GB1597184A

GB1597184A - Torsional oscillation damping flywheel for rotary shafts such as crank shafts of reciprocating engines

Info

Publication number: GB1597184A
Application number: GB1846978A
Authority: GB
Original assignee: Fiat Veicoli Industriali SpA; Societa Applicazioni Gomma Antivibranti SAGA SpA
Current assignee: Fiat Veicoli Industriali SpA; Societa Applicazioni Gomma Antivibranti SAGA SpA
Priority date: 1977-06-28
Filing date: 1978-05-09
Publication date: 1981-09-03
Also published as: FR2396211B1; IT1083366B; DE7816637U1; DE2824331A1; FR2396211A1

Description

(54) TORSIONAL OSCILLATION DAMPING FLYWHEEL FOR ROTARY SHAFTS, SUCH AS CRANKSHAFTS OF RECIPROCATING ENGINES (71) We, FIAT VEICOLI INDUSTRIALI S.p.A., an Italian joint stock company, of Via Puglia 35, Turin, Italy, and S.A.G.A.

Societa' Applicazione Gomma Antivibranti S.p.A., an Italian joint stock company, of Via Ripamonti 88, Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and bv the following statement The present invention relates to flywheels for damping torsional oscillations of rotary shafts, such as crankshafts for reciprocating engines.

The invention has particular reference to a vibration-damping flywheel of the type including an inertial mass formed by an annular plate having in axial cross section a radially elongate form, a layer of elastomeric material having an L-shape in its sais axial cross section and arranged in such a way as to line a radially inwardly facing inner surface and at least a part of a lateral face of the inertial mass, and a drive transmitting plate a part of which has an L-shape in said axial cross section, and is fixed to the elastomeric layer in a position opposite to the inertial mass, the drive transmitting plate being adapted to be coupled to a rotary shaft.

Such a flywheel will be referred to herein as "a damper flywheel of the type defined".

Vibration damping flywheels of the type defined are known for example from U.K.

Patent Specification No. 828,354. A problem which arises with such flywheels is that of affording a high capacity for damping torsional oscillations, with consequent dissipation as heat of the elastic energy of oscillation, with a considerable capacity for dispersal of this heat and a relative simplicity of construction and assembly. In damper flywheels of the type defined the inertial mass is formed by a ring having a rectangular shape in axial cross section.

An inertial mass connected to a driving shaft by means of an elastomeric layer generally has various vibratory modes among which two modes are the most significant in their effects on the driving shaft: these vibratory modes are respectively a torsional vibration, comprising a rotational oscillation around the axis of rotation and oscillation of the shaft, and a transverse vibration comprising a reciprocating displacement in a direction perpendicular to the aforesaid axis.

The inertial mass in the prior art referred to has a particularly simple rectangular cross-sectional shape, but has the disadvantage that the actual frequencies of the two aforesaid vibratory modes are normally very near one another. This gives rise to a somewhat complex resultant vibration of the mass with a consequent non-uniformstrain distribution in the elastomeric layer which is asymmetrical with respect to the axis of rotation. This in turn gives rise to a significant and non-uniform generation of heat, with consequent rapid deterioration in the elastic properties of the elastomer itself.

The object of the present invention is to provide a vibration-damping flywheel which, although of relatively simple construction and assembly, does not suffer from the aforesaid disadvantage.

According to the present invention, there is provided a damper flywheel of the type defined wherein the inertial mass is formed by a radially outer enlarged annular part and by a relatively thin annular Shaped flange part formed, in axial cross section, by a first portion projecting radially inwardly from said enlarged annular outer part and a second axially projecting portion, said elastomeric layer being interposed between the Shaped part of said drive transmitting plate and said annular flange and fixed to the facing surfaces of said plate and of said flange part.

The inertial mass in the flywheel of the present invention is formed by two parts of which the outer, enlarged one performs the true and proper function of an inertial mass whilst the inner one, formed by the relatively thin flange, serves only to attach the outer inertial mass to the elastomeric layer. By concentrating of the inertial mass in a radially outer zone the flywheel produces for a given overall mass an increase in the polar moment of inertia of the mass with respect to the axis of rotation of the damper flywheel.

Such increase will be accompanied by a corresponding decrease in the frequency of the said torsional vibration mode whilst the frequency of the transverse vibration mode, being dependent solely upon the actual magnitude of the inertial mass, remains substantially unaltered. In this way it is possible to separate the frequencies of these vibration modes sufficiently, that is, to decouple the two vibratory modes, so as to avoid undesirable resultant vibrations and their consequent non-uniform strain distributions. Having regard to the fact that the polar moment of inertia of a flywheel varies with the fourth power of its radial dimensions, it follows that for a flywheel having a given polar moment of inertia the flywheel of the present invention has an inertial mass which is significantly lower than that of known flywheels of the type defined.

Moreover the configuration of the inertial mass in the flywheel of the present invention is such as to permit a more effective heat exchange with the surrounding air than is possible when using an inertial mass of traditional form. This is due both to the relatively high lateral surface area in contact with the air, and to the reduced thickness of material in the flange part of the flywheel which is bonded to the elastomeric layer, so that heat has to traverse a smaller distance before coming into contact with the air.

The invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a vibrationdamping flywheel according to one embodiment of the present invention; Figure 2 is an axial cross-section, on an enlarged scale, taken on line II--II of Figure 1, and Figures 3 and 4 are fragmentary crosssectional views illustrating variants of the flywheel shown in Figure 2.

Reference numeral 1 indicates a vibrationdamping flywheel for attachment to a crankshaft of a reciprocating engine. The flywheel 1 includes a drive transmitting plate 2 having an L-shape in its axial cross section and provided with an internal annular flange 2a.

Holes 3 are formed in flange 2a for receiving fixing bolts which serve to clamp the plate 2 to the crankshaft.

A layer 4 of elastomeric material, also of L-shape in its axial cross section, is fixed to one face of the drive transmitting plate 2 by means of a vulcanising process. On the face of the elastomeric layer 4 opposite the plate 2 an inertial mass 5 is attached, also by means of a vulcanising process.

The mass 5 is formed by a radially outer enlarged annular part Sa of rectangular axial cross section and by a radially inwardly projecting flange Sb. The enlarged part Sa of the mass 5 has an internal surface 9 and two lateral end faces 10 and 11. The flange 5b has a surface which is a continuation of the lateral face 10 of the enlarged part 5a, which is bonded to the elastomeric layer 4.

The flange Sb includes a main portion 14 extending radially inwards and terminating at its radially inner end in an axially projecting lip 12.

In the variants of Figures 3 and 4 components common to the embodiment of Figure 2 are indicated by the same reference numerals as those used in Figure 2.

In the variant of Figure 3 the shape of the inertial mass 5 is substantially the same as that illustrated in Figure 2 and differs from the latter only in that the enlarged annular part Sa has been further displaced radially outwards. In the variant of Figure 4, the enlarged annular part 5a is disposed on the opposite side of the main portion 14 of the flange Sb from the lip 12. Thus the flange 5b in the Figure 4 variant is on a radial continuation of the lateral end face 11 of the enlarged part 5a which is remote from the elastomeric layer 4, the surface 11 facing in the same direction as the axially projecting lip 12 of the flange 5b.

WHAT WE CLAIM IS: 1. A damper flywheel for use in damping torsional oscillations in a crankshaft of a reciprocating engine, including an inertial mass formed by an annular plate having in axial cross section a radially elongated form, a layer of elastomeric material having an L-shape in its said axial cross section and arranged in such a way as to line a radially inwardly facing inner surface and at least a part of a lateral face of the inertial mass, a drive transmitting plate a part of which has an L-shape in said axial cross section and is fixed to the elastomeric layer in a position opposite to the inertial mass, the drive transmitting plate being adapted to be coupled to the shaft, wherein the inertial mass is formed by a radially outer enlarged annular part and by a relatively thin annular L-shaped flange part formed, in axial cross section, by a first portion projecting radially inwardly from said enlarged annular outer part and a second axially projecting portion, said elastomeric layer being interposed between the L-shaped part of said drive transmitting plate and said annular flange and fixed to the facing surfaces of said plate and of said flange part.

2. A flywheel according to claim 1, in which the enlarged annular part has a radially inwardly facing inner surface bounded by two lateral end faces and in which the annular flange part extends radially inwardly from

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. outer zone the flywheel produces for a given overall mass an increase in the polar moment of inertia of the mass with respect to the axis of rotation of the damper flywheel. Such increase will be accompanied by a corresponding decrease in the frequency of the said torsional vibration mode whilst the frequency of the transverse vibration mode, being dependent solely upon the actual magnitude of the inertial mass, remains substantially unaltered. In this way it is possible to separate the frequencies of these vibration modes sufficiently, that is, to decouple the two vibratory modes, so as to avoid undesirable resultant vibrations and their consequent non-uniform strain distributions. Having regard to the fact that the polar moment of inertia of a flywheel varies with the fourth power of its radial dimensions, it follows that for a flywheel having a given polar moment of inertia the flywheel of the present invention has an inertial mass which is significantly lower than that of known flywheels of the type defined. Moreover the configuration of the inertial mass in the flywheel of the present invention is such as to permit a more effective heat exchange with the surrounding air than is possible when using an inertial mass of traditional form. This is due both to the relatively high lateral surface area in contact with the air, and to the reduced thickness of material in the flange part of the flywheel which is bonded to the elastomeric layer, so that heat has to traverse a smaller distance before coming into contact with the air. The invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a vibrationdamping flywheel according to one embodiment of the present invention; Figure 2 is an axial cross-section, on an enlarged scale, taken on line II--II of Figure 1, and Figures 3 and 4 are fragmentary crosssectional views illustrating variants of the flywheel shown in Figure 2. Reference numeral 1 indicates a vibrationdamping flywheel for attachment to a crankshaft of a reciprocating engine. The flywheel 1 includes a drive transmitting plate 2 having an L-shape in its axial cross section and provided with an internal annular flange 2a. Holes 3 are formed in flange 2a for receiving fixing bolts which serve to clamp the plate 2 to the crankshaft. A layer 4 of elastomeric material, also of L-shape in its axial cross section, is fixed to one face of the drive transmitting plate 2 by means of a vulcanising process. On the face of the elastomeric layer 4 opposite the plate 2 an inertial mass 5 is attached, also by means of a vulcanising process. The mass 5 is formed by a radially outer enlarged annular part Sa of rectangular axial cross section and by a radially inwardly projecting flange Sb. The enlarged part Sa of the mass 5 has an internal surface 9 and two lateral end faces 10 and 11. The flange 5b has a surface which is a continuation of the lateral face 10 of the enlarged part 5a, which is bonded to the elastomeric layer 4. The flange Sb includes a main portion 14 extending radially inwards and terminating at its radially inner end in an axially projecting lip 12. In the variants of Figures 3 and 4 components common to the embodiment of Figure 2 are indicated by the same reference numerals as those used in Figure 2. In the variant of Figure 3 the shape of the inertial mass 5 is substantially the same as that illustrated in Figure 2 and differs from the latter only in that the enlarged annular part Sa has been further displaced radially outwards. In the variant of Figure 4, the enlarged annular part 5a is disposed on the opposite side of the main portion 14 of the flange Sb from the lip 12. Thus the flange 5b in the Figure 4 variant is on a radial continuation of the lateral end face 11 of the enlarged part 5a which is remote from the elastomeric layer 4, the surface 11 facing in the same direction as the axially projecting lip 12 of the flange 5b. WHAT WE CLAIM IS:

1. A damper flywheel for use in damping torsional oscillations in a crankshaft of a reciprocating engine, including an inertial mass formed by an annular plate having in axial cross section a radially elongated form, a layer of elastomeric material having an L-shape in its said axial cross section and arranged in such a way as to line a radially inwardly facing inner surface and at least a part of a lateral face of the inertial mass, a drive transmitting plate a part of which has an L-shape in said axial cross section and is fixed to the elastomeric layer in a position opposite to the inertial mass, the drive transmitting plate being adapted to be coupled to the shaft, wherein the inertial mass is formed by a radially outer enlarged annular part and by a relatively thin annular L-shaped flange part formed, in axial cross section, by a first portion projecting radially inwardly from said enlarged annular outer part and a second axially projecting portion, said elastomeric layer being interposed between the L-shaped part of said drive transmitting plate and said annular flange and fixed to the facing surfaces of said plate and of said flange part.

the inner surface of the enlarged annular part, the flange part having one face which is a continuation of one of the two lateral end faces of the said enlarged annular part.

3. A flywheel according to claim 2, in which the annular flange part extends radially inwardly from the inner surface of the enlarged annular part, and has one face which is a continuation of the end face of said enlarged annular part which faces towards the drive transmitting plate.

4. A flywheel according to claim 2, in which the annular flange part extends radially inwardly from the inner surface of the enlarged annular part and has one face which is a continuation of the end face of said enlarged annular part which is remote from the drive transmitting plate.

5. A damper flywheel substantially as herein described with reference to and as shown in Figures 1 and 2, Figure 3 or Figure 4 of the accompanying srawings.