JP2009138055A - Lubricating grease - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricating grease having highly excellent load resistance capable of satisfactorily exhibiting lubricity originating from the grease even under a condition that a component comes in contact with the grease at high surface pressure. <P>SOLUTION: Molybdenum disulfide to be a solid lubricant, graphite and limestone are incorporated into a grease formed by solidifying a base oil using a thickener. Contents of the base oil, the thickener, molybdenum disulfide, the graphite and the limestone are specified to be 70 to 86 wt.%, 6 to 7 wt.%, 1 to 5 wt.%, 1 to 5 wt.% and 1 to 5 wt.%, respectively. The base oil is specified to be a mineral oil and the thickener is specified to be lithium soap. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lubricating grease used for lubricating a sliding part of a component.

  Such lubricating grease is enclosed in the outer ring or the boot attached to the outer ring in a constant velocity universal joint used in, for example, an automobile, and contributes to the smooth operation of the constant velocity universal joint. .

  In recent years, automobiles, agricultural machinery, and various industrial machines have become lighter and more compact, including constant-velocity universal joints, due to space constraints and environmental considerations due to an increase in the number of parts associated with higher performance. Has been made.

  However, when the component is made compact in this way, the contact surface pressure of the component becomes high at the sliding portion of the component, which causes the component to peel off early.

  For example, in a constant velocity universal joint of an automobile, when the constant velocity universal joint is made compact, a ball that is involved in transmission of rotational torque of the constant velocity universal joint and a track groove that is a rolling surface of the ball have a high surface pressure. Therefore, the above-described problem may occur in the ball or the track groove. For this reason, lubrication grease (hereinafter referred to as “grease”) that can withstand high surface pressure is used in a portion where the component contacts and slides at high surface pressure, and this grease is called extreme pressure grease.

  For this extreme pressure grease, a lithium extreme pressure grease in which a base oil is thickened (solidified) with lithium soap and a sulfur-phosphorus extreme pressure additive is contained, or molybdenum disulfide, which is a solid lubricant, is used. A lithium-based extreme pressure grease containing bismuth is known.

In addition, the technique of using a urea-type thing as a thickener is also known for grease (refer patent documents 1 and 2).
JP-A-4-304300 JP-A-4-328198

  As already described, extreme pressure grease that can withstand this high surface pressure contact is used at the part where the component contacts at a high surface pressure. The conventional extreme pressure grease including the one disclosed in No. 2 has a problem that it is difficult to cope with it.

  The present invention has been made in view of the above circumstances, and is a grease for lubrication having an extremely excellent load resistance that can sufficiently exhibit the inherent lubricity of the grease even under conditions in which the components are in contact with each other at a high surface pressure. The purpose is to provide.

  The lubricating grease of the present invention for solving the above-mentioned problems is a lubricating grease having a base oil and a thickener as essential components, and contains molybdenum disulfide and graphite, which are solid lubricants, and limestone. It is characterized by that.

  Since solid lubricants such as molybdenum disulfide and graphite are bonded to the surface of the component, the component can be prevented from being directly contacted and worn even under conditions where the component is contacted at a high surface pressure. For this reason, the load resistance of grease can be improved. This action and effect can be obtained even when the grease film becomes extremely thin.

  Moreover, said effect | action and effect become remarkable by making a base oil contain limestone. Moreover, since limestone has water resistance, the grease can be provided with water resistance.

  The above-described actions and effects of the present invention are as follows. The base oil content is 70 to 86% by weight, the thickener content is 6 to 7% by weight, and the molybdenum disulfide content is 1 to 5% by weight. It can be effectively obtained by setting the content of graphite to 1 to 5% by weight and the content of limestone to 1 to 5% by weight.

  As the thickener, lithium soap or urea-based ones can be used. When lithium thickener is used as the thickener, lithium soap is inexpensive, so the cost when using grease can be reduced. On the other hand, when the thickener is urea-based, the grease can be provided with high load resistance and wear resistance, and the urea-based compound is stable even at high temperatures, thus imparting heat resistance to the grease. can do.

  In the present invention described above, the load resistance of the grease can be further improved by adding a sulfur-based additive to the base oil.

  The base oil may contain at least one of ZnDTP (zinc dithiophosphate), MoDTP (molybdenum dithiophosphate), and MoDTC (molybdenum dithiophosphate). All of ZnDTP, MoDTP, and MoDTC contribute to the improvement of the wear resistance of the grease, and since these additives have oxidation resistance, the grease can be prevented from being oxidized and deteriorated.

  In addition, when at least one of ZnDTP and MoDTP and MoDTC are used in combination, the wear resistance of the grease can be greatly improved. This is because the wear resistance of grease can be remarkably improved by coexistence of a compound having both elements of sulfur and phosphorus and MoDTC. ZnDTP and MoDTP have both elements of sulfur and phosphorus. Because it contains.

  Since the lubricating grease of the present invention contains molybdenum and graphite, which are solid lubricants, and limestone in a base oil thickened with a thickener, the load resistance of the grease can be greatly improved. For this reason, the grease according to the present invention is generated at the time of component contact because the contact surface of the component can be lubricated by fully exerting the inherent lubricity of the grease even under the condition where the component contacts at high surface pressure. It is possible to prevent abnormal noise and wear of contact surfaces of parts.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a fixed type constant velocity universal joint called a ball fixture type (BJ) to which the lubricating grease of the present invention is applied.

  The constant velocity universal joint 1 includes an outer ring 2 having an opening at one end, an inner ring 3, a ball 4, and a cage 5 as main parts, and the inner ring 3, the ball 4, and the cage 5 are disposed inside the outer ring 2. These are housed, and these constitute the internal component 6. A shaft 10 is spline-fitted into the shaft hole 11 of the inner ring 3, and the shaft 10 is formed in a concave groove 12 formed on the outer peripheral surface of the tip portion and a portion facing the concave groove 12 in the shaft hole 11. The circlip 14 interposed between the groove 13 and the concave groove 13 prevents the shaft hole 11 from coming out.

  A plurality of curved track grooves 7 are formed on the spherical inner peripheral surface of the outer ring 2, and a plurality of curved track grooves 8 are formed on the spherical outer peripheral surface of the inner ring 3 so as to face the track grooves 7. Between the outer ring 2 and the inner ring 3, a ball 4 is interposed between the outer ring 2 and the inner ring 3. The ball 4 is held in a pocket 9 of a cage 5 disposed between the outer ring 2 and the inner ring 3.

  The opening of the outer ring 2 is covered with a bellows-shaped resin boot 15. The boot 15 includes a large-diameter end portion 16, a small-diameter end portion 17, and a bellows-shaped intermediate portion 18 that connects the large-diameter end portion 16 and the small-diameter end portion 17. The large-diameter end portion 16 is attached to the outer peripheral surface of the open end portion 21 of the outer ring 2, the small-diameter end portion 17 is attached to the outer peripheral surface of the shaft 10, and each attachment portion is fixed by caulking the boot band (19, 20). Has been.

  As shown by the dotted pattern in FIG. 1, grease 22 is enclosed in the outer ring 2 and the boot 15, and this grease 22 maintains lubrication inside the outer ring 2, 4 and the track groove 7 and between the ball 4 and the track groove 8 are made smooth.

  Here, since the ball 4 and the track grooves (7, 8) are in contact with each other at a high surface pressure, the grease 22 is an extreme pressure grease that can withstand the high surface pressure. In the present embodiment, the grease 22 is a grease obtained by solidifying base oil with a thickener, and molybdenum disulfide, graphite, and limestone are added as additives, and the base oil is mineral oil. Is lithium soap. Molybdenum disulfide and graphite are called solid lubricants.

  In this case, since the load resistance of the grease 22 can be greatly improved, the original lubricity of the grease can be sufficiently exerted even when the components contact at a high surface pressure as in the present embodiment. . As a result, it is possible to prevent abnormal noise caused by direct contact of components and wear due to direct contact of components. This action and effect can be obtained even when the grease film becomes extremely thin.

  This is because molybdenum disulfide and graphite, which are solid lubricants, are bonded to the surface of the component, that is, the balls 4 and the track grooves (7, 8). This is because it is possible to suppress the direct contact of components even when used under surface pressure, and limestone has the same actions and effects.

  In addition, since limestone has lubricity and water resistance, it contributes to the improvement of the lubrication performance of the grease 22, and can impart water resistance to the grease. Further, since limestone is non-toxic and inexpensive, it is preferable to use it in consideration of not adversely affecting the environment, and the cost required for enclosing the grease 22 inside the outer ring 2 and the boot 15 is reduced. be able to.

  The grease 22 has a base oil (mineral oil) content of 70 to 86% by weight, a thickener (lithium soap) content of 6 to 7% by weight, and a molybdenum disulfide content of 1 to 5% by weight. The graphite content is 1 to 5% by weight, and the limestone content is 1 to 5% by weight.

  When the content of the base oil is lower than 70% by weight, sufficient lubricity cannot be imparted to the grease. On the other hand, if the content of the thickener is lower than 6% by weight, the friction coefficient of the grease cannot be sufficiently lowered, and it becomes difficult to obtain the intended effect of the present invention. Furthermore, if the respective contents of molybdenum disulfide and graphite, which are solid lubricants, are lower than 1% by weight, the load resistance of the grease cannot be sufficiently improved, and the intended effect of the present invention is sufficiently obtained. Can't get. This phenomenon is the same even when the content of limestone is lower than 1% by weight.

  When the content of the base oil is higher than 86% by weight, the amount of the additive that can be added decreases, and it becomes difficult to provide the base oil with performances other than lubricity. On the other hand, if the content of the thickener is higher than 7% by weight, the grease becomes too hard, making it difficult to use as a grease. This is the same when the content of each of the solid lubricants molybdenum disulfide and graphite is higher than 5% by weight and when the content of limestone is higher than 5% by weight.

  In addition to mineral oil, it is possible to use a base oil obtained by mixing a mineral oil with a synthetic oil, and the thickener can be a urea-based one other than lithium soap.

  As the urea system, a diurea system, a tetraurea system, and the like are known. The urea system has excellent friction resistance and heat resistance. Therefore, when the thickener is a urea system, the grease 22 can be provided with friction resistance, and the grease 22 can be used at a high temperature.

  When the grease 22 contains a sulfur-based additive containing elemental sulfur (S), the load resistance of the grease 22 can be further improved. As the sulfur-based additive, ZnDTP (zinc dithiophosphate), MoDTP (molybdenum dithiophosphate), MoDTC (molybdenum dithiophosphate) and the like are preferable.

  In addition, ZnDTP (zinc dithiophosphate), MoDTP (molybdenum dithiophosphate), and MoDTC (molybdenum dithiophosphate) have wear resistance and oxidation resistance, and at least one of these is used as a base oil. When contained, the wear resistance of the grease 22 can be improved. Moreover, since the grease 22 can be provided with oxidation resistance by the above-described additive, deterioration of the grease 22 due to oxidation can be prevented.

  If at least one of ZnDTP and MoDTP and MoDTC are used in combination, the wear resistance of the grease 22 can be greatly improved. This is because the wear resistance of the grease 22 can be remarkably improved by coexisting a compound having both elements of sulfur element (S) and phosphorus element (P) and MoDTC. ZnDTP and MoDTP This is because it contains both elements of sulfur and phosphorus.

  As mentioned above, although embodiment of this invention was described, embodiment mentioned here is an illustration to the last, and can change arbitrarily within the meaning and content range as described in a claim.

  For example, the additive to be added to the grease can be added within a range where the function and effect of the present invention can be obtained according to the use environment. At this time, it is desirable to refrain from using a compound containing lead element (Pb) in consideration of environmental aspects.

  Examples of the grease according to the present invention will be described below in comparison with conventional greases.

  First, the grease of the present invention described in the embodiment (hereinafter referred to as a new grease) and a conventional grease are prepared as a comparative example. For the conventional grease as a comparative example, a lithium-based thickener and a diurea thickener are prepared. Consistency test, drop point test, load resistance test with Timken tester, load test with shell four-ball tester, wear test with high-speed four-ball tester Are shown in FIGS. 2 (A) to (C). 2A is performed based on the test method standard of JIS number K 2220, and the test of FIG. 2B is performed based on the test method standard of ASTM (American Society for Testing and Materials) number D 2596. FIG. The test of (C) was performed based on the test method standard of ASTM number D2266. The numbers of the test method standards and the test conditions based on these numbers are shown in the margins of FIGS. 2 (A) to (C). The measurement results shown in FIG. 2 are the conditions for each grease.

  Here, each of the above tests will be described. The consistency test is a test for measuring the hardness (consistency) of grease, and the dropping point test is a test for measuring the dropping point of grease (the temperature at which it becomes liquid when heated). The load resistance test by the Timken tester is a test for measuring the maximum load (OK load) at which no scoring (burn-in) occurs on the friction surface of the part. The shell four-ball load-bearing test is a test for measuring the load (maximum load) at which one of the four balls is a test ball to be fused. In this test, one sample (grease) is subjected to LNSL (test The load at the start), WP (the load at which the test ball is fused), and LWI (the value obtained by dividing LNSL by the size of the wear mark on the test ball) are measured. The high-speed four-ball wear resistance test is a test in which one rotating sphere is pressed against the center of three fixed spheres and brought into contact at three points, and the wear scar generated at the contact point is measured.

  Next, the conventional grease or new grease is sealed inside the outer ring of the constant velocity universal joint (BJ125) as shown in FIG. 1, and the swing durability test is performed under the condition that the member contacts at high surface pressure. FIG. 3 shows the test conditions, and FIG. 4 and FIG. 5 show the test results (damage of the outer ring, inner ring, cage, and ball). In this rocking durability test, the conventional grease was tested only for grease containing a diurea thickener. This is because, in the test of FIG. 2, the diurea grease was superior in load resistance and wear resistance than the lithium grease.

  In the rocking endurance test shown in FIG. 3, four samples each having a conventional grease (BJ125) and a new grease (BJ125) were prepared, and No.1 to No.4 and No.5 to No.5 were prepared. It was set as No.8. In this oscillation endurance test, FIG. 4 shows the test result of the conventional grease (diurea type), and FIG. 5 shows the test result of the new grease.

In the test conditions of this test, when the total number of rotations is about 8.500 × 10 ⁶ rotations and the rotation time is about 200 hours, the sample in which the conventional grease is encapsulated has four samples as shown in FIG. Three of them (No.1, No.2, No.4) have problems, and in these cases, the outer ring, ball, and cage are flaking (the surface of the part is peeled off in a scale shape) and peeling (the surface of the part is Peeling off or peeling off), and the cage was also chipped. However, in the sample in which the new grease is filled, as shown in FIG. 5, there is no problem in the three samples (No. 5 to No. 7), and the problem is also in the remaining sample (No. 8). Was minor.

Furthermore, in the sample in which the new grease is enclosed, as shown in FIG. 5, even if the total number of revolutions is increased to about 4.3 × 10 ⁷ rotations and the rotation time is increased to about 1000 hours, there are few samples in which trouble occurs, It can be seen that the number of parts in which defects occur and the number of defects occurring in those parts are also small.

  According to the present example, it was found that the new grease has a significantly superior load resistance compared to the conventional grease, and thus the original lubricity of the grease can be sufficiently exerted.

It is sectional drawing which shows embodiment of this invention. In the Example of this invention, it shows the conditions of a conventional grease and a new grease, (A) is a table | surface which shows the measurement result of a consistency test, a drip point test, and the test by a Timken tester. (B) is a table | surface which shows the measurement result by a shell four-ball load tester. (C) is a table | surface which shows the measurement result by a high-speed four-ball abrasion resistance tester. It is a table | surface which shows the test conditions of the rocking | swiveling durability test of a constant velocity universal joint (BJ125). 4 is a table showing test results of conventional grease (diurea type) in the test shown in FIG. 3. 4 is a table showing test results of new grease in the test shown in FIG. 3.

Explanation of symbols

1 Constant velocity universal joint (BJ)
2 Outer ring 3 Inner ring 4 Ball 5 Cage

Claims (6)

Lubricating grease containing base oil and thickener as essential components,
A lubricating grease characterized by containing molybdenum disulfide and graphite, which are solid lubricants, and limestone.   The base oil content is 70 to 86% by weight, the thickener content is 6 to 7% by weight, the molybdenum disulfide content is 1 to 5% by weight, and the graphite content is The lubricating grease according to claim 1, wherein the content is 1 to 5% by weight, and the content of the limestone is 1 to 5% by weight.   The lubricating grease according to claim 1 or 2, wherein the thickener is lithium soap.   The lubricating grease according to claim 1 or 2, wherein the thickener is a urea type.   The lubricating grease according to any one of claims 1 to 4, wherein the base oil contains a sulfur-based additive.   The lubricating grease according to any one of claims 1 to 5, wherein the base oil contains at least one of ZnDTP, MoDTP, and MoDTC.

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