JP2006037853A - Rotation support device for turbocharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation support device for a turbocharger capable of solving a defect occurred in a conventional turbocharger by rotatably supporting a rotary shaft built in the turbocharger and connected to a turbine and an impeller for a bearing housing installed in a casing. <P>SOLUTION: In the rotation support device 50 for the turbocharger, an intermediate part of the rotary shaft 2 securing the turbine 3 at one end and the impeller 4 at the other end respectively is rotatably supported by a pair of roller bearings at the inside diameter side of the bearing housing 6 installed in the casing 18 at two positions separated in the axial direction. A surface treating layer 51 is formed at the outer peripheral surface of the bearing housing 6 to reduce abrasion. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention, for example, is incorporated in a turbocharger for improving the output of an automobile engine, and rotatably supports a rotating shaft connecting a turbine and an impeller with respect to a bearing housing portion provided in the casing. The present invention relates to a rotation support device for a turbocharger that is used for the above.

Conventionally, in order to increase the output of an engine without changing the displacement, turbochargers that compress the air fed into the engine with the energy of the exhaust are 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 tens of thousands of min ⁻¹ (rpm) as the engine is operated, and compresses air fed into the engine through the air supply passage.

FIG. 2 shows an example of such a turbocharger. This turbocharger rotates the turbine 3 fixed to one end (the left end in FIG. 2) of the rotating shaft 2 by the 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 end in FIG. 2) 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 flow path 5 is compressed and sent into the cylinder chamber of the engine together with fuel such as gasoline and light oil. The rotating shaft 2 of such a turbocharger usually 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, the rotary shaft 2 needs to support the intermediate portion thereof with a small rotational resistance with respect to the bearing housing 6 provided in the casing 18. Therefore, the rotating shaft 2 is a pair of rolling bearings (for example, the first ball bearing 7 and the second ball bearing 8) provided at two positions separated from each other on the inner diameter side of the bearing housing 6 in the axial direction. ) Is supported rotatably.

Further, an oil supply passage 19 is provided in the casing 18 in which the bearing housing 6 is housed, and the bearing housing 6 and the first ball bearing 7 and the second ball bearing 8 can be cooled and lubricated. That is, when the engine equipped with the turbocharger is operated, the lubricating oil has foreign matters removed by the filter 20 provided at the upstream end of the oil supply passage 19, and the inner peripheral surface of the casing 18 and the outer peripheral surface of the bearing housing 6 Are fed into an annular gap space 21 provided between the two. The gap space 21 is provided by fitting the bearing housing 6 and the casing 18 with a gap. 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. An oil film damper is configured that cools the bearing housing 6 and attenuates vibrations based on the rotation of the rotating shaft 2. (For example, see Patent Document 1)
Japanese Patent Laid-Open No. 2003-83342

However, the turbocharger oil film damper described above lubricates the first ball bearing 7 and the second ball bearing 8 with engine oil that lubricates the inside of the engine. For this reason, there is a possibility that a sufficient oil film may not be formed when the engine is started and stopped. Therefore, when the engine is started and stopped, metal contact may occur between the outer peripheral surface of the bearing housing 6 and the inner peripheral surface of the casing 18, and wear may occur. The abrasion powder generated in this way is mixed into the engine oil and circulates in the engine, and is bitten by the first ball bearing 7 and the second ball bearing 8, and the first ball bearing 7 and There is a possibility that the second ball bearing 8 may be worn on the rolling surface of each ball, the outer ring raceway, and the inner ring raceway or may be damaged such as indentations. When such wear or damage occurs, vibration and noise are generated from the first ball bearing 7 and the second ball bearing 8 when the rotary shaft 2 is rotated at a high speed of several tens of thousands to several ten thousand min ^−1. There is a possibility that the reliability and durability of the turbocharger may be reduced.

  The present invention, when incorporated in such a conventional turbocharger, rotatably supports a rotating shaft that connects the turbine and the impeller with respect to a bearing housing portion provided in the casing. An object of the present invention is to provide a rotation support device for a turbocharger that can solve a problem occurring in the charger.

  In order to achieve this object, the present invention provides an inner diameter side of a bearing housing portion in which a turbine is fixed at one end, an impeller is fixed at the other end, and an intermediate portion of a rotating shaft fixed in the casing. A rotation support device for a turbocharger that is rotatably supported by a pair of rolling bearings provided at two positions separated in a direction, and a surface treatment layer for reducing wear is formed on an outer peripheral surface of the bearing housing portion. The rotation support device for turbochargers is provided.

  In the turbocharger rotation support device having this configuration, since the surface treatment layer for reducing wear is formed on the outer peripheral surface of the bearing housing portion, the outer peripheral surface of the bearing housing and the casing are immediately after the start of engine operation. Until the engine oil reaches the inner peripheral surface of the engine, or even when the engine oil supply cannot catch up due to sudden acceleration / deceleration of the engine, lubrication between the parts that are in friction with each other is ensured can do.

Examples of the surface treatment layer for reducing wear formed on the outer peripheral surface of the bearing housing portion include a reaction layer of a compound of sulfur and iron; a reaction layer of a compound of sulfur and iron containing nitrogen; Reaction layer of phosphate compound with iron; treated layer obtained by firing a single or mixture of molybdenum disulfide (MoS ₂ ) and polytetrafluoroethylene (PTFE) with a thermosetting synthetic resin; And a layer obtained by laminating a treatment layer obtained by firing a simple substance or a mixture of molybdenum disulfide and polytetrafluoroethylene together with a thermosetting synthetic resin on the surface of the reaction layer.

  Of the above-mentioned surface treatment layers, in particular, when a reaction layer of a compound of sulfur and iron is formed, a reaction membrane regeneration effect due to an ionic component contained in engine oil can be expected, which is preferable.

  In addition, as a surface treatment layer for reducing wear formed on the outer peripheral surface of the bearing housing portion, irregularities serving as oil sumps may be formed. In this way, immediately after the start of engine operation, until the engine oil reaches the outer peripheral surface of the bearing housing and the inner peripheral surface of the casing, or as the engine accelerates or decelerates suddenly, Even when the supply cannot catch up, the oil (lubricating oil) accumulated in the irregularities is held on the surfaces of the parts that rub against each other, so that good lubrication can be ensured.

  The irregularities are, for example, minute irregularities having a diameter of about 0.1 μm to 100 μm, preferably about 0.5 μm to 20 μm. When the uneven diameter is less than 0.1 μm, a sufficient oil sump effect tends not to be obtained. Further, if the diameter of the unevenness exceeds 100 μm, the shape of the outer peripheral portion of the bearing housing may be deteriorated, and vibration tends to be prevented.

  Further, when the length of the diameter of the unevenness is expressed as a ratio between the rotation direction (Dr) of the bearing housing and the vertical direction (Dv) of rotation, the oil sump effect is higher when Dv / Dr ≧ 1. This is preferable.

  Examples of the method for forming the minute irregularities on the outer peripheral surface of the bearing housing portion include shot peening and barrel treatment.

  Examples of the material constituting the bearing housing include high carbon chrome bearing steel, carburized steel, medium carbon alloy steel, steel for machine structure, high Si high temperature steel, stainless steel, M50 (AISI standard), heat resistant steel such as SKH, etc. The steel material can be used. Further, for the purpose of improving the surface strength of the bearing housing, carburizing treatment, nitriding treatment, or carbonitriding treatment may be performed.

  In the turbocharger rotation support device according to the present invention, a ball bearing can be used as the pair of rolling bearings. The outer ring, the inner ring, and the plurality of balls that are components of the ball bearing are heat resistant. That is, the outer ring and the inner ring 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% by weight. It is assumed that it is made of a high-Si high-temperature steel containing 5% molybdenum (Mo), a steel material such as stainless steel, M50 (AISI standard), heat-resistant steel such as SKH, or a ceramic material such as silicon nitride.

In addition, when using the steel material mentioned above, it is preferable to perform a carburizing process, a nitriding process, or a carbonitriding process for the purpose of improving surface strength. In particular, when such a nitriding treatment is performed, it is preferable to perform the treatment at 480 ° C. or less by salt bath nitriding treatment or gas nitriding treatment because the deterioration of hardness of the steel material base can be suppressed. Further, the nitrided layer formed by such nitriding treatment is divided into δ phase (Fe ₂ N), ε phase (Fe ₂ N to Fe ₃ N), γ ′ phase (Fe ₄ N), CrN, and Cr ₂ N. If a large amount of at least one of the nitrides is precipitated on the martensite, the nitride layer can have extremely high hardness and toughness.

  The silicon nitride is obtained, for example, by pressure sintering such as HIP method, gas pressure sintering method, etc., and columnar crystals grown into columnar shapes having an average value of width of 3 μm or less and length of 4 μm or more are formed of the entire silicon nitride grains. 70% or more, preferably 90% or more, can be preferably used. However, any material that satisfies the specific strength condition may be used at pressureless sintering.

Furthermore, the auxiliary component is selected from, for example, metal oxides such as Al ₂ O ₃ , MgO and CeO, and rare earth oxides such as Y ₂ O ₃ , Yb ₂ O ₃ and La ₂ O ₃ Can be used with an upper limit of 20% by weight of the entire sintered body. In addition to such silicon nitride, use of a silicon nitride sintered body having high thermal conductivity is preferable because of its excellent heat dissipation.

  In addition, in consideration of seizure between the outer ring and the inner ring, the ball which is a component of the ball bearing is made of a steel material or a ceramic material used as a material for forming the outer ring and the inner ring. You can also. Moreover, when the said ball | bowl is comprised with a steel material, surface treatment as mentioned above can also be given. A ceramic material is more suitable because it is excellent in seizure resistance and heat resistance.

  As the cage incorporated in the first ball bearing and the second ball bearing, for example, a heat-resistant synthetic resin material mainly composed of polyimide can be used, but considering heat resistance, aluminum (Al) Metal alloys such as alloys, lightweight alloys such as magnesium (Mg) alloys and titanium (Ti) alloys, copper (Cu) alloys, and iron (Fe) alloys may also be used. However, in the case of such a metal alloy cage, heat resistance and strength are excellent, but it is inevitable that the slidability is inferior to that of a synthetic resin cage. 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).

  In the turbocharger rotary support device according to the present invention, since the surface treatment layer for reducing wear is formed on the outer peripheral surface of the bearing housing portion, the rolling surface of the rolling element of the rolling bearing, the outer ring raceway and the inner ring raceway are provided. It is possible to prevent the occurrence of wear or damage such as indentation due to foreign matter contamination. Therefore, there is an effect that the reliability and durability of the turbocharger can be improved.

  Next, a turbocharger rotation support device according to a preferred embodiment of the present invention will be described with reference to the drawings. In addition, embodiment described below is the illustration for demonstrating this invention, and this invention is not limited only to these embodiment. Therefore, the present invention can be implemented in various forms without departing from the gist thereof.

  FIG. 1 is a partially enlarged cross-sectional view of a turbocharger rotation support device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the overall configuration of the turbocharger.

  A feature of the present invention is a rotation support device for a turbocharger that supports the rotation shaft of the turbocharger, and the rolling elements (balls) of the rolling bearings (first ball bearing 7 and second ball bearing 8). The object is to prevent wear on the moving surface, the outer ring raceway and the inner ring raceway, and damage such as indentation due to foreign matter contamination. The overall configuration of the turbocharger is the same as that shown in FIG. 2 described in the section of the background art described above. Therefore, the description of the equivalent part is omitted, and the following description will focus on the characteristic part of the present invention. .

  As shown in FIGS. 1 and 2, the turbocharger rotation support device 50 according to the present embodiment is housed in the bearing housing 6 and the bearing housing 6, and the turbocharger rotating shaft 2 (see FIG. 2). A first ball bearing 7 and a second ball bearing 8 that are rotatably supported are provided.

  As shown in FIG. 1, the first ball bearing 7 and the second ball bearing 8 include an outer ring 10 having an outer ring raceway 9 on an inner peripheral surface, an inner ring 12 having an inner ring raceway 11 on an outer peripheral surface, and these outer rings. A plurality of balls 13 are provided between the track 9 and the inner ring track 11 so as to be freely rollable. Further, each of these balls 13 is held in a plurality of pockets 15 provided in an annular retainer 14 so as to be able to roll one by one. Then, the rotary shaft 2 of the turbocharger is supported by the first ball bearing 7 and the second ball bearing 8 with a small rotational resistance with respect to the bearing housing 6.

  A surface treatment layer 51 that reduces wear is formed on the outer peripheral surface of the bearing housing 6. For this reason, immediately after the start of engine operation, the supply of engine oil cannot catch up until the engine oil reaches the outer peripheral surface of the bearing housing 6 and the inner peripheral surface of the casing 18 or due to sudden acceleration / deceleration of the engine. Even in this case, it is possible to ensure lubrication between the parts that are in friction with each other. Accordingly, it is possible to prevent the rolling surfaces of the balls 13 of the first ball bearing 7 and the second ball bearing 8, the outer ring raceway 9 and the inner ring raceway 11 from being worn, and damage such as indentation due to foreign matter contamination. be able to.

In addition, as the surface treatment layer 51 for reducing wear, as described above, for example, a reaction layer of a compound of sulfur and iron (sulfurization treatment); a reaction layer of a compound of sulfur and iron containing nitrogen ( (Sulfur nitriding treatment); reaction layer of phosphate compound of phosphorus and iron (phosphate treatment); simple substance of molybdenum disulfide (MoS ₂ ) and polytetrafluoroethylene (PTFE) (MoS ₂ · PTFE fired film), Alternatively, a treatment layer obtained by firing a mixture with a thermosetting synthetic resin; on the surface of one of the reaction layers, a single body or a mixture of molybdenum disulfide and polytetrafluoroethylene is fired with a thermosetting synthetic resin. And the like, and the like.

  Moreover, you may form the recessed part 52 and the convex part 53 which become an oil sump in the outer peripheral surface of the bearing housing 6 as shown in FIG. FIG. 3 is a perspective view showing a part of the outer peripheral surface of the bearing housing 6.

  Next, the following abrasion resistance test was performed using an ultra-high speed four-ball test similar to ASTM D 2596.

  First, four test balls (ball balls for ball bearings, SUJ2 1/2 inch) subjected to the surface treatment shown in Table 1 are prepared. A surface treatment layer 51 for reducing wear according to the present invention was formed on the surface of the test balls (Examples 1 to 4) subjected to the surface treatment.

  Next, among the four test balls, three test balls are arranged and fixed in an equilateral triangle shape so as to be in contact with each other, and the remaining one test ball is set in a recess formed at the center thereof. In order to reproduce the lubrication state at the start and stop of the engine for these test balls, 10 microliters of commercially available mineral oil-based engine oil (Zepro SL, manufactured by Idemitsu Kosan Co., Ltd.) After applying to Example 4), it was rotated for 5 minutes under constant conditions (surface pressure: 1.5 GPa, sliding speed: 1.5 m / s), and the wear areas of the three test balls fixed on the lower side were measured. did.

  The test was repeated 5 times, and the average value of the wear area of a total of 15 test balls was obtained. Evaluation was made into comparative evaluation by calculating the specific wear area of another Example by setting the wear area of Example 1 to 1. Also, NG was determined as the case where the test could not be continued for 5 minutes due to seizure. The results are shown in Table 1.

  Further, as a comparative example, the same test and the same evaluation were performed on a test ball (Comparative Example 1) that was not subjected to surface treatment. The results are shown in Table 1.

  From Table 1, the test balls subjected to the surface treatment (Examples 1 to 4) have a small amount of reproduction of the lubrication state at the start / stop of the engine as compared with Comparative Example 1 where the surface treatment is not performed. It can be seen that the wear resistance was remarkably improved under oil lubrication conditions. In particular, in the reaction layer of sulfur and iron compound (sulfurization treatment) and in the reaction layer of sulfur and iron compound containing nitrogen (sulfur nitriding treatment), a remarkable effect of improving wear resistance was recognized. It was.

  Next, four test balls (ball balls for ball bearings, SUJ2 1/2 inch) having minute irregularities (concave portions 52 and convex portions 53 as shown in FIG. 3) formed on the surface are prepared. These test balls were subjected to the same wear resistance test as that described above.

  The test was conducted 5 times, and the average value of the wear area of a total of 15 test balls was obtained. The evaluation was carried out as a comparative evaluation by calculating the specific wear area by changing the diameter of the concave and convex portions of minute irregularities as shown in FIG. 4 and assuming the wear area of a test ball having a diameter of 100 μm as 1. Also, NG was determined as the case where the test could not be continued for 5 minutes due to seizure. The result is shown in FIG.

  Further, as a comparative example, the same test was performed on a test ball having no irregularities on the surface, but the test could not be continued for 5 minutes due to seizure, resulting in NG.

  From Fig. 4, by providing minute unevenness on the surface of the test ball, this unevenness became an oil sump, and the wear resistance was remarkably improved under the minute oil lubrication conditions that reproduced the lubrication state at the start and stop of the engine. I understand.

It is a partial expanded sectional view of the rotation support device for turbochargers concerning an embodiment of the invention. It is sectional drawing which shows the whole structure of a turbocharger. It is a perspective view which shows a part of outer peripheral surface of a bearing housing. It is a figure which shows the relationship between the diameter of the uneven | corrugated recessed part formed in the surface of the test ball | bowl concerning embodiment of this invention, and a specific friction area.

Explanation of symbols

2 Rotating shaft 3 Turbine 4 Impeller 6 Bearing housing 7 First ball bearing 8 Second ball bearing 9 Outer ring race 10 Outer ring 11 Inner ring race 12 Inner ring 13 Ball 18 Casing 50 Rotating support device 51 for turbocharger 51 Surface treatment layer 52 Recess 53 Convex

Claims (4)

A turbine is provided at one end, an impeller is provided at the other end, and an intermediate portion of the fixed rotation shaft is provided at two positions on the inner diameter side of the bearing housing provided in the casing and separated in the axial direction. In the rotation support device for a turbocharger that is rotatably supported by a pair of rolling bearings,
A turbocharger rotation support device in which a surface treatment layer for reducing wear is formed on an outer peripheral surface of the bearing housing portion.   The rotation support device for a turbocharger according to claim 1, wherein the surface treatment layer is provided with unevenness that serves as an oil reservoir.   The turbocharger rotation support device according to claim 1 or 2, wherein the pair of rolling bearings are ball bearings. The rotation support device for a turbocharger according to claim 3, wherein the ball which is a component of the ball bearing is made of ceramic.

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