JP2009250321A - Gear reduction and electric power steering device equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gear reduction and an electric power steering device equipped with the same, capable of suppressing a teeth beating noise, and suppressing the wear of an elastic tooth. <P>SOLUTION: A drive transmission gear train is provided which has at least metallic first gears 19, 24, and a second gear 26 meshing the first gear. The second gear comprises a metallic gear core metal 31, an elastic (resin) tooth 32 fitted externally into the gear core metal, and a hard (metallic) front cover portion 33 fitted externally into the resin tooth, having an operation limiting portion 33a, facing the gear core metal having a predetermined gap in the tooth thickness direction, and meshing the first gear. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gear reduction device capable of suppressing rattling noise and suppressing wear of an elastic tooth portion, and an electric power steering device including the gear reduction device.

  In the electric power steering device, for example, as described in Patent Document 1, an electric motor is arranged in parallel with a rotatable ball nut that is screwed through a ball to a ball screw shaft formed on a rack shaft, A motor parallel type electric power steering system having a gear reduction device in which a drive gear is coupled to a motor shaft of an electric motor, a driven gear is provided with a ball nut, and the drive gear and the driven gear are engaged with each other via an idle gear. There is a device.

The gear reduction device of this type of electric power steering apparatus has a problem that rattling noise is generated due to the meshing of the metal gears because the drive gear, the driven gear, and the idle gear are each made of metal. In order to suppress the rattling noise, for example, as described in Patent Document 2, a so-called hybrid gear (composite gear) in which a metal gear and a resin gear are combined is effective. In the compound gear, the tooth thickness of the tooth portion of the resin gear is formed to be slightly larger than the tooth thickness of the tooth portion of the metal gear, and in normal times when the transmission torque is small, the resin gear is used as the drive gear and the driven gear. By engaging the gears, the metal gears are prevented from meshing with each other and the rattling noise is suppressed.
JP-A-2005-280555 Japanese Utility Model Publication No. 1-116250

  However, when the compound gear described in Patent Document 2 is applied to, for example, a gear reduction device of a motor parallel type electric power steering device as described in Patent Document 1, a resin gear meshing with a metal gear is used. Accordingly, there is a problem that it gradually wears down and it is difficult to stably suppress the rattling noise over a long period of time.

  The present invention has been made in order to solve the above-described conventional problems, and can reduce gear rattling noise and can reduce wear of elastic teeth, and an electric power steering device including the gear reduction device. Is intended to provide.

  In order to solve the above-described problem, the invention according to claim 1 is characterized in that a drive transmission gear train having at least a first metal gear and a second gear meshing with the first gear is provided, The gear has a metal gear core, an elastic tooth portion fitted on the gear core, and a predetermined clearance in the circumferential direction with respect to the gear tooth metal. The gear reduction device is configured by a hard cover portion that has an operation limiting portion facing each other and meshes with the first gear.

  According to a second aspect of the invention, there is provided a gear reduction device according to the first aspect, wherein the elastic tooth portion is made of resin and the hard cover portion is made of metal.

  A feature of the invention according to claim 3 is the gear reduction device according to claim 1 or 2, wherein the first gear and the second gear are helical gears.

  According to a fourth aspect of the present invention, there is provided an electric power steering apparatus including the gear reduction device according to any one of the first to third aspects.

  According to a fifth aspect of the present invention, in the fourth aspect, the first gear of the gear reduction device is provided on a metal drive gear driven by an electric motor and a ball nut screwed to the ball screw shaft. This is an electric power steering device comprising a metal driven gear and the second gear meshed with the drive gear and the driven gear.

  According to the invention of the gear reduction device according to claim 1, the second gear meshing with the metal first gear includes the metal gear core, the elastic tooth portion fitted on the gear core, and the elasticity. Since it is comprised by the hard surface mounting part which has the operation | movement limitation part which is externally fitted by the tooth | gear part and has a predetermined clearance in the circumferential direction with respect to the gear wheel core, the first gear and the second gear While it is possible to suppress rattling noise due to meshing, the elastic tooth portion does not mesh directly with the metal gear, so that wear of the elastic tooth portion can be suppressed. Moreover, since the elastic deformation of the elastic tooth portion can be restricted by the operation restricting portion, highly rigid transmission can be achieved and the durability of the elastic tooth portion can be improved.

  According to the invention of the gear reduction device according to claim 2, since the elastic tooth portion is made of resin and the hard cover portion is made of metal, the wear of the resinous tooth portion can be suppressed, and the operation limiting portion. The life of the resinous tooth portion can be improved by restricting the elastic deformation due to.

  According to the invention of the gear reduction device according to claim 3, since the first gear and the second gear are helical gears, the meshing rate between the first gear and the second gear can be increased. In combination with the elastic tooth portion (resin tooth portion), it is possible to effectively reduce noise due to meshing.

  According to the invention of the electric power steering device according to the fourth aspect, since the gear reduction device having the above-described configuration is provided, an electric power steering device with low noise and a long life can be realized.

  According to the invention of the electric power steering device according to claim 5, the first gear of the gear reduction device is provided on the metal drive gear driven by the electric motor and the ball nut screwed to the ball screw shaft. Since the second gear is engaged with the drive gear and the driven gear, the motor parallel type electric power steering apparatus in which the electric motor is arranged in parallel with the ball screw shaft formed on the rack shaft is made of a metal driven gear. Can be easily applied.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an external view of an electric power steering apparatus 10 provided with a gear reduction device of the present invention, and FIG. 2 shows a cross-sectional view of a main part of the electric power steering apparatus 10.

  1 and 2, the electric power steering apparatus 10 includes a gear housing 11, and the gear housing 11 includes first and second housings 11a and 11b integrally coupled to each other, and an end fixed to the second housing 11b. It consists of a cover 11c. A pinion shaft 13 as an input shaft rotated by a steering wheel (not shown) is rotatably supported by the first housing 11a. In addition, the rack shaft 14 as a steered shaft that meshes with the pinion shaft 13 and extends in the width direction orthogonal to the traveling direction of the automobile is axially movable in the first and second housings 11a and 11b and the end cover 11c. A ball screw shaft 15 is integrally formed on the rack shaft 14. Both ends of the rack shaft 14 are connected to the steered wheels via tie rods and knuckle arms (not shown).

  As shown in detail in FIG. 2, a ball nut 16 is supported on the second housing 11 b via a bearing 17 so as to be rotatable concentrically with the rack shaft 14. Screw grooves 15 a and 16 a are formed on the outer periphery of the ball screw shaft 15 and the inner periphery of the ball nut 16, and these screw grooves 15 a and 16 a are screwed through a ball 18. A metal driven gear 19 is integrally attached to the outer periphery of the ball nut 16. The ball screw shaft 15 and the screw grooves 15a and 16a of the ball nut 16 and the ball 18 constitute a ball screw mechanism 20, and the ball screw mechanism 20 causes the ball nut shaft 16 to rotate the ball screw shaft 15 (rack). It is converted into an axial movement of the shaft 14).

  In addition, an electric motor 21 disposed in parallel with the rack shaft 14 is installed on the end cover 11c. The motor shaft of the electric motor 21 is connected to a drive shaft 23 supported by the second housing 11b via a bearing 22 so as to be rotatable about an axis parallel to the rack shaft 14. A metal drive gear 24 is integrally provided at one end of the drive shaft 23. An intermediate shaft 25 is fixedly disposed in the second housing 11 b between the rack shaft 14 and the drive shaft 23 in parallel with the rack shaft 14 and the drive shaft 23. On the intermediate shaft 25, an idle gear 26 that meshes with the drive gear 24 and the driven gear 19 and transmits the rotation of the drive gear 24 to the driven gear 19 rotates about an axis parallel to the rack shaft 14 via a bearing 27. Supported as possible.

  The drive gear 24, the idle gear 26, and the driven gear 19 described above are helical gears, and the meshing rate of the drive gear 24, the idle gear 26, and the driven gear 19 is increased by the helical gear. The drive gear 24, the idle gear 26, and the driven gear 19 constitute a gear reduction mechanism 30 that reduces and transmits the rotation of the electric motor 21 to the ball nut 16.

  As shown in FIG. 3, the idle gear 26 includes a metal gear core 31 having a gear shape, and resin tooth portions 32 that are externally fitted to both side surfaces of the tooth portions 31 a of the gear core 31. The metal cover portion 33 is externally fitted to the resin tooth portion 32, and the metal cover portion 33 is engaged (contacted) with the drive gear 24 and the driven gear 19 described above.

  The metal gear mandrel 31 is substantially similar to a conventional metal idle gear, and is formed in a tooth shape that is slightly smaller than the tooth shape of the idle gear. A substantially V-shaped resin tooth portion 32 is attached to the gear core 31 across the opposing side surfaces of the adjacent tooth portions 31 a, and the resin tooth portion 32 is between the tooth portions 31 a of the gear core 31. Are provided over the circumference. On each resin tooth part 32, a substantially V-shaped metal cover part 33 is attached so as to cover the resin tooth part 32. The resin tooth portion 32 and the metal cover portion 33 have an axial length substantially the same as the axial length of the gear core 31.

  More specifically, a gear core 31 and a plurality of metal cover parts 33 bent in a substantially V shape with a space on the circumference of the gear core 31 are set in a not-illustrated mold. By injecting the resin into the mold, the gear core 31 and the plurality of metal surface mounting portions 33 are integrally formed through the resin tooth portion 32. Alternatively, the resin tooth portion 32 is vulcanized and bonded to the metal cover portion 33 bent into a substantially V shape, and then the resin tooth portion 32 is integrally attached to the gear core 31 to be integrally formed. .

  At both ends of the metal cover portion 33, there are provided operation limiting portions 33a facing each other with a small amount of gap S on the side surface of the tip portion of the tooth portion 31a of the gear core 31. These operation limiting portions 33a are made of resin. When the tooth forming portion 32 is compressed by a predetermined amount, it contacts the side surface of the tip portion of the tooth portion 31a of the gear core 31 so that the resin tooth portion 32 is not further compressed.

  The drive gear 24 and / or the driven gear 19 described above constitute the first gear in the claims, and the idle gear 26 constitutes the second gear in the claims.

  Next, the operation of the electric power steering apparatus 10 including the gear reduction mechanism 30 configured as described above will be described. When a steering wheel (not shown) is steered, steering torque is input to the pinion shaft 13, and the rack shaft 14 is moved in the axial direction via a rack and pinion mechanism including the pinion shaft 13 and the rack shaft 14.

  The steering torque input to the pinion shaft 13 is detected by a torque sensor (not shown), and the electric motor 21 is rotationally controlled based on the detected steering torque to generate auxiliary torque. The auxiliary torque by the electric motor 21 is transmitted to the ball nut 16 via the drive gear 24, the idle gear 26 and the driven gear 19, and the rack shaft 14 is moved in the axial direction by the rotation of the ball nut 16, and the steering wheel by the driver. The steering force is reduced.

  At this time, since the metal surface mounting portion 33 is engaged with the drive gear 24 and the driven gear 19 via the resin tooth portion 32 of the idle gear 26, the transmission torque acting on the gear reduction mechanism 30 is less than a predetermined value. The resin tooth portion 32 of the idle gear 26 is elastically deformed, and the rattling noise generated when the metal gears are engaged with each other can be suppressed. Moreover, since the resin tooth portion 32 does not directly mesh with the drive gear 24 and the driven gear 19, the wear of the resin tooth portion 32 can be suppressed even after long-term use, and the durability of the gear reduction mechanism 30 can be reduced. Can be improved.

  Further, when the transmission torque acting on the gear reduction mechanism 30 becomes a predetermined value or more, due to the elastic deformation of the resin tooth portion 32, the operation limiting portion 33a of the metal surface mounting portion 33 comes into contact with the gear core 31 and the resin tooth portion. 32 is prevented from further elastic deformation, and the gear core 31, the resin tooth portion 32, and the metal surface mounting portion 33 function like a rigid gear, so that the driving force of the driving gear 24 is highly rigid to the driven gear 19. It is possible to suppress the settling of the resin teeth 32.

  As described above, according to the gear reduction mechanism 30 in the present embodiment, the idle gear 26 is made of the metal gear core 31, the resin tooth portion 32 fitted on the gear core 31, and the resin gear. Since the metal cover part 33 that is externally fitted to the tooth part 32 is provided with the operation restricting part 33a that restricts the elastic deformation of the resin tooth part 32, the idle gear 26 and the drive are driven. Since the rattling noise caused by the meshing with the gear 24 and the driven gear 19 can be suppressed and the resin tooth portion 32 does not directly contact the metal drive gear 24 and the driven gear 19, the resin tooth Wear of the portion 32 can be suppressed. Moreover, since the elastic deformation of the resin-made tooth portion 32 can be restricted by the operation restricting portion 33a, high-rigidity transmission can be achieved and the durability of the resin-made tooth portion 32 can be improved.

  Further, since the drive gear 24, the idle gear 26, and the driven gear 19 are helical gears, the meshing rate among the drive gear 24, the idle gear 26, and the driven gear 19 can be increased. In combination with the resin tooth portion 32, noise due to meshing can be effectively reduced.

  Furthermore, by applying the gear reduction mechanism 30 described above to the electric power steering apparatus 10, it is possible to realize the electric power steering apparatus 10 with low noise and long life.

  FIG. 4 shows a second embodiment of the present invention. The difference from the first embodiment is that, in the first embodiment, the resin tooth portion 32 and the metal cover portion 33 are provided. In the second embodiment, the axial lengths of the resin tooth portion 32 and the metal surface mounting portion 33 are set to the axis of the gear core 31. That is, the resin tooth portion 32 and the metal surface mounting portion 33 are provided in part of the axial direction of the gear core 31 by making the length smaller than the direction length. In this case, as shown in FIG. 4, the resin tooth portion 32 and the metal surface mounting portion 33 are provided in one row at the central portion in the axial direction of the gear core 31, and there are two spaces in the axial direction of the gear core 31. More than one row may be provided.

  In the above-described embodiment, an example in which the gear reduction mechanism 30 includes the drive gear 24, the idle gear 26, and the driven gear 19 has been described. However, the gear reduction mechanism 30 includes at least a first metal gear (for example, The present invention can be applied to a gear having a driving gear 24 or a driven gear 19) and a second gear made up of a gear core 31, a resin tooth portion 32, and a metal cover portion 33. In this case, the resin tooth portion 32 and the metal cover portion 33 that are externally fitted to the gear mandrel 31 are not limited to the configurations described in the embodiment. For example, the resin tooth portion 32 is made of resin. Other than the above, an elastically deformable elastic tooth portion may be used, and the metal cover portion 33 may be a hard cover portion made of a hard material other than metal.

  Further, in the above-described embodiment, the drive gear 24, the idle gear 26 and the driven gear 19 are constituted by helical gears. However, even if these gears 24, 26 and 19 are constituted by spur gears, the same effect is obtained. An effect can be expected.

  In the above-described embodiment, the example in which the gear reduction mechanism 30 is applied to the electric power steering apparatus 10 has been described. However, in the present invention, the rattling noise generated when the metal gears mesh with each other becomes a problem. The present invention can be similarly applied to other gear reduction mechanisms.

  As described above, the present invention is not limited to the above-described embodiments, and various forms can be adopted without departing from the gist of the present invention described in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS It is an external view of the electric power steering apparatus provided with the gear reduction device which shows the 1st Embodiment of this invention. It is a principal part expanded sectional view of FIG. It is sectional drawing which shows the idle gear provided with the resin-made tooth part externally fitted by the gear wheel core, and the metal surface part. It is a figure which shows the idle gear which shows the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electric power steering apparatus, 11 ... Gear housing, 13 ... Pinion shaft, 14 ... Rack shaft, 15 ... Ball screw shaft, 16 ... Ball nut, 19, 24 ... First gear (driven gear, drive gear), 21 ... Electric motor, 26 ... second gear (idle gear), 30 ... gear reduction mechanism, 31 ... gear core, 32 ... elastic (resin) tooth part, 33 ... hard (metal) cover part, 33a ... operation limiting part .

Claims (5)

A drive transmission gear train having at least a first gear made of metal and a second gear meshing with the first gear;
The second gear includes a metal gear mandrel, an elastic tooth portion fitted on the gear mandrel, and a predetermined gap in a circumferential direction with respect to the gear mandrel. A hard cover part that has an operation limiting part facing and meshes with the first gear;
It is comprised by these. The gear reduction device characterized by the above-mentioned.   2. The gear reduction device according to claim 1, wherein the elastic tooth portion is made of resin, and the hard cover portion is made of metal.   3. The gear reduction device according to claim 1, wherein the first gear and the second gear are helical gears.   An electric power steering apparatus comprising the gear reduction device according to any one of claims 1 to 3. 5. The first gear of the gear reduction device according to claim 4, comprising a metal drive gear driven by an electric motor and a metal driven gear provided on a ball nut screwed to a ball screw shaft. An electric power steering device in which the second gear is meshed with a drive gear and a driven gear.

Images