GB2250567A

GB2250567A - Dual damping device

Info

Publication number: GB2250567A
Application number: GB9026695A
Authority: GB
Inventors: Ronald Harding
Original assignee: Holset Engineering Co Ltd
Current assignee: Cummins Turbo Technologies Ltd
Priority date: 1990-12-07
Filing date: 1990-12-07
Publication date: 1992-06-10
Anticipated expiration: 2010-12-07
Also published as: GB9026695D0; GB2250567B

Abstract

A dual damping device has a hollow cylindrical carrier 1 adapted to fit a rotating shaft. A torsional vibration damper 5 and a bending vibration damper 6 are mounted on the carrier 1. Each damper 5, 6 comprises an annular damping mass 7, 10 attached to the carrier 1 by means of a resilient ring of elastomeric material 9, 11. Various locations for the mass 10 are proposed. <IMAGE>

Description

DUAL DAMPING DEVICE The present invention relates to a dual damping device for damping the vibration of a rotating shaft, for example, a crankshaft in an internal combustion engine.

The vibration of a rotating shaft generally comprises at least two main components: torsional vibration (in a circumferential direction) and bending vibration (in a radial direction). Devices which damp each component of vibration separately are known.

European Patents Nos. 0220871 and 0219341 (Tokai and Toyota) disclose a dual damping device designed to damp both torsional and bending vibration. The damping device is joined to a shaft by a cylindrical hub and features a first damper mass for damping torsional vibration and a second damper mass for damping bending vibration. The first damper mass is disposed radially outwardly of the cylindrical hub and the second damper mass is disposed within the cylindrical hub.

The above described device has two main disadvantages: firstly, the size of the second damper mass is restricted by the space available in the cylindrical hub and, secondly, a retaining member is required to prevent the second damper mass from falling out of the hub.

The restriction in size of the second mass limits the ability to damp large bending vibrations and thus the range of engines on which the device can be used is restricted. The need for the retaining member means that extra components have to be manufactured and fitted.

It is an object of the present invention to obviate or mitigate the aforesaid disadvantages.

According to the present invention there is provided a dual damping device comprising a torsional vibration damper and a bending vibration damper both mounted on a hollow cylindrical carrier adapted to fit onto one end of a rotating shaft characterised in that the dampers are mounted on the outside of the carrier.

Preferably, the dampers each comprise a damper mass in the form of an annulus encircling the carrier and attached thereto by a ring of resilient material.

The resilient material ring of the bending vibration damper may be attached to the radially inner face of the damper mass annulus and have axial holes to improve the damping of bending vibrations.

The carrier may be stepped to provide a relatively small diameter portion for attachment to the shaft and a relatively large diameter portion remote from the shaft. The large diameter portion of the carrier may terminate in an outwardly directed flange with both dampers being mounted on the large diameter portion and the bending vibration damper disposed between the flange and the torsional vibration damper.

The invention will now be further described by way of example only with reference to the accompanying drawings, in which: Figs. 1 to 6 are longitudinal sectional half views of different embodiments of dual damping devices in accordance with the invention, and Figs. la and 4a are cross-sectional scrap views on the section lines of the associated Figures 1 and 4.

Referring now to Fig. 1, a dual damping device comprises a hollow cylindrical carrier 1 having a radial shoulder or step 2 separating a relatively small diameter portion 3 from a relatively large diameter portion 4 of the carrier. The small diameter carrier portion 3 is adapted to be fitted onto one end of a rotating shaft (not shown) e.g. a crankshaft of an internal combustion engine.

Mounted on the outside of the large diameter carrier portion 4 are a torsional vibration damper 5 and a bending vibration damper 6. The torsional vibration damper 5 is considerably larger than the vibration damper 6 and comprises a damper mass 7 in the form of an annulus encircling the carrier portion 4. The radially outer face of the damper mass 7 is provided with two circumferential grooves 8 of V-section for receiving a pulley belt (not shown). The radially inner face of the damper mass 7 is bonded to a resilient ring 9 of elastomeric material e.g. natural or synthetic rubber which is in turn bonded to the carrier portion 4.

The bending vibration damper 6 is of similar construction with a damper mass 10 bonded to a ring 11 of elastomeric material, e.g. natural or synthetic rubber, but in this case the radially inner surface of the resilient ring 11 is bonded to a metal carrier ring 12 which is a compression fit on the carrier portion 4. The bending vibration damper 6 is accommodated in the gap between the torsional vibration damper 5 and a flange 4a on the carrier portion 4. As seen in the cross-sectional view of Fig. la the resilient ring 11 is penetrated by axial holes 13 for reducing the stiffness of the elastomeric material in the radial direction thereby adapting the material to bending as opposed to torsional vibrations.

The natural frequency of each damper 5, 6, which is dependent upon the masses of the damper masses 7, 10 and the spring constants of the resilient rings 9, 11, is predetermined to suit the torsional and bending vibration frequencies of the shaft to which the dual damping device is to be fitted.

Fig. 2 shows a second embodiment of dual damping device in which like parts bear the same reference numerals and are not further described. The large diameter carrier portion 4 has an axial length corresponding to the torsional vibration damper 5 and there is no terminal flange 4a. The bending vibration damper 6 is mounted on the outside of the step 2 of the carrier 1. The annular mass 10 therefore encircles the small diameter carrier portion 3 with substantial clearance and is bonded on its side face to the ring of elastomeric material 11 which is in turn bonded to the step 2.

In the third embodiment illustrated in Fig. 3 the carrier 1 is similar to that of the first embodiment of Fig. 1 with the terminal flange 4a defining a gap with the torsional vibration damper 5 and the bending vibration damper 6 being disposed in this gap. In this case, however, the bending vibration damper 6 is similar in design to that of Fig. 2 with the resilient ring 11 being bonded on the one hand to the side face of the damper mass 10 and on the other hand to the flange 4a of the carrier 1.

In the embodiment of Fig. 4, the carrier 1 is similar to that of Fig.

2 but in this case the bending vibration damper 6 has the Fig. 1 design but is positioned on the small diameter carrier portion 4 adjacent the step 2.

In the embodiment of Fig. 5 the shape of the carrier 1 is similar to that of Fig. 1 but the large diameter portion 4 is abbreviated to bring the flange 4a into close proximity with the torsional vibration damper 5. The carrier portion 4 is extended axially by a ring 14 with a radial flange 14a. The ring 14 is a tight fit in the carrier portion 4 and is so dimensioned and positioned as to provide an annular gap between the flanges 4a and 14a into which the bending vibration damper 6 fits. The bending vibration damper 6 is of the same design as in the Fig. 3 embodiment with the difference that the resilient ring 11 is bonded to the outside of the flange 4a.

In the embodiment of Fig. 6 the carrier 1 is of uniform cylindrical diameter with a circumferential section 15 and an end wall 16 having a central opening 17 enabling the carrier 1 to be fitted to the rotating shaft. The torsional vibration damper 5 has an ungrooved damper mass 7 and is mounted on the outside of the circumferential wall 15 of the carrier 1. The bending vibration damper 6 is of the same design as that of Fig. 3 and is mounted on the outside of the end wall 16 of the carrier 1.

Claims

1. A dual damping device comprising a torsional vibration damper and a bending vibration damper both mounted on a hollow cylindrical carrier adapted to fit onto one end of a rotating shaft characterised in that the dampers are mounted on the outside of the carrier.

2. A device as claimed in claim 1, wherein the dampers each comprise a damper mass in the form of an annulus encircling the carrier and attached thereto by a ring of resilient material.

3. A device as claimed in claim 2, wherein the resilient material ring of the bending vibration damper is attached to the radially inner face of the damper mass annulus and has axial holes to improve the damping of bending vibration.

4. A device as claimed in any one of the preceding claims, wherein the carrier is stepped to provide a relatively small diameter portion for attachment to the shaft and a relatively large diameter portion remote from the shaft.

5. A device as claimed in claim 4, wherein the large diameter portion of the carrier terminates in an outwardly directed flange and both dampers are mounted on the large diameter portion with the bending vibration damper between the flange and the torsional vibration damper.

6. A dual damping device substantially as herein described with reference to the accompanying drawings.