JP2006224945A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of achieving smooth operation, while aiming at downsizing. <P>SOLUTION: A deflector 45b of a nut 45 scoops up balls 65 from rolling paths (23b and 45f) to a tangential direction of the rolling raceway and in the direction of a lead angle. The balls 65 can be thereby scooped up to a circulation path 45c without changing rolling direction thereof, and smooth rolling is achieved, and operation noise and vibration can be restricted low. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric power steering apparatus provided with a ball screw mechanism.

  2. Description of the Related Art There is known an electric power steering device that drives an electric motor in accordance with steering torque and transmits the rotational force of the electric motor to a rack shaft to assist steering. Here, in order to convert the rotational force of the electric motor into the thrust of the rack shaft, a ball screw mechanism may be used (see Patent Document 1).

  By the way, in the electric power steering apparatus described in Patent Document 1, a gear is integrally formed on the outer periphery of the nut of the ball screw mechanism, and the power of the electric motor is transmitted to the nut via the gear. It has become. However, in order to increase the rotation of the nut, it is desired to suppress the inertia. Moreover, it is desired to keep the outer shape of the electric power steering device small, and for this purpose, it is preferable to make the outer diameter of the nut smaller.

  On the other hand, in the electric power steering apparatus described in Patent Document 2, end caps are attached to both ends of the nut of the ball screw mechanism for circulating the ball.

Japanese Patent Publication No. 6-504 Japanese Unexamined Patent Publication No. 2000-225956

  A schematic cross-sectional view of such a conventional ball screw mechanism is shown in FIG. As shown in the figure, in the case of the end cap type, the end face of the nut N is completely covered with the end cap ED. Therefore, when power is transmitted from the axial direction to the nut N for power transmission, the end cap ED If power is transmitted through the internal circuit, the internal circulation path may be distorted by the stress due to power transmission, and appropriate ball circulation may not be achieved, or the end cap ED may be damaged. However, if the end cap ED is thickened to increase the rigidity, the nut N becomes larger and heavier, and the inertial force that adversely affects assist control also increases.

  On the other hand, as shown by a dotted line in FIG. 9, it is conceivable that a flange F having an outer diameter larger than that of the end cap ED is provided on the nut N so that power is transmitted through the flange F. This leads to an increase in the size of the apparatus. On the other hand, when a general tube or piece is used for ball circulation, power transmission is possible through the end face of the nut, but there is a problem that the outer diameter of the nut is increased.

  Furthermore, in the electric power steering device described in Patent Document 1, a gear is integrally formed on the outer periphery of the nut of the ball screw mechanism so that the power of the electric motor is transmitted to the nut via the gear. It has become. However, when the nut and the screw shaft rotate relative to each other, a circulation path for returning the ball from one end of the rolling path to the other end is necessary. However, Patent Document 1 does not disclose anything about the circulation path. Therefore, it is considered that a tube or a top, which is a general circulation path, is used for such a nut. However, if a gear is formed on the outer periphery of the nut, it is difficult to dispose the tube or the piece across the gear. Therefore, regardless of the drawings of Patent Document 1, the electric power steering device disclosed in Patent Document 1 should be considered that the nut gear is displaced from the rolling path in the axial direction.

  However, assuming that the nut gears are arranged so as to be displaced outward in the axial direction from the rolling path, the torque transmitted from the electric motor is input to one end of the nut, so the nut is easily twisted and smooth. Power transmission cannot be performed. Also, when transmitting a large torque, the tooth width of the gear must be increased in order to reduce the surface pressure of the tooth surface, which increases the axial length of the nut, and the electric power steering device There is also a problem that compactness cannot be achieved.

  The present invention has been made in view of the problems of the prior art, and an object thereof is to provide an electric power steering apparatus that can ensure a smooth operation while achieving compactness.

The electric power steering apparatus of the first aspect of the present invention is
An electric motor;
A rack shaft coupled to a steering mechanism, and a power transmission mechanism for transmitting power from the electric motor to the rack shaft,
The power transmission mechanism is connected to or integrated with the rack shaft and includes a male screw groove, a nut disposed around the screw shaft and provided with a female screw groove, the male screw groove, and the screw shaft. A plurality of rolling elements capable of rolling in a rolling path formed between the female screw groove and
The nut includes a main body provided with a circulation path for the rolling elements extending in an axial direction, a rolling element provided at both ends of the main body and rolling on the rolling paths, in a tangential direction and a lead angle of the rolling path. It consists of a deflector scooped up in the direction and returned to the circulation path.

The electric power steering apparatus of the second aspect of the present invention is
An electric motor;
A rack shaft coupled to a steering mechanism, and a power transmission mechanism for transmitting power from the electric motor to the rack shaft,
The power transmission mechanism is connected to or integrated with the rack shaft and includes a male screw groove, a nut disposed around the screw shaft and provided with a female screw groove, the male screw groove, and the screw shaft. A plurality of rolling elements capable of rolling in a rolling path formed between the female screw groove and a sleeve having a receiving portion for receiving power transmitted from the electric motor;
The nut is inserted and fixed with respect to the sleeve so that the receiving portion is located radially outward of the rolling path, and rotates integrally with the nut.

The electric power steering apparatus of the third aspect of the present invention is:
An electric motor;
A rack shaft coupled to a steering mechanism, and a power transmission mechanism for transmitting power from the electric motor to the rack shaft,
The power transmission mechanism is connected to or integrated with the rack shaft and includes a male screw groove, a nut disposed around the screw shaft and provided with a female screw groove, the male screw groove, and the screw shaft. A plurality of rolling elements capable of rolling in a rolling path formed between the female screw groove and
The nut includes a main body provided with a circulation path for the rolling elements extending in an axial direction, a rolling element provided at both ends of the main body and rolling on the rolling paths, in a tangential direction and a lead angle of the rolling path. Consisting of a deflector that scoops up in the direction and returns to the circuit,
The power of the electric motor is transmitted to the nut through a fixing member that fixes the deflector to the nut.

The electric power steering device of the fourth aspect of the present invention is:
An electric motor;
A rack shaft coupled to a steering mechanism, and a power transmission mechanism for transmitting power from the electric motor to the rack shaft,
The power transmission mechanism is connected to or integrated with the rack shaft and includes a male screw groove, a nut disposed around the screw shaft and provided with a female screw groove, the male screw groove, and the screw shaft. A plurality of rolling elements capable of rolling in a rolling path formed between the female screw groove and
The nut includes a main body provided with a circulation path for the rolling elements extending in an axial direction, a rolling element provided at both ends of the main body and rolling on the rolling paths, in a tangential direction and a lead angle of the rolling path. Consisting of a deflector that scoops up in the direction and returns to the circuit,
The deflector is attached to the nut by fastening means for fixing a bearing that supports the nut.

The electric power steering apparatus of the fifth aspect of the present invention is
An electric motor;
A rack shaft coupled to a steering mechanism, and a power transmission mechanism for transmitting power from the electric motor to the rack shaft,
The power transmission mechanism is connected to or integrated with the rack shaft and includes a male screw groove, a nut disposed around the screw shaft and provided with a female screw groove, the male screw groove, and the screw shaft. A plurality of rolling elements capable of rolling in a rolling path formed between the female screw groove and
The nut includes a main body provided with a circulation path for the rolling elements extending in an axial direction, a rolling element provided at both ends of the main body and rolling on the rolling paths, in a tangential direction and a lead angle of the rolling path. Consisting of a deflector that scoops up in the direction and returns to the circuit,
A protrusion extending at least in the axial direction from the end surface or a recess recessed in the axial direction is formed on the end surface in the axial direction of the main body to transmit power of the electric motor.

  According to the electric power steering apparatus of the first aspect of the present invention, the nut scoops the rolling elements provided on both ends of the main body and rolling on the rolling path in the tangential direction and the lead angle direction of the rolling path. Since the deflector for returning to the circulation path is provided, scooping can be performed without changing the rolling direction of the rolling elements, so that smooth rolling can be ensured, and operating noise and vibration can be kept low. In particular, by providing the deflector, there is no need to provide a conventional frame or tube on the outer peripheral surface of the nut, and therefore the outer diameter of the nut can be kept small. Also, the axial length of the nut can be kept short compared to the end cap type.

  It is preferable that the nut is provided with a receiving portion that receives power transmitted from the electric motor on the outer side in the radial direction of the rolling path.

  The receiving portion is a gear portion formed on the outer peripheral surface of the nut, and it is preferable that the power from the electric motor is transmitted via another gear meshing with the gear portion. It may be transmitted via an attached belt or chain.

  The deflector is fixed to the nut using an annular fixing member that is press-fitted into the nut, and the fixing member has a female serration portion that engages with a male serration portion of an external member, It is preferable that power transmission is performed through the engaged male serration portion and female serration portion because power transmission can be performed without increasing the outer diameter of the nut.

  According to the electric power steering apparatus of the second aspect of the present invention, the nut is inserted and fixed with respect to the sleeve so as to rotate integrally. Therefore, regardless of the shape of the outer peripheral surface of the nut. In addition, a receiving portion that receives power transmitted from the electric motor can be provided on an outer circumferential surface of the sleeve in the radial direction of the rolling path, whereby power is transmitted from the electric motor to the receiving portion. Sometimes, the nut can be prevented from being twisted to enable smooth operation. Moreover, the axial direction length of the said sleeve and nut can also be suppressed by providing the receiving part which receives the motive power transmitted from the said electric motor in the outer peripheral surface of the radial direction outer side of the said rolling path. Further, since the nut having the female screw groove is inserted and fixed to the sleeve having the receiving portion, both can be processed separately, and thus the manufacturing cost can be reduced.

  The nut includes a main body provided with a circulation path for the rolling elements extending in an axial direction, a rolling element provided at both ends of the main body and rolling on the rolling paths, in a tangential direction and a lead angle of the rolling path. A deflector that scoops up in the direction and returns to the circuit is preferred.

  For example, according to the prior art described in Japanese Patent Application Laid-Open No. 2004-176826, instead of using a circulating member, an axial groove is provided on the outer periphery of the nut, and a groove connecting this to the spiral groove inside the nut is provided on both end faces. Have. However, with this connection configuration, the rolling direction of the ball changes greatly when moving from the spiral groove to the axial groove, so that the ball may not move smoothly and the operation may deteriorate. In addition, since the groove shape is complicated, the time required for processing increases and the cost increases.

  On the other hand, according to the present invention, the deflector scoops the rolling elements provided on both ends of the main body and rolling on the rolling path in the tangential direction and the lead angle direction of the rolling path, and returns to the circulation path. The ball can be circulated while maintaining the optimum clearance between the ball and the circulation path, and the change of the rolling direction of the rolling element can be suppressed, so that the ball can be smoothly moved and operated. Becomes better. Further, since the deflector can be provided separately from the nut, the nut can be easily processed.

  By providing the deflector instead of a tube or a piece, serrations and teeth can be formed on the outer peripheral surface of the nut, which facilitates fitting and fixing with the sleeve, but a nut having an end cap It may be. Further, a nut provided with a top and a tube can be used as long as it can be fitted and fixed to the sleeve.

  The nut is preferably fitted and fixed to the sleeve.

  The nut is preferably serrated to the sleeve.

  It is preferable that an elastic body is interposed between the nut and the sleeve. In this case, power transmission between the nut and the sleeve may be performed using the shearing force of the elastic body, or may be performed using the compression force.

  A convex portion is provided on the outer peripheral surface of the nut, a concave portion is provided on the inner peripheral surface of the sleeve, and the nut is engaged with the sleeve so that the convex portion is engaged with the concave portion. It is preferable.

  The shape of the nut can be optimized when at least a part of the convex portion is provided radially outward of the circulation path of the main body.

  If a buffer member is disposed between the convex portion and the concave portion in the circumferential direction, it can be mitigated even if an impact force from the electric motor or the rack shaft is transmitted.

  The nut and the sleeve each have a protrusion extending in the axial direction, and when the first buffer is disposed between the nut and the protrusion of the sleeve, the torque is transmitted by the first buffer. Vibration and noise can be suppressed, axial backlash between the nut and the sleeve can be eliminated, and a misalignment suppressing effect can be expected.

  If one of the nut and the sleeve has a protrusion extending in the axial direction and the other has a recess that engages with the protrusion, power can be transmitted between the nut and the sleeve. .

  When the first buffer is disposed between the protrusion and the recess, the first buffer suppresses vibration and noise during torque transmission, and eliminates axial play between the nut and the sleeve. Furthermore, the effect of suppressing misalignment can be expected.

  It is preferable that the gap that is reduced by relative movement in the compressing direction of the first buffer body is provided between the nut and the sleeve because the effect of the first buffer body can be effectively exhibited.

  When a second shock absorber is disposed between the screw member and the nut, the vibration and noise during torque transmission are generated by the second shock absorber. In addition, the axial play between the nut and the sleeve can be eliminated, and a misalignment suppressing effect can be expected.

  It is preferable that a gap that is reduced by relative movement in the direction in which the second buffer body is compressed is provided between the nut and the screw member because the effect of the second buffer body can be effectively exhibited. .

  It is preferable that the nut and the sleeve are connected by a key and rotate integrally with each other because torque transmission can be reliably performed with a simple configuration.

  The receiving portion is a gear portion formed on the outer peripheral surface of the sleeve, and it is preferable that the power from the electric motor is transmitted through another gear meshing with the receiving portion. It may be transmitted via an attached belt or chain.

  According to the electric power steering apparatus of the third aspect of the present invention, the nut scoops up the rolling elements provided on both ends of the main body and rolling the rolling path in the tangential direction and the lead angle direction of the rolling path. Since the deflector for returning to the circulation path is provided, it is not necessary to provide a conventional frame or tube on the outer peripheral surface of the nut, and therefore the outer diameter of the nut can be kept small. Also, the axial length of the nut can be kept short compared to the end cap type.

  Further, since the deflector is a member different from the nut, it is necessary to attach it to the nut. Therefore, if the power of the electric motor is transmitted to the nut via a fixing member that fixes the deflector to the nut, the power can be transmitted without increasing the outer diameter of the nut. This can reduce the number of parts and save space. Further, since no power is transmitted to the deflector, deformation and breakage due to power transmission do not occur.

  Preferably, the deflector is pressed against the nut at the end face of the fixing member.

  It is preferable that the nut and the fixing member are positioned by an inlay.

  When at least a part of the circulation path is formed by grooving the main body from the radial direction, the processing of the main body of the nut is facilitated.

  If a bearing is disposed radially outward of the processed groove, the groove can be used as a circulation path.

  It is preferable that a lid member that shields at least a part of the circulation path is disposed between the groove and the bearing, since the rolling of the ball passing through the circulation path becomes smooth.

  According to the electric power steering apparatus of the fourth aspect of the present invention, the nut scoops up the rolling elements provided on both ends of the main body and rolling the rolling path in the tangential direction and the lead angle direction of the rolling path. Since the deflector for returning to the circulation path is provided, it is not necessary to provide a conventional frame or tube on the outer peripheral surface of the nut, and therefore the outer diameter of the nut can be kept small. Also, the axial length of the nut can be kept short compared to the end cap type.

  On the other hand, the conventional deflector is directly screwed to the nut, or is fixed to the nut by using a separate fixing plate, so that the number of parts is increased and it takes time and effort to assemble. There are challenges. On the other hand, according to the present invention, since the deflector is attached to the nut by the fastening means for fixing the bearing that supports the nut, the number of parts required for assembly is reduced and the assembly is facilitated. .

  When an elastic body is interposed between the deflector and the fastening means, the elastic body can reduce vibration and noise of the deflector during operation.

  Providing a protrusion on the deflector and fixing the fastening means in contact with the protrusion makes it easier to fix the deflector.

  According to the electric power steering apparatus of the fifth aspect of the present invention, the nut scoops up the rolling elements provided on both ends of the main body and rolling the rolling path in the tangential direction and the lead angle direction of the rolling path. Since the deflector for returning to the circulation path is provided, it is not necessary to provide a conventional frame or tube on the outer peripheral surface of the nut, and therefore the outer diameter of the nut can be kept small. Also, the axial length of the nut can be kept short compared to the end cap type.

  Further, the deflector only needs to have a function of scooping up the ball from the rolling path to the circulation path, and therefore, when attached to the main body of the nut, a part of the end surface of the main body is exposed. be able to. Therefore, the exposed end face is provided with a projection extending in the axial direction or a concave portion recessed in the axial direction, and this is overlapped with the projection or concave portion of the external member in the circumferential direction to transmit the pressing force from one to the other. If the power of the electric motor is transmitted to the nut, the power can be transmitted without increasing the outer diameter of the nut. Further, since no power is transmitted to the deflector, deformation and breakage due to power transmission do not occur.

  If an elastic body is provided between the driven member that receives power from the electric motor and the projection or the recess, vibration and noise during operation can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of the electric power steering apparatus according to the first embodiment. FIG. 2 is a view of the nut of FIG. 1 cut along the line II-II and viewed in the direction of the arrow, but the screw shaft and the ball are omitted. In FIG. 1, the electric power steering apparatus 11 has a housing 21 fixed to a vehicle body (not shown). A rack shaft 23 is supported so as to be movable in the axial direction so as to penetrate the housing 21 horizontally. Although not shown, a pinion is formed at the lower end of the input shaft connected to the steering wheel and meshes with the rack teeth of the rack shaft 23. The rack shaft 23 moves to the left and right in the figure by the rotation of the input shaft. It is supposed to be. Both ends of the rack shaft 23 are connected to tie rods (not shown) of the steering mechanism.

  An electric motor 35 is attached to the housing 21 so that the rack shaft 23 and the axis are parallel to each other. The output shaft 35a of the electric motor 35 is fixed to the drive shaft 37 so as to be relatively displaceable in the axial direction by serration coupling and integrally in the rotational direction. The drive shaft 37 is rotatably supported with respect to the housing 21 by bearings 20 and 22, and has a drive gear portion 37 a at a portion sandwiched between the bearings 20 and 22.

  An intermediate shaft 38 is disposed between the drive shaft 37 and the rack shaft 23. The intermediate shaft 38 is rotatably supported with respect to the housing 21 by bearings 24 and 25, and has an intermediate gear portion 38 a that meshes with the drive gear portion 37 a at a portion sandwiched between the bearings 24 and 25. .

  A nut 45 is disposed around the rack shaft 23, and is rotatably supported with respect to the housing 21 by a ball bearing 26 and a double-row angular ball bearing 27. The inner ring of the double row angular ball bearing 27 is fixed while being preloaded by the inner ring restraint 51 that is screwed onto the inner circumference of the nut 45, and the outer ring of the double row angular ball bearing 27 is screwed into the inner circumference of the housing 21. It is fixed by an outer ring retainer 52. Therefore, the nut 45 is attached in a state in which the backlash is suppressed in the axial direction.

  The nut 45 includes a central hollow cylindrical main body 45a and deflectors 45b at both ends (only one side is shown). As shown in FIG. 2, the main body 45a forms a circulation path 45c penetrating in the axial direction.

  4 is an enlarged view of a portion indicated by an arrow IV in the configuration of FIG. 1, and FIG. 5 is a view of the configuration of FIG. 4 taken along the line VV and viewed in the direction of the arrow. Each deflector 45b (only one is shown in FIGS. 4 and 5) attached by a fixing plate 45h screwed to the main body 45a causes the ball 65 that has rolled to move as shown in FIG. A scooping piece 45d that returns to the circulation path 45c is formed by scooping up in the θ direction and scooping up in the tangential direction of the rolling path (screw groove) as shown in FIG.

  In FIG. 1, a fixing plate 45 g is screwed to the left end of the main body 45. Further, a driven gear portion (receiving portion) 45e that meshes with the intermediate gear portion 38a is provided at a portion sandwiched between the bearings 26 and 27 of the main body 45a. The drive gear portion 37a, the intermediate gear portion 38a, and the driven gear portion 45e constitute a gear pair.

  A male screw groove 23b is formed in a part of the outer peripheral surface of the rack shaft 23 which is integral with the screw shaft (may be connected with another part). A nut 45 is disposed around the male screw groove 23b, and a female screw groove 45f is formed on the inner peripheral surface of the main body 45a facing the male screw groove 23b. A large number of balls 65 are rollably arranged in a spiral space (rolling path) formed by the male screw groove 23b and the female screw groove 45f. The screw shaft 23, the nut 45, and the ball 65 constitute a ball screw mechanism (power transmission mechanism).

  The operation of this embodiment will be described. Although not shown, when the driver rotates the steering wheel, the rotational force is transmitted to the input shaft. When the input shaft rotates, the rack teeth meshed with the pinion are pushed, the rack shaft 23 moves in the axial direction, and the steering mechanism (not shown) is driven via the tie rod, so that the wheels are steered. ing.

  At this time, a torque sensor (not shown) detects the steering torque, and a CPU (not shown) supplies electric power to the electric motor 35 according to the amount, so that the drive gear portion 37a rotates with the output shaft, and the intermediate gear. The gear part 45e engaged through the part 38a is rotated at a predetermined reduction ratio. As a result, the nut 45 also rotates, and this rotational motion is converted into the axial motion of the rack shaft 23 via the balls 65. The ball 65 rolled to one end of the rolling path is picked up by the deflector 45b and returned to the other end via the circulation path 45c. An auxiliary steering force can be output using the axial force of the rack shaft 23.

  In the electric power steering apparatus 11 according to the present embodiment, the nut 45 scoops up the ball 65 from the rolling path (23b, 45f) in the tangential direction and the lead angle direction of the rolling path, so that the rolling direction of the ball 65 is changed. Since it can scoop up to circulation way 45c, without changing, smooth rolling can be secured and operation sound, vibration, etc. can be suppressed low. Further, since the deflectors 45b are provided at both ends of the main body 45a, it is not necessary to provide a frame or a tube on the outer peripheral surface of the main body 45a, and the receiving portion that receives the power transmitted from the electric motor 35, that is, the driven gear portion 45e is used as a rolling path. Therefore, when the power is transmitted from the electric motor 35 to the driven gear portion 45e, the nut 45 is prevented from being twisted to enable smooth operation. it can. Further, the axial length of the nut 45 can also be suppressed by providing the driven gear portion 45e that receives the power transmitted from the electric motor 35 on the outer circumferential surface of the rolling path radially outward.

  FIG. 3 is a cross-sectional view of a main part of the electric power steering apparatus 111 according to the second embodiment. In the present embodiment, only different points from the embodiment shown in FIGS. 1 and 2 will be described, and the description of the common configuration will be omitted by attaching the same reference numerals.

  In the present embodiment, instead of omitting the intermediate shaft, a toothed belt 55 that engages with the gear portion 37a of the drive shaft 37 and the driven gear portion 45e of the main body 45 is provided. Therefore, if the drive gear portion 37a rotates together with the output shaft 35a of the electric motor 35, the driven gear portion 45e is rotated at a predetermined reduction ratio via the toothed belt 55. As a result, the nut 45 also rotates, so that the power of the electric motor 35 can be transmitted to the screw shaft 23. A chain may be used instead of the toothed belt.

  FIG. 6 is a cross-sectional view of a main part of an electric power steering apparatus 211 according to the third embodiment. FIG. 7 is an exploded view of the nut and the driven gear, and FIG. 8 is a view seen in the axial direction with the deflector removed from the nut.

  In FIG. 6, the electric power steering apparatus 211 has a housing 121 fixed to a vehicle body (not shown). The housing 121 is divided into three parts in FIG. 6, and is integrated by bolting from the members 121A, 121B, and 121C. A rack shaft 123 is supported so as to be movable in the axial direction so as to penetrate the housing 121 horizontally. Although not shown, a pinion is formed at the lower end of the input shaft connected to the steering wheel and meshes with the rack teeth of the rack shaft 123. The rack shaft 123 moves to the left and right in the figure by the rotation of the input shaft. It is supposed to be. Both ends of the rack shaft 123 are connected to tie rods (not shown) of the steering mechanism.

  An electric motor (not shown) is attached to the housing 121 so that the rack shaft 123 and the axis are parallel to each other. The power of the electric motor is transmitted to an intermediate shaft 138 that is only partially shown in FIG. The intermediate shaft 138 is rotatably supported with respect to the housing 121 by bearings 124 and 125, and has an intermediate gear portion 138 a at a portion sandwiched between the bearings 124 and 125.

  A nut 145 is disposed around the rack shaft 123 and is rotatably supported with respect to the housing 121 by a double-row angular ball bearing 127. This will be described more specifically. A thin cylindrical sleeve 139 is disposed so as to fit in the inner hole 121a in the member 121A of the housing 121. In addition, the ring-shaped member 130, the first buffer member 131, the outer ring 127a of the double row angular ball bearing 127, and the second buffer member 132 are arranged in this order from the bottom surface (left side in FIG. 6) of the inner hole 121a. It is fixed by a lock member 133 to be joined. The first buffer member 131 has an elastic body 131 a that contacts the ring-shaped member 130. In addition, the second buffer member 132 has an elastic body 132 a that abuts against the lock member 133. Due to the elastic deformation of the elastic bodies 131a and 132a, the double-row angular ball bearing 127 can move in the axial direction together with the nut 145 within a limited range. The outer ring 127 a is fitted to the inner peripheral surface of the sleeve 139.

  The inner rings 127b and 127b of the double row angular ball bearing 127 that are divided into two and arranged in the axial direction are fitted to the outer peripheral surface of the nut 145, and the right end in the drawing is the outer periphery formed near the right end of the nut 145. It contacts the step 145h. Further, the left end of the inner rings 127b and 127b is in contact with the right end of the screw member 134, and preload is applied thereto. The screw member 134 is screwed into a screw portion 145k formed on the outer peripheral surface of the nut 145. The preload can be adjusted by the screwing amount of the screw member 134.

  In FIG. 7, the nut 145 includes a hollow cylindrical main body 145a and deflectors 145b provided at both ends thereof. The main body 145a forms a circulation path 145c (see FIG. 6) penetrating in the axial direction, and each deflector 145b scoops the rolled ball 165 in the tangential direction of the rolling path and in the lead angle direction. A scooping piece 145d to be returned to 145c is formed. The deflector 145b has the same shape as the deflector 45b shown in FIGS.

  In FIG. 7, a deflector 145 b is disposed at the left end of the main body 145 a of the nut 145, and is fixed by a donut disk-shaped holding plate 135 screwed to the main body 145 a by a screw 136. On the other hand, a deflector 145b is disposed at the right end of the main body 145a of the nut 145, and is fixed by an annular fixing member 147 that is press-fitted into a large-diameter portion 145j formed on the inner periphery of the right end of the nut 145. A female serration portion 147 a is formed on the inner periphery of the annular member 147.

  In FIG. 6, a hollow driven gear 137 that is a driven member (external member) is rotatably supported at both ends by bearings 126 and 129 with respect to the housing 121, and is a driven gear that meshes with the intermediate gear portion 138a. In addition to having a portion 137a, a male serration portion 137b is formed on the outer periphery of the left end. The intermediate gear portion 138a and the driven gear portion 137a constitute a gear pair. The nut 145 and the like can be assembled from the right side of the drawing with the members 121A and 121B of the housing 121 removed.

  By engaging the male serration portion 137b of the driven gear 137 and the female serration portion 147a of the annular member 147, the driven gear 137 and the fixed member 147 can move relative to each other in the axial direction, but cannot rotate relative to each other in the rotational direction. Connected. The reason why the driven gear 137 and the fixed member 147 can be moved relative to each other in the axial direction is to exhibit the buffering effect of the elastic bodies 131a and 132a. Even when a large load is transmitted between the male serration portion 137 b of the driven gear 137 and the female serration portion 147 a of the annular member 147, since the stress is not directly applied to the deflector 145 b, the deformation of the ball 165 is suppressed. Rolling defects are not incurred.

  Thus, according to the present embodiment, the nut 145 can be easily manufactured by press-fitting the annular member 147 formed with the female serration portion 147a without forming the female serration portion in the nut 145. There is an advantage and the point that the outer diameter of the nut 145 and the inner diameter of the female serration portion 147a are irrelevant and can be arbitrarily replaced with an annular member in which the outer diameter of the serration, the number of teeth, etc. are changed according to the specification.

  In FIG. 6, a male screw groove 123b is formed in a part of the outer peripheral surface of the rack shaft 123 that is integral with the screw shaft (may be connected as a separate part). A nut 145 is disposed around the male screw groove 123b, and a female screw groove 145f is formed on the inner peripheral surface of the main body 145a facing the male screw groove 123b. In a spiral space (rolling path) formed by the male screw groove 123b and the female screw groove 145f, a large number of balls (rolling elements) 165 are arranged to roll freely. The screw shaft 123, the nut 145, and the ball 165 constitute a ball screw mechanism (power transmission mechanism).

  The operation of this embodiment will be described. Although not shown, when the driver rotates the steering wheel, the rotational force is transmitted to the input shaft. When the input shaft rotates, the rack teeth meshed with the pinion are pushed, the rack shaft 123 moves in the axial direction, and the steering mechanism (not shown) is driven via the tie rod, so that the wheels are steered. ing.

  At this time, a torque sensor (not shown) detects the steering torque, and a CPU (not shown) supplies electric power to the electric motor according to the amount, so that the driven gear portion 137a meshed via the intermediate gear portion 138a, It is rotated at a predetermined reduction ratio. Accordingly, the rotational power is transmitted from the driven gear 137 to the nut 145 via the fixing member 147, and the rotational motion of the nut 145 is converted to the axial motion of the rack shaft 123 via the ball 165. The ball 165 rolled to one end of the rolling path is picked up by the deflector 145b and returned to the other end via the circulation path 145c. An auxiliary steering force can be output using the axial force of the rack shaft 123.

  FIG. 10 is a cross-sectional view of a main part of an electric power steering apparatus 311 according to the fourth embodiment. In the present embodiment, only differences from the embodiment shown in FIG. 6 will be described, and the description of the common components will be omitted by attaching the same reference numerals.

  In the present embodiment, instead of omitting the intermediate shaft, a toothed belt 155 that transmits power to the gear portion 137a of the driven shaft 137 is provided. Therefore, the power from the electric motor (not shown) is transmitted to the driven shaft 137 via the toothed belt 155, and the nut 145 connected thereto is also rotated, so that the power of the electric motor is transmitted to the screw shaft 123. Can do. A chain may be used instead of the toothed belt.

  FIG. 11 is a cross-sectional view of a main part of an electric power steering apparatus according to a fifth embodiment. In FIG. 11, an electric power steering apparatus 1011 has a housing 1021 fixed to a vehicle body (not shown). A rack shaft 1023 is supported so as to be movable in the axial direction so as to penetrate the housing 1021 horizontally. Although not shown, a pinion is formed at the lower end of the input shaft connected to the steering wheel and meshes with the rack teeth of the rack shaft 1023. The rack shaft 1023 moves to the left and right in the figure by the rotation of the input shaft. It is supposed to be. Both ends of the rack shaft 1023 are connected to tie rods (not shown) of the steering mechanism.

  An electric motor 1035 is attached to the housing 1021 so that the rack shaft 1023 and the axis are parallel to each other. An output shaft 1035a of the electric motor 1035 is fixed to the drive shaft 1037 so as to be relatively displaceable in the axial direction by serration coupling and integrally in the rotational direction. The drive shaft 1037 is rotatably supported with respect to the housing 1021 by bearings 1020 and 1022, and has a drive gear portion 1037a in a portion sandwiched between the bearings 1020 and 1022.

  An intermediate shaft 1038 is disposed between the drive shaft 1037 and the rack shaft 1023. The intermediate shaft 1038 is rotatably supported with respect to the housing 1021 by bearings 1024 and 1025, and has an intermediate gear portion 1038a that meshes with the drive gear portion 1037a at a portion sandwiched between the bearings 1024 and 1025. .

  A cylindrical sleeve 1050 is disposed around the rack shaft 1023 and is rotatably supported with respect to the housing 1021 by ball bearings 1026 and angular ball bearings 1027 and 1027. A nut 1045 through which the rack shaft 1023 passes is fitted in the sleeve 1050, and is fixed by a screw member 1051 screwed into the inner periphery thereof. Therefore, the sleeve 1050 and the nut 1045 rotate integrally.

  The inner rings of the angular ball bearings 1027, 1027 are fixed while being preloaded by an inner ring restrainer 1052 that is screwed into the inner circumference of the sleeve 1050, and the outer rings of the angular ball bearings 1027, 1027 are screwed into the inner circumference of the housing 1021. It is fixed by an outer ring restraint 1053. Therefore, the sleeve 1050 is attached in a state where the backlash is suppressed in the axial direction.

  The nut 1045 includes a central hollow cylindrical main body 1045a and deflectors 1045b and 1045b at both ends. The main body 1045a forms a circulation path 1045c penetrating in the axial direction, and each deflector 1045b scoops up the rolling ball 1065 in the tangential direction and the lead angle direction of the rolling path into the circulation path 1045c. A return scooping piece 1045d is formed. Further, a driven gear portion (receiving portion) 1050 a that meshes with the intermediate gear portion 1038 a is provided in a portion sandwiched between the bearings 1026 and 1027 of the sleeve 1050. The drive gear portion 1037a, the intermediate gear portion 1038a, and the driven gear portion 1050a constitute a gear pair.

  A male screw groove 1023b is formed in a part of the outer peripheral surface of the rack shaft 1023 that is integral with the screw shaft (may be connected with another part). A nut 1045 is disposed around the male screw groove 1023b, and a female screw groove 1045f is formed on the inner peripheral surface of the main body 1045a facing the male screw groove 1023b. A large number of balls 1065 are rollably arranged in a spiral space (rolling path) formed by the male screw groove 1023b and the female screw groove 1045f.

  The operation of this embodiment will be described. Although not shown, when the driver rotates the steering wheel, the rotational force is transmitted to the input shaft. When the input shaft rotates, the rack teeth meshed with the pinion are pushed, the rack shaft 23 moves in the axial direction, and the steering mechanism (not shown) is driven via the tie rod, so that the wheels are steered. ing.

  At this time, a torque sensor (not shown) detects the steering torque, and a CPU (not shown) supplies electric power to the electric motor 1035 according to the amount, so that the drive gear portion 1037a rotates with the output shaft, and the intermediate gear. The driven gear 1050a meshed with the portion 1038a is rotated at a predetermined reduction ratio. As a result, the nut 1045 also rotates together with the sleeve 1050, and the rotational motion is converted into the axial motion of the rack shaft 1023 via the ball 1065. The ball 1065 that has rolled to one end of the rolling path is picked up by the deflector 1045b and returned to the other end via the circulation path 1045c. An auxiliary steering force can be output using the axial force of the rack shaft 1023.

  In the electric power steering apparatus 1011 according to the present embodiment, the nut 1045 is inserted and fixed to the sleeve 1050 so as to rotate integrally. Therefore, regardless of the shape of the outer peripheral surface of the nut 1045. The driven gear portion 1050a that receives the power transmitted from the electric motor 1035 can be provided on the outer circumferential surface of the sleeve 1050 in the radial direction of the rolling path (1023b, 1045f), so that the power is driven by the electric motor 1035. When transmitted to the gear portion 1050a, the nut 1045 can be prevented from being twisted to enable smooth operation. Further, by providing a driven gear portion 1050a that receives power transmitted from the electric motor 1035 on the radially outer peripheral surface of the rolling path (1023b, 1045f), the axial length of the sleeve 1050 and the nut 1045 is suppressed. You can also. Furthermore, since the nut 1045 having the female thread groove 1045f is inserted and fixed to the sleeve 1050 having the driven gear portion 1050a, both can be processed separately, so that the manufacturing cost can be reduced.

  FIG. 12A is an axial sectional view of the ball screw mechanism according to the sixth embodiment, and FIG. 12B is an arrow obtained by cutting the nut of FIG. 12A along the line XIIB-XIIB. Although it is the figure seen in the direction, the ball is omitted. In FIG. 12, the sleeve 1150 and the nut 1145 are serrated. More specifically, the nut 1145 is inserted into the sleeve 1150 such that the female serration 1150b formed on the inner periphery of the sleeve 1150 and the same number of male serrations 1145g formed on the outer periphery of the nut 1145 are engaged. It is inserted and fixed, so that it can rotate integrally. As a result, even when a high torque is transmitted between the sleeve 1150 and the nut 1145, relative slippage between the two can be suppressed. Other configurations are the same as those in the embodiment shown in FIG.

  FIG. 13A is a sectional view in the axial direction of the ball screw mechanism according to the seventh embodiment, and FIG. 13B is an arrow formed by cutting the nut of FIG. 13A along the line XIIIB-XIIIB. Although it is the figure seen in the direction, the ball is omitted. In FIG. 13, on the outer periphery of the nut 1245, a raised portion 1245g which is a convex portion extends in the axial direction so as to cover the circulation path 1245c (that is, at least a part is located radially outward). It is provided as it exists. On the other hand, a groove 1250b, which is a recess corresponding to the raised portion 1245g, is formed on the inner periphery of the sleeve 1250. The nut 1245 is inserted and fixed in the sleeve 1250 so that the raised portion 1245g is engaged with the groove 1250b, and thus can rotate integrally. As a result, even when a high torque is transmitted between the sleeve 1250 and the nut 1245, the relative slip of both can be suppressed, and the thickness of the nut 1245 can be reduced. Other configurations are the same as those in the embodiment shown in FIG.

  Note that the number of raised portions is not necessarily limited to one. For example, as in the modification shown in FIG. 14A, two raised portions 1245g ′ facing the groove 1250b ′ are provided at a phase of 180 degrees, or as shown in the modification shown in FIG. 14B. Four ridges 1245g ″ facing 1250b ″ can be provided in 90 ° phase, but the number and phase are not limited to these.

  Depending on the nut, there may be two circulation paths. Therefore, for example, as in the modification shown in FIG. 15A, two raised portions 1245g ′ facing the groove 1250b ′ are formed so as to cover the circulation path 1245c ′ provided in a 180-degree phase. 15 (b), four raised portions 1245g ″ facing the grooves 1250b ″ (two of them are arranged so as to cover the circulation path 1245c ″ provided in a 180-degree phase). ), 90 degree phase.

  FIG. 16 is a cross-sectional view in the direction perpendicular to the axis of the ball screw mechanism according to the eighth embodiment, but the balls are omitted. In FIG. 16, external teeth 1345 g are formed on the entire periphery of the nut 1345, while internal teeth 1350 b are formed on the entire periphery of the sleeve 1350. The outer diameter of the nut 1345 is smaller than the inner diameter of the sleeve 1350. Therefore, the outer teeth 1345g and the inner teeth 1350b are not directly engaged with each other, and a cylindrical toothed belt 1353 is inserted therebetween. The toothed belt 1353 is formed with teeth on the inner and outer circumferences, the inner teeth mesh with the outer teeth 1345g, and the outer teeth mesh with the inner teeth 1350b. Thereby, the sleeve 1350 and the nut 1345 can be rotated integrally. According to the present embodiment, since the toothed belt 1353 functions as an elastic body, the impact force transmitted between the sleeve 1350 and the nut 1345 can be reduced. Instead of the toothed belt 1353, rubber or resin may be welded between the sleeve 1350 and the nut 1345 so as to function as an elastic body.

  FIG. 17 is a cross-sectional view in the direction perpendicular to the axis of the ball screw mechanism according to the ninth embodiment, but the balls are omitted. In FIG. 17, on the outer periphery of the nut 1445, a raised portion 1445g which is a convex portion extends in the axial direction so as to cover the circulation path 1445c (that is, at least a part is located radially outward). It is provided as it exists. On the other hand, a groove 1450b that is a recess corresponding to the raised portion 1445g is formed on the inner periphery of the sleeve 1450. The width of the groove 1450b is larger than the width of the raised portion 1445g, and when the raised portion 1445g is engaged with the groove 1450b, it is preferable that the buffer member 1453 (made of rubber or resin material) is formed in both spaces generated in the circumferential direction. ). When torque transmission is generated between the sleeve 1450 and the nut 1445, the raised portion 1445g which is a convex portion relatively moves in the groove 1450b. However, even when an impact force is generated at this time, the buffer member 1453 is applied. It is designed to reduce the impact force.

  Note that the number of raised portions is not necessarily limited to one. For example, two raised portions 1445g ′ facing the groove 1450b ′ are provided in a 180-degree phase as in the modified example shown in FIG. 18, or the raised parts facing the groove 1450b ″ as in the modified example shown in FIG. Four portions 1445g ″ may be provided with a 90-degree phase, but the number and phase are not limited to these.

  FIG. 20 is a cross-sectional view of a main part of an electric power steering apparatus 1511 according to the tenth embodiment. In the present embodiment, only differences from the embodiment shown in FIG. 11 will be described, and the description of the common configuration will be omitted by attaching the same reference numerals.

  In this embodiment, instead of omitting the intermediate shaft, a toothed belt 1055 that engages with the gear portion 1037a of the drive shaft 1037 and the driven gear portion 1050a of the sleeve 1050 is provided. Therefore, when the drive gear portion 1037a rotates together with the output shaft 1035a of the electric motor 1035, the driven gear portion 1050a is rotated at a predetermined reduction ratio via the toothed belt 1055. Accordingly, the sleeve 1050 and the nut 1045 also rotate, so that the power of the electric motor 1035 can be transmitted to the screw shaft 1023. A chain may be used instead of the toothed belt. Needless to say, the ball screw mechanism according to the modified examples of FIGS.

  FIG. 21 is a cross-sectional view of a main part of an electric power steering apparatus 1611 according to the eleventh embodiment. FIG. 22 is an exploded perspective view of the nut and sleeve according to the present embodiment, but the bearing is omitted. Fig.23 (a) is a figure which shows the end surface of the nut concerning this Embodiment, FIG.23 (b) cut | disconnected the structure of Fig.23 (a) by the XXIIIB-XXIIIB line | wire and looked at the arrow direction. FIG. 23 (c) is a diagram showing a deflector. In the present embodiment, only differences from the embodiment shown in FIG. 11 will be described, and the description of the common configuration will be omitted by attaching the same reference numerals.

  In the present embodiment, the configurations of the nut and the sleeve are different. More specifically, as shown in FIG. 22, on the bottom wall 1650b of the sleeve 1650, four prismatic protrusions 1650c protrude in the axial direction at intervals of 90 degrees in the circumferential direction (extend from the bottom surface in the axial direction). Formed).

  Further, four prismatic protrusions 1645g are formed on the end surface of the main body 1645a of the nut 1645 facing the sleeve 1650 so as to protrude in the axial direction at intervals of 90 degrees in the circumferential direction. Between the nut 1645 and the sleeve 1650, a ring-shaped first buffer (made of rubber or resin) 1635 is disposed. The first buffer 1635 has eight grooves 1635a formed at intervals of 45 degrees in the circumferential direction. The shape of the groove 1635a corresponds to the protrusions 1645g and 1650c.

  At the time of assembly, the protrusion 1645g of the nut 1645 passes through the groove 1635a of the first buffer 1635, and the protrusion 1650c of the sleeve 1650 passes through the remaining groove 1635a of the first buffer 1635. That is, the first buffer 1635 is positioned between the protrusions 1645g and 1650c alternately arranged in the circumferential direction. In this state, the nut 1645 and the sleeve 1650 are assembled so as to rotate integrally by screwing the male screw portion 1051a of the screw member 1051 into the female screw portion 1650d formed on the inner periphery of the end portion of the sleeve 1650. The bearings 1027 and 1027 can be assembled by fitting the bearings 1027 and 1027 (see FIG. 21) to the outer periphery of the sleeve 1650 and screwing the male screw portion 1052a of the inner ring restraint 1052 into the female screw portion 1650d.

  According to the present embodiment, since the first buffer 1635 is disposed between the protrusion 1645g of the nut 1645 and the protrusion 1650c of the sleeve 1650, the first buffer 1635 is deformed during torque transmission. As a buffering effect, vibration and noise during torque transmission can be suppressed, axial backlash between the nut 1645 and the sleeve 1650 can be eliminated, and a misalignment suppressing effect can also be expected.

  For example, a similar function can be exhibited even if a recess corresponding to the protrusion 1650c of the sleeve 1650 (or the protrusion 1645g of the nut 1645) is provided in the nut 1645 (or the sleeve 1650) and engaged therewith.

  Furthermore, as shown in FIG. 22, the main body 1645a of the nut 1645 has an axial groove 1645c formed on the outer periphery. The axial groove 1645c is configured such that a nut 1645 is fitted to a sleeve 1650 indicated by a one-dot chain line in FIG. 23B, so that the outside is covered with an inner peripheral surface 1650e to form a circulation path. . In the above-described embodiment, all the circulation paths penetrate the nut body, but a long drill is required to form this, and machining is relatively difficult. On the other hand, according to the present embodiment, the axial groove 1645c can be easily machined by milling or the like. In addition, in the circulation path of the through hole type, the thickness of the nut main body becomes thick as shown by a dotted line in FIG. 23A, but in this embodiment, the thickness of the main body 1645a can be made thin as shown by the solid line, It is possible to provide a ball screw mechanism that can easily accelerate and decelerate while suppressing the inertial mass.

  Similarly to the above-described embodiment, also in the present embodiment, the deflector 1645b shown in FIG. 23 (c) shows the ball 1065 rolling on the rolling path in the nut 1645 as shown in FIG. 23 (a). Further, it is scooped up in the tangential direction of the rolling path, and as shown in FIG.

  FIG. 24 is a cross-sectional view of main parts of an electric power steering apparatus 1711 according to the twelfth embodiment. In the present embodiment, only differences from the embodiment shown in FIG. 21 will be described, and the description of the common components will be omitted by attaching the same reference numerals.

  In this embodiment, instead of omitting the intermediate shaft, a toothed belt 1055 that engages with the gear portion 1037a of the drive shaft 1037 and the driven gear portion 1650a of the sleeve 1650 is provided. Therefore, when the drive gear portion 1037a rotates together with the output shaft 1035a of the electric motor 1035, the driven gear portion 1650a is rotated at a predetermined reduction ratio via the toothed belt 1055. Accordingly, the sleeve 1650 and the nut 1645 also rotate, so that the power of the electric motor 1035 can be transmitted to the screw shaft 1023. A chain may be used instead of the toothed belt.

  FIG. 25 is a cross-sectional view of a main part of an electric power steering apparatus 1811 according to the thirteenth embodiment. FIG. 26 is an exploded perspective view showing the nut and inner ring restraint according to the present embodiment. In the present embodiment, only differences from the embodiment shown in FIG. 21 will be described, and the description of the common components will be omitted by attaching the same reference numerals.

  In the present embodiment, as shown in FIG. 26, four prismatic projections 1845h are formed on the end surface of the nut 1845 on the inner ring restraint 1852 side so as to protrude in the axial direction at intervals of 90 degrees in the circumferential direction. .

  As in the above-described embodiment, four prismatic projections 1845g are formed on the end surface of the nut 1845 on the sleeve bottom wall side so as to protrude in the axial direction at intervals of 90 degrees in the circumferential direction.

  A ring-shaped second buffer (made of rubber or resin) 1835 is disposed between the nut 1845 and the inner ring retainer 1852. The second buffer body 1835 forms four groove portions 1835a at intervals of 90 degrees in the circumferential direction. The shape of the groove 1835a corresponds to the protrusion 1845h.

  At the time of assembly, the protrusion 1845h of the nut 1845 is disposed so as to fit into the groove 1835a of the second buffer 1835 as shown in FIG. 25, but the protrusion 1845h does not penetrate the second buffer 1835 and suppresses the inner ring. A clearance Δ 2 is defined between the end face 1852 and the end face 1852. On the other hand, the protrusion 1845g of the nut 1845 is disposed so as to fit into the groove portion of the first buffer body 1635 shown in FIG. 25, but the protrusion 1845g does not penetrate through the first buffer body 1635 and is between the bottom surface of the sleeve 1650. Define the clearance Δ1. In this state, the bearings 1027 and 1027 (see FIG. 25) are fitted to the outer periphery of the sleeve 1650, and the male screw portion 1852a of the inner ring retainer 1852 is screwed into the sleeve 1650, whereby the bearings 1027 and 1027 can be assembled. .

  According to the present embodiment, the clearance Δ2 is defined between the nut 1845 and the inner ring retainer 1852, and the clearance Δ1 is defined between the nut 1845 and the sleeve 1650. Therefore, the first buffer 1635 or the second buffer By giving elastic deformation to the body 1835, the nut 1845 can be moved in the axial direction, thereby enhancing the above-described buffering effect. Further, since the deflectors 1845b provided at both ends of the main body 1845a of the nut 1845 are suppressed by the first buffer 1635 and the second buffer 1835, when the ball 1065 comes into contact with the deflector 1845b during operation, the noise is It can also suppress and absorb vibrations.

  FIG. 27 is a cross-sectional view of main parts of an electric power steering apparatus 1911 according to the fourteenth embodiment. In this embodiment, only differences from the embodiment shown in FIG. 25 will be described, and the description of the common components will be omitted by attaching the same reference numerals.

  In this embodiment, instead of omitting the intermediate shaft, a toothed belt 1055 that engages with the gear portion 1037a of the drive shaft 1037 and the driven gear portion 1650a of the sleeve 1650 is provided. Accordingly, when the drive gear portion 1037a rotates together with the output shaft 1035a of the electric motor 1035, the driven gear portion 1650a is rotated at a predetermined reduction ratio via the toothed belt 1055. Accordingly, the sleeve 1650 and the nut 1845 also rotate, so that the power of the electric motor 1035 can be transmitted to the screw shaft 1023. A chain may be used instead of the toothed belt.

  In the embodiment described above, torque transmission may be performed by directly engaging the protrusions of the nut and the sleeve or the protrusions and the recesses without interposing the first buffer.

  FIG. 28 is a cross-sectional view of main parts of an electric power steering apparatus 2011 according to the fifteenth embodiment. FIG. 29 is a view of the configuration of FIG. 28 taken along the line XXIX-XXIX and viewed in the direction of the arrow, but the screw shaft and ball are omitted. In the present embodiment, only differences from the embodiment shown in FIG. 11 will be described, and the description of the common configuration will be omitted by attaching the same reference numerals.

  In the present embodiment, the nut and the sleeve are connected by a key. More specifically, in FIG. 29, a key groove 2045j extending in the axial direction is formed on the outer peripheral surface of the nut 2045, and a key extending in the axial direction is formed on the inner peripheral surface of the sleeve 2050 opposite thereto. A groove 2050f is formed. Since the prismatic key 2035 is disposed in the space formed by the key grooves 2045j and 2050f, torque can be transmitted from the sleeve 2050 to the nut 2045 using the shearing force of the key 2035.

  FIG. 30 is a cross-sectional view of main parts of an electric power steering apparatus 2111 according to the sixteenth embodiment. In the present embodiment, only differences from the embodiment shown in FIG. 28 will be described, and the description of the common configuration will be omitted by attaching the same reference numerals.

  In this embodiment, instead of omitting the intermediate shaft, a toothed belt 1055 that engages with the gear portion 1037a of the drive shaft 1037 and the driven gear portion 2050a of the sleeve 2050 is provided. Therefore, if the drive gear portion 1037a rotates together with the output shaft 1035a of the electric motor 1035, the driven gear portion 2050a is rotated at a predetermined reduction ratio via the toothed belt 1055. Accordingly, the sleeve 2050 and the nut 2045 also rotate, so that the power of the electric motor 1035 can be transmitted to the screw shaft 1023. A chain may be used instead of the toothed belt.

  FIG. 31 is a cross-sectional view of a main part of the electric power steering apparatus according to the seventeenth embodiment. 32 is a cross-sectional view of the assembly of the nut and the fixing member, and FIG. 33 is a view of the nut of FIG. 32 as viewed in the direction of arrow XXXIII.

  In FIG. 31, an electric power steering apparatus 3011 has a housing 3021 fixed to a vehicle body (not shown). The housing 3021 is divided into three parts in FIG. 31, and is integrated by bolting from the members 3021A, 3021B, and 3021C. A rack shaft 3023 is supported so as to be movable in the axial direction so as to penetrate the housing 3021 horizontally. Although not shown, a pinion is formed at the lower end of the input shaft connected to the steering wheel and meshes with the rack teeth of the rack shaft 3023. The rack shaft 3023 moves to the left and right in the figure by the rotation of the input shaft. It is supposed to be. Both ends of the rack shaft 3023 are connected to tie rods (not shown) of the steering mechanism.

  An electric motor (not shown) is attached to the housing 3021 so that the rack shaft 3023 and the axis are parallel to each other. The power of the electric motor is transmitted to an intermediate shaft 3038 that is only partially shown in FIG. The intermediate shaft 3038 is rotatably supported with respect to the housing 3021 by bearings 3024 and 3025, and has an intermediate gear portion 3038a at a portion sandwiched between the bearings 3024 and 3025.

  A nut 3045 is disposed around the rack shaft 3023 and is rotatably supported by the double-row angular ball bearing 3027 with respect to the housing 3021. This will be described more specifically. A thin cylindrical sleeve 3039 is disposed so as to fit into the inner hole 3021a in the member 3021A of the housing 3021. In addition, the ring-shaped member 3030, the first buffer member 3031, the outer ring 3027a of the double row angular ball bearing 3027, and the second buffer member 3032 are arranged in this order from the bottom surface (left side in FIG. 31) of the inner hole 3021a. It is fixed by a lock member 3033 to be joined. The first buffer member 3031 has an elastic body 3031 a that contacts the ring-shaped member 3030. Further, the second buffer member 3032 has an elastic body 3032 a that abuts against the lock member 3033. By elastically deforming the elastic bodies 3031a and 3032a, the double-row angular ball bearing 3027 can move in the axial direction together with the nut 3045 within a limited range. The outer ring 3027 a is fitted to the inner peripheral surface of the sleeve 3039.

  Inner rings 3027b, 3027b of the double-row angular ball bearing 3027 that are divided into two and arranged in the axial direction are fitted to the outer peripheral surface of the nut 3045, and the right end in the figure is the outer periphery formed in the vicinity of the right end of the nut 3045. It contacts the step 3045h. Further, the left end of the inner rings 3027b and 3027b is in contact with the right end of the screw member 3034, and preload is applied thereto. The screw member 3034 is screwed into a screw portion 3045k formed on the outer peripheral surface of the nut 3045. The preload can be adjusted by the screwing amount of the screw member 3034.

  In FIG. 32, a nut 3045 includes a central hollow cylindrical main body 3045a and deflectors 3045b at both ends. The main body 3045a forms a circulation path 3045c penetrating in the axial direction, and each deflector 3045b is a scooping piece for scooping up the ball 3065 that has been rolled up in the tangential direction and the lead angle direction of the rolling path and returning it to the circulation path 3045c. 3045d is formed. The screw shaft 3023, the nut 3045, and the ball 3065 constitute a ball screw mechanism (power transmission mechanism).

  In FIG. 32, a deflector 3045b is disposed at the left end of the main body 3045a of the nut 3045, and is fixed by a donut disk-shaped holding plate 3035 screwed to the main body 3045a by a screw 3036. On the other hand, a deflector 3045b is disposed at the right end of the main body 3045a of the nut 3045, and is fixed to the left end surface of a cylindrical fixing member 3047 screwed to the nut 3045 by four screws 3048. It is designed to rotate. As shown in FIG. 33, the end surface of the main body 3045a is a plane other than the periphery of the deflector 3045b. Therefore, screw holes 3045m into which the screws 3048 are screwed can be provided at arbitrary positions and numbers.

  In FIG. 32, a male serration portion 3047a is formed near the right end of the fixing member 3047. Since the fixing member 3047 is a separate body from the nut 3045, the outer diameter of the male serration portion 3047a can be arbitrarily set, and the degree of design freedom is increased.

  In FIG. 31, a hollow driven gear 3037, which is a driven member, is rotatably supported by bearings 3026 and 3029 at both ends with respect to the housing 3021 and has a driven gear portion 3037a meshing with the intermediate gear portion 3038a. And a female serration portion 3037b is formed on the inner periphery of the left end. The intermediate gear portion 3038a and the driven gear portion 3037a constitute a gear pair. The assembly of the nut 3045 and the like can be performed from the right side of the drawing with the members 3021A and 3021B of the housing 3021 removed.

  By engaging the female serration portion 3037b of the driven gear 3037 and the male serration portion 3047a of the fixed member 3047, the driven gear 3037 and the fixed member 3047 can move relative to each other in the axial direction, but cannot rotate relative to each other in the rotational direction. Connected. The reason why the driven gear 3037 and the fixed member 3047 can be moved relative to each other in the axial direction is to exhibit the buffering effect of the elastic bodies 3031a and 3032a.

  In FIG. 31, a male screw groove 3023b is formed in a part of the outer peripheral surface of the rack shaft 3023 that is integral with the screw shaft (may be connected as a separate part). A nut 3045 is disposed around the male screw groove 3023b, and a female screw groove 3045f is formed on the inner peripheral surface of the main body 3045a facing the male screw groove 3023b. In a spiral space (rolling path) formed by the male screw groove 3023b and the female screw groove 3045f, a large number of balls (rolling elements) 3065 are rotatably arranged.

  The operation of this embodiment will be described. Although not shown, when the driver rotates the steering wheel, the rotational force is transmitted to the input shaft. When the input shaft rotates, the rack teeth meshed with the pinion are pushed, the rack shaft 3023 moves in the axial direction, and the steering mechanism (not shown) is driven via the tie rod, so that the wheels are steered. ing.

  At this time, a torque sensor (not shown) detects the steering torque, and a CPU (not shown) supplies electric power to the electric motor according to the amount, so that the driven gear portion 3037a meshed with the intermediate gear portion 3038a It is rotated at a predetermined reduction ratio. Accordingly, rotational power is transmitted from the driven gear 3037 to the nut 3045 via the fixing member 3047, and the rotational motion of the nut 3045 is converted into the axial motion of the rack shaft 3023 via the ball 3065. The ball 3065 rolled to one end of the rolling path is picked up by the deflector 3045b and returned to the other end via the circulation path 3045c. An auxiliary steering force can be output using the axial force of the rack shaft 3023.

  In the electric power steering apparatus 3011 according to the present embodiment, the fixing member 3047 has both a function of fixing the deflector 3045b to the main body 3045a of the nut 3045 and a function of transmitting power from the driven gear 3037 to the nut 3045. As a result, the number of parts is reduced, the assemblability is improved, and further space saving can be achieved. Accordingly, since power is directly transmitted to the main body 3045a, there is no need to increase the outer diameter of the nut 3045, and no power is transmitted to the deflector 3045b, and deformation or breakage due to power transmission does not occur.

  FIG. 34 is a sectional view showing an electric power steering apparatus 3111 according to the eighteenth embodiment. In the present embodiment, only different points from the embodiment shown in FIGS. 31 to 33 will be described, and the description of the common configuration will be omitted by attaching the same reference numerals.

  In FIG. 34, an annular portion 3045g is coaxially formed on the right end surface of the main body 3045a of the nut 3045. On the other hand, a reduced diameter cylindrical portion 3047b having an outer diameter substantially matching the inner diameter of the annular portion 3045g is formed coaxially on the left end face of the fixing member 3047 facing it. Therefore, by fitting the reduced diameter cylindrical portion 3047b to the annular portion 3045g, the radial positioning of the both is achieved, that is, by connecting the main body 3045a and the fixing member 3047 coaxially, the runout of the nut 3045 at the time of high rotation is achieved. Turning around can be suppressed. The annular portion 3045g and the reduced diameter cylindrical portion 3047b constitute an inlay.

  FIG. 35 is a top view of a nut body according to another embodiment that can be used in the electric power steering apparatus shown in FIGS. 31 and 34. FIG. 36 shows the nut body shown in FIG. 37 is a view of the nut body shown in FIG. 36 taken along the line XXXVII-XXXVII and viewed in the direction of the arrow. FIG. 38 is a view of the nut body shown in FIG. It is the figure which cut | disconnected by the -XXXVIII line and looked at the arrow direction. FIG. 39 is a view showing a state in which a bearing is assembled to the main body of the nut, and FIG. 40 is a view of the configuration of FIG. 39 taken along line XXXX-XXXX and viewed in the direction of the arrow.

  As shown in FIGS. 35 and 37, a part of the circulation groove 3145c of the main body 3145a is opened (3145j) outward in the radial direction. In the main body 3045a shown in FIG. 33, the circulation path 3045c has to be processed with a long drill, and there is a problem that the processing time becomes long. On the other hand, in the present embodiment, since the elongated hole-shaped opening 3145j can be easily grooved by an end mill or the like, the processing time can be reduced and the cost can be reduced. The threaded portion 3145k formed on the outer peripheral surface of the nut 3145, the female thread groove 3145f, the connecting portion between the circulation path 3145c and the female thread groove 3145f, and the like can be easily processed from the axial direction as in the prior art.

  As shown in FIGS. 39 and 40, when the main body 3145a is assembled to the electric power steering apparatus, the opening 3145j is covered from the outside in the radial direction by the bearing 3027 applied to the step 3145h, so that the entire circumference is closed. Therefore, the ball 3065 does not escape outward through the opening 3145j. That is, it is not necessary to use a separate member to cover the opening 3145j, and the number of parts and cost can be reduced.

  However, since the opening 3145j is formed, rolling of the ball 3065 passing through the circulation path 3145c may be hindered. The following modification solves this problem.

  41 is a top view of a nut main body according to a modification, FIG. 42 is a view of the nut main body shown in FIG. 41 in the direction of arrow XXXXII, and FIG. 43 is a nut main body shown in FIG. Fig. 44 (a) is a view of the nut body shown in Fig. 43 cut along the XXXXIV-XXXXIV line and viewed in the arrow direction. FIG. 44B is a front view of the lid member assembled to the nut body. 45 is a view showing a state in which the bearing is assembled to the nut body, and is a cross-sectional view similar to FIG.

  This modification is different from the embodiment shown in FIGS. 35 to 40 in that a lid member 3150 covering (shielding) the opening 3145j and an opening step 3145s for attaching the lid member 3150 are formed in the main body 3145a ′. This is the point. About the common structure, description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  More specifically, as shown in FIGS. 41 and 44, the main body 3145a 'is formed with an opening step 3145s that is one step down from the outer periphery around the opening 3145j. The lid member 3150 includes a flange portion 3150a that is attached to the opening step portion 3145s to prevent falling into the opening 3145j, and a cylindrical groove 3150b formed on one surface of the flange portion 3150a. The cross-sectional shape (radius R) of the cylindrical groove 3150b is a shape corresponding to the cross-sectional shape (radius R) of the circulation groove 3145c, and it is preferable that the cross-section formed by them has an approximately circular shape with the radius R. That is, the space formed by the circulation groove 3145c and the lid member 3150 is a cylindrical hole formed by a drill. Further, the flange portion 3150a of the lid member 3150 has such a dimension that the outer surface of the lid member 3150 is flush with the outer peripheral surface of the main body 3145a 'when assembled to the main body 3145a'.

  As shown in FIG. 45, when the lid member 3150 is attached to the main body 3145a ′ and assembled to the electric power steering apparatus, the flange portion 3150a of the lid member 3150 is sandwiched and fixed between the opening step 3145s and the bearing 3027. Therefore, when the circulation ball 3065 passes through the circulation groove 3145c, the circulation ball 3065 does not come out through the opening 3145j, and the stepped portion generated by providing the opening 3145j by the cylindrical groove 3150b of the lid member 3150. Therefore, the ball 3065 can smoothly roll, and abnormal noise and vibration can be suppressed. Further, the lid member 3150 is prevented from being separated from the main body 3145a 'by the bearing 3027.

  FIG. 46 is a cross-sectional view showing an electric power steering apparatus 3211 using the modification shown in FIGS. The present embodiment differs from the embodiment shown in FIGS. 31 to 33 only in that the opening 3145j and the lid member 3150 are provided, and thus the description of the common configuration is omitted by attaching the same reference numerals. To do.

  FIG. 47 is a sectional view of an electric power steering apparatus 3311 according to the nineteenth embodiment. In the present embodiment, only differences from the embodiment shown in FIG. 46 will be described, and the description of the common configuration will be omitted by attaching the same reference numerals.

  In the present embodiment, instead of omitting the intermediate shaft, a toothed belt 3055 for transmitting power to the gear portion 3037a of the driven shaft 3037 is provided. Accordingly, the power from the electric motor (not shown) is transmitted to the driven shaft 3037 via the toothed belt 3055, and the nut 3145 connected to this rotates, so that the power of the electric motor is transmitted to the screw shaft 3023. Can do. A chain may be used instead of the toothed belt. Such a belt or chain can also be used in the embodiment shown in FIGS.

  FIG. 48 is a cross-sectional view of a main part of the electric power steering apparatus according to the twentieth embodiment. In FIG. 48, an electric power steering apparatus 4011 has a housing 4021 fixed to a vehicle body (not shown). The housing 4021 is divided into three parts in FIG. 48 and integrated by bolting from the members 4021A, 4021B, and 4021C. A rack shaft 4023 is supported so as to be movable in the axial direction so as to penetrate the housing 4021 horizontally. Although not shown, a pinion is formed at the lower end of the input shaft connected to the steering wheel and meshes with the rack teeth of the rack shaft 4023, and the rack shaft 4023 moves to the left and right in the figure by the rotation of the input shaft. It is supposed to be. Both ends of the rack shaft 4023 are connected to tie rods (not shown) of the steering mechanism.

  An electric motor (not shown) is attached to the housing 4021 so that the rack shaft 4023 and the axis are parallel to each other. The power of the electric motor is transmitted to an intermediate shaft 4038 that is only partially shown in FIG. The intermediate shaft 4038 is rotatably supported with respect to the housing 4021 by bearings 4024 and 4025, and has an intermediate gear portion 4038a at a portion sandwiched between the bearings 4024 and 4025.

  A nut 4045 is disposed around the rack shaft 4023, and is rotatably supported with respect to the housing 4021 by a double row angular ball bearing 4027. This will be described more specifically. A thin cylindrical sleeve 4039 is disposed so as to fit into the inner hole 4021a of the member 4021A of the housing 4021. Further, in order from the bottom surface of the inner hole 4021a (the left side in FIG. 48), a ring-shaped member 4030, a first buffer member 4031, an outer ring 4027a of a double row angular ball bearing 4027, and a second buffer member 4032 are arranged and screwed into the member 4021A. It is fixed by a lock member 4033 to be joined. The first buffer member 4031 has an elastic body 4031 a that contacts the ring-shaped member 4030. Further, the second buffer member 4032 has an elastic body 4032 a that abuts against the lock member 4033. By elastically deforming the elastic bodies 4031a and 4032a, the double-row angular ball bearing 4027 can move in the axial direction together with the nut 4045 within a limited range. The outer ring 4027 a is fitted to the inner peripheral surface of the sleeve 4039.

  FIG. 49 is a cross-sectional view showing the nut of the electric power steering apparatus according to the present embodiment in an assembled state. Inner rings 4027b and 4027b of the double-row angular ball bearing 4027 which are divided into two and arranged in the axial direction are fitted to the outer peripheral surface of the nut 4045, and the right end in the figure is the outer periphery formed in the vicinity of the right end of the nut 4045. It contacts the step 4045h. Further, the left ends of the inner rings 4027b and 4027b are in contact with the right end of a screw member 4034 which is a fastening means for fixing the bearing, and preload is applied thereto. The screw member 4034 includes a cylindrical portion 4034a that is screwed into a screw portion 4045k formed on the outer peripheral surface of the nut 4045, and a flange portion 4034b that extends radially inward from the left end of the cylindrical portion 4034a, and the cylindrical portion 4034a. The preload can be adjusted by the amount of screwing. The flange portion 4034b is in contact with and fixes a deflector 4045b on the left side in the drawing via a ring-shaped elastic body (made of rubber or resin) 4046. Since the elastic body 4046 can be elastically deformed within a certain range by being pressed, there is no particular problem even if the screw member 4034 is fastened with priority given to the preload of the double-row angular ball bearing 4027.

  In FIG. 48, the right deflector 4045b in the drawing of the nut 4045 is fixed by a spline member 4035 screwed to the right end of the nut 4045 on the inner side in the radial direction of the lock member 4033. The spline member 4035 is spline-coupled to a driven gear 4037 that is spaced apart in the axial direction with respect to the nut 4045, and the shock-absorbing effect of the buffer members 4031 and 4032 is obtained when an impact force is generated in the power transmission path. The relative movement between the nut 4045 and the driven gear 4037 is made possible so that it can be exhibited.

  The driven gear 4037 is rotatably supported at both ends by bearings 4026 and 4029 with respect to the housing 4021 and has a driven gear portion 4037a meshing with the intermediate gear portion 4038a. The intermediate gear portion 4038a and the driven gear portion 4037a constitute a gear pair. The assembly of the nut 4045 and the like can be performed from the right side of the drawing with the members 4021A and 4021B of the housing 4021 removed.

  The nut 4045 includes a central hollow cylindrical main body 4045a and deflectors 4045b at both ends. The main body 4045a forms a circulation path 4045c penetrating in the axial direction, and each deflector 4045b is a scooping piece for scooping up the ball 4065 that has been rolled up in the tangential direction and the lead angle direction of the rolling path and returning it to the circulation path 4045c. 4045d is formed.

  A male screw groove 4023b is formed in a part of the outer peripheral surface of the rack shaft 4023 that is integral with the screw shaft (may be connected as a separate part). A nut 4045 is disposed around the male screw groove 4023b, and a female screw groove 4045f is formed on the inner peripheral surface of the main body 4045a facing the male screw groove 4023b. In a spiral space (rolling path) formed by the male screw groove 4023b and the female screw groove 4045f, a large number of balls (rolling elements) 4065 are rotatably arranged. The rack shaft (screw shaft) 4023, the nut 4045, and the ball 4065 constitute a ball screw mechanism (power transmission mechanism).

  The operation of this embodiment will be described. Although not shown, when the driver rotates the steering wheel, the rotational force is transmitted to the input shaft. When the input shaft rotates, the rack teeth meshed with the pinion are pushed, the rack shaft 4023 moves in the axial direction, and the steering mechanism (not shown) is driven via the tie rod, so that the wheels are steered. ing.

  At this time, a torque sensor (not shown) detects the steering torque, and a CPU (not shown) supplies electric power to the electric motor according to the amount, so that the driven gear portion 4037a meshed via the intermediate gear portion 4038a It is rotated at a predetermined reduction ratio. Accordingly, the nut 4045 connected to the driven gear 4037 via the spline member 4035 also rotates, and this rotational motion is converted to the axial motion of the rack shaft 4023 via the ball 4065. The ball 4065 that has rolled to one end of the rolling path is picked up by the deflector 4045b and returned to the other end via the circulation path 4045c. The auxiliary steering force can be output using the axial force of the rack shaft 4023.

  In the electric power steering apparatus 4011 according to the present embodiment, the left deflector 4045b in the drawing is fixed to the nut 4045 by using a screw member 4034 that fixes a double-row angular ball bearing 4027 that supports the nut 4045. Therefore, the number of parts required for assembling is reduced, and assembling becomes easy. Further, since the elastic body 4046 is interposed between the deflector 4045b and the screw member 4034, the elastic body 4046 can reduce vibration and noise when the ball 4065 collides with the deflector 4045b during operation. .

  FIG. 50 is a cross-sectional view showing the nut of the electric power steering apparatus according to the twenty-first embodiment in an assembled state. In the present embodiment, only differences from the embodiment shown in FIGS. 48 and 49 will be described, and the description of the common components will be omitted by attaching the same reference numerals.

  In the present embodiment, instead of omitting the elastic body, a hemispherical protrusion 4045g provided on the deflector 4045b is brought into contact with the flange portion 4034b of the screw member 4034. Since the protrusion 4045g can be elastically deformed within a certain range by being pressed, it is preferable that the protrusion 4045g be formed slightly larger and assembled while being elastically deformed when preload is applied to the double row angular ball bearing 4027.

  FIG. 51 is a cross-sectional view of main parts of an electric power steering apparatus according to a twenty-second embodiment. 52 is a cross-sectional view of the nut alone, FIG. 53 is a view of the nut of FIG. 52 as viewed in the direction of the arrow XXXXXIII, and FIG. 54 is an exploded perspective view of the nut and the driven gear.

  In FIG. 51, an electric power steering apparatus 5011 has a housing 5021 fixed to a vehicle body (not shown). The housing 5021 is divided into three parts in FIG. 51 and integrated from the members 5021A, 5021B, and 5021C by bolting. A rack shaft 5023 is supported so as to be movable in the axial direction so as to penetrate the housing 5021 horizontally. Although not shown, a pinion is formed at the lower end of the input shaft connected to the steering wheel and meshes with the rack teeth of the rack shaft 5023. The rack shaft 5023 moves to the left and right in the figure by the rotation of the input shaft. It is supposed to be. Both ends of the rack shaft 5023 are connected to tie rods (not shown) of the steering mechanism.

  An electric motor (not shown) is attached to the housing 5021 so that the rack shaft 5023 and the axis are parallel to each other. The power of the electric motor is transmitted to an intermediate shaft 5038 that is only partially shown in FIG. The intermediate shaft 5038 is rotatably supported with respect to the housing 5021 by bearings 5024 and 5025, and has an intermediate gear portion 5038a at a portion sandwiched between the bearings 5024 and 5025.

  A nut 5045 is disposed around the rack shaft 5023 and is rotatably supported with respect to the housing 5021 by a double row angular ball bearing 5027. This will be described more specifically. A thin cylindrical sleeve 5039 is disposed so as to fit into the inner hole 5021a of the member 5021A of the housing 5021. Also, in order from the bottom surface of the inner hole 5021a (left side in FIG. 51), a ring-shaped member 5030, a first buffer member 5031, an outer ring 5027a of a double row angular ball bearing 5027, and a second buffer member 5032 are arranged and screwed into the member 5021A. It is fixed by a lock member 5033 to be joined. The first buffer member 5031 has an elastic body 5031 a that contacts the ring-shaped member 5030. The second buffer member 5032 has an elastic body 5032 a that abuts against the lock member 5033. By elastically deforming the elastic bodies 5031a and 5032a, the double-row angular ball bearing 5027 can move in the axial direction together with the nut 5045 within a limited range. The outer ring 5027 a is fitted to the inner peripheral surface of the sleeve 5039.

  The inner rings 5027b and 5027b of the double row angular ball bearing 5027 which are divided into two and arranged in the axial direction are fitted to the outer peripheral surface of the nut 5045, and the left end in the figure is the outer peripheral step formed at the left end of the nut 5045. It is in contact with the portion 5045h. Further, the right ends of the inner rings 5027b and 5027b are in contact with the left end of the screw member 5034, and preload is applied thereto. The screw member 5034 is screwed into a screw portion 5045k formed on the outer peripheral surface of the nut 5045. The preload can be adjusted by the screwing amount of the screw member 5034.

  The nut 5045 includes a central hollow cylindrical main body 5045a and deflectors 5045b (only one is shown in FIG. 51) at both ends. The main body 5045a forms a circulation path 5045c penetrating in the axial direction, and each deflector 5045b is a scooping piece for scooping the ball 5065 that has rolled up in the tangential direction and the lead angle direction of the rolling path and returning it to the circulation path 5045c. 5045d is formed. The screw shaft 5023, the nut 5045, and the ball 5065 constitute a ball screw mechanism (power transmission mechanism).

  In FIG. 52, four prismatic protrusions 5045j project in the axial direction at 90 ° intervals in the circumferential direction (see FIG. 53) on the right end surface of the main body 5045a of the nut 5045 (extend from the end surface in the axial direction). Formed). As shown in FIG. 53, the circulation path 5045c is arranged between the two protrusions 5045j, and the deflector 5045b is attached thereto, so that the protrusion 5045j does not become an obstacle to the arrangement.

  In FIG. 51, a hollow driven gear 5037 as a driven member is rotatably supported at both ends by bearings 5026 and 5029 with respect to the housing 5021 and has a driven gear portion 5037a meshing with the intermediate gear portion 5038a. ing. The intermediate gear portion 5038a and the driven gear portion 5037a constitute a gear pair. The nut 5045 and the like can be assembled from the right side of the drawing with the members 5021A and 5021B of the housing 5021 removed.

  54, four prismatic protrusions 5037b are formed to protrude in the axial direction from the end face of the driven gear 5037 at intervals of 90 degrees so as to face the main body 5045a of the nut 5045. Between the main body 5045a and the driven gear 5037, a ring-shaped elastic body (made of rubber or resin) 5035 is disposed. The elastic body 5035 forms eight groove portions 5035a at intervals of 45 degrees in the circumferential direction. The shape of the groove 5035a corresponds to the protrusions 5045j and 5037b.

  When assembled, the protrusion 5045j of the main body 5045a passes through the groove 5035a of the elastic body 5035, and the protrusion 5037b of the driven gear 5037 passes through the remaining groove 5035a of the elastic body 5035. That is, the elastic body 5035 is positioned between the protrusions 5045j and 5037b alternately arranged in the circumferential direction. It should be noted that the tip of the protrusion 5045j does not contact the opposite end surface of the driven gear 5037 and the tip of the protrusion 5037b does not contact the opposite end surface of the main body 5045a so that the buffering members 5031 and 5032 can exhibit the buffering effect. It is preferable to arrange them with a gap.

  In FIG. 51, a male screw groove 5023b is formed in a part of the outer peripheral surface of the rack shaft 5023 that is integral with the screw shaft (may be connected as a separate part). A nut 5045 is disposed around the male screw groove 5023b, and a female screw groove 5045f is formed on the inner peripheral surface of the main body 5045a facing the male screw groove 5023b. In a spiral space (rolling path) formed by the male screw groove 5023b and the female screw groove 5045f, a large number of balls (rolling elements) 5065 are arranged to roll freely.

  The operation of this embodiment will be described. Although not shown, when the driver rotates the steering wheel, the rotational force is transmitted to the input shaft. When the input shaft rotates, the rack teeth meshed with the pinion are pushed, the rack shaft 5023 moves in the axial direction, and the steering mechanism (not shown) is driven through the tie rod, so that the wheels are steered. ing.

  At this time, a torque sensor (not shown) detects the steering torque, and a CPU (not shown) supplies electric power to the electric motor in accordance with the amount, so that the driven gear portion 5037a meshed via the intermediate gear portion 5038a is It is rotated at a predetermined reduction ratio. Accordingly, rotational power is transmitted from the driven gear 5037 to the nut 5045 through the elastic body 5035, and the rotational motion of the nut 5045 is converted into the axial motion of the rack shaft 5023 through the ball 5065. The ball 5065 that has rolled to one end of the rolling path is picked up by the deflector 5045b and returned to the other end via the circulation path 5045c. An auxiliary steering force can be output using the axial force of the rack shaft 5023.

  In the electric power steering apparatus 5011 according to the present embodiment, a projection 5045j extending in the axial direction is provided on the end surface of the main body 5045a of the nut 5045, and the power of the electric motor is transmitted through this. Therefore, power transmission is possible without increasing the outer diameter of the nut 5045. Further, since power is directly transmitted to the main body 5045a, no power is transmitted to the deflector 5045b, and deformation or breakage due to power transmission does not occur.

  Furthermore, power transmission is transmitted from the projection 5037b of the driven gear 5037 via the elastic body to the projection 5045j. Therefore, compared to the case where the projections 5045j and 5037b are in direct contact with each other, it is possible to prevent the occurrence of hitting sound and play backlash. It can also be eliminated.

  In addition, the shape of the protrusion of the nut and the protrusion of the driven gear is not limited to a prismatic shape, and may be a cylindrical shape or a pyramid shape. Also, a recess recessed in the axial direction from the end surface of the nut may be provided, and the protrusion of the driven gear may be engaged therewith, or a similar recess may be provided in the driven gear and the protrusion of the nut engaged therewith. Good. For power transmission from the electric motor to the nut, a toothed belt or a chain may be used instead of the gear pair.

  As described above, the present invention has been described in detail with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be appropriately changed and improved without departing from the spirit thereof. Of course there is. The present invention is also applicable to a so-called steer-by-wire (SBW) type steering mechanism in which a steering wheel and a rack shaft are not mechanically connected, a rear wheel steering mechanism used in a four-wheel steering (4WS) vehicle, and the like. .

It is principal part sectional drawing of the electric power steering apparatus 11 concerning 1st Embodiment. It is the figure which cut | disconnected the nut of FIG. 1 by the II-II line | wire, and looked at the arrow direction. It is principal part sectional drawing of the electrically driven power steering apparatus 111 concerning 2nd Embodiment. It is a figure which expands and shows the site | part shown by arrow IV of the structure of FIG. FIG. 5 is a view of the configuration of FIG. 4 taken along the line VV and viewed in the direction of the arrow. It is principal part sectional drawing of the electrically driven power steering apparatus 211 concerning 3rd Embodiment. FIG. 7 is an exploded view of the nut and the driven gear. FIG. 8 is a view seen in the axial direction with the deflector removed from the nut. It is a schematic sectional drawing of an end cap type ball screw mechanism. It is principal part sectional drawing of the electrically driven power steering apparatus 311 concerning 4th Embodiment. It is principal part sectional drawing of the electrically driven power steering apparatus concerning 5th Embodiment. FIG. 12A is an axial sectional view of the ball screw mechanism according to the sixth embodiment, and FIG. 12B is an arrow obtained by cutting the nut of FIG. 12A along the line XIIB-XIIB. It is the figure seen in the direction. FIG. 13A is a sectional view in the axial direction of the ball screw mechanism according to the seventh embodiment, and FIG. 13B is an arrow formed by cutting the nut of FIG. 13A along the line XIIIB-XIIIB. It is the figure seen in the direction. It is an axis orthogonal cross section of the ball screw mechanism concerning a modification. It is an axis orthogonal cross section of the ball screw mechanism concerning a modification. It is an axial cross-sectional view of the ball screw mechanism according to the eighth embodiment. It is a sectional view in the direction perpendicular to the axis of a ball screw mechanism according to a ninth embodiment. It is an axis orthogonal cross section of the ball screw mechanism concerning a modification. It is an axis orthogonal cross section of the ball screw mechanism concerning a modification. It is principal part sectional drawing of the electrically driven power steering apparatus 1511 concerning 10th Embodiment. It is principal part sectional drawing of the electrically driven power steering apparatus 1611 concerning 11th Embodiment. It is a disassembled perspective view of the nut and sleeve concerning 11th Embodiment. Fig.23 (a) is a figure which shows the end surface of the nut concerning this Embodiment, FIG.23 (b) cut | disconnected the structure of Fig.23 (a) by the XXIIIB-XXIIIB line | wire and looked at the arrow direction. FIG. 23 (c) is a diagram showing a deflector. It is principal part sectional drawing of the electrically driven power steering apparatus 1711 concerning 12th Embodiment. It is principal part sectional drawing of the electrically driven power steering apparatus 1811 concerning 13th Embodiment. It is a disassembled perspective view which shows the nut and inner ring restraint concerning 13th Embodiment. It is principal part sectional drawing of the electrically driven power steering apparatus 1911 concerning 14th Embodiment. It is principal part sectional drawing of the electrically driven power steering apparatus 2011 concerning 15th Embodiment. It is the figure which cut | disconnected the structure of FIG. 28 along the XXIX-XXIX line | wire and looked at the arrow direction. It is principal part sectional drawing of the electrically driven power steering apparatus 2111 concerning 16th Embodiment. It is principal part sectional drawing of the electrically driven power steering apparatus 3011 concerning 17th Embodiment. It is assembly sectional drawing of a nut and a fixing member. It is the figure which looked at the nut of FIG. 32 in the arrow XXXIII direction. It is principal part sectional drawing of the electrically driven power steering apparatus 3111 concerning 18th Embodiment. FIG. 35 is a top view of a nut body according to another embodiment that can be used in the electric power steering apparatus shown in FIGS. 31 and 34. It is the figure which looked at the main body of the nut shown in FIG. 35 in the arrow XXXVI direction. It is the figure which cut | disconnected the main body of the nut shown in FIG. 36 by the XXXVII-XXXVII line, and looked at the arrow direction. It is the figure which cut | disconnected the main body of the nut shown in FIG. 37 by the XXXVIII-XXXVIII line | wire, and looked at the arrow direction. It is a figure shown in the state which assembled | attached the bearing to the main body of a nut. It is the figure which cut | disconnected the structure of FIG. 39 by the XXXX-XXXX line | wire, and looked at the arrow direction. It is a top view of the main body of the nut concerning a modification. It is the figure which looked at the main body of the nut shown in FIG. 41 in the arrow XXXXII direction. It is the figure which cut | disconnected the main body of the nut shown in FIG. 42 by the XXXXIII-XXXXIII line | wire, and looked at the arrow direction. 44 (a) is a view of the nut body shown in FIG. 43 taken along the line XXXXIV-XXXXIV and viewed in the direction of the arrow, and FIG. 44 (b) is a front view of the lid member assembled to the nut body. is there. It is a figure shown in the state where the bearing was attached to the main part of the nut concerning this modification, and is a sectional view similar to FIG. It is sectional drawing which shows the electric power steering apparatus 3211 using the modification shown to FIGS. It is sectional drawing of the electrically driven power steering apparatus 3311 concerning 19th Embodiment. It is principal part sectional drawing of the electrically driven power steering apparatus 4011 concerning 20th Embodiment. It is sectional drawing which shows the nut of the electrically driven power steering apparatus concerning 20th Embodiment in an assembly state. It is sectional drawing which shows the nut of the electrically driven power steering apparatus concerning 21st Embodiment in an assembly state. It is principal part sectional drawing of the electrically driven power steering apparatus 5011 concerning 22nd Embodiment. It is sectional drawing of a nut single-piece | unit. It is the figure which looked at the nut of FIG. 52 in the arrow XXXXXIII direction. It is a disassembled perspective view of a nut and a driven gear.

Explanation of symbols

11-5011 Electric power steering device 23-5023 Screw shaft (rack shaft)
45-5045 Nut 45b-5045b Deflector 65-5065 Ball

Claims (35)

An electric motor;
A rack shaft coupled to a steering mechanism, and a power transmission mechanism for transmitting power from the electric motor to the rack shaft,
The power transmission mechanism is connected to or integrated with the rack shaft and includes a male screw groove, a nut disposed around the screw shaft and provided with a female screw groove, the male screw groove, and the screw shaft. A plurality of rolling elements capable of rolling in a rolling path formed between the female screw groove and
The nut includes a main body provided with a circulation path for the rolling elements extending in an axial direction, a rolling element provided at both ends of the main body and rolling on the rolling paths, in a tangential direction and a lead angle of the rolling path. An electric power steering apparatus comprising a deflector that scoops up in a direction and returns to the circulation path.   2. The electric power steering apparatus according to claim 1, wherein the nut is provided with a receiving portion that receives power transmitted from the electric motor, radially outward of the rolling path.   The electric power steering apparatus according to claim 2, wherein the receiving portion is a gear portion formed on an outer peripheral surface of the nut.   The electric power steering apparatus according to claim 3, wherein the gear portion meshes with another gear.   The electric power steering apparatus according to claim 3, wherein the gear portion is engaged with a toothed belt.   The deflector is fixed to the nut using an annular fixing member press-fitted into the nut, and the fixing member has a female serration portion that engages with a male serration portion of an external member, The electric power steering apparatus according to any one of claims 1 to 5, wherein power transmission is performed through the engaged male serration portion and the female serration portion. An electric motor;
A rack shaft coupled to a steering mechanism, and a power transmission mechanism for transmitting power from the electric motor to the rack shaft,
The power transmission mechanism is connected to or integrated with the rack shaft and includes a male screw groove, a nut disposed around the screw shaft and provided with a female screw groove, the male screw groove, and the screw shaft. A plurality of rolling elements capable of rolling in a rolling path formed between the female screw groove and a sleeve having a receiving portion for receiving power transmitted from the electric motor;
The electric power steering characterized in that the nut is inserted and fixed with respect to the sleeve so that the receiving portion is located radially outward of the rolling path and is rotated integrally. apparatus.   The nut includes a main body provided with a circulation path for the rolling elements extending in an axial direction, a rolling element provided at both ends of the main body and rolling on the rolling paths, in a tangential direction and a lead angle of the rolling path. The electric power steering apparatus according to claim 7, comprising a deflector that scoops up in a direction and returns to the circulation path.   The electric power steering apparatus according to claim 7 or 8, wherein the nut is fitted and fixed to the sleeve.   The electric power steering apparatus according to claim 7 or 8, wherein the nut is serrated to the sleeve.   The electric power steering apparatus according to claim 7 or 8, wherein an elastic body is interposed between the nut and the sleeve.   A convex portion is provided on the outer peripheral surface of the nut, a concave portion is provided on the inner peripheral surface of the sleeve, and the nut is engaged with the sleeve so that the convex portion is engaged with the concave portion. The electric power steering apparatus according to claim 7 or 8, wherein   The electric power steering apparatus according to claim 12, wherein at least a part of the convex portion is provided radially outward of the circulation path of the main body.   The electric power steering apparatus according to claim 12 or 13, wherein a buffer member is disposed between the convex portion and the concave portion in the circumferential direction.   The nut and the sleeve have protrusions extending in an axial direction, respectively, and the first buffer is disposed between the protrusions of the nut and the sleeve. The electric power steering apparatus as described.   9. The electric type according to claim 7, wherein one of the nut and the sleeve has a protrusion extending in the axial direction, and the other has a recess that engages with the protrusion. Power steering device.   The electric power steering apparatus according to claim 16, wherein the first buffer is disposed between the protrusion and the recess.   18. The electric motor according to claim 15, wherein a gap that is reduced by relative movement in a direction in which the first buffer is compressed is provided between the nut and the sleeve. Power steering device.   19. The screw according to claim 7, further comprising: a screw member that is screwed onto an inner periphery of the sleeve, wherein a second buffer body is disposed between the screw member and the nut. Electric power steering device.   The electric power steering apparatus according to claim 19, wherein a gap that is reduced by relative movement in a direction in which the second buffer body is compressed is provided between the nut and the screw member. .   The electric power steering apparatus according to claim 7 or 8, wherein the nut and the sleeve are connected by a key and rotate integrally.   The electric power steering apparatus according to any one of claims 7 to 21, wherein the receiving portion is a gear portion formed on an outer peripheral surface of the sleeve.   The electric power steering apparatus according to claim 22, wherein the gear portion is engaged with another gear.   The electric power steering apparatus according to claim 22, wherein the gear portion is engaged with a toothed belt. An electric motor;
A rack shaft coupled to a steering mechanism, and a power transmission mechanism for transmitting power from the electric motor to the rack shaft,
The power transmission mechanism is connected to or integrated with the rack shaft and includes a male screw groove, a nut disposed around the screw shaft and provided with a female screw groove, the male screw groove, and the screw shaft. A plurality of rolling elements capable of rolling in a rolling path formed between the female screw groove and
The nut includes a main body provided with a circulation path for the rolling elements extending in an axial direction, a rolling element provided at both ends of the main body and rolling on the rolling paths, in a tangential direction and a lead angle of the rolling path. Consisting of a deflector that scoops up in the direction and returns to the circuit,
An electric power steering apparatus, wherein power of the electric motor is transmitted to the nut through a fixing member that fixes the deflector to the nut.   26. The electric power steering apparatus according to claim 25, wherein the deflector is pressed against the nut at an end surface of the fixing member.   27. The electric power steering apparatus according to claim 25 or 26, wherein the nut and the fixing member are positioned by an inlay.   The electric power steering apparatus according to any one of claims 25 to 27, wherein at least a part of the circulation path is formed by grooving the main body from a radial direction.   29. The electric power steering apparatus according to claim 28, wherein a bearing is disposed radially outward of the processed groove.   30. The electric power steering apparatus according to claim 29, wherein a lid member that shields at least a part of the circulation path is disposed between the groove and the bearing. An electric motor;
A rack shaft coupled to a steering mechanism, and a power transmission mechanism for transmitting power from the electric motor to the rack shaft,
The power transmission mechanism is connected to or integrated with the rack shaft and includes a male screw groove, a nut disposed around the screw shaft and provided with a female screw groove, the male screw groove, and the screw shaft. A plurality of rolling elements capable of rolling in a rolling path formed between the female screw groove and
The nut includes a main body provided with a circulation path for the rolling elements extending in an axial direction, a rolling element provided at both ends of the main body and rolling on the rolling paths, in a tangential direction and a lead angle of the rolling path. Consisting of a deflector that scoops up in the direction and returns to the circuit,
The electric power steering apparatus, wherein the deflector is attached to the nut by fastening means for fixing a bearing that supports the nut.   32. The electric power steering apparatus according to claim 31, wherein an elastic body is interposed between the deflector and the fastening means.   32. The electric power steering apparatus according to claim 31, wherein a protrusion is provided on the deflector and the fastening means is brought into contact with the protrusion to be fixed. An electric motor;
A rack shaft coupled to a steering mechanism, and a power transmission mechanism for transmitting power from the electric motor to the rack shaft,
The power transmission mechanism is connected to or integrated with the rack shaft and includes a male screw groove, a nut disposed around the screw shaft and provided with a female screw groove, the male screw groove, and the screw shaft. A plurality of rolling elements capable of rolling in a rolling path formed between the female screw groove and
The nut includes a main body provided with a circulation path for the rolling elements extending in an axial direction, a rolling element provided at both ends of the main body and rolling on the rolling paths, in a tangential direction and a lead angle of the rolling path. Consisting of a deflector that scoops up in the direction and returns to the circuit,
An electric power characterized in that a projection extending at least in the axial direction from the end surface or a recess recessed in the axial direction is formed on an end surface in the axial direction of the main body in order to transmit power of the electric motor. Steering device. 35. The electric power steering apparatus according to claim 34, wherein an elastic body is provided between a driven member that receives power from the electric motor and the protrusion or recess.

Images