JP2005014736A - Steering device and electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device and an electric power steering device capable of restraining rotation of a rack shaft while reducing friction. <P>SOLUTION: In the steering device provided with a pinion shaft 2 and the rack shaft 1 engaged to each other and a support yoke 3 slidably supporting the rack shaft 1, the rack shaft 1 has a portion of which cross section shape along the direction perpendicular to the axial direction of the rack shaft 1 is a V-shape on an opposite side of the engaged portion with the pinion shaft 2, respective sides of the V-shape are in a shape of a recessed arc, the support yoke 3 has two portions of which cross section along the direction perpendicular to the axial direction of the rack shaft 1 is a protruding arc shape abutting with the recessed arc shape of the rack shaft 1, and a radius of the recessed arc of the rack shaft 1 is larger than a radius of the protruding arc of the support yoke 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steering device and an electric power steering device that can maintain the meshing state of a rack tooth and a pinion with high accuracy.
[0002]
[Prior art]
In recent automobile steering devices, rack assist type power steering devices are often used. In the rack assist type power steering device, as the ball screw rotates due to the rotation of the electric motor, a rotational displacement (hereinafter referred to as a rack twist) is generated in the rack shaft that is screwed to the ball screw. There was a possibility that the meshing part of the pinion and the pinion might be damaged. Therefore, a direction perpendicular to the axial direction of the rack shaft on the back surface of the rack shaft, that is, the portion opposite to the meshing portion of the rack teeth and the pinion so as to stop the rotation of the rack shaft by pressing the rack shaft toward the pinion shaft. A support yoke for supporting the rack shaft is provided with a V-shaped cross-sectional shape and a V-shaped cross-sectional shape perpendicular to the axial direction of the rack shaft on the side supporting the rack shaft.
[0003]
However, when the cross-sectional shape in the direction perpendicular to the axial direction on the back surface of the rack shaft is V-shaped, the rack shaft and the support yoke are in surface contact with each other, resulting in excessive friction and particularly heavy load. When the rack twist is generated, the rack shaft and the support yoke are in line contact with each other. Therefore, there is a problem that the pressure applied to the contact portion increases and wear increases.
[0004]
In order to solve such a problem, for example, in (Patent Literature 1), (Patent Literature 2), (Patent Literature 3), and (Patent Literature 4), each side of the substantially V-shape on the rack shaft side is convex. A steering device is disclosed that has a circular arc shape and a support yoke having two portions in which the cross-sectional shape in the direction perpendicular to the axial direction of the rack shaft forms a concave arc shape at a corresponding portion as a rotation stopper. .
[0005]
By doing so, it is possible to provide a steering device and an electric power steering device that do not increase the contact area between the rack shaft and the support yoke and at the same time do not impair the function of suppressing the rotation of the rack shaft.
[0006]
[Patent Document 1]
JP 2001-18812 A [Patent Document 2]
JP 2001-10510 A [Patent Document 3]
JP 2002-87289 A [Patent Document 4]
Japanese Patent Laid-Open No. 2001-151132
[Problems to be solved by the invention]
However, the structures disclosed in (Patent Document 1) to (Patent Document 4) attempt to suppress the rotation of the rack shaft by the pressure frictional force by the support yoke, and completely stop the rotation of the rack shaft. I can't. Therefore, there has been a problem that there is a possibility that troubles such as an increase in the meshing resistance between the rack teeth and the pinion due to the rack twist, or uneven wear of the tooth surface may occur.
[0008]
The present invention has been made in view of such circumstances, and can reduce the rotation of the rack shaft while reducing the friction, increase the meshing resistance between the rack teeth and the pinion due to the rack twist, or the tooth surface. An object of the present invention is to provide a steering device and an electric power steering device that can reduce the occurrence of troubles such as uneven wear.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a steering apparatus according to a first invention includes a pinion shaft and a rack shaft that mesh with each other, and a support yoke that slidably supports the rack shaft, wherein the rack shaft includes: On the opposite side of the meshing portion with the pinion shaft, there is a portion having a substantially V-shaped cross section in a direction perpendicular to the axial direction of the rack shaft, and each side of the substantially V-shaped has a concave arc shape. None, the support yoke has two portions in which a cross-sectional shape in a direction perpendicular to the axial direction of the rack shaft forms a convex arc shape in contact with the concave arc shape of the rack shaft, The radius is larger than the radius of the convex arc in the support yoke.
[0010]
In the steering device according to the first aspect of the present invention, the rack shaft and the support yoke can be brought into line contact with each other because the radii of the arcs of the rack shaft and the support yoke are different, and the radius of the concave arc on the rack shaft side is the support yoke. Because it is larger than the radius of the convex arc on the side, even if a rotational moment is generated on the rack shaft, the rotation of the rack shaft can be reliably suppressed, and the meshing resistance between the rack teeth and the pinion due to the rack twist It is possible to reduce the increase in the number of teeth or uneven wear of the tooth surface.
[0011]
The steering device according to a second aspect of the present invention is the steering device according to the first aspect, wherein the two concave arcs of the rack shaft are connected to the center of the two concave arcs and the two portions to which the support yoke and the rack shaft are joined. The intersection of the straight lines is different from the rotation center when a rotational moment is generated on the rack shaft.
[0012]
In the steering device according to the second aspect of the invention, even when a rotational moment is generated on the rack shaft, the rotational radius of the rack shaft is determined by the center of the two concave arcs and the joint between the support yoke and the rack shaft. Unlike the case where both radii coincide with each other due to the difference from the physical turning radius, it cannot mechanically rotate. This is because the triangle formed by both radii and the center-to-center spacing is uniquely determined. Therefore, the rotation of the rack shaft can be reliably suppressed, and the increase in the meshing resistance between the rack teeth and the pinion due to the rack twist or the uneven wear of the tooth surfaces can be reduced.
[0013]
Next, in order to achieve the above object, an electric power steering apparatus according to a third aspect of the present invention includes an electric motor, a pinion shaft and a rack shaft that mesh with each other, and a support yoke that slidably supports the rack shaft. In the electric power steering apparatus including a ball screw mechanism that converts the rotation of the electric motor into a linear motion and transmits the linear motion to the rack shaft, the rack shaft is located on the opposite side of the meshing portion with the pinion shaft. The cross-sectional shape perpendicular to the axial direction of the shaft has a substantially V-shaped portion, each side of the substantially V-shaped has a convex arc shape, and the support yoke is perpendicular to the axial direction of the rack shaft. The cross-sectional shape in a certain direction has two portions forming a concave arc shape in contact with the convex arc shape of the rack shaft, and the radius of the concave arc in the support yoke is a convex circle in the rack shaft. Larger than the radius of, is characterized in that different from the rotation center when the center of the convex circular arc in the rack shaft has a rotational moment is generated in the rack shaft.
[0014]
In the electric power steering device according to the third aspect of the invention, the rack shaft and the support yoke can be brought into line contact with each other because the radii of the arcs of the rack shaft and the support yoke are different, and the radius of the concave arc on the support yoke side is When a rotational moment is generated on the rack shaft because the center of the convex circular arc shape on the rack shaft side is different from the rotation center when the rotational moment is generated on the rack shaft. Even so, the rotation radius of the rack shaft is longer than the radius of the convex arc on the rack shaft side, and the rotation of the rack shaft can be mechanically restrained, and the rack teeth and pinion meshing resistance increase due to the rack twist Or, it is possible to reduce uneven wear of the tooth surface.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
[0016]
(Embodiment 1)
FIG. 1 is a side cross-sectional view seen from the side of an automobile showing a schematic configuration of a steering apparatus according to Embodiment 1 of the present invention. As shown in FIG. 1, the pinion shaft 2 is arranged in the vertical direction, the pinion 20 is integrally formed in the lower half of the enlarged diameter, and a pair of ball bearings are arranged on the lower side and the upper side of the pinion 20. the 21 and 22 are supported inside the pinion housing of _{H 2} cylindrical.
[0017]
Pinion shaft 2 protrudes upward from the pinion housing H _2, such projecting portion is coupled to a steering wheel S, which is shown schematically.
[0018]
The middle part of the pinion housing H _2, the housing H ₁ of the cylindrical are transversely so as to have an axis in the lateral direction of the automobile, the interior of the housing H _1, the rack shaft 1, the axial direction of the housing H ₁ It is slidably supported by.
[0019]
The rack shaft 1, a pinion 20 meshing with the rack teeth 10 are formed at the intersection of the pinion housing H ₂ and the housing H _1. The rack shaft 1 protrudes from the left and right ends of the vehicle in the housing H _1. The left and right wheels of the automobile are connected to the protruding portions.
[0020]
The housing H ₁ comprises a housing H ₁ and the yoke housing H ₃ of integrally provided with cylindrical. The yoke housing H ₃ is provided so as to protrude in a direction substantially orthogonal to the housing H ₁ and the pinion housing H ₂ and in a direction opposite to the engagement portion between the rack teeth 10 and the pinion 20. Yoke housing H ₃ has a holding hole 30 having a circular cross section communicating with the housing H ₁ in the longitudinal direction of the automobile, by the holding hole 30, support the yoke 3 having a cylindrical shape, slide in the longitudinal direction of the automobile It is held movable.
[0021]
The support yoke 3 is inserted into the holding hole 30 and is pressed in the direction of the rack shaft 1 by the elastic force of the pressing spring 34 disposed on the front side of the automobile to support the rack shaft 1. The push spring 34 is provided between the support cap 32 and the support yoke 3 fixed by the lock nut 33.
[0022]
FIG. 2 is an enlarged cross-sectional view showing a cross section in the direction perpendicular to the axial direction of the rack shaft 1 in the vicinity of the meshing portion between the rack shaft 1 and the pinion shaft 2 in the steering apparatus according to Embodiment 1 of the present invention. As shown in FIG. 2, the support yoke 3 presses the rack shaft 1 from the opposite direction of the meshing portion between the rack teeth 10 and the pinion 20, and slides the rack shaft 1 while applying a preload to the meshing portion. Support as possible. The preload can be adjusted by changing the position of the support cap 32 by tightening the lock nut 33.
[0023]
The cross-sectional shape perpendicular to the axial direction of the rack shaft 1 is substantially V-shaped on the back side of the rack shaft 1, that is, on the side opposite to the meshing portion between the rack teeth 10 and the pinion 20. A concave surface is formed in which the two sides of the letter shape each have an arc shape.
[0024]
In order to correspond to such a shape, two convex surfaces whose cross-sectional shape in a direction perpendicular to the axial direction of the rack shaft 1 is an arc shape are formed at the tip of the support yoke 3 that supports the rack shaft 1. The rack receiving sheet 4 is attached so as to be in contact with the concave surface. The rack receiving sheet 4 is composed of a thin film sheet made of a material having excellent wear resistance and a low friction coefficient. For example, a coating film made of synthetic resin such as PTFE is formed on one surface of a metal plate as a base material. A metal sheet or a synthetic resin sheet such as carbon fiber reinforced polyacetanol (POM) is used. The material is not particularly limited to these.
[0025]
The radius of the two arcs on the back side of the rack shaft 1 has a larger value than the radius of the two arcs at the tip of the support yoke 3. By making the radii of the two arcs different from each other in this way, the rack shaft 1 and the support yoke 3 can be brought into line contact instead of surface contact, the friction between them can be reduced, and the back side of the rack shaft 1 can be reduced. By setting the radius of the two arcs at a larger value than the radius of the two arcs at the tip of the support yoke 3, the rotational radius of the rack shaft can be mechanically adjusted even when a rotational moment is generated in the rack shaft. Therefore, it is possible to reliably prevent the rack shaft 1 from rotating.
[0026]
FIG. 3 shows the relationship between the arc radii in the steering apparatus according to Embodiment 1 of the present invention. As shown in FIG. 3, the support yoke 3 is pressed against the back surface of the rack shaft 1 via the rack receiving sheet 4 by an elastic force by a pressing spring or the like, and presses the rack shaft 1 toward the pinion shaft 2. Since the radius R ₁ of the two arcs on the back side of the rack shaft 1 is larger than the radius R ₃ of the two arcs at the tip of the support yoke 3, the rack shaft 1 and the support yoke 3 are in contact with each other at the contact point P. In line contact.
[0027]
In addition, in order to suppress the rotation of the rack shaft 1 more effectively, the center O ₁ of the two arcs on the back side of the rack shaft 1, the center O _{3 of} the two arcs at the tip of the support yoke ₃ , and the rack two straight intersection O _P connecting the contact point P between the shaft 1 and the support yoke 3 is arranged so as not to coincide with the rotational center O _Q of the rack shaft 1.
[0028]
In this way, for example, even if the rotational moment in the drawing clockwise to the rack shaft 1 around the O _Q occurs, the movement of the rear of the rack shaft 1 by the support yoke 3 in the abutment point P Since the rotation radius of the rack shaft 1 is different from the physical rotation radius determined by the center of the two concave arcs and the joint portion of the support yoke 3 and the rack shaft 1, both radii coincide with each other. Unlike the case, it cannot rotate mechanically. Because the triangle O _{P O} Q _P defined by both radial and center-to-center spacing is from uniquely determined. Therefore, the rack shaft 1 is not inclined with respect to the pinion shaft 2 and no rack twist is generated, so that the engagement between the rack teeth 10 and the pinion 20 can be maintained with high accuracy. The same effect also when drawing counterclockwise rotation moment about the O _Q to the rack shaft 1 has occurred can be expected.
[0029]
(Embodiment 2)
Next, an electric power steering apparatus according to Embodiment 2 of the present invention will be described with reference to the drawings. 4 is an enlarged cross-sectional view showing a cross section in the direction perpendicular to the axial direction of the rack shaft 1 in the vicinity of the meshing portion of the rack shaft 1 and the pinion shaft 2 in the electric power steering apparatus according to Embodiment 2 of the present invention. is there. As shown in FIG. 4, as in the first embodiment, the support yoke 3 presses the rack shaft 1 from the opposite direction of the meshing portion between the rack teeth 10 and the pinion 20 and applies preload to the meshing portion. However, the rack shaft 1 is slidably supported.
[0030]
The cross-sectional shape in the direction perpendicular to the axial direction of the rack shaft 1 is substantially V-shaped on the back side of the rack shaft 1, that is, on the opposite side to the meshing portion between the rack teeth 10 and the pinion 20. And the convex surface which two sides of substantially V shape have a circular arc shape is formed.
[0031]
In order to correspond to such a shape, two concave surfaces whose cross-sectional shape in a direction perpendicular to the axial direction of the rack shaft 1 is an arc shape are formed at the front end portion of the support yoke 3 that supports the rack shaft 1. The rack receiving sheet 4 is attached so as to be in contact with the convex surface. The properties and materials required for the rack receiving sheet 4 are the same as those in the first embodiment.
[0032]
Further, the radius of the two arcs at the tip of the support yoke 3 has a value larger than the radius of the two arcs on the back side of the rack shaft 1. By making the radii of the arcs different in this way, the rack shaft 1 and the support yoke 3 can be brought into line contact instead of surface contact, the friction between them can be reduced, and the tip of the support yoke 3 can be reduced. By setting the radius of the two arcs to a value larger than the radius of the two arcs on the back side of the rack shaft 1, the rotation radius of the rack shaft can be mechanically adjusted even when a rotational moment is generated in the rack shaft. It cannot be maintained, and it is possible to reliably prevent the rack shaft 1 from rotating.
[0033]
FIG. 5 shows the relationship between the arc radii in the electric power steering apparatus according to Embodiment 2 of the present invention. As shown in FIG. 5, the support yoke 3 is pressed against the back surface of the rack shaft 1 via the rack receiving sheet 4 by the elastic force of a pressing spring or the like, and presses the rack shaft 1 toward the pinion shaft 2. Since the radius R ₃ of the two arcs at the tip of the support yoke 3 is larger than the radius R ₁ of the two arcs on the back side of the rack shaft 1, the rack shaft 1 and the support yoke 3 are in contact with each other at the contact point P. In line contact.
[0034]
In order to more effectively suppress the rotation of the rack shaft 1, the two arc centers O ₁ on the back side of the rack shaft 1, the two arc centers O 3 on the tip of the support yoke ₃ , and the rack shaft two straight intersection O _P are arranged so as not to coincide with the rotational center O _Q of the rack shaft 1 connecting the contact point P between 1 and support yoke 3.
[0035]
In this way, for example, even if the rotational moment in the drawing clockwise to the rack shaft 1 around the O _Q occurs, the movement of the rear of the rack shaft 1 by the support yoke 3 in the abutment point P The rack shaft 1 is restricted and cannot perform rotational movement. Therefore, the rack shaft 1 is not inclined with respect to the pinion shaft 2 and no rack twist is generated, so that the engagement between the rack teeth 10 and the pinion 20 can be maintained with high accuracy. The same effect also when drawing counterclockwise rotation moment about the O _Q to the rack shaft 1 has occurred can be expected.
[0036]
【The invention's effect】
As described above in detail, according to the present invention, the rack shaft and the support yoke are connected to each other by the difference in the arc radius of the cross-sectional shape in the direction perpendicular to the axial direction of the rack shaft at the contact surface between the rack shaft and the support yoke. In addition to being able to contact, it is possible to reliably suppress the rotation of the rack shaft, and it is possible to reduce the occurrence of increased meshing resistance between rack teeth and pinions due to rack twist, or uneven wear of the tooth surface, etc. Become.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing a schematic configuration of a steering apparatus according to Embodiment 1 of the present invention.
FIG. 2 is an enlarged cross-sectional view showing a cross section in a direction perpendicular to the axial direction of the rack shaft in the vicinity of the meshing portion between the rack shaft and the pinion shaft 2 in the steering device according to the first embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a relationship between arc radii in the steering device according to the first embodiment of the present invention.
FIG. 4 is an enlarged cross-sectional view showing a cross section in the direction perpendicular to the axial direction of the rack shaft in the vicinity of the meshing portion between the rack shaft and the pinion shaft in the electric power steering apparatus according to Embodiment 2 of the present invention.
FIG. 5 is an explanatory diagram showing a relationship between arc radii in the electric power steering apparatus according to Embodiment 2 of the present invention.
[Explanation of symbols]
1 rack shaft 2 the pinion shaft 3 support yoke 4 rack receiving two arcs of center O _P contact point in the two front end portion of the center of the arc O ₃ support yoke 3 on the rear side of the seat 10 the rack teeth 20 Pinion O ₁ rack shaft 1 Intersection O of two straight lines connecting P _Q Rotation center P of rack shaft 1 Contact point between rack shaft 1 and support yoke 3

Claims (3)

A pinion shaft and a rack shaft that mesh with each other;
In a steering apparatus comprising a support yoke that slidably supports the rack shaft,
The rack shaft has a portion having a substantially V-shaped cross section in a direction perpendicular to the axial direction of the rack shaft on the opposite side of the meshing portion with the pinion shaft, and each side of the substantially V-shaped side. Has a concave arc shape,
The support yoke has two portions in which a cross-sectional shape in a direction perpendicular to the axial direction of the rack shaft forms a convex arc shape in contact with the concave arc shape of the rack shaft,
A steering device, wherein a radius of a concave arc in the rack shaft is larger than a radius of a convex arc in the support yoke. The intersection of two straight lines connecting the center of the two concave arcs on the rack shaft and the two joining portions where the support yoke and the rack shaft are joined is a case where a rotational moment is generated on the rack shaft. The steering apparatus according to claim 1, wherein the steering apparatus is different from a rotation center. An electric motor;
A pinion shaft and a rack shaft that mesh with each other;
A support yoke that slidably supports the rack shaft;
In the electric power steering apparatus comprising a ball screw mechanism that converts the rotation of the electric motor into a linear motion and transmits it to the rack shaft,
The rack shaft has a portion having a substantially V-shaped cross section in a direction perpendicular to the axial direction of the rack shaft on the opposite side of the meshing portion with the pinion shaft, and each side of the substantially V-shaped side. Has a convex arc shape,
The support yoke has two portions in which a cross-sectional shape in a direction perpendicular to the axial direction of the rack shaft forms a concave arc shape in contact with the convex arc shape of the rack shaft,
The radius of the concave arc in the support yoke is larger than the radius of the convex arc in the rack shaft, and the center of the convex arc in the rack shaft is different from the rotation center when a rotational moment is generated in the rack shaft. Electric power steering device.

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