192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2003-02-07
2004-11-30
Rodriguez, Saul (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S03000R, C192S084941, C192S209000
Reexamination Certificate
active
06823974
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon, claims the benefit of priority of, and incorporates by reference the contents of prior Japanese Patent Application No. 2002-49681 filed Feb. 26, 2002.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic clutch that transmits and terminates rotational power, and particularly, the present invention relates to a reduction in clutch operating noise generated when the electromagnetic clutch actuates and stops.
2. Description of Related Art
One type of known electromagnetic clutch is disclosed in Japanese Patent Laid-Open Publication No. 2000-179582. The patent application is composed of an armature attracted to a drive-side rotation member by an electromagnetic force generated by an electromagnetic coil, a driven-side rotation member connected to a driven-side rotation device, and a plate of ring-shaped leaf springs, as a spring means, connecting the armature to the driven-side rotation member.
The ring-shaped leaf spring comprises an outer ring portion connected to the armature, an attachment portion disposed inside the outer ring portion and connected to the driven-side rotation member, connecting portions connecting between the outer ring portion and the attachment portion, securing portions of the armature disposed in a plurality of positions of the outer ring portion in a circumferential direction, and a deflection adding portion for providing an initial deflection to the ring-shaped leaf spring. The deflection adding portion is arranged between the plural positions of the outer ring portion in the circumferential direction so that it acts to shorten an axial dimension of the electromagnetic clutch and to simplify the overall configuration.
Using the ring-shaped leaf spring in the above-mentioned configuration, since a spring force which increases non-linearly and rapidly relative to a displacement amount of the armature restricts movement of the armature just before the armature collides with the drive-side rotation member, a collision force of the armature with the drive-side rotation member is reduced to reduce the operating noise of the electromagnetic clutch.
In order to further reduce the operating noise of the electromagnetic clutch, there is an extending portion inwardly extending an arm portion, which is a securing portion disposed in the outer ring portion of the ring-shaped leaf spring to secure the leaf spring to the armature, and an elastic member disposed in an opposite position to the extending portion of the arm portion. Thus, when the electromagnetic clutch is ON, that is, when the electromagnetic force generated by the electromagnetic coil attracts the armature toward the drive-side rotation member, the elastic member is elastically compressed in a relative fashion to increase a displacement amount of the arm portion, so that the elastic member alleviates an impact of attraction of the armature to the drive-side rotation member and further reduces the clutch operating noise.
The above-mentioned leaf spring functions as a spring when the outer ring portion secured to the armature is elastically deformed. However, there is a problem in which the ring-shaped leaf spring disclosed in the above publication does not have enough compressive force to deform the elastic member, because a length from the securing portion of the armature to the extending portion of the arm portion is long and the arm portion has a large deflection. For the sake of shortening the length of the arm portion, another securing portion may be disposed inwardly, but an increase in the number of the securing portion causes additional cost because of extra connecting means like rivets.
A plurality of three arm portions are provided in a circumferential direction of the leaf spring, and an elastic member is opposed to each arm portion. Thus, there is a problem in which the electromagnetic clutch needs a large number of parts and a large number of man-hours. Furthermore, the elastic member reduces the clutch operating noise only when the electromagnetic clutch is ON. It is necessary to reduce the operating noise when the electromagnetic clutch is OFF and the armature attracted to the drive-side rotation member is separated therefrom and returns to its original position.
In view of the above fact, an object of the present invention is to provide an electromagnetic clutch whose operating noise can be reduced at a low cost by using an elastic member which is better suited to a spring force of an attracted and separated leaf spring.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, an electromagnetic clutch comprises an electromagnetic coil (
3
) for generating an electromagnetic force when being energized, a drive-side rotation member (
4
) rotated by a driving source, an armature (
5
) attracted to the drive-side rotation member (
4
) in response to the electromagnetic force generated by the electromagnetic coil (
3
) to receive rotation of the drive-side rotation member (
4
), a driven-side rotation member (
6
) connected to a driven-side device (
7
), and a spring means (
61
). The spring means (
61
) couples the armature (
5
) to the driven-side rotation member (
6
) and supports the armature (
5
) such that the armature (
5
) is capable of being displaced toward the drive-side rotation member (
4
).
The electromagnetic clutch has a spring means (
61
) composed of a plate of a polygonal leaf spring (
61
). The leaf spring (
61
) comprises an outer ring portion (
61
c
) connected to the armature (
5
), an attachment portion (
61
b
) positioned inside the outer ring portion (
61
c
) and connected to the driven-side rotation member (
6
). A connecting portion (
61
d
) that connects between the outer ring portion (
61
c
) and the attachment portion (
61
b
), and a plurality of securing portions (
62
) of the armature (
5
) are disposed in a circumferential direction of the outer ring portion (
61
c
). A plurality of first elastic members (
67
) are disposed at intermediate points of the plurality of securing portions (
62
) in the circumferential direction (around) of the outer ring portion (
61
c
) to give an initial deflection to the leaf spring (
61
).
A second elastic member (
66
) is disposed between the leaf spring (
61
) and the drive-side rotation member (
4
) in an axial direction. The second elastic member (
66
) is elastically deformed between the leaf spring (
61
) and the driven-side rotation member (
6
) when the electromagnetic force generated by the electromagnetic coil (
3
) displaces the armature (
5
) toward the drive-side rotation member (
4
) in an axial direction and the armature (
5
) collides with the first elastic portions (
67
) to determine its axial position when the electromagnetic coil (
3
) is unenergized and the armature (
5
) is separated from the drive-side rotation member (
4
) to return to an original position.
According to the above aspect of the invention, when the clutch is actuated, namely when the leaf spring (
61
) connected to the armature (
5
) is displaced in the axial direction to the drive-side rotation member (
4
), the second elastic member (
66
) is elastically compressed between the leaf spring (
61
) and the driven-side rotation member (
6
) so that an elastic reaction force is generated in the second elastic member (
66
) in response to an increase in a displacement amount of the leaf spring (
61
). Since this elastic reaction force rapidly increases just before the armature (
5
) is attracted to the drive-side rotation member (
4
), the rapid increase in the elastic reaction force of the second elastic member (
66
) alleviates an impact produced when the armature (
5
) is attracted to the drive-side rotation member (
4
), and effects further reduction in the clutch operating noise.
On the other hand, when the clutch is OFF, namely when the armature (
5
) returns to the original, separate position by a spring force of the leaf spring (
61
), the armature (
5
) collides with the first elastic memb
Denso Corporation
Posz & Bethards, PLC
Rodriguez Saul
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