JP2000084750A - Inertial press fitting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the change of press fit amount caused by the error of press fitting margins when two members are assembled by the press fitting to obtain an assembly. SOLUTION: When an assembly is formed by press fitting a moving member having a fitting edge part formed with serration, into a stationary member having a fitting hole, a tooth part 20 of the serration is formed into the shape of isosceles trapezoid as the shape of which an apex is not sharp. In a case when the moving member and the stationary member are fitted with one another by the press fitting, at least one of the moving member and the stationary member is deformed, but a rate of change of a volume of a deformed part can be reduced by applying the isosceles trapezoidal shape to the tooth part 20 of the serration, and the change of press fitting amount can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a first member having a fitting end formed with serrations, and a second member having a fitting hole fitted with the fitting end of the first member. The present invention relates to an inertial press-fitting method in which kinetic energy is applied to at least one of the members and the first member and the second member are press-fitted by inertial motion of a member to which the kinetic energy is applied.

[0002]

2. Description of the Related Art An example of the above inertial press-fitting method is disclosed in Japanese Unexamined Patent Publication No.
No. 66421. The assembly is formed by press-fitting the serrated fitting end of the first member into the fitting hole of the second member. The material forming the first member and the material forming the second member are formed. In some cases, the teeth of the serrations of the first member are crushed, the inner peripheral surface of the fitting hole of the second member is shaved, or both occur. Hereinafter, the above-described deformation that occurs at the time of press-fitting is referred to as “a deformation of at least one of the first member and the second member”. In any case,
The outer diameter of the fitting end portion where the serration of the first member is formed before fitting is larger than the inner diameter of the fitting hole of the second member, and this difference is referred to as a press-fitting allowance. It is desirable that the press-fitting margin is set to a fixed size, but there is an error. Due to this error, the press-fitting amount of the assembly (the length at which the two members are tightly fitted at the end of the press-fitting, and the fitting length Can also be changed).

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an inertial press-fitting method capable of reducing a change in press-fit amount caused by an error in a press-fit margin. According to the present invention, the inertial press-fitting method of the following embodiment is obtained. As in the case of the claims, each aspect is divided into sections, each section is numbered, and if necessary, the other sections are cited in a form in which the numbers are cited. This is to illustrate the technical features and combinations thereof described in the present invention, and it should be construed that the technical features and combinations thereof described herein are limited to the following. is not. (1) First having a serrated fitting end
A kinetic energy is applied to at least one of the member and a second member having a fitting hole to be fitted to a fitting end of the first member, and the first member is given a kinetic energy by an inertial motion of the member to which the kinetic energy is applied. An inertial press-fitting method for press-fitting a member and a second member, wherein a cross-sectional shape of a tooth portion of the serration is not sharp at a top (claim 1). If the cross-sectional shape of the teeth of the serrations is not sharp, the change in the press-fitting amount due to the error in the press-fit allowance can be made smaller than in the case where the top is sharp. Generally, when the press-in allowance is constant, the press-in amount is increased with an increase in the applied kinetic energy (within a range in which rebound does not occur due to collision between the first member and the second member). Therefore, if the press-in allowance is constant, it is possible to control the amount of press-in by controlling the kinetic energy, and it is also possible to make the amount to be constant. However, due to an error in the outer diameter of the fitting end of the first member and an error in the inner diameter of the fitting hole of the second member, an error also occurs in the press-fitting allowance. For this reason, the volume of at least one of the first member and the second member that is deformed is changed, and the press-fit amount is changed even if the kinetic energy is the same. Then, the cross-sectional shape of the serration teeth is triangular as shown in FIG. 2A with a pointed top, and as a trapezoid with a non-pointed top as shown in FIG. As shown in FIG. 4, when the amount of change in the press-in allowance is the same, the amount of change in the amount of press-fit is smaller in the tooth B than the tooth B. This is because, when the tooth portion A and the tooth portion B are compared, the tooth portion B has at least one of the first member and the second member that are changed according to the change in the press-fitting allowance. It is presumed that the change rate is small. In the case where the kinetic energy is constant, when the press-fit amount is set to a value within the predetermined allowable range R, the allowable press-fit allowance error range for the tooth portion A is in the range ΦDA, which is narrow. The tooth portion B has an allowable error range ΦDB, which is widened. As a result, robust management of the press-fitting allowance becomes possible. If the cross-sectional shape of the tooth portion of the serration is not sharp, the influence of the press-fit allowance error on the press-fit amount is reduced, and the quality can be stabilized. As shown in FIG.
The kinetic energy required for the tooth portion A when the press-in allowance and press-in amount are the same is as shown in FIG. 2 when the root length L and the tooth height H are the same, as shown in FIG. This is because the volume deformed when the press-fitting margin is the same is smaller than the tooth portion B.
As a typical shape of the shape with no sharp top, FIG.
(B) corresponds to a trapezoid, but may be a quadrangle, a semicircle, or a polygon with rounded corners. (2) The inertial press-fitting method according to item (1), wherein the cross-sectional shape of the tooth portion of the serration is a shape in which a top of a triangle is removed. The cross-sectional shape of the serration teeth is usually triangular,
If the top is removed, the rate of volume change due to the change in the press-fitting margin can be made smaller than that of a triangular cross-section, and the change in the press-fit amount can be made smaller. The removal surface formed by removing the top may be a flat surface, a curved surface, or a combined surface of a flat surface and a curved surface. A plane M shown in FIG. 2B corresponds to an example of the removal surface. By providing the plane M, the volume change rate can be reduced, and the plane M can be referred to as a volume change rate reducing unit. The ridge line between the plane M and both inclined surfaces of the teeth may be rounded, or the plane M may be a partially cylindrical surface that is outwardly convex. The radius of curvature of the partial cylindrical surface may be the radius of a circle circumscribing all the teeth of the serration, or may be smaller. In order to substantially enjoy the effect of the invention of this embodiment, as shown in FIG. 6, at least removing a portion P ₂₀ of the vertices of the triangle, 1/20 or less of the height H (0.05 h) It is more desirable to remove at least the portion of 1/10 or less, 1/5 or less, 1/4 or less, 1/3 or less, 1/2 or less, and 2/3 or less. Further, the removal line defining the portion to be removed may be a straight line L or a curve C _{1 to} C _n.
n is an arc of a circle that touches a straight line defining H / 3 and two sides of the triangle. The removal line may be an arc of a circle centered on the center of the fitting end of the first member where the serration is formed. Further, in addition to defining the part to be removed based on the height of the triangle as described above, it is also possible to define the part to be removed by the radius of an arc that is in contact with two sides adjacent to the vertex of the triangle. The radius R is 1/20 or less of the height H of the triangle (R ≦ 1 /
20H), it is desirable to remove at least a portion on the vertex side of the arc, which is 1/10 or less, 1/5 or less, 1 /
It is further desirable to remove at least a portion of 4 or less, 1/3 or less, 1/2 or less, and 2/3 or less. Here, “remove at least the portion” means, for example, a portion opposite to the vertex from each of the circles, such as a case where a portion on the vertex side is removed from a straight line connecting the contact point between each of the circles and the two sides. Does not prevent removal. (3) First having a serrated fitting end
A kinetic energy is applied to at least one of the member and a second member having a fitting hole to be fitted to a fitting end of the first member, and the first member is given a kinetic energy by an inertial movement of the member to which the kinetic energy is applied. An inertial press-fitting method for press-fitting a member and a second member, wherein the shape of the serration is adjusted by changing a press-fitting margin in press-fitting the fitting end into the fitting hole. An inertial press-fitting method in which a change in the press-fit amount in the fitting portion with the serration is smaller than that in the case where the cross-sectional shape of the tooth portion of the serration is a sharp point. (4) By press-fitting a first member having a fitting end in which serrations of teeth having a non-pointed cross section are formed and a second member having a fitting hole fitted with the serrations. The resulting assembly. According to the assembly described in this section, the torsion torque strength in the case where the press-in allowance is the same as that of the assembly in which the cross-sectional shape of the serration of the serration at the fitting end of the first member is a sharp top. Can be increased. Further, concentricity between the first member and the second member can be improved, and the accuracy of the assembly can be improved.

[0004]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, more specific embodiments of the present invention will be described in detail with reference to the drawings. The present embodiment is a method of press-fitting the first member into the second member with the first member being a moving member and the second member being a stationary member. Specifically, as shown in FIG. This is a method in which the fitting end portion 12 is accelerated and pressed into the fitting hole 16 of the second member 14. In the illustrated example, the first member 10 is a torsion bar used in a power steering device of a vehicle, and the second member 14 is a shaft that is connected to the torsion bar in the power steering device so that the torsion bar cannot be disengaged and cannot rotate relatively. It is. Both members 10, 14 are made of tempered steel.

The first member 10 has a circular cross section and is formed in a rod shape extending along one axis, and has large diameter portions at both ends thereof.
One of the large diameter portions is the fitting end portion 12.
The second member 14 generally has a stepped cylindrical shape, and the fitting hole 16 which is a bottomed hole is formed at the center of one end surface. A recess 1 is formed at the center of the bottom of the fitting hole 16.
8 are formed. The recess 18 is formed by the tip of a drill when the second member 14 is prepared before boring and reaming. In order to tightly fit the fitting end 12 and the fitting hole 16, the outer diameter of the fitting end 12 before press-fitting is larger than the inner diameter of the fitting hole 16 before press-fitting. In addition, serrations 22 in which teeth 20 (see FIG. 1) and grooves extending in the axial direction are alternately arranged in the circumferential direction are formed on the outer peripheral surface of the fitting end 12.
The shape of the serrations 22 will be described later. Ideally, the press-fitting of the first member 10 and the second member 14 is performed in a state where the distal end surface of the fitting end 12 abuts against the bottom surface of the fitting hole 16. The bottom surface of the fitting hole 16 functions as a stopper for defining the press-fit amount.

This inertial press-fitting method is carried out by the inertial press-fitting device shown in FIG. The inertial press-fitting device includes a base 30, a first holding device 32 for holding the second member 14 as a press-fitted member fixedly and horizontally, and a first member 1 as a press-fitting member.
The second holding device 3 that holds the first member 0 horizontally and in an accessible manner to the second member 14 held by the first holding device 32
4 and a movement control device 36 for controlling the movement of the first member 10 held by the second holding device 34. The first holding device 32, the second holding device 34, and the motion control device 36 are all provided on the base 30. The motion control device 36 includes an acceleration device 38 and a substantial inertial motion realizing mechanism 40.

The first holding device 32 has a frame 44. The frame 44 is fixed to the base 30. The frame 44 has a hole 46 extending in the horizontal direction. The cylindrical member 4 as a holding member is provided in the hole 46.
8 is provided detachably. A pair of pins 50 as a detachable control member is attached to the cylindrical member 48 and the frame 44.
Are detachably provided in the radial direction. The pair of pins 50 are simultaneously fitted in the cylindrical member 48 and the frame 44 in the radial direction, thereby preventing the cylindrical member 48 from being detached from the frame 44. First of the second member 14
The attachment to the holding device 32 is performed as follows. First, the pair of pins 50 is removed from the first holding device 32,
The cylindrical member 48 is removed from the frame 44. Next, the second member 14 is fixed to the cylindrical member 48, and both are mounted on the frame 44.

[0008] The second holding device 34 also includes a frame 54. This frame 54 is also fixed to the base 30. The frame 54 has a bottomed holding hole 56 extending coaxially with the second member 14 held by the first holding device 32 and opening on the side of the first holding device 32.
Are formed. The holding hole 56 holds the first member 10 so as to be close to the second member 14 held by the first holding device 32 by fitting the first member 10 substantially airtightly and slidably. Is what you do. The bottom of the holding hole 56 is a stopper 58. The stopper 58 positions the first member 10 at a regular position in the holding hole 56 as shown by a broken line in the figure.

An air passage 60 is formed in the frame 54. This air passage 60 is connected to an air supply device 64 that supplies compressed air. In the middle of the air passage 60, a needle valve 66 as a control valve is provided.
The needle valve 66 has a valve element 68 slidably fitted to the frame 54, and shuts off the air passage 60 as shown in the drawing to allow air from the air supply device 64 to enter the holding hole 56. The state is switched between a cutoff state in which the inflow is prevented and an open state in which the air passage 60 is opened to allow the air to flow into the holding hole 56. This switching is performed by a cam 70 driven by a driving device (not shown).
By controlling the needle valve 66, the air pressure applied to the first member 10 can be controlled, and the kinetic energy can be controlled.

[0010] The second holding device 34 has a conduit 74 as a guide member. The conduit 74 has a frame 54 at one end.
And the other end is disposed so as to reach the large-diameter hole 76 of the second member 14 held by the first holding device 32. The conduit 74 defines a path of motion for the first member 10 by mating with the first member 10 in a substantially airtight and slidable manner. That is, in the present embodiment, the holding holes 5
6 and the conduit 74 form a guide passage for the first member 10. A groove 78 extending in the axial direction is provided on the outer periphery of a portion of the conduit 74 fitted with the second member 14.
Are formed to form an exhaust passage. The frame 44 is further provided with a communication hole 80 that allows an air chamber formed behind the first member 10 in the holding hole 56 to communicate with the atmosphere immediately before the first member 10 contacts the second member 14. I have. Therefore, immediately before the first member 10 contacts the second member 14, the pressure in the air chamber behind the first member 10 becomes substantially equal to the atmospheric pressure, and the first member 10 enters a state of performing a substantial inertial motion. . That is, the air passage 60, the air supply device 64, the needle valve 66, the cam 70, etc.
The portion forming the communication hole 80 of the frame 54 constitutes the substantial inertial motion realizing mechanism 40, and the acceleration device 38 and the substantial inertial motion realizing mechanism 40 cooperate with each other to form the motion control device 36. It constitutes.

Here, the shape of the serrations 22 of the moving member 10 will be described. Serration 22
Although it has a plurality of teeth 20, the cross-sectional shape of the teeth 20 is a trapezoidal shape as shown in FIG. Conventionally, as shown in FIG. 2A, the cross-sectional shape is a triangular shape in which the angle θ formed between the tooth bottom and the tooth surface is 45 °. While keeping the same, the angle θ was set to 50 ° to form a trapezoidal shape, and the corners were rounded.

In the inertial press-fitting device configured as described above, the second member 14 is attached to the first holding device 32 and the first member 1
After holding 0 in the second holding device 34, the press-fitting operation is performed. The assembly is obtained by press-fitting the fitting end portion 12 having the serrations 22 of the moving member 10 into the fitting hole 16 of the stationary member 14. Here, the air pressure supplied to the first member 10 is controlled to a predetermined magnitude.
In the present embodiment, since the shape of the tooth portion 20 of the serration 22 is a trapezoidal shape as shown in FIG. 1, a change in the press-fit amount due to an error in the press-fit margin is small. Therefore, the quality of the assembly can be stabilized. That is, as shown in FIG. 4, by making the cross-sectional shape of the tooth portion 20 a trapezoidal shape, the slope of the hyperbola becomes smaller than in the case of the triangular shape. Press-fit amount within allowable range R
, The allowable error range Φ of the press-in allowance can be widened, and robust management of the press-in allowance becomes possible. The value of the press-fit amount hardly deviates from the allowable range R due to the error of the press-fit allowance.

The shape of the teeth 20 of the serrations 22 is not limited to an equilateral trapezoidal shape, but may be a rectangular shape, a semicircular shape, or a shape obtained by removing a portion on the top side from each removal line shown in FIG. Although not specifically exemplified, the present invention can be embodied in other various forms based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a side view of serration teeth formed at a fitting end of a moving member used for performing an inertial press-fitting method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional shape of a tooth portion of the serration in comparison with a cross-sectional shape of a tooth portion of a conventional serration.

FIG. 3 is a diagram showing a relationship between a press-fit amount and a kinetic energy amount of an assembly obtained by press-fitting the moving member into a stationary member in comparison with a relationship of a conventional assembly.

FIG. 4 is a diagram showing a relationship between a press-fitting allowance and a press-fit amount of an assembly obtained by press-fitting the moving member into a stationary member, in comparison with a relationship of a conventional assembly.

FIG. 5 is a front sectional view showing an inertial press-fitting device suitable for performing an inertial press-fitting method according to an embodiment of the present invention.

FIG. 6 is a side view of serration teeth formed on a fitting end of another moving member.

[Explanation of symbols]

10: First member 12: Fitting end 14: Second member 16: Fitting hole 20: Tooth 22: Serration 32: First holding device 34: Second holding device
36: motion control device 38: acceleration device 40: substantial inertial motion realization mechanism 64: air supply device 66: needle valve

Claims (2)

[Claims] A kinetic energy is applied to at least one of a first member having a fitting end having serrations and a second member having a fitting hole fitted with the fitting end of the first member. An inertial press-fitting method of press-fitting a first member and a second member by inertial motion of a member to which the kinetic energy is applied, wherein a cross-sectional shape of the tooth portion of the serration has a shape without a sharp top. An inertial press-fitting method characterized by: 2. The inertial press-fitting method according to claim 1, wherein a cross-sectional shape of the tooth portion of the serration is a shape from which a top of a triangle is removed.