GB2214999A

GB2214999A - Balance weight for rotating body

Info

Publication number: GB2214999A
Application number: GB8803533A
Authority: GB
Inventors: Lionel Roger Phelps; Christopher Graham Ward; Anthony John Curtis
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1988-02-16
Filing date: 1988-02-16
Publication date: 1989-09-13
Also published as: GB8803533D0

Abstract

A balance weight 50 for a rotating body e.g. a clutch cover 4 or a clutch driven plate (30, Fig 9) is made from a polymeric material such as nylon which is filled with a high density material such as iron fillings or lead fillings. The weight 50 is a snap fit in an aperture 41 in the rotating body and can be colour coded according to its mass. Alternatively (Fig 8) the weight is dumbell-shaped and held in position by deformable jaws. <IMAGE>

Description

BALANCED ROTATIONAL BODIES This invention relates to balance weights for rotational bodies and in particular to balance weights which are suitable for use in rotational balancing of friction clutch components.

A typical motor vehicle friction clutch comprises an annular clutch cover assembly, and a driven plate which is clamped between a flywheel connected to the vehicle engine, and a pressure plate forming part of the clutch cover assembly.

Since clutch components are rotating at relatively high speeds with the driven plate connected to the gearbox input shaft, and the clutch cover assembly connected to the f.ly.wheel. mounted..on the engine crankshaft, then the rotating components must be balanced for rotational movement in order to reduce vibrations to a minimum.

Prior art methods of balancing clutch components have included the removal of excess material from the heaviest side of the component, generally by drilling, on flywheels and clutch cover assemblies, or the addition of small counterweights to the lighter side of the component as in the case of a friction clutch driven plate.

The present invention provides a suitable balancing weight for use in the dynamic balancing of rotating bodies.

Accordingly there is provided a balance weight for rotating bodies and which comprises polymeric material loaded with a filler having a relative density of at least 6 and shaped to locate in a prepared aperture in a rotating body.

Preferably the filter is metallic filings or powder.

Preferably the balance weight.. is a snap-fit into the respective aperture.

Where large numbers of balance weights of different weights are provided each balance weight can be assigned a colour according to its weight, so that any balance weight can be readily identified as being of a particular weight or mass.

An annular clutch cover assembly has a radially outwardly projecting flange by which it is attached to a vehicle flywheel, and conveniently the flange has at least one aperture formed therein to accommodate a balance weight of the type described above.

A friction clutch driven plate may also be dynamically balanced by use of the above described balance weight.

Preferably the driven plate is of the type comprising a hub, and a friction facing carrier which is rotatably -mounted on the hub, and a balance weight is secured in an aperture located in the radially outer peripheral margin of the facing carrier.

Also according to this invention there is provided a method of balancing a rotatable clutch component in which method a plurality of equiangularly spaced apertures are formed around the peripheral margin of the component, and metal filled plastic balance weights are secured in the apertures as required to achieve a dynamic balance.

The invention will be described by way of example and with reference to the accompanying drawings in which: FIG 1 is,a cross-section through a typically motor vehicle friction clutch, FIG 2 and FIG 3 are cross-sections through a clutch cover assembly showing a balance weight fitted thereto, FIG 4 illustrates the balance weight'utilised in FIG 2, FIG 5 illustrates the balance weight utilised in FIG 3, FIG 6 is a modified balance weight of the type shown in FIG 5, FIG 7 shows an alternative method of fitting a balance weight to a clutch cover, FIG 8 is a plan view of FIG 7, and FIG 9 is a schematic cross-section of a clutch driven plate showing a balance weight fitted thereto.

With reference to Figures 1 and 2 there is illustrated a friction clutch cover assembly 2, comprising an annular cover 4, a pressure plate 22 located coaxially within the cover 4, and a coaxial diaphragm spring 16 located between the cover and the pressure plate to bias the pressure plate 22 away from the cover 4.

The cover 4 comprises a cylindrical sidewall 5 having a radially outwardly projecting flange 7 at one axial end thereof and a radially inwardly projecting flange 8 at the other axial end. The outwardly projecting flange 7 has a plurality of holes 6 therein whereby the cover is attached by bolts B to flywheel F on the crankshaft of a vehicle engine. The inwardly projecting flange 8 has a plurality of tabs 26 on its radially inner periphery whereby the diaphragm spring 16 is attached to the cover.

The spring 16 is a frustoconical plate spring coned away from the pressure plate 22 and having a radially outer continuous annular portion 17 with a plurality of spaced radially inwardly extending fingers 18 projecting from the radially inner periphery of the annular portion 17.

The spring 16 is attached to the cover 4 by the tabs 26 on the cover, extending through respective apertures 19 at the base of the fingers 18 and being bent around the continuous portion 17 of the spring to clinch the spring to the cover. A pair of coaxial fulcrum rings 24 and 28 are located one on each side of the diaphragm spring and are located against the radially outer surface of the tabs 26 prior to the tabs being bent around the spring 16. The outer margin 17 of the spring 16 acts against the pressure plate 22.

When the cover assembly is mounted on the flywheel F the pressure plate 22 is biased by the spring 16 to clamp a driven plate 30 between itself and the flywheel F. The hub 31 of the driven plate 30 is fitted onto a gearbox input shaft I. To release the driven plate 30 a release load L is applied to the radially inner ends of the spring fingers 18, via a clutch release bearing G, to move the inner ends of the fingers towards the flywheel F, causing the outer annular portion 17 of the spring to pivot about the fulcrum rings 24, 28 and move away from the flywheel F. When the clutch is re-engaged the reverse operation takes place.

The rotatable components of the clutch such as the flywheel F, the cover assembly 2, and the driven plate 30 must be in dynamic balance to minimise vibrations.

Figs 2 and 3 show sections through a clutch cover 4 in which the cover is balanced by the addition of balance weights 40 and 50 to an aperture 41 located in the outwardly projecting cover flange 7. Preferably a plurality of equiangularly spaced holes 41 are formed in raised portions 42 of the flange 7 and which are spaced from the abutment surface on the flywheel F to which the cover is bolted. These balance weights 40 and 50 are a snapifit in their respective covers 4 (Fig 2 and Fig 3) and are placed in their respective holes around the flange as required to achieve dynamic balance of the assembly. The balance weight 40 is illustrated in Fig 4 and the balance weight 50 is shown in Fig 5.

The balance weights 40 and 50 are formed from heavily loaded polymeric materials, preferably plastics materials. It is considered that the weights would be formed from such materials as nylon, polypropylene, high density polyethylene which are heavily loaded with metallic powder such as iron filings, lead filings, etc., so as to achieve a balance weight of the desired mass. A range of different mass weights could be produced by using different percentage loadings of metallic powder in the base polymer from which the weight is formed, or alternatively by using different metallic fillers or base polymers. The balance weights can be moulded with pigmented polymer so that each weight can be assigned a colour according to its mass so that each balance weight is readily identifiable with a particular weight.

The balance weight 40 (Fig 4) is used on th cover of Fig 2 and has a head 45, a shank 46, and detent 47 on the end portion away from the head. The detent 47 has a champfered surface 48 and a slot 49 is formed in the end portion of the shank 46 so that the detent 47 has some resilience so that the balance weight is a snap fit into an aperture 41 in the cover flange 7 with the detent locating against the side of. the flange adjacent the flywheel F.

An alternative balance weight 50 (Fig 5) is a two part weight, the first part 51 is similar to the balance weight 40 excepting only that it has an elongated shank 46B, and the second part is a locking ring 52 which may be of metallic filled or unfilled plastics material dependent upon the desired overall mass of the balance weight. As can be seen in Fig. 3, the elongated shank 46B is necessary to accommodate the locking ring 52.

Fig. 6 illustrated amodified two part balance weight 60 which is similar to that of Fig. 5 excepting that there is no slot 49 in the end portion of the shank 46 and therefore the first part 61 of the weight must be of a more resilient material,and the locking ring 62 has internal flutes 63 for engagement with the detent 47.

In Fig. 7 and Fig. 8 there is illustrated a different balancing weight 70 which is dumbell shaped. The shank 72 interconnecting the two heads 73 of the weight is located in a radial slot 74 extending radially inwardly from the peripheral edge of the flange 7. The mouth 75 of the slot has a pair of jaws 76 which can be deformed to retain the balance weight in the slot.

With reference to Fig. 9 there is illustrated a clutch driven plate 30 having a hub 31 with an annular flange 32 thereon. A coaxial friction facing carrier 33 is mounted on the hub 31 for limited rotational movement thereto which is restrained by springs 34 in a well known manner.

The friction facing carrier 33 may comprise an annular carrier plate 35 located on one axial side of the hub flange 32 and a retainer plate 36 located on the other side of the hub flange and which is secured to the carrier plate by stops pins (not shown) in a known manner.

The radially outer margin of the facing carrier 33, and preferably the outer margin of the retainer plate 36 has a plurality of equiangularly spaced holes 37 therein.

The holes 40 can each accommodate a balance weight 40 of the type described with reference to Fig. 4. The balance weight or weights are located in the respective holes 37 as required to achieve a dynamic balance for rotational movement of the driven plate 31.

The balance weight540 and 50 have the advantage that they can be tit. ted to components in which it is not possible to insert a clinching tool for conventional rivet weights or there is not sufficient space for attachment using 'pop' (reg. Trade Mark) rivets. This situation is most relevant to clutch driven plates.

Claims

CLAIMS:

1. A balance weight for rotating bodies and which comprises polymeric material loaded with a filler having a relative density of at least 6 and shaped to locate in a prepared aperture in a rotating body.

2. A balance weight as claimed in claim 1 wherein the weight is a snap-fit in said aperture.

3. A balance weight as claimed in claim 1 wherein the balance weight comprises two parts, a first part which locates in said aperture, and a second part into which the first is a resilient snap,-fit to secure the first part to a rotating body.

4. A balance weight as claimed in any one of claims 1 to 3.

wherein the balance weight is assigned a colour according to its weight, said balance weight .therefore being identifiable with a particular weight.

5. A motor vehicle friction clutch in which at least one rotary component thereof is balanced for rotation by use of a balance weight as claimed in any one of claims 1 to 3.

6. An annular clutch cover- assembly including an annular clutch cover with a radially outwardly projecting flange at one axial end thereof for attachment to a flywheel, wherein said flange has at least one aperture therein to accommodate a balance weight according to any one of claims 1 to 3.

7. An annular clutch cover assembly as claimed in claim 6, when dependent upon claim 1, wherein said aperture is a slot extending radially inwardly from the outer peripheral edge of the flange on a portion thereof raised away from an abutment surface on a flywheel to which the cover is intended to be fitted and the balance weight is secured thereon by deformation, of the radially outer end of said slot.

8. An annular clutch cover assembly as claimed in claim 6 when dependent upon claim 3, wherein said aperture is a circular hole on a portion of the flange raised away from an abutment surface on a flywheel to which the cover is intended to be fitted and said first part of the balance weight comprises a head and a shank, with a detent on its end portion away from th head, the detent being engageable with said second part such that the head is located on one side of the raised portion of the flange and the second part is locked in position on the other side of the flange by the detent.

9. An annular clutch cover assembly as claimed in claim 8 wherein the detent is an outwardly projecting flange on the shank which is engageable with the second part which is in the form of a ring through which the detent is passed.

10. An annular clutch cover assembly as claimed in any one of claims 6 to 9, wherein the clutch cover flange has a plurality of equiangularty spaced apertures in the periphery thereof which are each suitable for accommodating a balance weight, and balance weights are located in said holes as is required for rotational balance of the cover assembly.

11. A friction clutch driven plate which is balanced for rotation by at 'least one balance weight as claimed in any one of claims 1 to -4.

12. A friction clutch driven plate e as claimed in claim 11 when dependent upon claim 2, wherein the driven plate comprises a hub having a coaxial annular friction facing carrier rotatably mounted thereon, and at least one balance weight is secured in an aperture located in the radially outer peripheral margin of the facing carrier.

13. A friction clutch driven plate as claimed in claim 12 wherein the hub has an annular flange thereon, and the friction facing carrier comprises a coaxial annular carrier plate located on one axial side of the hub flange, and a retainer plate located on the other axial side of the hub flange, and said balance weight is located in an aperture in the outer peripheral margin of the retainer plate.

14. A friction clutc-h driven plate as claimed in claim 13 wherein the retainer plate has a plurality of equiangularly spaced annular holes therein each of which is suitable for accommodation of a balance weight, and balance weights are located in said holes as is required for rotational balance of the cover assembly.

15. A method of balancing rotatable clutch components in which method a plurality of equiangularly spaced apertures are formed around the peripheral margin of the component, and metal filled plastic balance weights are secured in the apertures as required to achieve a dynamic balance.