WO2018193919A1 - Rack shaft and method for manufacturing rack shaft - Google Patents

Rack shaft and method for manufacturing rack shaft Download PDF

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Publication number
WO2018193919A1
WO2018193919A1 PCT/JP2018/015117 JP2018015117W WO2018193919A1 WO 2018193919 A1 WO2018193919 A1 WO 2018193919A1 JP 2018015117 W JP2018015117 W JP 2018015117W WO 2018193919 A1 WO2018193919 A1 WO 2018193919A1
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WO
WIPO (PCT)
Prior art keywords
shaft
rack
rack teeth
crushing
teeth
Prior art date
Application number
PCT/JP2018/015117
Other languages
French (fr)
Japanese (ja)
Inventor
真楽 吉川
井出　典数
Original Assignee
Ｋｙｂ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ｋｙｂ株式会社 filed Critical Ｋｙｂ株式会社
Publication of WO2018193919A1 publication Critical patent/WO2018193919A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
    • B21J5/06—Methods for forging, hammering, or pressing; Special equipment or accessories therefor for performing particular operations
    • B21J5/12—Forming profiles on internal or external surfaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
    • B21J5/06—Methods for forging, hammering, or pressing; Special equipment or accessories therefor for performing particular operations
    • B21J5/08—Upsetting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
    • B21K1/00—Making machine elements
    • B21K1/76—Making machine elements elements not mentioned in one of the preceding groups
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23F—MAKING GEARS OR TOOTHED RACKS
    • B23F1/00—Making gear teeth by tools of which the profile matches the profile of the required surface
    • B23F1/08—Making gear teeth by tools of which the profile matches the profile of the required surface by broaching; by broach-milling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23F—MAKING GEARS OR TOOTHED RACKS
    • B23F5/00—Making straight gear teeth involving moving a tool relatively to a workpiece with a rolling-off or an enveloping motion with respect to the gear teeth to be made
    • B23F5/20—Making straight gear teeth involving moving a tool relatively to a workpiece with a rolling-off or an enveloping motion with respect to the gear teeth to be made by milling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23F—MAKING GEARS OR TOOTHED RACKS
    • B23F5/00—Making straight gear teeth involving moving a tool relatively to a workpiece with a rolling-off or an enveloping motion with respect to the gear teeth to be made
    • B23F5/28—Making straight gear teeth involving moving a tool relatively to a workpiece with a rolling-off or an enveloping motion with respect to the gear teeth to be made by broaching; by broach-milling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D3/00—Steering gears
    • B62D3/02—Steering gears mechanical
    • B62D3/12—Steering gears mechanical of rack-and-pinion type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
    • F16H55/02—Toothed members; Worms
    • F16H55/26—Racks

Definitions

  • the present invention relates to a rack shaft and a method for manufacturing the rack shaft.
  • a dual pinion type electric power steering device in which steering torque by a driver and steering assist torque by an electric motor are independently input to a rack shaft is known.
  • a dual pinion type electric power steering apparatus it has been proposed to reduce the weight by forming a rack shaft from a hollow or cylindrical member (JP 2004-523365A, JP 2014-124767A).
  • first rack teeth are formed on a hollow first bar by forging.
  • a hollow second shaft is joined to the first shaft by friction welding, and second rack teeth are formed on the second shaft by cutting.
  • both the first and second rack teeth are formed by forging.
  • the shaft In the forging process, the shaft is plastically deformed according to the pressure applied to the shaft. Therefore, in order to form rack teeth, it is necessary to apply a large pressure to the shaft, and when the pressure is applied to the shaft, the shaft may rotate around the axis with respect to the mold. If the shaft rotates about the axis with respect to the mold at the time of forming the second rack tooth, the phase angle of the second rack tooth with respect to the first rack tooth shifts, and the phase angle accuracy of the first rack tooth and the second rack tooth decreases. To do.
  • the second rack teeth are formed by cutting a second shaft whose outer surface and inner surface are circular. Therefore, the thickness between the bottom of the second rack teeth and the inner surface of the second shaft decreases from the end in the tooth width direction of the second rack teeth toward the center, and the strength at the center is the lowest. If the second shaft is made thicker in order to increase the strength at the central portion, the portion other than the central portion becomes thicker than necessary, and the weight of the rack shaft increases.
  • An object of the present invention is to reduce the weight of the rack shaft while improving the phase angle accuracy of the first rack teeth and the second rack teeth.
  • the present invention relates to a rack shaft that converts the rotational motion of the first and second pinion gears into a linear motion.
  • the rack shaft includes a hollow shaft body, and first and second rack teeth provided on the shaft body and meshing with the first and second pinion gears, respectively.
  • the crushed portion is formed by crushing in the radial direction and includes a flat portion on the outer surface, and at least one of the first and second rack teeth is formed in the crushed portion by cutting.
  • a method for manufacturing a rack shaft includes a first rack tooth forming step for forming a first rack tooth on a hollow shaft body, and a second rack tooth for forming a second rack tooth on the shaft body. And forming a crushing portion including a flat portion on the outer surface by crushing the shaft main body in the radial direction, and crushing after forming the first rack teeth. Forming a second rack tooth on the part by cutting.
  • FIG. 1 is a configuration diagram of an electric power steering apparatus including a rack shaft according to the first embodiment of the present invention.
  • FIG. 2 is a cross-sectional view of the rack shaft according to the first embodiment of the present invention.
  • 3A is a cross-sectional view taken along line IIIA-IIIA shown in FIG. 3B is a cross-sectional view taken along line IIIB-IIIB shown in FIG. 4A.
  • 3C is a cross-sectional view taken along the line IIIC-IIIC shown in FIG.
  • FIG. 4A is a view for explaining a method of manufacturing the rack shaft shown in FIG. 2, and shows a step of forming a first crushing portion in the shaft body.
  • FIG. 4B is a view for explaining a method of manufacturing the rack shaft shown in FIG.
  • FIG. 5 is a cross-sectional view of a rack shaft according to the second embodiment of the present invention, corresponding to FIG.
  • FIG. 6A is a diagram for explaining a method of manufacturing the rack shaft shown in FIG. 5 and shows a step of forming first rack teeth on the shaft body.
  • FIG. 6B is a view for explaining a method of manufacturing the rack shaft shown in FIG. 5 and shows a step of forming a crushing portion in the shaft body.
  • FIG. 7 is a cross-sectional view of a rack shaft according to the third embodiment of the present invention, corresponding to FIG.
  • FIG. 8A is a cross-sectional view showing a modified example of the crushed portion, and corresponds to FIG. 3C.
  • FIG. 8B is a cross-sectional view showing another modified example of the crushed portion, corresponding to FIG. 3C.
  • FIG. 9 is a cross-sectional view of a rack shaft according to a comparative example, corresponding to FIG. 3C.
  • FIG. 1 is a configuration diagram of an electric power steering apparatus 100 including a rack shaft 50 according to the first embodiment of the present invention.
  • the electric power steering device 100 is a dual pinion type electric power steering device in which the steering force by the driver and the assist driving force by the electric motor 21 are independently input to the rack shaft 50.
  • the electric power steering apparatus 100 includes a steering mechanism 10 that steers the wheels 2 of the vehicle according to the rotation of the steering wheel 1 to which the steering force is input by the driver, and an assist mechanism 20 that assists the driver's steering force. And a control device 30 for controlling the assist amount of the steering force.
  • the steering mechanism 10 includes a steering shaft 11 that is connected to the steering wheel 1 and rotates according to the rotation of the steering wheel 1, and a rack shaft 50 that steers the vehicle wheel 2 according to the rotation of the steering shaft 11. .
  • the rack shaft 50 is connected to the wheel 2 via the tie rod 3.
  • the steering shaft 11 has an input shaft 13 connected to the steering wheel 1 and an output shaft 15 connected to the input shaft 13 via a torsion bar 14.
  • the output shaft 15 is provided with a first pinion gear 16 that meshes with the rack shaft 50.
  • the assist mechanism 20 includes an electric motor 21 that is a power source of assist force, a worm shaft 22 that is coupled to the output shaft of the electric motor 21, a worm wheel 23 that meshes with the worm shaft 22, and a pinion that is coupled to the worm wheel 23. And a shaft 24.
  • the pinion shaft 24 is provided with a second pinion gear 25 that meshes with the rack shaft 50.
  • the control device 30 includes a torque sensor 31 that detects the steering torque applied to the torsion bar 14 based on the relative rotation between the input shaft 13 and the output shaft 15, and a rotation angle sensor 32 that detects the rotation angle of the pinion shaft 24.
  • the steering angle sensor 34 that detects the rotation angle (steering angle) of the steering wheel 1, the motor rotation angle sensor 35 that is configured by a resolver and detects the rotation angle of the electric motor 21, and the controller 33 that controls the operation of the electric motor 21. And having.
  • the controller 33 controls the driving of the electric motor 21 based on the steering torque detected by the torque sensor 31 and the rotation angle of the electric motor 21 detected by the motor rotation angle sensor 35.
  • the controller 33 may control the driving of the electric motor 21 in consideration of the steering angle detected by the steering angle sensor 34 in addition to the steering torque and the rotation angle of the electric motor 21. Further, the controller 33 may control the driving of the electric motor 21 in consideration of the rotation angle of the pinion shaft 24 detected by the rotation angle sensor 32.
  • the rotation angle of the pinion shaft 24 detected by the rotation angle sensor 32 is used, the turning angle of the wheel 2 can be accurately grasped.
  • the detection result of the rotation angle sensor 32 is also used in control of a VDC (Vehicle Dynamics Control) or the like that suppresses a side slip or the like of the vehicle.
  • VDC Vehicle Dynamics Control
  • the rack shaft 50 includes a shaft main body 51 and first and second rack teeth 52 and 53 provided on the outer periphery of the shaft main body 51.
  • the first rack teeth 52 mesh with the first pinion gear 16 of the output shaft 15, and the second rack teeth 53 mesh with the second pinion gear 25 of the pinion shaft 24.
  • the shaft body 51 is connected to the wheel 2 via the tie rod 3.
  • Rotational force of the steering wheel 1 is transmitted to the output shaft 15 via the input shaft 13 and the torsion bar 14.
  • the rotational force of the output shaft 15 is converted into a force in the axial direction of the rack shaft 50 (the left-right direction of the vehicle) via the first pinion gear 16 and transmitted to the rack shaft 50. For this reason, when the steering wheel 1 is steered, the rack shaft 50 moves in the axial direction, and the vehicle wheel 2 is snaked according to the movement of the rack shaft 50.
  • Rotational force of the electric motor 21 is transmitted to the pinion shaft 24 via the worm shaft 22 and the worm wheel 23.
  • the rotational force of the pinion shaft 24 is converted into a force in the axial direction of the rack shaft 50 (the left-right direction of the vehicle) and transmitted to the rack shaft 50. For this reason, when the electric motor 21 is rotationally driven, a steering assist thrust is applied to the rack shaft 50 and the steering of the steering wheel 1 is assisted.
  • the rack shaft 50 is formed from a metal material (for example, carbon steel). As shown in FIG. 2, the shaft body 51 of the rack shaft 50 is formed in a hollow shape.
  • the shaft body 51 may be formed as a single hollow member that does not include a joint portion, or may be formed by joining a plurality of hollow members. When the rack shaft 50 is formed as one hollow member that does not include a joint portion, it is easy to ensure the coaxiality of the rack shaft 50.
  • a seamless tube or an electric resistance tube can be used as the hollow member that does not include the joint portion. Since the seamless pipe and the electric resistance welded pipe do not include the joint portion, the joining work can be omitted. Furthermore, you may perform processes, such as a swaging process and a drawing process, to a seamless pipe or an electric sewing pipe.
  • the shaft body 51 includes first and second crushing parts 54 and 55 having flat parts 54a and 55a on the outer surface, and an intermediate part 56 provided between the first and second crushing parts 54 and 55. As shown in FIG. 3A, the outer surface and the inner surface of the intermediate portion 56 are formed in a circular shape. As shown in FIG. 2, the 1st and 2nd rack teeth 52 and 53 are formed in the 1st and 2nd crushing parts 54 and 55, respectively.
  • the first crushing portion 54 is formed by crushing a part of the material of the shaft main body 51 whose entire length is formed in a cylindrical shape in the radial direction. Specifically, first, the outer surface of the material of the shaft body 51 is sandwiched between the upper mold 61 and the lower mold 62 of the processing machine 60. Next, the pressing die 63 is inserted into the guide hole 61 a of the upper die 61 to crush a part of the material of the shaft body 51 in the radial direction. Thereby, the first crushing portion 54 is formed in the shaft main body 51. Since a part of the shaft body 51 is crushed to form the first crushed portion 54, a flat portion 54a is formed on the outer surface of the first crushed portion 54 as shown in FIG. 3B.
  • the mandrel 64 When forming the first crushing portion 54, the mandrel 64 is inserted into the shaft body 51 as shown in FIG. 4A. A flat portion 64 a is formed on the outer surface of the mandrel 64, and the pressing die 63 crushes the shaft body 51 toward the flat portion 64 a of the mandrel 64. Therefore, as shown in FIG. 3B, a flat portion 54 b is formed on the inner surface of the first squashed portion 54. Since the flat portions 54a and 54b are formed on the outer and inner surfaces of the first squashed portion 54, the first squashed portion 54 has a uniform thickness.
  • the second crushing portion 55 is formed by crushing a part of the material of the shaft body 51 formed in a cylindrical shape in the radial direction, like the first crushing portion 54. Therefore, flat portions 55a and 55b are formed on the outer surface and the inner surface of the second crushed portion 55 similarly to the first crushed portion 54, and the second crushed portion 55 has a uniform thickness.
  • the first rack teeth 52 are formed in the first crushing portion 54 by cutting. Specifically, a part of the 1st crushing part 54 is cut using the broaching board 70, and a some groove
  • the width of the flat portion 54 a of the first crushing portion 54 corresponds to the tooth width L ⁇ b> 1 of the first rack tooth 52.
  • the depth of the groove formed in the first crushing portion 54 by the cutting process corresponds to the tooth height L ⁇ b> 2 of the first rack tooth 52.
  • the bottom surface of the groove formed in the first crushing portion 54 by cutting is a tooth bottom 52 a of the first rack tooth 52.
  • the tooth tips of the first rack teeth 52 may be further cut.
  • the width of the flat portion 54 a after cutting corresponds to the tooth width L 1 of the first rack tooth 52.
  • the cutting resistance can be reduced by controlling the cutting allowance, the force applied to the shaft main body 51 compared to the case where the first rack teeth 52 are formed by plastic deformation. Can be reduced. Therefore, the shaft body 51 can be prevented from moving with respect to the broaching machine 70 during the cutting process, and the first rack teeth 52 can be formed at a desired phase angle.
  • a flat portion 54 b is formed on the inner surface of the first squashed portion 54. Therefore, the thickness between the bottom 52a of the first rack tooth 52 and the inner surface of the first crushed part 54 is formed by cutting the first crushed part 54 along the flat part 54b to form the first rack tooth 52.
  • L3 is substantially uniform in the tooth width direction of the first rack teeth 52.
  • FIG. 9 is a cross-sectional view of the rack shaft 450, corresponding to FIG. 3C.
  • the first rack teeth 452 are formed by cutting a material of the shaft body 451 whose outer surface and inner surface are circular. Specifically, first, a cutting portion 454 having a flat portion 454a on the outer surface is formed on the material of the shaft body 451 by cutting. Thereafter, a plurality of grooves are formed in the cutting portion 454 by cutting. Thereby, the first rack teeth 452 are formed. Therefore, the width of the flat portion 454a of the cutting portion 454 corresponds to the tooth width L21 of the first rack tooth 452. Further, the depth of the groove formed in the cutting part 454 corresponds to the tooth height L22 of the first rack tooth 452.
  • the thickness between the bottom 452a of the first rack tooth 452 and the inner surface of the shaft main body 451 is the tooth width direction of the first rack tooth 452. It decreases as it goes from both ends to the central portion 452b. That is, the thickness L23 at the central portion 452b is the smallest.
  • the strength of the first rack teeth 452 depends on the thickness between the tooth bottom 452a and the inner surface of the shaft body 451. In order to give the first rack teeth 452 a desired strength, it is necessary to determine the inner diameter D2 of the shaft body 451 in accordance with the thickness L23 in the central portion 452b. Accordingly, in a portion other than the central portion 452b, the thickness between the bottom 452a of the first rack tooth 452 and the inner surface of the shaft body 451 becomes thicker than necessary.
  • the first crushed portion 54 is cut in a state where the flat portion 54 b is formed on the inner surface of the first crushed portion 54. Therefore, the inner diameter D1 of the shaft body 51 is determined in accordance with the thickness L3 at the edge 54c of the flat portion 54b of the first crushed portion 54, whereby the inner surface of the first crushed portion 54 and the entire edge 54c of the flat portion 54b.
  • the strength of the first rack teeth 52 can be increased without making the gap between the first rack teeth 52 and the root 52a unnecessarily thick. Accordingly, the inner diameter D1 of the material of the shaft main body 51 can be increased to make the shaft main body 51 thinner, and the rack shaft 50 can be reduced in weight.
  • the second rack teeth 53 are formed in the second crushing portion 55 by cutting using a broaching machine 70 (see FIG. 4C), similarly to the first rack teeth 52.
  • the cutting resistance can be reduced by controlling the cutting allowance, so that the force applied to the shaft main body 51 compared to the case where the second rack teeth 53 are formed by plastic deformation. Can be reduced. Therefore, it is possible to prevent the shaft body 51 from rotating around the axis with respect to the broaching machine 70 during the cutting process. Accordingly, when the second rack teeth 53 are formed after the first rack teeth 52 are formed, the second rack teeth 53 can be formed with a desired phase difference with respect to the first rack teeth 52.
  • the second crushing part 55 is cut with the flat part 55b formed on the inner surface of the second crushing part 55. Therefore, similarly to the first rack teeth 52, the strength of the first rack teeth 52 is increased without increasing the thickness between the inner surface of the second crushing portion 55 and the tooth bottom 53a of the second rack teeth 53 more than necessary. be able to. Accordingly, the inner diameter D1 of the material of the shaft main body 51 can be increased to make the shaft main body 51 thinner, and the rack shaft 50 can be reduced in weight.
  • the first and second rack teeth 52, 53 are formed by cutting the first and second crushing portions 54, 55, respectively, the first and second rack teeth 52, 53 are connected to a common broach. It can be molded using the board 70. Therefore, the manufacturing cost of the rack shaft 50 can be reduced.
  • the first and second rack teeth 52 and 53 are formed.
  • the second crushing portion 55 may be formed to form the second rack teeth 53.
  • the second rack teeth 53 are formed on the second crushing portion 55 by cutting.
  • the cutting resistance can be reduced by controlling the cutting allowance, so that the force applied to the shaft main body 51 compared to the case where the second rack teeth 53 are formed by plastic deformation. Can be reduced. Therefore, the shaft body 51 can be prevented from rotating around the axis during cutting. Therefore, by forming the second rack teeth 53 after forming the first rack teeth 52, the second rack teeth 53 can be formed with a desired phase difference with respect to the first rack teeth 52. The phase angle accuracy of the teeth 52 and the second rack teeth 53 can be improved.
  • the second crushing portion 55 is formed by crushing the shaft body 51 in the radial direction. Therefore, the inner surface of the second crushing portion 55 is deformed inward in the radial direction of the shaft body 51. Therefore, the shaft body 51 can be thinned while increasing the strength of the second rack teeth 53 formed by cutting the second crushing portion 55, and the rack shaft 50 can be reduced in weight.
  • the second crushing portion 55 has a uniform thickness. For this reason, the gap between the inner surface of the second crushing portion 55 and the root 53a of the second rack tooth 53 is not made thicker than necessary over the entire width between both edges of the flat portion 55b in the tooth width direction of the second rack tooth 53. The strength of the second rack teeth 53 can be increased. Therefore, the rack shaft 50 can be reduced in weight.
  • both the first and second rack teeth 52 and 53 are formed in the first and second crushing portions 54 and 55 by cutting. Therefore, both the first and second rack teeth 52 and 53 can be formed using the common broaching machine 70, and the manufacturing cost of the rack shaft 50 can be reduced.
  • a rack shaft 250 according to a second embodiment of the present invention will be described with reference to FIGS. 5, 6A, and 6B.
  • differences from the first embodiment will be mainly described.
  • the same or corresponding components as those described in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
  • the electric power steering apparatus including the rack shaft 250 is substantially the same as the electric power steering apparatus 100 shown in FIG. 1, the description and illustration thereof are omitted here.
  • the rack shaft 250 includes a hollow shaft body 51 and first and second rack teeth 252 and 53 formed on the outer periphery of the shaft body 251.
  • the first rack teeth 252 are formed by forging on a part of the material of the shaft body 51 whose overall length is formed in a cylindrical shape. Specifically, as shown in FIG. 6A, first, the outer surface of the shaft body 51 before processing is sandwiched between the upper mold 81 and the lower mold 82 of the forging machine 80 and the mandrel 84 is inserted into the shaft body 51. To do. Next, the forging die 83 is inserted into the guide hole 81 a of the upper die 81 to crush the shaft body 51. Thereby, a part of the shaft body 51 is plastically deformed, and the first rack teeth 252 are formed.
  • the first rack teeth 252 are formed according to the shape of the forging die 83. Therefore, the first rack teeth 252 can be formed in a complicated shape such as VGR (Variable Gear Ratio).
  • the second rack teeth 53 are formed in the second crushing portion 55 by cutting. Specifically, after the first rack teeth 252 are formed by forging, the outer surface of the shaft body 51 is sandwiched between the upper mold 61 and the lower mold 62 of the processing machine 60. Next, the pressing die 63 is inserted into the guide hole 61 a of the upper die 61 to crush the shaft body 51. Thereby, the 2nd crushing part 55 is formed. Thereafter, a part of the second crushing portion 55 is cut to form a plurality of grooves. Thereby, the 2nd rack tooth
  • the first rack teeth 252 are formed by forging. Therefore, the first rack teeth 252 can be formed according to the shape of the forging die 83, and the rack shaft 250 having the rack teeth having a complicated shape such as VGR can be easily manufactured. Further, since the second rack teeth 53 are formed in the second crushing portion 55 by cutting, the second rack teeth 53 have a desired phase difference with respect to the first rack teeth 252 having a complicated shape previously formed on the shaft body 51 by forging. The rack shaft 250 can be reduced in weight while forming the second rack teeth 53.
  • a rack shaft 350 according to a third embodiment of the present invention will be described with reference to FIG.
  • differences from the first and second embodiments will be mainly described, and in the figure, the same or corresponding configurations as those described in the first and second embodiments are denoted by the same reference numerals. Description is omitted.
  • the electric power steering apparatus including the rack shaft 350 is substantially the same as the electric power steering apparatus 100 shown in FIG. 1, the description and illustration thereof are omitted here.
  • the shaft main body 351 of the rack shaft 350 includes a hollow first shaft portion 351a having a predetermined thickness t1, and a second shaft portion 351b in which the thickness t2 is thicker than the thickness t1 of the first shaft portion 351a. And having.
  • the first shaft portion 351a and the second shaft portion 351b are joined together and formed as an integrated hollow member.
  • the first shaft portion 351a and the second shaft portion 351b are joined by, for example, friction welding.
  • the first rack teeth 252 are formed on the first shaft portion 351a by forging. Since the thickness of the first shaft portion 351a is thin, the first shaft portion 351a can be easily plastically deformed by forging. Therefore, the first rack teeth 252 can be easily formed.
  • the second crushing portion 55 is formed on the second shaft portion 351b, and the second rack teeth 53 are formed on the second crushing portion 55 by cutting. Since the thickness of the 2nd shaft part 351b is thick, the thickness of the 2nd crushing part 55 can be thickened, and the intensity
  • the first and second rack teeth 252 and 53 are formed by a processing method suitable for the first and second shaft portions 351a and 351b having different thicknesses. Therefore, an increase in the weight of the rack shaft 350 can be reduced and the rack shaft 350 can be easily manufactured.
  • the rack shaft 350 by forming the first rack teeth 252 on the first shaft portion 351a and then forming the second rack teeth 53, the first rack teeth 252 having a complicated shape formed by the forging process can be obtained.
  • the rack shaft 250 can be reduced in weight while forming the second rack teeth 53 with a desired phase difference.
  • the second crushing portion 55 is formed by inserting the mandrel 64 into the shaft main body 51 and crushing the shaft main body 51 in the radial direction. Is formed with a flat portion 55b.
  • the present invention is not limited to this, and the second squashed part 55 may be formed in a state where the mandrel 64 is not inserted into the shaft body 51, and the flat part 55 b is formed on the inner surface of the second squashed part 55. It does not have to be.
  • the inner surface of the second crushing portion 55 may protrude or protrude toward the radially inner side of the shaft body 51.
  • the inner surface of the second crushing portion 55 may be recessed toward the radially outer side of the shaft body 51. That is, the inner surface of the second crushed portion 55 only needs to be deformed radially inward and crushed as compared with the shapes of the inner surfaces of the shaft bodies 51 and 351 before processing.
  • the inner surface of the first crushed portion 54 may be crushed as compared with the shapes of the inner surfaces of the shaft main bodies 51 and 351 before processing.
  • the width of the flat portion 55a of the second crushing portion 55 is smaller than the outer diameter of the shaft bodies 51 and 351.
  • This invention is not limited to this, You may form the 2nd crushing part 55 so that the width
  • the first crushed portion 54 is formed so that the width of the flat portion 54a of the first crushed portion 54 is equal to or larger than the outer diameter of the shaft body 51 before processing, and the tooth width of the first rack teeth 52 is increased. Also good.
  • the second crushing portion 55 has substantially the same thickness as that of the shaft bodies 51 and 351 before processing.
  • This invention is not limited to this, You may form the 2nd crushing part 55 so that the thickness of the flat part 55a of the 2nd crushing part 55 may become thicker than the thickness of the shaft main bodies 51 and 351 before a process. In this case, the tooth height of the second rack teeth 53 can be increased.
  • the first crushing part 54 is formed so that the thickness of the flat part 54a of the first crushing part 54 is thicker than the thickness of the shaft body 51 before processing, and the tooth height of the first rack teeth 52 is increased. Also good.
  • a flat portion may be formed in a region other than the first and second rack teeth 52, 53, 252 on the outer surfaces of the shaft bodies 51, 351. By bringing a pressure pad (not shown) into contact with such a flat portion, the rotation of the rack shafts 50, 250, and 350 can be regulated.
  • Such flat portions may be formed over the entire length of the shaft bodies 51 and 351, or may be formed only in the vicinity of the first rack teeth 52 and 252 or the second rack teeth 53.
  • the first rack teeth 52 and 252 and the second rack teeth 53 are formed in the same phase, but the first rack teeth 52 and 252 and the second rack teeth 53 are formed in different phases. May be.
  • the first rack teeth 52 and 252 mesh with the first pinion gear 16 of the output shaft 15 and the second rack teeth 53 mesh with the second pinion gear 25 of the pinion shaft 24.
  • the invention is not limited to this form.
  • the first rack teeth 52 and 252 may mesh with the second pinion gear 25 of the pinion shaft 24, and the second rack teeth 53 may mesh with the first pinion gear 16 of the output shaft 15.
  • the rotational force of the steering wheel 1 is transmitted to the rack shafts 50, 250, 350 via the second rack teeth 53
  • the rotational force of the electric motor 21 is transmitted to the rack shafts 50, 250 via the first rack teeth 52, 252. , 350 may be transmitted.
  • This embodiment relates to rack shafts 50, 250, and 350 that convert the rotational motions of the first and second pinion gears 16 and 25 into linear motions.
  • the rack shafts 50, 250, 350 are provided in the hollow shaft main bodies 51, 351 and the shaft main bodies 51, 351, and the first and second rack teeth 52, 53 that mesh with the first and second pinion gears 16, 25, respectively.
  • , 252 and the shaft main bodies 51, 351 are formed by crushing in the radial direction and have first and second crushing portions 54, 55 including flat portions 54 a, 55 a on the outer surface. Is formed in the second crushing portion 55 by cutting.
  • the second rack teeth 53 are formed in the second crushing portion 55 by cutting.
  • the cutting resistance can be reduced by controlling the cutting allowance, and therefore, in addition to the case where the second rack teeth 53 are formed by plastic deformation, in addition to the shaft main bodies 51 and 351.
  • the force that can be reduced can be reduced. Therefore, it is possible to prevent the shaft bodies 51 and 351 from rotating around the axis during cutting. Therefore, by forming the second rack teeth 53 after forming the first rack teeth 52 and 252, the second rack teeth 53 can be formed with a desired phase difference with respect to the first rack teeth 52 and 252.
  • the second crushing portion 55 is formed by crushing the shaft main bodies 51 and 351 in the radial direction.
  • the shaft main body 51 can be made thin while increasing the strength of the second rack teeth 53 formed by cutting the second crushing portion 55. Accordingly, the rack shafts 50, 250, and 350 can be reduced in weight while improving the phase angle accuracy of the first rack teeth 52 and the second rack teeth 53.
  • the first and second crushing parts 54 and 55 have a uniform thickness.
  • the second crushing portion 55 has a uniform thickness. Therefore, the second rack without increasing the thickness between the inner surface of the second crushed portion 55 and the bottom 53a of the second rack tooth 53 over the entire length between both edges 55c of the flat portion 55b of the second crushed portion 55.
  • the strength of the teeth 53 can be increased. Therefore, the rack shafts 50, 250, and 350 can be reduced in weight.
  • the first and second rack teeth 52, 53 are formed in the first and second crushing portions 54, 55 by cutting.
  • the first and second rack teeth 52 and 53 are formed in the first and second crushing portions 54 and 55 by cutting. Therefore, both the first and second rack teeth 52 and 53 can be formed using the common broaching machine 70, and the manufacturing cost of the rack shaft 50 can be reduced.
  • the first rack teeth 252 are formed on the shaft bodies 51 and 351 by forging, and the second rack teeth 53 are formed on the second crushing portion 55 by cutting.
  • the first rack teeth 252 are formed by forging. Therefore, the first rack teeth 252 can be formed according to the shape of the forging die 83, and the rack shafts 250 and 350 having the first rack teeth 252 having a complicated shape such as VGR (Variable Gear Ratio) can be easily obtained. Can be manufactured. Further, since the second rack teeth 53 are formed in the second crushing portion 55 by cutting, a desired phase difference with respect to the first rack teeth 252 having a complicated shape previously formed on the shaft body 351 by forging. The rack shafts 250 and 350 can be reduced in weight while forming the second rack teeth 53.
  • VGR Very Gear Ratio
  • the shaft body 351 has a first shaft portion 351a and a second shaft portion 351b having a thickness t2 larger than the thickness t1 of the first shaft portion 351a, and the first rack teeth 252 are
  • the second crushing portion 55 is provided on the second shaft portion 351b.
  • the first shaft portion 351a since the thickness t1 of the first shaft portion 351a is thin, the first shaft portion 351a can be easily plastically deformed by forging, and the first rack teeth 252 can be easily formed.
  • the 2nd crushing part 55 is provided in the 2nd shaft part 351b which has thick thickness t2. Therefore, the strength of the second crushed portion 55 can be increased, and damage to the second crushed portion 55 when the second rack teeth 53 are formed by cutting can be prevented. Therefore, the rack shaft 350 can be easily manufactured.
  • the shaft main bodies 51 and 351 are formed of one hollow member that does not include a joint portion.
  • the shaft main bodies 51 and 351 are formed of one hollow member that does not include a joint portion.
  • a hollow member that does not include a joint portion for example, a seamless tube or an electric sewing tube can be used. Since the seamless pipe and the electric resistance welded pipe do not include the joint portion, the joining work can be omitted.
  • the present embodiment relates to a method of manufacturing the rack shafts 50, 250, 350 including the first and second rack teeth 52, 53, 252 that mesh with the first and second pinion gears 16, 25, respectively.
  • the manufacturing method of the rack shafts 50, 250, and 350 includes a first rack tooth forming step of forming the first rack teeth 52 and 252 on the hollow shaft main bodies 51 and 351, and the second rack teeth 53 on the shaft main bodies 51 and 351.
  • a second rack tooth forming step wherein the second rack tooth forming step includes crushing the shaft bodies 51 and 351 in the radial direction to form the second crushing portion 55, and the first rack teeth 52, Forming the second rack teeth 53 on the second crushing portion 55 by cutting after the 252 is formed.
  • the second rack teeth 53 are formed on the second crushing portion 55 by cutting.
  • the shaft main bodies 51 and 351 can be prevented from rotating around the axis during the cutting process, and the second rack teeth 53 can be formed with a desired phase difference with respect to the first rack teeth 52 and 252.
  • the second crushing portion 55 is formed by crushing the shaft main bodies 51 and 351 in the radial direction. Therefore, the inner surface of the second crushing portion 55 is deformed radially inward of the shaft main bodies 51 and 351.
  • the shaft main bodies 51 and 351 can be thinned while increasing the strength of the second rack teeth 53.
  • the rack shafts 50, 250, 350 can be reduced in weight while improving the phase angle accuracy of the first rack teeth 52, 252 and the second rack teeth 53.
  • the first rack tooth forming step includes forming the first rack teeth 52 and 252 on the shaft bodies 51 and 351 by forging.
  • the first rack teeth 252 are formed by forging. Therefore, the first rack teeth 252 can be formed according to the shape of the forging die 83, and the rack shafts 250 and 350 having the first rack teeth 252 having a complicated shape such as VGR (Variable Gear Ratio) can be easily obtained. Can be manufactured.
  • VGR Variable Gear Ratio
  • the second rack teeth 53 are formed on the second crushing portion 55 after the first rack teeth 252 are formed by forging, a desired position is obtained with respect to the first rack teeth 252 having a complicated shape.
  • the rack shafts 250 and 350 can be reduced in weight while forming the second rack teeth 53 by the phase difference.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Power Steering Mechanism (AREA)
  • Gears, Cams (AREA)
  • Forging (AREA)

Abstract

This rack shaft (50) is provided with: a hollow shaft body (51); and first and second rack teeth (52, 53) respectively meshing with first and second pinion gears (16, 25). The shaft body (51) has a second compressed section (55) which is formed compressed radially and which includes a flat section (55a) on the outer surface thereof. The second rack teeth (53) are formed by cutting on the second compressed section (55).

Description

ラックシャフト及びラックシャフトの製造方法Rack shaft and method for manufacturing rack shaft
　本発明は、ラックシャフト及びラックシャフトの製造方法に関する。 The present invention relates to a rack shaft and a method for manufacturing the rack shaft.
　電動パワーステアリング装置として、ドライバによる操舵トルクと電動モータによる操舵補助トルクとがそれぞれ独立してラックシャフトに入力されるデュアルピニオン式の電動パワーステアリング装置が知られている。デュアルピニオン式の電動パワーステアリング装置において、ラックシャフトを中空又は円筒状の部材から形成して軽量化することが提案されている（ＪＰ２００４－５２３３６５Ａ、ＪＰ２０１４－１２４７６７Ａ）。 As the electric power steering device, a dual pinion type electric power steering device in which steering torque by a driver and steering assist torque by an electric motor are independently input to a rack shaft is known. In a dual pinion type electric power steering apparatus, it has been proposed to reduce the weight by forming a rack shaft from a hollow or cylindrical member (JP 2004-523365A, JP 2014-124767A).
　ＪＰ２００４－５２３３６５Ａに開示されるラックシャフトの製造では、まず、円筒形のシャフトの一部を鍛造金型内に配置し、鍛造加工によりシャフトに第１ラック歯を形成する。その後、鍛造金型からシャフトを取り出し、鍛造金型内にシャフトの別の部分を配置し、鍛造加工によりシャフトに第２ラック歯を形成する。 In manufacturing the rack shaft disclosed in JP2004-523365A, first, a part of a cylindrical shaft is placed in a forging die, and first rack teeth are formed on the shaft by forging. Thereafter, the shaft is taken out from the forging die, another portion of the shaft is disposed in the forging die, and second rack teeth are formed on the shaft by forging.
　ＪＰ２０１４－１２４７６７Ａに開示されるラックシャフトの製造では、まず、鍛造加工により中空の第１バーに第１ラック歯を形成する。次に、この第１シャフトに摩擦圧接により中空の第２シャフトを接合し、切削加工により第２シャフトに第２ラック歯を形成する。 In manufacturing the rack shaft disclosed in JP2014-124767A, first, first rack teeth are formed on a hollow first bar by forging. Next, a hollow second shaft is joined to the first shaft by friction welding, and second rack teeth are formed on the second shaft by cutting.
　ＪＰ２００４－５２３３６５Ａに開示されるラックシャフトの製造では、第１及び第２ラック歯の両方が鍛造加工により形成される。鍛造加工では、シャフトに加えられる圧力の大きさに応じてシャフトが塑性変形する。そのため、ラック歯を形成するためには大きい圧力をシャフトに加える必要があり、圧力をシャフトに加える際にシャフトが金型に対して軸周りに回転することがある。第２ラック歯の形成時にシャフトが金型に対して軸周りに回転すると、第１ラック歯に対する第２ラック歯の位相角がずれ、第１ラック歯と第２ラック歯の位相角精度が低下する。 In manufacturing the rack shaft disclosed in JP 2004-523365A, both the first and second rack teeth are formed by forging. In the forging process, the shaft is plastically deformed according to the pressure applied to the shaft. Therefore, in order to form rack teeth, it is necessary to apply a large pressure to the shaft, and when the pressure is applied to the shaft, the shaft may rotate around the axis with respect to the mold. If the shaft rotates about the axis with respect to the mold at the time of forming the second rack tooth, the phase angle of the second rack tooth with respect to the first rack tooth shifts, and the phase angle accuracy of the first rack tooth and the second rack tooth decreases. To do.
　ＪＰ２０１４－１２４７６７Ａに開示されるラックシャフトの製造では、第２ラック歯は、外面及び内面が円形の第２シャフトに切削加工により形成される。そのため、第２ラック歯の歯底と第２シャフトの内面との間の厚みは、第２ラック歯の歯幅方向における端部から中央部に向うにつれ減少し、中央部における強度が最も低い。中央部における強度を高めるために第２シャフトを厚くすると、中央部以外の部分が必要以上に厚くなり、ラックシャフトの重量が増加する。 In the manufacture of the rack shaft disclosed in JP2014-124767A, the second rack teeth are formed by cutting a second shaft whose outer surface and inner surface are circular. Therefore, the thickness between the bottom of the second rack teeth and the inner surface of the second shaft decreases from the end in the tooth width direction of the second rack teeth toward the center, and the strength at the center is the lowest. If the second shaft is made thicker in order to increase the strength at the central portion, the portion other than the central portion becomes thicker than necessary, and the weight of the rack shaft increases.
　本発明は、第１ラック歯と第２ラック歯の位相角精度を向上させつつラックシャフトを軽量化することを目的とする。 An object of the present invention is to reduce the weight of the rack shaft while improving the phase angle accuracy of the first rack teeth and the second rack teeth.
　本発明は、第１及び第２ピニオンギアの回転運動を直線運動に変換するラックシャフトに係る。本発明のある態様によれば、ラックシャフトは、中空のシャフト本体と、シャフト本体に設けられ、第１及び第２ピニオンギアにそれぞれ噛み合う第１及び第２ラック歯と、を備え、シャフト本体は、径方向に潰すことによって形成され外面に平坦部を含む潰し部を有し、第１及び第２ラック歯の少なくとも一方は、潰し部に切削加工により形成される。 The present invention relates to a rack shaft that converts the rotational motion of the first and second pinion gears into a linear motion. According to an aspect of the present invention, the rack shaft includes a hollow shaft body, and first and second rack teeth provided on the shaft body and meshing with the first and second pinion gears, respectively. The crushed portion is formed by crushing in the radial direction and includes a flat portion on the outer surface, and at least one of the first and second rack teeth is formed in the crushed portion by cutting.
　また、本発明は、第１及び第２ピニオンギアにそれぞれ噛み合う第１及び第２ラック歯を備えるラックシャフトの製造方法に係る。本発明のある態様によれば、ラックシャフトの製造方法は、中空のシャフト本体に第１ラック歯を形成する第１ラック歯形成工程と、シャフト本体に第２ラック歯を形成する第２ラック歯形成工程と、を備え、第２ラック歯形成工程は、シャフト本体を径方向に押し潰すことによって、外面に平坦部を含む潰し部を形成することと、第１ラック歯を形成した後に、潰し部に切削加工により第２ラック歯を形成することと、を含む。 Further, the present invention relates to a method for manufacturing a rack shaft having first and second rack teeth that mesh with first and second pinion gears, respectively. According to an aspect of the present invention, a method for manufacturing a rack shaft includes a first rack tooth forming step for forming a first rack tooth on a hollow shaft body, and a second rack tooth for forming a second rack tooth on the shaft body. And forming a crushing portion including a flat portion on the outer surface by crushing the shaft main body in the radial direction, and crushing after forming the first rack teeth. Forming a second rack tooth on the part by cutting.
図１は、本発明の第１実施形態に係るラックシャフトを備える電動パワーステアリング装置の構成図である。FIG. 1 is a configuration diagram of an electric power steering apparatus including a rack shaft according to the first embodiment of the present invention. 図２は、本発明の第１実施形態に係るラックシャフトの断面図である。FIG. 2 is a cross-sectional view of the rack shaft according to the first embodiment of the present invention. 図３Ａは、図２に示すＩＩＩＡ－ＩＩＩＡ線に沿う断面図である。3A is a cross-sectional view taken along line IIIA-IIIA shown in FIG. 図３Ｂは、図４Ａに示すＩＩＩＢ－ＩＩＩＢ線に沿う断面図である。3B is a cross-sectional view taken along line IIIB-IIIB shown in FIG. 4A. 図３Ｃは、図２に示すＩＩＩＣ－ＩＩＩＣ線に沿う断面図である。3C is a cross-sectional view taken along the line IIIC-IIIC shown in FIG. 図４Ａは、図２に示すラックシャフトを製造する方法を説明するための図であり、シャフト本体に第１潰し部を形成する工程を示す。FIG. 4A is a view for explaining a method of manufacturing the rack shaft shown in FIG. 2, and shows a step of forming a first crushing portion in the shaft body. 図４Ｂは、図２に示すラックシャフトを製造する方法を説明するための図であり、シャフト本体に第２潰し部を形成する工程を示す。FIG. 4B is a view for explaining a method of manufacturing the rack shaft shown in FIG. 2 and shows a step of forming the second crushing portion in the shaft body. 図４Ｃは、図２に示すラックシャフトを製造する方法を説明するための図であり、第１潰し部に第１ラック歯を形成する工程を示す。FIG. 4C is a view for explaining a method of manufacturing the rack shaft shown in FIG. 2 and shows a step of forming first rack teeth in the first crushing portion. 図５は、本発明の第２実施形態に係るラックシャフトの断面図であり、図２に対応して示す。FIG. 5 is a cross-sectional view of a rack shaft according to the second embodiment of the present invention, corresponding to FIG. 図６Ａは、図５に示すラックシャフトを製造する方法を説明するための図であり、シャフト本体に第１ラック歯を形成する工程を示す。FIG. 6A is a diagram for explaining a method of manufacturing the rack shaft shown in FIG. 5 and shows a step of forming first rack teeth on the shaft body. 図６Ｂは、図５に示すラックシャフトを製造する方法を説明するための図であり、シャフト本体に潰し部を形成する工程を示す。FIG. 6B is a view for explaining a method of manufacturing the rack shaft shown in FIG. 5 and shows a step of forming a crushing portion in the shaft body. 図７は、本発明の第３実施形態に係るラックシャフトの断面図であり、図２に対応して示す。FIG. 7 is a cross-sectional view of a rack shaft according to the third embodiment of the present invention, corresponding to FIG. 図８Ａは、潰し部の変形例を示す断面図であり、図３Ｃに対応して示す。FIG. 8A is a cross-sectional view showing a modified example of the crushed portion, and corresponds to FIG. 3C. 図８Ｂは、潰し部の別の変形例を示す断面図であり、図３Ｃに対応して示す。FIG. 8B is a cross-sectional view showing another modified example of the crushed portion, corresponding to FIG. 3C. 図９は、比較例に係るラックシャフトの断面図であり、図３Ｃに対応して示す。FIG. 9 is a cross-sectional view of a rack shaft according to a comparative example, corresponding to FIG. 3C.
　以下、図面を参照して、本発明の実施形態について説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
　＜第１実施形態＞
　図１は、本発明の第１実施形態に係るラックシャフト５０を備える電動パワーステアリング装置１００の構成図である。電動パワーステアリング装置１００は、運転者による操舵力と電動モータ２１によるアシスト駆動力とがそれぞれ独立してラックシャフト５０に入力されるデュアルピニオン式の電動パワーステアリング装置である。 <First Embodiment>
FIG. 1 is a configuration diagram of an electric power steering apparatus 100 including a rack shaft 50 according to the first embodiment of the present invention. The electric power steering device 100 is a dual pinion type electric power steering device in which the steering force by the driver and the assist driving force by the electric motor 21 are independently input to the rack shaft 50.
　電動パワーステアリング装置１００は、運転者によって操舵力が入力されるステアリングホイール１の回転に応じて車両の車輪２を転舵させる転舵機構１０と、運転者の操舵力をアシストするアシスト機構２０と、操舵力のアシスト量を制御する制御装置３０と、を備える。 The electric power steering apparatus 100 includes a steering mechanism 10 that steers the wheels 2 of the vehicle according to the rotation of the steering wheel 1 to which the steering force is input by the driver, and an assist mechanism 20 that assists the driver's steering force. And a control device 30 for controlling the assist amount of the steering force.
　転舵機構１０は、ステアリングホイール１に連結されステアリングホイール１の回転に応じて回転するステアリングシャフト１１と、ステアリングシャフト１１の回転に応じて車両の車輪２を転舵させるラックシャフト５０と、を有する。ラックシャフト５０は、タイロッド３を介して車輪２に連結される。 The steering mechanism 10 includes a steering shaft 11 that is connected to the steering wheel 1 and rotates according to the rotation of the steering wheel 1, and a rack shaft 50 that steers the vehicle wheel 2 according to the rotation of the steering shaft 11. . The rack shaft 50 is connected to the wheel 2 via the tie rod 3.
　ステアリングシャフト１１は、ステアリングホイール１に連結された入力シャフト１３と、入力シャフト１３にトーションバー１４を介して連結された出力シャフト１５と、を有する。出力シャフト１５には、ラックシャフト５０と噛み合う第１ピニオンギア１６が設けられる。 The steering shaft 11 has an input shaft 13 connected to the steering wheel 1 and an output shaft 15 connected to the input shaft 13 via a torsion bar 14. The output shaft 15 is provided with a first pinion gear 16 that meshes with the rack shaft 50.
　アシスト機構２０は、アシスト力の動力源である電動モータ２１と、電動モータ２１の出力シャフトに連結されたウォームシャフト２２と、ウォームシャフト２２と噛み合うウォームホイール２３と、ウォームホイール２３に連結されるピニオンシャフト２４と、を有する。ピニオンシャフト２４にはラックシャフト５０と噛み合う第２ピニオンギア２５が設けられる。 The assist mechanism 20 includes an electric motor 21 that is a power source of assist force, a worm shaft 22 that is coupled to the output shaft of the electric motor 21, a worm wheel 23 that meshes with the worm shaft 22, and a pinion that is coupled to the worm wheel 23. And a shaft 24. The pinion shaft 24 is provided with a second pinion gear 25 that meshes with the rack shaft 50.
　制御装置３０は、入力シャフト１３と出力シャフト１５との相対回転に基づいてトーションバー１４に付与される操舵トルクを検出するトルクセンサ３１と、ピニオンシャフト２４の回転角度を検出する回転角度センサ３２と、ステアリングホイール１の回転角度（操舵角度）を検出する操舵角度センサ３４と、レゾルバによって構成され電動モータ２１の回転角度を検出するモータ回転角度センサ３５と、電動モータ２１の作動を制御するコントローラ３３と、を有する。 The control device 30 includes a torque sensor 31 that detects the steering torque applied to the torsion bar 14 based on the relative rotation between the input shaft 13 and the output shaft 15, and a rotation angle sensor 32 that detects the rotation angle of the pinion shaft 24. The steering angle sensor 34 that detects the rotation angle (steering angle) of the steering wheel 1, the motor rotation angle sensor 35 that is configured by a resolver and detects the rotation angle of the electric motor 21, and the controller 33 that controls the operation of the electric motor 21. And having.
　コントローラ３３は、トルクセンサ３１によって検出される操舵トルクと、モータ回転角度センサ３５によって検出される電動モータ２１の回転角度と、に基づいて電動モータ２１の駆動を制御する。なお、コントローラ３３は、操舵トルク及び電動モータ２１の回転角度に加えて、操舵角度センサ３４によって検出される操舵角度を考慮して、電動モータ２１の駆動を制御してもよい。さらに、コントローラ３３は、回転角度センサ３２によって検出されるピニオンシャフト２４の回転角度を考慮して電動モータ２１の駆動を制御してもよい。 The controller 33 controls the driving of the electric motor 21 based on the steering torque detected by the torque sensor 31 and the rotation angle of the electric motor 21 detected by the motor rotation angle sensor 35. The controller 33 may control the driving of the electric motor 21 in consideration of the steering angle detected by the steering angle sensor 34 in addition to the steering torque and the rotation angle of the electric motor 21. Further, the controller 33 may control the driving of the electric motor 21 in consideration of the rotation angle of the pinion shaft 24 detected by the rotation angle sensor 32.
　回転角度センサ３２によって検出されるピニオンシャフト２４の回転角度を用いれば、車輪２の転舵角を正確に把握することができる。回転角度センサ３２の検出結果は、車両の横滑り等を抑制するＶＤＣ（Ｖｅｈｉｃｌｅ　Ｄｙｎａｍｉｃｓ　Ｃｏｎｔｒｏｌ）等の制御においても用いられる。 If the rotation angle of the pinion shaft 24 detected by the rotation angle sensor 32 is used, the turning angle of the wheel 2 can be accurately grasped. The detection result of the rotation angle sensor 32 is also used in control of a VDC (Vehicle Dynamics Control) or the like that suppresses a side slip or the like of the vehicle.
　ラックシャフト５０は、シャフト本体５１と、シャフト本体５１の外周に設けられる第１及び第２ラック歯５２，５３と、を備える。第１ラック歯５２は、出力シャフト１５の第１ピニオンギア１６に噛み合い、第２ラック歯５３は、ピニオンシャフト２４の第２ピニオンギア２５に噛み合う。シャフト本体５１は、タイロッド３を介して車輪２に連結される。 The rack shaft 50 includes a shaft main body 51 and first and second rack teeth 52 and 53 provided on the outer periphery of the shaft main body 51. The first rack teeth 52 mesh with the first pinion gear 16 of the output shaft 15, and the second rack teeth 53 mesh with the second pinion gear 25 of the pinion shaft 24. The shaft body 51 is connected to the wheel 2 via the tie rod 3.
　ステアリングホイール１の回転力は、入力シャフト１３、トーションバー１４を介して出力シャフト１５に伝達される。出力シャフト１５の回転力は、第１ピニオンギア１６を介してラックシャフト５０の軸方向（車両の左右方向）の力に変換されてラックシャフト５０に伝達される。このため、ステアリングホイール１が操舵されると、ラックシャフト５０が軸方向に移動し、車両の車輪２がラックシャフト５０の移動に応じて転蛇される。 Rotational force of the steering wheel 1 is transmitted to the output shaft 15 via the input shaft 13 and the torsion bar 14. The rotational force of the output shaft 15 is converted into a force in the axial direction of the rack shaft 50 (the left-right direction of the vehicle) via the first pinion gear 16 and transmitted to the rack shaft 50. For this reason, when the steering wheel 1 is steered, the rack shaft 50 moves in the axial direction, and the vehicle wheel 2 is snaked according to the movement of the rack shaft 50.
　電動モータ２１の回転力は、ウォームシャフト２２、ウォームホイール２３を介してピニオンシャフト２４に伝達される。ピニオンシャフト２４の回転力は、ラックシャフト５０の軸方向（車両の左右方向）の力に変換されてラックシャフト５０に伝達される。このため、電動モータ２１が回転駆動されると、ラックシャフト５０に操舵補助推力が付与され、ステアリングホイール１の操舵が補助される。 Rotational force of the electric motor 21 is transmitted to the pinion shaft 24 via the worm shaft 22 and the worm wheel 23. The rotational force of the pinion shaft 24 is converted into a force in the axial direction of the rack shaft 50 (the left-right direction of the vehicle) and transmitted to the rack shaft 50. For this reason, when the electric motor 21 is rotationally driven, a steering assist thrust is applied to the rack shaft 50 and the steering of the steering wheel 1 is assisted.
　ラックシャフト５０は、金属材料（例えば炭素鋼）から形成される。図２に示すように、ラックシャフト５０のシャフト本体５１は、中空に形成される。シャフト本体５１は、接合部を含まない１つの中空の部材として形成されていてもよいし、複数の中空の部材を接合することによって形成されていてもよい。ラックシャフト５０が接合部を含まない１つの中空の部材として形成されている場合には、ラックシャフト５０の同軸度を確保しやすい。 The rack shaft 50 is formed from a metal material (for example, carbon steel). As shown in FIG. 2, the shaft body 51 of the rack shaft 50 is formed in a hollow shape. The shaft body 51 may be formed as a single hollow member that does not include a joint portion, or may be formed by joining a plurality of hollow members. When the rack shaft 50 is formed as one hollow member that does not include a joint portion, it is easy to ensure the coaxiality of the rack shaft 50.
　接合部を含まない中空部材としては、例えば、シームレス管や電縫管を使用することができる。シームレス管や電縫管は、接合部を含まないので、接合作業を省略することができる。さらに、シームレス管や電縫管にスウェージング加工や引抜加工といった加工を施してもよい。 For example, a seamless tube or an electric resistance tube can be used as the hollow member that does not include the joint portion. Since the seamless pipe and the electric resistance welded pipe do not include the joint portion, the joining work can be omitted. Furthermore, you may perform processes, such as a swaging process and a drawing process, to a seamless pipe or an electric sewing pipe.
　シャフト本体５１は、外面に平坦部５４ａ，５５ａを有する第１及び第２潰し部５４，５５と、第１及び第２潰し部５４，５５との間に設けられる中間部５６と、を含む。図３Ａに示すように、中間部５６の外面及び内面は円形に形成される。図２に示すように、第１及び第２ラック歯５２，５３は、それぞれ、第１及び第２潰し部５４，５５に形成される。 The shaft body 51 includes first and second crushing parts 54 and 55 having flat parts 54a and 55a on the outer surface, and an intermediate part 56 provided between the first and second crushing parts 54 and 55. As shown in FIG. 3A, the outer surface and the inner surface of the intermediate portion 56 are formed in a circular shape. As shown in FIG. 2, the 1st and 2nd rack teeth 52 and 53 are formed in the 1st and 2nd crushing parts 54 and 55, respectively.
　第１潰し部５４は、図４Ａに示すように、全長が円筒状に形成されたシャフト本体５１の素材の一部を径方向に潰すことによって形成される。具体的には、まず、シャフト本体５１の素材の外面を加工機６０の上金型６１と下金型６２とにより挟持する。次に、上金型６１の案内孔６１ａに押し型６３を挿入してシャフト本体５１の素材の一部を径方向に押し潰す。これにより、第１潰し部５４がシャフト本体５１に形成される。シャフト本体５１の一部が押し潰されて第１潰し部５４が形成されるため、図３Ｂに示すように、第１潰し部５４の外面には平坦部５４ａが形成される。 As shown in FIG. 4A, the first crushing portion 54 is formed by crushing a part of the material of the shaft main body 51 whose entire length is formed in a cylindrical shape in the radial direction. Specifically, first, the outer surface of the material of the shaft body 51 is sandwiched between the upper mold 61 and the lower mold 62 of the processing machine 60. Next, the pressing die 63 is inserted into the guide hole 61 a of the upper die 61 to crush a part of the material of the shaft body 51 in the radial direction. Thereby, the first crushing portion 54 is formed in the shaft main body 51. Since a part of the shaft body 51 is crushed to form the first crushed portion 54, a flat portion 54a is formed on the outer surface of the first crushed portion 54 as shown in FIG. 3B.
　第１潰し部５４を形成する際には、図４Ａに示すように、シャフト本体５１にマンドレル６４が挿入される。マンドレル６４の外面には平坦部６４ａが形成され、押し型６３は、マンドレル６４の平坦部６４ａに向ってシャフト本体５１を押し潰す。したがって、図３Ｂに示すように、第１潰し部５４の内面には平坦部５４ｂが形成される。第１潰し部５４の外面及び内面に平坦部５４ａ，５４ｂが形成されるので、第１潰し部５４は一様の厚みを有する。 When forming the first crushing portion 54, the mandrel 64 is inserted into the shaft body 51 as shown in FIG. 4A. A flat portion 64 a is formed on the outer surface of the mandrel 64, and the pressing die 63 crushes the shaft body 51 toward the flat portion 64 a of the mandrel 64. Therefore, as shown in FIG. 3B, a flat portion 54 b is formed on the inner surface of the first squashed portion 54. Since the flat portions 54a and 54b are formed on the outer and inner surfaces of the first squashed portion 54, the first squashed portion 54 has a uniform thickness.
　図４Ｂに示すように、第２潰し部５５は、第１潰し部５４と同様に、円筒状に形成されたシャフト本体５１の素材の一部を径方向に潰すことによって形成される。そのため、第２潰し部５５の外面及び内面には、第１潰し部５４と同様に平坦部５５ａ，５５ｂが形成され、第２潰し部５５は一様の厚みを有する。 As shown in FIG. 4B, the second crushing portion 55 is formed by crushing a part of the material of the shaft body 51 formed in a cylindrical shape in the radial direction, like the first crushing portion 54. Therefore, flat portions 55a and 55b are formed on the outer surface and the inner surface of the second crushed portion 55 similarly to the first crushed portion 54, and the second crushed portion 55 has a uniform thickness.
　図４Ｃに示すように、第１ラック歯５２は、第１潰し部５４に切削加工により形成される。具体的には、ブローチ盤７０を用いて第１潰し部５４の一部を切削して複数の溝を形成する。これにより、第１ラック歯５２が形成される。 As shown in FIG. 4C, the first rack teeth 52 are formed in the first crushing portion 54 by cutting. Specifically, a part of the 1st crushing part 54 is cut using the broaching board 70, and a some groove | channel is formed. Thereby, the first rack teeth 52 are formed.
　図３Ｃに示すように、第１潰し部５４の平坦部５４ａの幅は、第１ラック歯５２の歯幅Ｌ１に相当する。また、切削加工により第１潰し部５４に形成される溝の深さは、第１ラック歯５２の歯丈Ｌ２に相当する。切削加工により第１潰し部５４に形成される溝の底面は、第１ラック歯５２の歯底５２ａとなる。 As shown in FIG. 3C, the width of the flat portion 54 a of the first crushing portion 54 corresponds to the tooth width L <b> 1 of the first rack tooth 52. Further, the depth of the groove formed in the first crushing portion 54 by the cutting process corresponds to the tooth height L <b> 2 of the first rack tooth 52. The bottom surface of the groove formed in the first crushing portion 54 by cutting is a tooth bottom 52 a of the first rack tooth 52.
　なお、第１潰し部５４の平坦部５４ａに切削加工を施して第１ラック歯５２を形成した後に、第１ラック歯５２の歯先にさらに切削加工を施してもよい。この場合には、切削加工後の平坦部５４ａの幅が第１ラック歯５２の歯幅Ｌ１に相当する。 In addition, after performing the cutting process on the flat part 54a of the first crushing part 54 to form the first rack teeth 52, the tooth tips of the first rack teeth 52 may be further cut. In this case, the width of the flat portion 54 a after cutting corresponds to the tooth width L 1 of the first rack tooth 52.
　切削加工による第１ラック歯５２の形成では、切削代のコントロールにより切削抵抗を減らすことができるので、塑性変形により第１ラック歯５２を形成する場合と比較して、シャフト本体５１に加えられる力を小さくすることができる。したがって、切削加工時にシャフト本体５１がブローチ盤７０に対して移動するのを防止することができ、第１ラック歯５２を所望の位相角に形成することができる。 In the formation of the first rack teeth 52 by cutting, since the cutting resistance can be reduced by controlling the cutting allowance, the force applied to the shaft main body 51 compared to the case where the first rack teeth 52 are formed by plastic deformation. Can be reduced. Therefore, the shaft body 51 can be prevented from moving with respect to the broaching machine 70 during the cutting process, and the first rack teeth 52 can be formed at a desired phase angle.
　また、第１潰し部５４の内面に平坦部５４ｂが形成される。そのため、平坦部５４ｂに沿って第１潰し部５４を切削して第１ラック歯５２を形成することにより、第１ラック歯５２の歯底５２ａと第１潰し部５４の内面との間の厚みＬ３は、第１ラック歯５２の歯幅方向にほぼ一様となる。 Further, a flat portion 54 b is formed on the inner surface of the first squashed portion 54. Therefore, the thickness between the bottom 52a of the first rack tooth 52 and the inner surface of the first crushed part 54 is formed by cutting the first crushed part 54 along the flat part 54b to form the first rack tooth 52. L3 is substantially uniform in the tooth width direction of the first rack teeth 52.
　ここで、比較例に係るラックシャフト４５０について、図９を参照して説明する。図９は、ラックシャフト４５０の断面図であり、図３Ｃに対応して示す。ラックシャフト４５０では、第１ラック歯４５２は、外面及び内面が円形のシャフト本体４５１の素材に切削加工により形成される。具体的には、まず、シャフト本体４５１の素材に切削加工により外面に平坦部４５４ａを有する切削部４５４を形成する。その後、切削加工により切削部４５４に複数の溝を形成する。これにより、第１ラック歯４５２が形成される。そのため、切削部４５４の平坦部４５４ａの幅は、第１ラック歯４５２の歯幅Ｌ２１に相当する。また、切削部４５４に形成される溝の深さは、第１ラック歯４５２の歯丈Ｌ２２に相当する。 Here, a rack shaft 450 according to a comparative example will be described with reference to FIG. FIG. 9 is a cross-sectional view of the rack shaft 450, corresponding to FIG. 3C. In the rack shaft 450, the first rack teeth 452 are formed by cutting a material of the shaft body 451 whose outer surface and inner surface are circular. Specifically, first, a cutting portion 454 having a flat portion 454a on the outer surface is formed on the material of the shaft body 451 by cutting. Thereafter, a plurality of grooves are formed in the cutting portion 454 by cutting. Thereby, the first rack teeth 452 are formed. Therefore, the width of the flat portion 454a of the cutting portion 454 corresponds to the tooth width L21 of the first rack tooth 452. Further, the depth of the groove formed in the cutting part 454 corresponds to the tooth height L22 of the first rack tooth 452.
　シャフト本体４５１の内面が円形の状態でシャフト本体４５１が切削されるので、第１ラック歯４５２の歯底４５２ａとシャフト本体４５１の内面との間の厚みは、第１ラック歯４５２の歯幅方向における両端部から中央部４５２ｂに向うにつれ減少する。つまり、中央部４５２ｂにおける厚みＬ２３が最も小さい。 Since the shaft main body 451 is cut while the inner surface of the shaft main body 451 is circular, the thickness between the bottom 452a of the first rack tooth 452 and the inner surface of the shaft main body 451 is the tooth width direction of the first rack tooth 452. It decreases as it goes from both ends to the central portion 452b. That is, the thickness L23 at the central portion 452b is the smallest.
　第１ラック歯４５２の強度は、歯底４５２ａとシャフト本体４５１の内面との間の厚みに依存する。第１ラック歯４５２に所望の強度を持たせるためには、中央部４５２ｂにおける厚みＬ２３に合わせてシャフト本体４５１の内径Ｄ２を定める必要がある。したがって、中央部４５２ｂ以外の部分では、第１ラック歯４５２の歯底４５２ａとシャフト本体４５１の内面との間の厚みは必要以上に厚くなる。 The strength of the first rack teeth 452 depends on the thickness between the tooth bottom 452a and the inner surface of the shaft body 451. In order to give the first rack teeth 452 a desired strength, it is necessary to determine the inner diameter D2 of the shaft body 451 in accordance with the thickness L23 in the central portion 452b. Accordingly, in a portion other than the central portion 452b, the thickness between the bottom 452a of the first rack tooth 452 and the inner surface of the shaft body 451 becomes thicker than necessary.
　本実施形態に係るラックシャフト５０では、図３Ｃ及び図４Ｃに示すように、第１潰し部５４の内面に平坦部５４ｂが形成された状態で、第１潰し部５４が切削される。そのため、シャフト本体５１の内径Ｄ１を第１潰し部５４の平坦部５４ｂの縁５４ｃにおける厚みＬ３に合わせて定めることで、平坦部５４ｂの両縁５４ｃ間の全体にわたって第１潰し部５４の内面と第１ラック歯５２の歯底５２ａとの間を必要以上に厚くすることなく第１ラック歯５２の強度を高めることができる。したがって、シャフト本体５１の素材の内径Ｄ１を大きくしてシャフト本体５１を薄くすることができ、ラックシャフト５０を軽量化することができる。 In the rack shaft 50 according to the present embodiment, as shown in FIG. 3C and FIG. 4C, the first crushed portion 54 is cut in a state where the flat portion 54 b is formed on the inner surface of the first crushed portion 54. Therefore, the inner diameter D1 of the shaft body 51 is determined in accordance with the thickness L3 at the edge 54c of the flat portion 54b of the first crushed portion 54, whereby the inner surface of the first crushed portion 54 and the entire edge 54c of the flat portion 54b The strength of the first rack teeth 52 can be increased without making the gap between the first rack teeth 52 and the root 52a unnecessarily thick. Accordingly, the inner diameter D1 of the material of the shaft main body 51 can be increased to make the shaft main body 51 thinner, and the rack shaft 50 can be reduced in weight.
　第２ラック歯５３は、第１ラック歯５２と同様に、ブローチ盤７０（図４Ｃ参照）を用いた切削加工により第２潰し部５５に形成される。切削加工による第２ラック歯５３の形成では、切削代のコントロールにより切削抵抗を減らすことができるので、塑性変形により第２ラック歯５３を形成する場合と比較して、シャフト本体５１に加えられる力を小さくすることができる。したがって、切削加工時にシャフト本体５１がブローチ盤７０に対して軸周りに回転するのを防止することができる。これにより、第１ラック歯５２を形成した後に第２ラック歯５３を形成する際に、第１ラック歯５２に対して所望の位相差で第２ラック歯５３を形成することができる。 The second rack teeth 53 are formed in the second crushing portion 55 by cutting using a broaching machine 70 (see FIG. 4C), similarly to the first rack teeth 52. In the formation of the second rack teeth 53 by cutting, the cutting resistance can be reduced by controlling the cutting allowance, so that the force applied to the shaft main body 51 compared to the case where the second rack teeth 53 are formed by plastic deformation. Can be reduced. Therefore, it is possible to prevent the shaft body 51 from rotating around the axis with respect to the broaching machine 70 during the cutting process. Accordingly, when the second rack teeth 53 are formed after the first rack teeth 52 are formed, the second rack teeth 53 can be formed with a desired phase difference with respect to the first rack teeth 52.
　第２潰し部５５は、第２潰し部５５の内面に平坦部５５ｂが形成された状態で切削される。そのため、第１ラック歯５２と同様に、第２潰し部５５の内面と第２ラック歯５３の歯底５３ａとの間の厚みを必要以上に厚くすることなく第１ラック歯５２の強度を高めることができる。したがって、シャフト本体５１の素材の内径Ｄ１を大きくしてシャフト本体５１を薄くすることができ、ラックシャフト５０を軽量化することができる。 The second crushing part 55 is cut with the flat part 55b formed on the inner surface of the second crushing part 55. Therefore, similarly to the first rack teeth 52, the strength of the first rack teeth 52 is increased without increasing the thickness between the inner surface of the second crushing portion 55 and the tooth bottom 53a of the second rack teeth 53 more than necessary. be able to. Accordingly, the inner diameter D1 of the material of the shaft main body 51 can be increased to make the shaft main body 51 thinner, and the rack shaft 50 can be reduced in weight.
　ラックシャフト５０では、第１及び第２ラック歯５２，５３がそれぞれ第１及び第２潰し部５４，５５に切削加工により形成されるので、第１及び第２ラック歯５２，５３を共通のブローチ盤７０を用いて成形することができる。したがって、ラックシャフト５０の製造コストを削減することができる。 In the rack shaft 50, since the first and second rack teeth 52, 53 are formed by cutting the first and second crushing portions 54, 55, respectively, the first and second rack teeth 52, 53 are connected to a common broach. It can be molded using the board 70. Therefore, the manufacturing cost of the rack shaft 50 can be reduced.
　第１実施形態では、第１及び第２潰し部５４，５５をシャフト本体５１に形成した後に、第１及び第２ラック歯５２，５３が形成される。この順に代えて、第１潰し部５４を形成し第１ラック歯５２を第１潰し部５４に形成した後に、第２潰し部５５を形成して第２ラック歯５３を形成してもよい。 In the first embodiment, after the first and second crushing portions 54 and 55 are formed on the shaft body 51, the first and second rack teeth 52 and 53 are formed. Instead of this order, after forming the first crushing portion 54 and forming the first rack teeth 52 on the first crushing portion 54, the second crushing portion 55 may be formed to form the second rack teeth 53.
　以上の第１実施形態によれば、以下の効果を奏する。 According to the above 1st Embodiment, there exist the following effects.
　ラックシャフト５０では、第１ラック歯５２がシャフト本体５１に形成された後に、第２ラック歯５３が第２潰し部５５に切削加工により形成される。切削加工による第２ラック歯５３の形成では、切削代のコントロールにより切削抵抗を減らすことができるので、塑性変形により第２ラック歯５３を形成する場合と比較して、シャフト本体５１に加えられる力を小さくすることができる。そのため、切削加工時にシャフト本体５１が軸周りに回転するのを防止することができる。したがって、第１ラック歯５２を形成した後に第２ラック歯５３を形成することにより、第１ラック歯５２に対して所望の位相差で第２ラック歯５３を形成することができ、第１ラック歯５２と第２ラック歯５３の位相角精度を向上させることができる。 In the rack shaft 50, after the first rack teeth 52 are formed on the shaft body 51, the second rack teeth 53 are formed on the second crushing portion 55 by cutting. In the formation of the second rack teeth 53 by cutting, the cutting resistance can be reduced by controlling the cutting allowance, so that the force applied to the shaft main body 51 compared to the case where the second rack teeth 53 are formed by plastic deformation. Can be reduced. Therefore, the shaft body 51 can be prevented from rotating around the axis during cutting. Therefore, by forming the second rack teeth 53 after forming the first rack teeth 52, the second rack teeth 53 can be formed with a desired phase difference with respect to the first rack teeth 52. The phase angle accuracy of the teeth 52 and the second rack teeth 53 can be improved.
　また、第２潰し部５５は、シャフト本体５１を径方向に潰すことによって形成される。そのため、第２潰し部５５の内面がシャフト本体５１の径方向内側に変形する。したがって、第２潰し部５５に切削加工により形成される第２ラック歯５３の強度を高めつつシャフト本体５１を薄くすることができ、ラックシャフト５０を軽量化することができる。 Further, the second crushing portion 55 is formed by crushing the shaft body 51 in the radial direction. Therefore, the inner surface of the second crushing portion 55 is deformed inward in the radial direction of the shaft body 51. Therefore, the shaft body 51 can be thinned while increasing the strength of the second rack teeth 53 formed by cutting the second crushing portion 55, and the rack shaft 50 can be reduced in weight.
　また、ラックシャフト５０では、第２潰し部５５が一様の厚みを有する。そのため、第２ラック歯５３の歯幅方向における平坦部５５ｂの両縁間の全体にわたって第２潰し部５５の内面と第２ラック歯５３の歯底５３ａとの間を必要以上に厚くすることなく第２ラック歯５３の強度を高めることができる。したがって、ラックシャフト５０を軽量化することができる。 In the rack shaft 50, the second crushing portion 55 has a uniform thickness. For this reason, the gap between the inner surface of the second crushing portion 55 and the root 53a of the second rack tooth 53 is not made thicker than necessary over the entire width between both edges of the flat portion 55b in the tooth width direction of the second rack tooth 53. The strength of the second rack teeth 53 can be increased. Therefore, the rack shaft 50 can be reduced in weight.
　また、ラックシャフト５０では、第１及び第２ラック歯５２，５３の両方が第１及び第２潰し部５４，５５に切削加工により形成される。そのため、第１及び第２ラック歯５２，５３の両方を共通のブローチ盤７０を用いて形成することができ、ラックシャフト５０の製造コストを低減することができる。 In the rack shaft 50, both the first and second rack teeth 52 and 53 are formed in the first and second crushing portions 54 and 55 by cutting. Therefore, both the first and second rack teeth 52 and 53 can be formed using the common broaching machine 70, and the manufacturing cost of the rack shaft 50 can be reduced.
　＜第２実施形態＞
　次に、本発明の第２実施形態に係るラックシャフト２５０について、図５、図６Ａ及び図６Ｂを参照して説明する。以下では、第１実施形態と異なる点を主に説明し、図中、第１実施形態で説明した構成と同一の構成または相当する構成には同一の符号を付して説明を省略する。また、ラックシャフト２５０を備える電動パワーステアリング装置は、図１に示す電動パワーステアリング装置１００と略同じであるため、ここではその説明及び図示を省略する。 Second Embodiment
Next, a rack shaft 250 according to a second embodiment of the present invention will be described with reference to FIGS. 5, 6A, and 6B. In the following, differences from the first embodiment will be mainly described. In the figure, the same or corresponding components as those described in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Further, since the electric power steering apparatus including the rack shaft 250 is substantially the same as the electric power steering apparatus 100 shown in FIG. 1, the description and illustration thereof are omitted here.
　図５に示すように、ラックシャフト２５０は、中空のシャフト本体５１と、シャフト本体２５１の外周に形成される第１及び第２ラック歯２５２，５３と、を備える。 As shown in FIG. 5, the rack shaft 250 includes a hollow shaft body 51 and first and second rack teeth 252 and 53 formed on the outer periphery of the shaft body 251.
　第１ラック歯２５２は、全長が円筒状に形成されたシャフト本体５１の素材の一部に鍛造加工により形成される。具体的には、図６Ａに示すように、まず、加工前のシャフト本体５１の外面を鍛造加工機８０の上金型８１と下金型８２とにより挟持するとともにシャフト本体５１にマンドレル８４を挿入する。次に、上金型８１の案内孔８１ａに鍛造金型８３を挿入してシャフト本体５１を押し潰す。これにより、シャフト本体５１の一部が塑性変形し、第１ラック歯２５２が形成される。 The first rack teeth 252 are formed by forging on a part of the material of the shaft body 51 whose overall length is formed in a cylindrical shape. Specifically, as shown in FIG. 6A, first, the outer surface of the shaft body 51 before processing is sandwiched between the upper mold 81 and the lower mold 82 of the forging machine 80 and the mandrel 84 is inserted into the shaft body 51. To do. Next, the forging die 83 is inserted into the guide hole 81 a of the upper die 81 to crush the shaft body 51. Thereby, a part of the shaft body 51 is plastically deformed, and the first rack teeth 252 are formed.
　鍛造加工では、第１ラック歯２５２は、鍛造金型８３の形状に応じて形成される。したがって、第１ラック歯２５２を、ＶＧＲ（Ｖａｒｉａｂｌｅ　Ｇｅａｒ　Ｒａｔｉｏ）といった複雑な形状に形成することができる。 In the forging process, the first rack teeth 252 are formed according to the shape of the forging die 83. Therefore, the first rack teeth 252 can be formed in a complicated shape such as VGR (Variable Gear Ratio).
　第２ラック歯５３は、第２潰し部５５に切削加工により形成される。具体的には、第１ラック歯２５２を鍛造加工により形成した後に、シャフト本体５１の外面を加工機６０の上金型６１と下金型６２とにより挟持する。次に、上金型６１の案内孔６１ａに押し型６３を挿入してシャフト本体５１を押し潰す。これにより、第２潰し部５５が形成される。その後、第２潰し部５５の一部を切削して複数の溝を形成する。これにより、第２ラック歯５３が形成される（図５参照）。 The second rack teeth 53 are formed in the second crushing portion 55 by cutting. Specifically, after the first rack teeth 252 are formed by forging, the outer surface of the shaft body 51 is sandwiched between the upper mold 61 and the lower mold 62 of the processing machine 60. Next, the pressing die 63 is inserted into the guide hole 61 a of the upper die 61 to crush the shaft body 51. Thereby, the 2nd crushing part 55 is formed. Thereafter, a part of the second crushing portion 55 is cut to form a plurality of grooves. Thereby, the 2nd rack tooth | gear 53 is formed (refer FIG. 5).
　以上の第２実施形態によれば、以下の効果を奏する。 According to the above second embodiment, the following effects are obtained.
　ラックシャフト２５０では、第１ラック歯２５２が鍛造加工により形成される。そのため、第１ラック歯２５２を、鍛造金型８３の形状に応じて形成することができ、ＶＧＲといった複雑な形状のラック歯を有するラックシャフト２５０を容易に製造することができる。また、第２ラック歯５３が第２潰し部５５に切削加工により形成されるので、予めシャフト本体５１に鍛造加工により形成された複雑な形状の第１ラック歯２５２に対して所望の位相差で第２ラック歯５３を形成しつつ、ラックシャフト２５０を軽量化することができる。 In the rack shaft 250, the first rack teeth 252 are formed by forging. Therefore, the first rack teeth 252 can be formed according to the shape of the forging die 83, and the rack shaft 250 having the rack teeth having a complicated shape such as VGR can be easily manufactured. Further, since the second rack teeth 53 are formed in the second crushing portion 55 by cutting, the second rack teeth 53 have a desired phase difference with respect to the first rack teeth 252 having a complicated shape previously formed on the shaft body 51 by forging. The rack shaft 250 can be reduced in weight while forming the second rack teeth 53.
　＜第３実施形態＞
　次に、本発明の第３実施形態に係るラックシャフト３５０について、図７を参照して説明する。以下では、第１及び第２実施形態と異なる点を主に説明し、図中、第１及び第２実施形態で説明した構成と同一の構成または相当する構成には同一の符号を付して説明を省略する。また、ラックシャフト３５０を備える電動パワーステアリング装置は、図１に示す電動パワーステアリング装置１００と略同じであるため、ここではその説明及び図示を省略する。 <Third Embodiment>
Next, a rack shaft 350 according to a third embodiment of the present invention will be described with reference to FIG. In the following, differences from the first and second embodiments will be mainly described, and in the figure, the same or corresponding configurations as those described in the first and second embodiments are denoted by the same reference numerals. Description is omitted. Further, since the electric power steering apparatus including the rack shaft 350 is substantially the same as the electric power steering apparatus 100 shown in FIG. 1, the description and illustration thereof are omitted here.
　図７に示すように、ラックシャフト３５０のシャフト本体３５１は、所定の厚みｔ１を有する中空の第１シャフト部３５１ａと、厚みｔ２が第１シャフト部３５１ａの厚みｔ１よりも厚い第２シャフト部３５１ｂと、を有する。第１シャフト部３５１ａと第２シャフト部３５１ｂとは互いに接合され、一体化された中空の部材として形成される。第１シャフト部３５１ａと第２シャフト部３５１ｂとは、例えば摩擦圧接により接合される。 As shown in FIG. 7, the shaft main body 351 of the rack shaft 350 includes a hollow first shaft portion 351a having a predetermined thickness t1, and a second shaft portion 351b in which the thickness t2 is thicker than the thickness t1 of the first shaft portion 351a. And having. The first shaft portion 351a and the second shaft portion 351b are joined together and formed as an integrated hollow member. The first shaft portion 351a and the second shaft portion 351b are joined by, for example, friction welding.
　第１シャフト部３５１ａには、第１ラック歯２５２が鍛造加工により形成される。第１シャフト部３５１ａの厚みは薄いので、鍛造加工により第１シャフト部３５１ａを容易に塑性変形させることができる。したがって、第１ラック歯２５２を容易に形成することができる。 The first rack teeth 252 are formed on the first shaft portion 351a by forging. Since the thickness of the first shaft portion 351a is thin, the first shaft portion 351a can be easily plastically deformed by forging. Therefore, the first rack teeth 252 can be easily formed.
　第２シャフト部３５１ｂには、第２潰し部５５が形成され、第２潰し部５５に切削加工により第２ラック歯５３が形成される。第２シャフト部３５１ｂの厚みは厚いので、第２潰し部５５の厚みを厚くすることができ、第２潰し部５５の強度を高めることができる。したがって、切削加工により第２ラック歯５３を形成するときの第２潰し部５５の破損を防止することができる。 The second crushing portion 55 is formed on the second shaft portion 351b, and the second rack teeth 53 are formed on the second crushing portion 55 by cutting. Since the thickness of the 2nd shaft part 351b is thick, the thickness of the 2nd crushing part 55 can be thickened, and the intensity | strength of the 2nd crushing part 55 can be raised. Accordingly, it is possible to prevent the second crushing portion 55 from being damaged when the second rack teeth 53 are formed by cutting.
　このように、ラックシャフト３５０では、厚みの異なる第１及び第２シャフト部３５１ａ，３５１ｂに適した加工方法で第１及び第２ラック歯２５２，５３が形成される。したがって、ラックシャフト３５０の重量の増加を軽減するとともにラックシャフト３５０を容易に製造することができる。 Thus, in the rack shaft 350, the first and second rack teeth 252 and 53 are formed by a processing method suitable for the first and second shaft portions 351a and 351b having different thicknesses. Therefore, an increase in the weight of the rack shaft 350 can be reduced and the rack shaft 350 can be easily manufactured.
　ラックシャフト３５０においても、第１ラック歯２５２を第１シャフト部３５１ａに形成した後に第２ラック歯５３を形成することにより、鍛造加工により形成された複雑な形状の第１ラック歯２５２に対して所望の位相差で第２ラック歯５３を形成しつつ、ラックシャフト２５０を軽量化することができる。 Also in the rack shaft 350, by forming the first rack teeth 252 on the first shaft portion 351a and then forming the second rack teeth 53, the first rack teeth 252 having a complicated shape formed by the forging process can be obtained. The rack shaft 250 can be reduced in weight while forming the second rack teeth 53 with a desired phase difference.
　（変形例）
　以下のような変形例も本発明の範囲内であり、変形例に示す構成と上述の実施形態で説明した構成を組み合わせたり、上述の異なる実施形態で説明した構成どうしを組み合わせたり、以下の異なる変形例で説明する構成どうしを組み合わせることも可能である。 (Modification)
The following modified examples are also within the scope of the present invention, and the configuration shown in the modified example and the configuration described in the above-described embodiment are combined, the configurations described in the above-described different embodiments are combined, or the following different It is also possible to combine the configurations described in the modification.
　第１、第２及び第３実施形態では、シャフト本体５１にマンドレル６４を挿入してシャフト本体５１を径方向に潰すことによって第２潰し部５５が形成されるため、第２潰し部５５の内面には平坦部５５ｂが形成される。本発明はこれに限定されず、マンドレル６４がシャフト本体５１に挿入されていない状態で第２潰し部５５が形成されてもよく、第２潰し部５５の内面には平坦部５５ｂが形成されていなくてもよい。 In the first, second and third embodiments, the second crushing portion 55 is formed by inserting the mandrel 64 into the shaft main body 51 and crushing the shaft main body 51 in the radial direction. Is formed with a flat portion 55b. The present invention is not limited to this, and the second squashed part 55 may be formed in a state where the mandrel 64 is not inserted into the shaft body 51, and the flat part 55 b is formed on the inner surface of the second squashed part 55. It does not have to be.
　例えば、図８Ａに示すように、第２潰し部５５の内面は、シャフト本体５１の径方向内側に向って隆起又は突出していてもよい。また、図８Ｂに示すように、第２潰し部５５の内面は、シャフト本体５１の径方向外側に向って窪んでいてもよい。つまり、第２潰し部５５の内面は、径方向内側に変形し、加工前のシャフト本体５１，３５１の内面の形状と比較して潰れていればよい。第１潰し部５４の内面についても同様に、加工前のシャフト本体５１，３５１の内面の形状と比較して潰れていればよい。 For example, as shown in FIG. 8A, the inner surface of the second crushing portion 55 may protrude or protrude toward the radially inner side of the shaft body 51. Further, as shown in FIG. 8B, the inner surface of the second crushing portion 55 may be recessed toward the radially outer side of the shaft body 51. That is, the inner surface of the second crushed portion 55 only needs to be deformed radially inward and crushed as compared with the shapes of the inner surfaces of the shaft bodies 51 and 351 before processing. Similarly, the inner surface of the first crushed portion 54 may be crushed as compared with the shapes of the inner surfaces of the shaft main bodies 51 and 351 before processing.
　ラックシャフト５０，２５０，３５０では、第２潰し部５５の平坦部５５ａの幅は、シャフト本体５１，３５１の外径よりも小さい。本発明はこれに限定されず、第２潰し部５５の平坦部５５ａの幅が加工前のシャフト本体５１，３５１の外径以上になるように第２潰し部５５を形成してもよい。この場合には、第２ラック歯５３の歯幅を拡大することができる。同様に、第１潰し部５４の平坦部５４ａの幅が加工前のシャフト本体５１の外径以上になるように第１潰し部５４を形成して第１ラック歯５２の歯幅を拡大してもよい。 In the rack shafts 50, 250, and 350, the width of the flat portion 55a of the second crushing portion 55 is smaller than the outer diameter of the shaft bodies 51 and 351. This invention is not limited to this, You may form the 2nd crushing part 55 so that the width | variety of the flat part 55a of the 2nd crushing part 55 may become more than the outer diameter of the shaft main bodies 51 and 351 before a process. In this case, the tooth width of the second rack tooth 53 can be increased. Similarly, the first crushed portion 54 is formed so that the width of the flat portion 54a of the first crushed portion 54 is equal to or larger than the outer diameter of the shaft body 51 before processing, and the tooth width of the first rack teeth 52 is increased. Also good.
　ラックシャフト５０，２５０，３５０では、第２潰し部５５は、加工前のシャフト本体５１，３５１の厚みと略同じ厚みを有する。本発明はこれに限定されず、第２潰し部５５の平坦部５５ａの厚みが加工前のシャフト本体５１，３５１の厚みよりも厚くなるように第２潰し部５５を形成してもよい。この場合には、第２ラック歯５３の歯丈を増加させることができる。同様に、第１潰し部５４の平坦部５４ａの厚みが加工前のシャフト本体５１の厚みよりも厚くなるように第１潰し部５４を形成して第１ラック歯５２の歯丈を増加してもよい。 In the rack shafts 50, 250, and 350, the second crushing portion 55 has substantially the same thickness as that of the shaft bodies 51 and 351 before processing. This invention is not limited to this, You may form the 2nd crushing part 55 so that the thickness of the flat part 55a of the 2nd crushing part 55 may become thicker than the thickness of the shaft main bodies 51 and 351 before a process. In this case, the tooth height of the second rack teeth 53 can be increased. Similarly, the first crushing part 54 is formed so that the thickness of the flat part 54a of the first crushing part 54 is thicker than the thickness of the shaft body 51 before processing, and the tooth height of the first rack teeth 52 is increased. Also good.
　シャフト本体５１，３５１の外面における第１及び第２ラック歯５２，５３，２５２以外の領域に平坦部が形成されていてもよい。このような平坦部にプレッシャパッド（図示省略）を当接させることで、ラックシャフト５０，２５０，３５０の回転を規制することができる。このような平坦部は、シャフト本体５１，３５１の全長に渡って形成されていてもよいし、第１ラック歯５２，２５２か第２ラック歯５３の近傍にのみ形成されていてもよい。 A flat portion may be formed in a region other than the first and second rack teeth 52, 53, 252 on the outer surfaces of the shaft bodies 51, 351. By bringing a pressure pad (not shown) into contact with such a flat portion, the rotation of the rack shafts 50, 250, and 350 can be regulated. Such flat portions may be formed over the entire length of the shaft bodies 51 and 351, or may be formed only in the vicinity of the first rack teeth 52 and 252 or the second rack teeth 53.
　ラックシャフト５０，２５０，３５０では、第１ラック歯５２，２５２と第２ラック歯５３とが同位相に形成されるが、第１ラック歯５２，２５２と第２ラック歯５３は異なる位相に形成されていてもよい。 In the rack shafts 50, 250, and 350, the first rack teeth 52 and 252 and the second rack teeth 53 are formed in the same phase, but the first rack teeth 52 and 252 and the second rack teeth 53 are formed in different phases. May be.
　また、ラックシャフト５０，２５０，３５０では、第１ラック歯５２，２５２が出力シャフト１５の第１ピニオンギア１６に噛み合い第２ラック歯５３がピニオンシャフト２４の第２ピニオンギア２５と噛み合うが、本発明はこの形態に限られない。第１ラック歯５２，２５２がピニオンシャフト２４の第２ピニオンギア２５に噛み合い第２ラック歯５３が出力シャフト１５の第１ピニオンギア１６と噛み合ってもよい。言い換えれば、ステアリングホイール１の回転力が第２ラック歯５３を介してラックシャフト５０，２５０，３５０に伝達され電動モータ２１の回転力が第１ラック歯５２，２５２を介してラックシャフト５０，２５０，３５０に伝達されてもよい。 In the rack shafts 50, 250, and 350, the first rack teeth 52 and 252 mesh with the first pinion gear 16 of the output shaft 15 and the second rack teeth 53 mesh with the second pinion gear 25 of the pinion shaft 24. The invention is not limited to this form. The first rack teeth 52 and 252 may mesh with the second pinion gear 25 of the pinion shaft 24, and the second rack teeth 53 may mesh with the first pinion gear 16 of the output shaft 15. In other words, the rotational force of the steering wheel 1 is transmitted to the rack shafts 50, 250, 350 via the second rack teeth 53, and the rotational force of the electric motor 21 is transmitted to the rack shafts 50, 250 via the first rack teeth 52, 252. , 350 may be transmitted.
　以下、本発明の実施形態の構成、作用、及び効果をまとめて説明する。 Hereinafter, the configuration, operation, and effect of the embodiment of the present invention will be described together.
　本実施形態は、第１及び第２ピニオンギア１６，２５の回転運動を直線運動に変換するラックシャフト５０，２５０，３５０に係る。ラックシャフト５０，２５０，３５０は、中空のシャフト本体５１，３５１と、シャフト本体５１，３５１に設けられ、第１及び第２ピニオンギア１６，２５にそれぞれ噛み合う第１及び第２ラック歯５２，５３，２５２と、を備え、シャフト本体５１，３５１は、径方向に潰すことによって形成され外面に平坦部５４ａ，５５ａを含む第１及び第２潰し部５４，５５を有し、第２ラック歯５３は、第２潰し部５５に切削加工により形成される。 This embodiment relates to rack shafts 50, 250, and 350 that convert the rotational motions of the first and second pinion gears 16 and 25 into linear motions. The rack shafts 50, 250, 350 are provided in the hollow shaft main bodies 51, 351 and the shaft main bodies 51, 351, and the first and second rack teeth 52, 53 that mesh with the first and second pinion gears 16, 25, respectively. , 252, and the shaft main bodies 51, 351 are formed by crushing in the radial direction and have first and second crushing portions 54, 55 including flat portions 54 a, 55 a on the outer surface. Is formed in the second crushing portion 55 by cutting.
　この構成では、第２ラック歯５３が第２潰し部５５に切削加工により形成される。切削加工による第２ラック歯５３の形成では、切削代のコントロールにより切削抵抗を減らすことができるので、塑性変形により第２ラック歯５３を形成する場合と比較して、シャフト本体５１，３５１に加えられる力を小さくすることができる。そのため、切削加工時にシャフト本体５１，３５１が軸周りに回転するのを防止することができる。したがって、第１ラック歯５２，２５２を形成した後に第２ラック歯５３を形成することにより、第１ラック歯５２，２５２に対して所望の位相差で第２ラック歯５３を形成することができる。また、第２潰し部５５は、シャフト本体５１，３５１を径方向に潰すことによって形成される。そのため、第２潰し部５５の内面は径方向内側に変形する。したがって、第２潰し部５５に切削加工により形成される第２ラック歯５３の強度を高めつつシャフト本体５１を薄くすることができる。これにより、第１ラック歯５２と第２ラック歯５３の位相角精度を向上させつつラックシャフト５０，２５０，３５０を軽量化することができる。 In this configuration, the second rack teeth 53 are formed in the second crushing portion 55 by cutting. In the formation of the second rack teeth 53 by cutting, the cutting resistance can be reduced by controlling the cutting allowance, and therefore, in addition to the case where the second rack teeth 53 are formed by plastic deformation, in addition to the shaft main bodies 51 and 351. The force that can be reduced can be reduced. Therefore, it is possible to prevent the shaft bodies 51 and 351 from rotating around the axis during cutting. Therefore, by forming the second rack teeth 53 after forming the first rack teeth 52 and 252, the second rack teeth 53 can be formed with a desired phase difference with respect to the first rack teeth 52 and 252. . The second crushing portion 55 is formed by crushing the shaft main bodies 51 and 351 in the radial direction. Therefore, the inner surface of the second crushing portion 55 is deformed radially inward. Therefore, the shaft main body 51 can be made thin while increasing the strength of the second rack teeth 53 formed by cutting the second crushing portion 55. Accordingly, the rack shafts 50, 250, and 350 can be reduced in weight while improving the phase angle accuracy of the first rack teeth 52 and the second rack teeth 53.
　また、ラックシャフト５０，２５０，３５０では、第１及び第２潰し部５４，５５は、一様の厚みを有する。 In the rack shafts 50, 250, and 350, the first and second crushing parts 54 and 55 have a uniform thickness.
　この構成では、第２潰し部５５が一様の厚みを有する。そのため、第２潰し部５５の平坦部５５ｂの両縁５５ｃ間の全体にわたって第２潰し部５５の内面と第２ラック歯５３の歯底５３ａとの間を必要以上に厚くすることなく第２ラック歯５３の強度を高めることができる。したがって、ラックシャフト５０，２５０，３５０を軽量化することができる。 In this configuration, the second crushing portion 55 has a uniform thickness. Therefore, the second rack without increasing the thickness between the inner surface of the second crushed portion 55 and the bottom 53a of the second rack tooth 53 over the entire length between both edges 55c of the flat portion 55b of the second crushed portion 55. The strength of the teeth 53 can be increased. Therefore, the rack shafts 50, 250, and 350 can be reduced in weight.
　また、ラックシャフト５０では、第１及び第２ラック歯５２，５３が第１及び第２潰し部５４，５５に切削加工により形成される。 Further, in the rack shaft 50, the first and second rack teeth 52, 53 are formed in the first and second crushing portions 54, 55 by cutting.
　この構成では、第１及び第２ラック歯５２，５３が第１及び第２潰し部５４，５５に切削加工により形成される。そのため、第１及び第２ラック歯５２，５３の両方を共通のブローチ盤７０を用いて形成することができ、ラックシャフト５０の製造コストを低減することができる。 In this configuration, the first and second rack teeth 52 and 53 are formed in the first and second crushing portions 54 and 55 by cutting. Therefore, both the first and second rack teeth 52 and 53 can be formed using the common broaching machine 70, and the manufacturing cost of the rack shaft 50 can be reduced.
　また、ラックシャフト２５０，３５０では、第１ラック歯２５２は、鍛造加工によりシャフト本体５１，３５１に形成され、第２ラック歯５３は、第２潰し部５５に切削加工により形成される。 In the rack shafts 250 and 350, the first rack teeth 252 are formed on the shaft bodies 51 and 351 by forging, and the second rack teeth 53 are formed on the second crushing portion 55 by cutting.
　この構成では、第１ラック歯２５２が鍛造加工により形成される。そのため、第１ラック歯２５２を、鍛造金型８３の形状に応じて形成することができ、ＶＧＲ（Ｖａｒｉａｂｌｅ　Ｇｅａｒ　Ｒａｔｉｏ）といった複雑な形状の第１ラック歯２５２を有するラックシャフト２５０，３５０を容易に製造することができる。また、第２ラック歯５３が第２潰し部５５に切削加工により形成されるので、予めシャフト本体３５１に鍛造加工により形成された複雑な形状の第１ラック歯２５２に対して所望の位相差で第２ラック歯５３を形成しつつ、ラックシャフト２５０，３５０を軽量化することができる。 In this configuration, the first rack teeth 252 are formed by forging. Therefore, the first rack teeth 252 can be formed according to the shape of the forging die 83, and the rack shafts 250 and 350 having the first rack teeth 252 having a complicated shape such as VGR (Variable Gear Ratio) can be easily obtained. Can be manufactured. Further, since the second rack teeth 53 are formed in the second crushing portion 55 by cutting, a desired phase difference with respect to the first rack teeth 252 having a complicated shape previously formed on the shaft body 351 by forging. The rack shafts 250 and 350 can be reduced in weight while forming the second rack teeth 53.
　また、ラックシャフト３５０では、シャフト本体３５１は、第１シャフト部３５１ａと、厚みｔ２が第１シャフト部３５１ａの厚みｔ１よりも厚い第２シャフト部３５１ｂと、を有し、第１ラック歯２５２は、第１シャフト部３５１ａに設けられ、第２潰し部５５は、第２シャフト部３５１ｂに設けられる。 In the rack shaft 350, the shaft body 351 has a first shaft portion 351a and a second shaft portion 351b having a thickness t2 larger than the thickness t1 of the first shaft portion 351a, and the first rack teeth 252 are The second crushing portion 55 is provided on the second shaft portion 351b.
　この構成では、第１シャフト部３５１ａの厚みｔ１が薄いので、鍛造加工により第１シャフト部３５１ａを容易に塑性変形させることができ、第１ラック歯２５２を容易に形成することができる。また、第２潰し部５５が厚い厚みｔ２を有する第２シャフト部３５１ｂに設けられる。そのため、第２潰し部５５の強度を高めることができ、切削加工により第２ラック歯５３を形成する際の第２潰し部５５の破損を防止することができる。したがって、ラックシャフト３５０を容易に製造することができる。 In this configuration, since the thickness t1 of the first shaft portion 351a is thin, the first shaft portion 351a can be easily plastically deformed by forging, and the first rack teeth 252 can be easily formed. Moreover, the 2nd crushing part 55 is provided in the 2nd shaft part 351b which has thick thickness t2. Therefore, the strength of the second crushed portion 55 can be increased, and damage to the second crushed portion 55 when the second rack teeth 53 are formed by cutting can be prevented. Therefore, the rack shaft 350 can be easily manufactured.
　また、ラックシャフト５０，２５０，３５０では、シャフト本体５１，３５１は、接合部を含まない１つの中空部材からなる。 Further, in the rack shafts 50, 250, and 350, the shaft main bodies 51 and 351 are formed of one hollow member that does not include a joint portion.
　この構成では、シャフト本体５１，３５１が、接合部を含まない１つの中空部材からなる。接合部を含まない中空部材としては、例えば、シームレス管や電縫管を使用することができる。シームレス管や電縫管は、接合部を含まないので、接合作業を省略することができる。 In this configuration, the shaft main bodies 51 and 351 are formed of one hollow member that does not include a joint portion. As a hollow member that does not include a joint portion, for example, a seamless tube or an electric sewing tube can be used. Since the seamless pipe and the electric resistance welded pipe do not include the joint portion, the joining work can be omitted.
　また、本実施形態は、第１及び第２ピニオンギア１６，２５にそれぞれ噛み合う第１及び第２ラック歯５２，５３，２５２を備えるラックシャフト５０，２５０，３５０の製造方法に係る。ラックシャフト５０，２５０，３５０の製造方法は、中空のシャフト本体５１，３５１に第１ラック歯５２，２５２を形成する第１ラック歯形成工程と、シャフト本体５１，３５１に第２ラック歯５３を形成する第２ラック歯形成工程と、を備え、第２ラック歯形成工程は、シャフト本体５１，３５１を径方向に押し潰して第２潰し部５５を形成することと、第１ラック歯５２，２５２を形成した後に、第２潰し部５５に切削加工により第２ラック歯５３を形成することと、を含む。 Further, the present embodiment relates to a method of manufacturing the rack shafts 50, 250, 350 including the first and second rack teeth 52, 53, 252 that mesh with the first and second pinion gears 16, 25, respectively. The manufacturing method of the rack shafts 50, 250, and 350 includes a first rack tooth forming step of forming the first rack teeth 52 and 252 on the hollow shaft main bodies 51 and 351, and the second rack teeth 53 on the shaft main bodies 51 and 351. A second rack tooth forming step, wherein the second rack tooth forming step includes crushing the shaft bodies 51 and 351 in the radial direction to form the second crushing portion 55, and the first rack teeth 52, Forming the second rack teeth 53 on the second crushing portion 55 by cutting after the 252 is formed.
　この構成では、第１ラック歯５２，２５２が形成された後に、第２ラック歯５３が第２潰し部５５に切削加工により形成される。切削加工による第２ラック歯５３の形成では、第２潰し部５５の一部を除去すればよいので、塑性変形により第２ラック歯５３を形成する場合と比較して、シャフト本体５１，３５１に加えられる力は小さい。そのため、切削加工時にシャフト本体５１，３５１が軸周りに回転するのを防止することができ、第１ラック歯５２，２５２に対して所望の位相差で第２ラック歯５３を形成することができる。また、第２潰し部５５は、シャフト本体５１，３５１を径方向に潰すことによって形成される。そのため、第２潰し部５５の内面は、シャフト本体５１，３５１の径方向内側に変形する。したがって、第２ラック歯５３の強度を高めつつシャフト本体５１，３５１を薄くすることができる。これにより、第１ラック歯５２，２５２と第２ラック歯５３の位相角精度を向上させつつラックシャフト５０，２５０，３５０を軽量化することができる。 In this configuration, after the first rack teeth 52 and 252 are formed, the second rack teeth 53 are formed on the second crushing portion 55 by cutting. In the formation of the second rack teeth 53 by cutting, it is only necessary to remove a part of the second crushing portion 55. Therefore, compared with the case where the second rack teeth 53 are formed by plastic deformation, The applied force is small. Therefore, the shaft main bodies 51 and 351 can be prevented from rotating around the axis during the cutting process, and the second rack teeth 53 can be formed with a desired phase difference with respect to the first rack teeth 52 and 252. . The second crushing portion 55 is formed by crushing the shaft main bodies 51 and 351 in the radial direction. Therefore, the inner surface of the second crushing portion 55 is deformed radially inward of the shaft main bodies 51 and 351. Therefore, the shaft main bodies 51 and 351 can be thinned while increasing the strength of the second rack teeth 53. As a result, the rack shafts 50, 250, 350 can be reduced in weight while improving the phase angle accuracy of the first rack teeth 52, 252 and the second rack teeth 53.
　また、ラックシャフト２５０，３５０の製造方法では、第１ラック歯形成工程は、シャフト本体５１，３５１に鍛造加工により第１ラック歯５２，２５２を形成することを含む。 In the manufacturing method of the rack shafts 250 and 350, the first rack tooth forming step includes forming the first rack teeth 52 and 252 on the shaft bodies 51 and 351 by forging.
　この構成では、第１ラック歯２５２が鍛造加工により形成される。そのため、第１ラック歯２５２を、鍛造金型８３の形状に応じて形成することができ、ＶＧＲ（Ｖａｒｉａｂｌｅ　Ｇｅａｒ　Ｒａｔｉｏ）といった複雑な形状の第１ラック歯２５２を有するラックシャフト２５０，３５０を容易に製造することができる。また、第１ラック歯２５２が鍛造加工により形成された後に第２ラック歯５３が第２潰し部５５に切削加工により形成されるので、複雑な形状の第１ラック歯２５２に対して所望の位相差で第２ラック歯５３を形成しつつ、ラックシャフト２５０，３５０を軽量化することができる。 In this configuration, the first rack teeth 252 are formed by forging. Therefore, the first rack teeth 252 can be formed according to the shape of the forging die 83, and the rack shafts 250 and 350 having the first rack teeth 252 having a complicated shape such as VGR (Variable Gear Ratio) can be easily obtained. Can be manufactured. In addition, since the second rack teeth 53 are formed on the second crushing portion 55 after the first rack teeth 252 are formed by forging, a desired position is obtained with respect to the first rack teeth 252 having a complicated shape. The rack shafts 250 and 350 can be reduced in weight while forming the second rack teeth 53 by the phase difference.
　以上、本発明の実施形態について説明したが、上記実施形態は本発明の適用例の一部を示したに過ぎず、本発明の技術的範囲を上記実施形態の具体的構成に限定する趣旨ではない。 The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.
　本願は２０１７年４月２１日に日本国特許庁に出願された特願２０１７－０８４６４６に基づく優先権を主張し、この出願の全ての内容は参照により本明細書に組み込まれる。 This application claims priority based on Japanese Patent Application No. 2017-084646 filed with the Japan Patent Office on April 21, 2017, the entire contents of which are incorporated herein by reference.

Claims (8)

  1. 　第１及び第２ピニオンギアの回転運動を直線運動に変換するラックシャフトであって、
    　中空のシャフト本体と、
    　前記シャフト本体に設けられ、前記第１及び第２ピニオンギアにそれぞれ噛み合う第１及び第２ラック歯と、を備え、
    　前記シャフト本体は、径方向に潰すことによって形成され外面に平坦部を含む潰し部を有し、
    　前記第１及び第２ラック歯の少なくとも一方は、前記潰し部に切削加工により形成される
    ラックシャフト。     A rack shaft that converts the rotational motion of the first and second pinion gears into linear motion,
    A hollow shaft body;
    First and second rack teeth provided on the shaft body and meshing with the first and second pinion gears, respectively.
    The shaft body has a crushing portion formed by crushing in the radial direction and including a flat portion on the outer surface,
    At least one of the first and second rack teeth is a rack shaft formed by cutting the crushed portion.
  2. 　請求項１に記載のラックシャフトであって、
    　前記潰し部は、一様の厚みを有する
    ラックシャフト。     The rack shaft according to claim 1,
    The crushing part is a rack shaft having a uniform thickness.
  3. 　請求項１に記載のラックシャフトであって、
    　前記第１及び第２ラック歯の両方が前記潰し部に切削加工により形成される
    ラックシャフト。     The rack shaft according to claim 1,
    A rack shaft in which both the first and second rack teeth are formed in the crushed portion by cutting.
  4. 　請求項１に記載のラックシャフトであって、
    　前記第１ラック歯は、鍛造加工により前記シャフト本体に形成され、
    　前記第２ラック歯は、前記潰し部に切削加工により形成される
    ラックシャフト。     The rack shaft according to claim 1,
    The first rack teeth are formed on the shaft body by forging,
    The second rack teeth are rack shafts formed by cutting the crushing portion.
  5. 　請求項４に記載のラックシャフトであって、
    　前記シャフト本体は、第１シャフト部と、厚みが前記第１シャフト部よりも厚い第２シャフト部と、を有し、
    　前記第１ラック歯は、前記第１シャフト部に設けられ、
    　前記潰し部は、前記第２シャフト部に設けられる
    ラックシャフト。     The rack shaft according to claim 4,
    The shaft body includes a first shaft portion and a second shaft portion having a thickness larger than that of the first shaft portion,
    The first rack teeth are provided on the first shaft portion,
    The crushing part is a rack shaft provided on the second shaft part.
  6. 　請求項１に記載のラックシャフトであって、
    　前記シャフト本体は、接合部を含まない１つの中空部材からなる
    ラックシャフト。     The rack shaft according to claim 1,
    The shaft main body is a rack shaft made of one hollow member that does not include a joint.
  7. 　第１及び第２ピニオンギアにそれぞれ噛み合う第１及び第２ラック歯を備えるラックシャフトの製造方法であって、
    　中空のシャフト本体に前記第１ラック歯を形成する第１ラック歯形成工程と、
    　前記シャフト本体に前記第２ラック歯を形成する第２ラック歯形成工程と、を備え、
    　前記第２ラック歯形成工程は、
    　前記シャフト本体を径方向に押し潰すことによって、外面に平坦部を含む潰し部を形成することと、
    　前記第１ラック歯を形成した後に、前記潰し部に切削加工により前記第２ラック歯を形成することと、を含む
    ラックシャフトの製造方法。     A method of manufacturing a rack shaft comprising first and second rack teeth that mesh with first and second pinion gears, respectively,
    A first rack tooth forming step of forming the first rack teeth on a hollow shaft body;
    A second rack tooth forming step of forming the second rack teeth on the shaft body,
    The second rack tooth forming step includes:
    Forming a crushing portion including a flat portion on the outer surface by crushing the shaft body in a radial direction;
    A method of manufacturing a rack shaft, comprising: forming the second rack teeth by cutting the crushed portion after forming the first rack teeth.
  8. 　請求項７に記載のラックシャフトの製造方法であって、
    　前記第１ラック歯形成工程は、前記シャフト本体に鍛造加工により前記第１ラック歯を形成することを含む
    ラックシャフトの製造方法。     It is a manufacturing method of the rack shaft according to claim 7,
    The first rack tooth forming step is a method of manufacturing a rack shaft, including forming the first rack teeth on the shaft body by forging.
PCT/JP2018/015117 2017-04-21 2018-04-10 Rack shaft and method for manufacturing rack shaft WO2018193919A1 (en)

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JP2017-084646 2017-04-21
JP2017084646A JP6748600B2 (en) 2017-04-21 2017-04-21 Rack shaft and method of manufacturing rack shaft

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WO2018193919A1 true WO2018193919A1 (en) 2018-10-25

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JP7369661B2 (en) * 2020-04-24 2023-10-26 株式会社日立インダストリアルプロダクツ How to replace rotor shaft

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JPS603172U (en) * 1983-06-22 1985-01-11 トヨタ自動車株式会社 Rack bar of rack and pinion type steering gear
JPH05345231A (en) * 1992-06-15 1993-12-27 Sumitomo Metal Ind Ltd Manufacture of rack tube
KR100799935B1 (en) * 2006-11-27 2008-01-31 주식회사 코우 Rack forming method of rack bar
JP2014124767A (en) * 2012-12-27 2014-07-07 Neturen Co Ltd Apparatus and method for rack production
JP2014214810A (en) * 2013-04-25 2014-11-17 高周波熱錬株式会社 Double pinion-type rack bar

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Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS603172U (en) * 1983-06-22 1985-01-11 トヨタ自動車株式会社 Rack bar of rack and pinion type steering gear
JPH05345231A (en) * 1992-06-15 1993-12-27 Sumitomo Metal Ind Ltd Manufacture of rack tube
KR100799935B1 (en) * 2006-11-27 2008-01-31 주식회사 코우 Rack forming method of rack bar
JP2014124767A (en) * 2012-12-27 2014-07-07 Neturen Co Ltd Apparatus and method for rack production
JP2014214810A (en) * 2013-04-25 2014-11-17 高周波熱錬株式会社 Double pinion-type rack bar

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