WO2018180281A1 - Arbre à crémaillère et dispositif de direction assistée électrique - Google Patents

Arbre à crémaillère et dispositif de direction assistée électrique Download PDF

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Publication number
WO2018180281A1
WO2018180281A1 PCT/JP2018/008566 JP2018008566W WO2018180281A1 WO 2018180281 A1 WO2018180281 A1 WO 2018180281A1 JP 2018008566 W JP2018008566 W JP 2018008566W WO 2018180281 A1 WO2018180281 A1 WO 2018180281A1
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WO
WIPO (PCT)
Prior art keywords
shaft
rack
axis
outer diameter
pinion
Prior art date
Application number
PCT/JP2018/008566
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English (en)
Japanese (ja)
Inventor
真楽 吉川
前原　秀雄
勝海 下田
Original Assignee
Ｋｙｂ株式会社
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Filing date
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Application filed by Ｋｙｂ株式会社 filed Critical Ｋｙｂ株式会社
Publication of WO2018180281A1 publication Critical patent/WO2018180281A1/fr

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    • 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
    • F16H19/00—Gearings comprising essentially only toothed gears or friction members and not capable of conveying indefinitely-continuing rotary motion
    • F16H19/02—Gearings comprising essentially only toothed gears or friction members and not capable of conveying indefinitely-continuing rotary motion for interconverting rotary or oscillating motion and reciprocating motion
    • F16H19/04—Gearings comprising essentially only toothed gears or friction members and not capable of conveying indefinitely-continuing rotary motion for interconverting rotary or oscillating motion and reciprocating motion comprising a rack

Definitions

  • the present invention relates to a rack shaft and an electric power steering device.
  • JP2015-205581A describes a rack shaft used in a dual pinion type electric power steering apparatus.
  • the rack shaft includes a hollow first shaft on which a first rack for manual steering force transmission is formed, and a solid second shaft on which a second rack for steering assist force transmission is formed. .
  • the first axis and the second axis have the same diameter, so that one of the first axis and the second axis on which a relatively high load acts is used as a reference.
  • the diameter is determined, the diameter of the other shaft to which a relatively low load acts becomes unnecessarily large, and the mass increases accordingly.
  • An object of the present invention is to reduce the weight of a rack shaft and an electric power steering device.
  • a rack shaft that is engaged with a second pinion that is rotated by an electric motor and a first shaft that is formed with a first rack that meshes with a first pinion that rotates as the steering wheel is steered.
  • a second rack is formed, and includes a second shaft coupled to the first shaft, and the outer diameter of the first shaft and the outer diameter of the second shaft are different from each other.
  • FIG. 1 is a configuration diagram of a steering device according to a first embodiment of the present invention.
  • FIG. 2A is a longitudinal cross-sectional view showing a coupling portion of the rack shaft according to the first embodiment of the present invention, and shows a state before the first shaft and the second shaft are coupled.
  • FIG. 2B is a longitudinal cross-sectional view showing a coupling portion of the rack shaft according to the first embodiment of the present invention, and shows a state where the first shaft and the second shaft are coupled.
  • FIG. 3A is a cross-sectional view of the rack shaft along the line III-III in FIG. 1, and shows the dimensions of each part of the rack shaft.
  • 3B is a cross-sectional view of the rack shaft along the line III-III in FIG.
  • FIG. 4A is a longitudinal sectional view showing a coupling portion of a rack shaft according to the second embodiment of the present invention.
  • FIG. 4B is a longitudinal cross-sectional view showing a coupling portion of rack shafts according to a modification of the second embodiment of the present invention.
  • FIG. 5A is a plan view showing a rack shaft according to a third embodiment of the present invention.
  • FIG. 5B is a plan view showing a rack shaft according to a modification of the third embodiment of the present invention.
  • FIG. 6A is a longitudinal sectional view showing a rack shaft according to a fourth embodiment of the present invention.
  • FIG. 6B is a longitudinal sectional view showing a rack shaft according to the second modification of the fourth embodiment of the present invention.
  • FIG. 6C is a longitudinal sectional view showing a rack shaft according to a third modification of the fourth embodiment of the present invention.
  • FIG. 7 is a cross-sectional view showing a rack shaft according to a fifth embodiment of the present invention.
  • FIG. 8 is a side view showing a rack shaft support structure according to a fifth embodiment of the present invention.
  • FIG. 9 is a cross-sectional view showing a rack shaft according to the first modification of the embodiment of the present invention.
  • FIG. 10 is a cross-sectional view showing a rack shaft according to the second modification of the embodiment of the present invention.
  • FIG. 1 is a configuration diagram of a steering device 100 according to the first embodiment of the present invention.
  • the steering device 100 is a dual pinion type electric power steering device in which a steering force by a driver and an assist driving force by the electric motor 21 are independently input to the rack shaft 12A.
  • the steering device 100 includes a steering mechanism 10 that steers the vehicle wheel 2 in response to rotation of the steering wheel 1 to which a steering force is input by the driver, an assist mechanism 20 that assists the driver's steering force, and steering. And a control device 30 for controlling the force assist amount.
  • 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 12 ⁇ / b> A that steers the vehicle wheel 2 according to the rotation of the steering shaft 11. .
  • the steering shaft 11 includes an input shaft 13 connected to the steering wheel 1, an output shaft 15 connected to the input shaft 13 via a torsion bar 14, and a first pinion 16 formed on the output shaft 15 and meshing with the rack shaft 12A. And having.
  • the assist mechanism 20 includes an electric motor 21 that is a power source of assist force, a pinion shaft 22 as a rotating shaft to which the driving force of the electric motor 21 is transmitted via the speed reduction mechanism 3, and a rack shaft formed on the pinion shaft 22. And a second pinion 23 that meshes with 12A.
  • the speed reduction mechanism 3 includes a worm shaft 3 a connected to the output shaft of the electric motor 21, and a worm wheel 3 b that meshes with the worm shaft 3 a and is connected to the pinion shaft 22.
  • 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 22.
  • the steering angle sensor 34 that detects the steering angle that is the rotation 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 22 detected by the rotation angle sensor 32.
  • the detection result of the rotation angle sensor 32 is used also in control of VDC (Vehicle Dynamics Control) etc. which suppress the side slip etc. of a vehicle.
  • VDC Vehicle Dynamics Control
  • the rack shaft 12A is a round bar-like member that extends linearly along the left-right direction of the vehicle, and is formed by coupling the first shaft 110 and the second shaft 120 together.
  • shaft 120 are each formed from the same material (for example, carbon steel).
  • the rack shaft 12A is formed such that the axial length of the first shaft 110 and the axial length of the second shaft 120 are the same.
  • the rack shaft 12A is housed in a housing (not shown) fastened to the vehicle body. Both end portions of the rack shaft 12 ⁇ / b> A pass through an end portion in the axial direction of a housing (not shown) and are connected to the tie rod 25. That is, both end portions of the rack shaft 12 ⁇ / b> A are connected to the left and right wheels 2 via the tie rods 25.
  • the first shaft 110 is formed with a first rack 115 that meshes with the first pinion 16 that rotates as the steering wheel 1 is steered.
  • the rotational force from 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 transmitted to the first rack 115 via the first pinion 16.
  • the rotational force of the first pinion 16 is converted into a force in the axial direction of the rack shaft 12A (the left-right direction of the vehicle). Therefore, when the steering wheel 1 is steered, the driver's steering force is transmitted to the rack shaft 12A via the first rack 115, and the vehicle wheel 2 is steered in accordance with the movement of the rack shaft 12A.
  • a second rack 125 that meshes with a second pinion 23 that is rotated by the electric motor 21 is formed on the second shaft 120.
  • the rotational force from the electric motor 21 is transmitted to the pinion shaft 22 via the speed reduction mechanism 3.
  • the rotational force of the pinion shaft 22 is transmitted to the second rack 125 via the second pinion 23.
  • the rotational force of the second pinion 23 is converted into a force in the axial direction of the rack shaft 12A (the left-right direction of the vehicle). Therefore, when the electric motor 21 is driven to rotate, the rotational force of the electric motor 21 is transmitted to the rack shaft 12A via the second rack 125, and the vehicle wheel 2 is steered in accordance with the movement of the rack shaft 12A.
  • the rack shaft 12A is formed by joining two members of a first shaft 110 that is a solid columnar member and a second shaft 120 that is a solid columnar member.
  • Various methods such as friction welding, welding, and screw fitting can be employed as the coupling method, but it is preferable to employ friction welding with relatively high joint strength.
  • the rack shaft 12A is reduced in weight by making the outer diameter of the first shaft 110 and the outer diameter of the second shaft 120 different.
  • FIG. 2A and FIG. 2B are longitudinal sectional views showing a coupling portion of the rack shaft 12A according to the first embodiment of the present invention.
  • 2A shows a state before the first shaft 110 and the second shaft 120 are coupled
  • FIG. 2B shows a state where the first shaft 110 and the second shaft 120 are coupled.
  • the axial end of the first shaft 110 and the axial end of the second shaft 120 are coupled by friction welding.
  • the first shaft 110 includes a main body portion 111 and a cylindrical connecting tube portion 112 provided at an end portion of the main body portion 111 in the axial direction.
  • the connecting tube portion 112 is a portion in which the outer peripheral portion at the axial end of the main body portion 111 extends in the axial direction, and the outer diameter of the connecting tube portion 112 is the same as the outer diameter of the main body portion 111.
  • the center of the connecting cylinder part 112 is concentric with the center of the main body part 111.
  • the second shaft 120 includes a main body 121 and a cylindrical connecting cylinder 122 provided at an axial end of the main body 121.
  • the connecting cylinder portion 122 protrudes in the axial direction from the axial end portion of the main body portion 121.
  • the center of the connecting cylinder part 122 is concentric with the center of the main body part 121.
  • the outer diameter D1 of the main body 111 of the first shaft 110 is smaller than the outer diameter D2 of the main body 121 of the second shaft 120 (D1 ⁇ D2).
  • the connecting tube portion 122 of the second shaft 120 is formed so that the outer diameter D3 thereof is the same as the outer diameter D1 of the connecting tube portion 112 of the first shaft 110.
  • the connection cylinder part 112 and the connection cylinder part 122 are formed so that each thickness may become the same.
  • the manufacturing method of the rack shaft 12A includes a friction welding process, a first rack forming process, and a second rack forming process.
  • the friction welding process as shown in FIG. 2A, the first shaft 110 and the first shaft 110 are arranged so that the end surface 112a of the connecting tube portion 112 of the first shaft 110 and the end surface 122a of the connecting tube portion 122 of the second shaft 120 face each other.
  • Two axes 120 are arranged coaxially.
  • the first shaft 110 and the second shaft 120 are pressurized in the axial direction in a state where the end surface 112a and the end surface 122a are in contact with each other.
  • first shaft 110 and the second shaft 120 are pressurized, the first shaft 110 and the second shaft 120 are relatively rotated in the circumferential direction to generate frictional heat on the contact surface.
  • mutual diffusion between the first shaft 110 and the second shaft 120 is promoted, The second shaft 120 is joined.
  • the first rack 110 is formed on the first shaft 110 by performing a cutting process in which a part of the outer peripheral surface in the axial direction and the circumferential direction of the first shaft 110 is scraped by a broaching machine or the like.
  • the second rack 125 is formed on the second shaft 120 by performing a cutting process in which a part of the outer peripheral surface in the axial direction and the circumferential direction of the second shaft 120 is scraped with a broaching machine or the like.
  • the first rack 115 has a CGR (Constant Gear Ratio) specification in which the rack teeth have a uniform pitch
  • the second rack 125 has a VGR (Variable Gear) Ratio) specification in which the rack teeth have a variable pitch.
  • the module, the twist angle, and the number of teeth are set so that the stroke amount, the stroke ratio, the axis crossing angle (intersection angle between the output shaft 15 and the rack shaft 12A), the strength requirements, and the like are satisfied.
  • the module, the torsion angle, the outer diameter, and the phase angle are set so that the assist thrust by the electric motor 21, the durability, the mounting property on the vehicle, the requirements for the steering follow-up characteristic, and the like are satisfied.
  • the first rack forming step and the second rack forming step may be performed before the friction welding step or after the friction welding step.
  • the friction welding process is performed, and the other rack is formed so as to correspond to the circumferential position of the already formed rack.
  • a rack forming step may be performed. In this case, the positioning accuracy in the circumferential direction between the first rack 115 and the second rack 125 is not affected by the friction welding, which is preferable.
  • the rack teeth of the first rack 115 and the second rack 125 are formed so that the reference pitch line P1 of the first rack 115 and the reference pitch line P2 of the second rack 125 are parallel to each other ( (See FIG. 3A).
  • the reference pitch line P1 of the first rack 115 and the reference pitch line P2 of the second rack 125 are not limited to being parallel to each other, and may be inclined with respect to each other.
  • FIG. 3A and 3B are cross-sectional views of the rack shaft along the line III-III in FIG. 3A shows the dimensions of each part of the rack shaft 12A, and FIG. 3B shows the positional relationship between the rack shaft 12A, the output shaft 15, and the pinion shaft 22.
  • FIG. 3B only the center axes CL1 and CL2 of the output shaft 15 and the pinion shaft 22 are shown, and the first pinion 16 and the second pinion 23 are not shown.
  • the portion of the main body 111 of the first shaft 110 where the first rack 115 is formed is referred to as a first rack forming portion 116
  • the second rack 125 is formed of the main body 121 of the second shaft 120.
  • the portion in which is formed is referred to as a second rack forming portion 126.
  • the axial lengths of the first rack forming portion 116 and the second rack forming portion 126 correspond to a length that allows the rack shaft 12A to be slid in order to steer the wheel 2 left and right to the maximum turning angle.
  • the shape of the cross section of the first rack forming portion 116 of the first shaft 110 is indicated by a solid line
  • the shape of the cross section of the second rack forming portion 126 of the second shaft 120 is indicated by a two-dot chain line. ing.
  • each part of the first shaft 110 and the dimensions of each part of the second shaft 120 are compared.
  • an axis that is orthogonal to the reference pitch line P1 of the first rack 115 and the center axis O of the rack shaft 12A and that passes through the center axis O of the rack shaft 12A will be described as a Z axis.
  • each part of the first rack forming part 116 are smaller than the dimensions of each part of the second rack forming part 126 corresponding to each part of the first rack forming part 116. This will be described in detail below.
  • the tooth width W1 of the first rack 115 is smaller than the tooth width W2 of the second rack 125 (W1 ⁇ W2).
  • the tooth width W1 of the first rack 115 is smaller than the outer diameter D1 of the first rack forming portion 116
  • the tooth width W2 of the second rack 125 is smaller than the outer diameter D2 of the second rack forming portion 126 (W1 ⁇ D1, W2 ⁇ D2).
  • the wall thickness T1 of the first rack forming section 116 is smaller than the wall thickness T2 of the second rack forming section 126 (T1 ⁇ T2).
  • the wall thickness T1 is the Z-axis dimension from the tooth tip of the first rack 115 on the Z-axis to the back surface of the first rack forming portion 116
  • the wall thickness T2 is from the tooth tip of the second rack 125 on the Z-axis. This is the Z-axis dimension up to the back surface of the second rack forming portion 126.
  • the Z-axis dimension Z1 from the center axis O of the rack shaft 12A to the reference pitch line P1 of the first rack 115 is smaller than the Z-axis dimension Z2 from the center axis O to the reference pitch line P2 of the second rack 125 (Z1 ⁇ Z2).
  • the center axis CL1 of the output shaft 15 can be brought closer to the center axis O of the rack shaft 12A than the center axis CL2 of the pinion shaft 22.
  • the pinion shaft 22 and the output so that the inter-axis distance ZL1 between the rack shaft 12A and the output shaft 15 is smaller than the inter-axis distance ZL2 between the rack shaft 12A and the pinion shaft 22.
  • the inter-axis distance ZL1 is the Z-axis dimension from the central axis O of the rack shaft 12A to the central axis CL1 of the output shaft 15, and the inter-axis distance ZL2 is the central axis CL2 of the pinion shaft 22 from the central axis O of the rack shaft 12A. Z-axis dimensions up to.
  • the rack shaft 12A includes a first shaft 110 on which a first rack 115 to which a steering force is transmitted and a second rack 125 to which a driving force of the electric motor 21 is transmitted. And a second shaft 120 coupled to the second shaft 120.
  • the outer diameter D1 of the first shaft 110 and the outer diameter D2 of the second shaft 120 are different diameters. Since the diameter of one of the first shaft 110 and the second shaft 120 is smaller than the diameter of the other shaft, the mass of one shaft is smaller than that of the other shaft. Can be reduced. Therefore, the rack shaft 12A and the steering device 100 can be reduced in weight.
  • the materials of the first shaft 110 and the second shaft 120 are the same.
  • Each of the first shaft 110 and the second shaft 120 is a solid columnar member.
  • the load acting on the first shaft 110 to which the steering force is transmitted is smaller than that of the second shaft 120 to which the driving force of the electric motor 21 is transmitted.
  • the outer diameter D1 of the first rack forming portion 116 of the first shaft 110 is smaller than the outer diameter D2 of the second rack forming portion 126 of the second shaft 120 (D1 ⁇ D2). .
  • shaft 110 can be made smaller than the mass of the 2nd axis
  • the rack shaft 12 ⁇ / b> A having excellent durability against a high load from the electric motor 21 can be obtained.
  • the rack shaft 12A can be reduced in weight while satisfying the strength required for each of the first shaft 110 and the second shaft 120.
  • the Z-axis dimension Z1 from the center axis O of the rack shaft 12A to the reference pitch line P1 is smaller than the Z-axis dimension Z2 from the center axis O to the reference pitch line P2. Therefore, as shown in FIG. 3B, the center axis CL1 of the output shaft 15 can be brought closer to the center axis O of the rack shaft 12A than the center axis CL2 of the pinion shaft 22 (ZL1 ⁇ ZL2).
  • the output shaft 15 is brought close to the rack shaft 12A so that the distance between the output shaft 15 and the rack shaft 12A is shortened, and this portion is made compact.
  • the degree of freedom of attachment of the steering device 100 to the vehicle can be improved, that is, the mountability can be improved.
  • the outer diameters of the first shaft 110 and the second shaft 120 can be set individually. For this reason, for example, by making the outer diameter D2 of the second shaft 120 larger than the outer diameter D1 of the first shaft 110, the contact area of the rack teeth of the second shaft 120 with the second pinion 23 can be increased. Thereby, the freedom degree of the axis crossing angle which is the crossing angle of the pinion shaft 22 and the rack shaft 12A can be improved. As a result, the degree of freedom of mounting the steering device 100 on the vehicle can be improved, that is, the mountability can be improved.
  • connection cylinder part 112,122 was formed so that the outer diameter D1 of the connection cylinder part 112 and the outer diameter D3 of the connection cylinder part 122 may become the same (FIG. 2A
  • the present invention is not limited to this.
  • Either one of the connecting tube portions 112 and 122 may be formed larger.
  • the outer diameter D3 of the connecting cylinder part 122 may be formed larger than the outer diameter D1 of the connecting cylinder part 112 (D3> D1). What is necessary is just to form the connection cylinder parts 112 and 122 so that the contact area of the grade which can obtain sufficient joint strength at least can be obtained.
  • the example in which the size of each part of the first rack forming unit 116 is smaller than the size of each part of the second rack forming unit 126 corresponding to each part of the first rack forming unit 116 has been described.
  • the invention is not limited to this.
  • the Z-axis dimension Z1 from the central axis O of the rack shaft 12A to the reference pitch lines P1, P2 , Z2 may be such that Z1> Z2.
  • the magnitude relationship between the thicknesses T1 and T2 may satisfy T1> T2.
  • FIG. 4A is a longitudinal sectional view showing a coupling portion of the rack shaft 12B1.
  • each of the first shaft 110 and the second shaft 120 is a solid columnar member.
  • the first shaft 210 is a hollow cylindrical member. This is different from the first embodiment. This will be specifically described below.
  • the first shaft 210 is a cylindrical member.
  • the connecting tube portion 122 of the second shaft 120 is formed so that the thickness of the connecting tube portion 122 is the same as the thickness of the first shaft 210.
  • An axial end portion of the first shaft 210 is joined to the connecting tube portion 122 of the second shaft 120 by friction welding.
  • the first rack forming process before the friction welding process.
  • a cylindrical mandrel is reciprocated in the hollow portion of the first shaft 210 while the first shaft 210 is held by a rack forming mold. Thereby, the first shaft 210 is gradually plastically deformed.
  • the first rack 115 can be formed on the first rack forming portion 116 of the first shaft 210 by reciprocating the mandrel having a large diameter little by little in the axial direction.
  • the outer diameter D1 of the first shaft 210 in the first rack forming portion 116 is smaller than the outer diameter D2 of the second shaft 120 in the second rack forming portion 126 (D1 ⁇ D2).
  • the rack shaft 12B1 and the steering device 100 can be further reduced in weight compared to the first embodiment.
  • FIG. 4B is a longitudinal sectional view showing a coupling portion of the rack shaft 12B2 according to a modification of the second embodiment of the present invention.
  • a connecting tube portion 222 having an outer diameter D2 is formed at the axial end portion of the second shaft 220, and the outer diameter D2 is applied to the axial end portion of the first shaft 210.
  • the connecting tube portion 212 may be formed.
  • the outer diameter D1 of the first rack forming portion 116 can be made smaller than the outer diameter D2 of the second rack forming portion 126, so that the rack shaft 12B2 and the steering device 100 can be reduced in weight.
  • the outer diameters of the connecting tube portions 212 and 222 are larger than those in the above embodiment, so that the relative rotational speed of the first shaft 210 and the second shaft 220 is kept low in the friction welding process. Also, the peripheral speed necessary for friction welding can be obtained.
  • FIG. 5A is a plan view showing a rack shaft 12C1 according to a third embodiment of the present invention.
  • the first shaft 310A and the second shaft 320A are solid cylindrical members formed from the same material. For this reason, the mass per unit length in the first rack forming portion 116 of the small-diameter first shaft 310A is smaller than the mass per unit length in the second rack forming portion 126 of the large-diameter second shaft 320A.
  • the length of the first shaft 310A having a small mass per unit length is made longer than the length of the second shaft 320A having a large mass per unit length, thereby realizing weight reduction.
  • the shaft length of the first shaft 110 is the same as the shaft length of the second shaft 120, but in the third embodiment, the shaft length L1 of the first shaft 310A is the second shaft 320A. This is different from the first embodiment in that it is longer than the axial length L2.
  • the total length of the rack shaft 12C1 is the same as the total length of the rack shaft 12A of the first embodiment.
  • one axis having a small mass per unit length is formed longer than the other axis having a large mass per unit length.
  • the rack shaft 12C1 and the steering device 100 can further be reduced in weight.
  • FIG. 5B is a plan view showing a rack shaft 12C2 according to a modification of the third embodiment of the present invention.
  • the first shaft 310B is a hollow cylindrical member, and the outer diameter of the first shaft 310B is larger than the outer diameter of the second shaft 320B.
  • the first shaft 310B is a hollow cylindrical member, and the first rack 115 is formed by forging.
  • the second shaft 320B is a solid cylindrical member, and the second rack 125 is formed by cutting. Since the rack teeth can be formed more accurately in the cutting process than in the forging process, the meshing accuracy between the second rack 125 and the second pinion 23 is higher than the meshing accuracy between the first rack 115 and the first pinion 16. Is also expensive.
  • the durability of the second rack 125 can be ensured by increasing the meshing accuracy between the rack teeth of the second shaft 320B on which a relatively high load acts and the pinion.
  • the mass per unit length in the first rack forming portion 116 is smaller than the mass per unit length in the second rack forming portion 126. For this reason, by forming the axial length L1 of the first shaft 310B longer than the axial length L2 of the second shaft 320B, the rack shaft 12C2 and the steering device 100 can be reduced in weight compared to the case where the axial length is the same. .
  • a rack shaft 12D1 according to a fourth embodiment of the present invention will be described with reference to FIG. 6A.
  • the following description will focus on differences from the first embodiment, and in the figure, the same or corresponding components as those described in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted. .
  • FIG. 6A is a longitudinal sectional view showing a rack shaft 12D1 according to a fourth embodiment of the present invention.
  • the end surface 112a of the first shaft 110 and the end surface 122a of the second shaft 120 are joined by friction welding (see FIGS. 2A and 2B).
  • the second shaft 420A is a cylindrical member, and the first shaft 410A is press-fitted into the hollow portion of the second shaft 420A and welded, whereby the first shaft 410A and the second shaft 420A are welded.
  • the shaft 420A is coupled.
  • FIG. 6B is a longitudinal sectional view showing a rack shaft 12D2 according to the second modification of the fourth embodiment of the present invention.
  • a fastening member 490 such as a bolt or nut.
  • the first shaft 410B and the second shaft 420B are coupled.
  • FIG. 6C is a longitudinal sectional view showing a rack shaft 12D3 according to Modification 3 of the fourth embodiment of the present invention.
  • the first shaft 410C and the second shaft 420C are sandwiched between the socket 493 of the ball joint 491 and the step 418 provided on the first shaft 410C.
  • the second shaft 420C is coupled.
  • the first shaft 410 ⁇ / b> C is provided with a columnar fitting portion 417 that protrudes in the axial direction from the axial end portion of the main body portion 111.
  • the fitting portion 417 is a portion that is fitted into the hollow portion of the second shaft 420 ⁇ / b> C and has an outer diameter smaller than that of the main body portion 111. Since the fitting portion 417 is formed to have a smaller diameter than the main body portion 111, the axial end surface of the main body portion 111 facing the axial end surface of the second shaft 420 ⁇ / b> C is a stepped portion 418.
  • a ball joint 491 which is a universal joint connected to the end of the rack shaft 12D3 is provided at the end of the tie rod 25.
  • the ball joint 491 includes a socket 493 fixed to the end portion of the first shaft 410C and a ball 492 fixed to the end portion of the shaft portion of the tie rod 25.
  • the socket 493 includes a ball accommodating portion 493a that accommodates the ball 492, and a bolt 493b that is integrally provided on the proximal end side of the ball accommodating portion 493a.
  • the male screw provided on the bolt 493b is screwed into the female screw provided in the hole 449 extending in the axial direction from the distal end surface of the fitting portion 417 of the first shaft 410C, whereby the socket 493 is engaged with the first shaft 410C. It is fixed to.
  • FIG. 6C illustrates an example in which an annular member 499 is interposed between the socket 493 and the rack shaft 12D3, the annular member 499 may be omitted.
  • the outer peripheral portion of the fitting portion 417 of the first shaft 410C and the inner peripheral portion of the second shaft 420C are respectively keyed. It is preferable that a groove is provided and a key is fitted into the key groove to prevent the first shaft 410C and the second shaft 420C from rotating.
  • FIG. 7 is a cross-sectional view showing a rack shaft 12E according to a fifth embodiment of the present invention
  • FIG. 8 is a side view showing a support structure for the rack shaft 12E according to the fifth embodiment of the present invention.
  • the pinion and the rack guide are indicated by a two-dot chain line.
  • the first axis 110 and the second axis 120 are coupled so that the central axis of the first axis 110 and the central axis of the second axis 120 are the same (see FIG. 3A).
  • the central axis O1 of the first shaft 110 and the central axis O2 of the second shaft 120 are eccentric.
  • the steering device 100 includes a first rack guide 561 that presses the first rack forming portion 116 from the back side (back side) toward the first pinion 16, and the second rack forming portion 126 on the back side. And a second rack guide 562 for pressing toward the second pinion 23.
  • the first rack guide 561 includes a guide part 561a having an arc surface corresponding to the shape of the back surface side of the first rack forming part 116, and a coil spring 561b that biases the guide part 561a toward the first pinion 16. I have.
  • the second rack guide 562 includes a guide portion 562a having an arc surface corresponding to the shape of the back surface side of the second rack forming portion 126, and a coil spring 562b that biases the guide portion 562a toward the second pinion 23. And.
  • the first rack forming portion 116 is sandwiched between the first pinion 16 and the first rack guide 561, and the second rack forming portion 126 is sandwiched between the second pinion 23 and the second rack guide 562.
  • FIG. 9 is a cross-sectional view of a rack shaft 12G according to the first modification of the embodiment of the present invention.
  • the shape of the cross section of the first rack forming portion 116 of the first shaft 710 is indicated by a solid line
  • the shape of the cross section of the second rack forming portion 126 of the second shaft 720 is indicated by a two-dot chain line.
  • each part of the first rack forming part 116 are smaller than the dimensions of each part of the second rack forming part 126.
  • the dimensions of the above-mentioned parts include the rack tooth widths W1 and W2, the lengths of the long axes (long diameters a1 and a2) and the short axes (short diameters b1 and b2) in the rack forming part, and the thickness of the rack forming part. T1 and T2, and Z axis dimensions Z1 and Z2 from the center axis O of the rack shaft to the reference pitch lines P1 and P2 are included.
  • the rack shaft 12G according to the modification 1 is not limited to changing all the dimensions of each part in the cross-sectional shape orthogonal to the central axis O, and at least the major axis a1 and a2 has the first axis 710. And the second axis 720 may be different.
  • the rack teeth may be formed so that the tooth width W ⁇ b> 1 of the first rack 115 is the same as the outer diameter D ⁇ b> 1 of the first rack forming portion 116.
  • the rack teeth may be formed such that the rack tooth widths W1 and W2 are larger than the outer diameters D1 and D2 of the shaft (W1> D1, W2> D2).
  • shaft demonstrated the example formed from the same material
  • this invention is not limited to this.
  • the first axis and the second axis may be formed from different materials.
  • the second shaft is made stronger than the first shaft by using a material having a higher strength than the material of the first shaft (ie, a material having a high tensile strength). Also good.
  • the outer diameter of the second shaft can be made smaller than the outer diameter of the first shaft.
  • the materials of the first shaft and the second shaft can be made different.
  • the diameter of the first axis or the second axis, the axis crossing angle, the inter-axis distance between the center axis of the rack shaft and the center axis of the pinion, and the like can be adjusted to improve the mountability to the vehicle.
  • the present invention is not limited to the case where the outer diameter of the connecting cylinder portion of one shaft is the same as the outer diameter of the main body portion of the other shaft.
  • the outer diameter of the connecting cylinder portion of the first shaft and the outer diameter of the connecting cylinder portion of the second shaft may be different from the outer diameters of the main body portion of the first shaft and the main body portion of the second shaft.
  • a rack shaft can be reduced in weight by making the connecting cylinder part of a 1st axis
  • the strength of the rack shaft can be improved by making the connecting cylinder portion of the first shaft and the second shaft larger in diameter than the main body portion of the first shaft and the main body portion of the second shaft.
  • the rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G have first shafts 110, 210, 310A, 310B, 410A on which a first rack 115 to which a steering force is transmitted is formed.
  • 410B, 410C, 710 and a second rack 125 to which the driving force of the electric motor 21 is transmitted are formed, and the second shaft is coupled to the first shaft 110, 210, 310A, 310B, 410A, 410B, 410C, 710.
  • the mass can be reduced compared to the case where the outer diameter of one shaft is the same as the outer diameter of the other shaft.
  • the rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G can be reduced in weight.
  • the rack shafts 12A, 12B1, 12B2, 12C1, 12D1, 12D2, 12D3, 12E, and 12G have the first shafts 110, 210, 310A, 410A, 410B, 410C, and 710 having the outer diameter D1 of the second shafts 120, 220, and 320A.
  • 420A, 420B, 420C, 720 is smaller than the outer diameter D2.
  • the outer diameter D1 of the first shaft 110, 210, 310A, 410A, 410B, 410C, 710 having a smaller load acting than the second shaft 120, 220, 320A, 420A, 420B, 420C, 720 is reduced. Accordingly, the outer diameters D1 and D2 of the first shafts 110, 210, 310A, 410A, 410B, 410C, and 710 and the second shafts 120, 220, 320A, 420A, 420B, 420C, and 720 are required for the respective shafts. It is possible to reduce the weight while satisfying the required strength.
  • the central axis O2 of the second shaft 120 is eccentric with respect to the central axis O1 of the first shaft 110.
  • the rack shafts 12C1 and 12C2 are configured such that one of the first shafts 310A and 310B and the second shafts 320A and 320B has a smaller mass per unit length and a larger mass per unit length. It is formed long.
  • the rack shafts 12C1 and 12C2 can be reduced in weight.
  • the steering device 100 includes rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G, and an electric motor 21, and the rotational force of the electric motor 21 is passed through the second rack 125.
  • This is an electric power steering device for transmitting to rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G.
  • the steering device 100 can be reduced in weight.

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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)
  • Transmission Devices (AREA)

Abstract

L'invention concerne un arbre à crémaillère (12A) comprenant : un premier arbre (110) sur lequel est formée une première crémaillère (115) s'engrenant avec un premier pignon (16) qui est entraîné en rotation lorsqu'un volant de direction (1) est tourné ; et un second arbre (120) sur lequel est formée une seconde crémaillère (125) s'engrenant avec un second pignon (123) entraîné en rotation par un moteur électrique (21) et qui est raccordé au premier arbre (110). Le premier arbre (110) et le second arbre (120) présentent des diamètres externes différents.
PCT/JP2018/008566 2017-03-30 2018-03-06 Arbre à crémaillère et dispositif de direction assistée électrique WO2018180281A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2017068413A JP2018167780A (ja) 2017-03-30 2017-03-30 ラックシャフト及び電動パワーステアリング装置
JP2017-068413 2017-03-30

Publications (1)

Publication Number Publication Date
WO2018180281A1 true WO2018180281A1 (fr) 2018-10-04

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WO (1) WO2018180281A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3903962A4 (fr) * 2018-12-27 2022-10-05 NSK Ltd. Arbre d'entraînement linéaire pour direction, direction, et procédé de fabrication correspondant

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001151132A (ja) * 1999-11-26 2001-06-05 Honda Motor Co Ltd 電動パワーステアリング装置
JP2014046803A (ja) * 2012-08-31 2014-03-17 Hitachi Automotive Systems Steering Ltd ラックバーの製造方法、ラックバー及び電動パワーステアリング装置
JP2014151833A (ja) * 2013-02-12 2014-08-25 Nsk Ltd デュアルピニオン式電動パワーステアリング装置のラック軸及びその製造方法
JP2014234882A (ja) * 2013-06-03 2014-12-15 高周波熱錬株式会社 ラック製造方法及び中空ラックバー

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001151132A (ja) * 1999-11-26 2001-06-05 Honda Motor Co Ltd 電動パワーステアリング装置
JP2014046803A (ja) * 2012-08-31 2014-03-17 Hitachi Automotive Systems Steering Ltd ラックバーの製造方法、ラックバー及び電動パワーステアリング装置
JP2014151833A (ja) * 2013-02-12 2014-08-25 Nsk Ltd デュアルピニオン式電動パワーステアリング装置のラック軸及びその製造方法
JP2014234882A (ja) * 2013-06-03 2014-12-15 高周波熱錬株式会社 ラック製造方法及び中空ラックバー

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