JPH0434590B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention can be applied to lubrication points such as constant velocity joints (CVJs) in automobiles, which have high surface pressure, are prone to wear, and are likely to generate abnormal vibration torque, to efficiently lubricate them. The present invention relates to a grease for constant velocity joints that can effectively prevent wear and vibration. (Prior technology) Conventionally, lithium-based extreme pressure grease containing sulfur-phosphorus-based extreme pressure additives and molybdenum disulfide were used for lubrication points that are subject to high surface pressure, are prone to wear, and are prone to vibration. Lithium-based extreme pressure grease, etc., is used. (Problem to be solved by the invention) Under such lubrication conditions, oil tends to run out on the lubricated surface, resulting in wear and abnormal wear vibration, which further accelerates wear and damages the lubricated parts. Shortening lifespan has become a problem. For this reason, measures have been taken to prevent oil from running out by adding solid lubricants such as molybdenum disulfide to greases used under such lubrication conditions, but these are not sufficient, and this results in poor lubrication and accelerated wear. The current situation is such that parts have to be replaced at an early stage. In particular, for constant velocity joints (CVJs) in automobiles, greases need to have improved wear resistance and vibration prevention, as well as smaller and lighter CVJs and increased heat resistance due to the tendency for engine rooms to become hotter. There is. (Means for solving the problem) We will first conduct research on greases with good wear resistance to be used under such lubrication conditions that are subject to high surface pressure and are prone to wear and vibration. We have repeatedly investigated additives and solid lubricants and their combined effects. On the other hand, as a method for evaluating wear resistance, the wear coefficient was measured at various loads ranging from low loads to high loads, and evaluation of the effects of adding each of the above-mentioned additives was studied. As a result, the previously used greases containing molybdenum disulfide and sulfur-phosphorus extreme pressure additives have a small friction coefficient at low loads, but at high loads, that is, 3 kg (hydraulic pressure) in the Soda 4-ball tester. Under such high load (high surface pressure) conditions, the coefficient of friction increases. Tests on actual machines have shown that such grease has problems with wear resistance. Next, in order to solve this problem, we tried various additives to improve the additives, and unexpectedly, we used (A) molybdenum sulfide dialkyldithiocarbamate as a solid lubricant, and a sulfur-phosphorus extreme pressure Using (B) sulfurized oil, sulfurized olefin, tricresyl phosphate, trialkylthiophosphate, and zinc dialkyldithiophosphate as additives,
By containing specific amounts of both components (A) and (B) in the grease, it was confirmed that the resulting grease behaves under the above-mentioned high loads with a small coefficient of friction that is almost the same as under low loads. We found that the grease has excellent wear resistance in actual machine tests, and as a result, can prevent the occurrence of abnormal wear vibrations. Furthermore, under high loads, the coefficient of friction is small, the wear resistance is excellent, and vibrations can be prevented. We continued to consider greases that also have excellent heat resistance and tested various types of grease.The results showed that using urea grease as the base grease satisfied all of the characteristics required for CVJ grease. I also learned that it was appropriate for the purpose. That is, the present invention provides a urea grease containing (A) molybdenum sulfide dialkyldithiocarbamate, and (B) sulfurized oil, sulfurized olefin, tricresyl phosphate, trialkylthiophosphate, and zinc dialkyldithiophosphate. Contains as an essential component a sulfur-phosphorus extreme pressure additive consisting of one type or a combination of two or more types, and
The present invention relates to a grease for constant velocity joints, characterized in that the content of component (A) is 0.5 to 10% by weight, and the content of component (B) is 0.5 to 10% by weight. (Function) The urea grease used in the present invention uses refined mineral oil, synthetic oil, or a mixture thereof as the base oil and a urea compound as the thickening agent, and has excellent heat resistance. Urea grease is necessary for applications that also require heat resistance, such as urea grease. Next, molybdenum sulfide dialkyldithiocarbamate, which is component (A) used in the present invention, is expressed by the following formula (1): (R ₁ and R ₂ in the formula represent an alkyl group having 1 to 24 carbon atoms, and m + n = 4, and m is 0 to 3, n
is 4-1. ) is a well-known solid lubricant. The compound of formula (1) is, for example,
−24562, where m is 2.35
~3, n is 1.65 to 1, m is 0 and n is 4 in the one disclosed in Japanese Patent Publication No. 51-964, and m is 0.5 to 2.3, n is disclosed in Japanese Patent Publication No. 53-31646. is 3.5
~1.7 have been disclosed. The compounds of formula (1) used in the present invention include all those disclosed above. That is, compounds of formula (1) with a large value of n, that is, with a large sulfur content, have high extreme pressure properties, but also have high corrosiveness to metals. The opposite is true for small n. In the present invention, depending on the lubrication conditions, a more severe one gives priority to extreme pressure properties, and a relatively mild one gives priority to corrosiveness, and is appropriately selected to achieve the desired effect. Further, the sulfur-phosphorus extreme pressure additive used in the present invention is one or two selected from the group consisting of sulfurized oils and fats, sulfurized olefins, tricresyl phosphates, trialkylthiophosphates, and zinc dialkyldithiophosphates. This is a sulfur-phosphorus-based extreme pressure additive consisting of the above combination, and is an extreme pressure additive containing both sulfur and phosphorus. Therefore, sulfurized oils and fats, which are sulfur-based extreme pressure additives that only contain sulfur,
When using sulfurized olefin and tricresyl phosphate, which is a phosphorus-based extreme pressure additive containing only phosphorus, it is necessary to use both in combination. Both trialkyl thiophosphate and zinc dialkyl dithiophosphate are sulfur-phosphorus extreme pressure additives, so they can be used alone. The present invention is characterized in that component (A), molybdenum sulfide dialkyldithiocarbamate, and component (B), a specific sulfur-phosphorus extreme pressure additive, are combined in a specific amount ratio and are contained in the grease. Sideways
It achieves the objective by exhibiting a much better effect than when the components (A) and (B) are contained alone. This unique effect that can only be obtained when both components (A) and (B) are contained together has been confirmed through repeated experiments, and as shown in Table 1, the following test method is used. Friction coefficient in wear resistance evaluation test and vibration acceleration G in vibration test
In the case of the examples containing both components (A) and (B), the numerical value is 1/2 to 1/3 of that in the case of containing only one component. Furthermore, the effect was obtained that vibration and wear in CVJ vibration tests were completely undetectable. This is a unique effect that can only be obtained when both components (A) and (B) coexist, and this was discovered for the first time by the present invention as a result of research. However, the reason why such an effect is obtained is unknown. I haven't found any proof, but I'm thinking about it for next time. Molybdenum dialxydithiocarbamate sulfide, component (A), used in the present invention has dithiocarbamate in its molecule, like dithiocarbamates such as zinc dialxydithiocarbamate, which have been conventionally known as dithiocarbamate-based vulcanization accelerators for rubber. Since it has a structure in which the metal part in the molecule is molybdenum, which is effective for lubrication, it is naturally thought that it also has a vulcanization accelerator effect. Here, the vulcanization accelerator effect is an effect of activating sulfur and rubber hydrocarbons to promote crosslinking reactions between hydrocarbon molecules due to sulfur. Therefore, in the breath of the present invention, component (A) of molybdenum dibenzyldithiocarbamate and (B)
When component sulfur-phosphorus extreme pressure additives coexist, component (B) both contains sulfur and phosphorus and also has hydrocarbon groups, so the action of component (A) causes the increase in component (B). The sulfur and hydrocarbon groups are activated and a crosslinking reaction occurs between molecules to produce a polymer, which coats the metal part of the lubricated surface to form a viscoelastic polymer film that absorbs vibrations and prevents metal contact. On the other hand, it is known that phosphorus is an additive that reduces the coefficient of friction on lubricated surfaces. It is quite conceivable that the above-mentioned unique effects can be obtained only by a combination of ingredients. Addition amounts of less than 0.5% by weight of component (A) and less than 0.5% by weight of component (B) have no effect; on the other hand, (A)
Adding more than 10% by weight of the component, and adding more than 10% by weight of the component (B), does not increase the effect any further, and an excessive amount of the component (A) may cause side effects such as increased corrosiveness. Component (A) 0.5-10
The required range is 0.5 to 10% by weight of component (B). In addition to both components (A) and (B), if necessary, solid lubricants such as molybdenum disulfide and graphite,
N,N'-trimethylenediamine dioleate,
Rust inhibitors such as sorbidan monooleate, and antioxidants such as phenylalphanaphthylamine and 2,6-dithyabutyl para-cresol can also be included as optional components. (Example) Technical means used to solve the problems will be specifically explained using the examples and comparative examples shown in Table 1. 1 The ingredients of the base grease shown in the composition column of Table 1 are as follows. A. Urea grease Using refined mineral oil with a viscosity of 10cst at 100℃ as the base oil, react diphenylmethane-4,4'-diisocyanate and stearylamine in the base oil, and adjust the resulting urea compound content to 20% by weight. Urea grease made by uniformly dispersing in base oil. B Lithium Grease 12-Hydroxystearic acid and lithium hydroxide are heated and reacted in the same base oil as in Section A, and the resulting lithium-12-hydroxystearate is added to the base oil at a content of 8% by weight. Lithium grease that is uniformly dispersed. C Calcium grease 12-hydroxystearic acid and calcium hydroxide are reacted by heating in the same base oil as in Section A, and the resulting calcium-12-hydroxystearate is added to the base oil at a content of 8% by weight. Calcium grease that is uniformly dispersed. 2 The methods for preparing the samples of Examples 1 to 5 and Comparative Examples 1 to 10 are as follows. Molybdenum sulfide dialkyldithiocarbamate and a sulfur-phosphorus extreme pressure additive were added to the base grease in the proportions (% by weight) shown in Table 1 and kneaded to obtain a uniform composition, which was then used as a sample. 3 The test methods shown in Table 1 are as follows. A Wear resistance evaluation test method Each sample was applied to the friction surface of the test ball of the Soda 4-ball tester, and the test was performed step by step.
The friction coefficient was measured at an oil pressure of 3 kg/cm ² by increasing the load using the method. B. Vibration Test Each sample was applied to the speed change gear surface of a geared motor of the following type, and an acceleration type sensor was attached to the upper part of the gear case to measure the acceleration G of vibration. Motor 0.75KW 4P Input speed 1800rpm Output speed 60rpm Reduction ratio 1/30C CVJ vibration test 1 Presence or absence of vibration Each sample was applied to the lubricated part of CVJ and operated for 8 hours under the following conditions. The presence or absence of vibration was determined by touch 1 hour and 5 minutes after the start of operation. CVJ model: 95 bar field type joint Rotation speed: 1800rpm Joint angle: 10 degrees Torque: 20Kgf-m 2 Wear condition Apply each sample to the lubricated part of CVJ and operate under the same conditions as in the previous section for 8 hours, then check the wear condition of the lubricated surface. Judgment was made visually.

【table】

[Table] (Effects of the invention) As shown in Table 1, this is a grease for constant velocity joints that is based on urea grease and contains a specific amount of molybdenum sulfide dialkyldithiocarbamate and a specific sulfur-phosphorus extreme pressure additive. The present invention has a small coefficient of friction under high surface pressure, and when applied to lubricate the transmission gear surface of a geared motor, there is little vibration. When applied to an actual CVJ machine, it can effectively prevent vibration and wear. It was found that the heat resistance was higher than that of the comparative examples using lithium grease and calcium grease, and that the heat resistance was excellent, confirming that the original purpose of the present invention was achieved.

Claims (1)

[Scope of Claims] 1 Urea grease containing (A) molybdenum sulfide dialkyldithiocarbamate, and (B) sulfurized oil, sulfurized olefin, tricresyl phosphate, trialkyl thiophosphate, and zinc dialkyldithiophosphate. A sulfur-phosphorous extreme pressure additive consisting of one selected type or a combination of two or more types is contained as an essential component, and the content of component (A) is 0.5 to 10% by weight, and the content of component (B) is 0.5 to 10% by weight. Grease for constant velocity joints of automobiles, characterized in that it contains 0.5 to 10% by weight.