A kind of automobile EPS steering gear worm gear grease composition and its application

Abstract

The present invention relates to the field of grease technology, and in particular to a grease composition for worm gear of an automobile EPS steering gear and its application. The grease composition provided by the present invention comprises the following components by weight: 77 to 85 parts of base oil, 6 to 9 parts of thickener, 8 to 12 parts of solid lubricant, and 0.5 to 2.0 parts of oxidized polyethylene wax; wherein the thickener is a mixture of 12-hydroxy stearic acid lithium soap and isostearic acid lithium soap. The grease composition provided by the present invention has excellent anti-wear and friction reduction performance, a low friction coefficient, can effectively prevent abnormal noise and stick-slip phenomenon, has good low-temperature starting performance, mechanical stability and water resistance and rust prevention, and fully meets the lubrication performance requirements of various aspects of the worm gear of the automobile EPS steering gear.

Description

Technical Field

[0001] The invention relates to the technical field of lubricating grease, and in particular to a lubricating grease composition for a worm gear of an automobile EPS steering gear and application thereof. Background Art

[0002] With the development of electrification and intelligence of automobiles, electric power steering almost occupies the entire market share of steering gears. Worm gears are commonly used reduction mechanisms for electric power steering, which play the role of reducing speed and increasing torque. Passengers have higher and higher requirements for automobile comfort. Abnormal steering noise is most easily perceived by customers. In recent years, there have been more and more complaints from customers. Major OEMs have taken various measures to optimize the design from aspects such as the size and surface structure of worm gears, and to improve lubrication and other aspects to reduce abnormal steering noise and improve customer satisfaction. As a safety part of automobiles, the steering system requires grease to have the reliability and lifelong lubrication characteristics required by the safety system. At present, grease is mainly supplied by foreign suppliers, and the market share of domestic suppliers is extremely low and there is still room for further improvement in performance.

[0003] CN110408463A discloses a worm gear grease and its preparation method. The grease is composed of base oil, thickener, solid hydrocarbon compound, high temperature improver, anti-wear extreme pressure agent, antioxidant and solid filler. The base oil is 50-100 mm thick at 40°C. 2 / s polyalphaolefin, alkyl naphthalene, ester oil of two or more kinds of blending oil; but the composition of the grease is complex, and attempts to achieve extreme pressure and anti-wear effects through active additives containing phosphorus, chlorine, and sulfur. Such additives cannot form a chemical adsorption film on the surface of nylon material. At the same time, the introduction of a large number of active additives will affect the long life and colloid stability of the grease. There is oil separation during use, which shortens the service life of the equipment and causes customer complaints. CN103242942A discloses a low-temperature worm gear grease and a preparation method thereof. The grease composition contains a synthetic base oil, a thickener, a solid lubricant, a friction modifier, a rust inhibitor, a metal deactivator, and an antioxidant. It mainly uses 20% of organic esters with better oiliness to blend with other base oils to improve the anti-oxidation property of the oil, the solubility of additives and thickeners, and the compatibility of materials, but the grease still has room for further improvement in terms of the difference in dynamic and static friction coefficients. CN105647628A discloses a special lubricating grease for worm gear and a preparation method thereof. The grease has a temperature of 380 to 400 mm at 40°C. 2 / s high viscosity refined mineral oil as base oil, organic and inorganic mixture as thickener, extreme pressure anti-wear agent, antioxidant, and special synthetic materials are added; but the low temperature performance of the product is poor and does not meet the applicable requirements of -40℃. CN113563944A discloses a special grease for worm gear and its preparation method. The grease is 280~300mm at 40℃.2 / s high viscosity refined mineral oil is used as base oil, with organic and inorganic mixed soap as thickener, and extreme pressure anti-wear agent, antioxidant and tackifier are added; but the low temperature performance of the product is poor and does not meet the use requirement of -40℃.

[0004] At present, the main reasons for steering noise caused by lubrication include the following aspects: 1. The poor wear resistance of grease leads to serious wear of the worm gear; 2. The insufficient bearing capacity of grease leads to the formation of abrasive particles on the friction interface under impact load, resulting in wear; 3. The large difference between the dynamic and static friction coefficients of grease leads to sticky noise when the static and dynamic friction is converted. Therefore, it is urgent to find a high-performance grease to effectively solve the problems of steering noise caused by poor lubrication. Summary of the invention

[0005] The invention provides an automobile EPS steering gear worm gear grease composition and application thereof, which are used to solve the defects of the prior art such as abnormal steering noise caused by poor lubrication, and realize a high-performance grease that can be applied to automobile EPS steering gear worm gear.

[0006] The present invention provides a grease composition, which comprises the following components in parts by weight:

[0007]

[0008] Wherein, the thickener is a mixture of 12-hydroxystearate lithium soap and isostearate lithium soap.

[0009] In the prior art, the average friction coefficient of the grease composition is often the focus of attention and optimization in this field, while the dynamic and static friction coefficients of the grease vary greatly, which leads to sticky and slippery noises when the dynamic and static frictions are converted. However, after extensive research, the present invention has found that when 12-hydroxystearate lithium soap and isostearate lithium soap are used as thickeners according to the above scheme, and compounded with base oil, oxidized polyethylene wax and solid lubricant in the above dosage relationship, the anti-wear performance of the prepared grease composition is greatly improved, which can not only significantly reduce the average friction coefficient, but most importantly, the difference in dynamic and static friction coefficients of the grease composition is significantly reduced, which can effectively solve the abnormal noise problem of the worm gear of the automotive EPS steering gear, reduce wear, and have an operating temperature range of -50 to 130°C, meeting the reliability and lifelong lubrication characteristics required for automotive safety parts, and providing good lubrication and protection for the use parts.

[0010] In the lubricant composition of the present invention, the mixture of thickener 12-hydroxystearate lithium soap and isostearate lithium soap has more excellent lubricity and better adsorption and release capabilities for base oil; at the same time, the oxidized polyethylene wax has good internal lubrication, and the solid lubricant has chemical inertness and self-lubricating ability. The two can play a synergistic role after cooperating with the base oil and the thickener, and can effectively reduce the difference in dynamic and static friction coefficients, greatly improve the wear reduction and anti-wear capabilities, and at the same time ensure the low-temperature performance of the grease.

[0011] In the present invention, 12-hydroxystearic acid lithium soap and isostearic acid lithium soap are prepared by reacting 12-hydroxystearic acid and isostearic acid lithium soap with lithium hydroxide respectively.

[0012] Aiming at the specific performance required by the worm gear of the automotive EPS steering gear, the present invention further optimizes the selection and dosage of each component and obtains the following preferred solution.

[0013] Preferably, when the amount of the oxidized polyethylene wax is 0.5-2.0 wt % based on the total amount of the grease composition, the difference between the dynamic and static friction coefficients can be reduced and the stick-slip phenomenon can be avoided.

[0014] Preferably, the average molecular weight of the oxidized polyethylene wax is 2000-10000; more preferably, when the average molecular weight is 5000-10000, the anti-stick-slip effect is better.

[0015] Preferably, the base oil is a poly-alpha olefin synthetic oil, and the kinematic viscosity of the base oil at 40°C is 16 to 48 mm 2 / s, the solidification point is not higher than -55℃, and the viscosity index is not less than 120.

[0016] The present invention finds that PAO synthetic oil with kinematic viscosity, pour point and viscosity index within the above ranges has more excellent high and low temperature performance and reliable long life performance, while the compatibility with the rubber and plastic material of the EPS steering gear is greatly improved.

[0017] Preferably, the mass ratio of the 12-hydroxystearate lithium soap to the isostearate lithium soap is 3:1 to 1:3; more preferably, the mass ratio of the 12-hydroxystearate lithium soap to the isostearate lithium soap is 3:1.

[0018] Preferably, the solid lubricant is one of PTFE and MCA or a mixture of the two.

[0019] When the solid lubricant is a mixture of PTFE and MCA, the mass ratio of PTFE to MCA is 4:1 to 1:1.

[0020] Preferably, the grease composition further comprises a detergent dispersant, which is a high base synthetic calcium sulfonate having a total base number greater than 300 mgKOH / g.

[0021] The present invention finds that the above-mentioned detergent dispersant with a high alkalinity value can improve the chemical stability and colloidal stability of grease, reduce or avoid agglomeration of solid lubricants, and thus help improve the lubrication effect.

[0022] More preferably, when the amount of the detergent dispersant is 1.0 to 3.0 wt % based on the total amount of the grease composition, agglomeration of the solid lubricant can be effectively avoided, and the colloidal stability and storage stability of the grease can be improved.

[0023] Preferably, the grease composition also includes an antioxidant, which is an amine antioxidant and / or a phenolic antioxidant; the amine antioxidant is selected from one or two of alkylated diphenylamine, naphthylamine and p-phenylenediamine; the phenolic antioxidant is one or two of 2,6-di-tert-butyl-p-cresol or α-naphthol.

[0024] More preferably, the antioxidant is a mixture of 2,6-di-tert-butyl-p-cresol and alkylated diphenylamine in a mass ratio of 1:0.8-1.2.

[0025] Those skilled in the art can combine the above-mentioned preferred embodiments according to common understanding to obtain preferred embodiments of the lubricant composition of the present invention.

[0026] As a preferred embodiment of the present invention, the grease composition comprises the following components in parts by weight:

[0027]

[0028] During the specific implementation process, those skilled in the art can prepare the grease composition using conventional methods in the art according to actual conditions.

[0029] As a preferred embodiment of the present invention, the method for preparing the grease composition comprises the following steps:

[0030] Add 1 / 3 to 1 / 2 of the base oil and all the 12-hydroxystearic acid and isostearic acid into the reactor and heat it to 90-95°C. Add all the lithium hydroxide solution (105-110) and react for 45-60 minutes. After the reaction is completed, heat it to 200-205°C, add 1 / 3 of the base oil and cool it down. When the temperature drops below 140°C, add all the antioxidants. When the temperature drops below 80°C, add the remaining base oil, solid lubricant and detergent dispersant. After dispersion and grinding by post-processing equipment, the finished product is canned.

[0031] The present invention further provides application of the lubricant composition in a worm gear of an automobile EPS steering gear.

[0032] Based on the above scheme, the beneficial effects of the present invention are as follows:

[0033] The present invention, through the compatibility test of the selection of raw material types and the addition amount in the product formula, finally provides a grease composition with excellent anti-wear and friction reduction performance, a low friction coefficient and a low difference between dynamic and static friction coefficients, which can effectively prevent abnormal noise and sick-slip (stick-slip) phenomenon, and has good low-temperature starting performance, mechanical stability and water resistance and rust prevention. At the same time, the use temperature range of the grease composition is -40 to 130°C, which can provide good lubrication and protection for the worm gear of the EPS steering gear. The EPS steering gear worm gear grease of the present invention has passed the stick-slip and durability bench test of the host manufacturer. From the test results, it fully meets the lubrication performance requirements of the worm gear of the automobile EPS steering gear in all aspects. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The PAO synthetic oil used in the following examples has a freezing point of no higher than -55°C and a viscosity index of no less than 120. The "%" mentioned in the base oil refers to "mass percentage content".

[0036] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0037] Example 1

[0038] This embodiment provides an automotive EPS steering gear worm gear grease composition, comprising:

[0039] Thickener: 70 g, of which the mass ratio of 12-hydroxystearic acid to isostearic acid is 3:1, lithium hydroxide 9.72 g, water 48.6 g;

[0040] Base oil: 750g (PAO synthetic oil: 100%, base oil 40℃ kinematic viscosity: 16mm 2 / s, viscosity index is 132);

[0041] Solid lubricant: PTFE: 60g; MCA: 60g;

[0042] Oxidized polyethylene wax: 20g;

[0043] Antioxidant: diphenylamine 20g;

[0044] Detergent dispersant: 20g of high base synthetic calcium sulfonate;

[0045] This embodiment further provides a method for preparing the above-mentioned automotive EPS steering gear worm gear grease composition, specifically:

[0046] Add 375g of base oil and all the 12-hydroxystearic acid and isostearic acid into a reactor and heat it to 90-95°C, add all the lithium hydroxide solution at 105-110°C and react for 45-60min; after the reaction is completed, heat it to 200-205°C, add 250g of base oil and cool it down, add all the antioxidants when the temperature drops below 140°C, cool it down to below 80°C, add 125g of base oil, solid lubricant and detergent dispersant, and disperse and grind it through post-processing equipment before canning the finished product.

[0047] Example 2

[0048] This embodiment provides an automotive EPS steering gear worm gear grease composition, comprising:

[0049] Thickener: 50 g, of which the mass ratio of 12-hydroxystearic acid to isostearic acid is 1:1, lithium hydroxide 7.04 g, water 35.2 g;

[0050] Base oil: 850g (PAO synthetic oil: 100%, base oil 40℃ kinematic viscosity: 32mm 2 / s, viscosity index is 129);

[0051] Solid lubricant: PTFE: 40g; MCA: 40g;

[0052] Oxidized polyethylene wax: 5g;

[0053] Antioxidant: 2,6-di-tert-butyl-p-cresol 5g;

[0054] Detergent dispersant: high base synthetic calcium sulfonate 10g;

[0055] This embodiment further provides a method for preparing the above-mentioned automotive EPS steering gear worm gear grease composition, specifically:

[0056] Add 425g of base oil and all the 12-hydroxystearic acid and isostearic acid into a reactor and heat to 90-95°C, add all the lithium hydroxide solution at 105-110°C and react for 45-60min; after the reaction is completed, heat to 200-205°C, add 283g of base oil and cool down, add all the antioxidants when the temperature drops below 140°C, cool to below 80°C, add 142g of base oil and solid lubricant, and disperse and grind through post-processing equipment before canning the finished product.

[0057] Example 3

[0058] This embodiment provides an automotive EPS steering gear worm gear grease composition, comprising:

[0059] Thickener: 70 g, of which the mass ratio of 12-hydroxystearic acid to isostearic acid is 1:3, lithium hydroxide 9.99 g, water 50 g;

[0060] Base oil: 770g (PAO synthetic oil: 100%, base oil 40℃ kinematic viscosity: 46mm 2 / s, viscosity index is 135);

[0061] Solid lubricant: PTFE: 120g;

[0062] Oxidized polyethylene wax: 15g;

[0063] Antioxidant: 2,6-di-tert-butyl-p-cresol 10g;

[0064] Detergent dispersant: 15g of high base synthetic calcium sulfonate;

[0065] This embodiment further provides a method for preparing the above-mentioned automotive EPS steering gear worm gear grease composition, specifically:

[0066] Add 385g of base oil and all the 12-hydroxystearic acid and isostearic acid into a reactor and heat it to 90-95°C. Add all the lithium hydroxide solution at 105-110°C and react for 45-60min. After the reaction is completed, heat it to 200-205°C, add 256g of base oil and cool it down. When the temperature drops below 140°C, add all the antioxidants, cool it down to below 80°C, add 129g of base oil, solid lubricant and detergent dispersant, and disperse and grind it through post-processing equipment before canning the finished product.

[0067] Example 4

[0068] This embodiment provides an automotive EPS steering gear worm gear grease composition, comprising:

[0069] Thickener: 70 g, of which the mass ratio of 12-hydroxystearic acid to isostearic acid is 3:1, lithium hydroxide 9.72 g, water 48.6 g;

[0070] Base oil: 760g (PAO synthetic oil: 100%, base oil 40℃ kinematic viscosity: 32mm 2 / s, viscosity index is 129);

[0071] Solid lubricant: MCA: 120g;

[0072] Oxidized polyethylene wax: 10g;

[0073] Antioxidant: diphenylamine 10g;

[0074] Detergent dispersant: 30g of high base synthetic calcium sulfonate;

[0075] This embodiment further provides a method for preparing the above-mentioned automotive EPS steering gear worm gear grease composition, specifically:

[0076] Add 380g of base oil and all the 12-hydroxystearic acid and isostearic acid into a reactor and heat it to 90-95°C, add all the lithium hydroxide solution at 105-110°C and react for 45-60min; after the reaction is completed, heat it to 200-205°C, add 253g of base oil and cool it down, add all the antioxidants when the temperature drops below 140°C, cool it down to below 80°C, add 127g of base oil, solid lubricant and detergent dispersant, and after dispersion and grinding by post-processing equipment, the finished product is canned.

[0077] Example 5

[0078] This embodiment provides an automotive EPS steering gear worm gear grease composition, comprising:

[0079] Thickener: 65 g, of which the ratio of 12-hydroxystearic acid to isostearic acid is 3:2, lithium hydroxide 9.11 g, water 45.5 g;

[0080] Base oil: 810g (PAO synthetic oil: 100%, base oil 40℃ kinematic viscosity: 32mm 2 / s, viscosity index is 129);

[0081] Solid lubricant: PTFE: 70g;

[0082] Oxidized polyethylene wax: 15g;

[0083] Antioxidant: diphenylamine 10g, 2,6-di-tert-butyl-p-cresol 10g;

[0084] Detergent dispersant: 20g of high base synthetic calcium sulfonate;

[0085] This embodiment further provides a method for preparing the above-mentioned automotive EPS steering gear worm gear grease composition, specifically:

[0086] Add 405g of base oil and all the 12-hydroxystearic acid and isostearic acid into a reactor and heat it to 90-95°C. Add all the lithium hydroxide solution at 105-110°C and react for 45-60min. After the reaction is completed, heat it to 200-205°C, add 270g of base oil and cool it down. When the temperature drops below 140°C, add all the antioxidants, cool it down to below 80°C, add 135g of base oil, solid lubricant and detergent dispersant, and disperse and grind it through post-processing equipment before canning the finished product.

[0087] Example 6

[0088] This embodiment provides an automotive EPS steering gear worm gear grease composition, comprising:

[0089] Thickener: 60 g, of which the mass ratio of 12-hydroxystearic acid to isostearic acid is 3:1, lithium hydroxide 8.34 g, water 41.7 g1;

[0090] Base oil: 825g (PAO synthetic oil: 100%, base oil 40℃ kinematic viscosity: 32mm 2 / s, viscosity index is 129);

[0091] Solid lubricant: MCA: 85g;

[0092] Oxidized polyethylene wax: 15g;

[0093] Antioxidant: diphenylamine 5g;

[0094] Detergent dispersant: high base synthetic calcium sulfonate 10g;

[0095] This embodiment further provides a method for preparing the above-mentioned automotive EPS steering gear worm gear grease composition, specifically:

[0096] Add 412g of base oil and all the 12-hydroxystearic acid and isostearic acid into a reactor and heat it to 90-95°C. Add all the lithium hydroxide solution at 105-110°C and react for 45-60min. After the reaction is completed, heat it to 200-205°C, add 275g of base oil and cool it down. When the temperature drops below 140°C, add all the antioxidants, cool it down to below 80°C, add 138g of base oil, solid lubricant and detergent dispersant, and disperse and grind it through post-processing equipment before canning the finished product.

[0097] Comparative Example 1

[0098] This comparative example provides an automotive EPS steering gear worm gear grease composition, which is different from Example 1 only in that the thickener is 12-hydroxystearate lithium soap, 70 g.

[0099] The preparation method of the above-mentioned automotive EPS steering gear worm gear grease composition is the same as that of Example 1.

[0100] Comparative Example 2

[0101] This comparative example provides an automotive EPS steering gear worm gear grease composition, which differs from Example 1 only in that the grease composition does not contain oxidized polyethylene wax, which is replaced by an equal amount of base oil.

[0102] The preparation method of the above-mentioned automotive EPS steering gear worm gear grease composition is the same as that of Example 1.

[0103] Comparative Example 3

[0104] This comparative example provides an automotive EPS steering gear worm gear grease composition, which is different from Example 1 only in that the oxidized polyethylene wax in the grease composition is replaced by polyethylene wax.

[0105] The preparation method of the above-mentioned automotive EPS steering gear worm gear grease composition is the same as that of Example 1.

[0106] Comparative Example 4

[0107] Comparative Example 4 is a special grease for imported automobile EPS steering gear worm gear. According to the product MSDS and component analysis, it is preliminarily determined that it includes at least 8% 12-hydroxystearate lithium soap thickened 80% PAO base oil, 10% PTFE solid lubricant, 1% alkyl diphenylamine antioxidant and 1% zinc cyclohexanecarboxylate rust inhibitor.

[0108] Test example

[0109] The lubricant compositions of Examples 1-6 and Comparative Examples 1-3 were evaluated for low temperature starting performance, anti-wear performance, lubricity, friction reduction, stick-slip test, and noise endurance bench test.

[0110] Among them, the evaluation method of each performance is as follows:

[0111] 1. Low temperature starting performance is determined by the low temperature torque of the grease at -40°C;

[0112] 2. Lubricity and friction reduction are evaluated by SRV high frequency linear vibration instrument;

[0113] 3. The dynamic and static friction coefficient is measured by LFW#1 testing machine: test temperature: 25℃; load: 196N; speed: 0.37mm / s; test ring: SAE4620; test block: PA66GF30;

[0114] 4. Stick-slip and durability bench test of automotive EPS worm gear grease.

[0115] The specific test results are shown in Table 1.

[0116] Table 1

[0117]

[0118]

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. Application of a grease composition in a worm gear of an automobile EPS steering gear, characterized in that: The grease composition comprises the following components in parts by weight: Base oil 77-85 parts, Thickener 6-9 parts, 8-12 parts of solid lubricant, 0.5-2.0 parts of oxidized polyethylene wax; The thickener is a mixture of 12-hydroxystearate lithium soap and isostearate lithium soap, the mass ratio of 12-hydroxystearate lithium soap to isostearate lithium soap is 3:1 to 1:3, and the amount of oxidized polyethylene wax is 0.5 to 2.0 wt% based on the total amount of the grease composition; The average molecular weight of the oxidized polyethylene wax is 2000-10000; the solid lubricant is a mixture of PTFE and MCA; the mass ratio of PTFE to MCA is 4:1-1:1; The base oil is a poly-alpha olefin synthetic oil, and the kinematic viscosity of the base oil at 40° C. is 16 to 48 mm 2 / s, the solidification point is not higher than -55℃, and the viscosity index is not less than 120.

2. The grease composition according to claim 1, characterized in that The average molecular weight of the oxidized polyethylene wax is 5000-10000.

3. The grease composition according to claim 1 or 2, characterized in that: The grease composition also includes a detergent dispersant, which is a high-alkalinity synthetic calcium sulfonate with a total alkalinity greater than 300 mgKOH / g.

4. The grease composition according to claim 3, characterized in that Based on the total amount of the grease composition, the amount of the detergent dispersant is 1.0-2.0 wt %.

5. The grease composition according to claim 1 or 2, characterized in that: The grease composition also includes an antioxidant, which is an amine antioxidant and / or a phenolic antioxidant; the amine antioxidant is selected from one or two of alkylated diphenylamine, naphthylamine and p-phenylenediamine; the phenolic antioxidant is one or two of 2,6-di-tert-butyl-p-cresol or α-naphthol.

6. The grease composition according to any one of claims 1 or 2, characterized in that: Contains the following components by weight: Base oil 77-85 parts, Thickener 6-9 parts, 8-12 parts of solid lubricant, Oxidized polyethylene wax 0.5~2.0 parts, Antioxidant 0.5~2.0 parts, 1 to 3 parts of detergent and dispersant.

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