JP2018080285A - Ester oil based lubricant and method for producing the same, and mechanical part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a lubricant that is excellent in low frictional property and in which early detachment due to hydrogen embrittlement at the contact part where two objects slide can effectively be prevented by the improvement of a base oil; a method for producing the same; and a mechanical part using said lubricant.SOLUTION: Provided is a lubricant used for lubricating contact part where two objects slide, said lubricant is an ester oil-containing lubricant and said ester oil is an ester oil that is given a thermal hysteresis at a high temperature equal to or lower than its flash point (for example, the flash point of the ester oil is 200 to 320°C, the high temperature is within 150°C of the flash point, and the time to give the thermal hysteresis is 100 hours or more), and it is used as a base oil or the like of a grease 7 to be included in a rolling shaft bearing 1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ester oil-based lubricant and a method for producing the same, and more particularly, to a lubricant used for lubricating a contact portion in a machine part in which two objects slide, and a method for producing the same.

  When mechanical parts such as rolling bearings and gears are used under conditions involving slippage, the lubricant is decomposed to generate hydrogen. When this hydrogen penetrates into the steel, it may cause early peeling due to hydrogen embrittlement. This is because when metal contact occurs at the contact surface between the contact elements and the new metal surface is exposed, generation of hydrogen by decomposition of the lubricant and penetration of the hydrogen into the steel are promoted. Since hydrogen significantly reduces the fatigue strength of steel, it can cause early damage when hydrogen penetrates even at a maximum contact surface pressure that is not so large. Among hydrogen that has penetrated into steel, diffusible hydrogen is considered to be a cause of hydrogen embrittlement.

  Motors for electrical equipment used in automobiles, drive motors for electric cars and hybrid cars, servo motors, motors for industrial machines such as stepping motors, and other motors such as motors for household appliances are being downsized. Yes. Along with this, miniaturization of motor bearings that support the rotor of the motor has been promoted. For this reason, the contact surface pressure applied to the members constituting the motor bearing tends to increase. In addition, the speed of rotation of the motor has been increased, and the acceleration / deceleration of the rotation of the motor bearing tends to increase when the motor is started and stopped. Furthermore, there is a demand for higher performance including extending the high-temperature life, reducing rotational torque, and improving quietness.

  These motor bearings (rolling bearings) are lubricated by sealing grease around the rolling elements. However, due to the severe use conditions accompanying the above-mentioned demands for miniaturization and high performance, there is a risk that specific peeling accompanied by a change in white structure may occur at an early stage on the rolling surface of the rolling bearing. This peeling is considered to be early peeling due to the hydrogen embrittlement described above. For example, when grease is decomposed and hydrogen is generated and invades into the steel of the rolling bearing, early peeling due to hydrogen embrittlement can occur.

  As a countermeasure against such early peeling, it has been proposed to add a predetermined zinc compound to grease used for lubrication (see Patent Document 1). This technology pays attention to the reaction mechanism during steel corrosion, and by mixing zinc compounds such as zinc dialkyldithiophosphate, zinc dialkyldithiocarbamate, and zinc oxide in grease, it prevents the adsorption of hydrogen to the steel, and early It is said that peeling can be prevented.

JP 2004-323586 A

  It can be said that it is effective to take measures against early peeling by variously examining the additive of the lubricant according to the use and use conditions as in Patent Document 1. However, many studies have been made on such additives, but improvement of the base oil itself of the base lubricant has not been sufficiently studied. In particular, due to further severe use conditions associated with recent demands for miniaturization and higher performance of motors, conventional additives may be insufficient as a measure for preventing the above-described early peeling. In addition, depending on the type of base oil and the reforming method, the low torque and lubrication life required for the rolling bearing of the motor may not be ensured.

  The present invention has been made in order to cope with such a problem, and is excellent in low friction characteristics and effective in improving the base oil by early peeling due to hydrogen embrittlement at a contact portion where two bodies slide. It is an object of the present invention to provide a lubricant that can be prevented, a method for producing the same, and a machine component that uses the lubricant.

  The method for producing a lubricant according to the present invention is a method for producing a lubricant used to lubricate a contact portion where two objects slide, and the lubricant is a lubricant obtained by blending an ester oil or an ester. A grease obtained by blending an oil and a thickener, wherein the ester oil is given a heat history at a high temperature below the flash point of the ester oil before the blending.

  The flash point of the ester oil is 200 to 330 ° C., the high temperature is within 150 ° C. of the flash point, and the time for giving the thermal history is 100 hours or more. In particular, the high temperature is 120 ° C. to 180 ° C., and the time for giving the thermal history is 300 hours or more.

  The lubricating oil of the present invention is a lubricant used for lubricating a contact portion where two objects slide, and the lubricant is a lubricant containing an ester oil or a grease containing an ester oil and a thickener. The ester oil is characterized in that it is an ester oil given a thermal history at a high temperature below its flash point.

  The flash point of the ester oil is 200 to 330 ° C., and the high temperature is within 150 ° C. of the flash point.

The ester oil after the thermal history has a height ratio (A / B) between a peak A of 3527 cm ^{−1 and} a peak B of 1742 cm ⁻¹ in infrared absorption spectrum measurement of 0.12 or more. And

  The mechanical component of the present invention is a mechanical component comprising two objects that are in sliding contact with each other and a lubricant that lubricates these contact portions, and the lubricant is the lubricant of the present invention. It is characterized by. Further, the surface roughness of the contact part of the mechanical part is 0.01 μmRa or more and 0.6 μmRa or less.

  In the production method of the lubricant of the present invention, when producing an ester oil-based lubricant based on ester oil, the ester oil is given a thermal history at a high temperature below its flash point before blending in advance. When used in a contact portion (sliding portion) that slides, the amount of hydrogen generated from the lubricant can be reduced. For this reason, the hydrogen penetration | invasion amount to steel can be decreased and the early damage resulting from hydrogen embrittlement in this contact part in a machine part can be suppressed. Moreover, ester oil is excellent in low friction characteristics compared with mineral oil etc., and this can be maintained even after thermal deterioration giving a thermal history. As a result, by using the lubricant obtained by the production method of the present invention, it can be suitably used for machine parts (such as rolling bearings) that require low friction and low torque, and its life is extended. be able to.

  The flash point of the ester oil is 200 to 330 ° C., the high temperature during the heat history treatment is within 150 ° C. of the flash point, and the time for applying the heat history is 100 hours or more, so the amount of hydrogen generation is further reduced. be able to.

  Since the mechanical component of the present invention uses the above-mentioned lubricant that suppresses the amount of hydrogen generated to lubricate the contact portion of two objects that are in sliding contact with each other, early damage due to hydrogen embrittlement at the contact portion can be suppressed, Long service life.

It is sectional drawing of the deep groove ball bearing which is an example of the machine component of this invention. It is sectional drawing of the motor using the bearing of FIG. It is a figure which shows the outline | summary of a vacuum sliding test (measurement of the amount of hydrogen generation). It is a figure which shows a time-dependent change of a friction coefficient.

  The lubricant of the present invention is an ester oil-based lubricant used for lubricating a contact portion where two objects slide. Here, the ester oil used as the base oil of the lubricant is characterized in that an ester oil given a heat history at a high temperature below its flash point is used.

  The ester oil before giving the thermal history is not particularly limited as long as it is used in the field of the machine part. Ester oil is a compound that has an ester group in the molecule and is liquid at room temperature, and examples thereof include polyol ester oil, phosphate ester oil, polymer ester oil, aromatic ester oil, carbonate ester oil, and diester oil. It is done. Among these, polyol ester oil is preferable. Moreover, if it is ester oil, it is good also as mixed oil which combined multiple types of ester oil.

  The polyol ester oil is preferably a compound having a plurality of ester groups in a molecule obtained by a reaction between a polyol and a monobasic acid. The monobasic acid to be reacted with the polyol may be used alone or as a mixture. In the case of an oligoester, a dibasic acid may be used. Examples of the polyol include trimethylolpropane, pentaerythritol, dipentaerythritol, neopentyl glycol, 2-methyl-2-propyl-1,3-propanediol, and the like. Examples of the monobasic acid include monovalent fatty acids having 4 to 18 carbon atoms. For example, valeric acid, caproic acid, caprylic acid, enanthic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, tallow acid, stearic acid, caproleic acid, undecylenic acid, lindelic acid, tuzuic acid , Fizetheric acid, myristoleic acid, palmitoleic acid, petrothelic acid, oleic acid, elaidic acid, asclepic acid, vaccenic acid, sorbic acid, linoleic acid, linolenic acid, sabinic acid, ricinoleic acid and the like. Specific examples of the polyol ester oil include trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, and pentaerythritol pelargonate.

(For mixing oil, kinematic viscosity of the mixed oil) ester oil kinematic viscosity of the base oil as is preferably in the range of 30 to 70 mm ² / s at 40 ° C., and more preferably in a range of from 30 to 60 mm ² / s . By making the kinematic viscosity within the above range, it can be widely used as a lubricant.In particular, by applying it to a rolling bearing for motors, it is possible to reduce torque while preventing oil film breakage, and to reduce power loss during motor driving. Heat generation can be suppressed.

  Giving the ester oil a heat history means holding the ester oil in the air at a predetermined temperature for a predetermined time. The predetermined temperature here is a high temperature below the flash point. This means that the treatment is performed at a temperature close to the flash point. The temperature and time at which the thermal history is given are not particularly limited as long as the hydrogen generation amount is reduced as compared with the case where the thermal history is not given.

  For example, when the flash point of the ester oil is 200 to 330 ° C., the specific temperature condition for giving the heat history is within 150 ° C., preferably 120 to 180 ° C. of the flash point. More preferably, it is 140 to 160 degreeC. Moreover, specific time conditions for giving the thermal history are, for example, 100 hours or more, preferably 200 hours or more, and more preferably 300 hours or more. Further, the upper limit of the time may be in a range where the oxidative deterioration does not proceed remarkably, and is usually within 1000 hours.

Table 1 shows the influence of heat history conditions on components in ester oil. Table 1 shows the analysis results by infrared spectroscopy (IR) of ester oils that have been subjected to heat history treatment under different heat history conditions (time). Table 1 shows the height of 3527 cm ⁻¹ [Peak A], the height of 1742 cm ⁻¹ [Peak B], and the ratio thereof in the IR spectrum measurement. Here, the peak B is a peak derived from an ester bond, and the peak A is a peak derived from a hydroxyl group (OH stretching (association)). In this evaluation, the same ester oil as that used in Example 1 described later was used as the ester oil before the heat history treatment. As the heat history treatment, the heat history of each time shown in Table 1 at 150 ° C. (0 hour, 20 hours, 100 hours, 300 hours, 500 hours, 700 hours, where “0 hour” is no heat history) is given. It was a document.

  As shown in Table 1, it can be seen that the peak A is increased by increasing the heat history processing time. In terms of the ratio of the height to the peak B (A / B), it increases by increasing the processing time, and becomes 0.12 after 300 hours. As shown in Table 2 to be described later, it is understood that the generation of the amount of hydrogen during use can be suppressed by giving such a thermal history and increasing A / B.

  As the form of the lubricant of the present invention, there are (1) a lubricating oil containing the ester oil, and (2) a grease containing the ester oil and a thickener. Since the lubricant of the present invention is based on ester oil, in each case, the content of ester oil is 50% by mass or more, preferably 80%, based on the total amount of oil with other oils. The mass is not less than mass%, and most preferably is 100 mass% of ester oil.

  Further, the thickening agent in the case of (2) grease is not particularly limited, and general ones usually used in the field of grease can be used. For example, soap-type thickeners such as metal soaps and composite metal soaps, and non-soap-type thickeners such as benton, silica gel, urea compounds and urea / urethane compounds can be used. Examples of the metal soap include sodium soap, calcium soap, aluminum soap, and lithium soap. Examples of the urea compound and urea / urethane compound include diurea compounds, triurea compounds, tetraurea compounds, other polyurea compounds, and diurethane compounds. Among these, use of lithium soap, a diurea compound, etc. which are excellent in cost and heat-resistant durability is preferable.

  When the grease is used, the blending ratio of the thickener in 100 parts by weight of the base grease composed of the base oil such as ester oil and the thickener is 1 to 40 parts by weight, preferably 3 to 25 parts by weight. . If the content of the thickener is less than 1 part by weight, the thickening effect is reduced, making it difficult to form a grease. If the content exceeds 40 parts by weight, the obtained base grease becomes too hard and the desired effect is difficult to obtain. Become.

  The lubricant of the present invention may contain a known additive capable of preventing early peeling due to hydrogen embrittlement. For example, organic zinc compounds such as zinc dithiophosphate, zinc dithiocarbamate, and zinc phenate can be used. Examples of zinc dithiophosphate (ZnDTP) include zinc dialkyldithiodithiophosphate and zinc diaryldithiophosphate. In addition, a molybdenum compound may be blended for the purpose of stably reducing the wear amount of machine parts. Examples of the molybdenum compound include organic molybdenum compounds such as molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC).

  Moreover, you may make the lubricant of this invention contain well-known additives other than the above as needed. Examples of such additives include rust inhibitors such as dinonyl naphthalene sulfonate and sorbitan esters, antioxidants such as amines and phenols, corrosion inhibitors such as sodium nitrite and sodium sebacate, graphite And solid lubricants such as molybdenum disulfide, oily agents such as fatty acid amides, fatty acids, amines and fats, and viscosity index improvements such as polymethacrylate and polystyrene. In addition, these can be added individually or in combination of 2 or more types.

  The mechanical component of the present invention is a mechanical component comprising two objects that come into sliding contact with each other and a lubricant that lubricates these contact portions, and uses the lubricant of the present invention as a lubricant. . Specific mechanical parts include rolling bearings and gears. The material of the contact portion in the machine part is a steel material. For example, when the machine part is a bearing, the material of the steel material is high carbon chromium bearing steel (SUJ1, SUJ2, SUJ3, SUJ4, SUJ5, etc .; JIS G 4805), carburized steel (SCr420, SCM420, etc .; JIS G 4053), Stainless steel (SUS440C etc .; JIS G 4303), high speed steel (M50 etc.) are mentioned.

  Further, the surface roughness at the contact portion in the machine part affects the amount of hydrogen generation. Considering the amount of hydrogen generation and processing cost, the surface roughness is preferably 0.01 μmRa or more and 0.6 μmRa or less, more preferably 0.01 μmRa or more and 0.2 μmRa or less.

  Rolling bearings are used under the condition that metal contact occurs between contact elements due to their motion, and they are used in a condition that involves slipping. Therefore, hydrogen easily penetrates into the steel due to the exposure of the new metal surface on the steel member surface. It is a part that is susceptible to In particular, a rolling bearing for a motor has a large rapid acceleration / deceleration, and is liable to slip and is easily affected by hydrogen.

  An example of a rolling bearing which is a mechanical component of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of a rolling bearing (deep groove ball bearing). In the rolling bearing 1, an inner ring 2 having an inner ring rolling surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on the inner peripheral surface are arranged concentrically, and the inner ring rolling surface 2a and the outer ring rolling surface 3a A plurality of rolling elements 4 are arranged between the two. The rolling element 4 is held by a cage 5. If necessary, the axially opposite end openings 8 a and 8 b of the inner and outer rings are sealed by the seal member 6, and the grease 7 is sealed around the rolling element 4. Grease 7 is lubricated by interposing on the rolling surfaces of inner ring 2 and outer ring 3 and rolling element 4. As the grease 7, the above-described lubricant (grease) of the present invention can be used.

  An example of a motor to which the rolling bearing is applied is shown in FIG. FIG. 2 is a sectional view of the structure of the motor. The motor includes a stator 10 made of a magnet for a motor disposed on the inner peripheral wall of the jacket 9, a rotor 13 around which a winding 12 fixed to the rotating shaft 11 is wound, and a commutator fixed to the rotating shaft 11. 14, a brush holder 15 disposed on an end frame 17 supported by the jacket 9, and a brush 16 accommodated in the brush holder 15. The rotating shaft 11 is rotatably supported by the jacket 9 by a rolling bearing 1 and a support structure for the bearing 1. The bearing 1 is the rolling bearing of FIG.

  As rolling bearings for motors, in addition to deep groove ball bearings shown in FIG. 1, angular ball bearings, cylindrical roller bearings, tapered roller bearings, self-aligning roller bearings, needle roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings Thrust needle roller bearings, thrust spherical roller bearings, and the like can also be used. Among these, it is preferable to use a deep groove ball bearing having rotational accuracy at high speed, load resistance, and low cost.

  Motors to which such rolling bearings can be applied include motors for industrial machines such as motors for ventilation fans, blower motors for fuel cells, cleaner motors, fan motors, servo motors, stepping motors, starter motors for automobiles, electric power steering motors, steering Examples thereof include motors for electrical equipment such as adjustment tilt motors, blower motors, wiper motors, and power window motors, and drive motors for electric vehicles and hybrid vehicles. Further, the present invention can be applied to other motors used in an environment in which peeling on the bearing rolling surface due to hydrogen embrittlement is likely to occur.

  The lubricant of the present invention will be specifically described with reference to examples, but is not limited to these examples.

Examples 1 to 3
A thermal history was given to the ester oil (flash point: about 284 ° C.) shown in Table 2 in a thermostatic bath under the conditions (time and temperature) shown in Table 2 to obtain a predetermined lubricating oil. With respect to this lubricating oil, the following hydrogen generation amount was measured.

<Vacuum sliding test (measurement of hydrogen generation amount)>
Hydrogen generated during a sliding test under vacuum was measured with a mass spectrometer, and the influence of thermal history on the lubricating oil on the hydrogen generation from the lubricating oil was evaluated. FIG. 3 shows a schematic diagram of the testing machine. The test piece 31 was a SUJ2 disc made of standard quenching and tempering with a diameter of 24 mm and a thickness of 10 mm, and finished to the surface roughness in Table 2. The counterpart material is a 1/4 inch steel ball 32 made of SUS440C. Three steel balls 32 were fixed to a steel ball holder 33, and the steel ball holder 33 and the steel ball holder 33 were attached to the rotating shaft at the upper part of the vacuum chamber. The rotating shaft is rotated by a motor 34. The test piece 31 was fixed to the test piece holder 35, and after placing the load spring 36 on the lower side, the pedestal was pushed up to load the load. The initial surface pressure was 2.0 GPa and the rotational peripheral speed was 0.1 m / s. 10 μL of the lubricating oil 37 shown in Table 2 was applied to the test piece 31. The sliding test was started after the degree of vacuum in the tank reached about 5.0 × 10 ⁵ Pa, and the sliding for 3 minutes and the pause for 2 minutes were repeated three times. The generated hydrogen is measured by measuring the ion current value of m / z = 2 (m: mass, z: charge) using the mass spectrometer 38, and the integrated value of the ion current increased during sliding. Was the hydrogen generation amount A · s (A: ampere, s: second). The results are shown in Table 2.

Comparative Examples 1 to 3
The ester oil shown in Table 2 was directly used as a lubricating oil without giving a heat history. For this lubricating oil, the same amount of hydrogen generation as in Example 1 was measured.

Comparative Example 4 to Comparative Example 9
Using the lubricating oil (mineral oil, synthetic hydrocarbon oil (PAO oil)) shown in Table 2, a thermal history was given under the conditions (time and temperature) shown in Table 2 to obtain a predetermined lubricating oil. For this lubricating oil, the same amount of hydrogen generation as in Example 1 was measured.

  As shown in Table 2, it can be seen that the amount of hydrogen generation can be reduced by giving a thermal history as compared with the case where no thermal history is given.

  Further, using the lubricating oils of Examples and Comparative Examples, they were subjected to the SRV frictional wear test shown below, and the friction coefficient was measured. Table 2 shows the average value of the friction coefficient between the test time of 25 minutes and 30 minutes. Moreover, the result of Example 1 at the time of a measurement and Comparative Examples 1, 4, and 7 is shown in FIG.

<SRV friction and wear test>
Test piece:
Ball diameter: 10 mm (SUJ2)
Disc plate diameter: 24mm x 7.85mm (SUJ2)
Evaluation conditions:
Load: 150N
Frequency: 10Hz
Amplitude: 1.2 mm
Time: 30 minutes Test temperature: 40 ° C

  As shown in FIG. 4, when the lubricating oil of the example was used, the coefficient of friction (a value that became constant within the measurement time) was about 0.08, which was more stable than the lubricating oil of the comparative example. It turns out that it is low. Moreover, it turns out from the comparison with Example 1 and the comparative example 1 that it is a low friction coefficient similarly after the thermal deterioration which gave the thermal history. For this reason, it turns out that it is excellent also in the low friction characteristic, giving a thermal history and suppressing the amount of hydrogen generation.

  The lubricant of the present invention has such a contact portion because it has excellent low friction characteristics and can effectively prevent early peeling due to hydrogen embrittlement at the contact portion where the two bodies slide, by improving the base oil. It can be widely applied to machine parts such as rolling bearings. In particular, a rolling bearing using the lubricant can be suitably used as a bearing for supporting a rotor of an industrial machine motor, an electrical equipment motor, or an electric vehicle driving motor.

DESCRIPTION OF SYMBOLS 1 Rolling bearing 2 Inner ring 3 Outer ring 4 Rolling body 5 Cage 6 Seal member 7 Grease 8a, 8b Opening 9 Jacket 10 Stator 11 Rotating shaft 12 Winding 13 Rotor 14 Commutator 15 Brush holder 16 Brush 17 End frame 31 Test Piece 32 Steel ball 33 Steel ball holder 34 Motor 35 Test piece holder 36 Load spring 37 Lubricating oil 38 Mass spectrometer

Claims (9)

A method for producing a lubricant used for lubricating a contact portion in which two objects slide.
The lubricant is a lubricant formed by blending an ester oil, or a grease formed by blending an ester oil and a thickener.
A method for producing a lubricant, wherein a thermal history is given to the ester oil at a high temperature below the flash point of the ester oil before the blending.   The lubrication according to claim 1, wherein the flash point of the ester oil is 200 to 330 ° C, the high temperature is within 150 ° C of the flash point, and the time for giving the thermal history is 100 hours or more. Manufacturing method.   The method for producing a lubricant according to claim 2, wherein the high temperature is 120 ° C. to 180 ° C., and the time for applying the thermal history is 300 hours or more. The ester oil after the thermal history is characterized in that the height ratio (A / B) between the peak A of 3527 cm ^{−1 and} the peak B of 1742 cm ⁻¹ in the infrared absorption spectrum measurement is 0.12 or more. The method for producing a lubricant according to any one of claims 1 to 3. It is a lubricant used to lubricate the contact area where two objects slide.
The lubricant is a lubricant containing an ester oil, or a grease containing an ester oil and a thickener, and the ester oil is an ester oil given a thermal history at a high temperature below its flash point. Lubricant characterized by   The lubricant according to claim 5, wherein the flash point of the ester oil is 200 to 330 ° C, and the high temperature is within 150 ° C of the flash point. The ester oil after the thermal history has a height ratio (A / B) between a peak A of 3527 cm ^{−1 and} a peak B of 1742 cm ⁻¹ in infrared absorption spectrum measurement of 0.12 or more. The lubricant according to claim 5 or 6. A machine component comprising two objects that make sliding contact and a lubricant that lubricates these contact parts,
The mechanical component according to claim 5, wherein the lubricant is a lubricant according to claim 5.   The machine part according to claim 8, wherein a surface roughness of the contact part of the machine part is 0.01 μmRa or more and 0.6 μmRa or less.

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