JP2019218967A - Rack shaft, steering device and method for manufacturing rack shaft - Google Patents

Abstract

To provide a rack shaft that has high-shape accuracy and can be readily manufactured by forging.SOLUTION: A rack shaft is shaped by forging. The rack shaft includes: a plurality of rack teeth arranged along an axial direction of the rack shaft; and a part to be guided that is arranged on an opposite side to the rack teeth and held by a rack guide. The rack guide includes a first recess that is a groove provided at a surface facing the rack guide.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a rack shaft, a steering device, and a method of manufacturing a rack shaft.

  2. Description of the Related Art A steering device including a rack shaft and a pinion that converts rotation of a steering wheel into a linear motion is known. For example, Patent Literature 1 discloses an example of a rack and pinion type steering device. As shown in Patent Document 1, the rack shaft is supported by a rack guide, and moves in the axial direction according to the rotation of the pinion.

JP-A-8-133100

  By the way, it may be required to manufacture the rack shaft by forging. When the rack shaft is manufactured by forging, it is difficult to form the entire portion of the rack shaft facing the rack guide into a predetermined shape. For this reason, it is not easy to manufacture a rack shaft having high shape accuracy by forging.

  The present disclosure has been made in view of the above problems, and has as its object to provide a rack shaft that has high shape accuracy and can be easily manufactured by forging.

  In order to achieve the above object, a rack shaft according to an embodiment of the present disclosure is a rack shaft formed by forging, and a plurality of rack teeth arranged along an axial direction of the rack shaft; And a guided portion which is arranged on the opposite side to the rack guide and is held by a rack guide, wherein the guided portion includes a first concave portion which is a groove provided on a surface facing the rack guide.

  This eliminates the need for forming the first concave portion, which is not the portion in contact with the rack guide, into a predetermined shape. It is not necessary to form the entire guided portion into a predetermined shape. For this reason, in the guided portion, the range in which the shape accuracy needs to be high is narrowed. As a result, the rack shaft has high shape accuracy and can be easily manufactured by forging. Further, the first concave portion can be filled with a lubricant. Thus, the rack shaft can suppress an increase in frictional resistance between the rack shaft and the rack guide.

  As a desirable mode of the above-mentioned rack axis, the guided part is provided with the 1st curved surface which is the curved surface arranged at the edge of the 1st crevice. Thereby, the movement of the rack shaft becomes smooth.

  As a desirable mode of the above-mentioned rack axis, the above-mentioned guided part is provided with the 2nd curved surface which is a curved surface in contact with the above-mentioned rack guide. The first curved surface is disposed inside a circle drawn by the second curved surface. This suppresses the contact between the periphery of the first recess and the rack guide, thereby improving the supportability of the rack shaft.

  As a preferable aspect of the rack shaft, the guided portion includes a second concave portion provided on a bottom surface of the first concave portion. Thereby, the amount of the lubricant that can be filled can be increased.

  As a desirable mode of the above-mentioned rack axis, the above-mentioned guided part is provided with a plurality of above-mentioned 1st crevice. Thereby, it is possible to provide the first concave portion only in a necessary portion.

  As a desirable mode of the above-mentioned rack shaft, the depth of one of the first concave portions is different from the depth of the other of the first concave portions. Thus, by arranging the deep first concave portion in a portion requiring more lubricant, it is possible to further suppress an increase in frictional resistance between the rack shaft and the rack guide.

  In order to achieve the above object, a steering device according to one embodiment of the present disclosure includes the rack shaft described above, and a rack guide that supports the rack shaft. Accordingly, the rack shaft has a high shape accuracy, so that the steering device can reduce vibration generated in the rack shaft.

  As a desirable mode of the above-mentioned steering device, the rack guide has a concave curved surface which is a surface facing the guided portion, and the first concave portion is arranged so as to face a bottom of the concave curved surface. Thereby, even when the rack guide is worn, the contact position of the rack shaft with the rack guide does not approach the bottom side of the concave curved surface more than the first concave portion. For this reason, since the component force in the width direction that the rack shaft receives from the rack guide is maintained at a predetermined value or more, the supportability of the rack shaft is maintained.

  As a desirable mode of the steering device described above, the first recess is arranged so as to face the rack guide when the rack shaft is at a neutral position. Thus, the first concave portion is arranged in a portion of the rack shaft where the frequency of contact with the rack guide is high. Therefore, the steering device can further reduce the vibration generated in the rack shaft.

  In order to achieve the above object, a method of manufacturing a rack shaft according to an embodiment of the present disclosure is directed to a method of manufacturing a rack shaft, the method comprising: a plurality of rack teeth arranged along an axial direction of a rack shaft; A method of manufacturing a rack shaft, comprising: a guided portion held by a guide, wherein the guided portion includes a first concave portion which is a groove provided on a surface facing the rack guide; , And the first concave portion are formed by forging.

  This eliminates the need for forming the first concave portion, which is not the portion in contact with the rack guide, into a predetermined shape. It is not necessary to form the entire guided portion into a predetermined shape. For this reason, in the guided portion, the range in which the shape accuracy needs to be high is narrowed. As a result, according to the rack shaft manufacturing method, a rack shaft having high shape accuracy can be easily manufactured by forging.

  The rack shaft of the present disclosure has high shape accuracy and can be easily manufactured by forging.

FIG. 1 is a schematic diagram of the steering device of the present embodiment. FIG. 2 is a front view of the steering gear unit of the present embodiment. FIG. 3 is a sectional view taken along line AA of FIG. FIG. 4 is an enlarged view of the rack shaft and the rack guide of FIG. FIG. 5 is a plan view of the rack shaft of the present embodiment. FIG. 6 is a front view of the rack shaft of the present embodiment. FIG. 7 is a rear view of the rack shaft of the present embodiment. FIG. 8 is a sectional view taken along the line BB of FIG. FIG. 9 is an enlarged view of FIG. FIG. 10 is a schematic view illustrating a method of manufacturing a rack shaft. FIG. 11 is a cross-sectional view of a rack shaft according to a first modification. FIG. 12 is a sectional view of a rack shaft according to a second modification. FIG. 13 is a sectional view of a rack shaft according to a third modification. FIG. 14 is a sectional view of a rack shaft according to a fourth modification. FIG. 15 is a sectional view of a rack shaft according to a fifth modification. FIG. 16 is a sectional view of a rack shaft according to a sixth modification.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited by the following embodiments for carrying out the invention (hereinafter, referred to as embodiments). The components in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that are in a so-called equivalent range. Furthermore, components disclosed in the following embodiments can be appropriately combined.

(Embodiment)
FIG. 1 is a schematic diagram of the steering device of the present embodiment. FIG. 2 is a front view of the steering gear unit of the present embodiment. FIG. 3 is a sectional view taken along line AA of FIG. As shown in FIG. 1, the steering device 80 includes a steering wheel 81, a steering shaft 82, a universal joint 84, a lower shaft 85, a universal joint 86, a pinion shaft 87, and the steering gear unit 1. .

  As shown in FIG. 1, the steering wheel 81 is connected to a steering shaft 82. One end of the steering shaft 82 is connected to the steering wheel 81. The other end of the steering shaft 82 is connected to a universal joint 84. One end of the lower shaft 85 is connected to the steering shaft 82 via a universal joint 84. The other end of the lower shaft 85 is connected to a pinion shaft 87 via a universal joint 86.

  As shown in FIGS. 1 and 3, the steering gear unit 1 includes a pinion 3, a rack shaft 4, a rack guide 5, a housing 10, a rack guide screw 15, and an elastic member 16. The pinion shaft 87 is connected to the pinion 3. The pinion 3 meshes with the rack shaft 4. When the pinion 3 rotates, the rack shaft 4 moves in the vehicle width direction of the vehicle. The pinion 3 and the rack shaft 4 convert the rotational motion transmitted to the pinion shaft 87 into a linear motion. The rack shaft 4 is connected to a tie rod 89. The angle of the wheel changes as the rack shaft 4 moves. The operation of the steering wheel 81 may be converted into an electric signal, and the angle of the wheel may be changed by the electric signal. That is, a steer-by-wire system may be applied to the steering device 80.

  As shown in FIG. 1, the steering device 80 includes an electric motor 93, a torque sensor 94, a vehicle speed sensor 95, and an ECU (Electronic Control Unit) 90. The electric motor 93, the torque sensor 94, and the vehicle speed sensor 95 are electrically connected to the ECU 90. The electric motor 93 is, for example, a brushless motor, but may be a motor including a brush (slider) and a commutator (commutator). The torque sensor 94 is attached to, for example, the pinion 3. The torque sensor 94 outputs the steering torque transmitted to the pinion 3 to the ECU 90 through CAN (Controller Area Network) communication. The vehicle speed sensor 95 detects a traveling speed (vehicle speed) of a vehicle body on which the steering device 80 is mounted. The vehicle speed sensor 95 is provided on the vehicle body and outputs the vehicle speed to the ECU 90 through CAN communication.

  The ECU 90 controls the operation of the electric motor 93. The ECU 90 acquires signals from each of the torque sensor 94 and the vehicle speed sensor 95. Power is supplied to the ECU 90 from a power supply device 99 (for example, a battery mounted on a vehicle) with the ignition switch 98 turned on. The ECU 90 calculates an auxiliary steering command value based on the steering torque and the vehicle speed. The ECU 90 adjusts the power value supplied to the electric motor 93 based on the auxiliary steering command value. The ECU 90 acquires information on an induced voltage from the electric motor 93 or information output from a resolver or the like provided in the electric motor 93.

  As shown in FIG. 3, the pinion 3 is supported by the housing 10 via the bearing 11 and the bearing 12. The pinion 3 includes a plurality of pinion teeth 31. The rack guide screw 15 is attached to the housing 10. For example, a screw groove provided on the outer peripheral surface of the rack guide screw 15 meshes with a screw groove provided on the inner peripheral surface of the housing 10. The elastic member 16 is disposed between the rack guide screw 15 and the rack guide 5. The elastic member 16 is, for example, a coil spring. The elastic member 16 presses the rack guide 5 against the rack shaft 4. The rack guide 5 supports the rack shaft 4. The rack guide 5 presses the rack shaft 4 against the pinion 3. Thereby, the backlash between the rack shaft 4 and the pinion 3 is suppressed.

  FIG. 4 is an enlarged view of the rack shaft and the rack guide of FIG. FIG. 5 is a plan view of the rack shaft of the present embodiment. FIG. 6 is a front view of the rack shaft of the present embodiment. FIG. 7 is a rear view of the rack shaft of the present embodiment. FIG. 8 is a sectional view taken along the line BB of FIG. FIG. 9 is an enlarged view of FIG.

  As shown in FIG. 4, the rack guide 5 includes a main body 51 and a guide 53. The main body 51 has a substantially cylindrical shape. The main body 51 is formed of, for example, metal or the like. One end face of the main body 51 contacts the elastic member 16. The other end surface of the main body 51 is formed in a semi-cylindrical shape. The guide part 53 is provided on a semi-cylindrical end face of the main body part 51. The guide portion 53 is formed of, for example, a resin or the like. The guide section 53 has a concave curved surface 531. The concave curved surface 531 is a surface facing the rack shaft 4. As shown in FIG. 4, in a section obtained by cutting the rack guide 5 on a plane orthogonal to the axial direction of the rack shaft 4, the concave curved surface 531 has, for example, a Gothic arch shape. The Gothic arch shape is a shape composed of two arcs. The concave curved surface 531 is symmetric with respect to the bottom 531a. In the following description, the axial direction of the rack shaft 4 is simply described as the axial direction.

  The rack shaft 4 is formed by forging. As shown in FIG. 4, the rack shaft 4 includes rack teeth 41 and a guided portion 42. As shown in FIG. 3, the rack teeth 41 mesh with the pinion teeth 31. As shown in FIGS. 5 and 6, the plurality of rack teeth 41 are arranged along the axial direction. The rack shaft 4 includes a first group G1, a second group G2, and a third group G3 each including a plurality of rack teeth 41. The first group G1 is arranged at the center of the portion of the rack shaft 4 where the rack teeth 41 are arranged. In the first group G1, a plurality of rack teeth 41 are arranged such that the specific stroke is constant. The specific stroke is a movement amount of the rack shaft 4 when the pinion 3 makes one rotation. The second group G2 is arranged next to the first group G1. In the second group G2, a plurality of rack teeth 41 are arranged such that the specific stroke changes depending on the position in the axial direction. The third group G3 is arranged next to the second group G2. In the third group G3, a plurality of rack teeth 41 are arranged so that the specific stroke is constant. The specific stroke of the third group G3 is larger than the specific stroke of the first group G1. The specific stroke changes depending on the specifications (pitch, shape, inclination angle of tooth trace, etc.) of the rack teeth 41. When the specifications of the rack teeth 41 are constant, the specific stroke is constant. When the specifications of the rack teeth 41 change depending on the position in the axial direction, the specific stroke changes depending on the position in the axial direction. Thus, the rack shaft 4 employs the variable gear ratio. Note that the magnitude relationship between the specific stroke of the first group G1 and the specific stroke of the third group G3 is not limited to the above-described relationship. The specific stroke of the third group G3 may be smaller than the specific stroke of the first group G1.

  As shown in FIG. 4, the guided portion 42 is arranged on the side opposite to the rack teeth 41. The guided portion 42 is held by the guide portion 53 of the rack guide 5. A part of the guided portion 42 contacts the guide portion 53. As shown in FIG. 8, the guided portion 42 includes a first recess 45, a second recess 46, a first curved surface 421, and a second curved surface 422.

  As shown in FIG. 4, the first concave portion 45 is provided on a surface facing the rack guide 5. As shown in FIG. 4, the first concave portion 45 is arranged so as to face the bottom 531a of the concave curved surface 531. As shown in FIG. 7, the first recess 45 is a linear groove extending along the axial direction. As shown in FIGS. 5 to 7, the length of the first concave portion 45 in the axial direction is equal to or greater than the distance from the rack tooth 41 at one end to the rack tooth 41 at the other end in the axial direction. The first recess 45 is arranged so as to face the rack guide 5 at least when the rack shaft 4 is at the neutral position. The neutral position is a position corresponding to a midpoint between both ends of the movement range of the rack shaft 4. For example, grease is disposed in the first recess 45 as a lubricant.

  As shown in FIG. 8, the second concave portion 46 is provided on the bottom surface of the first concave portion 45. The second concave portion 46 is arranged so as to face the bottom 531a of the concave curved surface 531. As shown in FIG. 7, the first recess 45 is a linear groove extending along the axial direction. The guided portion 42 includes a plurality of second concave portions 46. The plurality of second concave portions 46 are arranged with a gap in the axial direction.

  As shown in FIGS. 8 and 9, the first curved surface 421 is a curved surface arranged at the edge of the first recess 45. The first curved surface 421 is formed by molding the rack shaft 4 by forging. For example, the first curved surface 421 is a surface of the excess portion 43 formed at the time of forging. The surplus portion 43 is formed by extruding the material toward both sides of the first recess 45 when the first recess 45 is formed. As shown in FIG. 9, in a cross section orthogonal to the axial direction, the first curved surface 421 is disposed inside a circle C1 drawn by the second curved surface 422.

  The second curved surface 422 is a curved surface that is in contact with the guide portion 53 of the rack guide 5. As shown in FIG. 8, the second curved surface 422 is a circular arc in a cross section orthogonal to the axial direction. As shown in FIG. 4, the curvature of the second curved surface 422 is larger than the curvature of the concave curved surface 531 of the guide portion 53. That is, the radius of curvature of the second curved surface 422 is smaller than the radius of curvature of the concave curved surface 531. Therefore, the contact between the second curved surface 422 and the concave curved surface 531 is a line contact.

  As shown in FIG. 3, the rack guide 5 is pressed against the rack shaft 4 by the elastic member 16, so that the rack shaft 4 receives a force F from the guide portion 53 as shown in FIG. The force F includes a component force F1 and a component force F2. The component force F1 is a force in a direction in which the rack shaft 4 is pressed against the pinion 3. The component force F2 is a force in a direction orthogonal to the component force F1. When the component force F2 is applied to the rack shaft 4, the movement of the rack shaft 4 in a direction orthogonal to the axial direction is restricted. The supportability of the rack shaft 4 is improved. Thereby, the movement of the rack shaft 4 in the axial direction becomes smooth.

  The guide portion 53 of the rack guide 5 is worn. Accordingly, the contact position of the rack shaft 4 with the guide portion 53 approaches the bottom 531a shown in FIG. As the contact position of the rack shaft 4 with the guide portion 53 approaches the bottom 531a, the component force F2 decreases. For this reason, the movement of the rack shaft 4 in the direction orthogonal to the axial direction is less likely to be restricted. That is, the supportability of the rack shaft 4 may be reduced. On the other hand, the rack shaft 4 of the present embodiment includes the first concave portion 45 arranged so as to face the bottom 531a. Thereby, even when the guide portion 53 is worn, the contact position of the rack shaft 4 with the guide portion 53 does not approach the bottom 531 a side of the concave curved surface 531 at least more than the first concave portion 45. Therefore, the component force F2 is maintained at a predetermined value or more, so that the supportability of the rack shaft 4 is maintained.

  FIG. 10 is a schematic view illustrating a method of manufacturing a rack shaft. The method of manufacturing the rack shaft 4 includes a step of forming the rack teeth 41 and the first recesses 45 by forging. As shown in FIG. 10, the columnar intermediate material placed on the receiving member 102 is pressed by the punch 101, so that the rack teeth 41 and the first concave portion 45 are formed at the same time. The punch 101 has a shape corresponding to the rack teeth 41. The rack teeth 41 are formed by partially deforming the intermediate material along the shape of the punch 101. The receiving member 102 is provided with a protrusion corresponding to the first recess 45. The first concave portion 45 is formed by partially deforming the intermediate material along the convex portion of the receiving member 102. For example, forging is performed a plurality of times while changing the shape of the receiving member 102.

  After one forging, the intermediate material is removed from the receiving member 102. The intermediate material is pushed out of the receiving member 102 by a member called a knock pin provided so as to protrude from the receiving member 102. For example, the knock pin is provided so as to project from the convex portion of the receiving member 102. The second concave portion 46 of the guided portion 42 is formed by a knock pin. The second concave portion 46 does not necessarily need to be formed by the knock pin, and may be formed at the same time as the first concave portion 45 by partially deforming the intermediate material along the convex portion of the receiving member 102.

  The shape and arrangement of the first concave portion 45 are not limited to those described above. The number of the first concave portions 45 is not limited to one, and may be two or more. The plurality of first concave portions 45 may have the same shape, or may have different shapes.

  The rack guide 5 does not necessarily have to be a so-called sliding type. The rack guide 5 may be a so-called rolling type. That is, the rack guide 5 may include a rolling element.

  As described above, the rack shaft 4 is a rack shaft formed by forging. The rack shaft 4 includes a plurality of rack teeth 41 arranged along the axial direction of the rack shaft 4, and a guided portion 42 arranged on the opposite side of the rack teeth 41 and held by the rack guide 5. . The guided portion 42 includes a first concave portion 45 which is a groove provided on a surface facing the rack guide 5.

  Thus, it is not necessary to form the first recess 45 which is not in contact with the rack guide 5 into a predetermined shape. It is not necessary to form the entire guided portion 42 into a predetermined shape. For this reason, in the guided portion 42, the range in which the shape accuracy needs to be high is narrowed. As a result, the rack shaft 4 has high shape accuracy and can be easily manufactured by forging. Further, the first concave portion 45 can be filled with a lubricant. Thereby, the rack shaft 4 can suppress an increase in frictional resistance between the rack shaft 4 and the rack guide 5.

  In the rack shaft 4, the guided portion 42 includes a first curved surface 421 that is a curved surface disposed on an edge of the first recess 45. Thereby, the movement of the rack shaft 4 becomes smooth.

  In the rack shaft 4, the guided portion 42 includes a second curved surface 422 that is a curved surface that is in contact with the rack guide 5. In a cross section obtained by cutting the rack axis 4 on a plane orthogonal to the axial direction, the first curved surface 421 is disposed inside a circle C1 drawn by the second curved surface 422. Thereby, the contact between the peripheral portion of the first recess 45 and the rack guide 5 is suppressed, so that the supportability of the rack shaft 4 is improved.

  In the rack shaft 4, the guided portion 42 includes a second recess 46 provided on the bottom surface of the first recess 45. Thereby, the amount of the lubricant that can be filled can be increased.

  The steering device 80 includes the rack shaft 4 and the rack guide 5 that supports the rack shaft 4. Thereby, since the rack shaft 4 has high shape accuracy, the steering device 80 can reduce the vibration generated in the rack shaft 4.

  In the steering device 80, the rack guide 5 includes a concave curved surface 531 which is a surface facing the guided portion 42. The first recess 45 is arranged so as to face the bottom 531a of the concave curved surface 531. Accordingly, even when the rack guide 5 is worn, the contact position of the rack shaft 4 with the rack guide 5 does not approach the bottom 531a side of the concave curved surface 531 more than the first concave portion 45. For this reason, the component force in the width direction that the rack shaft 4 receives from the rack guide 5 (the component force F2 in FIG. 4) is maintained at a predetermined value or more, so that the supportability of the rack shaft 4 is maintained.

  In the steering device 80, the first concave portion 45 is disposed so as to face the rack guide 5 when the rack shaft 4 is at the neutral position. As a result, the first concave portion 45 is arranged in a portion of the rack shaft 4 where the frequency of contact with the rack guide 5 is high. Therefore, the steering device 80 can further reduce the vibration generated in the rack shaft 4.

  The method of manufacturing the rack shaft includes a plurality of rack teeth 41 arranged along the axial direction of the rack shaft 4, a guided portion 42 arranged on the opposite side of the rack teeth 41 and held by the rack guide 5, This is a method for manufacturing the rack shaft 4 including: The guided portion 42 includes a first concave portion 45 which is a groove provided on a surface facing the rack guide 5. The method includes a step of forming the rack teeth 41 and the first recesses 45 by forging.

  Thus, it is not necessary to form the first recess 45 which is not in contact with the rack guide 5 into a predetermined shape. It is not necessary to form the entire guided portion 42 into a predetermined shape. For this reason, in the guided portion 42, the range in which the shape accuracy needs to be high is narrowed. As a result, according to the rack shaft manufacturing method, the rack shaft 4 having high shape accuracy can be easily manufactured by forging.

(First Modification)
FIG. 11 is a cross-sectional view of a rack shaft according to a first modification. Note that the same components as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description will be omitted.

  As shown in FIG. 11, the guided portion 42A of the rack shaft 4A of the first modified example includes a plurality of first concave portions 45A. The plurality of first concave portions 45A are arranged along the axial direction. Thereby, it becomes possible to provide the first concave portion 45A only in a necessary portion.

(Second Modification)
FIG. 12 is a sectional view of a rack shaft according to a second modification. Note that the same components as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description will be omitted.

  As shown in FIG. 12, the guided portion 42B of the rack shaft 4B of the second modified example includes a first recess 451B and a first recess 452B. The first concave portion 451B and the first concave portion 452B are arranged at intervals in the axial direction. The first recess 451B is longer in the axial direction than the first recess 452B. The first recess 451B is disposed between the two first recesses 452B.

(Third Modification)
FIG. 13 is a sectional view of a rack shaft according to a third modification. Note that the same components as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description will be omitted.

  As shown in FIG. 13, the guided portion 42C of the rack shaft 4C of the third modified example includes a first recess 451C and a first recess 452C. The first recess 451C and the first recess 452C are arranged at intervals in the axial direction. The depth of the first recess 451C is different from the depth of the first recess 452C. The first recess 451C is deeper than the first recess 452C. The first recess 451C is disposed between the two first recesses 452C. Thus, by arranging the deep first concave portion 451C in a portion where more lubricant is required, it is possible to further suppress an increase in frictional resistance between the rack shaft 4C and the rack guide 5.

(Fourth modification)
FIG. 14 is a sectional view of a rack shaft according to a fourth modification. Note that the same components as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description will be omitted.

  As shown in FIG. 14, the guided portion 42D of the rack shaft 4D according to the fourth modification includes a first recess 45D. The first recess 45D is arranged only at a position corresponding to the first group G1. The first recess 45D is arranged on the opposite side of the first group G1. The axial length of the first recess 45D is equal to or less than the axial length of the first group G1.

(Fifth Modification)
FIG. 15 is a sectional view of a rack shaft according to a fifth modification. Note that the same components as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description will be omitted.

  As shown in FIG. 15, the guided portion 42E of the rack shaft 4E according to the fifth modification includes a first concave portion 45E. The first recess 45E is arranged only at a position corresponding to the third group G3. The first recess 45E is arranged on the opposite side of the third group G3. The axial length of the first recess 45E is equal to or less than the axial length of the third group G3.

(Sixth modification)
FIG. 16 is a sectional view of a rack shaft according to a sixth modification. Note that the same components as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description will be omitted.

  As shown in FIG. 16, the guided portion 42F of the rack shaft 4F of the sixth modification includes a first recess 45F. The depth of the first recess 45F differs depending on the position in the axial direction. The first concave portion 45F is deepest at a position opposite to the first group G1. The first recess 45F becomes shallower toward both ends.

Reference Signs List 1 steering gear unit 10 housing 11, 12 bearing 15 rack guide screw 16 elastic member 3 pinion 31 pinion teeth 4, 4A, 4B, 4C, 4D, 4E, 4F rack shaft 41 rack teeth 42 guided portions 42A, 42B, 42C, 42D, 42E, 42F Guided portion 43 Surplus portion 5 Rack guide 51 Main body 53 Guide portion 531 Concave curved surface 531a Bottom 80 Steering device 81 Steering wheel 82 Steering shaft 84 Universal joint 85 Lower shaft 86 Universal joint 87 Pinion shaft 89 Tie rod 90 ECU
93 Electric motor 94 Torque sensor 95 Vehicle speed sensor 98 Ignition switch 99 Power supply device 101 Punch 102 Receiving member G1 First group G2 Second group G3 Third group F Force F1, F2 Component force

Claims (10)

A rack shaft formed by forging,
A plurality of rack teeth arranged along the axial direction of the rack shaft;
A guided portion arranged on the opposite side to the rack teeth and held by a rack guide,
The rack shaft, wherein the guided portion includes a first recess which is a groove provided on a surface facing the rack guide. The rack shaft according to claim 1, wherein the guided portion includes a first curved surface that is a curved surface disposed on an edge of the first recess. The guided portion includes a second curved surface that is a curved surface in contact with the rack guide,
The rack shaft according to claim 2, wherein the first curved surface is disposed inside a circle drawn by the second curved surface in a cross section obtained by cutting the rack axis along a plane orthogonal to the axial direction. The rack shaft according to any one of claims 1 to 3, wherein the guided portion includes a second recess provided on a bottom surface of the first recess. The rack shaft according to claim 1, wherein the guided portion includes a plurality of the first recesses. The rack shaft according to claim 5, wherein a depth of one of the first concave portions is different from a depth of another of the first concave portions. A rack shaft according to any one of claims 1 to 6,
A rack guide supporting the rack shaft;
A steering device comprising: The rack guide includes a concave curved surface that is a surface facing the guided portion,
The steering device according to claim 7, wherein the first concave portion is arranged to face a bottom of the concave curved surface. The steering device according to claim 7, wherein the first recess is arranged to face the rack guide when the rack shaft is at a neutral position. A method of manufacturing a rack shaft, comprising: a plurality of rack teeth arranged along an axial direction of a rack shaft; and a guided portion arranged on a side opposite to the rack teeth and held by a rack guide,
The guided portion includes a first recess which is a groove provided on a surface facing the rack guide,
A method of manufacturing a rack shaft, comprising a step of forming the rack teeth and the first recess by forging.

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