JP2006090402A - Turbocharger rotation supporting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent metal contact and thus wear between the outer peripheral face of a bearing housing and the inner peripheral face of a casing when starting/stopping an engine. <P>SOLUTION: This turbocharger rotation supporting device comprises a rotating shaft having a turbine fixed to one end and an impeller fixed to the other end, the bearing housing having a pair of rolling bearings provided at two places distant in the axial direction for rotatably supporting the rotating shaft, and the casing storing the bearing housing. A gap space formed between the outer peripheral face of the bearing housing and the inner peripheral face of the casing is filled with lubricating oil to form an oil film. A recessed portion is formed in the outer peripheral face of the bearing housing, which solves the problem. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rotation support device for a turbocharger, and more particularly to a rotation support device for a turbocharger in which wear of a bearing housing and a casing that houses the bearing housing is reduced.

In order to increase the engine output without changing the displacement, a turbocharger that compresses the air fed into the engine with the energy of the exhaust is widely used. The turbocharger collects exhaust energy by a turbine provided in the middle of the exhaust passage, and rotates an impeller of a compressor provided in the middle of the air supply passage by a rotating shaft fixed to the end of the turbine. The impeller rotates at a speed of tens of thousands to several ten thousand min ⁻¹ (rpm) as the engine is operated, and compresses air fed into the engine through the air supply passage.

  FIG. 3 shows an example of such a conventional turbocharger. FIG. 4 is a partially enlarged view of FIG. This turbocharger rotates the turbine 3 fixed to one end (left side in FIG. 3) of the rotating shaft 2 by exhaust gas flowing through the exhaust passage 1. The rotation of the rotating shaft 2 is transmitted to the impeller 4 fixed to the other end (right side in FIG. 3) of the rotating shaft 2, and the impeller 4 rotates in the air supply passage 5. As a result, the air sucked from the upstream end opening of the air supply passage 5 is compressed and sent together with fuel such as gasoline and light oil into the cylinder chamber (not shown) of the engine.

The rotating shaft 2 of such a turbocharger rotates at a high speed of tens of thousands to several tens of thousands of min ⁻¹ , and the rotation speed frequently changes according to the operating state of the engine. Therefore, it is necessary to support the rotating shaft 2 with a small rotational resistance with respect to the bearing housing 6. For this reason, conventionally, a configuration in which the rotary shaft 2 is rotatably supported by the first and second ball bearings 7 and 8 provided inside the bearing housing 6 has been adopted.

Further, an oil supply passage 19 is provided in a casing 18 in which the bearing housing 6 is housed, and the bearing housing 6 and the first and second ball bearings 7 and 8 can be cooled and lubricated. That is, when the engine equipped with the turbocharger is operated, the lubricating oil is removed of foreign matters by the filter 20 provided at the upstream end of the oil supply passage 19, so that the gap between the inner peripheral surface of the casing 18 and the outer peripheral surface of the bearing housing 6 is reduced. It is fed into the formed annular gap space 21. Then, by filling the gap space 21 with the lubricating oil, an oil film (oil film) is formed over the entire circumference between the outer peripheral surface of the bearing housing 6 and the inner peripheral surface of the casing 18, and the casing 18 and the bearing housing are formed. An oil film damper is configured that cools 6 and attenuates vibrations based on rotation of the rotating shaft 2. A turbocharger rotation support device having such a configuration is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-140888 (Patent Document 1).
JP 2001-140888 A

  However, since the oil film damper is made of engine oil circulating in the engine, a sufficient oil film is not formed when the engine is started or stopped. For this reason, when the engine is started or stopped, there is a problem that contact occurs between the outer peripheral surface of the bearing housing 6 and the inner peripheral surface of the casing 18, and the outer peripheral surface of the bearing housing 6 and the inner peripheral surface of the casing 18 wear. .

The abrasion powder generated in this way is mixed into the engine oil and circulates in the engine, and is caught in the first and second ball bearings 7 and 8, and the rolling surfaces of the balls 13 and 13 and the outer ring raceway 9. In addition, the inner ring raceway 11 may be damaged such as wear or indentation. If such damage occurs, vibration and noise may be generated from the first and second ball bearings 7 and 8 when the rotary shaft 2 rotates at a high speed of several tens of thousands to several ten thousand min ⁻¹ . This is not preferable because the reliability and durability of the turbocharger are lowered.

  Accordingly, an object of the present invention is to prevent metal contact between the outer peripheral surface of the bearing housing and the inner peripheral surface of the casing, and hence the occurrence of wear, when the engine is started and stopped.

  In order to solve the above-described problems, the present invention provides a rotating shaft having a turbine fixed at one end and an impeller fixed at the other end, and a pair of rolling bearings provided at two positions separated in the axial direction. A bearing housing that rotatably supports the rotating shaft, and a casing that accommodates the bearing housing, and a gap space formed between an outer peripheral surface of the bearing housing and an inner peripheral surface of the casing is made of lubricating oil. In the turbocharger rotation support device in which an oil film is formed by filling, a concave portion is formed on the outer peripheral surface of the bearing housing.

  With such a configuration, the recess formed in the outer peripheral surface of the bearing housing functions as an oil sump, and a sufficient oil film can be formed on the outer peripheral surface of the bearing housing even when the engine is started and stopped.

  According to the preferable aspect of the said invention, it is as follows. The diameter of the concave portion is preferably 0.1 to 100 μm, and more preferably 0.5 to 20 μm.

Further, the diameter of the recess is preferably a relationship expressed by the following formula (1) when expressed as a ratio of the rotation direction (Dr) and the axial direction (Dv) of the bearing housing in order to exert an oil sump function. It is.
Dv / Dr ≧ 1 (1)

  Moreover, it is preferable that the depth of the said recessed part is 0.1-20 micrometers.

  Moreover, it is preferable that the concave portion is filled with a solid lubricant. By filling such a solid lubricant, the solid lubricant filled in the recesses on the outer peripheral surface of the bearing housing gradually falls off due to centrifugal force of the rotating shaft, etc., and the inner peripheral surface of the casing and the outer peripheral surface of the bearing housing Wear caused by contact can be further reduced.

  The hardness of the solid lubricant is preferably 100 HV or less lower than the hardness of the outer peripheral surface of the housing. Thereby, even when a solid lubricant is used as shot grains in shot blasting or the like, deformation of the cage can be prevented.

  The rolling bearing is preferably a ball bearing, and the balls constituting the ball bearing are preferably made of ceramic. Thereby, the seizure resistance and heat resistance with the outer ring and the inner ring constituting the rolling bearing can be improved.

  In the turbocharger rotation support device according to the present invention, since the lubricating oil is held on the outer peripheral surface of the bearing housing by forming minute irregularities on the outer peripheral surface of the bearing housing, the outer peripheral surface of the bearing housing immediately after the start of engine operation. Even when the engine oil has spread over the inner peripheral surface of the casing, or even when the supply of engine oil cannot catch up with the rapid acceleration / deceleration of the engine, it is possible to ensure lubrication between components. As a result, it is possible to prevent foreign matter from getting into the rolling bearing, so that the reliability and durability of the turbocharger can be improved.

  Next, the rotation support device for a turbocharger according to the present invention will be described in more detail. FIG. 1 shows an example of an embodiment according to a rotation support device for a turbocharger of the present invention. The feature of the present invention is that the concave portion 42 functions as an oil sump by forming the concave portion 42 on the outer peripheral surface 41 of the bearing housing 40. It is in the point which forms a proper oil film. The overall structure of the turbocharger rotation support device includes the structure shown in FIG. 3 described above, and is the same as the conventionally known rotation support device, so the description of the equivalent parts is omitted or simplified. The description will focus on the features of the present invention.

  As shown in FIG. 1, a minute recess 42 is formed over the entire outer peripheral surface 41 of the bearing housing 40.

  The diameter of the minute recesses 42 provided on the surface is preferably 0.1 to 100 μm, and more preferably 0.5 to 20 μm. If the diameter is less than 0.1 μm, a sufficient oil sump function cannot be exhibited. On the other hand, if the diameter exceeds 100 μm, the roundness of the outer peripheral surface of the bearing housing deteriorates, and vibration is likely to occur.

  The depth of the recess 42 is preferably 0.1 to 20 μm, and more preferably 0.2 to 5 μm, from the viewpoint of the balance between roundness and oil film forming ability.

Further, the diameter of the concave portion 42 has a relationship represented by the following formula (1) when expressed as a ratio of the rotation direction (Dr) and the axial direction (Dv) of the bearing housing 40.
Dv / Dr ≧ 1 (1)

  That is, the shape of the formed recess 42 is an ellipse having a major axis in the axial direction (Dv). However, as long as the above conditions are satisfied, the shape is not limited to an ellipse, and may be, for example, a rectangle.

  Examples of the method for forming the minute concave portion 42 on the bearing housing outer peripheral surface 41 include shot peening and barrel processing.

  Materials for the bearing housing 40 include carbon steel for machine structure (S45C), high carbon chromium bearing steel, carburized steel, medium carbon alloy steel, steel for machine structure, high Si high temperature steel, stainless steel, M50 (AISI standard), SKH. Steel materials such as heat-resistant steel can be used. In order to improve the surface strength, it is preferable to perform carburizing treatment, nitriding treatment, or carbonitriding treatment.

A recess 42 formed in the outer peripheral surface 41 of the bearing housing 40 is filled with a solid lubricant 43. Here, the “solid lubricant” refers to a non-oil-soluble lubricant, and a commonly used solid lubricant can be used. Specifically, for example, polyethylene, fluororesin, nylon , Polyacetal, polyolefin, polyester, metal soap, MoS ₂ , WS ₂ , BN, graphite, calcium fluoride, barium fluoride, and the like.

  As a method for filling the concave portion 42 with the solid lubricant 43, there is a method in which the solid lubricant 43 is plastically deformed by shot peening, shot blasting, or the like, and mechanical engagement is used. Moreover, barrel processing can be performed as preprocessing, and then the solid lubricant 43 can be plastically deformed and filled.

  The solid lubricant 43 preferably has a hardness that is lower by 100 HV or more than the hardness of the outer peripheral surface 41 of the bearing housing 40. In mechanical parts such as a slide bearing and a rolling bearing, it is known that the lifetime is remarkably reduced when foreign matter is mixed. Further, when the solid lubricant 43 is filled in the recess 42 by shot blasting or the like, if the difference between the hardness of the solid lubricant 43 and the hardness of the outer peripheral surface 41 of the bearing housing 40 is less than 100 HV, the solid lubricant 43 is shot. When used as a grain, the bearing housing 40 may be deformed.

  For the reasons described above, a solid lubricant that has a hardness lower than 100 HV than the hardness of the outer peripheral surface 41 of the bearing housing 40 is selected as the solid lubricant that does not significantly reduce the life when it falls off from the recess 42. From the viewpoint described above, a more preferable solid lubricant has a hardness that is 300 HV or more lower than the hardness of the outer peripheral surface 41 of the bearing housing 40.

As the outer ring 10, the inner ring 12, and the balls 13, 13 constituting the first and second ball bearings 7 and 8 shown in FIG. 4, those having heat resistance are used. Outer ring 10 and inner ring 12 are 0.7 to 1.5% by weight of silicon (Si), 0.5 to 2.0% by weight of chromium (Cr), and 0.5 to 2.0%. High-Si high-temperature steel containing molybdenum (Mo) by weight, stainless steel, M50 (
AISI standard), steel materials such as heat-resistant steel such as SKH (high speed), or ceramic materials such as silicon nitride.

  When the steel material is used, it is preferable to perform carburizing treatment, nitriding treatment, or carbonitriding treatment to improve the surface strength. In particular, when performing nitriding treatment, it is preferable to treat at 480 ° C. or less by salt bathing treatment or gas nitriding treatment from the viewpoint of suppressing the hardness deterioration of the steel material base.

Further, the nitride layer formed by the nitriding treatment is made of d phase (Fe ₂ N), e phase (Fe ₂ N to Fe ₃ N), Y ′ phase (Fe ₄ N), CrN, and Cr ₂ N. If a large amount of at least one nitride is deposited on the martensite, the nitride layer can have extremely high hardness and toughness.

  When the ceramic material is used, it can be obtained by pressure sintering such as HIP method or gas pressure sintering method. Here, a columnar crystal having an average value of a width of 3 μm or less and a length of 4 μm or more in a columnar crystal containing 70% or more, preferably 90% or more of the entire silicon nitride grains can be preferably used. As long as the material satisfies the conditions, it may be pressureless sintered.

Further, when the weight criteria of the sintered body (100 wt%), as an auxiliary component, as up to 20 wt%, Al _2, O _3, MgO, a metal oxide CeO like, and Y ₂ O ₃ , Yb ₂ O ₃ , La ₂ O _{3 and} other rare earth oxides may be added to the ceramic material.

  In addition to such silicon nitride, it is preferable to use a silicon nitride sintered body having a high thermal conductivity because of excellent heat dissipation.

  Further, the balls 13 and 13 shown in FIG. 4 are made of the above-described steel material or ceramic material used for manufacturing the outer ring 10 and the inner ring 12 in consideration of seizure resistance and heat resistance with the outer ring 10 and the inner ring 12. Can do. Of course, when a steel material is used, the surface treatment as described above may be performed. Ceramic materials are preferred because they are excellent in seizure resistance and heat resistance.

  The cage 14 incorporated in the first and second ball bearings 7 and 8 can be made of a heat-resistant synthetic resin material mainly composed of polyimide. Considering heat resistance, lightweight alloys such as aluminum (Al) alloy, magnesium (Mg) alloy, and titanium (Ti) alloy, and metals such as copper (Cu) alloy and iron (Fe) alloy may be used. . However, the cage 14 made of metal alloy is excellent in heat resistance and strength, but is inferior in slidability as compared with the cage 14 made of synthetic resin. For this reason, it is preferable to subject the surface to oxidation treatment or nitridation treatment, or to form a soft coating such as lead (Pb) or silver (Ag) or a lubricating film such as DLC (diamond-like carbon).

  A bearing housing made of carbon steel for machine structure (S45C) was used, and concave portions were formed on the outer peripheral surface of the bearing housing by shot peening. The recess has a diameter in the rotational direction (Dr) of 5 μm, a diameter in the axial direction (Dv) of 6 μm (Dv / Dr = 1.2), and a depth of 2.5 μm.

  Next, molybdenum disulfide was used as a solid lubricant, and the recesses formed as described above were filled by shot peening. Note that molybdenum disulfide having a hardness 280 HV lower than the hardness of the outer peripheral surface of the bearing housing was used.

  A bearing housing made of carbon steel for machine structure (S45C) is used, and the shape of the recess is 10 μm in the rotational direction (Dr) and 13 μm in the axial direction (Dv) (Dv / Dr = 1.3). A bearing housing in which molybdenum disulfide was filled in the recesses on the outer peripheral surface was manufactured by the same treatment as in Example 1 except that the depth was 4 μm. The molybdenum disulfide having a hardness lower by 300 HV than the hardness of the outer peripheral surface of the bearing housing was used.

  A bearing housing made of carbon steel for machine structure (S45C) is used, and the shape of the recess is 5 μm in the rotational direction (Dr) and 6 μm in the axial direction (Dv) (Dv / Dr = 1.2). A bearing housing in which molybdenum disulfide was filled in the recesses on the outer peripheral surface was manufactured by the same treatment as in Example 1 except that the depth was 0.1 μm. The molybdenum disulfide used had a hardness 200 HV lower than the hardness of the outer peripheral surface of the bearing housing.

  A bearing housing made of carbon steel for machine structure (S45C) is used, and the shape of the recess is 10 μm in the rotational direction (Dr) and 11 μm in the axial direction (Dv) (Dv / Dr = 1.1). A bearing housing in which molybdenum disulfide was filled in the recesses on the outer peripheral surface was manufactured by the same treatment as in Example 1 except that the depth was 20 μm. The molybdenum disulfide having a hardness lower by 700 HV than the hardness of the outer peripheral surface of the bearing housing was used.

  A bearing housing made of carbon steel for machine structure (S45C) is used, and the shape of the recess is 5 μm in the rotational direction (Dr) and 9 μm in the axial direction (Dv) (Dv / Dr = 1.8). A bearing housing in which molybdenum disulfide was filled in the recesses on the outer peripheral surface was manufactured by the same treatment as in Example 1 except that the depth was 3 μm. The molybdenum disulfide having a hardness lower by 700 HV than the hardness of the outer peripheral surface of the bearing housing was used.

A bearing housing made of carbon steel for machine structure (S45C) is used, and the shape of the recess is 10 μm in the rotational direction (Dr) and 16 μm in the axial direction (Dv) (Dv / Dr = 1.6). A bearing housing in which molybdenum disulfide was filled in the recesses on the outer peripheral surface was manufactured by the same treatment as in Example 1 except that the depth was 2 μm. The molybdenum disulfide having a hardness lower by 500 HV than the hardness of the outer peripheral surface of the bearing housing was used.
[Comparative Example 1]

A bearing housing made of carbon steel for machine structure (S45C) was used, and molybdenum disulfide treatment was applied to the outer peripheral surface of the bearing housing without forming a recess. Note that molybdenum disulfide having a hardness 280 HV lower than the hardness of the outer peripheral surface of the bearing housing was used.
[Comparative Example 2]

Bearing housing in the same manner as in Comparative Example 1 except that a carbon steel (S45C) bearing housing for machine structure is used, and molybdenum disulfide having a hardness of 300 HV lower than the hardness of the outer peripheral surface of the bearing housing is used. Processed.
[Comparative Example 3]

Bearing housing in the same manner as in Comparative Example 1 except that a carbon steel (S45C) bearing housing for machine structure is used, and molybdenum disulfide having a hardness 80 HV lower than the hardness of the outer peripheral surface of the bearing housing is used. Processed.
[Comparative Example 4]

A bearing housing made of carbon steel for machine structure (S45C) is used, and the shape of the recess is 10 μm in the rotational direction (Dr) and 8 μm in the axial direction (Dv) (Dv / Dr = 0.8). A bearing housing in which molybdenum disulfide was filled in the recesses on the outer peripheral surface was manufactured by the same treatment as in Example 1 except that the depth was 0.8 μm. The molybdenum disulfide having a hardness lower by 700 HV than the hardness of the outer peripheral surface of the bearing housing was used.
[Comparative Example 5]

A bearing housing made of carbon steel for machine structure (S45C) is used, and the shape of the recess is 5 μm in the rotational direction (Dr) and 6 μm in the axial direction (Dv) (Dv / Dr = 1.2). A bearing housing in which molybdenum disulfide was filled in the recesses on the outer peripheral surface was manufactured by the same treatment as in Example 1 except that the depth was 4 μm. In addition, the molybdenum disulfide used the thing whose hardness is 80HV lower than the hardness of the outer peripheral surface of a bearing housing.
[Abrasion resistance test]

  A wear resistance test was performed by the following method using a Sabang type wear tester 30 as shown in FIG. A recess (not shown) was formed on the surface of the pin 31 under the same conditions as in Examples 1 to 6, and the recess was filled with molybdenum disulfide. Then, the counterpart material, that is, the ring-shaped test piece 32, was similarly subjected to lapping by using SUJ2 so that the roughness was 0.02 μmRa or less.

  Then, in order to reproduce the lubrication state at the time of starting and stopping the engine, a mineral oil-based commercial engine oil EO (trade name: Zepro SL, manufactured by Idemitsu Kosan Co., Ltd.) is dropped onto the ring-shaped test piece 32 at a rate of 10 μl / min. While applying a surface pressure N of 2.2 GPa, the pin 31 was rotated for 2000 m at a sliding speed of 1.2 m / s, and the wear amount (mg) of the pin 31 was measured. The test was performed five times, and the average value of the amount of wear of the pin 31 was determined. Then, a comparative evaluation was performed by calculating the specific wear area, where the wear area was 1 when the diameter of the minute unevenness was 100 μm.

The evaluation criteria are as follows.
A: Average wear amount is less than 0.05 mg B: Average wear amount is less than 0.05 to 0.1 mg C: Average wear amount is 0.1 mg or more

  The evaluation results are shown in Table 1. In the table, “Dv / Dr” means “diameter of the rotational direction (Dr) of the recess / diameter of the axial direction (Dv)”, and “(housing HV) − (solid lubricant HV)” means “bearing “Hardness of outer peripheral surface of housing−hardness of solid lubricant”.

  As shown in Table 1, a recess satisfying the condition of Dv / Dr ≧ 1 is provided on the surface of the pin 31, and the recess is filled with a solid lubricant having a hardness lower than 100 HV than the hardness of the outer peripheral surface of the bearing housing. As a result, a significant improvement in wear resistance was observed.

It is a figure which shows an example of embodiment which concerns on the rotation support apparatus for turbochargers of this invention. It is a figure for demonstrating an abrasion resistance test. It is a figure which shows an example of the conventional turbocharger. FIG. 4 is a partially enlarged view of the turbocharger of FIG. 3.

Explanation of symbols

1: exhaust passage, 2: rotating shaft, 3: turbine, 4: impeller, 5: air supply passage, 6: bearing housing, 7: first ball bearing, 8: second ball bearing, 10: outer ring, 11 : Inner ring raceway, 12: Inner ring, 13: Ball, 14: Cage, 18: Casing, 19: Oil supply passage, 20: Filter, 21: Crevice space, 30: Sabang type wear tester, 31: Pin, 32: Ring Test piece 40: bearing housing, 41: outer peripheral surface of bearing housing, 42: recess, 43: solid lubricant

Claims (7)

A rotating shaft having a turbine fixed to one end and an impeller fixed to the other end; and a bearing housing that rotatably supports the rotating shaft by a pair of rolling bearings provided at two positions spaced apart in the axial direction; A turbocharger in which an oil film is formed by filling a gap space formed between an outer peripheral surface of the bearing housing and an inner peripheral surface of the casing with a lubricating oil. In the rotation support device,
A rotation support device for a turbocharger, wherein a recess is formed on an outer peripheral surface of the bearing housing.   The turbocharger rotary support device according to claim 1, wherein a diameter of the concave portion is 0.1 to 100 μm. 3. The turbo according to claim 1, wherein the diameter of the recess is a relationship expressed by the following formula (1) when expressed by a ratio of a rotation direction (Dr) and an axial direction (Dv) of the bearing housing. Rotating support device for charger.
Dv / Dr ≧ 1 (1)   The rotation support device for a turbocharger according to any one of claims 1 to 3, wherein the depth of the recess is 0.1 to 20 µm.   The turbocharger rotary support device according to any one of claims 1 to 4, wherein the concave portion is filled with a solid lubricant.   The turbocharger rotary support device according to claim 5, wherein the hardness of the solid lubricant is 100HV or more lower than the hardness of the outer peripheral surface of the bearing housing. The rotation support device for a turbocharger according to any one of claims 1 to 6, wherein the rolling bearing is a ball bearing, and the balls constituting the ball bearing are made of ceramic.

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