WO2024075695A1 - Unité arbre, son procédé de fabrication et dispositif d'assistance électrique - Google Patents

Unité arbre, son procédé de fabrication et dispositif d'assistance électrique Download PDF

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Publication number
WO2024075695A1
WO2024075695A1 PCT/JP2023/035926 JP2023035926W WO2024075695A1 WO 2024075695 A1 WO2024075695 A1 WO 2024075695A1 JP 2023035926 W JP2023035926 W JP 2023035926W WO 2024075695 A1 WO2024075695 A1 WO 2024075695A1
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WO
WIPO (PCT)
Prior art keywords
shaft
joint member
axial
worm
axial side
Prior art date
Application number
PCT/JP2023/035926
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English (en)
Japanese (ja)
Inventor
亮 大澤
健太郎 海野
友貴 神津
徹 石井
Original Assignee
Ｎｓｋステアリング＆コントロール株式会社
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Application filed by Ｎｓｋステアリング＆コントロール株式会社 filed Critical Ｎｓｋステアリング＆コントロール株式会社
Publication of WO2024075695A1 publication Critical patent/WO2024075695A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D39/00—Application of procedures in order to connect objects or parts, e.g. coating with sheet metal otherwise than by plating; Tube expanders
    • 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
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D1/00—Couplings for rigidly connecting two coaxial shafts or other movable machine elements
    • F16D1/06—Couplings for rigidly connecting two coaxial shafts or other movable machine elements for attachment of a member on a shaft or on a shaft-end
    • F16D1/064—Couplings for rigidly connecting two coaxial shafts or other movable machine elements for attachment of a member on a shaft or on a shaft-end non-disconnectable
    • F16D1/072—Couplings for rigidly connecting two coaxial shafts or other movable machine elements for attachment of a member on a shaft or on a shaft-end non-disconnectable involving plastic deformation
    • 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
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D3/00—Yielding couplings, i.e. with means permitting movement between the connected parts during the drive
    • F16D3/02—Yielding couplings, i.e. with means permitting movement between the connected parts during the drive adapted to specific functions
    • F16D3/04—Yielding couplings, i.e. with means permitting movement between the connected parts during the drive adapted to specific functions specially adapted to allow radial displacement, e.g. Oldham couplings
    • 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
    • F16H1/00—Toothed gearings for conveying rotary motion
    • F16H1/02—Toothed gearings for conveying rotary motion without gears having orbital motion
    • F16H1/04—Toothed gearings for conveying rotary motion without gears having orbital motion involving only two intermeshing members
    • F16H1/12—Toothed gearings for conveying rotary motion without gears having orbital motion involving only two intermeshing members with non-parallel axes
    • F16H1/16—Toothed gearings for conveying rotary motion without gears having orbital motion involving only two intermeshing members with non-parallel axes comprising worm and worm-wheel

Definitions

  • This disclosure relates to an axle unit formed by joining an axle member and a joint member with a crimping portion, a manufacturing method thereof, and an electric assist device including the axle unit.
  • electric power steering devices are widely used, which are configured to provide auxiliary power to steering force transmission members such as the steering shaft, pinion shaft, and rack shaft in order to reduce the force required to operate the steering wheel.
  • Electric power steering devices are equipped with an electric assist device for providing the auxiliary power.
  • An electric assist device comprises an electric motor as a power source, a worm that is rotated by the electric motor, and a worm wheel that meshes with the worm.
  • a structure that includes a coupling for connecting the output shaft of the electric motor and the worm to enable torque transmission while allowing misalignment such as inclination and axial misalignment has also been known for some time (see U.S. Patent No. 1,1084,522).
  • the coupling comprises a joint member that is connected to the output shaft of the electric motor, and a joint member that is connected to one axial end of the worm. These joint members are connected directly or via an intermediate joint member to enable torque transmission while allowing for mutual misalignment.
  • U.S. Patent No. 1,1084,522 describes the specific structure of a shaft unit formed by connecting a shaft member made of a worm to a joint member.
  • the shaft member has a connecting shaft portion at one axial end.
  • the joint member has a central hole that penetrates axially on the radially inward side, and the connecting shaft portion of the shaft member is fitted into this central hole.
  • the shaft member has a center hole that opens to the radial center of the end face on one axial side of the connecting shaft portion.
  • the connecting shaft portion of the shaft member has a cylindrical end on one axial side.
  • the edge of one axial end of the joint shaft is formed with an outward flange-like crimped portion, which is formed by plastically deforming the entire edge radially outward.
  • the crimped portion presses down on the periphery of the opening on one axial end of the central hole of the joint member, thereby joining the shaft member and the joint member.
  • the center hole is a part that is used when machining the outer surface of the shaft member, measuring the bending and rotational runout of the shaft member, and assembling the shaft member with other members, and is specifically engaged with a center shaft for centering and/or rotational support. Therefore, if the center hole is deformed as a result of forming the crimped portion, there is a possibility that the center hole will not be able to be effectively used when performing the measurements and assembly.
  • This problem is not limited to the shaft unit consisting of the worm and joint member that make up the electric assist device, but occurs similarly with shaft units that make up various types of mechanical devices.
  • the purpose of this disclosure is to provide an axle unit that can suppress deformation of the center hole that occurs when forming the crimped portion, a manufacturing method thereof, and an electric assist device that includes the axle unit.
  • the shaft unit of one embodiment of the present disclosure comprises a shaft member having a connecting shaft portion at one axial end and a center hole opening in the radial center of the end face on one axial end of the connecting shaft portion, and a joint member having a central hole penetrating in the axial direction on the radially inner side, into which the connecting shaft portion is fitted.
  • the joint member is a member for connecting the shaft member and a mating shaft member adjacent to the shaft member so as to enable torque transmission.
  • the connecting shaft portion has a crimped portion formed by plastically deforming only the radially outer portion of the edge portion on one axial side protruding from the central hole, and the crimped portion is in surface contact with the opening peripheral portion on one axial side of the central hole of the joint member.
  • At least the radially outer portion of the side surface on one axial side of the crimped portion is configured with an inclined surface portion that is inclined in a direction toward the other axial side as it moves radially outward.
  • the opening periphery of the joint member is configured with a chamfered portion that is inclined radially outward as it approaches one axial side.
  • the shaft member is formed by a worm.
  • An electric assist device includes a worm wheel, a worm meshed with the worm wheel, a coupling including a joint member connected to a connecting shaft portion provided at one axial end of the worm, and an electric motor that transmits torque to the worm via the coupling.
  • the shaft unit including the worm and the joint member is constituted by the shaft unit according to one embodiment of the present disclosure.
  • the axle unit to be manufactured comprises a shaft member having a connecting shaft portion at one axial end and a center hole opening in the radial center of the end face on one axial end of the connecting shaft portion, and a joint member having a center hole penetrating the axial direction on the radially inner side.
  • the manufacturing method of the shaft unit includes a step of pressing the radially outer portion of the edge portion on one axial side of the connecting shaft portion protruding from the central hole toward the other axial side with the pressing surface of a pressing punch while the connecting shaft portion is fitted into the central hole of the joint member, thereby crushing the radially outer portion in the axial direction to form a crimped portion, and bringing the crimped portion into surface contact with the opening peripheral portion on one axial side of the central hole of the joint member.
  • a method for manufacturing a shaft unit includes a step of press-fitting the joint member onto an outer circumferential surface of the coupled shaft portion from one axial side,
  • the inner peripheral surface of the central hole is formed by a serration portion, an outer diameter of the entire connecting shaft portion that protrudes from the central hole of the joint member to one side in the axial direction is equal to or smaller than an inner diameter of the serration portion,
  • the teeth of the serration portion are caused to bite into the outer peripheral surface of the connecting shaft portion, and the press-fitting of the joint member is completed, thereby bringing the connecting shaft portion into the central hole of the joint member.
  • the radially outer portion of the pressing surface presses the side surface on one axial side of the crimped portion toward the other axial side and radially inward.
  • the axle member is formed from a worm.
  • This disclosure provides an axle unit that can suppress deformation of the center hole that occurs when a crimped portion is formed, a manufacturing method thereof, and an electric assist device that includes the axle unit.
  • FIG. 1 is a partial cutaway side view showing an electric power steering device to which an electric assist device according to a first embodiment of the present disclosure is applied.
  • FIG. 2 is a cross-sectional view taken along line AA of FIG. 1, showing the electric power assist device of the first example.
  • FIG. 3 is an enlarged view of a portion B in FIG. 2, showing a connection portion between a worm and an output shaft of an electric motor in the electric assist device of the first example.
  • 4 is an exploded perspective view of a coupling including a worm, a worm-side joint member, an intermediate joint member, and a motor-side joint member in the connection portion of the electric assist device of the first example.
  • the shaft unit of the first example is composed of a shaft member including a worm and the worm-side joint member.
  • FIG. 5 is a perspective view showing one axial end of the shaft unit of the first example.
  • FIG. 6 is a cross-sectional view showing one axial end of the shaft unit of the first example.
  • FIG. 7 is an enlarged view of part C in FIG.
  • FIG. 8 is a diagram showing one axial end of the shaft member before the worm side joint member is press-fitted onto the outer circumferential surface of the connecting shaft portion of the shaft member in the first example.
  • FIG. 9 is a partial cross-sectional view showing a stage immediately before the worm-side joint member is press-fitted onto the outer circumferential surface of the coupled shaft portion in the process of manufacturing the shaft unit of the first example.
  • FIG. 10 is a partial cross-sectional view showing a stage in which the worm side joint member is press-fitted onto the outer circumferential surface of the coupled shaft portion in the process of manufacturing the shaft unit of the first example.
  • FIG. 11 is a cross-sectional view of a pressing punch used in the first example of the shaft unit manufacturing method.
  • FIG. 12 is an enlarged view of a portion D in FIG.
  • FIG. 13 is a partial cross-sectional view showing a stage immediately before the formation of the crimped portion in the process of manufacturing the shaft unit of the first example.
  • FIG. 14 is a partial cross-sectional view showing the start of formation of the crimped portion in the process of manufacturing the shaft unit of the first example.
  • FIG. 15 is an enlarged view of a portion E in FIG.
  • FIG. 16 is a partial cross-sectional view showing the completion stage of formation of the crimped portion in the process of manufacturing the shaft unit of the first example.
  • FIG. 17 is an enlarged view of part F in FIG.
  • FIG. 18 is a half cross-sectional view of one axial side portion of a shaft member (worm) constituting a shaft unit of a second example of an embodiment of the present disclosure.
  • Figure 19(a) is a partial cross-sectional view showing the stage where the worm side joint member is press-fitted onto the outer peripheral surface of the connecting shaft portion of the shaft member in the process of manufacturing the second example shaft unit
  • Figure 19(b) is a partial cross-sectional view showing the stage where the formation of the crimped portion is completed.
  • the present disclosure is applicable to various shaft units that are incorporated into parts of various mechanical devices and are composed of a shaft member and a joint member.
  • shaft members include torque transmission shafts such as worms, sliding screw shafts, ball screw shafts, motor shafts and steering shafts, rack shafts and pinion shafts.
  • the joint member is a member that connects the shaft member to a mating shaft member adjacent to the shaft member to enable torque transmission.
  • joint members include joint members that constitute various joint devices such as couplings, universal joints and constant velocity joints.
  • Shaft unit A first example of a shaft unit 56 is particularly shown in Figures 1 to 7.
  • the shaft unit 56 of this example includes a shaft member 12 having a coupling shaft portion 39 at one axial end and a center hole 43a opening in the radial center of the end face on one axial end of the coupling shaft portion 39, and a joint member 25 having a central hole 30 penetrating in the axial direction on the radially inner side, into which the coupling shaft portion 39 is fitted.
  • the coupling shaft portion 39 has a crimped portion 41 formed by plastically deforming only the radially outer portion of the edge portion on one axial end protruding from the central hole 30, and the crimped portion 41 is in surface contact with an opening peripheral portion 77 on one axial end of the central hole 30 of the joint member 25.
  • one axial side is the right side in Figs. 2 and 3
  • the other axial side is the left side in Figs. 2 and 3.
  • the shaft member 12 is made up of a worm.
  • the joint member 25 is made up of a worm-side joint member that is a part of the coupling 13.
  • the shaft member (worm) 12 of this example is made of metal and has worm teeth 22 on the outer peripheral surface of the axial middle portion.
  • the constituent material and shape of the shaft member 12 are arbitrarily determined according to the type and use of the shaft unit to which this disclosure is applied.
  • the connecting shaft portion 39 provided at the end on one axial side has a smaller outer diameter than the portion adjacent to the other axial side. That is, the shaft member 12 of this example has, in order from one axial side, a mating shaft portion 44 with a larger diameter than the connecting shaft portion 39 and a flange portion 45 protruding radially outward in the portion between the connecting shaft portion 39 and the worm teeth 22.
  • the outer peripheral surface of the connecting shaft portion 39 and the outer peripheral surface of the mating shaft portion 44 are connected by a step surface 40 facing one axial side.
  • the center hole 43a which opens into the radial center of the end face on one axial side of the connecting shaft portion 39, is located at the end on one axial side of the connecting shaft portion 39 and is arranged overlapping the crimped portion 41 in the radial direction.
  • the portion of the end on one axial side of the connecting shaft portion 39 that surrounds the center hole 43a is formed by a cylindrical portion 76.
  • the center hole 43a is a portion that is used when machining the outer peripheral surface of the shaft member 12, measuring bending and rotational runout of the shaft member 12, and assembling the shaft member 12 with other members.
  • a center shaft for centering and/or rotational support engages with the center hole 43a.
  • the shaft member 12 in this example also has a center hole 43b at the other axial end that opens to the radial center of the end face on the other axial end.
  • the portion of the outer circumferential surface of the connecting shaft portion 39 that is fitted into the central hole 30 of the joint member (worm side joint member) 25 is configured as a cylindrical surface.
  • an escape groove 71 is provided around the entire circumference at the end portion on the other axial side that is located on the other axial side of the portion of the outer circumferential surface of the connecting shaft portion 39 that is fitted into the central hole 30 of the joint member 25.
  • the escape groove 71 is a portion for allowing the blade of a cutting tool to escape when making the worm 12.
  • the escape groove 71 can be omitted if not necessary.
  • the joint member 25 in this example is made of metal.
  • the constituent material and shape of the joint member 25 are determined arbitrarily depending on the type and use of the axle unit to which the present disclosure is applied.
  • the central hole 30 of the joint member 25 is provided radially inside the tubular portion 31 that constitutes the radially inner portion of the joint member 25.
  • the inner peripheral surface of the central hole 30 is formed by the serration portion 34.
  • the joint member 25 of this example includes a circular flange portion 32 that protrudes radially outward from an axially intermediate portion of the tubular portion 31, and teeth 33 that protrude toward one axial side from multiple locations (four locations in this example) that are equally spaced circumferentially on the radially outer portion of the flange portion 32.
  • the radial thickness of the tubular portion 31 is greater in the portion located on the other axial side of the flange portion 32 than in the portion located on the one axial side of the flange portion 32.
  • the joint member 25 is formed by subjecting a metal material to necessary processes such as forging and cutting, and then the entire joint member 25 is heat-treated to make it harder than the worm 12.
  • the serration portion 34 is harder than the outer circumferential surface of the connecting shaft portion 39.
  • the joint member 25 is press-fitted from one axial side onto the outer peripheral surface of the connecting shaft portion 39, and the end face on the other axial side of the tubular portion 31 of the joint member 25 abuts against the step surface 40.
  • the teeth of the serration portion 34 (the tooth tips of the tooth portion 33) bite into the outer peripheral surface of the connecting shaft portion 39.
  • a large diameter portion 37 having an inner diameter larger than the inner peripheral surface of the central hole 30 is provided at the opening peripheral portion 78 on the other axial side of the central hole 30 of the joint member 25.
  • the large diameter portion 37 is a portion that forms a space between the outer peripheral surface of the connecting shaft portion 39 and the large diameter portion 37 for storing shavings generated during the press-fitting.
  • the large diameter portion 37 is also configured with a conical surface such as a C-chamfered portion that is inclined radially outward as it approaches the other axial side.
  • the large diameter portion 37 can also be configured with a curved surface such as an R-chamfered portion, or a cylindrical surface with a larger diameter than the inner peripheral surface of the central hole.
  • the opening peripheral portion 77 on one axial side of the central hole 30 of the joint member 25 is configured with a chamfered portion 35 that is inclined radially outward as it approaches one axial side, as shown in Figures 6 and 7. That is, the inner peripheral surface of the central hole 30 and the end face 36 on one axial side of the tubular portion 31 are connected via the chamfered portion 35.
  • the chamfered portion 35 is configured with a linearly inclined C-chamfered portion.
  • the chamfered portion 35 that constitutes the opening peripheral portion 77 of the joint member 25 can also be configured with a curvedly inclined R-chamfered portion, or a chamfered portion whose inclination angle gradually increases as it approaches one axial side.
  • the outer diameter of the chamfered portion 35 i.e., the inner diameter of the end face 36 on one axial side of the tubular portion 31, is larger than the groove bottom diameter of the serration portion 34. Therefore, the end of the groove on one axial side of the serration portion 34 opens only to the chamfered portion 35, and does not open to the end face 36 on one axial side of the tubular portion 31.
  • the engagement relationship between the shaft member 12 and the joint member 25 is determined arbitrarily depending on the type and use of the shaft unit to which the present disclosure is applied.
  • the inner circumferential surface of the central hole of the joint member can be formed of a cylindrical surface
  • the portion of the outer circumferential surface of the connecting shaft portion that is fitted into the central hole of the worm-side joint member can be formed of a serration portion, and the hardness of the worm-side joint member can be made lower than that of the connecting shaft portion.
  • the crimped portion 41 which is formed by plastically deforming only the radially outer portion of the edge portion on one axial side of the connecting shaft portion 39, is in surface contact with the chamfered portion 35 over the entire circumference.
  • the crimped portion 41 protrudes radially outward from the portion of the outer circumferential surface of the connecting shaft portion 39 adjacent to the other axial side of the crimped portion 41.
  • the side surface on the other axial side of the crimped portion 41 is formed of an annular surface that matches the chamfered portion 35 and is inclined toward the one axial side as it moves radially outward, and is in surface contact with the chamfered portion 35 over the entire circumference.
  • the side surface on the other axial side of the crimped portion 41 is in surface contact with the chamfered portion 35 over the entire circumference without any gaps.
  • the opening on one axial side of the groove of the serration portion 34 is entirely blocked by the crimped portion 41.
  • the joint member 25 is fixed to the outside of the connecting shaft portion 39 while being clamped from both axial sides by the stepped surface 40 and the crimping portion 41 of the shaft member 12, and the crimping portion 41 prevents the joint member 25 from falling off from the connecting shaft portion 39 to one side in the axial direction.
  • the crimping portion 41 is in surface contact with the opening periphery 77 (chamfered portion 35) of the joint member 25 over the entire circumference, so compared to the comparative example structure in which the crimping portion only has line contact with the opening periphery (corner) of the central hole over the entire circumference, the crimping portion 41 can firmly hold the joint member 25 from one axial side. Therefore, the crimping portion 41 can effectively prevent the joint member 25 from falling off from the connecting shaft portion 39 to one axial side.
  • the joint member 25 and the shaft member 12 can be effectively prevented from rotating relative to each other by utilizing not only the engagement force acting on the fitting portion between the serration portion 34 of the joint member 25 and the outer circumferential surface of the connecting shaft portion 39 of the shaft member 12, and the frictional force acting on the abutment portion between the other axial end face of the tubular portion 31 of the joint member 25 and the stepped surface 40 of the shaft member 12, but also the large frictional force acting on the surface contact portion between the opening peripheral portion 77 of the joint member 25 and the crimped portion 41 of the shaft member 12.
  • the contact area between the crimped portion 41 and the opening periphery 77 can be made larger than in the structure of the comparative example, in which the crimped portion makes line contact. This ensures a large frictional force acting on the contact portion, effectively preventing relative rotation between the shaft member 12 and the joint member 25.
  • the chamfered portion 35 of the opening periphery 77 of the joint member 25 can be omitted.
  • the opening periphery with which the crimping portion 41 comes into surface contact becomes the radially inner end of the end face on one axial side of the joint member 25.
  • At least the radially outer portion of the side surface on one axial side of the crimped portion 41 is configured with an inclined surface portion 42 that is inclined in a direction toward the other axial side as it moves radially outward.
  • only the radially outer portion of the side surface on one axial side of the crimped portion 41 is configured with an inclined surface portion 42.
  • the entire side surface on one axial side of the crimped portion 41 can also be configured with an inclined surface portion 42.
  • the inclined surface portion 42 is a plastically processed surface formed by pressing a pressing punch 60 (see Figure 17) to form the crimped portion 41.
  • the generatrix shape (cross-sectional shape) of the inclined surface portion 42 is a straight line.
  • the inclination angle ⁇ of the inclined surface portion 42 with respect to a virtual plane perpendicular to the axial direction of the worm 12 can be set arbitrarily in a range greater than 0 degrees, but from the viewpoint of ensuring the crack suppression effect of the crimped portion 41, it is preferable to set the inclination angle ⁇ to 15 degrees or more, and from the viewpoint of suppressing the processing force for forming the crimped portion 41, it is preferable to set the inclination angle ⁇ to 45 degrees or less.
  • the generatrix shape (cross-sectional shape) of the inclined surface portion 42 that constitutes the side surface on one axial side of the crimping portion 41 can also be curved.
  • one axial side of the crimping portion 41 can also be configured as a plane perpendicular to the axial direction of the shaft member 12.
  • the manufacturing method of the shaft unit 56 of the first example is particularly shown in Figures 8 to 17.
  • the manufacturing method of the shaft unit 56 of this example is characterized in that it includes a step of pressing a radially outer portion of an end edge portion on one axial side of the coupling shaft portion 39 protruding from the central hole 30 toward the other axial side with a pressing surface 61 of a pressing punch 60 while the coupling shaft portion 39 is fitted into the central hole 30 of the joint member 25, thereby crushing the radially outer portion in the axial direction to form a crimped portion 41, and bringing the crimped portion 41 into surface contact with an opening peripheral portion 77 on one axial side of the central hole 30 of the joint member 25.
  • optional preparation steps can be provided, including a step of obtaining the intermediate shaft member 12a and the joint member 25, and a step of press-fitting the joint member 25 onto the outer peripheral surface of the connecting shaft portion 39a of the intermediate shaft member 12a from one axial side.
  • an intermediate shaft member 12a is obtained using any material and processing method before the connecting shaft portion 39a is fitted into the central hole 30 of the joint member 25.
  • the intermediate shaft member 12a is obtained by performing necessary processing such as forging and cutting on a metal material.
  • the intermediate shaft member 12a differs from the completed shaft member 12 only in the shape of the outer circumferential surface of the connecting shaft portion 39a. Specifically, the crimped portion 41 is not formed at one axial end of the outer circumferential surface of the connecting shaft portion 39a.
  • the outer circumferential surface of the connecting shaft portion 39a has a cylindrical surface portion 69 in the axial middle portion, a guide surface portion 70 at one axial end adjacent to one axial side of the cylindrical surface portion 69, and an escape groove 71 running around the entire circumference at the other axial end adjacent to the other axial end of the cylindrical surface portion 69.
  • the cylindrical surface portion 69 is configured by a cylindrical surface whose outer diameter does not change in the axial direction.
  • the axial range L69 of the cylindrical surface portion 69 includes the axial range L30 of the portion that is fitted into the central hole 30 of the joint member 25 after the shaft unit 56 is completed ( L69 ⁇ L30 ).
  • the outer diameter of the cylindrical surface portion 69 is larger than the inner diameter of the serration portion 34 of the joint member 25. More specifically, the outer diameter of the cylindrical surface portion 69 is larger than the tip diameter of the serration portion 34 and smaller than the root diameter of the serration portion 34.
  • the guide surface portion 70 is configured with a conical surface whose outer diameter decreases toward one axial side.
  • the guide surface portion 70 is a portion that functions as a guide when starting to press-fit the joint member 25 onto the outer peripheral surface of the connecting shaft portion 39a from one axial side.
  • the guide surface portion 70 can be omitted.
  • the joint member 25 can be obtained by any material and processing method.
  • the joint member 25 is obtained by subjecting a metal material to the necessary processing, such as forging or cutting, and heat treatment.
  • the necessary mechanical properties, such as hardness can be secured, the joint member 25 can also be obtained by sintering metal powder.
  • the joint member 25 is press-fitted onto the outer peripheral surface of the connecting shaft portion 39a of the intermediate shaft member 12a from one axial side.
  • the intermediate shaft member 12a is supported by a support base 57 with one axial end facing upward.
  • the outer peripheral surface of the intermediate shaft member 12a is fitted into a support hole 58 provided in the support base, and the side surface on the other axial side of the flange portion 45 provided on the intermediate shaft member 12a is supported by a support surface 59 of the support base 57, thereby preventing radial displacement and displacement to the other axial side of the intermediate shaft member 12a.
  • the worm teeth 22 of the intermediate shaft member 12a are fitted into the support hole 58 of the support base 57, and the conical convex side of the flange portion 45 of the intermediate shaft member 12a is supported by a conical concave support surface 59 provided on the periphery of the opening on one axial side of the support hole 58 of the support base 57.
  • the joint member 25 is press-fitted from one axial side onto the outer circumferential surface of the connecting shaft portion 39a of the intermediate shaft member 12a.
  • the joint member 25 is press-fitted with the ball bearing 46 and the worm damper 53 on the other axial side positioned around one axial side portion of the intermediate shaft member 12a, which is located above the support base 57, and with the worm damper 53 on one axial side positioned around the end of the tubular portion 31 of the joint member 25 on the other axial side.
  • a cylindrical center shaft 65 is inserted without any radial wobble into a joint member 25 having a worm damper 53 on one axial side arranged around the other axial end of the tubular portion 31, and a press-in jig 72 arranged adjacent to and above the joint member 25, and then a conical engagement portion 73 provided in the radial center of the lower end of the center shaft 65 is engaged with a center hole 43a on one axial side of the intermediate shaft member 12a.
  • the worm damper 53 on one axial side, the joint member 25, and the press-in jig 72 are positioned above the intermediate shaft member 12a, coaxially with the intermediate shaft member 12a.
  • the press-fitting jig 72 presses the end face 36 on one axial side of the tubular portion 31 of the joint member 25, thereby press-fitting the joint member 25 from one axial side onto the outer circumferential surface of the connecting shaft portion 39a, and the end face on the other axial side of the tubular portion 31 of the joint member 25 abuts against the step surface 40 of the intermediate shaft member 12a.
  • the teeth (tooth tips of the tooth portion 33) of the serration portion 34 of the worm side joint member 25 are caused to bite into the cylindrical surface portion 69 provided in the axial middle portion of the outer circumferential surface of the connecting shaft portion 39a.
  • the connecting shaft portion 39 is fitted inside the central hole 30 of the joint member 25, and then a process of forming the crimped portion 41 is carried out using a pressing punch 60 as shown in Figures 11 to 13.
  • the pressing punch 60 is configured as a cylinder as a whole, and has a pressing surface 61 on the radially inner part of the lower end surface in the axial direction.
  • the radially inner portion of the pressing surface 61 is configured with a flat surface portion 62 perpendicular to the axial direction of the pressing punch 60, and the radially outer portion of the pressing surface 61 is configured with an inclined surface portion 63 that inclines downward as it moves radially outward.
  • the radially outer end of the flat surface portion 62 and the radially inner end of the inclined surface portion 63 are smoothly connected.
  • the central hole of the pressing punch 60 has a guide hole portion 64 with a smaller diameter than the axially lower end portion, located from the axially middle portion to the axially upper end portion.
  • the pressing punch 60 is moved downward along the center axis 65a from the state shown in FIG. 13 to the state shown in FIG. 14 and FIG. 15, and the flat surface portion 62 of the pressing surface 61 of the pressing punch 60 is brought into contact with the radially outer portion of the end face on one axial side of the connecting shaft portion 39a.
  • the pressing punch 60 is moved further downward along the center axis 65a from the state shown in Figures 14 and 15 to the state shown in Figures 16 and 17, whereby the flat surface portion 62 of the pressing surface 61 of the pressing punch 60 presses the radially outer portion of the edge portion on one axial side of the connecting shaft portion 39a toward the other axial side. This causes the radially outer portion to be crushed in the axial direction to form the crimped portion 41.
  • the radially outer portion is crushed in the axial direction, and the material of the radially outer portion is caused to flow radially outward along the flat surface portion 62 and the inclined surface portion 63 of the pressing surface 61 of the pressing punch 60, thereby forming the crimped portion 41. Then, the crimped portion 41 is brought into surface contact with the chamfered portion 35 of the joint member 25 over the entire circumference.
  • the inclined surface portion 63 of the pressing surface 61 of the pressing punch 60 presses the radially outer portion of the side surface on one axial side of the crimped portion 41 toward the other axial side and radially inward. This causes a compressive stress to act on the crimped portion 41.
  • the side surface on one axial side of the crimped portion 41 becomes the inclined surface portion 42, which is a plastically processed surface, formed by pressing the inclined surface portion 63 of the pressing surface 61.
  • the center hole 43a can be effectively used when measuring bending and rotational runout of the shaft member 12, and when assembling the shaft member 12 with other members.
  • the radially outer portion of the side surface on one axial side of the crimped portion 41 is pressed toward the other axial side and radially inward, so that compressive stress can be applied to the crimped portion 41, making it less likely that cracks will occur in the crimped portion 41.
  • the side surface on one axial side of the crimped portion 41 can also be pressed toward the other axial side by a flat portion perpendicular to the axial direction.
  • the crimping portion 41 contacts only a number of circumferentially spaced apart locations on the opening peripheral portion 77 (e.g., the chamfered portion 35) on one axial side of the central hole 30 of the joint member 25.
  • the processing load on the crimping portion can be reduced, making manufacturing easier.
  • the press processing of the crimped portion 41 can be performed in multiple steps. In this case, the processing load per step can be reduced, making manufacturing easier.
  • the electric power steering device 1 of this example includes a steering wheel 2, a steering shaft 3, a steering column 4, a pair of universal joints 5a, 5b, an intermediate shaft 6, a steering gear unit 7, and an electric assist device 8 to which the shaft unit 56 of this example is applied.
  • the steering wheel 2 is fixedly supported at the rear end of the steering shaft 3.
  • the steering shaft 3 is rotatably supported inside a steering column 4 supported on the vehicle body.
  • the front end of the steering shaft 3 is connected to the pinion shaft 9 of the steering gear unit 7 via a rear universal joint 5a, an intermediate shaft 6, and a front universal joint 5b.
  • the electric assist device 8 is a device that generates auxiliary power to reduce the force required for the driver to operate the steering wheel 2.
  • the electric assist device 8 of this example includes a worm wheel 11, a worm 12, a coupling 13, and an electric motor 14.
  • the shaft member 12 constituting the shaft unit 56 of this example is used as the worm 12.
  • the electric assist device 8 transmits the rotational torque of the output shaft 23 of the electric motor 14 to the worm 12 via the coupling 13, and then the rotational torque is amplified by a worm reducer that meshes the worm 12 with the worm wheel 11 before being applied to the steering shaft 3.
  • the electric assist device 8 of this example further comprises a housing 15 supported and fixed to the front end of the steering column 4.
  • the housing 15 is a cast product of an iron-based alloy, a die-cast product of a light alloy such as aluminum, or an injection molded product of a synthetic resin, and comprises a wheel housing portion 16 and a worm housing portion 17 that is disposed in a twisted position with respect to the wheel housing portion 16 and has an axially intermediate portion that opens into the wheel housing portion 16.
  • the wheel housing 16 is supported and fixed to the front end of the steering column 4 so that its central axis is coaxial with the central axis of the steering column 4.
  • the worm housing portion 17 is cylindrical and has openings at both axial ends.
  • one axial side of the worm housing portion 17 and the members housed in the worm housing portion 17 is the right side in Figs. 2 and 3, and the other axial side is the left side in Figs. 2 and 3.
  • the opening on one axial side of the worm storage section 17 is blocked by an electric motor 14 supported and fixed to the housing 15.
  • the opening on the other axial side of the worm storage section 17 is blocked by a lid 18.
  • the worm wheel 11 has wheel teeth 19 on its outer circumferential surface, and is rotatably supported inside the wheel housing 16.
  • the worm wheel 11 is supported and fixed around the front end of the steering shaft 3, which is rotatably supported inside the wheel housing 16, so as to rotate integrally with the steering shaft 3.
  • the worm wheel 11 in this example is formed by connecting and fixing a synthetic resin gear portion 21, which has wheel teeth 19 on its outer circumferential surface, to the periphery of a metal, circular disk-shaped core portion 20.
  • the worm 12 is rotatably supported inside the worm housing 17 by a pair of ball bearings 46, 54.
  • One axial end of the worm 12 is connected to the tip of the output shaft 23 of the electric motor 14 via a coupling 13 so as to transmit torque and oscillate.
  • a biasing mechanism 55 including an elastic body such as a coil spring or leaf spring is attached between the outer peripheral surface of the ball bearing 54 supporting the other axial end of the worm 12 and the inner peripheral surface of the worm accommodating portion 17.
  • the biasing mechanism 55 elastically biases the worm teeth 22 of the worm 12 toward the wheel teeth 19 of the worm wheel 11. This configuration suppresses backlash between the worm teeth 22 and the wheel teeth 19, thereby reducing the occurrence of teeth rattle noise.
  • the electric assist device 8 is disposed in a position where it applies auxiliary power to the steering shaft 3.
  • this disclosure can also be applied to an electric assist device that is disposed in a position where it applies auxiliary power to the pinion shaft or rack shaft of a steering gear unit.
  • the coupling 13 includes a worm side joint member 25, a motor side joint member 24 that is fixedly connected to the tip of the output shaft 23 of the electric motor 14, and an intermediate joint member 26 that connects the motor side joint member 24 and the worm side joint member 25 to enable torque transmission while allowing for misalignment between them.
  • the coupling 13 is entirely housed inside the worm accommodating section 17.
  • the joint member 25 of this example is applied to the worm side joint member 25 that constitutes the coupling 13. Therefore, the worm 12 and the worm side joint member 25 constitute the shaft unit 56 of this example.
  • the motor-side joint member 24 is a metal member and includes a cylindrical tube portion 27 that is fitted and fixed to the tip of the output shaft 23 of the electric motor 14, a circular ring-shaped flange portion 28 that protrudes radially outward from the axial middle portion of the tube portion 27, and teeth portions 29 that protrude toward the other axial side from multiple locations (four locations in this example) that are equally spaced circumferentially on the radial outer portion of the flange portion 28.
  • the ends (tips) on the other axial side of these teeth portions 29 are positioned on the other axial side of the tube portion 27.
  • the intermediate joint member 26 is configured in an annular shape as a whole.
  • the intermediate joint member 26 has insertion holes 38a at multiple locations (four locations in this example) on one axial side at equal circumferential intervals into which the teeth 29 of the motor-side joint member 24 can be inserted, and has insertion holes 38b at multiple locations (four locations in this example) on the other axial side at equal circumferential intervals into which the teeth 33 of the worm-side joint member 25 can be inserted.
  • the intermediate joint member 26 is made of a synthetic resin or metal annular core material combined with a rubber cushioning material. The portions of the inner circumferential surfaces of the insertion holes 38a, 38b that come into contact with the teeth 29, 33 when torque is not being transmitted are made of the cushioning material.
  • the multiple teeth 29 of the motor-side joint member 24 are inserted into the multiple insertion holes 38a of the intermediate joint member 26 from one axial side, and the multiple teeth 33 of the worm-side joint member 25 are inserted into the multiple insertion holes 38b of the intermediate joint member 26 from the other axial side. This allows the motor-side joint member 24 and the worm-side joint member 25 to be connected via the intermediate joint member 26 in a manner that allows torque transmission while allowing for mutual misalignment.
  • the tip of the output shaft 23 of the electric motor 14 and one axial end of the worm 12 are connected via a coupling 13 to enable torque transmission, allowing the worm 12 to oscillate relative to the output shaft 23.
  • the structure of the coupling is not limited to the structure of this example.
  • the coupling may be configured to directly connect the motor side joint member and the worm side joint member without using an intermediate joint member, allowing torque transmission while allowing for misalignment between them.
  • the mating shaft portion 44 of the worm 12 is rotatably supported by a ball bearing 46 relative to the worm housing portion 17.
  • the ball bearing 46 comprises an outer ring 47, an inner ring 48, and a number of balls 49.
  • the outer ring 47 is fitted into a cylindrical surface portion 50 provided on the inner peripheral surface of one axial end of the worm accommodating portion 17. In this state, the outer ring 47 is clamped from both axial sides by a step surface 51 facing one axial side that is present in a portion of the worm accommodating portion 17 adjacent to the other axial side of the cylindrical surface portion 50, and a retaining ring 52 engaged with the cylindrical surface portion 50.
  • the inner ring 48 is fitted onto the mating shaft portion 44 of the worm 12 with a clearance fit.
  • An O-ring 67 is engaged in a circumferential groove 66 formed on the outer peripheral surface of the axially middle portion of the mating shaft portion 44, and the O-ring 67 is elastically sandwiched between the bottom surface of the circumferential groove 66 and the inner peripheral surface of the inner ring 48.
  • the worm 12 and the worm side joint member 25 are capable of relative radial displacement with respect to the inner ring 48 by the amount of the minute radial gap.
  • the inner ring 48 is disposed with a small axial gap between the side surface on the other axial side of the tubular portion 31 of the worm side joint member 25 and a step surface 68 facing one axial side provided on the outer peripheral surface of the fitting shaft portion 44.
  • the inner ring 48 is also sandwiched from both axial sides by the side surface on one axial side of the flange portion 45 of the worm 12 and the side surface on the other axial side of the flange portion 32 of the worm side joint member 25 via a pair of worm dampers 53, each of which can be elastically compressed in the axial direction.
  • the side surface on the other axial direction of the inner ring 48 abuts against the side surface on one axial side of the flange 45 via the worm damper 53 on the other axial side
  • the side surface on one axial side of the inner ring 48 abuts against the side surface on the other axial side of the flange 32 via the worm damper 53 on one axial side.
  • the balls 49 are arranged between an outer ring raceway provided on the inner peripheral surface of the outer ring 47 and an inner ring raceway provided on the outer peripheral surface of the inner ring 48.
  • the ball bearing 46 has a radial gap between the outer ring 47 and the inner ring 48 and the balls 49.
  • the mating shaft portion 44 of the worm 12 is supported in the worm accommodating portion 17 in such a way that it can oscillate and move based on the presence of the minute radial gap, the minute axial gap, and the radial gap.
  • an axial meshing reaction force acts on the worm 12 at the meshing portion with the worm wheel 11.
  • the direction of the axial meshing reaction force reverses depending on the rotation direction of the worm 12.
  • the meshing reaction force acting on one axial side of the worm 12 is supported by the retaining ring 52 via the worm damper 53 and ball bearing 46 on the other axial side.
  • the meshing reaction force acting on the worm 12 on the other axial side is supported by the stepped surface 51 of the worm accommodating portion 17 via the worm side joint member 25, the worm damper 53 on one axial side, and the ball bearing 46.
  • the side surface on one axial side of the inner ring 48 comes into contact with the side surface on the other axial side of the tubular portion 31 of the worm side joint member 25, and a large force is applied from the inner ring 48 to the worm side joint member 25 in the one axial direction.
  • the crimped portion 41 provided on the connecting shaft portion 39 of the worm 12 is in surface contact over the entire circumference with the chamfered portion 35 that constitutes the opening peripheral portion on one axial side of the central hole 30 of the worm side joint member 25. Therefore, the crimped portion 41 can effectively prevent the worm side joint member 25 from falling off the connecting shaft portion 39 to one axial side.
  • the inner peripheral surface of the central hole 30 of the joint member 25 is formed by a serration portion 34, and the teeth of the serration portion 34 (tooth tips of the tooth portion 33) bite into the outer peripheral surface of the connecting shaft portion 39 of the shaft member 12 by press-fitting the joint member 25 from one axial side onto the outer peripheral surface of the connecting shaft portion 39.
  • the overall outer diameter of the portion of the connecting shaft portion 39b that protrudes from the radial inside of the joint member 25 to one axial side after the press-fitting of the joint member 25 is completed (the portion shown by the axial range S in FIG. 18 and FIG. 19(a)) is set to be equal to or smaller than the inner diameter of the serration portion 34 provided on the inner peripheral surface of the central hole 30 of the joint member 25.
  • the outer peripheral surface of the connecting shaft portion 39b of the intermediate shaft member 12b has a small diameter portion 74 between the cylindrical surface portion 69 and the guide surface portion 70 in the axial direction, as shown in FIG. 18.
  • the small diameter portion 74 is formed of a cylindrical surface whose outer diameter does not change in the axial direction.
  • the end portion on one axial side of the small diameter portion 74 is directly connected to the end portion on the other axial side of the guide surface portion 70.
  • the end portion on the other axial side of the small diameter portion 74 is connected to the end portion on one axial side of the cylindrical surface portion 69 via a connection portion 75 formed of a conical surface whose outer diameter increases toward the other axial side.
  • the outer diameter of the small diameter portion 74 is equal to or smaller than the inner diameter of the serration portion 34. Therefore, the outer diameter of the guide surface portion 70 is smaller than the inner diameter of the serration portion 34.
  • the outer diameter of the entire portion of the connecting shaft portion 39b that protrudes from the central hole 30 of the joint member 25 onto one axial side after the press-fitting is completed (the portion shown by the axial range S in Figures 18 and 19(a)), i.e., the portion of the small diameter portion 74 excluding the end portion on the other axial side, and the entire guide surface portion 70, is set to be equal to or smaller than the inner diameter of the serration portion 34.
  • the shape of the protruding portion (the portion shown by axial range S in Figures 18 and 19(a)) is a combination of a small diameter portion 74 formed by a cylindrical surface and a guide surface portion 70 formed by a conical surface.
  • the protruding portion can have any shape as long as its overall outer diameter is equal to or smaller than the inner diameter of the serration portion 34.
  • the shape of the protruding portion can be a shape formed entirely by a cylindrical surface, or a shape in which the outer diameter decreases continuously or stepwise toward one axial side.
  • the press-fit is completed and the coupling shaft 39b is fitted inside the central hole 30 of the joint member 25.
  • the radially outer portion of the edge of one axial side of the coupling shaft 39b protruding from the central hole 30 is pressed toward the other axial side by the pressing surface of the pressing punch, thereby crushing the radially outer portion in the axial direction to form a crimped portion 41, and the crimped portion 41 is brought into surface contact with the opening peripheral portion 77 (chamfered portion 35) on one axial side of the central hole 30 of the joint member 25.
  • the overall outer diameter of the protruding portion (the portion shown by the axial range S in Figures 18 and 19(a)) is set to be equal to or smaller than the inner diameter of the serration portion 34. Therefore, compared to a structure in which the outer diameter of at least a portion of the protruding portion is larger than the inner diameter of the serration portion 34 (for example, the structure of the first example), the amount of axial press-in stroke when performing the press-in and external fitting can be kept small. Therefore, the energy required to perform the press-in and external fitting can be reduced accordingly.
  • axial passage marks spin marks
  • axial passage marks of the teeth of the serration portion 34 are formed at multiple circumferential points on the outer peripheral surface of the connecting shaft portion 39b, and even if shavings (burrs) are formed on the edges of the passage marks, the passage marks and shavings are not present in the portion protruding from the center hole 30 of the joint member 25 to one axial side.
  • the opening on one axial side inside the center hole 30, i.e., the opening on one axial side of the groove of the serration portion 34, is blocked by the crimping portion 41. This effectively prevents the shavings from falling off into the surrounding area.
  • axial passage marks of the teeth of the serration portion 34 are formed at multiple points in the circumferential direction on the outer circumferential surface of the protruding portion, and even if chips are formed on the edges of the passage marks, a process for removing the chips can be performed after the crimping portion 41 is formed and before the completed shaft unit 56 is housed in the housing 15 of the worm reducer, thereby preventing the chips from falling off inside the housing 15. In this example, it is possible to omit the process for removing such chips.
  • the other configurations and effects are the same as those of the first example.

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

Abstract

L'invention concerne une unité arbre en mesure de supprimer la déformation d'un trou central due à la formation d'une partie matée, un procédé de fabrication de l'unité arbre et un dispositif d'assistance électrique équipé de l'unité arbre. Une unité arbre 56 a un élément arbre 12 qui a une partie arbre d'accouplement 39 au niveau d'une extrémité dans la direction axiale et a un trou central 43a ouvert au niveau d'une surface d'extrémité de la partie arbre d'accouplement 39 dans la direction axiale, et un élément joint 25, qui a un trou central 30 pénétrant radialement vers l'intérieur dans la direction axiale et dans lequel la partie arbre d'accouplement 39 est ajustée dans le trou central 30, la partie arbre d'accouplement 39 ayant une partie matée 41 qui est formée par déformation plastique uniquement de la partie radialement externe de la partie bord de la partie arbre d'accouplement sur un côté dans la direction axiale, la partie matée 41 étant en contact de surface avec un bord périphérique d'ouverture 77 du trou central 30 de l'élément joint 25 sur un côté dans la direction axiale.
PCT/JP2023/035926 2022-10-05 2023-10-02 Unité arbre, son procédé de fabrication et dispositif d'assistance électrique WO2024075695A1 (fr)

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JP2022161215 2022-10-05
JP2022-161215 2022-10-05
JP2023124154 2023-07-31
JP2023-124154 2023-07-31

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1137168A (ja) * 1997-05-22 1999-02-09 Chubu Tepuro:Kk ボス付きプレート及びボス付きプレートの製造方法
JP2006250294A (ja) * 2005-03-11 2006-09-21 Ntn Corp 転がり軸受
JP2007040420A (ja) * 2005-08-03 2007-02-15 Jtekt Corp 駆動軸の製造方法
JP2007303685A (ja) * 2007-08-27 2007-11-22 Jtekt Corp 軸受装置
JP2011250485A (ja) * 2010-05-21 2011-12-08 Asmo Co Ltd 軸受固定方法、回転子及び減速機構付きモータ

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1137168A (ja) * 1997-05-22 1999-02-09 Chubu Tepuro:Kk ボス付きプレート及びボス付きプレートの製造方法
JP2006250294A (ja) * 2005-03-11 2006-09-21 Ntn Corp 転がり軸受
JP2007040420A (ja) * 2005-08-03 2007-02-15 Jtekt Corp 駆動軸の製造方法
JP2007303685A (ja) * 2007-08-27 2007-11-22 Jtekt Corp 軸受装置
JP2011250485A (ja) * 2010-05-21 2011-12-08 Asmo Co Ltd 軸受固定方法、回転子及び減速機構付きモータ

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