JP2013063723A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device that reduces an adverse effect of engagement between one pinion gear and rack bar on engagement between the other pinion gear and rack bar.SOLUTION: In the dual pinion type electric power steering device, a protrusion part 33 is provided on the opposite side in the peripheral direction of a second rack tooth R2 on the other axial end side of a rack bar 30 as an assist side, a pair of recesses 34 and 34 are formed on both sides in the peripheral direction of the protrusion part 33, and the interior angle θ of supported surfaces 34a and 34a supporting the rack bar 30 in the recessed parts 34 and 34 is set to be larger than 90° and smaller than 180°.

Description

  The present invention relates to a so-called dual pinion type electric power steering apparatus configured by engaging a pair of pinion shafts on the steering side and the assist side with one rack shaft having two rack teeth.

  As a conventional dual pinion type electric power steering device, for example, one described in Patent Document 1 below is known.

  This electric power steering device separates a first pinion gear that is linked to the steering wheel and serves to transmit the steering force, and a second pinion gear that is linked to the electric motor that generates the steering assist force and serves to transmit the steering assist force. With this configuration, the layout of the apparatus can be improved, and thereby interference with other apparatuses can be avoided.

JP 2007-39032 A

  However, in the conventional electric power steering apparatus, since both the two pinion gears and one rack bar are always meshed with each other, the meshing between one pinion gear and the rack bar is caused by the engagement between the other pinion gear and the rack bar. There was a problem that it would adversely affect the meshing.

  The present invention has been devised in view of such technical problems, and the electric motor capable of reducing the adverse effect of the meshing between the one-side pinion gear and the rack bar on the meshing between the other-side pinion gear and the rack bar. A power steering apparatus is provided.

  The present invention includes different first and second pinion gears respectively linked to the steering side and the assist side, and a rack bar formed with first and second rack teeth that respectively mesh with the respective pinion gears. In the electric power steering apparatus, in particular, with respect to the formation region of the second rack tooth in the rack bar, a protrusion is provided on the opposite side of the second rack tooth in the circumferential direction, and the rack bar is supported on both sides in the circumferential direction of the protrusion. A pair of recesses for use in the above is provided, and an angle formed by a pair of constituent surfaces constituting each recess is formed to be larger than 90 degrees and smaller than 180 degrees.

  According to the present invention, a rack based on a torsional force acting on a rack bar is provided by providing a pair of recesses formed by surfaces having an internal angle larger than 90 degrees on the supported portion on the assist side of the rack bar. It becomes possible to suppress the rotational displacement of the bar. As a result, it is possible to reduce an adverse effect on the meshing between the first pinion gear and the first rack teeth.

1 is a front view of an electric power steering apparatus according to the present invention. 1 shows a first embodiment of an electric power steering apparatus according to the present invention, and is a longitudinal sectional view according to a steering system rack and pinion component shown in FIG. It is a longitudinal cross-sectional view which concerns on the assist type | system | group rack and pinion structure part shown in FIG. It is a perspective view of the rack bar shown in FIG. It is the arrow line view which looked at the rack bar shown in FIG. 4 from the A direction. It is the arrow line view which looked at the rack bar shown in FIG. 4 from the B direction. FIG. 3 is a partially enlarged view of FIG. 2. FIG. 4 is a partially enlarged view of FIG. 3. It is sectional drawing which follows the CC line of FIG. It is a cross-sectional view of a rack bar for explaining the operational effects of the electric power steering apparatus according to the present invention. It is a cross-sectional view of a rack bar according to a conventional electric power steering device. FIGS. 7A and 7B are diagrams illustrating a state in which steering assist torque is applied to the rack bar in one-way steering, in which FIG. 7A corresponds to FIG. 5 and FIG. FIGS. 7A and 7B are diagrams illustrating a state in which steering assist torque is applied to the rack bar in the other direction steering, where FIG. 7A corresponds to FIG. 5 and FIG. FIG. 4 is a longitudinal sectional view of a steering system rack and pinion component corresponding to FIG. 2, showing a second embodiment of the electric power steering device according to the present invention.

  Hereinafter, embodiments of an electric power steering apparatus according to the present invention will be described in detail with reference to the drawings. In the following embodiments, the electric power steering apparatus according to the present invention is applied to an automobile as in the conventional case.

  FIGS. 1 to 13 show a first embodiment of the present invention. As shown in FIG. 1, this electric power steering apparatus is linked to a steering wheel (not shown), and the driver's steering force is not shown. Steering system rack and pinion component 10 that transmits to the steered wheels and an assist system rack and pinion that is linked to the electric motor M that is an electric motor and transmits the steering assist force generated by the electric motor M to the steered wheels that are not shown in the figure. And is attached to the vehicle body via a pair of brackets 40,40.

  That is, as shown in FIGS. 1 to 4, the electric power steering apparatus includes a first output shaft 11 linked to a steering wheel (not shown) and a second output shaft 21 linked to the electric motor M. The two rack bars 30 are shared, and the steering force by the driver and the steering assist force by the electric motor M are transmitted to the steered wheels (not shown) via the rack bar 30.

  As shown in FIG. 2, the steering system rack and pinion component 10 has an input shaft 12 whose one end side is linked to a steering wheel (not shown) so as to be integrally rotatable, and one end side thereof which is connected to the input shaft 12 via a torsion bar 13. A first output shaft 14 connected to the other end of the rack so as to be relatively rotatable, and a first rack and pinion used for turning by converting the rotational motion of the first output shaft 14 into the linear motion of the rack bar 30. It is mainly composed of a mechanism 11 and a torque sensor 15 that is disposed on the outer peripheral side of the input shaft 12 and detects a steering input torque based on the relative rotational displacement amount of the input shaft 12 and the first output shaft 14.

  The first rack and pinion mechanism 11 has a first pinion tooth P1 (a first pinion gear according to the present invention) formed on the outer periphery of the other end of the first output shaft 14, and the other end of the first output shaft 14. A first rack tooth R1 (see FIG. 5) formed in a predetermined range on one end side in the axial direction of the rack bar 30 arranged substantially orthogonally meshes with each other in the rotational direction of the first output shaft 14. Accordingly, the rack bar 30 moves in the axial direction, so that the direction of the steered wheels (not shown) linked to both ends of the rack bar 30 is changed.

  On the other hand, as shown in FIG. 3, the assist system rack and pinion component 20 includes a second output shaft 22 linked to the drive shaft of the electric motor M via a predetermined speed reduction mechanism, and the second output shaft 22. The second rack and pinion mechanism 21 that is used for turning by converting the rotational motion of the rack into the linear motion of the rack bar 30 is mainly configured. The speed reduction mechanism is housed in a first gear housing portion provided on the upper side of the second housing 42, which will be described later, and includes a worm shaft 23 connected to the drive shaft tip of the electric motor M, The worm gear 24 includes a worm wheel 24 fixed to the outer periphery of the base end portion of the two output shaft 22.

  The second rack and pinion mechanism 21 is substantially orthogonal to the second pinion teeth P2 (second pinion gear according to the present invention) formed on the outer periphery of the distal end portion of the second output shaft 22 and the distal end portion of the second output shaft 22. A second rack tooth R2 (see FIG. 6) formed in a predetermined range on the other end side in the axial direction of the rack bar 30 arranged in this manner meshes with the rack bar 30 in the same manner as the first rack and pinion mechanism 11. The rack bar 30 moves in the axial direction according to the rotation direction of the second output shaft 22. At this time, the electric motor M is controlled on the basis of the detection result by the torque sensor 15 or a vehicle speed signal from a vehicle speed sensor disposed on a wheel or the like not shown in the figure, and accordingly, an appropriate value corresponding to the steering torque of the driver is obtained. The steering assist torque is transmitted to the steered wheels not shown.

  As shown in FIGS. 4 to 6, the rack bar 30 is formed by joining two shaft members, and the first member 31 formed with the first rack teeth R1 and the second rack teeth R2 are formed. The formed second member 32 is joined with a predetermined angle (90 ° in this embodiment) with a phase shifted from each other.

  As shown in FIGS. 5 to 7, the first member 31 is generally formed in a substantially round bar shape, and the first rack teeth R <b> 1 are forged into a single surface within a predetermined axial range. Except for the portion where the first rack tooth R1 is formed, the cross section thereof is configured to be substantially circular (see FIG. 7). In other words, the first rack tooth forming portion having the first rack teeth R1 is formed by the one-sided first rack teeth R1 and the circular portion B1 formed on the portion (back portion) on the opposite side in the circumferential direction. It is configured. The first member 31 is joined to one end of the second member 32 by friction welding at one end formed in a cylindrical shape.

  As shown in FIGS. 5, 6, and 8, the second member 32 has a second rack tooth R <b> 2 formed in a different shape, and the second member 32 is second in a predetermined axial range. The rack teeth R2 are forged into a single surface like the first rack teeth R1 and are forged so that the back portion has a Y-shaped cross section, and both end portions 32a where the second rack teeth R2 are not formed, Only 32b is formed in a substantially cylindrical shape (see FIG. 8). In other words, a second rack tooth forming portion having the second rack tooth R2 is constituted by the one-sided second rack tooth R2 and the deformed portion B2 formed on the back portion thereof. In addition, the second member 32 is formed to have substantially the same diameter as the one end portion of the first member 31 by forming the outer end side of the one end portion 32a to have a stepped diameter, and the first member 31 is formed by the friction welding. And joined with no step.

  As shown in FIG. 8, the deformed portion B2 in the second rack tooth forming portion is provided on the opposite side of the second rack tooth R2 in the circumferential direction, and is radially outside the outer edges of the cylindrical portions 32a and 32b. And a pair of recesses 34, 34 provided on both sides in the circumferential direction of the projection 33 and recessed radially inward from the outer edges of the cylindrical portions 32a, 32b. A pair of supported surfaces 34a, 34a supported by a second rack retainer 52, which will be described later, is formed in the pair of recesses 34, 34. The pair of supported surfaces 34a and 34a are formed so that the longitudinal section thereof is substantially arc-shaped in the circumferential direction of the second member 32 and protrudes outward (on the second rack retainer 52 side). The angle formed by both of these 34a and 34a is set to be a predetermined angle θ larger than 90 degrees and smaller than 180 degrees.

  The one end side (first member 31) of the rack bar 30 and the first output shaft 14 are, as shown in FIG. 1 and FIG. It is accommodated in a gear accommodating portion provided on the lower side. The gear housing portion includes a rack housing chamber 43 that houses one end side of the rack bar 30 so as to be movable in the axial direction, and a front surface on the one end side of the rack bar 30 so as to intersect the rack housing chamber 43 (first rack teeth R1). ) And a first pinion storage chamber 44 that rotatably stores the first output shaft 14. In the communication portion between the storage chambers 43, 44, the rack bar 30 and the first pinion storage chamber 44 are arranged. One output shaft 14 is meshed.

  Further, the first housing 41 is formed so as to be substantially orthogonal to the rack housing chamber 43, with one end opened to the outside and the other end facing the back of one end of the rack bar 30. In addition, a first cylindrical retainer accommodating portion 45 is provided, and a first retainer mechanism for maintaining an appropriate meshing state between the rack bar 30 and the first output shaft 14 in the first retainer accommodating portion 45. Is housed.

  As shown in FIGS. 2 and 7, the first retainer mechanism is disposed adjacent to the rear surface on one end side of the rack bar 30, and has a substantially arc-shaped vertical cross section formed on one end side thereof (the vertical cross section is substantially circular). A first rack retainer 51 for supporting one end of the rack bar 30 via a support surface 51a (supporting portion according to the present invention) that is arcuate and convex inward; Screwed into one end of the retainer accommodating portion 45, closes one end opening of the first retainer accommodating portion 45, and preloads a first coil spring 55 to be described later by an axial position in the first retainer accommodating portion 45. The first adjusting member 53 for adjustment and the first adjusting member 53 are held in a recessed portion 51b drilled in the other end of the first rack retainer 51, and a preload is applied to the first pinion teeth P1. The first coil spring 55 that urges the rack bar 30 in the direction in which the first rack teeth R1 are engaged, and the first rack retainer 51 and the rack bar 30 are interposed, and the rack bar 30 slides. And a first sliding member 57 for smoothing.

  The first rack retainer 51 is accommodated in the first retainer accommodating portion 45 so as to be slidable in the axial direction with a minute radial clearance, and the radial clearance is the other end side of the first rack retainer 51. The inside of the 1st retainer accommodating part 45 is hold | maintained liquid-tight by being obstruct | occluded by the well-known O-rings 59 and 59 fitted by the outer periphery. The O-rings 59 and 59 also have a role of ensuring an appropriate axial center position of the first rack retainer 51 by elastically holding the first rack retainer 51 in the first retainer accommodating portion 45. ing.

  Further, a male screw portion is formed in a predetermined region in the axial direction on the inner peripheral surface of the first retainer housing portion 45, while a female screw that engages with the male screw portion on the outer peripheral surface of the first adjustment member 53. The first rack retainer is adjusted while the preload of the first coil spring 55 is adjusted by screwing the first adjusting member 53 to the inner periphery of the one end of the first retainer housing 45 with such a screw structure. 51 can be held. At this time, the first coil spring 55 has a pair of recesses 51 b and 53 a that are arranged to face each central portion of the outer end surface of the first rack retainer 51 and the inner end surface of the first adjustment member 53, and thus the first retainer housing portion 45. Supported within.

  On the other hand, the other end side (second member 32) of the rack bar 30 and the second output shaft 22 are, as shown in FIGS. 1 and 3, the second housing 42, which is the other housing formed separately. It is accommodated in a second gear accommodating portion provided on the lower side. Here, the 1st housing 41 and the 2nd housing 42 are connected with the some volt | bolt 50 via the flange parts 41a and 42a formed in each joining edge part (refer FIG. 1). At this time, both the housings 41 and 42 are connected to each other through the long holes 41b and 42b extending in the circumferential direction at the both flange portions 41a and 42a. It is configured to be relatively rotatable in the width range. This eliminates the need to form the housings 41 and 42 with high accuracy in accordance with the phase angle θ of the members 31 and 32, thereby reducing the manufacturing cost of the apparatus (see FIG. 9). .

  Similarly to the gear housing portion according to the first housing 41, the second gear housing portion intersects the rack housing chamber 46 and a rack housing chamber 46 that houses the rack bar 30 so as to be movable in the axial direction. And a second pinion housing chamber 47 that is disposed so as to face the other end side front surface (second rack tooth R2) of the rack bar 30 and that rotatably accommodates the second output shaft 22. The rack bar 30 and the second output shaft 22 mesh with each other at the communicating portion of the storage chambers 46 and 47.

  Similarly to the first housing 41, the second housing 42 is formed so as to be substantially orthogonal to the rack housing chamber 46, with one end opened to the outside and the other end of the rack bar 30. A substantially cylindrical second retainer accommodating portion 48 configured to face the rear surface on the other end side is provided, and in the second retainer accommodating portion 48, the rack bar 30 and the second output shaft 22 are properly arranged. A second retainer mechanism that holds the meshed state is accommodated.

  As shown in FIGS. 3 and 8, the second retainer mechanism is disposed adjacent to the rear surface on the other end side of the rack bar 30 and has a substantially arc-shaped vertical cross section formed on one end side thereof (the vertical cross section is substantially the same). A second rack retainer 52 for supporting the other end of the rack bar 30 via a support surface 52a (a support portion according to the present invention) that is arcuate and convex inward; Screwed into one end of the second retainer accommodating portion 48, closes one end opening of the second retainer accommodating portion 48, and against the second coil spring 56 described later depending on the axial position in the first retainer accommodating portion 45. The second adjustment member 54 used for adjusting the preload and the second pinion teeth are held in a state in which the preload is applied by the second adjustment member 54 in the recess 52b formed in the other end of the second rack retainer 52. P2 And a second coil spring 56 for urging the rack bar 30 in the direction in which the second rack teeth R2 are meshed, and a second rack retainer 52 and the rack bar 30. And a second sliding member 58 for smoothing.

  Similar to the first rack retainer 51, the second rack retainer 52 is accommodated in the second retainer accommodating portion 48 so as to be slidable in the axial direction with a minute radial clearance, and the second rack retainer 52 The radial gap is closed by well-known O-rings 59 and 59 fitted on the outer periphery on the other end side. A male threaded portion is formed on the inner peripheral surface of the second retainer accommodating portion 48 on the one end side, and a female threaded portion is formed on the outer peripheral surface of the second adjusting member 54 to be engaged with the male threaded portion. The member 54 is screwed to the inner periphery of one end portion of the second retainer accommodating portion 48, whereby the second rack retainer 52 is held while adjusting the preload of the second coil spring 56. At this time, the second coil spring 56 has a pair of recesses 52 b and 54 a that are opposed to the central portions of the outer end surface of the second rack retainer 52 and the inner end surface of the second adjustment member 54, and has a second retainer receiving portion 48. Supported within.

  Further, the support surfaces 52a and 52a of the second rack retainer 52 are set so that the curvature 52r is larger than the curvature 34r of the supported surfaces 34a and 34a of the rack bar 30 (see FIG. 8).

  Hereinafter, characteristic operation and effects of the electric power steering apparatus according to the present embodiment will be described based on FIGS. 10 to 13 with reference to FIGS. 2 and 3.

  As described above, in the electric power steering apparatus, the rack and pinion mechanisms 11 and 21 apply the preloads F1 and F2 to the rack bar 30 by the coil springs 55 and 56, respectively. The backlash between the teeth P1, P2 and the rack teeth R1, R2 is set to be zero.

  However, at this time, the load input from the output shafts 14 and 22 to the rack bar 30 by the rack and pinion mechanisms 11 and 21 is the input load from the driver as shown in FIGS. The steering assist torque, which is an input load from the electric motor M, is much larger than the steering torque, and the steering assist torque T2 cannot be suppressed by the preload F2 alone. The steering assist torque T2 invites a roll moment M1 in the radial direction (twisting direction) and a pitching moment M2 in the axial direction (axial direction).

  As a result, the steering side (the first member 31 side) with a small input load loses the roll moment M1, and in the case of unidirectional steering in which the rack bar 30 moves to the left in the figure, As shown in FIG. 12 (b), the force acting in the meshing direction is reduced, and the two teeth P1 and R1 become so-called one-sided on the steering side, and problems such as the generation of rattle noise due to the lack of meshing. I will be invited. Further, in the case of reverse direction steering (the other direction steering in which the rack bar 30 moves to the right side in the figure), the steering is lost as shown in FIG. 13B by losing the pitching moment M2. On the side, since a reaction force (radial component RT2) against the steering assist torque T2 increased by the pitching moment M2 is applied to the preload F1, it acts in the meshing direction as opposed to the one-way steering described above. As a result, the force becomes excessive and a uniform steering feeling that is uniform cannot be obtained.

  Therefore, in the present embodiment, the angle ω formed by the supported surfaces 34a and 34a on the other end side of the rack bar 30 having a large input load so that the cross section thereof is substantially Y-shaped (different shape). Is configured by the second member 32 formed so as to be larger than 90 degrees and smaller than 180 degrees, as shown in FIG. 10 and FIG. The support point S2 of the second rack retainer 52 with respect to the member 32) can be made closer to the center C of the second member 32 than the support point S1 according to the conventional rack bar having a substantially circular longitudinal section.

  That is, as the support point S2 of the second rack retainer 52 approaches the center C of the second member 32, the distance X from the meshing point E of the two teeth P2 and R2 is shortened, so that the roll moment M1 is reduced. Accordingly, the radial displacement of the rack bar 30 based on the roll moment M1 can be suppressed. As a result, the contact between the teeth P1 and R1 in the first rack and pinion mechanism 11 is suppressed, and an appropriate meshing between the teeth P1 and R1 is obtained, resulting in problems such as the generation of the rattle noise. Can be reduced.

  Further, as the support point S2 of the second rack retainer 52 approaches the center C of the second member 32, the angle δ between the center C of the second member 32 and the support point S2 is increased. , It is possible to increase the force (preload F2 (radial component F2y)) that opposes the steering assist torque T2 (see FIG. 10 and FIG. 11 for comparison), thereby reducing the pitching moment M2, The displacement of the rack bar 30 in the axial direction based on the pitching moment M2 can also be suppressed. As a result, in the case of the reverse steering, even if a reaction force (radial component RT2y) against the steering assist torque T2 is applied to the preload F1 on the steering side, the pitching moment M2 can be suppressed to the meshing direction. It becomes possible to suppress an increase in the acting force, and the steering feeling can be made close to uniform (see FIG. 13B).

  As described above, according to the present embodiment, the angle θ formed by the supported surfaces 34a and 34a is larger than 90 degrees and smaller than 180 degrees on the other end side of the rack bar 30 serving as the assist side. By configuring the cross section to have a substantially Y shape, it is possible to suppress radial displacement of the rack bar 30 based on the roll moment M1 acting on the rack bar 30. As a result, it is possible to reduce adverse effects on the meshing between the teeth P1 and R1 in the first rack and pinion mechanism 11 on the steering side.

  Furthermore, this unique configuration makes it possible to reduce the force acting in the meshing direction on the steering side based on the pitching moment M2 caused by the large steering assist torque on the assist side. -Appropriate meshing in the pinion mechanism 11 is obtained, and a uniform steering feeling is ensured.

  In the electric power steering apparatus, the supported surfaces 34a and 34a on the other end side of the rack bar 30 and the support surfaces 34a and 34a that support the supported surfaces 34a and 34a protrude in the same direction. And the support surfaces 52a and 52a have a curvature 52r larger than the curvatures 34r of the supported surfaces 34a and 34a, and therefore a particularly large load acts. The followability of the support surfaces 52a and 52a with respect to the rack bar 30 (supported surfaces 34a and 34a) when an input load is applied to the rack bar 30 on the assisting side can be improved.

  Further, since the other end side of the rack bar 30 is formed in the Y-shape, the rack bar 30 is also reduced in weight, so that not only the apparatus can be reduced in weight but also the steering response can be improved. Can contribute.

  In forming the odd-shaped rack bar 30, it is possible to suppress an increase in manufacturing cost by joining the divided members 31 and 32 by the friction welding or the like.

  FIG. 14 shows a second embodiment of the electric power steering apparatus according to the present invention, in which the arrangement of the first rack retainer is changed. Since the basic configuration other than this configuration is the same as that of the first embodiment, the same configuration and operation as the first embodiment are denoted by the same reference numerals as those of the first embodiment. Description is omitted.

  In other words, in the present embodiment, the first rack retainer 51 is disposed so as to support the rack bar 30 with respect to the first output shaft 14 by pushing it up obliquely upward in the drawing.

  More specifically, the forward / backward movement direction of the first rack retainer 51 is the action of the roll moment M1 that acts from the first output shaft 14 (first pinion tooth P1) to the rack bar 30 (first rack tooth R1). The direction is closer to the direction of action of the roll moment M2 acting on the rack bar 30 (second rack tooth R2) from the second output shaft 22 (second pinion tooth P2) than the direction.

  With this configuration, the roll moment M1 received from the second output shaft 22 can be received more efficiently by the first rack retainer 51, and the steering side such as the generation of rattle noise based on the roll moment M1 can be prevented. Adverse effects can be further reduced.

  The present invention is not limited to the configuration of each of the above embodiments. For example, the specific shape of the rack bar 30 such as the phase angle between the first member 31 and the second member 32 is used for the electric power steering apparatus. It can be changed freely according to the specifications.

  In addition, the housings 41 and 42 are not necessarily divided and can be integrally formed. In this case, the assembly work process can be particularly shortened, which can contribute to the improvement of productivity.

14 ... First output shaft (first pinion gear)
22 ... Second output shaft (second pinion gear)
30 ... Rack bar 33 ... Projection 34 ... Concave 34a ... Supported surface (surface constituting the concavity)
51 ... 1st rack retainer 52 ... 2nd rack retainer 52a ... Support surface (support part)
55 ... 1st coil spring (1st biasing member)
56. Second coil spring (second biasing member)
M ... Electric motor (electric motor)
P1 ... 1st pinion tooth (1st pinion gear)
P2 ... Second pinion tooth (second pinion gear)
R1 ... 1st rack tooth R2 ... 2nd rack tooth θ ... Angle formed (angle formed by both surfaces constituting the recess)

Claims (3)

A first pinion gear that rotates in accordance with a steering operation of the steering wheel;
A rack bar in which a first rack tooth meshing with the first pinion gear is formed on one side in the axial direction and a second rack tooth is formed on the other side;
A second pinion gear meshing with the second rack teeth;
An electric motor for applying a steering assist force to the rack shaft via the second pinion gear;
A first rack retainer disposed on the opposite side of the first pinion gear across the rack bar and supporting the rack bar when meshed with the first pinion gear;
A first urging member that urges the rack bar in a meshing direction with the first pinion gear via the first rack retainer;
A second rack retainer disposed on the opposite side of the second pinion gear across the rack bar and supporting the rack bar when engaged with the second pinion gear;
An electric power steering device comprising: a second urging member that urges the rack bar in a meshing direction with the second pinion gear via the second rack retainer;
The rack bar includes a protrusion provided on a side opposite to the second rack tooth in a region opposite to the second rack tooth in a region where the second rack tooth is formed, and the protrusion opposite to the circumferential direction of the second rack tooth. And a pair of recesses provided on both sides in the circumferential direction of the unit,
The second rack retainer has a pair of support portions including a contact portion that contacts the pair of recesses,
The pair of recesses is formed such that an angle on the second rack tooth side formed by a surface constituting the recess on one side and a surface constituting the recess on the other side is greater than 90 degrees and less than 180 degrees. An electric power steering device. The pair of recesses are formed in an arc shape that protrudes outward in the circumferential direction of the rack bar,
The pair of support portions have an arc shape that protrudes inward in the circumferential direction of the rack bar, and the curvature thereof is larger than that of the pair of recesses. Item 4. The electric power steering device according to Item 1.   The first rack retainer twists the rack bar acting on the rack bar from the second pinion gear with respect to the direction of the force acting on the torsion direction of the rack bar acting on the rack bar from the first pinion gear. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is provided so as to move forward and backward in a direction close to a direction in which a force related to the direction is applied.

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