Brakes – Inertia of damping mass dissipates motion – Resiliently supported damping mass
Reexamination Certificate
2000-01-13
2001-10-30
Oberleitner, Robert J. (Department: 3613)
Brakes
Inertia of damping mass dissipates motion
Resiliently supported damping mass
Reexamination Certificate
active
06308810
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a dynamic damper serving as a dynamic vibration absorber, and a method of manufacturing the same. More particularly, the invention is concerned with such a dynamic damper which is to be attached to a rotary shaft, such as a drive shaft of a motor vehicle, for damping or absorbing vibrations of the rotary shaft, and a method of manufacturing the same.
2. Discussion of the Related Art
There is known a dynamic damper, as disclosed in JP-Y2-02-31626 and JP-A-08-28627, for damping vibrations which are applied to a rotary shaft such as a drive shaft of a motor vehicle in an axial direction of the rotary shaft as well as in a direction perpendicular to the axial direction. The dynamic damper includes a matallic mass member which has a generally cylindrical shape, and an elastic support member which is to be mounted on the rotary shaft. The elastic support member elastically supports the metallic mass member with respect to the rotary shaft such that the mass member is displaceable relative to the rotary shaft as the elastic support member is mounted on the rotary shaft. The thus constructed dynamic damper minimizes transmission of the vibrations and noises of the rotary shaft to the other components, and also restrains a stress amplitude of the rotary shaft for thereby effectively preventing fatigue failure of the rotary shaft.
In recent years, there is a demand for further improved efficiency and further reduced cost of manufacture of the dynamic damper. To meet such a demand, there are required some improvements in the construction of the dynamic damper.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a dynamic damper having an improved construction which is easy to manufacture at a reduced cost while assuring a sufficiently high vibration damping effect.
It is a second object of the present invention to provide a method suitable for manufacturing such a dynamic damper.
The above first object may be achieved according to a first aspect of the present invention, which provides a dynamic damper for damping vibration of a rotary shaft, comprising: (a) a mass member having a generally cylindrical shape and formed from a plate having a predetermined contour, the plate being rolled into the generally cylindrical shape and including circumferentially opposite end portions which are opposed to each other in a circumferential direction thereof and which are not fixed to each other; (b) an elastic support member to be mounted on the rotary shaft, for elastically supporting the mass member with respect to the rotary shaft such that the mass member is displaceable relative to the rotary shaft; and (c) balancing means for maintaining a rotary balance of the mass member about an axis of the mass member.
In the conventional dynamic damper, the mass member is, in general, formed by cutting a drawn or otherwise formed metallic pipe, to a suitable length, or alternatively, is a cylindrical metallic member which has been formed by forging or casting or by other suitable methods. A study made by the inventor of the present invention revealed that such a conventional dynamic damper requires a high level of skill and a high cost of manufacture, and that there was still some room for improvement in terms of its manufacturing efficiency and cost. In this view, the inventor attempted to form the mass member by rolling a metal plate, which has been formed by a blanking or other operation, into a cylindrical shape such that circumferentially opposite end portions of the metal plate were circumferentially opposed to each other. The thus constructed mass member can be produced more easily and economically than the conventional mass member. However, it was found that the thus constructed mass member suffered from an imbalance of the mass member, i.e., an uneven distribution of mass in the circumferential direction of the mass member, due to the presence of a circumferential gap between the circumferentially opposite end portions of the metal plate, thereby possibly deteriorating the vibration damping capability of the dynamic damper and also the durability of the elastic support member. It might be possible to eliminate the circumferential gap by welding, bonding or otherwise connecting together the circumferentially opposite end portions of the metal plate. However, such a welding or connection may be another cause of an imbalance of the mass member, requiring a further adjustment of the mass distribution in the mass member.
The present invention has been developed based on the above-described findings. In the dynamic damper constructed according to the present invention, the uneven amass distribution in the mass member is compensated for or corrected by the provision of the balancing means in the dynamic damper, without connecting or fixing the circumferentially opposite end portions of the metal plate to each other even if the circumferentially opposite end portions are circumferentially spaced apart from each other with a circumferential gap therebetween. According to this arrangement, the mass member is formed from the metal plate which is easily and economically produced, while an even mass distribution in the circumferential direction of the mass member is advantageously assured owing to the balancing means, without welding or other cumbersome operation. Thus, the present dynamic damper can be efficiently manufactured at a reduced cost, while assuring a sufficiently high vibration damping effect.
According to a first preferred form of the first aspect of the invention, the circumferentially opposed end portions of the plate are circumferentially spaced apart from each other with a circumferential gap therebetween, and the balancing means cooperates with the circumferential gap to maintain the balance of the mass member about the axis, the balancing means comprising at least one of mass-reducing means for reducing a mass in a circumferentially central portion of the plate which is substantially diametrically opposed to the circumferential gap, and mass-increasing means for increasing a mass in the circumferentially opposite end portions of the plate.
The circumferential gap possibly causes an uneven mass distribution in the mass member, resulting in a rotary imbalance of the mass member about the axis. However, the possible uneven mass distribution is advantageously compensated for by the balancing means. In other words, the balancing means cooperates with the circumferential gap to maintain the rotary balance of the mass member about the axis. The imbalance caused by the weight reduction due to the circumferential gap is advantageously corrected, for example, by reducing the mass of the circumferentially central portion which is substantially diametrically opposed to the circumferential gap, or alternatively by increasing the mass of the circumferentially opposite end portions which are adjacent to the circumferential gap.
According to a second preferred form of the first aspect of the invention, the balancing means comprises mass-reducing means for reducing a mass of at least one local portion of the plate, the at least one local portion being located in a circumferentially central portion of the plate which is substantially diametrically opposed to the circumferentially opposite end portions of the plate.
The mass-reducing means preferably comprises at least one hole formed in the at least one local portion of the plate. The hole may be a blind hole or a through-hole extending in a thickness direction of the plate. Further, the mass-reducing means may comprise a concavity, recess, or means for reducing an axial length of the circumferentially central portion of the plate, in place of or in addition to the hole. The recess may be preferably formed at each of the axially opposite end faces of the circumferentially central portion of the plate so as to extend axially inwardly from the end face. Since the recess defines a part of the outer periphery or contour of th
Burr & Brown
Oberleitner Robert J.
Pezzlo Benjamin A.
Tokai Rubber Industries Ltd.
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