JP2002181056A - Bearings for water pumps - Google Patents

Abstract

(57) Abstract: Provided is a water pump bearing provided with a seal device that is not denatured even when used in a high-temperature atmosphere and in contact with excessive cooling water. SOLUTION: An outer ring 10a fixed to a casing,
A rolling element 10b is provided between a driving unit provided on one end side and a rotating shaft 12 provided with an impeller on the other end side.
a in a water pump bearing 10 in which a seal is provided between the rotary shaft 12 and a pair of seal devices 400 each having an elastic material 15b fixed to both ends of the impeller-side seal device. Elastic material 1
5b is a vulcanizable fluororubber composition containing a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, or a vulcanizable fluororubber composition containing a tetrafluoroethylene-propylene terpolymer. A bearing for a water pump.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water pump bearing suitable for a water-cooled engine or the like of an automobile, and more particularly to a water pump bearing for supporting a rotating shaft of a water pump. Also, the present invention relates to a bearing provided with a sealing device for preventing grease from leaking from the bearing.

[0002]

2. Description of the Related Art As shown in FIG. 1, a water pump 30 for pumping and circulating cooling water for an engine generally includes a plurality of rotating shafts 12 to each of which an impeller 32 is fixed. The bearing 38 is supported on the casing 38 by the rolling bearing 10. Cooling water is impeller 32
The bearing 10 is hermetically sealed by a mechanical seal 40 disposed between the bearing and the bearing 10. However, in the water pump bearing 10 (hereinafter, sometimes simply referred to as a “bearing”), the sliding surface of the mechanical seal 40 with the rotating shaft 12 is in a water lubricated state. Leaks and enters the bearing 10 side, and steam and the like further enter the inside of the bearing 10 to deteriorate the bearing 10. Therefore, it is prevented that steam and the like enter the bearing 10 from the impeller 32 side. In addition, a sealing device is provided on the impeller 32 side of the bearing 10 to prevent the leakage of the lubricating grease sealed inside the bearing 10. The driving side 31 of the bearing 10 is also provided.
In addition, a seal device is provided to prevent intrusion of dust from the outside and prevent leakage of lubricating grease sealed inside the bearing 10.

The seal device on the impeller 32 side has a structure as shown in, for example, an axial sectional view in FIG.
In FIG. 2, the bearing 10 includes an outer ring 10a, a rotating shaft 12 constituting an inner ring, a ball 10b sandwiched between the outer ring 10a and the rotating shaft 12, and a retainer 10c for holding the ball 10b. The sealing device 400 includes a sealing plate 15 and a flinger 20. A sealing plate 15 is disposed in a seal groove 10d at an axial end of the outer ring 10a. The sealing plate 15 includes a metal core 15a and an elastic material 15b, and the elastic material 15b has three lip portions 15c, 15d, and 15e. The core 15a has an inverted L-shaped cross section,
It is crimped and installed in the seal groove 10d of FIG.
An elastic material 15b is in close contact with the outer surface of the core 15a. The elastic material 15b is made of nitrile rubber, a standard fluorine rubber having excellent heat resistance (for example, vinylidene fluoride-hexafluoropropylene binary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer) , The cross-section of which is bifurcated, the main lip 15e forming one of them extends obliquely to the lower right and the sub lip 15d forming the other Extends diagonally to the lower left. Further, a cylindrical third lip portion 15c is formed at an intermediate position of the core bar 15a so as to extend rightward in the drawing from the elastic member 15b.

[0004] On the rotating shaft 12, a flinger 20 made of stainless steel is arranged. Flinger 20
It comprises a small cylinder 20c closely fitted to the rotating shaft 12, a large cylinder 20a coaxially enclosing the small cylinder 20c, and a flange portion 20b connecting the two cylinders in the radial direction. Elastic material 15b
The third lip 15c of the flinger 20 is
a, and the main lip portion 15e is attached to the small cylinder 20c.
, And the sub lip portion 15d contacts the outer peripheral surface of the rotating shaft 12 to achieve sealing.

In the sealing device 400, when steam or water droplets of the cooling water are scattered from the outside, the cooling water is received on the outer peripheral surface of the flinger 20 so that the cooling water does not fall directly on the sealing plate 15. ing. Thereby, deformation and expansion of the sealing plate 15 (particularly, the third lip member 15c) can be reduced. On the other hand, grease or the like sealed inside the bearing 10 is sealed by the sub lip portion 15d and the main lip portion 15e of the sealing plate 15, so that leakage to the outside is prevented.

[0006]

With the recent high performance and high output of the engine, the temperature conditions around the engine have become severe, and the ambient temperature of the bearing may exceed 120 ° C. in some cases. However, nitrile rubber has a heat resistance limit of 1
Since the temperature is about 20 ° C., when nitrile rubber is used as the material of the elastic material of the sealing device of the bearing 10, the elastic material is hardened and deteriorated due to heat and loses elasticity. May be compromised. In addition, since the above-mentioned standard fluoro rubber has a heat resistance limit of 200 ° C. or more, there is no problem with heat resistance even under the above temperature conditions, but it deteriorates and deforms when it comes into contact with additives contained in cooling water. And the sealing performance may be reduced. Looking at the material of the elastic material of the conventional sealing device for water pump bearings,
There is known a hydrogenated nitrile rubber described in Japanese Patent No. 179395. Since the limit of heat resistance of the hydrogenated nitrile rubber is 150 ° C., there is no problem with heat resistance under the above temperature conditions, but it is included in cooling water to a certain extent as compared with standard fluoro rubber. However, when the additive comes into contact with the additive, it is deteriorated and deformed, and the sealing performance may be deteriorated. Therefore, the performance is not yet sufficient.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a bearing for a water pump provided with a sealing device which does not deteriorate even when used in a high-temperature atmosphere and in contact with excessive cooling water. It is in.

[0008]

The object of the present invention is to provide a rolling element between an outer ring fixed to a casing and a rotating shaft having a driving portion at one end and an impeller at the other end. A water pump bearing having a pair of sealing devices fixed to both ends of the outer ring, each having an elastic material, and sealing between the rotating shaft and the rotating shaft. Vulcanizable fluoro rubber composition, wherein the elastic material comprises a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer.
Alternatively, it is achieved by a water pump bearing comprising a vulcanizable fluoro rubber composition containing a tetrafluoroethylene-propylene binary copolymer.

[0009]

The above vinylidene fluoride-tetrafluoroethylene-propylene terpolymer has a relatively small proportion of vinylidene fluoride because it is a ternary copolymer, and does not contain hexafluoropropylene. The dehydrofluorination reaction of vinylidene fluoride is hardly caused by the reactive compound. Also,
The tetrafluoroethylene-propylene binary copolymer does not contain vinylidene fluoride as a raw material, and also does not contain hexafluoropropylene. Therefore, a basic compound such as an amine does not cause a hydrofluoric acid reaction of vinylidene fluoride. Therefore, it is suitable as an elastic material of the sealing device for a water pump bearing of the present invention. These fluororubbers are also vulcanizable, including standard fluororubbers (vinylidene fluoride-hexafluoropropylene binary copolymer or vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer). Chemical resistance is much better than that of fluororubber compositions). That is, a vulcanizable fluororubber composition containing a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer or a vulcanizable fluororubber composition containing a tetrafluoroethylene-propylene terpolymer is water-cooled. When used as an elastic material of a seal device for a pump bearing, the seal device does not change even when used in a high-temperature atmosphere or in contact with cooling water, and can exhibit good sealing performance over a long period of time.
Therefore, the water vapor or the like does not enter the bearing and the performance of the bearing does not deteriorate.

[Detailed Description of the Invention] Hereinafter, the present invention will be described in detail.

The water pump bearing of the present invention includes, for example, a sealing device shown in FIG. That is, the bearing 10
An outer ring 10a, a rotating shaft 12 forming an inner ring, and an outer ring 10
and a retainer 10c for holding the ball 10b, the seal device 40 comprising a sealing plate 15 and a flinger 20.
0 is incorporated. Sealing plates 15 are arranged in seal grooves 10d at both ends in the axial direction of the outer ring 10a. The sealing plate 15 includes a core metal 15a and an elastic material 15b, and the elastic material 15b has three lip portions 15c, 15d, and 15e. The core metal 15a has an inverted L-shaped cross section,
Is crimped in the seal groove 10d. An elastic material 15b is in close contact with the outer surface of the core 15a.

The elastic member 15b is made of a fluorine rubber, which will be described later, and has a bifurcated cross section. 15d extends obliquely to the lower left.
Further, a cylindrical third lip portion 15c is formed at an intermediate position of the core bar 15a so as to extend rightward in the drawing from the elastic member 15b.

A flinger 20 made of stainless steel is arranged on the rotating shaft 12. Flinger 20
It comprises a small cylinder 20c closely fitted to the rotating shaft 12, a large cylinder 20a coaxially enclosing the small cylinder 20c, and a flange portion 20b connecting the two cylinders in the radial direction. Elastic material 15b
The third lip 15c of the flinger 20 is
a, and the main lip portion 15e is attached to the small cylinder 20c.
, And the sub lip portion 15d contacts the outer peripheral surface of the rotating shaft 12 to achieve sealing.

The elastic material 15b may be a vulcanizable fluororubber composition containing a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer or a vulcanizable vulcanizable material containing a tetrafluoroethylene-propylene terpolymer. It consists of a flexible fluororubber composition. The component ratio in these copolymers is not particularly limited, but in the vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, 1 to 70 mol% of vinylidene fluoride and 1 to 7 mol of tetrafluoroethylene are used.
0 mol%, propylene is preferably in the range of 1 to 70 mol%, more preferably 1 to 30 mol% of vinylidene fluoride,
Tetrafluoroethylene is in the range of 10 to 60 mol%, and propylene is in the range of 10 to 60 mol%. In the tetrafluoroethylene-propylene binary copolymer, the content of tetrafluoroethylene is 20 to 80% by mole, and the content of propylene is 20 to 80%.
The range is preferably 80 mol%, more preferably 30 to 60 mol% of tetrafluoroethylene and 30 to 30 mol% of propylene.
６０60 mol%. Further, these copolymers may be copolymerized with several mole% of a so-called cure site monomer (for example, an iodine compound or a bromine compound) which serves as a cross-linking point at the time of cross-linking. Unsaturated bonds may be introduced into the union. Such vinylidene fluoride
As the tetrafluoroethylene-propylene terpolymer, “BRE LJ-298005” manufactured by DINEON is available.
(Trade name) and "AFLAS SP" manufactured by Asahi Glass Co., Ltd.
Commercial products such as "AFLAS SZ" (trade name) can be used. As the tetrafluoroethylene-propylene binary copolymer, “AFLAS 15” manufactured by Asahi Glass Co., Ltd.
Commercial products such as "0" and (trade name) can be used.

The method for vulcanizing the copolymer is not particularly limited, and is a usual vulcanization method for fluororubber, but polyol vulcanization or peroxide vulcanization can be applied. For example, as a polyhydroxy compound as a vulcanizing agent in the case of polyol vulcanization, a conventionally known polyhydroxy aromatic compound or fluorinated polyhydroxy aliphatic compound can be used. Among them, hydroquinone, 2,2-bis (4-
Hydroxyphenyl) propane [bisphenol A],
2,2-bis (4-hydroxyphenyl) perfluoropropane [bisphenol AF] and the like are preferably used. These are also alkali metals, alkaline earth metals,
Salts such as organic onium compounds may be used. The compounding amount of these polyol vulcanizing agents is in the range of 0.5 to 10 parts by weight based on 100 parts by weight of the copolymer, and in this range, there is no possibility of insufficient vulcanization or excessive vulcanization. .

On the other hand, an organic peroxide which is a vulcanizing agent in the case of peroxide vulcanization is an organic compound having an —O—O— bond in its molecule, and specifically, peroxyketal, dialkyl Oxides, diacyl peroxides, peroxyesters, hydroperoxides and the like can be mentioned. More specifically, benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t
-Butylperoxy) hexane, 2,5-dimethyl-
2,5-di (t-butylperoxy) hexyne-3,
α, α′-bis (t-butylperoxy) -p-diisopropylbenzene, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane and the like can be exemplified. The compounding amount of these organic peroxides is in the range of 0.5 to 10 parts by weight based on 100 parts by weight of the copolymer, and in this range, there is no possibility of insufficient vulcanization or excessive vulcanization. .

When vulcanizing the polyol, an acid acceptor,
In addition, a metal oxide and a metal hydroxide are blended as essential components as a vulcanization aid. Examples of this are calcium hydroxide, magnesium hydroxide, calcium oxide,
Examples thereof include zinc oxide, lead oxide, and magnesium oxide. Among them, a combination of calcium hydroxide and magnesium oxide is preferable. The compounding amount of these metal oxides and metal hydroxides is preferably 0.5 to 50 parts by weight, more preferably 1 to 30 parts by weight, based on 100 parts by weight of the copolymer. Further, an onium salt (quaternary ammonium salt or quaternary phosphonium salt) may be blended as a vulcanization accelerator. As a specific example, as the quaternary ammonium salt,
Examples include tetrabutylammonium hydrogen sulfate, tetramethylammonium hydrogen sulfate, tetraethylammonium hydrogen sulfate, trioctylmethylammonium hydrogensulfate, tridecylmethylammonium hydrogensulfate, and trimethylbenzylammonium hydrogensulfate. Examples of the quaternary phosphonium salt include tetrabutylphosphonium chloride, tetrabutylphosphonium bromide, tributyl (methoxypropyl) phosphonium chloride, trioctylmethylphosphonium chloride, and tridodecylmethylphosphonium chloride. For example, two or more kinds may be used in combination. The compounding amount of these onium salts is preferably in the range of usually 0.3 to 5 parts by weight based on 100 parts by weight of the copolymer, and in this range, insufficient vulcanization, overvulcanization and early vulcanization may occur. There is no.

In peroxide vulcanization, an unsaturated polyfunctional compound is used as a vulcanization aid.
Examples include a polyallyl compound, a methacrylate compound, a divinyl compound, and polybutadiene. Of these, triallyl isocyanurate and triallyl cyanurate are preferred. The compounding amount of these unsaturated polyfunctional compounds is 0.5 to 20 parts by weight, preferably 1 to 10 parts by weight per 100 parts by weight of the copolymer.

The above-mentioned copolymers may further contain fillers such as carbon black, silica, clay, talc and calcium carbonate which have been used as a conventionally known reinforcing filler, other pigments, dyes, antioxidants and antioxidants. , Stabilizers, processing aids, plasticizers, release agents and the like may be added and blended.

The method of obtaining the elastic material of the sealing device 400 using the above-mentioned components is not particularly limited, but the raw material rubber such as vinylidene fluoride-tetrafluoroethylene-propylene terpolymer or tetrafluoroethylene is used. -It is possible to uniformly mix the propylene binary copolymer, the filler and other additives using a conventionally known rubber kneading device such as a rubber kneading roll, a pressure kneader or a Banbury mixer. . The kneading conditions are not particularly limited, but are usually at a temperature of 30 to 80 ° C and 5 to 5 ° C.
By kneading for 60 minutes, sufficient dispersion of various additives can be achieved.

The manufacturing method for forming the elastic member 15b of the sealing device 400 is not particularly limited, but the fluororubber composition may be heated while being pressed in a mold. It can be manufactured by a known rubber molding method such as injection molding. For example,
In the case of compression molding, a metal core (forming a core of a sealing device) coated with an adhesive in advance is inserted into a mold, and a sheet of the unvulcanized rubber composition manufactured by the method described above is placed thereon. Usually 12
It can be manufactured by vulcanizing under pressure at 0 to 250 ° C. for about 3 minutes to 2 hours. In addition, by performing post-vulcanization on the obtained elastic material 15b, vulcanization is completed, and at the same time, excess volatile components are volatilized.
This is preferable since an effect is recognized in improving the physical properties of the above. The conditions of the post-vulcanization are not particularly limited, but a heat treatment at a temperature of, for example, 150 to 250 ° C. for about 1 to 50 hours can be performed.

[0022]

The present invention will be further described below with reference to examples. However, the present invention is not limited at all by the examples.

(First experiment) First, as a first experiment, in order to confirm the cooling water resistance of the elastic material of the sealing device for a water pump bearing of the present invention, an autoclave was used, and the composition shown in Table 1 was used. No. 3 JIS dumbbell-shaped test piece (thickness: 2 mm) was immersed in LLC manufactured by CCI (diluted to 50% with water) at 140 ° C. for 500 hours, and changes in various physical properties were measured. In addition, * 1 in the left column of Table 1 is a trade name of a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer manufactured by Asahi Glass Co., Ltd. * 2 is a tetrafluoroethylene-propylene terpolymer manufactured by Asahi Glass Co. The trade name of the copolymer, * 3 is the trade name of JSR's middle and high nitrile rubber, * 4 is the trade name of Zeon's hydrogenated nitrile rubber, * 5 is the product of Daikin The trade name of vinylidene fluoride-hexafluoropropylene binary copolymer is * 6
Is the product name of SRF grade carbon black manufactured by Asahi Carbon Co., * 7 is the product name of diatomaceous earth manufactured by Manvill, * 8 is the product name of magnesium oxide manufactured by Kyowa Chemical Industry, * 9
Is the brand name of calcium hydroxide manufactured by Omi Chemical Co., Ltd. * 1
0 is the brand name of the antioxidant manufactured by Ouchi Shinko Chemical Co., Ltd.
* 11 is a brand name of an antioxidant manufactured by Ouchi Shinko Chemical Co., Ltd. * 12 is a brand name of an organic peroxide manufactured by NOF Corporation * 13 is a triallyl isocyanate manufactured by Nippon Kasei Co., Ltd. * 14 is the product name of stearic acid manufactured by Kao Corporation, * 15 is the product name of the vulcanization accelerator manufactured by Ouchi Shinko Chemical Industry Co., Ltd., * 16 is the product name of Ouchi Shinko Chemical Industry Co., Ltd. The trade names of the vulcanization accelerators manufactured by each are shown.

The sample was prepared by first kneading using a kneading roll at a ratio shown in Table 1 and a thickness of about 2.2.
An unvulcanized rubber sheet of mm was produced. Next, the unvulcanized rubber sheet was inserted into a mold having a length and width of 150 mm and a thickness of 2 mm.
Under the conditions of the primary vulcanization described in 1 above, a pressure of 50 kgf / cm ² was applied to perform vulcanization molding. Examples 1 to 3 and Comparative Examples 2 and 3 were taken out of the mold and placed in an oven in Table 1.
The post-vulcanization was carried out under the conditions of the secondary vulcanization described in the above. The obtained vulcanized rubber sheet was punched into a JIS dumbbell-shaped No. 3 test piece, and the physical properties in a normal state were measured. The hardness was determined by stacking three dumbbell specimens and using a type A durometer hardness tester based on JIS K 6253.
It was measured based on SK 6251. The LLC resistance was measured based on JIS K 6258, except that autoclave was used. The results are shown in Table 1.

[0025]

[Table 1]

As is evident from the results in Table 1, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer or tetrafluoroethylene-propylene terpolymer in the range of the present invention is used as a raw rubber. The rubber composition showed good LLC resistance. In addition, the rubber composition of Comparative Example 1 using nitrile rubber as the raw rubber showed curing deterioration. The rubber composition of Comparative Example 2 using a hydrogenated nitrile rubber as a raw rubber is the same as that of Comparative Example 3 using a vinylidene fluoride-hexafluoropropylene binary copolymer as a standard rubber as a raw rubber. Although better than the rubber composition, it exhibited a decrease in tensile properties with swelling.

(Second Experiment) Using a test apparatus shown in FIG. 3, a heat resistance test and a water resistance test of a bearing provided with a sealing device having the structure shown in FIG. 2 were performed. The test device shown in FIG.
The bearing supporting the rotating shaft is heated by a heater via a housing, and a fixed amount of cooling water is supplied to the end of the bearing by a fixed amount pump. With this test equipment,
The change over time of the performance of the elastic material of the seal device provided at the bearing end was examined. The elastic materials of the sealing device used in the above test were the same as those in Examples 1 and 3 and Comparative Examples 2 and 3 described in the first experiment.
And the same composition.

First, an unvulcanized rubber composition was prepared in the same manner as in the first experiment, and the resulting unvulcanized rubber sheet was coated with a core metal 15a to which an adhesive was applied in advance. placed in the inserted mold was loaded with vulcanization molding pressure 30 kgf / cm ² in the primary vulcanization conditions shown in Table 1. Further, post-vulcanization was carried out in an oven in a state of being taken out of the mold under the secondary vulcanization conditions shown in Table 1. Then, the obtained sealing plate 15
A flinger 20 was mounted on the bearing 10 and assembled into the bearing 10 to produce a test bearing.

The test conditions are as follows.・ Bearing temperature: 150 ° C. ・ LLC: LLC manufactured by CCI ・ LLC water injection amount: 50 ml / min ・ Rotation speed: 8000 rpm ・ Test time: 1000 hours

The evaluation items were a change in hardness of the main lip 15e and a deformation (undulation) of the third lip. The hardness was measured based on JIS K 6253, using IRHD (International R).
ubber Hardness Degree) was performed using a micro hardness tester. Table 2 shows the results.

[0031]

[Table 2]

As is evident from the results in Table 2, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer or tetrafluoroethylene-propylene terpolymer within the scope of the present invention was used as the raw material rubber. The sealing device in which the elastic material is formed from the rubber composition used has a good LLC resistance and an excellent sealing property since the hardness of the main lip is hardly changed and the third lip is not deformed. It seems to be. The rubber composition of Comparative Example 2 using a hydrogenated nitrile rubber as a raw rubber is the rubber composition of Comparative Example 3 using a vinylidene fluoride-hexafluoropropylene binary copolymer as a standard rubber as a raw rubber. Although it is better than the sealing device in which the elastic material is formed of a material, the hardness of the main lip changes greatly and the third lip is deformed, so that the sealing performance is inferior to the bearing of the embodiment, and the life of the bearing is reduced. Seems short.

[0033]

As described above, according to the water pump bearing of the present invention, the elastic material of the sealing device is a vulcanizable fluoro rubber containing a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer. The composition, or a vulcanizable fluororubber composition containing a tetrafluoroethylene-propylene binary copolymer, and has excellent LLC resistance, so that it can exhibit good sealing performance over a long period of time, Water vapor or the like that has passed through the mechanical seal from the impeller side does not enter the bearing, and stable bearing performance can be guaranteed.

[Brief description of the drawings]

FIG. 1 is an axial sectional view showing an example of a water pump to which the present invention is applied.

FIG. 2 is an axial sectional view showing an example of a sealing device.

FIG. 3 is a sectional view of a test apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Bearing 10a Outer ring 12 Rotating shaft 15 Sealing plate 15a Core 15b Elastic material 20 Flinger 30 Water pump 32 Impeller 400 Sealing device

Continued on the front page (72) Inventor Shunichi Yabe 1-5-50 Kugenuma Shinmei, Fujisawa-shi, Kanagawa F-term in NSK Ltd. (reference) 3J016 AA01 BB03 BB16 CA01 CA06 CA07 4J002 BD141 BD151 GM05

Claims (1)

[Claims] A rolling element is provided between an outer ring fixed to a casing and a rotating shaft having a driving part at one end and an impeller at the other end, and is fixed to both ends of the outer ring. A pair of sealing devices, each having an elastic material,
In a bearing for a water pump in which a seal is provided between the rotating shaft and the rotating shaft, at least the elastic material of the sealing device on the impeller side includes vinylidene fluoride-tetrafluoroethylene-
A water pump bearing comprising a vulcanizable fluororubber composition containing a propylene terpolymer or a vulcanizable fluororubber composition containing a tetrafluoroethylene-propylene terpolymer.