Metal working – Method of mechanical manufacture – Assembling or joining
Reexamination Certificate
2000-10-03
2002-10-08
Hughes, S. Thomas (Department: 3726)
Metal working
Method of mechanical manufacture
Assembling or joining
C029S525000, C029S522100, C029S451000, C029S423000, C072S056000, C403S279000, C403S280000, C403S282000
Reexamination Certificate
active
06460242
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the art of press-fitting two members with each other and particularly to the art of applying a kinetic energy to at least one of two members in a direction which causes the two members to approach each other, and thereby press-fitting the two members with each other.
BACKGROUND ART
The above-indicated press-fit art is the art of utilizing inertia of at least one of two members and press-fitting the two members with each other by impact thereof, and is disclosed in Japanese Patent Application laid open under Publication No. 9-66421.
DISCLOSURE OF INVENTION
Generally, the inertia-press-fit art requires the art of stabilizing a relative position of two members at a time when the press-fitting of the two members ends (hereinafter, referred to simply as the “press-fit-end position”). To meet this requirement, the present inventors had proposed, in the inertia-press-fit art, the art of defining the press-fit-end position of two members by causing the two members to butt each other.
However, if, in the above-indicated art, at least one of the two members has a remaining kinetic energy immediately after the butting of the two members, the two members are rebounded from each other, so that an actual press-fit-end position of the two members is deviated from a normal position.
The present invention has been developed in the above-indicated background, and an object thereof is to provide an inertia-press-fit method which can sufficiently stabilize the press-fit-end position of two members.
The above-indicated object is achieved according to each of the following features of the present invention. Those features are given respective sequential numbers and are described, as needed, in the same manner as that in which claims are described, i.e., any feature that includes another feature shall do so by referring to the number given to the latter feature. This is for helping more easily understand that two or more of the following features may be combined. It is to be understood that the technical features, and the combinations thereof, described in the present specification are not limited to the following features and the combinations thereof.
(1) An inertia-press-fit method of applying a kinetic energy to at least one of two members in a direction which causes the two members to approach each other, and press-fitting the two members with each other, characterized by
causing the two members to butt each other to define a relative position of the two members at a time when the press-fitting ends and, immediately after the butting, causing at least one of the two members to plastically deform and thereby absorb a remaining kinetic energy of the one member.
In the present method, the remaining kinetic energy of the one member (to which the kinetic energy had been applied), at a time immediate after the butting of the two members, is absorbed into plastic-deformation energy by at least one of the two members. Therefore, in the present method, even if at least one of the two members may have a remaining kinetic energy immediately after the butting of the two members, an actual press-fit-end position of the two members is not largely deviated from a normal position.
Each of the two members may be provided by a single part or by an assembly consisting of a plurality of parts. In the latter case, the plurality of parts may include such a part which is used exclusively when the press-fitting is performed. The latter part may be a buffer member which, immediately after one of the two members to which the buffer member belongs butts the other member, plastically deforms and thereby absorbs the kinetic energy (i.e., excessive kinetic energy) which remains immediately after the butting.
(2) An inertia-press-fit method according to the feature (1), wherein at least one of the two members includes a butting portion which butts the other member, and an interference-fitting portion which interference-fits with the other member, the butting portion being more plastically deformable than the interference-fitting portion.
In this method, the butting portion contributes to absorbing the kinetic energy which remains immediately after the butting, thereby stabilizing the press-fit-end position of the two members. In addition, since the interference-fitting portion provides an anchoring effect by mechanically engaging the other member, the two members are bonded with each other with an increased strength.
(3) An inertia-press-fit method according to the feature (2), wherein the butting portion of the at least one of the two members has a Vickers hardness Hv smaller than that of the interference-fitting portion thereof.
Generally, hardness of a material has a positive correlation with yield stress. More specifically described, as hardness decreases, yield stress also decreases. As yield stress of a material decreases, the material is more likely to plastically deform and thereby absorb an external energy into plastic-deformation energy. Therefore, a material with a lower hardness is more likely to absorb an external energy. In addition, hardness of a material has a positive correlation with coefficient of rebound. More specifically described, as hardness decreases, coefficient of rebound decreases. As coefficient of rebound of a material decreases, amount of rebound of the material upon butting on another member decreases. Meanwhile, there are various hardness measuring methods one of which is known as Vickers harness. Based on those knowledges, the method according to the present feature (3) has been developed as one embodiment of the method according to the feature (2).
(4) An inertia-press-fit method according to any one of the features (1) to (3), wherein the two members include respective butting portions which butt each other, at least one of the butting portions having a shape which allows a material thereof to flow and thus plastically deform.
In the present method, the shape factor of at least one of the two butting portions assures the plastic deformation, which leads to absorbing efficiently the excessive kinetic energy immediate after the butting.
(5) An inertia-press-fit method according to any one of the features (1) to (4), wherein the two members are caused to butt each other at a stopper surface inclined relative to a plane perpendicular to the direction, to define the relative position of the two members at the time when the press-fitting ends.
In the case where the press-fit-end position of the two members are defined by causing the two members to butt each other at a stopper surface perpendicular to the direction in which the two members approach each other, a rebounding force whose magnitude is equal to that of the excessive force acting from one member to the other member immediately after the butting, acts from the other member to the one member in a direction opposite to the direction in which the excessive force acts. In contrast, in the case where the press-fit-end position of the two members are defined by causing the two members to butt each other at a stopper surface inclined relative to a plane perpendicular to the direction in which the two members approach each other, a rebounding force whose magnitude is smaller than that of the excessive force acting from one member to the other member immediately after the butting, acts from the other member to the one member in the direction opposite to the direction in which the excessive force acts. Thus, under the condition that the excessive force is same in the two cases, the rebounding force received, in the latter case, by the one member from the other member immediately after the butting is smaller than that received in the former case by the one member, so that the distance by which the one member is rebounded, in the latter case, from the other member with the excessive force immediate after the butting is smaller than that in the former case.
Based on the above-indicated knowledges, in the method according to the present feature, the press-fit-end position of the two members are defined
Endoh Kouki
Inui Michiya
Mori Hideo
Nakaoka Masaki
Shioya Shigemi
Compton Eric
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Hughes S. Thomas
Toyota Jidosha & Kabushiki Kaisha
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