JP2010036678A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of making the phase of a serration of an input shaft accurately coincide with the phase of a serration of an output shaft, and making the neutral state of a steering wheel accurately coincide with the neutral state on a wheel side, by the electric power steering device alone. <P>SOLUTION: So as to make the phases of chipped teeth 124 of a male serration 123 of a torque transmitting cylinder 12 and chipped teeth 233 of a male serration 231 of the output shaft 23 coincide with each other, the male serration 123 of the torque transmitting cylinder 12 is engaged with a female serration jig 75, and the male serration 231 of the output shaft 23 is engaged with a female serration jig 72. In this state, a slider 74 is descended to externally fit the torque transmitting cylinder 12 with a hollow shaft 11, and an inner diameter hole 121 of the torque transmitting cylinder 12 is serration pressed in a male serration 111 of the hollow shaft 11 to be engaged. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus that drives an electric motor to apply a required steering assist force to a steering gear.

  The electric power steering device connects the input shaft on the steering wheel side and the output shaft on the wheel side with a torsion bar, detects torsion of this torsion bar with a torque sensor, and detects the torque acting on the torsion bar from this detection result. Then, the electric motor is driven to give a required steering assist force to the output shaft.

  In such an electric power steering device, when the electric power steering device is attached to the vehicle body, in order to accurately match the neutral state of the handle and the neutral state of the wheel side, an input shaft to which the rotation of the handle is transmitted is transmitted. Therefore, it is necessary to match the phase of the male serration with the phase of the male serration of the output shaft that transmits the rotation to the wheel side with high accuracy.

  However, in the electric power steering apparatus, it is necessary to assemble so that the torque sensor is in a magnetic neutral state when the output shaft is assembled to the input shaft. When the input shaft and output shaft are assembled in this magnetic neutral state, the processing error of male serration of the input shaft and the processing error of male serration of the output shaft accumulate, and the phase of the male serration of the input shaft and the male of the output shaft A difference occurs in the phase of serration, and the difference between the neutral state of the steering wheel and the neutral state of the wheel side becomes large. The difference between the neutral position of the handle and the neutral position on the wheel side is difficult to understand with the round handle, but with the bar handle, the length in the left-right direction is long, so it is noticeably enlarged at the grips at both ends. Become.

  If the male serration of the input shaft and the male serration of the output shaft are machined with high precision by each part, when the output shaft is assembled to the input shaft, the phase of the male serration of the input shaft and the male of the output shaft By matching the phases of the serrations, the neutral state of the steering wheel and the neutral state of the wheel side can be accurately matched. However, the cutting process is not suitable for mass production, and the manufacturing cost increases. Also, male serration processing by rolling is suitable in terms of mass production and manufacturing cost, but it is difficult to manufacture male serration with high accuracy.

  In the electric power steering apparatus shown in Patent Document 1 and Patent Document 2, a tapered hole formed on the handle side is fitted to a taper shaft formed on the input shaft side of the electric power steering apparatus so that the handle is in a neutral state. The neutral state on the wheel side is matched accurately.

  However, in the electric power steering devices shown in Patent Literature 1 and Patent Literature 2, when the electric power steering device is attached to the vehicle body, an operation for accurately matching the neutral state of the handle with the neutral state on the wheel side is performed. Since it is necessary, the total assembly time of the vehicle body becomes longer. In addition, since the coupling between the taper shaft and the taper hole is caused by friction, if a large rotational torque is repeatedly applied to the handle, the joint between the taper shaft and the taper hole may become loose and the handle may idle.

JP 2006-256576 A JP 2006-256577 A

  According to the present invention, the electric power steering device alone can accurately match the phase of the serration of the input shaft and the phase of the serration of the output shaft so that the neutral state of the steering wheel and the neutral state of the wheel side can be accurately matched. It is an object of the present invention to provide an electric power steering device that is made possible.

  The above problem is solved by the following means. That is, the first invention is a gear housing, an output shaft that is rotatably supported by the gear housing and has a serration that transmits rotation to the wheel side, a hollow shaft that transmits rotation on the handle side to the output shaft, The shaft is fitted into an axial through hole formed in the hollow shaft, and one end in the axial direction is coupled to the end on the handle side of the hollow shaft with a pin, and the other end in the axial direction is engaged with the output shaft so that torque can be transmitted. A combined torsion bar, a torque sensor for detecting torque acting on the torsion bar, an electric motor for applying a predetermined steering assist force to the output shaft according to a detection value of the torque sensor, and an outer periphery of the hollow shaft. A hollow torque transmission cylinder that is press-fitted into and engaged with the male serration and has an inner diameter hole whose hardness is lower than that of the male serration of the hollow shaft, and is formed at the handle-side end of the torque transmission cylinder. Serration for transmitting rotation of the dollar, a bearing inserted between the gear housing and the torque transmission cylinder, and rotatably supporting the torque transmission cylinder, the hollow shaft and the torque transmission cylinder are The phase of the serration of the output shaft and the serration of the torque transmission cylinder are matched, and the inner diameter hole of the torque transmission cylinder is pressed and engaged with the male serration of the hollow shaft while being plastically deformed. This is an electric power steering device.

  According to a second aspect of the present invention, there is provided a gear housing, an output shaft rotatably supported by the gear housing, and having a serration that transmits rotation to a wheel side, a hollow shaft that transmits rotation on a handle side to the output shaft, and the hollow The shaft is fitted in an axial through hole formed in the shaft, one end in the axial direction is coupled to the end on the handle side of the hollow shaft with a pin, and the other end in the axial direction is engaged with the output shaft so as to transmit torque. A torsion bar, a torque sensor for detecting a torque acting on the torsion bar, an electric motor for applying a predetermined steering assist force to the output shaft in accordance with a detection value of the torque sensor, and press-fitting to the outer periphery of the hollow shaft. A hollow torque transmission cylinder having a female serration having a hardness higher than that of the outer periphery of the hollow shaft, a serration formed at the handle-side end of the torque transmission cylinder, to which the rotation of the handle is transmitted, A bearing interposed between the gear housing and the torque transmission cylinder and rotatably supporting the torque transmission cylinder, wherein the hollow shaft and the torque transmission cylinder include the serration of the output shaft and the torque transmission cylinder. The electric power steering apparatus is characterized in that the phases of the serrations are made to coincide with each other and the female serration of the torque transmission cylinder is press-fitted and engaged while plastically deforming the outer periphery of the hollow shaft.

  According to a third aspect of the invention, in the electric power steering apparatus of the first or second aspect of the invention, the outer periphery of the hollow shaft supports a press-fit load when a torque transmission cylinder is press-fitted into the hollow shaft. An electric power steering apparatus is characterized in that a stepped surface is formed.

  A fourth invention is formed in a gear housing, an input shaft having a serration that is inserted into the gear housing and to which the rotation of the handle is transmitted, a hollow shaft that transmits the rotation of the input shaft to the wheel side, and the hollow shaft A torsion bar which is fitted in the axial through hole, one end in the axial direction is coupled to the end of the hollow shaft on the wheel side by a pin, and the other end in the axial direction is engaged with the input shaft so that torque can be transmitted; A torque sensor that detects torque acting on the bar, a hollow torque transmission cylinder that is press-fitted into and engaged with the male serration formed on the outer periphery of the hollow shaft, and has an inner diameter hole that is lower in hardness than the male serration of the hollow shaft; A serration that is formed at the end of the torque transmission cylinder on the wheel side and transmits the rotation of the torque transmission cylinder to the wheel side, and a predetermined steering assist force according to the detected value of the torque sensor. An electric motor to be applied to the motor, and a bearing that is interposed between the gear housing and the torque transmission cylinder and rotatably supports the torque transmission cylinder. The hollow shaft and the torque transmission cylinder are provided on the input shaft. The electric type characterized in that the serration and the serration phase of the torque transmission cylinder coincide with each other, and the inner diameter hole of the torque transmission cylinder is press-fitted into the male serration of the hollow shaft while being plastically deformed. It is a power steering device.

  A fifth invention is formed in a gear housing, an input shaft having a serration that is inserted into the gear housing and transmits the rotation of the handle, a hollow shaft that transmits the rotation of the input shaft to the wheel side, and the hollow shaft A torsion bar which is fitted in the axial through hole, one end in the axial direction is coupled to the end of the hollow shaft on the wheel side by a pin, and the other end in the axial direction is engaged with the input shaft so that torque can be transmitted; Torque sensor for detecting torque acting on the bar, a hollow torque transmission cylinder that is press-fitted into and engaged with the outer periphery of the hollow shaft, and has a female serration that is harder than the outer periphery of the hollow shaft, the wheel side of the torque transmission cylinder An electric motor that provides a predetermined steering assist force to the torque transmission cylinder according to a detection value of the torque sensor, the serration for transmitting the rotation of the torque transmission cylinder to the wheel side, A bearing that is interposed between the housing and the torque transmission cylinder and rotatably supports the torque transmission cylinder. The hollow shaft and the torque transmission cylinder include the serration of the input shaft and the torque transmission cylinder. The electric power steering apparatus is characterized in that the phases of the serrations are matched, and the outer periphery of the hollow shaft is press-fitted and engaged with the female serrations of the torque transmission cylinder.

  According to a sixth aspect of the invention, in the electric power steering apparatus of the fourth or fifth aspect of the invention, the outer periphery of the hollow shaft supports a press-fitting load when a torque transmission cylinder is press-fitted into the hollow shaft. An electric power steering apparatus is characterized in that a stepped surface is formed.

  A seventh invention is the electric power steering device according to any one of the first to sixth inventions, wherein the handle is a bar handle.

  In the electric power steering apparatus of the present invention, an output shaft that is rotatably supported by the gear housing and has serrations that transmit rotation to the wheel side, a hollow shaft that transmits rotation on the handle side to the output shaft, and a hollow shaft A hollow torque transmission tube that is press-fitted into the outer periphery of the shaft, a serration that is formed at the handle-side end of the torque transmission tube, and is interposed between the gear housing and the torque transmission tube. And a bearing that rotatably supports the torque transmission cylinder, the serrations of the output shaft and the torque transmission cylinder are matched, and the torque transmission cylinder is press-fitted into and engaged with the outer periphery of the hollow shaft. Yes.

  In the electric power steering device of the present invention, the input shaft having a serration that is inserted into the gear housing and to which the rotation of the handle is transmitted, the hollow shaft that transmits the rotation of the input shaft to the wheel side, and the outer periphery of the hollow shaft A hollow torque transmission cylinder that is press-fitted with serrations, a serration that is formed at the wheel-side end of the outer periphery of the torque transmission cylinder, and transmits the rotation of the torque transmission cylinder to the wheel side, and between the gear housing and the torque transmission cylinder And a bearing that rotatably supports the torque transmission cylinder. The serrations of the input shaft and the torque transmission cylinder are matched, and the torque transmission cylinder is press-fitted into the outer periphery of the hollow shaft. Match.

  Therefore, with the electric power steering device alone, the phase of the serration on the input side and that on the output side match, and the neutral position of the steering wheel and the wheel can be matched with high accuracy.

  Further, since it is not necessary to process the serrations on the input side and the output side with high accuracy, the serration can be rolled, and the mass productivity and the manufacturing cost are excellent. Furthermore, since the torque transmission cylinder is press-fitted and coupled to the outer periphery of the hollow shaft, there is no risk of backlash or idling occurring at the conventional coupling portion between the tapered shaft and the tapered hole. Further, since the serration phases on the input side and the output side coincide with each other in the electric power steering device alone, the time for assembling to the vehicle body can be shortened compared to the conventional coupling of the taper shaft and the taper hole.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a gear housing portion of an electric power steering apparatus 20 according to an embodiment of the present invention. As shown in FIG. 1, the hollow shaft 11 and the output shaft 23 are arranged on the same central axis in the gear housing 21 of the electric power steering apparatus 20.

  The output shaft 23 is rotatably supported on the cover 22 by a bearing (deep groove radial ball bearing) 41. The cover 22 covers the left open end of the gear housing 21. The hollow shaft 11 and the output shaft 23 are connected by a torsion bar 24.

  A disc-shaped cored bar 52 is press-fitted near the right end of the output shaft 23, and a worm wheel 51 that meshes with the worm 53 is press-fitted into the outer periphery of the cored bar 52. The core metal 52 is press-fitted into the output shaft 23 by serration press-fitting (the male serration on the outer periphery of the right end of the output shaft 23 is hardened to increase the hardness, and the male serration is press-fitted into the inner diameter hole of the raw material of the core metal 52. The hole is plastically deformed). The worm 53 is rotationally driven by an electric motor (not shown). A male serration 231 is formed at the left end of the output shaft 23 (the wheel side at the front end of the vehicle body), and this male serration 231 is connected to a tie rod via a universal joint, an intermediate shaft, a steering gear, etc. (not shown), Steer a wheel (not shown). A female serration may be formed instead of the male serration 231 at the left end of the output shaft 23, and this female serration may be connected to the tie rod via a universal joint, an intermediate shaft, a steering gear, etc. (not shown).

  The torsion bar 24 is fitted in an axial through hole 114 formed in the hollow shaft 11. The torsion bar 24 is press-fitted into the output shaft 23 at its left end (wheel side at the front end of the vehicle body), and its right end (handle side at the rear end of the vehicle body) is connected to the right end of the hollow shaft 11 by a pin 25. ing.

  The press-fitting of the output shaft 23 and the torsion bar 24 is performed by serration press-fitting (hardening the male serration on the outer periphery of the torsion bar 24 to increase the hardness, and press-fitting the male serration of the torsion bar 24 into the inner diameter hole of the raw material of the output shaft 23 The inner diameter hole is plastically deformed). Further, the outer periphery of the torsion bar 24 is pivotally supported by the bush 26 at the left end of the axial through hole 114 of the hollow shaft 11.

  A torque sensor 61 that detects torque acting on the torsion bar 24 includes a sensor shaft portion 62, a detection coil 63, and a cylindrical member 64. The sensor shaft portion 62 is integrally formed at the left end of the hollow shaft 11 (the wheel side of the vehicle body front side end portion). The detection coil 63 has a gap with the gear housing 21, and is fixed to the gear housing 21 with a leaf spring press-fitted inside the gear housing 21. The cylindrical member 64 is disposed in a gap between the outer periphery of the sensor shaft portion 62 and the inner periphery of the detection coil 63.

  The cylindrical member 64 is fixed to the right end (end of the vehicle body rear side) of the output shaft 23 by caulking, and the sensor shaft portion 62 is formed with a plurality of ridges extending in the axial direction at equal intervals in the circumferential direction. Yes. In the cylindrical member 64, a plurality of rectangular windows are formed at equal intervals in the circumferential direction at positions facing the detection coil 63.

  A hollow torque transmission cylinder 12 is fitted on the hollow shaft 11. The torque transmission cylinder 12 is engaged with the hollow shaft 11 so that torque can be transmitted to the front side of the vehicle body (wheel side) with respect to the right end of the hollow shaft 11 (the coupling portion of the torsion bar 24 and the pin 25 of the hollow shaft 11). . The engagement between the torque transmission cylinder 12 and the hollow shaft 11 is achieved by the serration press-fitting of the inner diameter hole 121 of the torque transmission cylinder 12 and the male serration 111 of the hollow shaft 11 (hardening the male serration 111 of the hollow shaft 11 to increase the hardness, The male serration 111 is press-fitted into the inner diameter hole 121 of the raw material of the torque transmission cylinder 12, and the inner diameter hole 121 is plastically deformed). That is, the hollow shaft 11 and the torque transmission cylinder 12 are integrated by engaging with each other so that torque can be transmitted, and have a function of a conventional input shaft.

  Between the gear housing 21 and the torque transmission cylinder 12, two bearings (deep groove radial ball bearings) 42 and 43 that rotatably support the torque transmission cylinder 12 are provided in the axial direction of the torque transmission cylinder 12. It is inserted adjacent. The bearings 42 and 43 are disposed at an axial position between the torque transmission cylinder 12, the serration engaging portion of the hollow shaft 11, and the right end of the hollow shaft 11. When the torque transmission cylinder 12 is press-fitted into the hollow shaft 11, the outer diameter of the torque transmission cylinder 12 at the press-fitting portion expands. Therefore, the bearings 42 and 43 are preferably arranged at positions shifted from the press-fitting portion in the axial direction.

  A gap is formed between the inner periphery 122 of the torque transmission cylinder 12 and the outer periphery 112 of the hollow shaft 11. This gap is formed over the entire axial length from the serration engaging portion between the torque transmission cylinder 12 and the hollow shaft 11 to the right end of the hollow shaft 11. The gap between the inner periphery 122 of the torque transmission cylinder 12 and the outer periphery 112 of the hollow shaft 11 does not need to be formed from the serration engaging portion between the torque transmission cylinder 12 and the hollow shaft 11, and torque generated by the bearings 42 and 43 is not required. You may form over the full length of the axial direction from the axial support part of the transmission cylinder 12 to the right end of the hollow shaft 11. FIG.

  A male serration 123 is formed at the right end of the torque transmission cylinder 12 (the handle side of the rear end portion of the vehicle body). The male serration 123 may be a handle (round handle or bar handle) via a steering shaft (not shown). ) And the rotation of the handle is transmitted to the torque transmission cylinder 12. Instead of the male serration 123 at the right end of the torque transmission cylinder 12, a female serration may be formed, and this female serration may be connected to the handle via a steering shaft (not shown).

  When a large bending load is applied to the torque transmission cylinder 12, the torque transmission cylinder 12 is elastically deformed by this bending load. The gap between the inner periphery 122 of the torque transmission cylinder 12 and the outer periphery 112 of the hollow shaft 11 is set to be larger than the elastic deformation amount of the torque transmission cylinder 12. Therefore, no bending load acts on the hollow shaft 11 and the torsion bar 24, and the torsion of the torsion bar 24 accurately reflects the steering torque, so that an appropriate steering assist force can be applied to the output shaft 23. .

  When a large bending load is applied to the torque transmission cylinder 12, the torque transmission cylinder 12 is elastically deformed by the bending load, and an inclination is generated between the inner ring and the outer ring of the bearings 42 and 43. However, as shown in the embodiment of the present invention, if the torque transmission cylinder 12 is pivotally supported on the gear housing 21 by at least two bearings 42 and 43, the inner ring and the outer ring of the bearings 42 and 43 caused by bending load are provided. Since the inclination is small, the deformation of the torque transmission cylinder 12 is small, which is preferable.

  Further, bearings 42 and 43 that rotatably support the torque transmission cylinder 12 include serration engaging portions between the torque transmission cylinder 12 and the hollow shaft 11 and the right end of the hollow shaft 11 (the torsion bar 24 and the pin 25 of the hollow shaft 11). Are arranged at positions in the axial direction. Accordingly, the gear housing 21 is not enlarged, and an increase in weight and an increase in required space in the vehicle interior are suppressed, and the electric power steering apparatus can be reduced in size and weight.

  The assembly procedure of the electric power steering apparatus 20 of the present invention is as follows. FIG. 2 is a longitudinal sectional view showing a state before the torque transmission cylinder 12 is assembled to the hollow shaft 11 after the hollow shaft 11 is assembled to the output shaft 23. As shown in FIG. 2, first, the metal core 52 into which the worm wheel 51 is press-fitted, the torsion bar 24, and the cylindrical member 64 are press-fitted into the output shaft 23.

  Next, the hollow shaft 11 is externally fitted to the torsion bar 24, and the hollow shaft 11 is rotated relative to the output shaft 23, so that the phase between the protrusion on the surface of the sensor shaft portion 62 and the window of the cylindrical member 64 is reached. To a magnetically neutral state. The magnetic neutral state is detected by a master detection coil (not shown). In this magnetic neutral state, a pin hole 251 is processed in the hollow shaft 11 and the torsion bar 24, and the pin 25 is driven into the pin hole 251 to connect the hollow shaft 11 and the torsion bar 24.

  Next, the torque transmission cylinder 12 is assembled to the hollow shaft 11. FIG. 3 is a longitudinal sectional view showing a process of assembling the torque transmission cylinder 12 to the hollow shaft 11. 4 (1) is a longitudinal sectional view showing a coupling state between the male serration 123 of the torque transmitting cylinder 12 and the slide side of the press machine, and FIG. 4 (2) is a sectional view taken along line AA of FIG. 4 (1).

  FIG. 5A is a longitudinal sectional view showing a coupling state between the male serration 231 of the output shaft 23 and the bolster side of the press machine, and FIG. 5B is a sectional view taken along the line BB in FIG. 6 (1) is a longitudinal sectional view of the main part showing a state in which the assembly of the output shaft and the hollow shaft is normally set in the assembly jig of FIG. 3, and FIG. 6 (2) is the assembly jig of FIG. It is a longitudinal cross-sectional view of the principal part which shows the state which the assembly | attachment goods of the output shaft and the hollow shaft set in the axial direction.

  As shown in FIGS. 3 to 6, the torque transmission cylinder 12 and the hollow shaft 11 are assembled by a press machine. A female serration jig 72 and holding jigs 73A and 73B are attached to the upper surface of the bolster 71 at the lower part of the press machine. A female serration jig 75 is attached to the lower surface of the slide 74 at the top of the press machine.

  The female serration jig 72 fixed to the upper surface of the bolster 71 has a cylindrical shape, the female serration 721 is formed on the inner periphery, and can be engaged with the male serration 231 of the output shaft 23. The female serration jig 75 fixed to the upper slide 74 of the press machine has a cylindrical shape, and the female serration 751 is formed on the inner periphery, and can engage with the male serration 123 of the torque transmission cylinder 12. The female serration 721 and the female serration 751 are tightly fitted so as to reduce backlash when engaged with the male serration 231 and the male serration 123.

  The phases of the female serration 721 and the female serration 751 are matched with high accuracy, and the female serration jig 72 and the female serration jig 75 are fixed to the bolster 71 and the slide 74, respectively. This highly accurate phase alignment is performed by simultaneously engaging a female serration 721 and a female serration 751 with a master serration shaft in which male serration is processed with high accuracy at both ends in the axial direction.

As shown in FIGS. 4 and 5, the male serration 123 of the torque transmission cylinder 12 and the male serration 231 of the output shaft 23 are formed with tooth missing portions 124 and 233, respectively. As shown in FIG. 3, the male serration 123 of the torque transmitting cylinder 12 is engaged with the female serration jig 75 so that the phase of the tooth missing portions 124 and 233 coincide with each other, and the male serration 231 of the output shaft 23 is engaged.
Is engaged with the female serration jig 72. Missing teeth 124, 233 which are marks for phase alignment
Instead of this, the male serrations 123 and the male serrations 231 may be marked with valleys filled with valleys or markings.

  The holding jigs 73 </ b> A and 73 </ b> B support a load when the torque transmission cylinder 12 is press-fitted into the hollow shaft 11. That is, the holding jigs 73A and 73B have a shape in which a cylinder is divided into two vertically, and are movable in the left-right direction in FIG. 3 along the upper surface of the bolster 71. The outer periphery 112 of the hollow shaft 11 is moved in the left-right direction in FIG. Hold from.

  As shown in FIG. 6 (1), a step surface 115 is formed on the outer periphery 112 of the hollow shaft 11 below the male serration 111. In a state where the assembly of the output shaft 23 and the hollow shaft 11 is normally set on the holding jigs 73A and 73B, the holding jigs 73A and 73B are moved in the direction of arrow P (holding direction) in FIG. . Then, as shown in FIG. 6 (1), the holding surfaces 73A and 732B of the holding jigs 73A and 73B hold the outer periphery 112 of the hollow shaft 11, and the stepped surface 115 of the hollow shaft 11 becomes the holding jig 73A. It abuts on the upper surfaces 731A and 731B of 73B.

  Therefore, the press-fitting load when the torque transmission cylinder 12 is press-fitted into the hollow shaft 11 is supported by the step surface 115 and the upper surfaces 731A and 731B of the holding jigs 73A and 73B. For this reason, the hollow shaft 11 is not moved downward, and no load is applied to the torsion bar 24 during press-fitting, so the torsion bar 24 does not bend.

  As shown in FIG. 6 (2), the holding jig 73A, the assembled product of the output shaft 23 and the hollow shaft 11 is set so as to be shifted upward in the axial direction with respect to the holding jig 73A, 73B. 73B is moved in the direction of arrow P (holding direction) in FIG. Then, the outer periphery of the worm wheel 51 comes into contact with the small-diameter inner peripheral surfaces 733A and 733B of the holding jigs 73A and 73B to stop the holding jigs 73A and 73B from moving in the holding direction.

  Accordingly, the holding surfaces 732A and 732B of the holding jigs 73A and 73B tighten the thin cylindrical member 64 so that the cylindrical member 64 is not deformed or damaged.

  The male serration 123 of the torque transmission cylinder 12 is engaged with the female serration jig 75 so that the phases of the missing tooth portion 124 of the male serration 123 of the torque transmission cylinder 12 and the missing tooth section 233 of the male serration 231 of the output shaft 23 coincide with each other. The male serration 231 of the output shaft 23 is engaged with the female serration jig 72.

  As shown in FIG. 6 (1), the assembly of the output shaft 23 and the hollow shaft 11 is set with respect to the holding jigs 73A and 73B so that the axial position is a normal position. Next, the outer periphery 112 of the hollow shaft 11 is held by the holding surfaces 732A and 732B of the holding jigs 73A and 73B, and the stepped surface 115 of the hollow shaft 11 is brought into contact with the upper surfaces 731A and 731B of the holding jigs 73A and 73B.

  In this state, the slide 74 shown in FIG. 3 is lowered, and the torque transmission cylinder 12 is fitted onto the hollow shaft 11, and the inner diameter hole 121 of the torque transmission cylinder 12 is press-fitted into the male serration 111 of the hollow shaft 11. 121 is plastically deformed and engaged with the male serration 111.

  Accordingly, with the electric power steering device 20 alone, the phase of the male serration 123 of the torque transmission cylinder 12 and the male serration 231 of the output shaft 23 can be matched with high accuracy, and the neutral position of the handle and the wheel can be matched with high accuracy. It becomes possible.

  In addition, since it is not necessary to process the male serration 123 of the torque transmission cylinder 12 and the male serration 231 of the output shaft 23 with high accuracy, it is possible to perform rolling with excellent mass production and manufacturing cost. Furthermore, since the inner diameter hole 121 of the torque transmitting cylinder 12 is press-fitted and coupled to the male serration 111 of the hollow shaft 11, there is no risk of backlash or idling occurring at the conventional coupling portion between the tapered shaft and the tapered hole. Further, since the serration phases on the input side and the output side coincide with each other in the electric power steering device alone, the time for assembling to the vehicle body can be shortened compared to the conventional coupling of the taper shaft and the taper hole.

  In the above embodiment, the male serration 111 of the hollow shaft 11 is quenched to increase the hardness, the male serration 111 is press-fitted into the inner diameter hole 121 of the raw material of the torque transmission cylinder 12, and the inner diameter hole 121 is plastically deformed. . As another example, the female serration formed in the torque transmission cylinder 12 is quenched to increase the hardness, the female serration of the torque transmission cylinder 12 is press-fitted into the outer periphery of the raw material of the hollow shaft 11, and the raw material of the hollow shaft 11 is obtained. The outer periphery of each may be plastically deformed.

  FIG. 7A is a longitudinal sectional view of a shaft assembly product showing a state where the assembly of the torque transmission cylinder 12 to the hollow shaft 11 is completed. The shaft assembly in which the output shaft 23, the worm wheel 51, the torsion bar 24, the hollow shaft 11, and the torque transmission cylinder 12 are assembled is assembled to the gear housing 21 in which the detection coil 63 and the bearings 42 and 43 in FIG.

  The shaft assembly is assembled by inserting it into the gear housing 21 from the left side (front side of the vehicle body) in FIG. Next, when the cover 22 with the bearing 41 assembled is assembled to the gear housing 21 from the left side of FIG. 1 (the vehicle body front side), the assembly of the electric power steering device 20 is completed.

  When the electric power steering device 20 is assembled to the vehicle body and a handle (not shown) is operated, the rotation of the handle is transmitted to the torque transmission cylinder 12. The torque of the torque transmission cylinder 12 is transmitted to the output shaft 23 via the inner diameter hole 121 of the torque transmission cylinder 12 and the male serration 111 of the hollow shaft 11, the hollow shaft 11, the pin 25, and the torsion bar 24.

  At this time, the torsion bar 24 that connects the hollow shaft 11 and the output shaft 23 is twisted due to the resistance on the wheel side, and relative rotation occurs between the protrusion on the surface of the sensor shaft portion 62 and the window of the cylindrical member 64. .

  With this relative rotation, the magnetic flux generated in the sensor shaft portion 62 increases or decreases, and the detection coil 63 detects the increase or decrease of the magnetic flux as a change in inductance. From this detection result, torque acting on the torsion bar 24 is detected, and an electric motor (not shown) is driven to rotate the worm 53 with a required steering assist force. The rotation of the worm 53 is transmitted to the wheels via the worm wheel 51, the cored bar 52, and the output shaft 23, thereby reducing the driver's steering torque.

  As shown in FIGS. 7 (1) and (2), in order to prevent an excessive torsional stress from acting on the torsion bar 24 when a large torque is applied to the hollow shaft 11, the hollow shaft 11 and the output shaft A stopper is formed between the two.

  That is, as shown in an enlarged view in FIG. 7 (2), stoppers 113 and 232 are formed in the fitting portion between the outer periphery of the left end of the hollow shaft 11 and the inner periphery of the right end of the output shaft 23. Eight stoppers 113 and 232 are formed at equal angular intervals, and have a clearance β in the rotational direction when torque is not applied to the hollow shaft 11. When a large torque is applied to the hollow shaft 11, the stoppers 113 and 232 come into contact with each other to prevent an excessive torsional stress from acting on the torsion bar 24.

  However, even after the stoppers 113 and 232 come into contact with each other, the torque transmission cylinder 12 and the hollow shaft 11 are slightly twisted. The torsion bar 24 is also slightly twisted by the torque transmission cylinder 12 and the hollow shaft 11 being slightly twisted.

  The twist of the torsion bar 24 after the stoppers 113 and 232 come into contact with each other affects the durability of the torsion bar 24, so it is desirable that the twist is as small as possible. In the embodiment of the present invention, the torque transmission cylinder 12 is formed with a large diameter, and therefore hardly twists.

  Therefore, only the hollow shaft 11 between the engagement portion between the inner diameter hole 121 of the torque transmission cylinder 12 and the male serration 111 of the hollow shaft 11 and the stoppers 113 and 232 is twisted. Therefore, the twist of the torsion bar 24 is small, and the adverse effect on the durability of the torsion bar 24 can be reduced.

  Further, since the torsion bar 24 is less twisted after the stoppers 113 and 232 come into contact with each other, the rigidity of the hollow shaft 11 (than the engagement portion between the inner diameter hole 121 of the torque transmission cylinder 12 and the male serration 111 of the hollow shaft 11). The pin 25 side) may be rigid enough to withstand the small torsion of the torsion bar 24.

  In the embodiment of the present invention, the torsion bar 24 is fitted in the axial through hole 114 formed in the hollow shaft 11 on the input side, and the torsion bar 24 is coupled to the end of the hollow shaft 11 on the handle side by the pin 25. An example in which the present invention is applied to an electric power steering apparatus 20 of the type described above is shown.

  As a modification, a torsion bar 24 is fitted in an axial through hole formed in the hollow shaft 11 on the output side, and the torsion bar 24 is coupled to the end of the hollow shaft 11 on the wheel side with a pin 25. The present invention may be applied to the electric power steering device 20.

  Specifically, a hollow torque transmission cylinder is fitted on the output-side hollow shaft 11 so that the torque transmission cylinder can be transmitted to the hollow shaft 11 on the handle side of the coupling portion between the pin 25 and the hollow shaft 11. Press the serration.

  A serration that transmits the rotation of the torque transmission cylinder to the wheel side is formed at the end of the outer periphery of the torque transmission cylinder on the wheel side. A bearing that rotatably supports the torque transmission cylinder may be disposed between the gear housing 21 and the torque transmission cylinder.

It is a longitudinal cross-sectional view of the gear housing part of the electric power steering apparatus of the Example of this invention. It is a longitudinal cross-sectional view which shows the state before attaching a torque transmission cylinder to a hollow shaft, after attaching a hollow shaft to an output shaft. It is a longitudinal cross-sectional view which shows the process of assembling | attaching a torque transmission cylinder to a hollow shaft. (1) is a longitudinal sectional view showing a coupling state between the male serration of the torque transmission cylinder and the slide side of the press machine, and (2) is an AA sectional view of (1). (1) is a longitudinal sectional view showing a coupling state between the male serration of the output shaft and the bolster side of the press machine, and (2) is a sectional view taken along the line BB of (1). (1) is a longitudinal sectional view of the main part showing a state in which the assembly of the output shaft and the hollow shaft is normally set on the assembly jig of FIG. 3, and (2) is the output shaft and the hollow of the assembly jig of FIG. It is a longitudinal cross-sectional view of the principal part which shows the state which the assembly | attachment product of the axis | shaft set and shifted | deviated to the axial direction. (1) is a longitudinal sectional view showing a state where the assembly of the torque transmission cylinder to the hollow shaft is completed, and (2) is a sectional view taken along the line CC of (1).

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Hollow shaft 111 Male serration 112 Outer periphery 113 Stopper 114 Axial direction through-hole 115 Step surface 12 Torque transmission cylinder 121 Inner diameter hole 122 Inner periphery 123 Male serration 124 No-tooth part 20 Electric power steering device 21 Gear housing 22 Cover 23 Output shaft 231 Male serration 232 Stopper 233 No-tooth part 24 Torsion bar 25 Pin 251 Pin hole 26 Bush 41 Bearing (Deep groove radial ball bearing)
42, 43 Bearing (Deep groove radial ball bearing)
51 Worm wheel 52 Core metal 53 Worm 61 Torque sensor 62 Sensor shaft part 63 Detection coil 64 Cylindrical member 71 Bolster 72 Female serration jig 721 Female serration 73A, 73B Holding jig 731A, 731B Upper surface 732A, 732B Holding surface 733A, 733B Small diameter Inner peripheral surface 74 Slide 75 Female serration jig 751 Female serration

Claims (7)

Gear housing,
An output shaft that is rotatably supported by the gear housing and has a serration that transmits rotation to the wheel side;
A hollow shaft that transmits the rotation on the handle side to the output shaft,
The shaft is fitted into an axial through hole formed in the hollow shaft, and one end in the axial direction is coupled to the end on the handle side of the hollow shaft with a pin, and the other end in the axial direction is engaged with the output shaft so that torque can be transmitted. Combined torsion bar,
A torque sensor for detecting torque acting on the torsion bar;
An electric motor that applies a predetermined steering assist force to the output shaft in accordance with a detection value of the torque sensor;
A hollow torque transmission cylinder that is press-fitted into and engaged with a male serration formed on the outer periphery of the hollow shaft, and has an inner diameter hole that is lower in hardness than the male serration of the hollow shaft,
A serration formed at the handle-side end of the torque transmission cylinder to transmit the rotation of the handle;
A bearing interposed between the gear housing and the torque transmission cylinder and rotatably supporting the torque transmission cylinder;
The hollow shaft and the torque transmission cylinder are press-fitted into the male serration of the hollow shaft while the inner diameter hole of the torque transmission cylinder is plastically deformed so that the serration phases of the output shaft and the torque transmission cylinder coincide with each other. An electric power steering device characterized by being engaged with each other. Gear housing,
An output shaft that is rotatably supported by the gear housing and has a serration that transmits rotation to the wheel side;
A hollow shaft that transmits the rotation on the handle side to the output shaft,
The shaft is fitted into an axial through hole formed in the hollow shaft, and one end in the axial direction is coupled to the end on the handle side of the hollow shaft with a pin, and the other end in the axial direction is engaged with the output shaft so that torque can be transmitted. Combined torsion bar,
A torque sensor for detecting torque acting on the torsion bar;
An electric motor that applies a predetermined steering assist force to the output shaft in accordance with a detection value of the torque sensor;
A hollow torque transmission cylinder that is press-fitted into and engaged with the outer periphery of the hollow shaft and has a female serration having a hardness higher than that of the outer periphery of the hollow shaft;
A serration formed at the handle-side end of the torque transmission cylinder to transmit the rotation of the handle;
A bearing interposed between the gear housing and the torque transmission cylinder and rotatably supporting the torque transmission cylinder;
The hollow shaft and the torque transmission cylinder are press-fitted into the female serration of the torque transmission cylinder while the outer periphery of the hollow shaft is plastically deformed so that the serration phases of the output shaft and the torque transmission cylinder coincide with each other. An electric power steering device characterized by being engaged. In the electric power steering apparatus according to any one of claims 1 and 2,
A stepped surface is formed on the outer periphery of the hollow shaft to support a press-fitting load when a torque transmission cylinder is press-fitted into the hollow shaft. Gear housing,
An input shaft having a serration that is inserted into the gear housing and transmits the rotation of the handle;
A hollow shaft that transmits the rotation of the input shaft to the wheel side,
It is fitted in the axial through hole formed in the hollow shaft, one end in the axial direction is connected to the end of the hollow shaft on the wheel side by a pin, and the other end in the axial direction is engaged with the input shaft so that torque can be transmitted. Combined torsion bar,
A torque sensor for detecting torque acting on the torsion bar;
A hollow torque transmission cylinder that is press-fitted into and engaged with a male serration formed on the outer periphery of the hollow shaft, and has an inner diameter hole that is lower in hardness than the male serration of the hollow shaft,
A serration that is formed at the wheel side end of the torque transmission cylinder and transmits the rotation of the torque transmission cylinder to the wheel side;
An electric motor that applies a predetermined steering assist force to the torque transmission cylinder in accordance with a detection value of the torque sensor;
A bearing interposed between the gear housing and the torque transmission cylinder and rotatably supporting the torque transmission cylinder;
The hollow shaft and the torque transmission cylinder are press-fitted while the serration phase of the input shaft and the serration of the torque transmission cylinder are matched and the inner diameter hole of the torque transmission cylinder is plastically deformed into the male serration of the hollow shaft. An electric power steering device characterized by being engaged with each other. Gear housing,
An input shaft having a serration that is inserted into the gear housing and transmits the rotation of the handle;
A hollow shaft that transmits the rotation of the input shaft to the wheel side,
The shaft is fitted into the axial through hole formed in the hollow shaft, one end in the axial direction is coupled to the end of the hollow shaft on the wheel side by a pin, and the other end in the axial direction is engaged with the input shaft so that torque can be transmitted. Combined torsion bar,
A torque sensor for detecting torque acting on the torsion bar;
A hollow torque transmission cylinder that is press-fitted into and engaged with the outer periphery of the hollow shaft, and has a female serration that is harder than the outer periphery of the hollow shaft;
A serration that is formed at the wheel side end of the torque transmission cylinder and transmits the rotation of the torque transmission cylinder to the wheel side;
An electric motor that applies a predetermined steering assist force to the torque transmission cylinder in accordance with a detection value of the torque sensor;
A bearing interposed between the gear housing and the torque transmission cylinder and rotatably supporting the torque transmission cylinder;
The hollow shaft and the torque transmission cylinder are press-fitted into the female serration of the torque transmission cylinder while the outer periphery of the hollow shaft is plastically deformed so that the serrations of the input shaft and the torque transmission cylinder coincide with each other. An electric power steering device characterized by being engaged. In the electric power steering apparatus according to any one of claims 4 and 5,
A stepped surface is formed on the outer periphery of the hollow shaft to support a press-fitting load when a torque transmission cylinder is press-fitted into the hollow shaft. In the electric power steering apparatus according to any one of claims 1 to 6,
An electric power steering apparatus, wherein the handle is a bar handle.

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