GB2182948A - Automatic transmission fluid composition - Google Patents

Abstract

An automatic transmission fluid composition comprises a major amount of mineral oil and/or synthetic oil as a base oil, and 0.1-5% by weight of magnesium sulfonate on the basis of the total amount of the composition as an essential component.

Description

SPECIFICATION Automatic transmission fluid composition 2. Background of the Invention (1) Field of the Invention This invention relates to an automatic transmission fluid composition, and more particularly to an automatic transmission fluid composition which is excellent in durability in shift transmission, shift feeling, and prevention for the slip of a clutch after bonding, and in addition which has a small variation with time in a coefficient of friction of the composition during use.

(2) Description of the Prior Art Recently, a rate of installing automatic gears on motorcars increases rapidly. An automatic gear is a speed change gear having such a mechanism in which a transmission torque ratio is automatically established in response to a speed of a car, a magnitude of load or the like. Such automatic gear comprises a torque converter part, a multiple disk clutch, a planetary gear part, and a hydraulic controlling part. Automatic transmission fluid is a common lubrication oil for all the parts described above, and which functions as a transmission fluid for motive power, as a lubricating oil for gears and bearings, and as a hydraulic operating fluid.

Such a shift operation wherein various reduction gear ratios are attained by changing the connections between the respective members of planetary gears is carried out by utilizing a contact clutch and braking band. At the present time, a type of the contact clutch is generally a wet clutch composed of a multiple disk clutch comprising a driven plate being a steel plate and a drive plate being a paper frictional material. Frictional properties of such wet clutch exert an influence upon the transmitting function of an automatic transmission unit, in its turn, shift feeling of a motorcar Such frictional properties are evaluated by a SAE No. 2 friction tester and which is well known by those skilled in the art.This type of tester is essentially an inertia dynamometer wherein the kinetic energy of a rotor is spent by a frictional plate, and a coefficient (u) of friction is calculated by means of friction torque from the following equation: T 2nSP? T: friction torque n: number of clutch plate S: area of piston P: pushing pressure of piston r: average radius of clutch plate.

As a method for measuring a coefficient of friction, there are dynamic method and static method. The dynamic method is effected by such a manner that an inertia plate (mounted on a motor shaft) is rotated at a high speed by means of a motor for a given period of time, thereafter a motor power supply is shut off, and at the same time pneumatic pressure is applied to a piston, whereby a driven plate is pressed against a drive plate which has been rotated integrally with the motor shaft to stop the movement of the inertia plate. A certain torque at the time of rotating the motor is obtained from a friction torque curve in the above case, and a coefficient Wd) of dynamic friction is calculated from the above equation. Furthermore a coefficient (,ltO) of static friction is obtained from the torque immediately before the stoppage.

In static method, such friction torque produced by a facing up of the drive plate and the driven plate is obtained by rotating the inertia plate by means of an auxiliary motor at a very low speed while applying a pneumatic pressure to the piston, and a coefficient (us) of static friction is calculated from the value obtained as described above.

While a value of such coefficient of friction varies dependent upon a combination of a paper frictional material being the drive plate with an automatic transmission fluid, such influence due to a composition of the automatic transmission fluid is very remarkable. In general, a larger value of #d is desired in view of favourable durability, i.e., continuance of preferred shift transmission.

Furthermore the closer value of ,ao/,ad to 1.0 provides the smoother shift feeling, so that it is preferable. The larger value of ,~~s brings about the more effective prevention of slip after bonding a clutch, so that it is desirable.

However, such automatic transmission fluids which have widely been used heretofore could not have been necessarily satisfied with them in view of their values of coefficient of friction.

3. Object of the Invention An object of the present invention is to provide an automatic transmission fluid composition wherein a coefficient Wd) of dynamic friction according to dynamic method is high, a ratio (yo/,ud) of a coefficient of static friction to the coefficient of dynamic friction is close to 1, and the coefficient (us) of static friction according to static method is high, besides there is a very small variation with time in both the coefficients of friction in use of the composition.

Another object of the present invention is to provide an automatic transmission fluid composition characterized by containing a major amount of mineral oil and/or synthetic oil as a base oil, and 0.1-5% by weight of magnesium sulfonate on the basis of the total amount of the composition as an essential component.

4. Detailed Description of the Invention Either mineral oils or synthetic oils may be used as the lubricating base oils in the present invention wherein such an oil having a viscosity range of from 1.5 to 5.0 cSt at 1000C may be employed. Accordingly, it is possible to use any single material or admixture consisting of two or more components which satisfy a viscosity of 1.5 to 5.0 cSt at 100 C. In this respect, such materials having a viscosity range at 1000C of from 1.5-50 cSt can be used in case of blending two or more components together.More specifically, examples of such mineral oil include 70 pale, SAE 10, SAE 20, SAE 30, SAE 50, bright stock, and cylinder stock; while examples of preferably employed synthetic oil include decene-1 oligomers (those having a viscosity within a range of 2.0-50 cSt at 100 C), diesters (di-2-ethylhexyl sebacate, dioctyl adipate, dioctyl dodecanoate and the like), and polyol esters (pentaerythritol tetraoleate, trimethylolpropane tripelargonate and the like). Preferably the automatic transmission fluid of the present invention comprises at least 70% by weight of the total composition, and more preferably at least 80% by weight of the total composition, of mineral and/or synthetic oil.

Furthermore the "magnesium sulfonates" referred to in the present invention are magnesium salts of alkyl aromatic sulfonic acids having a molecular weight of from 100 to 700. Specific examples of such alkyl aromatic sulfonic acids include so-called petroleum sulfonic acids, synthetic sulfonic acids and the like. The term "petroleum sulfonic acids" means those obtained by sulfonating alkyl aromatic compounds in the lubricating oil fractions of mineral oils. Examples of such synthetic sulfonic acids include by-products from detergent manufacturing plants, sulfonated alkylbenzene having straight- or branched-chain alkyl group prepared by alkylating benzene with polyolefin, sulfonated alkylnaphthalene such as dinonylnaphthalene and the like.

The magnesium sulfonates of the present invention are not limited to neutral salts (normal salts) only, but basic sulfonates obtained by heating neutral salts with excess magnesium in the presence of water, and so-called overbasic sulfonates prepared by reacting neutral or basic salts with oxides or hydroxides of an alkaline -earth metal in the presence of carbonic acid gas may also be utilized in the present invention.

However, it should be noted that the method for producing the magnesium sulfonates of the present invention is not limited to those as mentioned above, but any suitable manufacturing process is acceptable.

While the magnesium sulfonates of the present invention are publicly known compounds as a metal cleaner, heretofore only calcium sulfonate and calcium pheneate have been used as a metal cleaner for automatic transmission oils (e.g. such fact is described in the SAE paper 680040 (1968)). Unlike the present invention, there has never been such an example wherein magnesium sulfonate is added to an automatic transmission oil for the sake of positively improving frictional properties.

In the present invention, it is preferable to use such an over basic magnesium sulfonate among magnesium sulfonates, which has a base number of 300 or more, and preferably 350 or more according to the potentiometric titration method (perchloric acid method) as provided by JIS K 2501 5.2.3 in view of the particularly excellent improving effects in frictional properties.

A content of the magnesium sulfonate is 0.1-5.0% by weight, and preferably 0.3-2.0% by weight on the basis of the total weight of a composition.

Other additives which are used to add to an ordinary lubricating oil than the magnesium sulfonates described above may arbitrarily be used with respect to the automatic transmission fluid compositions of the present invention. Examples of these additives include metallic cleaners such as other alkaline earth metal sulfonates than magnesium sulfonate, alkaline earth metal pheneates, phosphonates, carboxylates, salicylates and the like; ash-free dispersants such as alkenyl succinic imides, alkylbenzyl amines and the like; antioxidants such as zinc alkyl or aryl dithiophosphates, hindered phenols, aromatic amines and the like; extreme pressure agents such as olefin sulfides, sulfuric esters, phosphoric esters, phosphorous esters and the like; oiliness agents/friction adjustors such as fatty acids, salts and esters of fatty acid, higher alcohols, acid phosphoric esters, amine compounds and the like; rust preventives; defoaming agents and the like.

(Examples) While the advantages of the compositions according to the present invention will be described in detail hereinbelow in conjunction with the following examples, it is to be noted that the scope of the present invention should not be limited to these examples.

Examples 1-5 and Comparative Examples 1-5 According to the composition indicated in Table 1, the automatic transmission fluid compo sitions of the present invention were prepared. Frictional properties ( d, s were mea sured with respect to these compositions prepared by means of SAE No. 2 friction tester (with the use of commercially available paper frictional materials), and the results thereof are shown also in Table 1.

For the comparison, frictional properties were measured also with respect to the compositions prepared in accordance with the composition indicated in Table 2 wherein no magnesium sulfonate is used, and the results thereof are shown in the following Table 2.

bl e

Ex. 1 Ex. 2 Ex. 3 Ex. Ex.4 Ex. 5 Mg Sulf.1) ( ) O.B.Ca M. Cl. - - - Sulf. 4 Comp. (B.N.300) Add. (0.7) (0.7) wt Pt.) ZnDTP (0.3] (0.3) Other Add.2) (5.0, r5.0) (6.0) (5.0) (5.0, P.M.O. P.M.O.+ Base Oil [4.3cst Po.-Ole.

Oil @100 C) g b b (4.3cat (88.4) (87.5) (86.7) (87.7) Q100 C) 7.

Fric. ud 0.14 0.16 0.16 0.15 0.15 Prop. us 0.14 0.15 0.14 0.14 0.14 uo/ud 1.0 1.0 1.0 1,0 .0 (1) over basic magnesium sulfonate (base number 400) (2) including friction adjustor, viscosity index improver and the like.

Explanation of the abbreviation in the Table: Sulf.=sulfonate, O.B.=Overbasic, Comp.=composition, pt.=part, Add.=additive, M. Cl. = me- tal cleaner, B.N.=base number, A.F. Disp.=ash-free dispersant, P.M.O.=purified mineral oil, Po.=poly, Ole.=olefin, Fric. Prop.=friction properties.

Table 2

M. CI. B Ca O.B.Ca O.B.Ca Suif. Phen. - Sulf.

Comp. (B.N.300)(B.N.300) (B.N.300) Add.

lwt pt.) A,F, DlsP. (6.0) (6.0) J 5.0) (6.0) (6.0 5, 0 ) pt.) Dther Add.l (0.3) (5.0) ~ Other Add.l) (5.0) (5.0) t5.0) (6.0) (5.0i P.M.O. Po.a-O Base Oil .4.3cst Oil @100 C) 4 4 e (4.3cbt (89.0) (88.3) (88.2) (88.7) 8100 C) ~ (88.3) Fric. ud 0.13 0.14 0.14 0.13 0.13 Prop. US 0.16 0.12 0.12 0.16 0.12 U 1.3 1.1 1.2 1.3 1.1 (1) Including friction adjustor, viscosity index improver and the like.

Explanation of the abbreviation in the Table: Cx.=Comparative Example, Phen.=pheneate.

O.B. =Overbasic.

As is apparent from the results of the frictional properties shown in Tables 1 and 2, the automatic transmission fluid compositions of Examples 1-5 according to the present invention have both high coefficients of dynamic friction (,ud) and static friction ( s), besides a ratio ( o/,ud) of the coefficient of static friction to the coefficient of dynamic friction is very close to 1.0. As a result, these compositions involve excellent performance as an automatic transmission fluid.

On the contrary, when the compositions of Comparative Examples 1 and 4 in which being no magnesium sulfonate is used are compared with those of Examples 1 and 3 corresponding to the compositions of the former Comparative Examples, respectively, both the ijo/,ud increase, so that shift feeling in driving becomes worse in both the cases. In cases of Comparative Examples 2 and 3 wherein calcium sulfonate and calcium pheneate which are well known as a metal cleaner are added to the composition of Comparative Example 1, respectively, both the ,usof these compositions decrease as a result of addition of such compounds as mentioned above, while both the ,uo//zd increase also as compared with the composition of Example 1 to which is added the corresponding magnesium sulfonate, and such increase is not favourable. Furthermore, in also the case where a mixed base oil of a mineral oil and a synthetic oil is used as a base oil, when the composition of Comparative Example 5 to which is added calcium sulfonate is compared with the composition of Example 5 to which is added magnesium sulfonate, the latter composition is superior to the former in all the frictional properties.

As described above, effects of adding magnesium sulfonate are clear, and it is apparent that only the compositions according to the present invention exhibit particular performance.

Claims (16)

1. An automatic transmission fluid composition comprising a major amount of mineral oil and/or synthetic oil as a base oil, and 0.1-5% by weight of magnesium sulfonate on the basis of the total amount of the composition as an essential component.

2. An automatic transmission fluid composition as claimed in claim 1 wherein said magnesium sulfonate is an over basic magnesium sulfonate having a base number of 300 or more.

3. An automatic transmission fluid composition comprising mineral and/or synthetic oil and between 0.1 and 5.0%, by weight of the total composition, of a magnesium sulphonate.

4. An automatic transmission fluid composition according to Claim 3, wherein the content of the magnesium sulphonate is between 0.3 and 2.0% by weight of the total composition.

5. An automatic transmission fluid composition according to Claim 3 or 4, wherein the magnesium sulphonate has a molecular weight between 100 and 700.

6. An automatic transmission fluid composition according to any one of Claims 3, 4 or 5, wherein the magnesium sulphonate is an over basic magnesium sulphonate.

7. An automatic transmission fluid composition according to Claim 6, wherein the magnesium sulphonate has a base number of not less than 300.

8. An automatic transmission fluid composition according to Claim 7, wherein the magnesium sulphonate has a base number of not less than 350.

9. An automatic transmission fluid composition according to any one of Claims 3 to 8, wherein the oil component has a viscosity of between 1.5 and 5.0 cSt at 100 C.

10. An automatic transmission fluid composition according to any one of Claims 3 to 9, wherein the oil component comprises at least two different oils.

11. An automatic transmission fluid composition according to Claim 10, wherein the oils comprising the oil component, each have a viscosity of between 1.5 to 50 cSt at 100 C, such that the viscosity of the total oil component is between 1.5 and 5.0 cSt at 100 C.

12. An automatic transmission fluid composition according to any one of Claims 3 to 11, the composition further comprising at least one additive of metallic cleaners, ash-free dispersants, antioxidants, extreme pressure agents, oiliness agents/friction adjusters, rust preventatives and defoaming agents.

13. An automatic transmission fluid composition according to any one of Claims 3 to 12, wherein the content of mineral and/or synthetic oil is at least 70%.

14. An automatic transmission fluid composition according to Claim 13, wherein the content of mineral and/or synthetic oil is at least 80%.

15. An automatic transmission fluid composition substantially as hereinbefore described with reference to the foregoing examples.

16. Any novel feature or combination of features as hereinbefore described.