JP2006220281A - Bearing device for motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To resolve a problem in a conventional bearing device for a motor wherein reduction of friction generated in a sliding contact portion between a rotary shaft of the motor and a bearing rotatably holding it is desired. <P>SOLUTION: The device rotatably holds the rotary shaft 17 of the motor housed in a motor case 12 by the bearing 19, and the rotary shaft 17 slidably contacts the bearing 19 via grease using ester oil and/or ether oil as base oil. By forming a hard carbon thin film on a sliding contact face of at least one of the rotary shaft 17 and the bearing 19, and providing a hydrogen content of the hard carbon thin film at twenty atomic percent or less, extensive reduction of the friction in the sliding contact portion is realized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor bearing device suitable for use as a drive source of a valve device provided in an intake passage or the like in an automobile engine, for example.

  For example, a motor with a speed reduction mechanism is used as a drive source for an engine valve device. This type of motor is housed in a motor case together with a speed reduction mechanism including a worm gear fixed to the rotating shaft, and in such a motor with a speed reducing mechanism, a thrust load is generated on the rotating shaft due to rotation transmission via the worm gear. A thrust bearing (metal bearing) is provided in the motor case, and the rotating shaft is rotatably held by the thrust bearing.

Meanwhile, in recent years, global environmental issues such as the destruction of global warming and ozone layer are largely close-up, for inter alia the reduction of CO ₂ which is said to have great influence on the global warming, in various countries There is great interest in how to determine the regulation value. Regarding this CO ₂ reduction, it is one of the major issues to reduce the fuel consumption of automobiles, and in automobiles having various sliding mechanisms, a sliding mechanism with a low friction coefficient is realized to reduce fuel consumption. In addition, the sliding material and the lubricating oil play a large role.

  In automobiles, the role of sliding materials is to exhibit excellent wear resistance and low coefficient of friction for parts with severe frictional wear environment. Recently, various hard thin film materials have been applied. Yes. In general, hard carbon materials, particularly DLC (diamond-like carbon) materials, have a friction coefficient in the air or in the absence of lubricating oil, and wear-resistant hard coating materials such as titanium oxide (TiN) and chromium nitride (CrN). Therefore, it is expected as a low friction sliding material.

  In addition, as a fuel-saving measure for lubricating oils, 1) reduction of viscosity resistance in the fluid lubrication area by lowering the viscosity, 2) mixing and mixing under the boundary lubrication area by combining optimum friction modifiers and various additives Reduction of friction loss has been proposed, and as a friction modifier, many studies have been conducted focusing on organic molybdenum compounds such as molybdenum dithiocarbamate (MoDTC) and molybdenum dithiophosphate (MoDTP). On the sliding surface made of the material, a lubricating oil blended with an organomolybdenum compound exhibiting an excellent low friction coefficient at the beginning of use was applied, and the effect was improved.

For example, Non-Patent Documents 1 and 2 have been reported on the friction characteristics of such DLC materials and the performance of organic molybdenum compounds as friction modifiers.
Kano et al., Proceedings of Japan Society of Tribology, May 1999, p. 11-12 Kano et al., World Tribology Congress 2001.9, Vienna, Proceeding p. 342

  Incidentally, a motor bearing device used as a drive source of a valve device in an engine is naturally used in a high-temperature environment. However, when continuously operated in such an environment, oil shortage is likely to occur. There is a problem that the friction at the sliding contact portion between the rotating shaft and the bearing is increased, and the response and durability are lowered. For this reason, the improvement in reducing the friction in a sliding contact part was desired.

  Further, Non-Patent Document 1 reports that a general DLC material that is excellent in low friction in air does not necessarily have a large friction reducing effect in the presence of lubricating oil. According to No. 2, it has been found that even if a lubricating oil composition containing an organomolybdenum compound is applied to such a sliding material, the friction reducing effect may not be sufficiently exhibited.

  Furthermore, as described above, in the motor bearing device used in a high temperature environment, grease is used as a lubricant instead of lubricating oil, and the combined use of such grease and a hard carbon material such as DLC. Has not yet been considered.

  The present invention has been made in view of the above-described conventional situation. In an apparatus for rotatably holding a rotating shaft of a motor housed in a motor case with a bearing provided in the motor case, the rotating shaft and the bearing An object of the present invention is to provide a motor bearing device capable of realizing a significant reduction in friction by employing a hard carbon material and grease for the sliding contact portion.

  A motor bearing device according to the present invention is a device that rotatably holds a rotating shaft of a motor accommodated in a motor case by a bearing provided in the motor case, and the rotating shaft and the bearing are ester oil and / or It is in sliding contact via grease based on ether oil, a hard carbon thin film is formed on at least one sliding contact surface of the rotating shaft and the bearing, and the hydrogen content of the hard carbon thin film is 20 This is characterized in that it is not more than atomic%, thereby realizing a significant reduction in friction at the sliding contact portion between the rotating shaft and the bearing.

  A preferred embodiment of the motor bearing device according to the present invention is characterized in that the grease contains a metal soap or a urea compound containing calcium or lithium as a thickener.

  The motor bearing device of the present invention employs a hard carbon material such as DLC and a specific grease for the sliding contact portion between the rotating shaft of the motor and the bearing that rotatably holds the rotating shaft, so that the sliding contact is achieved. The friction of the part can be greatly reduced.

  This prevents problems such as seizure in the sliding contact portion between the rotating shaft and the bearing even when operated continuously in a high-temperature environment, thereby improving durability and extending the service life. The motor rotation speed and response speed can be improved and the torque can be improved, and the motor can be miniaturized. As a result, the flexibility of layout including peripheral devices can be improved, power saving and It can contribute to cost reduction.

  Hereinafter, the present invention will be described in more detail. In this specification, “%” represents a mass percentage unless otherwise specified.

  FIG. 1 is a view for explaining a motor with a speed reduction mechanism provided with a motor bearing device according to the present invention. As shown in FIG. 2, the illustrated motor M with a speed reduction mechanism is used as a drive source for a variable intake control valve (tumble control valve) that is an example of a valve device provided in an intake path of an automobile engine.

  The variable intake control valve is a butterfly type valve, and is provided in each intake passage corresponding to each cylinder in the intake manifold 1, and increases the length of the effective intake port by closing at low and medium speeds. Moreover, the length of the effective intake port is reduced by opening it at high speed, thereby improving the torque in each rotation region.

  The variable intake control valve includes a plate-like valve 4 that opens and closes a port 3 formed on the flange 2 of the intake manifold 1 and a valve shaft 5 that passes through the intake manifold 1 so as to pass through each port 3. The valve shaft 5 is rotatably held in the intake manifold 1, and the valve 4 is screwed to the valve shaft 5.

  The variable intake control valve has a bearing 6 and a lip seal 7 interposed between the end of the valve shaft 5 and the flange 2, and a motor M with a speed reduction mechanism is connected to the flange 2 via a packing 30. The output portion of the motor and one end portion of the valve shaft 5 are connected, and the valve shaft 5 and the valve 4 are integrally reciprocated by the motor M to open and close the port 3.

  The motor M with a speed reduction mechanism includes a motor case 12 that houses the motor body 11, an end bracket 13 that forms part of the motor case 12, a gear case 14 that houses the speed reduction mechanism, and an end of the gear case 14. An external appearance is constituted by the cap 15 fitted to the end bracket 13, and the end bracket 13 is integrally provided with a connector 16 for connection to an external power source (not shown). The motor body is not particularly limited, and may be various rotating machines such as a DC motor and a step motor.

  The motor body 11 includes a rotating shaft 17 that protrudes on both sides in the axial direction, and is biased toward the gear case 14 by a coil spring 18 provided in the end bracket 13. The rotating shaft 17 of the motor body 11 is made of various metal materials typified by iron-based alloys such as steel and non-ferrous metal alloys such as aluminum alloys, and is substantially inside the motor case 12 on the end bracket 13 side. A bearing 19 provided inside the end bracket 13 is rotatably held, and a worm gear 20 constituting a reduction mechanism is fixed to the gear case 14 side.

  Here, a thrust load is generated on the rotating shaft 17 by transmitting rotation through the worm gear 20. Therefore, the bearing 19 is a metal bearing that can cope with both a thrust load and a radial load. As a more preferable example, a metal bearing made of a sintered metal that can be impregnated with grease, which will be described later, is employed.

  In addition to the worm gear 20 described above, the speed reduction mechanism includes a transmission shaft 21 orthogonal to the rotation shaft 17 of the motor body 11 and an output shaft 22 parallel to the transmission shaft 21, and the transmission shaft 21 is connected to the worm gear 20. A helical gear 23 to be engaged and a pinion gear 24 that is coaxial with the helical gear 23 are provided, and an output gear 25 to be engaged with the pinion gear 24 is provided on the output shaft 22. Since the motor M performs reciprocal rotation, the output gear 25 has teeth only in a portion corresponding to the rotation range, and indirectly detects, for example, the opening degree of the valve 4 inside. A rotation detection sensor or the like can be provided.

  In the motor M with a speed reduction mechanism having the above-described configuration, the rotary shaft 17 and the bearing 19 are in sliding contact with each other in a bearing device that rotatably holds the rotary shaft 17 with the bearing 19. Therefore, in the bearing device, a hard carbon thin film having a hydrogen content of 20 atomic% or less is formed on at least one sliding contact surface between the rotary shaft 17 and the bearing 19, and the valve shaft 5 and the valve bearing portion 6 are formed. In between, a grease having a base oil of ester oil and / or ether oil is interposed, thereby greatly reducing friction at the sliding contact portion.

  Further, since the bearing device in the motor M with a speed reduction mechanism as described above is directly subjected to high-frequency vibration and pressure pulsation (low pressure side and high pressure side) of the engine and is used in a high temperature environment, such an environment is avoided. It is necessary to reduce the friction in consideration of the above. Table 1 shows examples of engine types, high-frequency vibrations, and pressure pulsations.

  Therefore, in the present invention, as described above, the sliding contact portion between the rotating shaft 17 and the bearing 19 has grease having a base oil based on ester oil and / or ether oil and a hydrogen content of 20 atomic% or less. By using the hard carbon thin film, the friction reduction of the sliding contact portion is realized even in the above environment.

  As a result, even when operated continuously in a high temperature environment, problems such as seizure in the sliding contact portion between the rotating shaft 17 and the bearing 19 can be prevented, and durability can be increased and a longer life can be realized. In addition, the motor rotation speed and response speed and torque can be improved to contribute to the improvement of engine performance, and the motor can be reduced in size. This can contribute to an improvement in layout flexibility, power saving and cost reduction.

  Further, with the reduction of friction, the effect of noise reduction can be obtained, and the temperature rise of the sliding contact portion can be suppressed, thereby enabling operation under a higher temperature environment. By using a metal bearing made of a sintered metal that can be impregnated with grease, it is possible to easily hold and lubricate the grease, and this also realizes improvement in durability.

  Examples of the hard carbon thin film include a crystalline or amorphous thin film containing carbon, in particular, a diamond thin film and a DLC thin film, such as various PVD methods, specifically, arc ion plating. A DLC thin film (diamond-like carbon thin film) formed by a method is desirable.

The DLC thin film is composed of a so-called DLC material, and this DLC material is an amorphous material mainly composed of carbon atoms, and the bonding form of the carbon atoms is a diamond structure (SP ³ Bond) and graphite bond (SP ² bond).

  Specifically, aC (amorphous carbon) consisting only of carbon atoms, aC: H (hydrogen amorphous carbon) containing hydrogen, and some metal atoms such as titanium (Ti) and molybdenum (Mo). In the present invention, the lower the hydrogen content, the more preferable. The hydrogen content is 20 atomic% or less, preferably 10 atomic% or less, particularly 0.5 atomic% or less, An aC-based (amorphous carbon-based) material that does not contain hydrogen can be preferably used.

  The film thickness of the hard carbon thin film is affected by the type and required performance of the target rotating shaft and bearing, the type of each material constituting the rotating shaft and bearing, and the surface roughness of the sliding part. In the case of a DLC thin film, for example, the thickness is preferably about 0.3 to 2.0 μm.

  In addition, the surface roughness of the base material before the formation of the hard carbon thin film is also the type and required performance of the target rotating shaft and bearing, the type of each base material constituting the rotating shaft and bearing, and the surface of the sliding portion. Although affected by roughness, etc., when applying the DLC thin film to the rotating shaft and bearing, if the base material is steel, the surface roughness before coating of the hard carbon thin film should be 0.1 μm or less in Ra It is preferable.

  Further, when the base material is an aluminum alloy, Ra is preferably 0.02 μm or less, and when the base material is plastic, Ra is preferably 0.1 μm or less.

  Furthermore, although the said hard carbon thin film is normally coat | covered on the whole at least one sliding surface of a rotating shaft and a bearing, you may coat | cover a part of at least one sliding surface.

  Next, as described above, the grease used is based on ester oil and / or ether oil, but this base oil is not limited to those containing only ester oil or ether oil. However, other natural oils and synthetic oils may be included. Examples of other base oil components include mineral oil, silicone oil, fluorocarbon oil, and the like.

  The ester oil is not particularly limited as long as it can be used as a component of a lubricant, but it is not limited whether it is a natural oil or a synthetic oil. Specific examples include ditridecyl glutarate, dioctyl adipate, diisodecyl adipate, ditrile. Examples include decyl adipate, dioctyl sebacate, trimethylolpropane caprylate, trimethylolpropane pelargonate, trimethylolpropane isostearinate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, and the like. Rate is preferably used.

  It does not matter whether the ether oil is a natural oil or a synthetic oil as long as it can be used as a component of a lubricant. Specific examples include polyoxyalkylene glycol, dialkyl diphenyl ether and polyphenyl ether, and dialkyl diphenyl ether is preferred.

The base oil containing the above components typically has a base oil viscosity at 100 ° C. of about ^{2 to} 100 mm ² / s, preferably about ² to 40 mm ² / s, more preferably about 10 to 20 mm ² / s. It becomes.

In addition, when kinematic viscosity is less than 2 mm < ² > / s, since sufficient abrasion resistance is not acquired and an evaporation characteristic may be inferior, it is unpreferable. On the other hand, if the kinematic viscosity exceeds 100 mm ² / s, it is difficult to exhibit low friction performance, and low temperature performance may be deteriorated, which is not preferable.

  The viscosity index of such base oil is typically 100 or more, preferably 120 or more, and more preferably 140 or more. By selecting a base oil having a high viscosity index, it is possible to obtain a composition that not only has excellent low-temperature viscosity characteristics, but also has low oil consumption and excellent low-temperature viscosity characteristics, fuel saving performance, and friction reduction effect.

  On the other hand, examples of the thickener contained in the grease include various metal soap-based materials and non-metal soap-based materials. Examples of the metal soap material include sodium, calcium, aluminum, lithium, barium, copper and lead salts of higher fatty acids, and complex salts of higher fatty acids with lower fatty acids or dibasic acids. As these metal soap materials, calcium stearate, lithium hydroxystearate, lithium stearate, sodium stearate and aluminum stearate are suitable.

  Non-metallic soap materials include inorganic materials (organic thickeners) such as silica gel and bentonite, and organic materials (inorganic thickeners) such as copper phthalocyanine, allylurea, imide derivatives and indanthrene blue. be able to. As these non-metallic soap thickeners, urea compounds such as diurea, sodium terephthalamate and PTFE are suitable.

  In the above-described grease, it is possible to add an antioxidant, a detergent, an antiwear agent, a solid lubricant and the like to the base oil and the thickener.

  The antioxidant is not particularly limited, and examples thereof include those conventionally used in greases. Examples thereof include amine compounds, phenols, sulfur compounds, and carbamates.

  In addition, the detergent is not particularly limited, and examples thereof include those conventionally used in greases. Examples thereof include sulfonates, phenates, sacylates, and amine compounds.

  The antiwear agent is not particularly limited, and examples thereof include those conventionally used in grease. Examples thereof include phosphate esters, zinc dialkyldithiophosphates, sulfur compounds, and chlorides.

  Furthermore, the solid lubricant is not particularly limited, and examples thereof include those conventionally used in grease.

  The properties of the above grease itself are affected by the purpose and operating conditions of the sliding mechanism used, but typically the consistency is about 265 to 295 and the dropping point is about 100 to 300 ° C. Is preferred.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

(Examples 1-4)
As shown in FIG. 3, a cylinder-shaped test piece 100 and a disk-shaped test piece 200 were made of SUJ2 steel in order to measure the friction coefficient using a cylinder-on-disk single-piece reciprocating friction tester. The cylindrical test piece 100 and the disk-shaped test piece 200 correspond to a rotating shaft and a bearing.

Next, the surface of the upper sliding surface of the disk-shaped test piece 200 is subjected to a PVD arc ion ion plating method with a hydrogen atom amount of 0.5 atomic% or less, a Knoop hardness Hk = 2170 kg / mm ² , and a surface roughness Ry = 0. A DLC thin film having a thickness of 03 μm and a thickness of 0.5 μm was formed, and the sliding mechanism of this example using the cylindrical test piece 100 and the disk-shaped test piece 200 as sliding members was manufactured.

  Next, about 0.3 g of the grease shown in Table 2 was applied between the cylindrical specimen 100 and the disk specimen 200, and a friction test was performed under the following conditions to measure the friction coefficient. Table 2 shows the components of the specimen material and grease. Further, the coefficient of friction of the sliding mechanism of each example after 10 minutes from the test was graphed and shown in FIG.

[Friction test conditions]
・ Test equipment: Cylinder-on-disk single-piece reciprocating friction tester ・ Sliding side test piece; φ15 × 22 mm cylindrical test piece ・ Math side test piece; φ24 × 7.9 mm disc-like test piece ・ Load; (Pressing load of one piece)
・ Amplitude: 1.5mm
・ Frequency: 50Hz
Test temperature: 80 ° C
・ Measurement time: 10 min

(Comparative Examples 1-6)
Except that no DLC thin film was formed on the disk-shaped test piece 200, the same operation as in Examples 1 to 4 was repeated, and the friction coefficient was measured. The obtained results are shown in FIG.

It is side sectional drawing (a) and a horizontal sectional view (b) explaining the motor with a speed reduction mechanism provided with the motor bearing device according to the present invention. It is a valve front view explaining the variable intake control valve which uses a motor with a deceleration mechanism as a drive source. FIG. 2 is a perspective view schematically illustrating a cylinder-on-disk single-piece reciprocating friction tester. It is a graph which shows a friction coefficient.

Explanation of symbols

M motor with reduction mechanism 11 motor body 12 motor case 13 end bracket (motor case 17 rotating shaft 19 bearing

Claims (9)

  An apparatus for rotatably holding a rotating shaft of a motor housed in a motor case by a bearing provided in the motor case, wherein the rotating shaft and the bearing are made of grease having ester oil and / or ether oil as a base oil. A hard carbon thin film is formed on at least one sliding contact surface of the rotating shaft and the bearing, and the hydrogen content of the hard carbon thin film is 20 atomic% or less. Motor bearing device.   2. The motor bearing device according to claim 1, wherein the hydrogen content of the hard carbon thin film is 10 atomic% or less.   2. The motor bearing device according to claim 1, wherein the hydrogen content of the hard carbon thin film is 0.5 atomic% or less.   The motor according to any one of claims 1 to 3, wherein the surface roughness of the substrate of the member on which the hard carbon film is formed is 0.1 µm or less in Ra before coating with the hard carbon thin film. Bearing device.   The motor bearing device according to any one of claims 1 to 4, wherein the grease comprises a metal soap containing calcium or lithium, or a urea compound as a thickener.   The motor bearing device according to claim 1, wherein the hard carbon thin film has a thickness of 0.3 to 2.0 μm.   The motor bearing device according to claim 1, wherein the hard carbon thin film is a DLC thin film formed by a PVD method.   8. The motor bearing device according to claim 1, wherein the bearing is a metal bearing made of sintered metal impregnated with grease.   The motor bearing device according to any one of claims 1 to 8, wherein the motor is a motor with a speed reduction mechanism used as a drive source of a valve device provided in an intake passage or the like of the engine.

Images