JP2006200595A - Gear and electric power steering device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the steering feeling of a steering wheel connected via a steering shaft by uniformly producing the effects of the elasticity of an elastic member on a worm wheel at any peripheral position. <P>SOLUTION: A disc gear body 13 having a toothed portion 11 formed on the outer periphery has a plurality of bolt holes formed at almost equal intervals in the peripheral direction, which pass therethrough in the axial direction. A cylindrical rubber tube 14 is stored in each of the bolt holes 12. Each of the bolts 18 is inserted through the rubber tube 14, and both first and second flanges 16, 17 are fastened to each other in the state of holding the gear body 13 at both axial sides between the first and second flanges 16, 17. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gear capable of obtaining a uniform elastic effect even when force is applied from any circumferential position of the gear when the gear rotates, and an electric power steering apparatus to which the gear is applied.

  As a conventional electric power steering device, for example, a device described in Patent Document 1 below has been proposed.

  This type of electric power steering apparatus includes a steering shaft connected to a steering wheel, a worm shaft that is coupled to the steering shaft and rotates together with the steering shaft, and an electric motor having a worm shaft that meshes with the worm shaft, The motor controls the rotation angle of the worm wheel engaged with the worm shaft by controlling the rotation amount of the worm shaft.

  The worm wheel is made of a resin-made gear main body having teeth formed on the outer periphery, and a metal disc-shaped connecting member provided so as to sandwich the gear main body on both axial sides of the gear main body. And an annular elastic member interposed between the gear body and the connecting member.

The connecting member is formed with a projecting portion in the circumferential direction toward the axial direction, and the projecting portion and the gear body are arranged on the outer peripheral side of the elastic member so as to alternately contact each other. The member exerts self-elasticity to suppress vibration from being transmitted from the electric motor to the steering wheel.
Japanese translation of PCT publication No. 2004-513021 (FIG. 3)

  However, the worm wheel used in the electric power steering apparatus has a portion where the gear body and the elastic member are in contact with each other and a portion where the protrusion and the elastic member are in contact depending on the circumferential position of the gear body. To do. As a result, the elastic effect of the elastic member differs at the position where the force transmitted from the electric motor to the elastic member via the tooth portion of the gear body switches at these different portions, that is, the circumferential position of the gear, and the steering shaft The steering wheel connected to the worm wheel via the steering wheel has a different feeling.

  The present invention has been made paying attention to such problems, and by making the elastic effect of the elastic member uniform in any circumferential position, the uncomfortable feeling due to the difference in the rotational reaction force of the steering wheel is prevented. The present invention provides a gear capable of improving the steering feeling of the steering wheel and an electric power steering device to which the gear is applied.

  The invention according to claim 1 is a disc-shaped gear body having a plurality of teeth on the outer periphery and having a plurality of through holes penetrating in the axial direction at substantially equal intervals in the circumferential direction, A cylindrical elastic member accommodated in the hole, a coupling member disposed on both sides in the axial direction of the gear main body, and the elastic members are inserted to connect the coupling members while sandwiching the gear main body. And a connecting member.

  According to this invention, the elastic member is accommodated over the entire circumference of the connection member while being accommodated at substantially equal intervals in the gear body, so that the force from the radial direction is applied to the elastic member. It is transmitted to the connecting member through the connecting member inserted, and the uniform elastic effect of the elastic member can be obtained at any circumferential position of the gear. As a result, for example, the force on the shaft coupled to the gear is uniform at any circumferential position of the gear.

  According to a second aspect of the present invention, the gear according to the first aspect is applied as a worm wheel of an electric power steering device, and the worm wheel has a plurality of tooth portions on an outer periphery thereof and has a circumferential direction. A disc-shaped gear body having a plurality of through-holes penetrating in the axial direction at substantially equal positions, cylindrical elastic members accommodated in the respective through-holes, and the gear bodies disposed on both sides in the axial direction. And a connecting member that is inserted through each of the elastic members and connects the connecting members while sandwiching the gear body.

  According to the present invention, as in the first aspect of the present invention, the elastic member is accommodated at substantially equal intervals in the gear body and is fitted over the entire circumference of the connection member. Therefore, even if the worm wheel rotates and a force is applied from any circumferential position of the worm wheel, the uniform elastic effect of the elastic member can be obtained. As a result, the rotational reaction force of the steering shaft coupled to the worm wheel is uniform at any circumferential position, and the steering feeling of the steering wheel connected to the steering shaft can be improved.

  The invention according to claim 3 is characterized in that the gear body is formed of a synthetic resin material, and the elastic coefficient of the elastic member is set larger than the elastic coefficient of the gear body.

  According to the present invention, since the elastic coefficient of the elastic member is set to be larger than the elastic coefficient of the gear body, the elastic member is mainly elastically deformed when a force is applied to the gear from the circumferential direction. Demonstrate the effect. Therefore, the adjustment of the elastic effect can be performed by exchanging only the elastic member, so that the assembling efficiency is improved.

  1 to 3 show an embodiment of a gear according to the present invention and an electric power steering apparatus to which the gear is applied.

  As shown in FIG. 1, the electric power steering apparatus includes a steering shaft 2 connected to a steering wheel 1 and a sensor that is a steering state detection unit that detects the steering state of the steering wheel 1 as the steering shaft 2 rotates. 3, a disc-shaped worm wheel 4 that is a gear coupled to the steering shaft 2, a worm shaft 5 that meshes with the worm wheel 4, and the worm shaft 5. The worm shaft 5 and the worm wheel 4 includes an electric motor 6 for applying a steering assist torque to the steering shaft 2 via 4 and an electric motor control mechanism 7 for controlling the electric motor 6 based on an output signal of the sensor 3. 4 and the electric motor 6 are accommodated in a housing 8, respectively.

  The worm wheel 4 and the worm shaft 5 mesh with each other in an oblique manner, and the worm wheel 4 rotates as the worm shaft 5 rotates.

  One end side of the steering shaft 2 is linked to the steering wheel 1, while the other end side is linked to a pinion shaft (not shown). The steering shaft 2 passes through the worm wheel 4 and the housing 8, is coupled to the worm wheel 4, and is rotatably supported by a pair of annular bearings 9.

  As shown in FIGS. 2 and 3, the worm wheel 4 includes a disc-shaped gear body 13 in which a plurality of through holes bolt holes 12 are formed, and a cylindrical elastic body accommodated in each bolt hole 12. A rubber tube 14 that is a member, first and second flanges 16 and 17 that are connecting members disposed so as to sandwich the gear body 13 on both sides in the axial direction of the gear body 13, and the rubber tubes 14 are inserted. And bolts 18 and 30 that are connecting members for connecting the first and second flanges 16 and 17 to each other.

  The gear body 13 is made of, for example, synthetic resin, and has eight bolt holes 12 penetrating in the axial direction at substantially equal intervals in the circumferential direction, and a tooth portion 11 is formed on the outer periphery. Yes. A gear center hole 15 through which the steering shaft 2 is inserted is formed at the center.

  The first flange 16 is formed in a disc shape, and a central hole 20 through which the steering shaft 2 is inserted is formed at the center. Four bolt insertion holes 21 penetrating in the axial direction are formed at substantially equal intervals in the circumferential direction of the first flange 16, and each of the bolt insertion holes 21 is also at substantially equal intervals in the circumferential direction. Similarly, four nut portions 22 to be fastened to the bolts 18 are formed. That is, the bolt insertion holes 21 and the nut portions 22 are alternately formed at substantially equal intervals.

  On the other hand, the second flange 17 is a cylindrical portion 26 in which a disc portion 24 having substantially the same diameter as the first flange 16 and a central hole 25 through which the steering shaft 2 is inserted are formed in the central portion of the disc portion 24. Are integrated. In addition, four bolt insertion holes 27 penetrating in the axial direction are formed at substantially equal intervals in the circumferential direction of the disk portion 24, and the bolts 30 are also at substantially equal intervals in the circumferential direction. Four nut portions 28 to be fastened are formed.

  A reduced diameter portion 29 is formed at the tip of the cylindrical portion 26, and the outer diameter of the cylindrical portion 26 is slightly smaller than the inner diameter of the gear central hole 15, while the outer diameter of the reduced diameter portion 29 is formed. Is formed in the same size as the inner diameter of the central hole 20 of the first flange 16. As a result, a gap L <b> 1 is formed between the outer peripheral surface of the cylindrical portion 26 and the inner peripheral surface of the gear central hole 15, and the reduced diameter portion 29 is in contact with the peripheral portion of the central hole 20.

  The bolts 18 and 30 have screw portions 19a and 31a formed at the tip portions of the shaft portions 19 and 31, respectively, and an enlarged diameter that is larger than the shaft portions 19 and 30 in the vicinity of the screw heads. Portions 19b and 30b are formed. Since the bolts 18 and 30 are formed in substantially the same shape, only the structure of the bolt 18 will be described below.

  The outer diameter of the enlarged diameter portion 19b is smaller than the inner diameter of the bolt hole 12 of the gear body 13, and is formed to be approximately the same as the inner diameter of the bolt insertion hole 21 of the first flange. As a result, a gap L2 is formed between the outer peripheral surface of the enlarged diameter portion 19b and the inner peripheral surface of the bolt hole 12, and the outer peripheral surface of the enlarged diameter portion 19b is the inner peripheral surface of the bolt insertion hole 21. Abut.

  And since the thread part 19a formed in the front-end | tip part of each said volt | bolt 18 is fastened by each said nut part 28, the said gear main body 13 is hold | maintained by the said 1st, 2nd flanges 16 and 17 at the clamping state. ing.

  Each rubber tube 14 is penetrated so as to be in close contact with the shaft portion 19 of each bolt 18, and rotates together with the bolt 18 when the bolt 18 is fastened to the nut portion 28. . The length of each rubber tube 18 in the axial direction is smaller than the length of the gear body 13 in the axial direction, and the outer diameter of each rubber tube 18 is the outer diameter of the enlarged portion 19b of the bolt 18. And is in contact with the inner peripheral surface of the bolt hole 12.

  The sensor 3 includes a ring-shaped detected member 32 fixed to the outer peripheral side outer surface of the first flange 16 and is inserted and fixed inside from the side portion of the housing 8 so that the detected state of the detected member 32 is That is, it comprises a detector 33 that detects the rotation angle. The sensor 3 continuously transmits an electrical signal of the rotation angle to the machine control mechanism 7 as the detected member 32 rotates.

  The motor control mechanism 7 includes, for example, a microcomputer (not shown), receives and calculates a steering angle from the sensor 3, transmits a control current to the motor 6, and rotates the worm shaft 5 of the motor 6. The amount is to be controlled.

  Hereinafter, the procedure for assembling the worm wheel 4 in the electric power steering apparatus of the present embodiment will be described.

  As shown in FIG. 2, the worm wheel 4 first accommodates the rubber tubes 14 in the bolt holes 12 of the gear main body 13, and then first and second on both axial sides of the gear main body 13. The flanges 16 and 17 are arranged.

  Then, the respective bolts 18 are inserted through the rubber tube 14 from the bolt insertion hole 21 side so that the threaded portions 19a of the bolts 18 protrude from the respective bolt holes 12.

  Using the protruding screw portion 19a as a mark, the screw portion 19a and the nut portion 28 of the second flange 17 are aligned, and after positioning the first and second flanges 16 and 17, the bolts 30 are passed through from the bolt insertion hole 27 side. Then, the respective bolts 30 and the nut portions 22 and 28 are fastened.

  The worm wheel 4 is inserted and coupled to the steering shaft 2 and arranged so that the teeth 11 of the gear body 13 mesh with the worm shaft 5 of the electric motor 6.

  Here, since the bolt 18 is inserted from the bolt insertion hole 21 side and the first and second flanges 16 and 17 are positioned in the circumferential direction, the flanges 16 and 17 are fastened together. In addition to the improvement, the torsional deformation of the rubber tube 14 due to the relative displacement of the first and second flanges 16 and 17 can be prevented.

  In addition, since the second flange 17 can be connected to the first flange 16 by passing the tubular portion 26 of the second flange through the central hole 20 of the first flange 16, a disk with respect to the first flange 16 is provided. The radial relative position of the part 24 can be easily defined, and the assembling efficiency is improved.

  Hereinafter, the operation of the electric power steering apparatus of the present embodiment will be described.

  By steering the steering wheel 1, the steering shaft 2 rotates in the circumferential direction, and the worm wheel 4 coupled to the steering shaft 2 rotates along with the rotation of the steering shaft 2.

  As the worm wheel 4 rotates, the detected member 32 fixed to the outer peripheral side outer surface of the worm wheel 4 also rotates, and the rotation angle of the worm wheel 4 is detected by the detector 33 provided in the housing 8. Then, the detected rotation angle data of the worm wheel 4 is transmitted to the motor control mechanism 7 as an electric signal.

  The electric motor control mechanism 7 controls the electric motor 6 by this electric signal, that is, the rotation amount of the worm shaft 5 of the electric motor 6 is controlled. As a result, the rotation angle of the worm wheel 4 is also controlled. Steering feeling changes.

  When the worm wheel 4 rotates, the worm shaft 4 shown in FIG. 3 receives a radial force from the worm shaft 6, that is, a force from the b direction, and the gear body 13 is urged to the right in the drawing. The

  Here, as described above, between the cylindrical portion 26 of the second flange 17 and the gear central hole 15 of the gear body 13 and between the enlarged diameter portion 19b of the bolt 18 and the bolt hole 12 of the gear body 13. The gaps L1 and L2 are formed over the entire circumference. Thereby, even if the gear body 13 is urged toward the cylindrical portion 26 by the force from the b direction, the inner peripheral surface of the bolt hole 12 is pressed against the outer peripheral surface of the rubber tube 14, and the rubber tube 14 Can surely exert an elastic effect.

  Since the rubber tube 14 is accommodated at substantially equal intervals over the circumferential direction of the gear body 13 and is penetrated so as to closely contact the entire circumference of each bolt 18, the worm wheel Even if 4 receives a force from any circumferential position, a uniform elastic effect can be obtained. As a result, the steering feeling of the steering wheel 1 connected to the worm wheel 4 via the steering shaft 2 can be improved.

  In addition, since each rubber tube 14 is cylindrical, a more uniform elastic effect can be obtained, and the steering feeling of the steering wheel 1 can be further improved.

  Further, since each rubber tube 14 is set to have a larger elastic coefficient than that of the gear body 13, each rubber tube 14 is positively elastically deformed even when the gear body 13 receives a force from the radial direction. To do. Therefore, the elastic characteristics can be adjusted by exchanging each rubber tube 14, and the working efficiency is improved.

  The technical ideas other than the invention described in the claims, as grasped from the embodiment, will be described below.

  The gear according to claim 1, wherein the elastic member is formed in a cylindrical shape.

  According to this invention, since the elastic member is formed in a cylindrical shape, the elastic member exhibits uniform elastic characteristics regardless of the circumferential position, and a more uniform elastic effect can be obtained. it can.

  (2) The connecting member is inserted into a pair of disk-like portions provided on both sides in the axial direction of the gear body, and a central hole provided in the center of the gear body, and the diameter of the pair of disk-like portions. The gear according to claim 1, comprising a cylindrical portion that regulates a relative position in the direction.

  According to this invention, the cylindrical portion is inserted into the central hole, and the radial relative positions of the pair of disk-shaped portions are defined. It becomes easy and work efficiency improves.

  Claim (3) The gear according to claim (2), wherein a gap is set over the entire circumference between the gear body and the cylindrical portion.

  According to this invention, when the gear body receives a force from the circumferential position by setting a gap over the entire circumference between the gear body and the cylindrical portion, the through holes Since the elastic member accommodated in the pressure contact is pressed against the inner peripheral surface of the through hole, the elastic effect by the elastic member can be obtained more reliably.

  (4) The gear according to (2), wherein a gap is set over the entire circumference between the through hole of the gear body and each of the connection members.

  According to this invention, when the gear main body receives a force from the circumferential position by setting a gap over the entire circumference between the through hole of the gear main body and each of the connection members, Similarly to the item (3), since the elastic member inserted through the connection member is pressed against the inner peripheral surface of the through hole, the elastic effect of the elastic member can be obtained more reliably.

  (5) The gear according to (2), wherein each of the connection members is inserted through the through hole of the gear body from alternate directions.

  According to this invention, when connecting the connecting member to the gear body, the connecting member is inserted from one of them, the positioning of the pair of disk-shaped portions in the circumferential direction is performed, and then the connecting member is connected from the opposite direction. Since the insertion connecting members can be fastened, the assembling efficiency is improved.

1 is a simplified cross-sectional view of an electric power steering apparatus according to the present invention. It is a disassembled perspective view of the worm wheel of FIG. It is an expanded sectional view which follows the AA line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Steering wheel 2 ... Steering shaft 3 ... Sensor (steering state detection means)
4. Worm wheel (gear)
5 ... Worm shaft 6 ... Electric motor 7 ... Electric motor control mechanism 11 ... Tooth part 12 ... Bolt hole (through hole)
13 ... gear body 14 ... rubber tube (elastic member)
15 ... Gear central hole 16 ... First flange (connecting member)
17 ... 2nd flange (connection member)
18 ... Bolt (connection member)
24 ... Disc part (disc-like part)
26 ... Cylindrical portions L1, L2 ... Gap

Claims (3)

A disc-shaped gear body having a plurality of teeth on the outer periphery and having a plurality of through-holes penetrating in the axial direction at substantially equal intervals in the circumferential direction;
A cylindrical elastic member accommodated in each through hole;
Connecting members disposed on both axial sides of the gear body;
And a connecting member that is inserted through each of the elastic members and connects the connecting members while sandwiching the gear body. A steering shaft connected to the steering wheel;
Steering state detection means for detecting the steering state of the steering wheel as the steering shaft rotates;
A worm wheel coupled to the steering shaft;
A worm shaft meshing with the worm wheel;
An electric motor having the worm shaft and applying a steering assist torque to the steering shaft via the worm shaft and the worm wheel;
An electric power steering apparatus comprising: an electric motor control mechanism that controls the electric motor based on an output signal of the steering state detection means;
The worm wheel is
A disc-shaped gear body having a plurality of teeth on the outer periphery and having a plurality of through-holes penetrating in the axial direction at substantially equal intervals in the circumferential direction;
A cylindrical elastic member accommodated in each through hole;
Connecting members disposed on both axial sides of the gear body;
An electric power steering apparatus comprising: a connecting member that is inserted through each of the elastic members and connects the connecting members while holding the gear body.   2. The gear according to claim 1, wherein the gear body is formed of a synthetic resin material, and an elastic coefficient of the elastic member is set to be larger than an elastic coefficient of the gear body.

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