to a portion protruding from the rolling bearing 9 a at the tip of the worm shaft 6, and an elastic member such as a coil spring 11 is provided between the pressing piece 10 and the housing 3. ing. The coil spring 11 presses the worm teeth 5 provided on the worm shaft 6 toward the worm wheel 4 through the pressing piece 10. With such a configuration, backlash between the worm teeth 5 and the worm wheel 4 is suppressed, and generation of the rattling noise is suppressed.

  In the case of the conventional structure as described above, it is possible to suppress the occurrence of the rattling noise at the meshing portion between the worm tooth 5 and the worm wheel 4, but the tip of the output shaft 12 of the electric motor 7 and the worm The rattling noise generated at the joint with the base end of the shaft 6 cannot be suppressed. This point will be described below. A spline hole 13 is formed in the base end portion of the worm shaft 6 so that the tip end portion of the output shaft 12 of the electric motor 7 and the base end portion of the worm shaft 6 can be freely transmitted. It forms in the state opened to the base end surface of the axis | shaft 6. FIG. A spline shaft portion 14 is formed at the tip of the output shaft 12. The spline shaft portion 14 and the spline hole 13 are spline-engaged so that the output shaft 12 and the worm shaft 6 are freely coupled to transmit rotational force.

  If the spline shaft portion 14 and the spline hole 13 are in spline engagement with no circumferential clearance (without backlash), the distal end portion of the output shaft 12 and the proximal end portion of the worm shaft 6 No rattling noise is generated at the coupling part (spline engaging part). However, in the actual case, a backlash exists in the spline engaging portion. In the case of a simple spline engaging portion, a large torque suddenly starts to be transmitted from the output shaft 12 to the worm shaft 6 with the start of energization of the electric motor 7. For this reason, immediately after the operation of the steering wheel 1 is started, the force required to operate the steering wheel 1 suddenly decreases. Such a situation is not preferable because it gives the driver an uncomfortable feeling.

In particular, as shown in FIG. 6 described above, the worm shaft 6 is provided on the worm shaft 6 by an elastic member such as the coil spring 11 in order to eliminate backlash existing in the meshing portion between the worm 8 and the worm wheel 4. In the case of a structure in which the worm teeth 5 are pressed against the worm wheel 4, it is essential to connect the base end portion of the worm shaft 6 to the tip end portion of the output shaft 12 in a swingable manner. For this reason, in the case where the coupling portion is formed by simple spline engagement, the backlash of the spline engagement portion must be increased, and the above problem is likely to become remarkable.

  Instead of the spline engaging portion that causes such inconvenience, an elastic shaft coupling that transmits torque via an elastic member to the torque transmitting portion between the distal end portion of the output shaft 12 and the proximal end portion of the worm shaft 6. Can be considered. Patent Documents 4 and 5 describe elastic shaft couplings that can be incorporated between the distal end portion of the output shaft 12 of the electric motor 7 constituting the electric power steering device and the proximal end portion of the worm shaft 6. It has been known. In any of the elastic shaft couplings described in Patent Documents 4 and 5, torque can be elastically deformed between ends of a pair of rotating shafts arranged in series with each other in the axial direction. It transmits via an elastic member.

  For this purpose, the conventional elastic shaft coupling includes first and second transmission members and an elastic member. Both of these transmission members are supported concentrically with the two rotation shafts at the ends of the two rotation shafts. Further, a plurality of first and second members projecting in the axial direction toward the mating rotating shaft intermittently with respect to the rotating direction on the surface facing the mating rotating shaft of the two transmission members. Each protrusion is provided. And the said elastic member is clamped between the circumferential direction side surfaces of each 1st, 2nd protrusion part. In the case of the conventional structure described in Patent Document 4, the elastic member is tuned to the elastic deformation state by forming a through hole in a part of the elastic member in the axial direction of the two rotating shafts. doing. Further, in the case of the conventional structure described in Patent Document 5, the elastic deformation state of the elastic member is tuned by changing the compression state of the elastic member by the first and second protrusions in two stages. doing.

  However, in the case of the conventional structures described in Patent Documents 4 and 5, when the elasticity of the elastic member deteriorates (has) with use over a long period of time, the elastic member is placed near the neutral position. A dead zone (a range in which torque transmission is not performed at all) in which a buffer action cannot be obtained occurs. In such a state, a driver or the like who operates the steering wheel is uncomfortable. In particular, in the case of the conventional structure described in Patent Document 5, a part of the elastic member is compressed from the initial stage of torque transmission that transmits a small torque, and when this part transmits a large torque, Further, since the amount of compression is increased, it is considered that a part of the elastic member is easily deteriorated and the dead zone is easily generated. In addition, the conventional structures described in Patent Documents 4 and 5 are not structures that positively allow so-called misalignment in which the central axes of a pair of rotating shafts do not coincide with each other. When becomes larger, there is a possibility that torque transmission between the two rotating shafts cannot be performed smoothly. In particular, the base end portion of the worm shaft 6 is swingably coupled to the distal end portion of the output shaft 12 in order to eliminate the backlash existing in the meshing portion between the worm 8 and the worm wheel 4 as described above. In the case of a structure, the above-mentioned misalignment inevitably occurs, so that the above problem is likely to be remarkable. Further, in the case of the conventional structure described in Patent Document 4, since the elastic member is not integral, parts management and assembly work become troublesome.

JP 2000-43739 A JP 2004-306898 A JP-T-2006-513906 JP 2002-206564 A JP 2004-148990 A

  In view of the circumstances as described above, the present invention has good transient characteristics at the start of torque transmission, the elastic member is not easily deteriorated, and when this elastic member is deteriorated, no dead zone is generated, and the parts management, The invention was invented to realize an elastic shaft coupling and an electric power steering device that can be easily assembled.

Of the elastic shaft coupling and the electric power steering apparatus of the present invention, the invention of the elastic shaft coupling described in claim 1 is an elastic shaft coupling known from the past, for example, as described in Patent Documents 4 and 5. Similarly, torque is transmitted between ends of a pair of rotating shafts arranged in series with respect to the axial direction via elastic members that are elastically deformable with respect to the direction of the torque.
For this purpose, the elastic shaft coupling of the present invention includes both first and second transmission members and an elastic member.
The first transmission member is supported at the end of one of the two rotating shafts concentrically with the one rotating shaft, and the other rotating shaft of the two rotating shafts. A plurality of first projecting portions that project intermittently in the axial direction toward the other rotational axis are provided on the surface facing each other intermittently in the rotational direction.
The second transmission member is supported at the end of the other rotation shaft concentrically with the other rotation shaft, and intermittently with respect to the rotation direction on the surface facing the one rotation shaft. A plurality of second projecting portions projecting in the axial direction toward the one rotating shaft are provided.
Further, the elastic member is sandwiched between the circumferential side surface of each of the second projecting portions and the circumferential side surface of each of the first projecting portions.

In particular, in the elastic shaft coupling according to the present invention, the elastic member includes a plurality of sandwiched between a circumferential side surface of each of the first protrusions and a circumferential side surface of each of the second protrusions. The elastic deformation portions are integrally joined to each other. Each of these elastic deformation portions is composed of a pair of compression deformation portions and bending deformation portions.
Among these, the pair of compression deforming portions are opposed to each other through the gap with respect to the torque transmission direction, and can be elastically compressed with respect to the rotation directions of the two rotation shafts.
Further, the bending deformation portion connects the ends of the both compression deformation portions with respect to the radial direction of the two rotation shafts, and the bending amount is elastically corresponding to the change in the interval between the both compression deformation portions. It will change.

Further, in the case of the present invention, the elastic deformation portions are formed by bending the inner end edges of the pair of compression deformation portions each having a plate shape in the radial direction of the two rotation shafts into a partial cylindrical shape. The cross-section is V-shaped, which is formed by connecting the parts. Further, the outer peripheral edges of the compression deformation portions of the elastic deformation portions adjacent to each other in the circumferential direction in the radial direction of the two rotation shafts are connected to the first and second protrusions in the radial direction of the two rotation shafts. They are connected to each other by an outer diameter side connecting portion existing outside.
Furthermore, in the case of the present invention, among the compression deformation portions constituting the elastic deformation portions, the surfaces facing the compression deformation portions constituting the elastic deformation portions adjacent to each other in the rotation direction of the two rotation shafts An intermediate portion in the radial direction of both rotation shafts is a convex curved surface that protrudes most in the rotation direction.

When implementing the present invention as described above, preferably, as in the invention described in claim 2 , for example, the thickness dimension of the bending deformation portion constituting each elastic deformation portion is set to a pair of compression deformations. The thickness should be smaller than the thickness of the part. And a recessed part is provided inside in the bending direction of this bending deformation part .

On the other hand, among the elastic shaft coupling and the electric power steering device of the present invention, the invention of the electric power steering device according to claim 3 includes a housing, a rotating shaft, a worm wheel, a worm, an electric motor, A coupling device.
Of these, the housing is supported by a fixed portion and does not rotate.
The rotating shaft is provided so as to be rotatable with respect to the housing, and is rotated by an operation of a steering wheel, and gives a steering angle to the steered wheels as it rotates.
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 worm teeth at the axial intermediate portion of the worm shaft, and in the state where the worm teeth are engaged with the worm wheel, both end portions in the axial direction of the worm shaft are respectively attached to the housing by bearings. On the other hand, it is supported rotatably.
The electric motor is for rotationally driving the worm.
Furthermore, the joint device is provided between the distal end portion of the output shaft of the electric motor and the proximal end portion of the worm shaft, and transmits torque between the two shafts. The elastic shaft coupling of the present invention.
When the invention of the electric power steering apparatus described in claim 3 is carried out, preferably, as in the invention described in claim 4 , the tip portion of the worm shaft and the housing are An elastic member for pressing the worm teeth toward the worm wheel is provided.

According to the elastic shaft coupling and the electric power steering device of the present invention configured as described above, the transient characteristics at the start of torque transmission are good, the elastic member is not easily deteriorated, and even when the elastic member is deteriorated. Dead zones do not occur, and parts management and assembly work become easy.
First, it is difficult for the elastic member to be deteriorated and the transient characteristics at the start of torque transmission are good. Each elastic deformation portion constituting the elastic member is divided into a pair of compression deformation portion and bending deformation portion, respectively. It can be achieved by configuring. When torque transmission is started between a pair of rotating shafts, first, the curvature of the bending deformation portion of each elastic deformation portion changes. That is, when torque is transmitted between the two rotating shafts, the first and second projecting portions provided on the first and second transmitting members are located between the circumferential side surfaces of the first and second projecting portions. The width in the circumferential direction of the gap portion where each elastic deformation portion is arranged changes. Specifically, among these gaps, the width of half of the gaps existing every other gap is reduced, and the width of the remaining half of the gaps is increased. And each elastic deformation part arrange | positioned in the gap part with which the curvature of the bending deformation part which comprises each elastic deformation part arrange | positioned in the clearance part with which width | variety became small becomes large (a curvature radius is small), and became wide. The curvature of the bending deformation part which comprises is small (the curvature radius is large).

  Regardless of the direction in which the curvature changes (both larger and smaller), each of the bending deformation portions generates elasticity to return to the original (neutral) state. And based on this elasticity, a torque is transmitted between both said rotating shafts. The force required to change the curvature of each bending deformation part, in other words, the torque that can be transmitted by changing the curvature of these bending deformation parts is small, so immediately after the torque transmission between the two rotating shafts starts. There is no sudden start of large torque transmission. Therefore, when the elastic shaft coupling is incorporated in the electric power steering apparatus, it is possible to prevent the driver operating the steering wheel from feeling uncomfortable (transient characteristics are improved). Even after a certain amount of time has elapsed after the torque transmission is started, while the torque transmitted between the two rotating shafts is small, this torque can be changed by changing the curvature of each bending deformation portion. To communicate.

On the other hand, when the torque transmitted between the rotating shafts increases after the torque transmission is started, the elastic deforming portion disposed in the gap portion having a reduced width is formed among the elastic deforming portions. One pair of compression deforming portions contact each other. And after each these compression deformation parts contact | abut, among each torque which transmits between the said both rotating shafts, each said compression deformation part is a part which cannot be transmitted by each said bending deformation part. It transmits while elastically deforming in the compression direction. In this way, when a relatively large torque is transmitted after a certain amount of time has elapsed after the torque transmission is started, the amount of deformation of each of the bending deformation portions does not become very large (the compression of each compression deformation portion). Just stop to meet the amount). For this reason, even when a large torque is transmitted, it is possible to prevent the amount of deformation of each of the bending deformation portions provided for transmitting a small torque from being excessive, thereby preventing deterioration of the elastic member.
In particular, in the case of the present invention, since the circumferential side surface of the compression deformation portion constituting each elastic deformation portion is a convex curved surface, it is possible to increase the buffering effect related to torque fluctuations, and to achieve the above-described elasticity when large torque fluctuations occur. The maximum value of the stress generated inside the deformed portion can be kept low, and the durability of the elastic member can be easily ensured.

  Next, in order to prevent the dead zone from occurring even when the elastic member deteriorates, the bending deformation parts constituting the elastic deformation parts are between the bending deformation parts adjacent in the circumferential direction. This can be achieved by elastically deforming in the opposite direction. That is, when a bending deformation part constituting a certain elastic deformation part elastically deforms in a direction in which the curvature increases, the bending deformation part constituting the elastic deformation part adjacent to the elastic deformation part in the circumferential direction is: Elastically deforms in the direction of decreasing curvature. Since the force generated by the elastic deformation of each bending deformation part is applied to the direction in which the phase with respect to the rotation direction of the pair of rotation shafts becomes neutral, torque is transmitted between the rotation shafts. A buffering action is exerted with respect to, preventing the start of torque transmission from becoming abrupt and improving the transient characteristics at the start of torque transmission. When the elastic member is deteriorated, the buffering action may be reduced but not lost. Therefore, the dead zone does not occur even if the transient characteristics are somewhat deteriorated.

  Furthermore, the ease of parts management and assembling work can be achieved by integrally connecting the elastic deforming portions constituting the elastic member. That is, since the elastic members constituting the elastic shaft coupling can be handled as one body, it is possible to reduce the labor of component management. Also, the work of assembling the elastic member between the two rotating shafts becomes easy.

[First example of reference example of the present invention ]
1 and 2 show a first example of a reference example related to the present invention . In the case of the present embodiment includes a distal end portion of the output shaft 12a of the electric motor 7 constituting the electric power steering apparatus, between the base end portion of the worm shaft 6a constituting the worm reducer, the present reference example The elastic shaft coupling 15 is provided. The torque from the output shaft 12a to the worm shaft 6a is in a state of having a buffering action at the time of starting (a state in which transient characteristics are improved so that torque transmission is not suddenly started when the electric motor 7 is started) ). In order to provide the elastic shaft joint 15, a driving side serration portion 16 is provided at the distal end portion of the output shaft 12a, and a driven side serration portion 17 is provided at the proximal end portion of the worm shaft 6a. Since the configuration and operation of the electric power steering apparatus excluding the elastic shaft joint 15 are the same as those of the conventionally known electric power steering apparatus including the structure shown in FIGS. The description will be omitted, and the configuration and operation of the elastic shaft coupling 15 will be described below. In the following description, the radial direction, the circumferential direction, and the axial direction refer to the radial direction, the circumferential direction, and the axial direction of the elastic shaft coupling 15 (constituting members).

  The elastic shaft coupling 15 includes a drive-side transmission member 18 corresponding to the first transmission member described in the claims, and a driven-side transmission member 19 corresponding to the second transmission member. Of these, the drive-side transmission member 18 has drive-side arm portions respectively from a plurality of radial locations (three locations in the circumferential direction at equal intervals in the circumferential direction) on the outer peripheral surface of the cylindrical drive-side boss portion 20 provided at the center. 21 and 21 are extended in the radial direction. Drive side protrusions 22 and 22 corresponding to the first protrusions described in the claims are formed on one side surface in the axial direction of each of the drive side arm portions 21 and 21 so as to protrude in the axial direction. Yes. The width dimensions of the drive-side protrusions 22 and 22 in the circumferential direction are small in the radial direction and large in the radial direction. That is, when viewed from the axial direction, the end face shape of each of the drive side protrusions 22 and 22 is a sector shape whose width becomes narrower inward in the radial direction. A drive-side female serration that engages with the drive-side serration portion 16 is formed on the inner peripheral surface of the drive-side boss portion 20.

  On the other hand, the driven-side transmission member 19 uses a member having the same shape as the driving-side transmission member 18 in a state of being inverted with respect to the axial direction. That is, the driven side transmission member 19 includes a driven side boss portion 23 having the same shape as the driving side boss portion 20 and driven side arm portions 24 and 24 having the same shape as the driving side arm portions 21 and 21. And driven side protrusions 25, 25 corresponding to the second protrusions described in the claims. A driven-side female serration that engages with the driven-side serration portion 17 is formed on the inner peripheral surface of the driven-side boss portion 23.

Each having such a structure described above, the above drive-side transmission member 18 and the driven side transmission member 19, as shown in FIGS. 1-2, in combination through the elastic member 26, the elastic of the present embodiment A shaft coupling 15 is used. This elastic member 26 is integrally formed by injection molding an elastic material such as rubber, elastomer such as vinyl, or synthetic resin, and each of the driving side protrusions 22 constituting the driving side transmission member 18, The number of elastic deformation portions 27, which is a multiple of 22 (same as the multiple of each of the driven-side protrusions 25, 25 constituting the driven-side transmission member 19 and six in the case of this reference example ), 27 are connected to each other by outer diameter side connecting portions 28, 28. Each of these elastic deformation portions 27, 27 includes a pair of compression deformation portions 29, 29 and a bending deformation portion 30. Among these, each compression deformation part 29 and 29 is a wedge plate shape, respectively, and the thickness regarding the circumferential direction becomes large, so that it goes to radial direction outer side.

  On the other hand, the bending deformation portion 30 has a partial cylindrical shape, and connects the radially inner ends of the pair of compression deformation portions 29 and 29 as described above. The thickness of the bending deformation portion 30 is smaller than the thickness of the radially inner end portions of the compression deformation portions 29 and 29. Further, the side surfaces on the opposite sides of the circumferential side surfaces of the compression deformation portions 29, 29 and the bending direction outer surface (convex surface on the radial inner side) of the bending deformation portion 30 are smoothly and continuously connected. ing. Therefore, a concave portion 31 is formed on the inner side surface in the bending direction of the bending deformation portion 30 (a concave surface on the outer side in the radial direction) so as to be recessed from the opposite side surfaces of the compression deformation portions 29 and 29. . With the above configuration, each of the elastic deformation portions 27 and 27 has a V shape when viewed from the axial direction of the elastic member 26. Further, in the neutral state of each elastic deformation part 27, 27 (free state where no external force is applied), as shown in FIG. Parallel or slightly inclined in the direction in which the mutual distance increases toward the outside in the radial direction. In short, the direction of the mutually opposing side surfaces of the compression deformation portions 29, 29 in the neutral state is the diameter direction centered on the central axis of the elastic shaft coupling 15 (in a state excluding manufacturing errors and assembly errors). It is substantially matched.

  The outer diameter side connecting portions 28, 28 respectively connect the radially outer edges of the compression deformable portions 29, 29 constituting the elastic deformable portions 27, 27 adjacent to each other in the circumferential direction. Yes. Each of the outer diameter side coupling portions 28, 28 exists in a single virtual cylindrical space having the central axis of the elastic shaft coupling 15 as the central axis. In addition, the inner diameter of the virtual cylindrical space is larger than the diameter of the circumscribed circle of the driving side and driven side projections 22 and 25.

  The elastic member 26 having the above-described configuration is combined with the drive-side and driven-side transmission members 18 and 19 each having the above-described configuration to form the elastic shaft joint 15. That is, as shown in FIG. 1 and FIG. 2A, the drive-side protrusions constituting the transmission members 18 and 19 are arranged inside the elastic deformation portions 27 and 27 constituting the elastic member 26, respectively. The parts 22 and 22 and the driven side protrusions 25 and 25 are alternately fitted in the circumferential direction. Thus, in the neutral state in which the elastic shaft coupling 15 is configured by combining the members 18, 19, and 26, as shown in FIG. 2A, the elastic deformation portions 27 adjacent in the circumferential direction are provided. , 27 are in a state of being separated from each other. Since the elastic member 26 is an integral product, the combination of the members 18, 19, 26 can be easily performed.

  Such an elastic shaft joint 15 includes the driving side boss portion 20 of the driving side transmission member 18 as the driving side serration portion 16 of the output shaft 12a and the driven side boss portion 23 of the driven side transmission member 19 as described above. The worm shaft 6a is assembled between the output shaft 12a and the worm shaft 6a by being externally fitted to the driven serration portions 17 of the worm shaft 6a. In this state, when the output shaft 12a is rotated based on energization to the electric motor 7, the drive-side protrusions 22 and 22 constituting the drive-side transmission member 18 are replaced with the elastic deformation portions 27, 27, it is displaced in the rotational direction inside (three) elastic deformation portions 27, 27 that are present every other circumferential direction. Accordingly, the compression deformation portions 29 and 29 existing on the front side in the rotation direction are pushed in the circumferential direction, and at the same time, the compression deformation portions 29 and 29 existing on the rear side in the rotation direction are pulled in the circumferential direction.

  And each said bending deformation part 30 and 30 which exists in the inner diameter side edge part of each said elastic deformation part 27 and 27 elastically deforms in the direction which changes each curvature. Specifically, the curvatures of the bending deformation parts 30 and 30 existing on the front side in the rotation direction of the drive side protrusions 22 and 22 are increased, and the curvatures of the bending deformation parts 30 and 30 existing on the rear side are the same. Get smaller. In this process, torque is transmitted from the drive-side protrusions 22 and 22 to the driven-side protrusions 25 and 25 based on the elasticity with which the bending deformation parts 30 and 30 return. That is, the bending deformation portions 30 and 30 having increased curvatures press the driven-side protruding portions 25 and 25 in the circumferential direction, and the bending deformation portions 30 and 30 having decreased curvature are The driven side protrusions 25 and 25 are pulled in the circumferential direction. As a result, immediately after the output shaft 12a is started, and when the torque transmitted between the output shaft 12a and the worm shaft 6a is small, based on the elastic deformation of the bending deformation portions 30 and 30, This torque is transmitted.

When a certain amount of time (actually very short time) has elapsed after the output shaft 12a is started and the torque transmitted between the output shaft 12a and the worm shaft 6a increases, ), The curvatures of the bending deformation portions 30 and 30 existing on the front side in the rotation direction are sufficiently increased, and the compression deformation portions 29 and 29 existing between the bending deformation portions 30 and 30 come into contact with each other. In the case of this reference example , since the positional relationship between the mutually facing side surfaces of each of the compression deformation portions 29, 29 in the neutral state is substantially parallel or slightly inclined as described above, In a state where the large torque is transmitted, the mutually opposing side surfaces of the compression deformation portions 29 and 29 are almost in contact with each other. For this reason, a sufficiently large torque can be transmitted between the output shaft 12a and the worm shaft 6a. Even in this case, as the torque increases, the compression deforming portions 29 and 29 are elastically compressed in the circumferential direction, so that a buffering action related to torque fluctuation can be obtained.

In the case of this reference example , even if the center axis of the output shaft 12a and the center axis of the worm shaft 6a are slightly deviated from each other, this deviation is based on the elastic deformation of the bending deformation portions 30 and 30. Can be absorbed. For example, the central axis of the driven transmission member 19 fixed to the base end portion of the worm shaft 6a is different from the central axis of the driving transmission member 18 fixed to the distal end portion of the output shaft 12a in FIG. 2), the bending deformation portions 30 and 30 are elastically deformed unevenly as shown in FIG. 2C to absorb the displacement. For this reason, the worm teeth 5 provided on the worm shaft 6a are pressed against the worm wheel 4 by the coil spring 11 in order to eliminate the backlash existing in the meshing portion between the worm 8 and the worm wheel 4. Even if the base end portion of the shaft 6a is swingably coupled to the tip portion of the output shaft 12a, the worm shaft 6a can be smoothly driven to rotate by the output shaft 12a.

[Second Example of Reference Example of the Present Invention ]
FIG. 3 shows a second example of a reference example relating to the present invention . In the case of the elastic shaft joint 15a of this reference example, the thickness in the circumferential direction of each compression deformation portion 29a, 29a constituting each elastic deformation portion 27a, 27a of the elastic member 26a is constant in the radial direction. For this reason, in the case of this reference example , the space | interval of the side surfaces of the compression deformation parts 29a and 29a of the elastic deformation parts 27a and 27a adjacent to the circumference direction becomes large radially outer side. In other words, the clearance spaces 32, 32 existing between the side surfaces of each of the compression deformed portions 29a, 29a are in the neutral state shown in FIG. 3A or the torque transmission shown in FIG. Regardless of whether it is in a state or not, it becomes a wedge shape with a smaller dimension in the circumferential direction on the radially inner side.

Also in the case of this reference example , first, with the start of torque transmission from the drive-side transmission member 18 to the driven-side transmission member 19, each bend existing on the front side in the rotation direction of each drive-side protrusion 22 and 22 is firstly provided. The curvatures of the deformation parts 30 and 30 are increased, and the curvatures of the bending deformation parts 30 and 30 existing on the rear side are also reduced. Immediately after the start of torque transmission and when the torque to be transmitted is small, the torque is based on the elastic deformation of the bending deformation portions 30 and 30 in the same manner as in the first example of the embodiment described above. To communicate.

Also in the case of this reference example , when a certain amount of time has elapsed after the start of the torque transmission and the torque to be transmitted increases, as shown in FIG. The compression deformation portions 29a and 29a existing between the portions 30 and 30 come into contact with each other. In particular, in the case of this reference example , the distance between the side surfaces of the compression deformation portions 29a and 29a of the elastic deformation portions 27a and 27a adjacent in the circumferential direction is made smaller toward the inside in the radial direction. In this state, the radially inner end portions of the side surfaces facing each other of the compression deformation portions 29a and 29a are in contact with each other. And the said torque deformation | transformation is transmitted, elastically deforming the radial direction inner end part of each of these compression deformation parts 29a and 29a. The amount of elastic deformation at the radially inner end of each compression deformation portion 29a, 29a increases as the torque transmitted increases. For this reason, the buffering effect relating to the torque fluctuation can be increased as compared with the first example of the embodiment described above. Since the configuration and operation of the other parts are the same as in the first example of this embodiment, overlapping illustrations and explanations regarding equivalent parts are omitted.

[ Example of Embodiment ]
FIG. 4 shows an example of an embodiment of the present invention corresponding to claims 1 and 2 . In the case of the elastic shaft joint 15b of the present example, the adjacent elastic deformation portions 27b and 27b among the circumferential side surfaces of the compression deformation portions 29b and 29b constituting the elastic deformation portions 27b and 27b of the elastic member 26b are arranged. The outer surface facing each compression deformation part 29b and 29b which comprises is made into the partial cylindrical convex curved surface. Out of the circumferential side surfaces of each of these compression deformed portions 29b, 29b, the inner side surfaces that contact the circumferential side surfaces of the drive side and driven side projections 22, 25 are respectively centered on the central axis of the elastic member 26b. It is set as the plane which exists in the diameter direction. Accordingly, the thickness in the circumferential direction of each of the elastic deformation portions 27b, 27b is the largest in the radial intermediate portion, and gradually decreases toward the outer side and the inner side in the radial direction. In addition, the thickness of the bending deformation parts 30a and 30a which make the inner edge of radial direction of each said elastic deformation part 27b and 27b continue is equal to the thickness of the radial direction inner end of these each elastic deformation part 27b and 27b.

In the case of the structure of the present example configured as described above, when the torque transmitted between the drive-side transmission member 18 and the driven-side transmission member 19 increases to some extent, each of the elastic deformation portions 27b and 27b The radially intermediate portions of the outer side surfaces are in contact with each other. When the torque further increases from this state, the elastically deforming portions 27b, 27b are gradually expanded inward and outward in the radial direction from the radial intermediate portion. For this reason, as in the case of the second example of the reference example described above, the buffering action related to torque fluctuation can be made larger than that of the first example of the reference example described above. In particular, in the case of this example, the maximum value of the stress generated in each of the elastic deformation portions 27b and 27b at the time of large torque fluctuation is suppressed to be lower than the structure of the second example of the reference example described above. Since the configuration and operation of the other portions including the elastic deformation portions 27b and 27b, which are easy to ensure the durability of the elastic member 26b, are the same as those in the first example of the above reference example , Description is omitted.

  The above description has been given when the elastic shaft coupling of the present invention is mounted between the distal end portion of the output shaft of the electric motor constituting the electric power steering apparatus and the proximal end portion of the worm shaft. The elastic shaft coupling of the present invention is not limited to such a portion, and can be applied to various mechanical devices that transmit torque between a pair of rotating shafts.

The principal part sectional view of the electric power steering device which incorporated the elastic shaft coupling which shows the 1st example of the reference example about the present invention. Only the elastic shaft coupling is taken out, (A) shows a neutral state, (B) shows a state during torque transmission, and (C) shows a state in which the eccentricity between the output shaft and the worm shaft is compensated. XX view. The figure similar to (A) (B) of Drawing 2 showing the 2nd example of the reference example about the present invention. The figure similar to (A) of FIG. 2 which shows an example of embodiment of this invention . The partial longitudinal section side view showing an example of the steering device for cars. The expanded YY sectional drawing of FIG. 5 which shows an example of the conventional structure.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Housing 4 Worm wheel 5 Worm tooth | gear 6, 6a Worm shaft 7 Electric motor 8 Worm 9a, 9b Rolling bearing 10 Pressing piece 11 Coil spring 12, 12a Output shaft 13 Spline hole 14 Spline shaft part 15, 15a 15b Elastic shaft coupling 16 Driving side serration part 17 Driven side serration part
18 Drive-side transmission member
19 Driven side transmission member 20 Drive side boss part 21 Drive side arm part
22 Drive side protrusion 23 Driven side boss part 24 Driven side arm part
25 Driven side protrusions 26, 26a, 26b Elastic members 27, 27a, 27b Elastic deformation parts 28 Outer diameter side connection parts 29, 29a , 29b Compression deformation parts 30, 30a Bending deformation parts 31 Recesses 32 Gap space

Claims (4)

In order to transmit torque between ends of a pair of rotating shafts arranged in series with respect to the axial direction via an elastic member that can be elastically deformed with respect to the direction of the torque, one of the rotating shafts The rotary shaft is supported at the end of the rotary shaft concentrically with the one rotary shaft, on the surface facing the other rotary shaft of the two rotary shafts, and intermittently with respect to the rotational direction. A first transmission member provided with a plurality of first projecting portions projecting in the direction of the directional axis, and the one rotating shaft that is supported concentrically with the other rotating shaft at the end of the other rotating shaft A second transmission member provided with a plurality of second projecting portions projecting in the axial direction toward the one rotational axis intermittently with respect to the rotational direction, and circumferential side surfaces of the second projecting portions; Sandwiched between the circumferential side surfaces of each of the first protrusions, In the elastic shaft coupling including the elastic member, the elastic member includes a plurality of sandwiched between the circumferential side surface of each of the first protrusions and the circumferential side surface of each of the second protrusions. The elastically deforming parts are integrally joined to each other, and each of these elastically deforming parts is plate-like and faces each other via a gap in the torque transmission direction, and each of the rotating shafts rotates. A pair of compression deformable portions for each elastic deformable portion that can be elastically compressed with respect to the direction is formed by connecting the inner end edges in the radial direction of both rotation shafts by a partially cylindrical bent deformable portion. The both rotation shafts of the compression deforming portion having a V-shaped cross section and having the inner end edges not connected to each other by the bending deformation portions among the compression deformation portions of the elastic deformation portions adjacent in the circumferential direction. The outer edges in the radial direction of these two rotations Among the compression deformation portions that are connected to each other by the outer diameter side connection portions that exist outside the first and second protrusions with respect to the radial direction, and that constitute the elastic deformation portions, The surface opposite to the compression deformation portion constituting the elastic deformation portion adjacent to the rotation direction of the rotation shaft is a convex curved surface in which the intermediate portion in the radial direction of both rotation shafts protrudes most in the rotation direction. Elastic shaft coupling. The thickness of the bending deformation portion forming each elastic deformation portion, and smaller than the thickness of the compressive deformation portion of the same pair, is provided with a recess on the inner side with respect to the bending direction of the deformed portion the bending, wherein Item 2. An elastic shaft joint according to Item 1 . A housing that is supported by a fixed portion and does not rotate; a rotating shaft that is rotatably provided to the housing and is rotated by an operation of a steering wheel; A worm wheel that is supported concentrically with the rotary shaft inside the housing and rotates together with the rotary shaft, and a worm tooth is provided at an axially intermediate portion of the worm shaft. In a state where the worm teeth are engaged with the worm wheel, both end portions in the axial direction of the worm shaft are rotatably supported with respect to the housing by bearings, and an electric motor for rotationally driving the worm, A joint device that is provided between the distal end portion of the output shaft of the electric motor and the proximal end portion of the worm shaft and transmits torque between the two shafts. In the electric power steering apparatus provided with bets, the joint device, an electric power steering apparatus, characterized in that the elastic coupling according to any one of claims 1-2. The electric power steering apparatus according to claim 3 , wherein an elastic member that presses the worm teeth toward the worm wheel is provided between the tip of the worm shaft and the housing.

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