JPS6361090A - Automotive gear oil composition - Google Patents

Abstract

PURPOSE:To obtain an automotive gear oil composition, containing an olefin sulfide, alkyl phosphate compound, etc., metal based cleaner and zinc dialkyl dithiophosphate in respective specific proportions in a base oil and having excellent extreme pressure properties as well as friction and abrasion characteristics. CONSTITUTION:A gear oil composition containing (A) an olefin sulfide in an amount of 0.5-4pt.wt. expressed in terms of sulfur, (B) an alkyl phosphate compound and/or alkyl (di)thiophosphate based compound in an amount of 0.02-0.2pts.wt. expressed in terms of phosphorus, (C) a metal cleaner in an amount of 0.01-0.6pts.wt. expressed in therms of metal and (D) a zinc dialkyl dithiophosphate in an amount of 0.04-0.5pts.wt. expressed in terms of zinc in 100pts.wt. base oil. The resultant gear oil composition is used common lubricant for speed change gears, center differential gears and rear axle hypoid gears.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a gear oil composition for commonly lubricating a transmission gear, a center differential gear, and a hypoid gear of a four-wheel drive vehicle.

In particular, the present invention significantly improves the lubrication of the transmission gear system of a four-wheel drive vehicle and the friction and wear characteristics of the synchronizer ring and gear cone compared to conventional sulfur-phosphorus gear oils, and at the same time improves the lubrication of the transmission gear system of four-wheel drive vehicles and the friction and wear characteristics of the synchronizer ring and gear cone, compared to conventional sulfur-phosphorus gear oils. The present invention relates to a lubricating oil composition for a drive system that can maintain the extreme pressure properties of a device.

In recent years, four-wheel drive vehicles have become rapidly popular in order to improve driving safety, but the drive system (transmission section, center differential section, and rear axle hypoid gear section) each has separate gears. It has been lubricated with oil. For example, for the transmission, a multigrade gear oil with an extreme pressure level of GL-3 to GL-4 containing a mild sulfur-phosphorus extreme pressure agent, and for the center differential part, a mild sulfur-phosphorus extreme pressure agent The extreme pressure level containing GL-
3 or GL-4 gear oil, and a gear oil with an extreme pressure level equivalent to GL-5 level or higher that contains a highly active sulfur-phosphorus extreme pressure agent due to the high extreme pressure required performance. has been used. But GL-
When a gear oil with high extreme pressure performance of level 5 is used in the transmission part, the friction and wear characteristics of the synchronizer ring and gear cone part are significantly impaired, which may lead to early synchronization failure. Furthermore, lubricating the drive system of a single vehicle with a separate gear oil poses problems in terms of lubrication management. That is, in the case of a four-wheel drive vehicle in which the transmission, front differential, and center differential are integrated, it is difficult to commonly lubricate them with gear oil according to the conventional concept.

The difference between transmission oil and hypoid oil is that the amount of sulfur-phosphorus extreme pressure agent added must be changed depending on the extreme pressure level, and in the case of transmission oil, the less active sulfur-phosphorus agent Applications include the use of pressure agents. Therefore, if transmission oil is applied to hypoid gears, the extreme pressure performance will be insufficient, causing seizure and wear.
Conversely, if hypoid gear oil is applied to a transmission, the active extreme pressure agent will create a reaction film on the metal surface, drastically reducing the coefficient of friction, making it impossible to obtain the desired synchronization effect, and causing rapid corrosion and wear. There were other problems.

In order to save time, the present invention has good extreme pressure properties as a transmission oil for a four-wheel drive vehicle that integrates a transmission, a front differential, and a center differential, and has high friction at the synchronizer ring and gear cone parts. This is a gear oil composition that achieves a high friction coefficient, has the durability to maintain the friction coefficient, and at the same time maintains the extreme pressure performance of the hypoid part at GL-5.

That is, in order to commonly lubricate the transmission gear, center differential gear, and hypoid gear of a four-wheel drive vehicle, the present invention uses (a) sulfurized olefin in an amount of 0.5 to 4 parts by weight as a sulfur content per 100 parts by weight of base oil. (b) 0.02 to 0.2 parts by weight of at least one selected from the group consisting of alkyl phosphoric acid compounds, alkyl thiophosphoric acid compounds, and alkyl dithiophosphoric acid compounds as a phosphorus content, (c1 metal-based detergent is 0.01 to 0.0 as the metal content.
5 parts by weight and fdl zinc dialkyldithiophosphate as zinc amount 0
．． The present invention relates to an automatic gear oil composition characterized in that the composition contains 0.04 to 0.6 parts by weight.

The present invention is based on a relatively highly active sulfur phosphorus extreme pressure agent, but by adding a new metal detergent and zinc dithiophosphate, the coefficient of friction between the synchronizer ring and gear cone is kept high (maintained). At the same time, the extreme pressure level is set to GL-
It is characterized by keeping it at the equivalent of 5.

The base oil used in the present invention may be a mineral oil refined by solvent refining or hydrogenation treatment, or a synthetic oil as described below, and may have an appropriate viscosity. For example, synthetic oils include polyalphaolefins, polybutenes,
Examples include diesters, polyethylene propylene, polyglycols, and hindered esters, but in consideration of the solubility of the additive, polyalphaolefins similar to mineral oil, polybutenes, and polyethylene propylene are preferable. In general, automotive transmission gear oils are 75W, 80W, 190, and 140 in consideration of fluidity at low temperatures.
Single grade type and 75W/90.7
5W/85.80W/90.80W/140.85W/
It is formulated into a multi-grade type such as 140, but a base oil of 4 to 20 centistokes (@100 revision) is usually used, and if necessary, polymethacrylate-based base oil is used to obtain a thickening effect and a pour point effect. A combination of a polymer compound or a polyethylene propylene or polybutene polymer compound and a polymethacrylate polymer compound is used.

In order to maintain extreme pressure performance at the GL-5 level, a sulfur-phosphorus compound is used, the main components of which are (a) sulfurized olefin and (b) phosphoric acid esters. ) Sulfur compounds are sulfurized olefins with a sulfur content of 40 to 50% by weight obtained by sulfurizing isobutylene polymers, sulfurized oils and sulfurized esters, and have traditionally been used alone or as extreme pressure agents for gear oils. have been used in combination of two or more types. Generally, sulfur content is used as an automotive gear oil in a range of 0.1 to 4 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts of base oil.

If it is less than 0.1, the extreme pressure properties will be insufficient, and if it is more than 4 parts by weight, the activity as a lubricating oil will become too strong, which is not preferable.

Next, the (bl phosphate ester compound) used in the present invention
Examples include alkyl or aryl phosphate compounds such as phosphorous diester, phosphorous triester, phosphonic acid ester, orthophosphoric acid ester, birophosphoric acid ester, acidic phosphoric acid ester, acidic F4 acid ester amine salt, and alkyl having 1 to 18 carbon atoms. alkylthiophosphates having groups, phosphoric acid ester compounds of acidic thiophosphates, alkylthiophosphates such as completely neutralized salts or partially neutralized salts of these alkylamines, and alkyldithiophosphates having an alkyl group having 1 to 18 carbon atoms. Phosphates, phosphoric acid ester compounds or thiophosphoric acid ester compounds of acidic dithiophosphoric acid esters, or alkyl dithiophosphoric acid esters such as completely neutralized or partially neutralized salts of alkyl amines, alkyl groups having 1 to 18 carbon atoms 2
Acidic.

Examples include phosphoric acid ester compounds or thiophosphoric acid ester compounds of dithiophosphoric acid esters, and dialkyl dithiophosphoric acid esters such as completely neutralized salts or partially neutralized salts of alkyl amines thereof. These phosphorus compounds may be used alone or in combination of two or more. One or more of the above phosphoric acid ester compounds are used in combination, and the phosphorus content is suitably 0.02 to 0.2 parts by weight per 100 parts by weight of the base oil. The wear resistance and seizure resistance of these phosphorus compounds alone can be improved by combining several kinds of them or by combining them with a sulfur compound. These phosphorus compounds are conventionally used as extreme pressure agents for gear oils, such as ANGLAMOL99.9.
88 (all Loupreseal products), HITECE-3
33, M6310 and above (Cooper products), and is a product in which the above-mentioned sulfur compounds are combined.

Next, the metal-based detergent (c) used in the present invention generally has the function of cleaning the inside of the engine by removing deposits and starting materials generated during high-temperature operation of the engine. Compounds include sulfonates, phenates, salicylates, and phosphonates, and metals include metal salts such as calcium, magnesium, and barium.

There are also ultrabasic detergents containing excessive amounts of hydroxides or carbonates of these metals. In the present invention, these metal detergents are blended as a metal amount of 0.01 to 0.5 parts by weight with respect to 100 parts by weight of base oil, and in addition to the conventional basic functions of detergency and acid neutralization, A new feature is that the friction and wear characteristics of the synchronizer ring and gear cone can be significantly improved. Although differences in the type of metal and organic moiety (e.g. sulfonate and phenate) have a slight effect on the friction and wear characteristics of the synchronizer ring and gear cone, both have the effect of increasing the coefficient of friction.
If a particularly high coefficient of friction is required, the amount of metal detergent added may be increased.

However, if 0.5 parts by weight or more is added, the coefficient of friction becomes too large, which is not preferable as an automotive gear oil. If the amount is less than 0.01 parts by weight, not only a high friction coefficient cannot be obtained, but also the above-mentioned effects such as cleaning and acid neutralization effects cannot be obtained.

Furthermore, (d) zinc dithiophosphate used in the present invention is used as an antioxidant and anti-wear agent in engine oil or hydraulic oil, and its chemical structure is expressed by the following formula: RIt R2t R :l+ R4 has 3 to 10 carbon atoms
It is said that just as the thermal decomposition temperature changes by changing the alkyl group and aryl group in this molecule, and the hydrocarbon group R in this molecule, the lubricating properties are also naturally affected. Although the friction and wear characteristics of the synchronizer ring and gear cone differ slightly depending on the number of carbon atoms and the presence or absence of branching of the alkyl group, it is possible to obtain good friction and wear characteristics by adjusting the amount added. In the present invention, R in the formula corresponds to a compound represented by C:l to CIO, where the amount of zinc dithiophosphate is 100% of the base oil.
The amount of zinc bone is 0.01 to 0.6 parts by weight relative to parts by weight, and if it is outside this range, no improvement in wear resistance or extreme pressure properties can be expected.

In addition, the above components (al, (bl, (c) and (d)
Even when 1 is used in combination, the performance of each component (a - d) can be exhibited as long as it is within the range of the above-mentioned blending amount.

As mentioned above, the substances added to the base oil in the present invention are known as lubricating oil additives.
By achieving a new combination of the extreme pressure performance of automotive gear oil and the maintenance of a high friction coefficient of a synchronized meshing mechanism device made mainly of copper alloy, the transmission, front differential, and center differential gear were integrated. It is possible to provide optimal performance as a common lubricant for wheel drive vehicles,
This was not possible with conventional gear oil compositions. With conventional Sulfur Hanato gear oil, even if it has the extreme pressure performance of GL-5, the durability of the synchronizer characteristics described below will deteriorate in a short period of time, and conversely, even if the synchronizer has the durability performance, the extreme pressure performance will deteriorate. It was not possible to combine both performances so that it would not reach the level of GL-5.

For example, removing the metal detergent and zinc dithiophosphate from the composition would not accomplish the above objectives.

Main Basis Next, the present invention will be explained with reference to examples, but the present invention is not limited thereto.

Example 1 Sulfurized olefin was added as a sulfur content of 2 to 100 parts of base oil.
．． 5 parts by weight of a mixture of the C18 alkylamine salt of a phosphoric acid ester substituted with one or two dihexylthiophosphoric acid groups and the above alkylamine salt of a phosphoric acid ester substituted with one or two dihexylpropyldithiophosphoric acid groups. Gear oil 1 was obtained by blending 0.15 parts by weight of phosphorus, 1.0 parts by weight of calcium sulfonate (containing 3 parts by weight of calcium concentration), and 2.0 parts by weight of sacrificial cyamyl dithioline (juice).

Example 2 The phosphorus content of Example 1 is 0.0 when the long chain (8 to 12) alkylamine salt of di- and monoalkyl ester of phosphoric acid is converted to phosphorus content.
Gear oil 2 was obtained by blending the additives of Example 1, except that the amount of phosphorus was changed to 3 parts by weight, and the amount of phosphorus was changed to 0.12 parts by weight of the phosphorus compound whose main component was an alkylamine salt of a phosphoric acid ester.

Example 3 Gear oil 3 was obtained by blending the additives of Example 1, except that 1.0 parts by weight of magnesium sulfonate (magnesium concentration: 9.5 parts by weight) was added instead of calcium sulfonate. .

Example 4 Gear oil 4 was prepared by blending the additives of Example 1 with the exception of adding 1.0 parts by weight of overbased calcium sulfonate (calcium concentration 12.5 parts by weight) instead of calcium sulfonate in Example 4. I got it.

Example 5 In Example 1, calcium sulfonate was replaced with calcium salicate (calcium concentration 6.0 parts by weight).
．． Gear oil 5 was obtained by blending the additives of Example 1, except that 0 part by weight was added.

Example 6 In Example 1, barium sulfonate (barium concentration: 14.2 parts by weight) was used in place of calcium sulfonate.
Gear oil 6 was obtained by blending the additives of Example 1, except that 0 part by weight was added.

Example 7 Gear oil 7 was obtained by blending the additives of Example 1, except that 1.5 parts by weight of zinc diisooctyldithiophosphate was added in place of zinc cyamyldithiophosphate in Example 1.

Example 8 Gear oil 8 was prepared by blending the additives of Example 1, except that 1.0 parts by weight each of zinc dibutyldithiophosphate and zinc dihexyldithiophosphate were added in place of zinc cyamyldithiophosphate in Example 1. Obtained.

Comparative example 1 Gear oil 9 Ichi UiGL-3 transmission gear oil (75W/90
). Typical properties are shown in Table 1.

Comparative Example 2 Gear Oil 10 GL-5 city version hypoid gear oil (No. 90). Typical properties are shown in Table 1.

Comparative Example 3 Gear oil 11 containing only 2.5 parts by weight of the sulfurized olefin of Example 1 as sulfur content and 0.15 parts by weight of phosphorus Comparative example 4 Example except that calcium sulfonate was removed from Example 1 Gear oil 12 was obtained by blending the additive of No. 1.

Comparative Example 5 Gear oil 13 was obtained by blending the additives of Example 1 except that zinc cyamyl dithiophosphate was removed.

For the gear oils 1 to 8 of the above-mentioned Examples and the gear oils of Comparative Examples 1 to 5, the synchronizer ring and gear cone were taken out of the automobile transmission, the gear cone was rotated at a constant rate, and the synchronizer ring was pressed with a constant load. For example, when the test pattern of pressing for 0.5 seconds and releasing for 0.5 seconds is repeated several thousand times, the friction coefficient of the comparative gear oils 10 and 11 decreases rapidly, the synchronization time increases, and at the same time the synchronizer ring wears out. progresses gradually. However, it is clear that the gear oils of Examples 1 to 7 have higher coefficients of friction and less wear on synchronizer rings than commercially available sulfur-phosphorus gear oils, and are suitable for lubricating synchronizers of transmissions. The effect of zinc dialkyldithiophosphate in the present invention is, for example, as can be seen from the results of Gear Oil 1 of Example and Gear Oil 13 of Comparative Example, which has the effect of significantly reducing the wear of synchronizer rings. Similarly, as for the effect of the metal detergent, for example, when comparing Gear Oil 1 of Example and Gear Oil 12 of Comparative Example 4, it can be seen that the coefficient of friction can be maintained high. Furthermore, by simultaneously blending a metal detergent and zinc dithiophosphate, it becomes possible to maintain a high coefficient of friction and at the same time reduce the amount of wear on the synchronizer ring, as shown in Example 1.

Next, it will be explained that the gear oil of the present invention not only improves the friction characteristics of the synchronizer ring and gear cone, but also has excellent extreme pressure performance. Extreme pressure performance test is conducted by US CRCL-
It has a test method and severity level equivalent to that of the domestically produced 16
The hypoid gear installed in the 00CC car was used. Note that hypoid gears with no surface treatment were used for testing. The numbers in Table 1 indicate the area where scoring occurs in the ring gear and drive pinion gear. For example, Comparative Gear Oil 1 with extreme pressure performance of GL-5
0 with each Example gear oil, the scoring area is equal to or greater than Comparative Example Gear 10, and it can be said that it clearly has the extreme pressure performance of GL-5.

On the other hand, the transmission oil of Comparative Example Gear Oil 9 has a considerably large scoring area and has an extreme pressure performance of less than GL, -5.
Even if synchronizers can be lubricated, it cannot be applied to hypoid gears that require high extreme pressure performance.

The effects of the metal detergent and zinc dithiophosphate on extreme pressure performance in the present invention are as follows: Gear oil 1 in Example 1 and Comparative Example 9
As is clear from the comparison with U, the addition of a metal detergent reduces the extreme pressure performance to some extent.

On the other hand, a comparison of gear oil 11 of Comparative Example 3 and gear oil 12 of Comparative Example 4 revealed that zinc dithiophosphate did not impede extreme pressure performance but had the effect of slightly improving it. Further, even if a metal detergent and zinc dithiophosphate are co-existed in a sulfur-phosphorus extreme pressure agent as in the present invention, the extreme pressure properties of the sulfur-phosphorus extreme pressure agent are not reduced, but rather are improved.

Table 1 shows the properties, friction, wear characteristics, and extreme pressure characteristics of the example gear oil and the comparative example gear oil. Furthermore, the extreme pressure performance test conditions are shown in Table-2.

As mentioned above, the gear oil composition of the present invention combines a conventional sulfur phosphorus-based extreme pressure agent with a metal detergent and zinc dialkyldithiophosphate, so that it is not as simple as a conventional gear oil. A gear oil that not only satisfies pressure performance but also has good friction and wear characteristics for the mesh synchronization mechanism, which is essential as a common lubricant for the transmission, front differential, and rear axle hypoid of 4-wheel drive vehicles due to the combination of additives. It is a composition.

[Brief explanation of the drawing]

Attached drawing 1 is a graph plotting the coefficient of friction in repeated friction tests of the synchronizer ring and gear cone parts of gear oil 1 of Example 1, gear oil 9 of comparative example, and gear oil 1O for each number of repetitions of pressing. .

Claims (1)

[Scope of Claims] Based on 100 parts by weight of the base oil, (a) 0.5 to 4 parts by weight of sulfurized olefin as a sulfur content, (b) an alkyl phosphoric acid compound, an alkylthiophosphoric acid compound, and an alkyl dithiophosphoric acid compound. 0.02 to 0.2 parts by weight of at least one selected from the group consisting of phosphorus; (c) 0.01 to 0.2 parts by weight of a metallic detergent;
5 parts by weight and (d) zinc dialkyldithiophosphate as zinc amount 0.0
An automotive gear oil composition comprising 4 to 0.6 parts by weight.