GB2340554A

GB2340554A - Flywheel damper support

Info

Publication number: GB2340554A
Application number: GB9917720A
Authority: GB
Inventors: Hiroyki Ichikawa; Takahiro Koremoto
Original assignee: NTN Corp; NTN Toyo Bearing Co Ltd
Current assignee: NTN Corp
Priority date: 1998-08-07
Filing date: 1999-07-28
Publication date: 2000-02-23
Anticipated expiration: 2019-07-28
Also published as: FR2782134B1; GB9917720D0; FR2782134A1; JP2000055132A; GB2340554B

Abstract

A flywheel damper support structure includes a rolling bearing (6) interposed between an engine-side mass (2) and a transmission-side mass (3) of the flywheel damper for supporting the masses. The rolling bearing (6) has a grease filled therein, which grease contain urea as a thickening agent. Inner and outer races (11, 12) of the rolling bearing (6) is made of steel as a raw material, contains a retained austenite in a quantity not greater than 8% and has a hardness not lower than HRC 60. The amount of the grease filled is chosen to be within the range of 40 to 50% of an inner space of the rolling bearing (6). The grease is of a kind prepared from a synthetic oil as a base oil and containing an aromatic urea used as the thickening agent. Seals (15) are made of a fluorine-contained rubber.

Description

2340554 Flywheel Damper Support The present invention relates to a support

structure for a flywheel damper of a type wherein a rolling bearing is utilized to support the flywheel damper in an automotive engine.

lhe flywheel damper is of a structure in which the flywheel is divided into engine-side and transmission-side masses with a compres sion spring and an attenuator mechanism interposed between these engine side and transmission side masses to allow the flywheel itself to define a damper structure effective to attenuate vibratory noises associated with torsinal vibration of the drive shaft system.

The rolling bearing supporting both of the engine-side mass and the transmission-side mass of the flywheel damper is frequently utilized under a severe condition in which vibrations transmitted from the automotive engine is transmitted accompanied by rocking motion of inner and outer races of the rolling bearing incident to follow-up rotation thereof and is therefore, susceptible to fretting wear.

With the advent of the age of high-performance engine equipped automobiles and compactization of that engine, the environment in which bearings are utilized is getting severe and the bearing for the support of the flywheel damper has come to be developed on the assumption that it will be used under a high temperature condition of, for example, 1509C and p,-ulicularly 20TC. - Increase of the temperature under which the rolling bearing for the support of the flywheel damper is expected to be used brings about such a concern that the fretting wear would more often occur in the rolling -<I>- bearing as a result of change in dimension of the rolling bearing, reduction in hardness of the inner and outer races and decrease of the lubricating performance brought about by thermal degradation of a grease. Another concern is that the rolling bearing for the support of the flywheel damper 5 would be susceptible to decrease of the lifetime thereof due to seizure. Accordingly, countermeasures to alleviate those concerns have now been focused. A countermeasure to alleviate any possible leakage of the grease which would be brought about by change in dimension of seals having been affected by high temperature is also required.

Accordingly, an essential ob ect of the present invention is to provide an improved support structure for the support of the flywheel damper, in which the possibilities of change in dimension and hardness of the bearing races under the high-temperature environment are minimized, in which the thermal resistance of the grease is increased and which is excellent in resistance to fretting and is therefore durable.

Another important object of the present invention is to provide an improved support structure for the support of the flywheel damper of the type discussed above, wherein the lubricating performance exhibited by the grease is improved to thereby increase the resistance to fretting and the resistance to seizure.

A ftuther important object of the present invention is to provide an improved support structure for the support of the flywheel damper of the type discussed above, wherein any possible leakage of the grease under the high-temperature environment which would otherwise brought about by decrease of the thermal resistance of the seals and the resistance to compressive permanent deformation is minimized.

In order to accomplish these objects of the present invention, there is provided a flywheel damper support structure for the support of a -<2>flywheel damper which is interposed between an automotive engine and a transmission. The support structure comprises a rolling bearing interposed between an engine-side mass and a transmission-side mass of the flywheel damper for supporting the masses, including inner and outer race members.

The rolling bearing is filled with a grease containing urea as a thickening agent. At least one of the inner and outer race members which is fitted to the engine-side mass is made of steel as a raw material and contains a retainer austenite in a quantity not greater than 8% and has a hardness not lower than HRC 60. At least one of the inner and outer race members which is made of the above described raw material may be any of the inner and outer races or the both.

Although if the quantity of the retained austenite in the bearing raceway member is increased, a desirable effect can be obtained in that the hardness can be increased to prevent wear, the dimensional stability tends to be lowered with passage of time when the use is made under the high-temperature environment such as occurring in the modem engine. On the other hand, in view of the advance in steel manufacturing technology, it is possible to secure the hardness not lower than HRC 60 that is required to assuredly prevent any possible fretting wear even though the quantity of the retained austenite is not greater than 8%. Accordingly, the present invention is featured in that while the quantity of the retained austenite is chosen within a range effective to secure the necessary hardness and, also, the dimensional stability under the high- temperature environment (It is to be noted that the term "high- temperature environ- ment" herein used is intended to means the environment of a temperature not lower than 1509C.) with passage of time is secured, any possible occurrence of the fretting wear which would result from an excessive gap is prevented. The fretting wear referred to hereinbefore tends to easily occur particularly in one of the raceway members which is fitted to the engine- side mass and, therefore, if the material and the hardness of the raceway member fitted to at least the engine-side mass are selected such as hereinabove described, the fretting wear in both of the raceway members can be prevented. Also, if the grease containing urea as the thickening agent is employed, the heat resistance of the grease can be obtained, thereby improving the resistance to fretting wear further.

In the practice of the present invention, the amount of the grease filled is preferably within the range of 40 to 50% relative to an inner space of the rolling bearing.

While the amount of the grease filled is generally considered within the range of 25 to 30%, by increasing this amount of the grease filled, the lubricant property can be improved accompanied by improvement of the resistance to fretting -and, also, the resistance to seizure.

Also, in the practice of the present invention, the grease is preferably of a kind prepared from a synthetic oil as a base oil and contains an aromatic urea as a thickening agent.

The synthetic oil is excellent in resistance to fretting and also heat resistance. In particular, of the various urea, the aromatic urea exhibits an excellent heat resistance. For this reason, if the grease of a kind wherein the base oil comprises a synthetic oil and the urea for the thickening agent is employed in the form of the aromatic urea, the heat resistance of the grease can further be improved with the consequence that the resistance to fretting and the resistance to seizure of the raceway members can be improved.

Furthermore, in the practice of the present invention, the rolling bearing is preferably sealed by seals made of fluorine-contained rubber.

-<4>- Ibe fluorine-contained rubber has an excellent heat resistance and an excellent resistance to compressive permanent deformation and, therefore, the use of the seals made of the fluorine-contained rubber is effective to minimize any possible change in diameter of the seals and hence to improve the sealability. For this reason, any possible occurrence of fretting which would result from reduction in lubricating property brought about by a leakage of the grease can advantageously be prevented.

Again, in the practice of the present invention, the engineside mass and the transmission-side mass are preferably opposed to each other in an axial direction and, also, the inner race member of the rolling bearing is preferably mounted on an outer diametric surface of an inner peripheral portion of the engine-side mass that protrude in one axial direction and the outer race member of the rolling bearing is mounted on an inner diametric surface of an inner peripheral portion of the transmission- side mass that protrude in an axial direction counter to such one axial direction.

In any event, the present invention will become more clearly understood from the following description of a preferred embodiment thereof, when taken in conjunction with the accompanying drawings. However, the embodiments and the drawings are given only for the purpose of illustration and explanation, and are not to be taken as limiting the scope of the present invention in any way whatsoever, which scope is to be determined by the appended claims. In the accompanying drawings, like reference numerals are used to denote like parts throughout the several views, and:

Fig. 1A is a longitudinal sectional view of a support structure for the support of a flywheel damper according to a preferred embodiment of the present invention; -<5>- Fig. I B is a transverse sectional view, on an enlarged scale, of a bearing used in the flywheel damper support structure shown in Fig. I A; and Fig. 2 is a front elevational view, with a portion cut away, of the flywheel damper support structure as viewed in a direction shown by the arrow II in Fig. 1 A.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, particularly to Figs. 1 A to 2. It is, however, to be noted that the upper half of the drawing of Fig. I A represents a cross-section taken along the line A-0 in Fig. 2 while the lower half of the drawing of Fig. 1A represents a crosssection taken along the line B-0 in Fig. 2.

A support structure for a flywheel damper shown therein is of a type in which as shown in Fig. 1 A. A flywheel 1 is divided into engine-side and transmission-side masses 2 and 3 axially opposed to each other with a compression spring 4 and an attenuator mechanism 5 interposed between these engine-side and transmission side masses 2 and 3 to allow the flywheel 1 itself to define a damper structure. The engine- side and transmission-side masses 2 and 3 are supported by a bearing 6 which is interposed between the masses and employed in the form of, for example, a rolling bearing so as to facilitate damping.

An output torque from an automobile engine is transmitted to the engineside mass 2 through a crankshaft CR which is an engine output shaft and is coupled directly with the engine-side mass 2. This output torque is then transmitted from the engine-side mass 2 to an input shaft (not shown) of an automobile transmission (also not shown) through the compression spring 4, then through the attenuator mechanism 5 and finally through the transmission-side mass 3. In this design, depending on -<6>- the magnitude of the engine output torque, flexing of the compression spring 4 and actuation of the attenuator mechanism 5 occur, and since under this condition the compression spring 4 and the attenuator mechanism 5 cooperate with each other to absorb variation of the engine output torque, the transmission-side mass 3 can rotate relative to the engine-side mass 3 at a varying rate which has been attenuated.

The attenuator mechanism 5 comprises, as shown in Fig. 2, an oil chamber 5a, and the transmission of rotation taking place between the engine-side and transmission-side masses 2 and 3 through the compression spring 4 and the attenuator mechanism 5 takes place through a driven plate 7. The driven plate 7 is coupled with the transmission-side mass 3 by means of serrations 8 formed in an inner peripheral surface of the driven plate 7. Stoppers 9 are formed on the engine-side mass 2 in correspondence with projections 7a formed on an outer peripheral surface of the driven plate 7.

The bearing 6 comprises a sealed deep-groove ball bearing as shown in Fig. 1 B and includes an inner race 11, an outer race 12, a plurality of rolling elements 14 in the form of steel balls rollingly retained by a retainer 13 and interposed between the inner and outer races 11 and 12, and seals 15 fitted to respective opposite ends of the bearing 6 so as to straddle between the inner and outer races 11 and 12 so as to seal an annular bearing gap defined between the inner and outer races 11 and 12. Each of the seals 15 is of a unitary structure including a wire core 15a embedded in a portion of a rubber body 15b except for inner and outer peripheral regions whereof which serve as respective inner and outer peripheral lip regions 15c. Each of the seals 15 is secured to the bearing 6 with the outer peripheral lip region 15c engaged in a seal mounting groove 16 defined in an inner peripheral surface of the outer race 12 while the inner peripheral lip region 15c is slidingly engaged in a seal mounting groove 17 defined in an outer peripheral surface of the inner race 13.

Mounting of the bearing 6 to the engine-side and transmission-side masses 2 and 3 is carried out in the following manner. The inner race I I is mounted on and engaged in an outer peripheral surface of a cylindrical portion 2a that is formed in an inner diametric portion of the engine-side mass 2 so as to extend in a first axial direction as shown in Fig. IA, and is retained in position by a stop ring 18. The outer race 12 is mounted on and engaged in an inner peripheral surface of a cylindrical portion 3a that is formed in an inner diametric portion of the transmissionside mass 3 so as to extend in a second axial direction counter to the first axial direction, and is retained in position by a stop ring 19 engaged in a retainer groove formed in this inner peripheral surface of the cylindrical portion 3a.

The bearing 6 is of a structure substantially identical with that disclosed in the Japanese Patent Examined Publication No. 6-33441, published May 2, 1994. More specifically, the inner race 11 of the bearing 6 which is a raceway member fitted to the engine-side mass 2 and the outer race 12 of the bearing 6 which is a raceway member fitted to the transmission-side mass 3 are made of the following material. Each of the inner and outer races I I and 12 is made of steel as a raw materiall which steel contains carbon in a quantity of 0.95 to 1. 10 welo, silicon or aluminum in a quantity of I to 2 wtO/o, manganese in a quantity of not greater than 1. 15 wtP/o, chromium in a quantity of 0.90 to 1.60 wVVo and the balance being iron and impurities and having an oxygen content not greater than 13 ppm. A product made of the raw material is, after having been hardened, tempered at a high temperature within the range of 180 to 4000C, preferably within the range of 230 to 300r and more preferably within the range of 250 to 2800C so that the quantity of the retained austenite and the -<8>- hardness can attain not greater than 8 % and not lower than HRC 60, respectively. It is to be noted that if the thickness of the product is a thick walled. addition of molybdenum (Mo) to the raw material is recommended to improve the hardening property, in which case the amount of molybdenum to be added is not greater than 0.25 wt'Yo, preferably within the range of 0. 10 to 0.25 wV?/o.

The reason for the selection of the oxygen content not greater than 13 ppm is because a result of test conducted on non-metallic inclusions has indicated that if the oxygen content is not greater than 13 ppm, the presence of non-metallic inclusions is rarely observed on a fracture surface and, therefore, it appears that the effect of the retained austenite on the rolling wear can be reduced.

The reason for the selection of the amount of Si or AI within the range of 1 to 2 wtO/o is because if the amount of Si or AI to be added is lower than 1 wt% will result in reduction of the hardness at the time of the high-temperature tempering and because if the amount of Si or AI to be added is greater than 2 wt%, the toughness would be undesirably affected, resulting in problems associated with forging, grinding and milling. In addition, although the temperature at which the high-temperature tempering is carried out is preferably within the range of 230 to 3009C and more preferably within the range of 250 to 2809C, a result of experiments has shown that the amount of the retained austenite in the product tempered at 230C is 8% and, accordingly, the amount of the retained austenite is not greater than 8% and preferably not greater than 6%.

The rubber body 15b of each of the seals 15 employed in the bearing 6 is preferably prepared from fluorine-contained rubber (fluoro rubber).

The grease filled in the bearing 6 is of a kind containing a thickening agent made of urea. Of the various urea resins, the use is _<9>_ preferred of an aromatic urea because of its excellent heat resistance. The base oil for the grease may be a mineral oil or a synthetic oil, but the use of the synthetic oil is preferred. Of the various synthetic oils, the use is preferred of an ether oil because of its excellent heat resistance.

The amount of the grease filled in the bearing 6 is preferably within the range of 40 to 50 % relative to the volume of an internal space in the bearing 6. The volume of the internal space in the bearing 6 is the volume of a space delimited between the inner and outer races I I and 12 and bound by the opposite seals 15, less the volume occupied by the rolling elements 14 and the retainer 13.

The flywheel damper support structure of the construction described above is featured in that the inner and outer races I I and 12 of the bearing 6 are made of steel as a raw material, which steel has a retained austenite in a quantity not greater than 8 % and also has a hardness not lower than HRC 60. Accordingly, as compared with the use of a generally used bearing steel (for example, SUR material complying the JIS standards), (1) the dimensional change under the high-temperature environment is minimized, and any possible occurrence of fretting resulting from an excessively large gap and an excessively small gap can be avoided, and (2) any possible reduction in hardness under the high-temperature environment is minimal with the resistance to fretting improved. In particular, where the oxygen-containing steel containing the previously described respective contents of carbon, silicon or aluminum, manganese and chromium with the balance being iron and impurities is used as the raw material and where the product made of such raw material is, after having been hardened, tempered to render the content of the retained austenite to be not greater than 8% and also to render the product to have a hardness not lower than HRC 60, the above described meritorious effects (1) and (2) can be paramount.

-< I 0>- Also, where the seal 15 is made of fluorine-contained rubber, the heat resistance and the resistance to compressive permanent deformation are excellent as compared with the use of a standard seal made of acrylic rubber and, therefore, no dimensional change in outer diameter of the seal 15 occur, accompanied by improvement of the sealing property of an outer diametric portion of the seal 15.

Where the grease of a kind containing a thickening agent made of urea and the synthetic oil as the base oil is used, the heat resistance of the grease can be improved since the synthetic oil is excellent in terms of the resistance to fretting and the heat resistance, and, therefore, the bearing can exhibit an excellent resistance to seizure. Where of the various urea resins, an aromatic urea excellent in heat resistance is used for the thickening agent and of the various synthetic oils, the ether oil excellent in heat resistance is used for the base oil as hereinbefore described, the heat resistance can further be improved.

Moreover, since the amount of the grease filled is chosen to be within the range of 40 to 50% which is greater than the standard amount of the grease which has hitherto been within the range of 25 to 30%, the lubricating property can be improved along with improvement in resistance to fretting and resistance to seizure.

By suitably combining the raw material for each of the inner and outer races I I and 12, the raw material for the seal 15, the raw material for the grease and the increase of the amount of the grease filled, the flywheel damper support structure can be realized in which the dimensional change and reduction in hardness of the bearing raceway members under the high-temperature environment can be minimized, the heat resistance of the grease is improved and which has the excellent resistance to fretting and also to seizure and, hence, has an increased lifetime.

_<11>_ The following table 1 illustrate results of tests conducted on the product according to the embodiment of the present invention and the standard produce to determine the occurrence of fretting and the resistance to seizure which are exhibited when the quantity of the retained austenite in each of the inner and outer races 11 and 12, the hardness of each of the inner and outer races 11 and 12 and the content of the grease are varied. For the urea which serves as the thickening agent contained in the grease, the aromatic urea was used and for the synthetic oil the ether was employed. The amount of the grease filled was within the range of 40 to 50%. The resistance to fretting was evaluated in three ratings represented by @, 0 and X. Table 1 Retained Grease Resistance Resistance Material Austenite HRC Composition to Fretting to Seizure Greater than 8% Metallic soap + mineral oil 0 X Standard and not greater Lower Urea + mineml oil 0 X (SUJ2) than 15% than 60 Urea + synthetic oil 0 0 Metallic soap @ X Embodi- Not greater Not lower Urea + mineral oil X ment 1 than 8% than 60 Urea + synthetic oil A @ Table 1 makes it clear that if the raceway members are made of steel and contains the retained austenite in a quantity not greater than 8% and has a hardness not lower than HRC 60, the resistance to fretting is excellent. Also, Table 1 makes it clear that if the base oil of the grease is employed in the form of the synthetic oil, the resistance to seizure is excellent.

The following table 2 illustrate results of tests conducted to determine how the resistance to fretting and the resistance to seizure are affected when the amount of the grease filled is chosen to be within the range of 25 to 35% and within the range of 40 to 50%. In both cases, the grease contained urea employed as the thickening agent and was prepared from mineral oil used as the base oil. Table 2 makes it clear that the -<U>amount of the grease filled within the range of 40 to 50% has resulted in the excellent resistances to fretting and seizure, respectively. Table 2 Material Retained HRC Amount of Grease Resistance Resistance Austenite Filled to Fretting to Seizure Embodi- Not greater Not lower 25 to 35% 0 0 ment than 8% than 60 40 to 50% @ 0 Although the present invention has been fully described in connection with the preferred embodiment thereof with reference to the accompanying drawings which are used only for the purpose of illustration, those skilled in the art will readily conceive numerous changes and modi fications within the framework of obviousness upon the reading of the specification herein presented of the present invention. Accordingly, such changes and modifications are, unless they depart from the scope of the present invention as delivered from the claims annexed hereto, to be construed as included therein.

-<13>-

Claims

CLAINIS

1. A flywheer damper support structure for the support of a flywheel damper which is interposed between an automotive engine and a transmission, said support structure comprising:

a rolling bearing interposed between an engine-side mass and a transmission-side mass of the flywheel damper for supporting the masses, including inner and outer race members; said rolling bearing being filled with a grease containing urea as a thickening agent; wherein at least one of the inner and outer race member which is fitted to the engine-side mass is made of steel as a raw material and contains a retainer austenite in a quantity not greater than 8% and has a hardness not lower than HRC 60.

2. The flywheel damper support structure as claimed in Claim 1, wherein the amount of the grease filled is Within the range of 40 to 50% relative to an inner space of the rolling bearing.

3. The flywheel damper support structure as claimed in Claim 1 or 2, wherein the grease is prepared from a synthetic oil as a base oil and contains an aromatic urea as a thickening agent.

4. The flywheel damper support structure as claimed in any one of Claims 1 to 3, wherein the rolling bearing is sealed by seals made of fluorine-contained rubber.

5. The flywheel damper support structure as claimed in Claim 1 or 4, wherein the race members contain molybdenum added thereto in a quantity not greater than 0.25 wC/o.

6. The flywheel damper support structure as claimed in Claim 1 or 5, wherein the race members has an oxygen content of not greater than 13 ppm.

-<M>-

7. The flywheel damper support structure as claimed in Claim I or 6, wherein the race members contain silicon or aluminum in a quantity within the range of I to 2 wtO/o.

8. The flywheel damper support structure as claimed in Claim I or 7, wherein the engine-side mass and the transmission-side mass are opposed to each other in an axial direction and wherein the inner race member of the rolling bearing is mounted on an outer diametric surface of an inner peripheral portion of the engine-side mass that protrude in one axial direction and the outer race member of the rolling bearing is mounted on an inner diametric surface of an inner peripheral portion of the transmission-side mass that protrude in an axial direction counter to such one axial direction.

9. A flywheel damper support structure substantially as herein described with reference to and as illustrated in the accompanying drawings.

-<15>-