JP6902233B2 - Grease composition and movable fitting - Google Patents

Description

The present invention relates to, for example, a grease composition for movable joints.

Conventionally, for example, grease using mineral oil or synthetic hydrocarbon oil has been used for movable joints such as suspensions and lower arms of automobiles (see Patent Document 1).

In order to maintain the lubricity of the movable joint, these greases use a base oil with a relatively high viscosity or improve the thickener to increase the viscosity of the base oil and improve the adhesiveness of the grease. ing.

Japanese Unexamined Patent Publication No. 2000-23188

However, the conventional grease has a high viscosity in order to maintain the lubricity, and there is a problem that the operating torque of the movable joint becomes high due to this influence. Further, at a low temperature, the viscosity of the grease becomes very high, and there is a concern that malfunction may occur.

Therefore, the present invention has been made in view of such a problem, and a grease composition capable of reducing the operating torque and improving the low temperature property as compared with the conventional one, and a movable joint using the same. The purpose is to provide.

The grease composition of the present invention is a grease composition used for lubricating the inside of a movable joint having a spherical portion and a receiving member that receives the spherical portion, and is a dimethyl silicone oil as a base oil. , The additive is characterized by containing at least one of a carboxylic acid-modified silicone and an amino-modified silicone.

Further, in the grease composition of the present invention, the content of the additive is preferably 15 parts by mass or less.

Further, in the grease composition of the present invention, the content of the additive is preferably 0.01 part by mass or more.

Further, in the grease composition of the present invention, the additive is preferably a modified silicone represented by the following general formulas (1), (2) or (3).

Further, in the grease composition of the present invention, the kinematic viscosity of the additive ^{is preferably 15000 mm 2} / s or less at 25 ° C.

Further, in the grease composition of the present invention, the viscosity of the grease composition is preferably −40 ° C., a shear rate of 1.0 S- ¹ , and 5500 Pa · s or less.

Further, in the grease composition of the present invention, the kinematic viscosity of the base oil ^{is preferably 100,000 mm 2} / s or less at 25 ° C.

Further, the present invention is a movable joint having a spherical portion, a receiving member that receives the spherical portion, and a surface layer that covers the surface of the spherical portion, and at least one of the spherical portion and the surface layer is made of resin. It is formed and is characterized in that the grease composition described above is filled between the spherical portion and the surface layer.

According to the grease composition of the present invention, the operating torque can be reduced and the low temperature property can be improved as compared with the conventional one.

Therefore, the grease composition of the present invention can be suitably used as a lubricant for movable joints.

It is a graph which measured the relationship between the temperature and the operating torque by using a plurality of grease compositions having different compositions for a movable joint.

Hereinafter, one embodiment of the present invention (hereinafter, abbreviated as “embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof.

The present inventor has conducted sincere research on a grease composition used for lubricating the inside of a movable joint having a spherical portion and a receiving member that receives the spherical portion, and as a result, dimethyl silicone oil is used as a base oil. By using the above, the operability at low temperature has been improved.

(Grease composition)
The grease composition in the present embodiment contains dimethyl silicone oil as a base oil, and preferably contains the additives described below.

In addition, those conventionally contained as a grease composition such as a thickener are appropriately added.

In the present embodiment, the kinematic viscosity of the base oil ^{is preferably 100,000 mm 2} / s or less at 25 ° C. As shown in the experiment described later, in the present embodiment, the kinematic viscosity of the base oil can be defined within the above range. The kinematic viscosity of the base oil ^{is more preferably 10000 mm 2} / s or less, ^{further preferably 5000 mm 2} / s or less, and even ^{more preferably 2000 mm 2} / s or less at 25 ° C. Further, although the lower limit value is not particularly limited, for example, the kinematic viscosity of the base oil can be lowered to about ^{5 mm 2 / s at 25 ° C.}

In the present embodiment, two or more kinds of different types of base oils may be mixed and used, and dimethyl silicone oil may be used as one of the base oils. However, when two or more types of base oils are combined, it is preferable that more than half (50 parts by mass or more) of the base oils in the grease composition is composed of dimethyl silicone oil.

The additive contained in the grease composition preferably contains at least one of a carboxylic acid-modified silicone and an amino-modified silicone.

ここで、数値を限定するものではないが、ｍは、数十以上であり、具体的には５０以上であり、後述する実施例では、８０〜７５０程度である。また、ｎは、１００程度以下であり、具体的には２０以下であり、後述する実施例では、１〜１０程度である。

Specifically, the additive is preferably a modified silicone represented by the following general formulas (1), (2) or (3).

Here, although the numerical value is not limited, m is several tens or more, specifically 50 or more, and in the examples described later, it is about 80 to 750. Further, n is about 100 or less, specifically 20 or less, and in the examples described later, it is about 1 to 10.

As described above, in the present embodiment, it is preferable to contain the carboxylic acid-modified silicone and / or the amino-modified silicone as the additive, but from the viewpoint of stability over time, the carboxylic acid-modified silicone is more than the amino-modified silicone. Is preferably included.

In the present embodiment, it is preferable to adjust the content of the additive within a predetermined range. If the content of the additive is too large, oil separation is likely to occur. Therefore, specifically, the content of the additive is preferably 15 parts by mass or less. Here, 100 parts by mass is the total amount of the grease composition, and therefore, "parts by mass" means a ratio to the total amount of the grease composition. The same applies hereinafter.

Further, in the present embodiment, the amount of the additive added is preferably 0.01 part by mass or more. If an additive of this amount is contained, the operating torque can be reduced as compared with the conventional case.

In the present embodiment, the amount of the additive added is more preferably 10 parts by mass or less, further preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less. Further, the amount of the additive added is more preferably 0.2 parts by mass or more. The amount of the additive added is most preferably about 0.02 parts by mass to 1 part by mass.

Further, in the present embodiment, the kinematic viscosity of the additive ^{is preferably 15000 mm 2} / s or less at 25 ° C. This kinematic viscosity can be adjusted by the number of repetitions of the chemical formula described in the above general formula.

The thickener contained in the grease composition of the present embodiment is not particularly limited, but for example, lithium soap, calcium soap, sodium soap, aluminum soap, lithium composite soap, calcium composite soap, aluminum composite soap. , Urea compound, organic bentonite, polytetrafluoroethylene, silica gel, and sodium terephthalamate can be selected from at least one. Lithium soap is a saponification reaction product of fatty acid or its derivative and lithium hydroxide. The fatty acid used is at least one selected from the group consisting of saturated or unsaturated fatty acids having 2 to 22 carbon atoms and derivatives thereof. In addition, "soap" obtained by reacting the above fatty acid or its derivative with lithium hydroxide is commercially available, and this can also be used.

Further, if necessary, an antioxidant, a rust preventive, a metal corrosion inhibitor, an oil-based agent, an abrasion resistant agent, an extreme pressure agent, a solid lubricant and the like can be added. The content of these additives is within the range of about 0.01 parts by weight to 20 parts by weight. The antioxidant can be selected from hindered phenol, alkylated diphenylamine, phenyl-α-naphthylamine and the like. The rust preventive can be selected from carboxylic acids such as stearic acid, dicarboxylic acids, metal soaps, carboxylic acid amine salts, metal salts of heavy sulfonic acids, and carboxylic acid partial esters of polyhydric alcohols. The metal corrosion inhibitor can be selected from benzotriazole, benzimidazole and the like. The oily agent can be selected from amines such as laurylamine, higher alcohols such as myristyl alcohol, higher fatty acids such as palmitic acid, fatty acid esters such as methyl stearate, and amides such as oleylamide. it can. The wear resistant agent can be selected from zinc-based, sulfur-based, phosphorus-based, amine-based, ester-based, and the like. The extreme pressure agent should be selected from zinc dialkyldithiophosphate, molybdenum dialkyldithiophosphate, olefin sulfide, fat and oil sulfide, methyltrichlorostearate, chlorinated naphthalene, benzyl iodide, fluoroalkylpolysiloxane, lead naphthenate and the like. Can be done. The solid lubricant can be selected from graphite, fluorographite, polytetrafluoroethylene, melamine cyanurate, molybdenum disulfide, antimony sulfide and the like.

The viscosity of the grease composition in the present embodiment is preferably −40 ° C., a shear modulus of 1.0 S- ¹ , and 5500 Pa · s or less. Since the viscosity of the grease composition changes depending on the shear rate, the shear rate is specified. Further, in the present embodiment, the difference in viscosity between normal temperature (25 ° C.) and −40 ° C. can be about 4000 Pa · s or less at a ^{shear rate of 1.0 S-1.}

The consistency of the grease composition can be about 200 to 500. The method for measuring the consistency will be described in the column of Examples described later.

(Movable fitting)
The movable joint using the grease composition of the present embodiment can be used, for example, for a movable part such as an automobile suspension, a lower arm, and a tie rod end.

The movable joint is configured to include a spherical portion, a receiving member that receives the spherical portion, and a surface layer that covers the surface of the spherical portion. The surface layer is held by the receiving member.

Then, the grease composition of the present embodiment is filled between the spherical portion and the surface layer. By the way, the spherical portion is formed of, for example, metal, and the receiving member and the surface layer are formed of, for example, resin. Although the material is not limited, examples of the resin include polyacetal resin and polyester resin.

As described above, in the present embodiment, a grease composition containing a dimethyl silicone oil having a high viscosity index as a base oil is filled between the metal and the resin. That is, for example, the grease composition containing dimethyl silicone oil as the base oil can effectively exhibit the desired lubrication performance between the metal and the resin, as compared with the case where both are metals. In particular, with the miniaturization of movable joints, in the conventionally used mineral oils and synthetic hydrocarbon oils, the change in grease viscosity at a low temperature becomes a non-negligible level, whereas in the present embodiment, this is achieved. It can overcome the problem, suppress the increase in viscosity of the grease composition at a low temperature, and maintain the fluidity of the grease composition appropriately.

In addition, in the carboxylic acid-modified silicone used as an additive, the carboxylic acid portion is easily adsorbed on the metal material, thereby improving the lubricity of the movable joint, reducing the operating torque, and suppressing stick slip. Will be possible. Therefore, by using the movable joint of the present embodiment, the steerability of the automobile can be improved, and in particular, the malfunction at low temperature can be suppressed.

Further, the movable joint of the present embodiment has a spherical portion, a receiving member that receives the spherical portion, and a surface layer that covers the surface of the spherical portion, and at least one of the spherical portion and the surface layer is formed of resin. A grease composition having a viscosity of 5500 Pa · s or less at −40 ° C. and a shear rate of 1.0 S ^{-1 can be filled between the spherical portion and the surface layer.}

In the above embodiment, a movable joint for an automobile is mentioned as an example of the movable joint, but it can be applied to transportation equipment and industrial equipment other than the automobile as long as it has a high load load and a movable part.

Hereinafter, the present invention will be described in detail with reference to examples carried out to clarify the effects of the present invention. The present invention is not limited to the following examples.

In the experiment, the viscosity, consistency, and grease viscosity of the base oil of the grease compositions shown in Tables 1 and 2 were measured, and each grease composition was further filled between the spherical portion and the surface layer of the movable joint. The operating torque at room temperature (25 ° C.), the operating torque at −40 ° C., and the presence or absence of stick slip were measured.

In addition, "carboxylation -1", "carboxylation-2", "carboxylation -3", "amino modification -1", "amino modification-2", "amino modification-3" shown in Tables 1 and 2 Is shown in Table 3 below.

The viscosities of the base oils shown in Tables 1 and 2 are measured values at 25 ° C. In the grease composition having a viscosity of the base oil shown in Tables 1 and 2 of 1800 cSt (= mm ² / s), a 100 cSt product and a 10000 cSt product were mixed to adjust the viscosity. On the other hand, as the grease composition having a base oil viscosity of 5 cSt and the grease composition having a base oil viscosity of 100,000 cSt, commercially available dimethyl silicone oil was used as it was.

Consistency was measured by the consistency test method specified in JIS K2220.

The operating torque at room temperature was measured with a grease composition applied at 0.5 g, a commercially available tie rod end, a rotation speed of 0.2 rpm, and a rotation angle of 45 degrees (reciprocating operation). .. The operating torque at −40 ° C. was measured in the same manner as the operating torque at room temperature by allowing the movable joint coated with the grease composition to stand still in a constant temperature bath at −40 ° C. for 4 hours.

The viscosity of the grease composition at −40 ° C. was measured with a rheometer owned by Nippeco Co., Ltd. In the measurement, the viscosity at a shear rate of 1s ^{-1 was measured.}

Based on the examples shown in Tables 1 and 2, the content of the additive composed of carboxylic acid-modified silicone or amino-modified silicone is set to 15 parts by mass or less, preferably 10 parts by mass or less, more preferably 10 parts by mass or less. It was set to 5 parts by mass or less, more preferably 3 parts by mass or less.

If the content of the additive is too large, the thickener structure constituting the grease composition is easily deformed or broken, and softening leakage and oil separation of the grease composition are likely to occur. The amount is preferably small.

On the other hand, although it is the lower limit of the content of the additive, it was found that the operating torque can be reduced as compared with the conventional case even if 0.01% by mass of Example-2 shown in Table 1 is added. Therefore, the lower limit of the content of the additive was set to 0.01 parts by mass. However, if the content of the additive is increased a little more, for example, as can be seen in Example 3, the operating torque can be further reduced, and in particular, not only at room temperature but also at -40 ° C. It was found that the operating torque can be stably maintained at a low value.

Further, according to Example-10 shown in Table 1, the kinematic viscosity of the base oil ^{was set to 100,000 mm 2} / s or less at 25 ° C. If the kinematic viscosity of the base oil becomes higher than this, there is a concern that workability may deteriorate in actual use.

Further, according to Example-9 shown in Table 1, the kinematic viscosity of the base oil ^{was set to 5 mm 2} / s or more at 25 ° C. If the kinematic viscosity of the base oil is made lower than this, it is considered that the lubrication ability is lowered and the base oil is likely to dry.

The hardness (consistency) of the grease composition is preferably about 225 (consistency: No. 3) from Examples -11. If it is harder than this, there is a concern that workability will deteriorate in actual use.

Further, the softness (consistency) of the grease composition is preferably about 465 (consistency: No. 000) from Implementation-12. If it is softer than this, there is a concern that the lubricity may deteriorate and the grease composition may leak.

From the above experimental results, it was set that the consistency of the grease composition is preferably about 200 to 500.

Further, in this embodiment, the viscosity of the grease composition at −40 ° C. can be set to 5500 Pa · s or less ^{at a shear coefficient of 1.0 S-1.} On the other hand, in the comparative example, the viscosity of the grease composition was about 40,000 Pa · s or more at ^{a shear rate of 1.0 S-1, or could not be measured.}

Using Example 3 shown in Table 1 and Comparative Example 3 and Comparative Example 4 shown in Table 2, the operating torque of the movable joint at each temperature was measured. The measurement conditions are as listed above.

The experimental conclusions are shown in Table 4 and FIG. 1 below.

As shown in Table 4 and FIG. 1, in Comparative Example 3 and Comparative Example 4, it was found that the operating torque rapidly increased when the temperature was lower than 0 ° C. On the other hand, in Example 3, it was found that the operating torque can be suppressed to about 2000 mN · m or less in the temperature range of about −40 ° C. to 100 ° C. Further, in Comparative Example 3 and Comparative Example 4, the operating torque at −40 ° C. increases by about 5000 mN · m as compared with the operating torque at 25 ° C., whereas in Example 3, It was found that the operating torque at -40 ° C and the operating torque at 25 ° C hardly changed (about 300 nNm or less).

In the present invention, the grease composition using dimethyl silicone oil having a high viscosity index as the base oil can suppress an increase in viscosity at a low temperature and can maintain good fluidity. By using the grease composition of the present invention as a lubricant for a movable joint in which at least one of the spherical portion and the surface layer covering the spherical portion is formed of resin, the operating torque is reduced (particularly, the operating torque at low temperature). Reduction) and suppression of stick strips can be achieved. The movable joint to which the grease composition of the present invention is applied can be suitably used for a movable joint of an automobile, but can also be effectively used for transportation equipment and industrial equipment other than automobiles.

Claims (8)

A grease composition used for lubricating the inside of a movable joint having a spherical portion and a receiving member for receiving the spherical portion.
Contains dimethyl silicone oil as a base oil and additives,
The grease composition is characterized by containing at least one of a carboxylic acid-modified silicone and an amino-modified silicone. The grease composition according to claim 1 , wherein the content of the additive is 15 parts by mass or less. The grease composition according to claim 1 or 2 , wherein the content of the additive is 0.01 parts by mass or more. The additive is represented by the following general formula (1), (2) or grease composition according to any one of claims 1 to 3, characterized in that the modified silicone represented by (3).

Kinematic viscosity of the additive at 25 ° C., the grease composition according to any one of claims 1 to 4, characterized in that at most 15000mm ² / s. The grease composition according to any one of claims 1 to 5 , wherein the grease composition has a viscosity of −40 ° C. and a shear modulus of 1.0 S- ^{1 and is 5500 Pa · s or less.} .. The grease composition according to any one of claims 1 to 6 , wherein the kinematic viscosity of the base oil is 100,000 mm ² / s or less at 25 ° C. A movable joint having a spherical portion, a receiving member that receives the spherical portion, and a surface layer that covers the surface of the spherical portion.
At least one of the spherical portion and the surface layer is made of resin.
A movable joint characterized in that the grease composition according to any one of claims 1 to 7 is filled between the spherical portion and the surface layer.

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