JPH05105895A - Lubricating oil composition for wet clutch or wet brake - Google Patents

Abstract

PURPOSE:To obtain the title composition having a high coefficient of dynamic friction and a high coefficient of static friction and improved in power transmission efficiency by incorporating a specified aliphatic compound into a lube base oil for a wet clutch or brake. CONSTITUTION:A lube base oil for a wet clutch or brake having a kinematic viscosity at 100C of 1-80cSt is mixed with 0.01-10 pts.wt. 2-14C aliphatic compound having at least two hydroxyl groups.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition of a lubricating oil used for a wet clutch or a wet brake of a power transmission device in automobiles, agricultural machines, construction machines and other industrial machines.

[0002]

2. Description of the Related Art Wet clutches and wet brakes in the above-mentioned various types of machines both transmit or control rotational force by friction between a disk and a plate. Friction properties are a very important requirement. In the explanation below,
As an example, the description will be given using a wet clutch.However, if the friction characteristics are not suitable, power transmission loss in the clutch or comfort during driving of the vehicle will be greatly affected, so it is important to obtain proper friction characteristics. Come on.

Conventionally, the friction modifier plays an extremely important role in the lubricating oil for the wet clutch (or for the wet brake) in the above-mentioned various machines and has been used in various ways. There are two types of friction adjustment of a wet clutch in a power transmission device for passenger cars, which increases a dynamic friction transmission torque (a friction coefficient is called a dynamic friction coefficient and is generally expressed as μd) to increase the friction transmission when the wet clutch is engaged. It is necessary to reduce the torque (which is called the static friction coefficient as a friction coefficient and is generally expressed as μo). If the ratio of the dynamic friction coefficient to the static friction coefficient is greater than 1, a shift shock occurs during a shift, causing discomfort.
On the other hand, when the ratio is 1 or less, there is no shift shock and comfortable shift characteristics are obtained.

It is a friction modifier that adjusts this frictional characteristic, and the above ratio can be set to 1 or less by mixing an appropriate friction modifier with the lubricating oil. However, when a friction modifier is blended, the static friction coefficient (μo) may decrease, and at the same time, the wet clutch may slip due to fluctuations in engine power after the wet clutch is completely engaged.
This is generally distinguished from the static friction coefficient (μo). Therefore, the static friction coefficient (μ
(expressed as s). This static friction coefficient (μ
s) responds sharply by blending a friction modifier, and may lower the coefficient of static friction (μs). The static friction coefficient (μs) generally shows a high value when the dynamic friction coefficient (μd) is high.

Therefore, it is desirable to add a friction modifier to an additive composition for increasing the dynamic friction coefficient (μd) to adjust the static friction coefficient (μs) and the static friction coefficient (μo). Conventionally, in order to increase the dynamic friction coefficient (μd), for example, an alkenyl succinimide dispersant, a borated alkenyl succinimide dispersant, a Mannich-based ashless dispersant or calcium sulfonate, magnesium sulfonate, etc., a lubricating oil. In the field of (1), additives called detergent dispersants have been compounded. However, when these additives are blended in a large amount, other performances such as oxidative stability,
May adversely affect copper corrosion stability. In addition, in order to obtain appropriate frictional characteristics, various innovations are required as a compounding technique.

Further, in recent years, in order to achieve fuel efficiency in automatic transmissions for passenger cars, a device for mechanically transmitting power by using a lock-up clutch to prevent power transmission loss due to friction loss of fluid is used. It started to come. A wet clutch is also used here, and if friction characteristics are not suitable, self-excited vibration caused by stick-slip may occur, possibly resulting in damage to the machine.

Generally, in order to suppress this self-excited vibration, a large amount of a friction modifier is blended or a strong friction modifier is used. A static friction coefficient (μ
s) is greatly affected and decreases, leading to power transmission loss. Therefore, suppressing self-excited vibration while maintaining a high coefficient of static friction (μs) is a contradictory phenomenon, and making both of these performances compatible is a major issue in this field. Moreover, since the friction modifier deteriorates during use and gradually loses the self-excited vibration suppressing ability, the sustainability of the self-excited vibration suppressing ability has become an important issue.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a lubricating oil for a wet clutch or a wet brake, which has a particularly high dynamic friction coefficient and static friction coefficient. The gist is that the aliphatic compound having 2 to 14 carbon atoms and having 2 or more hydroxyl groups is added in an amount of 0.01 to 100 parts by weight of the base oil of the lubricating oil for wet clutches or wet brakes. It exists in a lubricating oil composition for a wet clutch or a wet brake, which is blended at a ratio of 10 parts by weight.

As the base oil which is the main component of the lubricating oil of the present invention, any one which can be used as a lubricant for wet clutches or wet brakes can be used without any particular limitation. Mineral oil, synthetic oil or those A mixture of 10
The kinematic viscosity at 0 ° C. is 1 to 80 cSt (centistokes), preferably 2 to 50 cSt. Mineral oil,
That is, the mineral oil-based lubricating oil fraction includes paraffin-based crude oil, naphthene-based crude oil, and mineral oil obtained by distilling and refining paraffin-naphthene-based crude oil according to a conventional method. Mineral oil having a viscosity index is used. As synthetic lubricating oil, poly-α-olefin, polybutene, dibasic acid ester, polyglycol,
Various synthetic oils such as hindered esters, alkylbenzenes and polyethers can be used. Also, a mixture of the above mineral oil and synthetic oil can be used.

In the lubricating oil of the present invention, the aliphatic compound blended in the base oil is one having two or more hydroxyl groups, that is, a polyhydric alcohol such as diol, triol, tetraol and having 2 to 2 carbon atoms. It has 14 pieces. The hydrocarbon group of this compound may be a straight chain or an aliphatic hydrocarbon group having a branched chain. As the hydrocarbon group, an unsaturated hydrocarbon or an alkylallyl group can be used, but in general, a saturated hydrocarbon group is preferable from the availability of raw materials. Specifically, as the diol, 1,3-propanediol,
1,2-butanediol, 1,3-butanediol,
1,4-butanediol, 1,2-hexanediol,
2,4-hexanediol, 2,4-octanediol, 1,3-dodecanediol and the like can be mentioned. Also,
For triols, tetraols and higher polyhydric alcohols, in addition to their simple substance, at least 2
Those in which one hydroxyl group is left and other hydroxyl groups are esterified, that is, those in the form of monoester or diester compounds can also be used.

Specifically, when glycerol, trimethylolpropane or the like is used as the triol, its monohexylate, monooctylate or the like can be mentioned. The same applies to pentaerythritol as tetraol. Among these polyhydric alcohols such as diols, triols and tetraols, short-chain polyhydric alcohols having a carbon chain of 3 to 11 carbon atoms are preferable. As described above, the aliphatic polyol compound to be added to the base oil is
It is blended in a proportion of 0.01 to 10 parts by weight with respect to 100 parts by weight of the base oil.

Further, in the lubricating oil composition of the present invention, in addition to the above essential components, an antioxidant, a detergent dispersant, an extreme pressure agent, a friction modifier, an oiliness agent, in order to improve the performance as a lubricating oil.
Additives that are normally used, such as a corrosion inhibitor, a rust preventive agent, a rubber swelling agent, a defoaming agent, a pour point improver, and a viscosity index improver, are appropriately mixed.

As the antioxidant, a phenol-based antioxidant, an aromatic amine-based antioxidant, zinc dithiophosphate, etc. are used, and specifically, 2,6-di-t-butyl-4-methylphenol, 4,4'-methylenebis (2,6-di-t-butylphenol), phenyl-α-naphthylamine, dialkyldiphenylamine, zinc di-2-ethylhexyldithiophosphate, zinc diamyldithiocarbamate, pinene pentasulfide and the like can be mentioned. These antioxidants are 0.01 to 2% by weight, based on mineral oil, preferably 0.1%.
It is mixed in the range of 05 to 1% by weight.

Examples of the detergent dispersant include ashless dispersants, metal detergents, etc., and ashless dispersants containing boron, and JP-A-2-140299 (USP 4,857,
214) or PCT publication WO 90 09,
The dispersants described in 425 can also be used. Specific examples include alkenyl succinimide, metal sulfonate, metal finate, metal salicylate, and the like. These are blended in the range of 0.01 to 10% by weight, preferably 0.5 to 5% by weight, based on the mineral oil.
In addition, each of the above-mentioned various additives is specifically added in an appropriate amount in the preparation of a lubricating oil for wet clutches or wet brakes.

The lubricating oil obtained as described above provides excellent friction characteristics, particularly high dynamic friction coefficient (μd) and high static friction coefficient (μs) in wet clutches and wet brakes. The lubricating oil of the present invention exhibits a sufficiently effective action as shock absorber oil, power steering oil, hydraulic suspension oil and the like.

[0016]

EXAMPLES Next, examples of the present invention will be described. The performance evaluation of the lubricating oils obtained in the examples was based on the following test methods. (1) SAE No. 2 friction tester; using this tester,
Evaluation was performed under the following test conditions. Disc: Paper type disc for automatic transmission, Plate: Steel plate for automatic transmission, Motor speed: 3000 rpm, Dynamic friction coefficient (μd) is 1200 rpm (indicated as μ1200 in the table below), and clutch engagement point The coefficient of friction was measured as the coefficient of static friction (μo). Piston pressing pressure: 49 rsi, oil temperature: 110 ° C. Further, in order to obtain the static friction coefficient (μs), the maximum friction coefficient when engaged at 0.7 rpm was measured as μs. μ
The higher d and μs are, the better, and those having μo / μd ≦ 1.1 are preferable. It is more preferable that μo / μd ≦ 1.0.

(2) LVFA (single plate low speed friction tester);
In order to evaluate the stick-slip suppressing ability, a friction coefficient-slip velocity relationship is obtained. Disc: Paper type disc for automatic transmission (1 sheet), Plate: Steel plate for automatic transmission (1 sheet) Surface pressure: 10 kg / cm ² , Oil temperature: 40 ° C Motor speed: Intermittent from 1 to 100 rpm Change to each rotation speed.

The friction coefficient (μ) with respect to the sliding speed (v) is obtained by changing the rotation speed. If dμ / dv ≧ 0, the self-excited vibration is suppressed. Here, for the sake of convenience, the friction coefficient at a rotation speed of 1 rpm is set to μ1, and similarly at 100 rpm, it is set to μ100. By using this ratio μ1 / μ100 as an index, a lubricating oil having μ1 / μ100 ≦ 1 has a preferable self-excited vibration suppressing ability. Also, this LVF
In A, the ratio of μ1 / μ100 is also important, but if the absolute value of μ1 decreases, the clutch slips,
The value of μ1 is preferably as high as possible.

(3) Oxidation stability test: Comparison was made under the conditions of 165.5 ° C. and 120 hours in accordance with the oxidation stability test (JIS K-2514) of the lubricating oil for internal combustion engines. (4) Copper corrosion test; in accordance with JIS K-2513,
It processed at 150 degreeC for 3 hours, and evaluated the corrosion state after that.

Example 1 and Comparative Example 1 A mineral oil having a kinematic viscosity of 4.5 cSt at 100 ° C. was used as a base oil, and the following additives were blended in the indicated numerical ratios to prepare a base oil. The one with this composition is
Basic oil A. Detergent dispersant Polyisobutenyl succinimide type 5.0 Antioxidant Hindered phenol type 0.5 Extreme pressure agent Hydroenphosphite 0.5 Friction modifier amide type 0.5 Oiliness agent Sulfurized oil and fat 1.0 Corrosion inhibitor Benzotriazole 0.05 Defoamer Polydimethylsiloxane kerosene solution 0.05 Viscosity index improver Polymethacrylate 6.0 Base oil Mineral oil 86.4 The unit of the above mixing ratio is% by weight.

In Example 1, 1,3-
Butanediol is blended, and the blending ratio is 0.23 parts by weight with respect to 100 parts by weight of mineral oil in the base oil A. For comparison with this, Comparative Example 1 had the same composition as in Example 1 except that 1,3-butanediol was not added at all. The friction characteristics of these lubricating oils were measured, and the results are shown in Table 1.

Example 2 and Comparative Example 2 In these examples, the base oil A used in Example 1 above was modified by boration in place of 5.0% by weight of its detergent-dispersant polyisobutenylsuccinimide system. The same composition as the base oil A was used except that 5.0% by weight of polyisobutenyl succinimide type was used. This composition is hereinafter referred to as "Basic oil B", and its composition is as follows. Detergent dispersant Borated polyisobutenyl succinimide type 5.0 Antioxidant Hindered phenol type 0.5 Extreme pressure agent Hydroenphosphite 0.5 Friction modifier amide type 0.5 Oiliness agent Sulfurized oil and fat 1 .0 Corrosion inhibitor benzotriazole 0.05 Defoaming agent Polydimethylsiloxane kerosene solution 0.05 Viscosity index improver Polymethacrylate 6.0 Base oil Mineral oil 86.4 The unit of the above mixing ratio is% by weight. ..

In Example 2, 1,3-
Butanediol was blended, and the blending ratio was 0.23 parts by weight with respect to 100 parts by weight of the mineral oil in the base oil B. For comparison with this, Comparative Example 2 was prepared without adding 1,3-butanediol at all and having the same composition as in Example 2 except for the above. The frictional properties of these were measured, and the results are shown in Table 1. From the results in Table 1,
The composition of 1,3-butanediol was μd (in Table 1, μ1
(Indicated by the display of 200) and μs is apparent.

[0024]

[Table 1]

Example 3 and Comparative Example 3 and Example 4 and Comparative Example 4 In Example 3, the base oil A used in Example 1 was used, and 2,4-hexanediol was added thereto. The mixing ratio was 0.47 parts by weight with respect to 100 parts by weight of the mineral oil in the base oil A. For comparison with this, Comparative Example 3 had the same composition as that of Example 3 except that the 2,4-hexanediol was not blended at all.

In Example 4, the base oil B used in Example 2 was used, and 2,4-hexanediol was added to the base oil B, and the mixing ratio was 10% of the mineral oil in the base oil B.
It was 0.47 parts by weight with respect to 0 parts by weight. In contrast to this, no 2,4-hexanediol was added,
Other than that, Comparative Example 4 has the same composition as that of Example 4. Example 3, Comparative Example 3, Example 4 and Comparative Example 4 above
The friction characteristics of the lubricating oil of No. 1 were measured, and the results are shown in Table 2. The results in Table 2 also clearly show the improvement effect of μd (μ1200) and μs by blending 2,4-hexanediol.

[0027]

[Table 2]

Examples 5 and 6 This example shows an example in which the blending ratio of the aliphatic compound blended in the lubricating oil of the present invention was increased. That is, in Example 4 above, 2,4-hexanediol was added to the base oil B, and 0.47 was added to 100 parts by weight of the mineral oil in the base oil B.
The amount was 0.7 parts by weight in Example 5, and 0.93 parts by weight in Example 6. The properties of the obtained lubricating oil are shown in Table 3. Note that Table 3 also shows the measured values of Example 4 for easy comparison. From the results in Table 3, as the blending ratio of 2,4-hexanediol is increased, the increase in μd (μ1200) is slight, but the increase in μs is remarkable, and μo / μ1200
As a result, the power transmission efficiency can be improved while maintaining preferable friction characteristics.

[0029]

[Table 3]

Examples 7 and 8 and Comparative Example 5 In this example, the properties of the lubricating oil were measured by an LVFA (Single Plate Low Speed Friction Tester). In Example 7, the base oil B
Is a lubricating oil in which 2,4-hexanediol is blended at a ratio of 0.47 part by weight to 100 parts by weight of mineral oil in the base oil B. Example 8 is the same as the base oil B.
0.94 parts by weight of 2,4-per 100 parts by weight mineral oil in
Hexanediol was added, and Comparative Example 5
It is a lubricating oil consisting only of base oil B to which 2,4-hexanediol is not added at all. The results are shown in Table 4.

[0031]

[Table 4]

As can be seen from Table 4 above, when the addition ratio of 2,4-hexanediol is increased with respect to the base oil B having the same composition, the values of μ1 and μ100 remarkably increase, but μ1 The ratio of / μ100 hardly changed, and showed an improving effect in the single plate low speed friction test. That is, if a friction modifier is added to achieve the suppression of stick-slip, μ1 will decrease, causing the problem of slipping on the low speed side, whereas the addition of the polyol aliphatic compound of the present invention will lead to good sticking. While showing the ability to suppress slip, μ
By increasing the absolute value of 1, the effect of suppressing the slip phenomenon on the low speed side can be achieved.

Example 9 and Comparative Examples 6 and 7 One of the improvements of the present invention is the durability of suppressing self-excited vibration. This example demonstrates the improvement in durability of the stick-slip suppressing ability. Comparative Example 6
The lubricating oil of No. 1 is obtained by changing a part of the basic oil B mentioned in the above-mentioned Example 2 as the basic oil. That is, as the friction modifier, an ester-amide mixture type was used instead of the amide type, and the compounding ratio was not changed and was 0.5% by weight. This composition is referred to as Basic Oil B (Modification 1). The lubricating oil of Comparative Example 6 consisted only of this basic oil B (Variation 1) and did not contain the aliphatic polyol compound of the present invention.

The lubricating oil of Comparative Example 7 is obtained by further changing a part of the basic oil B (deformation 1). That is, the same ester-amide mixture system is used as the substance of the friction modifier in the base oil B (variant 1), but the blending amount is 1.
0% by weight, 0.5% by weight of mineral oil in the base oil 8
5.9% by weight [this base oil is base oil B
(Variation 2)]. The lubricating oil of Comparative Example 7 was composed only of the base oil B (Variation 2), and the aliphatic polyol compound of the present invention was not blended. The lubricating oil of Example 9 is different from the base oil B (deformation 2) of Comparative Example 7 in the base oil B (deformation 2).
0.47 parts by weight of 2,4-based on 100 parts by weight of mineral oil
Hexanediol is compounded.

With respect to the lubricating oils of Comparative Examples 6 and 7 and Example 9, μ0, μ1 were measured by a SAE No. 2 friction tester.
200 (μd), μs and μo / μ1200 were measured. The results are shown in Table 5.

[0036]

[Table 5]

With respect to each of the lubricating oils of the above Comparative Examples and Examples, the values of μ1 and μ100 were measured by an LVFA tester with the one before the durability test (this is called a new oil), and the ratio value of μ1 / μ100 was measured. Ask for. Then, the same composition as each lubricating oil is subjected to the durability test as follows. That is, the sample to be measured was subjected to the same test conditions as described above (motor rotation speed 3000 rpm, piston pressing pressure 40 psi, by SAE No. 2 friction tester,
The load is applied at an oil temperature of 110 ° C.), the load is released after 30 seconds have elapsed, and then the load is applied for another 30 seconds, which is repeated 10,000 times, and the test is completed. After this test, for each sample, μ1 and μ10 were used by using the used disk, plate and oil after endurance by the LVFA tester.
0 is measured and the value of the ratio of μ1 / μ100 is obtained. The test results are shown in Table 6.

[0038]

[Table 6]

The following is clear from Table 6 above. That is, as seen in Comparative Example 6 in Table 6, the lubricating oil of Comparative Example 6 greatly changed in the ratio of μ1 / μ100 before and after the durability test by the SAE No. 2 tester (0.97 → 1.0).
7), self-excited vibration was suppressed in the new oil before the durability test by SAE No. 2 tester, but self-excited vibration occurred after the test. Then, in order to examine the effect of the addition amount of the friction modifier on the suppression of self-excited vibration, a lubricant containing double the amount of the friction modifier was prepared as the lubricating oil of Comparative Example 7, and a durability test was conducted on this oil to prepare a new oil and Μ1 after each endurance test
The ratio of ˜ / μ100 is calculated in the same manner as in the previous example.
As can be seen from the above, the change in the value of μ1 / μ100 is small, and it is understood that the sustainability of the self-excited vibration suppressing ability is improved by increasing the amount of the friction modifier added.

However, from the comparison of the static friction coefficients (μs) of Comparative Example 6 and Comparative Example 7 in Table 5 above, when the compounding amount of the friction modifier is increased, this μs value decreases (0.130 →
0.120), it is understood that there is a problem that the transmission efficiency in the power transmission device is reduced.

On the other hand, the lubricating oil of Example 9 had the same proportion of the friction modifier as that of Comparative Example 7, but had a composition containing the aliphatic polyol compound of the present invention.
The lubricating oil of this Example 9 had μ1 / μ before and after the durability test.
The change in 100 ratio is small as in Comparative Example 7, while the μs value is higher than that in Comparative Example 7 as seen in Table 5. That is, it is understood that the aliphatic polyol compound of the present invention does not affect the self-excited vibration suppressing ability after the durability test. From these results, the aliphatic polyol compound of the present invention can use a large amount of the friction modifier without sacrificing the static friction coefficient, that is, without sacrificing the power transmission efficiency by the blending thereof, and as a result, self-excited. It is possible to improve the sustainability of vibration suppression.

Example 10 and Comparative Example 8 In these examples, for each sample, the oxidation stability test according to JIS K-2514 and JIS were carried out as described above.
The result of having performed the copper corrosion test by K-2513 is shown.
The lubricating oil of Example 10 comprises the above base oil B and 2,4-hexanediol in an amount of 0.58 parts by weight based on 100 parts by weight of mineral oil in the base oil B. The lubricating oil of Comparative Example 8 is
It is composed only of the base oil B without the addition of 2,4-hexanediol. The test results are shown in Table 7.

[0043]

[Table 7]

From the results shown in Table 7, it is recognized that the aliphatic polyol compound of the present invention does not have any adverse effect on the oxidation stability and the copper corrosiveness when it is compounded.

[0045]

INDUSTRIAL APPLICABILITY The lubricating oil composition of the present invention provides a high dynamic friction coefficient (μd) and a high static friction coefficient (μs) in wet clutches and wet brakes, which improves the power transmission efficiency, resulting in a power transmission device. The miniaturization and fuel saving are expected. In addition, in a wet clutch lubricating oil or the like, if the ratio (μo / μd) of the coefficient of static friction (μo) to μd is large, discomfort occurs during shifting. Although the μd ratio is improved, at the same time, there is a problem that μs is reduced. When the aliphatic polyol compound in the present invention is added, it can reduce μo / μd and can obtain a lubricating oil having a high μs.

Further, in order to save fuel consumption in recent years, a lock-up clutch has been introduced in an automatic transmission, but if the relationship between the sliding speed and the coefficient of friction is poor, self-excited vibration occurs and a problem occurs. Friction modifiers contribute to the improvement of this relationship, and usually a large amount of friction modifier is used or a highly effective friction agent is added. However, in this case as well, although μs is decreased as described above, the addition of the aliphatic polyol compound of the present invention
The above relationship can be improved while maintaining a high μs.

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Claims (1)

[Claims] 1. 0.01 to 10 parts by weight of an aliphatic compound having 2 to 14 carbon atoms and having 2 or more hydroxyl groups with respect to 100 parts by weight of a base oil of a lubricating oil for wet clutches or wet brakes. A lubricating oil composition for a wet clutch or a wet brake, which is blended in a ratio of 1 part.