GB2111169A

GB2111169A - Torsional vibration dampers

Info

Publication number: GB2111169A
Application number: GB08233040A
Authority: GB
Inventors: Peter Pfeifer
Original assignee: Dr Ing Geislinger und Co Schwingungstechnik GmbH
Current assignee: Dr Ing Geislinger und Co Schwingungstechnik GmbH
Priority date: 1981-12-04
Filing date: 1982-11-19
Publication date: 1983-06-29
Also published as: FR2517780B1; JPS58102841A; DE3238572A1; AT371578B; CH657195A5; FR2517780A1; ATA520081A; GB2111169B

Abstract

A torsional vibration damper for drive means having rotary unbalance e.g. crankshaft drives comprises an inner member 1, which is adapted to be non-rotatably connected to the drive means, and an outer member 3, 5,8, which constitutes the damping mass and is coupled to the inner member by resilient and/or viscous means 4. In order to minimize the additional expenditure for counterweights and to eliminate the moment of inertia which is due to the mass of counterweights, the center of gravity of the outer member is eccentric with respect to the axis of rotation of the outer member. This may be achieved by the end plate 8 having a thicker portion 8' which extends along only part of its periphery. Alternatively the spacers 5 on one side of the axis may have bores. The outer member may instead be composed of materials with different specific gravities. <IMAGE>

Description

SPECIFICATION Torsional vibration damper This invention relates to a torsional vibration damper for drive means having rotary unbalance, particularly crankshaft drives, comprising an inner member, which is adapted to be non-rotatably connected to the drive means, and an outer member, which constitutes the damping mass and is coupled to said inner member by resilient or viscous means.

Internal combustion engines and all other rotary systems which have rotary unbalance must be provided with counterweights for compensating the forces and torques which are due to rotary unbalance. These counterweights consist, e.g., of segments of circular rings and are secured to a free shaft end, e.g., to a suitable flange of the crankshaft. The compensating action always depends on the product of mass times center of gravity radius rather than on the geometric configuration. But such a counterweight involves a secondary effect, which is undesirable in most cases and resides in that the moment of inertia which is due to the mass of the counterweight increases the total amount of inertia of the drive mechanism and reduces its natural frequency.

In addition to that mass compensation, means are required in most cases for limiting the alternating torsional stresses of the crankshafts or drive shafts. This can be effected by a torsional vibration damper. Experience has shown that the damping action increases with the magnitude of the damping means, which is coupled by resilient and/or viscous means. As the damper requires space too, a provision of a damper and of counterweights often involves difficulties regarding space and layout.

For this reason it is an object of the invention to avoid these disadvantages and to provide a torsional vibration damper which is of the kind described first hereinbefore and in which the additional expenditure and space requirement which were due to the counterweights and the torsional vibration damper are minimized and the undesired moment of inertia which was due to the mass of the counterweights is eliminated.

This object is accomplished according to the invention is that the center of gravity of the outer member is eccentric with respect to the axis of rotation of the outer member. Because the mass of the outer member is eccentric, it acts as a combination of a damping mass and compensating mass so that the counterweight can be arranged in the damper itself and the moment of inertia which is due to the mass of the counterweight is available as an effective damping mass and is not effective as a rather disturbing mass moment of inertia. As the damper constitutes also a counterweight, the structural expenditure is reduced, the space problem is solved and the assembling is facilitated because it is sufficient to secure a damper rather than a damper and a counterweight.Various meaures can be adopted to ensure that the outer member has an eccentric center of gravity so that it constitutes a counterweight and these measures may be adapted to the conditions of each case.

For instance, the outer member may be asymmetrical with respect to its axis of rotation, e.g., in that it is formed with unilaterally disposed portions which are of larger thickness or with unilaterally disposed flats, cavities or bores.

Additional weights of suitable shape may be mounted on the outer member in suitable positions or the outer member may be composed of elements consisting of materials having different specific gravities.

An illustrative embodiment of the invention is diagrammatically shown in the drawing, in which Figure 1 is an end view showing partly in section one half of a torsional vibration damper according to the invention and Figure 2 is a transverse sectional view showing that rotary vibration damper.

The inner member 1 of the rotary vibration damper is screw-connected with the aid of bores 2 to a flange of a shaft, which is not shown and consists, e.g., of a crankshaft. During a rotation of the shaft, the inner member cooperates with the outer member, which constitutes the damping mass. The outer member 3 is coupled to the inner member 1 by means of radial leaf springs 4 and in addition to said spring leaves 4 comprises spacers 5, by which the spring leaves are gripped, a stressing ring 6 for holding the spring leaves 4 and spacers 5 together, and two end plates 7, 8.

In order to provide not only a damping of vibrations but also a mass compensation for the crankshaft or another drive member which has rotary unbalance, the outer member 3 is so designed that its center of gravity is eccentric with respect to its axis of rotation. This can be accomplished in various ways, e.g., in that the spacers 5 are provided with unilaterally disposed bores, or, as in the illustrative embodiment shown, in that the end plate 8 has a thicker portion 8' which extends along part of its periphery. It will be understood that the mass compensating action can be increased in that bores as well as the thicker portion 8r are provided. Because an eccentric center of gravity can be provided in numerous ways, the invention is not restricted to a specific measure adopted to provide an outer member which constitutes also a counterweight, but includes all ways by which this can be achieved.

As the damping mass is eccentric, the torsional vibration damper acts also as a counterweight for a mass compensation of drive means having rotary unbalance. This eliminates the need for separate counterweights and provides a solution to the problem regarding the arrangement of a damper as well as a counterweight. Besides, the structural expenditure is correspondingly reduced, the disturbing secondary effects of counterweights associated with the drive are eliminated and the assembling is simplified.

Claims

Claim

1. A torsional vibration damper for drive means having rotary unbalance, particularly crankshaft drive means, comprising an inner member, which is adapted to be non-rotatably connected to the drive means, and an outer member, which is coupled to said inner member by resilient or viscous means and constitutes the damping mass, characterized in that the center of gravity of the outer member is eccentric with respect to the axis of rotation of the outer member.