JP2005096622A - Electric type power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of a slapping sound by buffering impact force inversely input from a steering wheel. <P>SOLUTION: In this electric type power steering device, a stator 43 is disposed on the inner periphery of a housing 20 of an electric motor 60, a rotor 61 is arranged facedly to the stator 43, and a plurality of bearings for rotatably bearing the rotor 61 are disposed. At least one of the plurality of bearings is used as an angular ball bearing 63 for receiving a force in the thrust direction, and spring members 70 and 80 are disposed for elastically supporting the angular ball bearing 63 with respect to the force working in the thrust direction of the rotor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

   The present invention relates to an electric power steering apparatus of a type that applies assist force to a rack shaft.

   2. Description of the Related Art Conventionally, an electric power steering apparatus that detects torque applied to a handle and applies an assisting force corresponding to the torque to a rack shaft by an electric motor is known as disclosed in Patent Document 1.

   For example, as shown in FIG. 3, an electric power steering apparatus as disclosed in Patent Document 1 includes a stator 3 of an electric motor 2 disposed on the inner periphery of a housing 1, and a magnet facing the stator 3. 4 is attached to the outer periphery, the rotor 5 is formed in a hollow cylindrical shape, and rack teeth 7 and ball grooves 8 that mesh with hollow holes 6 of the rotor 5 that are not shown in the drawings connected to a handle shaft. The nut 11 constituting the ball screw mechanism 10 together with the ball groove 8 is fixed to the hollow hole 6 of the rotor 5, and the rotation of the rotor 5 is performed by the action of the ball screw mechanism 10. By converting the movement to the axial movement of 9, an assist force corresponding to the handle torque is applied to the rack shaft 9, and the steering wheel (not shown) connected to the rack shaft 9 is turned.

Both ends of the rotor 5 are rotatably supported by the housing 1 by a double-row angular bearing 12 and a radial bearing 13, and the axial movement of the rotor 5 with respect to the housing 1 is restricted by the double-row angular bearing 12.
JP-A-7-165089 (page 3, left column, line 38 to right column, line 8; FIG. 4)

   In the above configuration, the rotor 5 connected to the rack shaft 9 via the ball screw mechanism is supported by the housing 1 in a rigid state in the axial direction, so that impact force is applied from the steering wheel connected to the rack shaft 9. In the case of reverse input, the impact force is transmitted to the rotor 5 as it is, and the transmitted impact force is received by the radial bearing without being buffered, which is a cause of sound generation of the electric power steering apparatus. It was.

   It is an object of the present invention to buffer the impact force reversely input from the steering wheel and prevent the occurrence of hitting sound.

  In order to solve the above-mentioned problem, the structural feature of the invention according to claim 1 is that the rotor of the electric motor is formed in a hollow cylindrical shape, and the rack is moved in the axial direction by a ball screw mechanism in the hollow hole of the rotor. An electric power steering system in which a shaft is provided so as to pass therethrough, a housing including a stator that constitutes the motor together with the rotor is provided on the outer periphery of the rotor, and a plurality of bearings that rotatably support the rotor are fitted in the housing. In the apparatus, at least one of the plurality of bearings is a ball bearing that supports a thrust force in the axial direction, and the ball bearing is elastically supported in the axial direction by a spring member on the rotor or the housing. Electric power steering device.

   According to a second aspect of the present invention, in the first aspect, the spring member includes a pair of opposed annular disk portions, and one side of the inner peripheral edge and the outer peripheral edge of the spring member. A gap forming portion that is provided at an edge and forms a predetermined gap between the pair of annular disks, and a flange that protrudes in the axial direction from each outer end face of the pair of annular disks at the other edge It is to provide.

   According to a third aspect of the present invention, in the second aspect of the present invention, the spring member is composed of first and second spring bodies, and the first and second spring bodies are provided with the flanges protruding. Each of the annular disk portions is provided, and the gap forming portion is formed in at least one of the first and second spring bodies.

   The structural feature of the invention according to claim 4 is that, according to claim 2 or 3, the inner ring of the ball bearing is fitted to the rotor so as to be relatively movable in the axial direction, and is arranged on both sides of the bearing. One flange portion of the spring member is brought into contact with both end faces of the inner ring, and the other flange portion is sandwiched between step portions provided on the rotor.

   In the invention according to claim 1 configured as described above, the ball bearing that rotatably supports the rotor on the housing and supports the axial thrust force is elastically supported in the axial direction by the spring member on the rotor or the housing. Therefore, when an impact force is reversely input from the steering wheel to the rack shaft, the rotor connected to the rack shaft via the ball screw mechanism is moved in the axial direction with respect to the housing against the spring force of the spring member. . Thereby, the reversely input impact force is buffered, and the occurrence of a hitting sound is prevented.

   In the invention according to claim 2 configured as described above, when the impact force reversely input to the rack shaft is transmitted to the rotor via the ball screw mechanism, the ball bearing bearing the rotor is elastically supported in the axial direction. The pair of annular disc portions of the spring member bends to buffer the impact force. At this time, the flange portion of the spring member that is in contact with the end face of the ball bearing only moves in the axial direction and does not expand in the radial direction, so that it does not bite into the rotor or the housing to cause malfunction.

   In the invention which concerns on Claim 3 comprised as mentioned above, the spring member is divided | segmented into the 1st and 2nd spring body, and the annular disc by which the collar part protruded from the 1st and 2nd spring body Since the gap is formed in at least one of the first and second spring bodies, the spring member can be easily created.

   In the invention according to claim 4 configured as described above, when the impact force reversely input to the rack shaft is transmitted to the rotor via the ball screw mechanism, the flange portions are arranged on both sides of the ball bearing bearing the rotor. The ring-shaped disk portion of the spring member that contacts both end faces of the inner ring is bent, and the rotor moves in the axial direction relative to the inner ring of the ball bearing to buffer the impact force. Since the rotor is usually made of steel, it has high wear resistance and can move smoothly relative to the inner ring of the ball bearing.

  Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of an electric power steering apparatus according to the present invention. In this power steering apparatus, a vehicle body (not shown) is provided extending in the left-right direction of the vehicle. A rack shaft 40, a ball screw mechanism 50, an electric motor 60, and the like are assembled to an aluminum housing 20 that is attached to the housing.

   Rack teeth 41 are formed on one outer periphery of the rack shaft 40, a pinion (not shown) to which steering force is transmitted from the handle is engaged with the rack teeth 41, and the rack shaft 40 is axially rotated (in FIG. 1) by the rotation of the pinion. Left and right). In addition to the rack teeth 41, the rack shaft 40 is formed with a male screw portion 51 that constitutes the screw shaft of the ball screw mechanism 50. The ball screw mechanism 50 is a rotation-axial motion conversion mechanism that converts the rotation of the rotor 61 of the electric motor 60 described later into movement in the axial direction of the rack shaft 40 and transmits the rotation to the male screw portion 51 of the rack shaft 40. Are screwed through a plurality of balls 53. The nut 52 is fixed with a top 56 for circulating the ball 53 between the adjacent thread grooves of the female thread portion 54 formed on the nut 52.

   The electric motor 60 applies an assist force in the axial direction to the rack shaft 40 via the ball screw mechanism 50, and includes a steel-made rotor 61 and a stator 43. The rotor 61 is formed in a hollow cylindrical shape, and the rack shaft 40 is inserted coaxially through the hollow hole. A plurality of plate-like permanent magnets 42 are bonded to the outer periphery of the rotor 61, and a stator 43 having a plurality of coils facing the permanent magnet 42 is fixed to the inner periphery of the housing 20. Magnetic flux generated by energizing the coils of the stator 43 acts on the permanent magnet 42 to rotate the rotor 61.

   The rotor 61 is supported by the housing 20 so that both ends of the rotor 61 can be rotated by radial ball bearings 62 and double-row angular ball bearings 63 arranged on both sides of the stator 43. The double-row angular ball bearing 63 is a ball bearing that supports the axial thrust force acting on the rotor 61 and restricts the movement of the rotor 61 in the axial direction with respect to the housing 20. An outer ring 63a of a double-row angular ball bearing 63 is fitted into a bearing hole formed on the housing 20 on the rack tooth 41 side (left side in FIG. 1), and one end surface of the outer ring 63a is brought into contact with a shoulder portion of the bearing hole. The other end surface is tightened by a nut 64 screwed into the bearing hole opening.

   The inner ring 63b of the angular ball bearing 63 is fitted to the rotor 61 so as to be slidable in the axial direction, and spring members 70 and 80 are disposed on both sides of the inner ring 63b. The spring member 70 includes first and second spring bodies 71a and 71b, and the first spring body 71a projects in an annular shape to the right from the inner peripheral side edge of the annular disc portion 72a and the annular disc portion 72a. The flange 73a is in contact with the left end surface of the inner ring 63b, and is formed of a gap forming portion 74a projecting leftward from the outer peripheral side edge of the annular disc portion 72a. The second spring body 71b is annularly projected leftward from the inner peripheral side edge portion of the annular disc portion 72b and the annular disc portion 72b facing the annular disc portion 72a, and is screwed to the left end portion of the rotor 61. A flange 73b that comes into contact with the nut 75 and a gap that protrudes rightward from the outer peripheral side edge of the annular disc portion 72b and that abuts against the gap forming portion 74a to form a predetermined gap between the annular disc portions 72a and 72b. It is comprised from the formation part 74b.

   The spring member 80 includes first and second spring bodies 81a and 81b, and the first spring body 81a projects annularly to the left from the inner peripheral side edge of the annular disc portion 82a and the annular disc portion 82a. The flange portion 83a is in contact with the right end surface of the inner ring 63b, and the gap forming portion 84a projects rightward from the outer peripheral side edge portion of the annular disc portion 82a. The second spring body 81b protrudes annularly to the right from the inner peripheral side edge portion of the annular disc portion 82b and the annular disc portion 82b facing the annular disc portion 82a, and comes into contact with the shoulder portion 85 of the rotor 61. The flange portion 83b and the gap forming portion 84b projecting leftward from the outer peripheral side edge of the annular disc portion 82b and contacting the gap forming portion 84a to form a predetermined gap between the annular disc portions 82a and 82b. ing.

   In this way, the inner ring 63b of the angular ball bearing 63 is fitted to the rotor 61 so as to be relatively movable in the axial direction, and one flange 73a, 83a of each spring member 70, 80 disposed on both sides of the bearing 63 is provided. The other flanges 73b and 83b are in contact with both end faces of the inner ring 63b, and are sandwiched between a shoulder 85 and a nut 75, which are stepped portions provided on the rotor 61. The nut 75 is screwed into the left end portion of the rotor 61 to compress the spring members 70 and 80, thereby preloading the angular ball bearing 63.

   The operation of the electric power steering apparatus having the above configuration will be described. When the steering force is transmitted from the unillustrated pinion to the rack teeth 41 of the rack shaft 40, the electric motor 60 is activated with the torque corresponding to the steering force, the rotor 61 is rotated, and the output of the electric motor 60 is the ball screw mechanism. 50 is transmitted as an assist force to the rack shaft 40 through 50, the rack shaft 40 is moved in the axial direction, and the steering wheel is turned.

   When an impact force is reversely input to the rack shaft 40 from the steering wheel, the impact force is transmitted from the rack shaft 40 through the ball screw mechanism 50 to the rotor 61 as an impact force in the axial direction. When the impact force in the axial direction is transmitted to the rotor 61, the spring members 70 and 80 are compressed and deformed according to the direction of the impact force, and the rotor 61 is relatively relative to the inner ring 63b of the angular ball bearing 63 in the axial direction. Move to buffer the impact force. Thus, when the reverse input is generated, the spring members 70 and 80 are deformed to absorb the impact force, so that it is possible to prevent a hitting sound generated between the rack teeth 41 and the pinion. Since the rotor 61 is made of steel, the rotor 61 has high wear resistance and can smoothly move relative to the inner ring 63b of the angular ball bearing 63. Since the impact force does not act on the angular ball bearing 63, the life of the bearing itself can be extended.

   In the above embodiment, the inner ring of the angular ball bearing is fitted to the rotor so as to be slidable in the axial direction, and the spring members are disposed on both end faces of the inner ring, but the outer ring of the angular ball bearing is placed in the bearing hole of the housing. Attached so as to be slidable in the axial direction, the flanges protruding from the outer peripheral edge of the spring member are brought into contact with both end faces of the outer ring, and the flange protruding from the inner peripheral edge is attached to the housing. You may make it pinch | interpose between the provided step parts. In this case, if the housing is made of casting, the wear resistance of the bearing hole with respect to the outer ring can be improved.

   Moreover, in the said embodiment, although the spring member is divided | segmented into the 1st and 2nd spring body, you may shape | mold a spring member integrally.

Sectional drawing of the electric power steering device which concerns on embodiment of this invention. The expanded sectional view of the angular ball bearing part elastically supported by the spring member. Sectional drawing of the conventional electric power steering device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Housing, 40 ... Rack shaft, 41 ... Rack tooth, 42 ... Permanent magnet, 43 ... Stator, 50 ... Ball screw mechanism, 51 ... Male screw part, 52 ... Nut, 53 ... Ball, 54 ... Female screw part, 56 ... Top 60 ... Electric motor, 61 ... Rotor, 62 ... Radial ball bearing, 63 ... Double row angular ball bearing, 63a ... Outer ring, 63b ... Inner ring, 70, 80 ... Spring member, 71a, 81a ... First spring body, 71b, 81b ... second spring body, 72a, 72b, 82a, 82b ... annular disk part, 73a, 73b, 83a, 83b ... collar part, 74a, 74b, 84a, 84b ... gap forming part, 75 ... nut, 85 ... shoulder Department.

Claims (4)

A rotor of an electric motor is formed in a hollow cylindrical shape, a rack shaft that is moved in the axial direction by a ball screw mechanism is passed through the hollow hole of the rotor, and a stator that constitutes the motor together with the rotor is disposed on the outer periphery of the rotor. An electric power steering apparatus in which a plurality of bearings for rotatably supporting the rotor is provided in the housing, and at least one of the plurality of bearings supports an axial thrust force. An electric power steering apparatus comprising a ball bearing and elastically supported in the axial direction by a spring member on the rotor or the housing. 2. The spring member according to claim 1, wherein the spring member is provided at a pair of opposed annular disk parts and one edge of an inner circumferential edge and an outer circumferential edge of the spring member. An electric power steering system, comprising: a gap forming portion that forms a predetermined gap on the outer circumferential surface of the pair of annular discs; and a flange projecting in an axial direction from each outer end surface of the pair of annular disks. apparatus. In Claim 2, the said spring member is comprised by the 1st and 2nd spring body, and this 1st and 2nd spring body each has the said annular disc part by which the said collar part protruded, and said 1st An electric power steering apparatus, wherein the gap forming portion is formed in at least one of the second spring body. 4. The inner ring of the ball bearing according to claim 2 or 3, wherein the inner ring of the ball bearing is fitted to the rotor so as to be relatively movable in the axial direction, and one flange portion of each spring member respectively disposed on both sides of the bearing is an end face of the inner ring. The electric power steering apparatus is characterized in that the other flange portion is held between the step portions provided on the rotor.

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