JP2009203812A - Bearing device for turbocharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device for a turbocharger allowing use of low cost material other than heat resistant steel for a rolling bearing by inhibiting temperature rise of the rolling bearing on a turbine wheel side and inhibiting drop of rotation accuracy of a rotary shaft of a turbocharger. <P>SOLUTION: This device is provided with a pair of angular ball bearings A, B supporting the rotary shaft 31 of the turbine wheel 32, and an inner ring spacer 6 is put between inner rings 2 of each angular ball bearing A, B. An annular uneven part 8 for accelerating heat radiation of the rotary shaft 31 is formed at least on an outer circumference part at the turbine wheel 32 side of the inner ring spacer 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a turbocharger bearing device that rotatably supports a rotating shaft of a turbocharger of an automobile.

In automobiles, turbochargers are widely used because they can further bring out engine performance. In this turbocharger, a bearing device provided with a rolling bearing is used to rotatably support the rotating shaft of the turbine wheel within the housing.
The turbine wheel receives a high-temperature and high-pressure exhaust from the engine and becomes very hot. Therefore, the heat of the turbine wheel is transmitted to the rolling bearing through the rotating shaft, and the temperature of the rolling bearing rises. In this case, the temperature of the rotating shaft is highest on the turbine wheel side and gradually decreases toward the compressor impeller side. For this reason, the rolling bearing on the turbine wheel side is particularly hot. Therefore, heat resistant steel materials such as heat resistant bearing steel are used for the inner ring of the rolling bearing on the turbine wheel side (see, for example, Patent Document 1).

JP 2002-48144 A

In the conventional turbocharger bearing device, since it is necessary to use an expensive heat-resistant steel material for the inner ring of the rolling bearing on the turbine wheel side, there is a problem that the material cost of the rolling bearing increases.
In addition, a large temperature difference occurs between the rolling bearing on the turbine wheel side and the rolling bearing on the compressor impeller side, and the rotational accuracy of the rotating shaft of the turbocharger is affected by the difference in thermal expansion amount of each rolling bearing due to this temperature difference. There was also the problem of a drop.

  The present invention has been made in view of such circumstances, can suppress the temperature rise of the rolling bearing on the turbine wheel side, can use an inexpensive material for the rolling bearing, It aims at providing the bearing device for turbochargers which can suppress the fall of the rotation precision of a rotating shaft.

  The turbocharger bearing device of the present invention is a turbocharger bearing device that rotatably supports a rotating shaft having a turbine wheel at one end and a compressor impeller at the other end in a housing. An inner ring fitted to the outer peripheral surface of the inner ring, an outer ring attached to the housing and arranged concentrically with the inner ring, and a plurality of rolling elements arranged to roll between the inner ring and the outer ring. At least a pair of rolling bearings, and an inner ring spacer disposed between the inner rings of the rolling bearing and fitted to the outer circumferential surface of the rotary shaft, the inner ring spacer being disposed on the outer circumference on the turbine wheel side, It has the annular uneven | corrugated | grooved part which accelerates | stimulates the thermal radiation of the said rotating shaft, It is characterized by the above-mentioned.

  According to this configuration, the heat of the rotating shaft on the turbine wheel side can be effectively radiated by the uneven portion of the inner ring spacer. Thereby, it can suppress that the temperature of the rolling bearing by the side of a turbine wheel raises greatly with the heat of a rotating shaft. For this reason, it is not necessary to use an expensive heat-resistant steel material for the inner ring of the rolling bearing on the turbine wheel side, and the material cost of the rolling bearing can be reduced.

  Moreover, the temperature difference between the rolling bearing on the turbine wheel side and the rolling bearing on the compressor impeller side can be reduced by suppressing the temperature rise of the rolling bearing on the turbine wheel side. As a result, the difference in the amount of thermal expansion due to the temperature difference between the two rolling bearings can be reduced, so that a reduction in the rotational accuracy of the rotating shaft can be suppressed.

  Further, in the turbocharger bearing device, an annular concavo-convex portion that promotes heat dissipation of the rotating shaft is formed on an outer periphery of the inner ring spacer on the compressor impeller side, and a heat dissipation area of the concavo-convex portion is determined by the turbine wheel. It may be smaller than the heat radiation area of the uneven portion on the side.

  In this case, since the heat of the rotating shaft can be radiated more effectively by the uneven portions on the turbine wheel side and the compressor impeller side, the rolling bearings on both the turbine wheel side and the compressor impeller side with the heat of the rotating shaft. It is possible to suppress an increase in temperature. For this reason, the amount of thermal expansion of the double rolling bearing can be reduced. Moreover, since the heat dissipation area of the uneven portion on the compressor impeller side is smaller than the heat dissipation area of the uneven portion on the turbine wheel side, the temperature rise of the rolling bearing on the turbine wheel side is further suppressed than the rolling bearing on the compressor impeller side, and the turbine A temperature difference between the rolling bearing on the wheel side and the rolling bearing on the compressor impeller side can be reduced. Thus, since the thermal expansion amount of both the rolling bearings on the turbine wheel side and the compressor impeller side can be reduced, the difference in the thermal expansion amount due to the temperature difference between the two rolling bearings can be reduced. Can be more effectively suppressed.

  According to the turbocharger bearing device of the present invention, it is possible to suppress an increase in temperature of the rolling bearing on the turbine wheel side. Therefore, it is necessary to use an expensive material such as heat-resistant bearing steel for the rolling bearing on the turbine wheel side. Therefore, the material cost of the rolling bearing can be reduced. In addition, since the temperature difference between the rolling bearing on the turbine wheel side and the rolling bearing on the compressor impeller side can be reduced, the difference in thermal expansion between both rolling bearings can be reduced, resulting in the rotation of the turbocharger. A reduction in rotational accuracy of the shaft can be suppressed.

Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 3 shows a schematic configuration of a turbocharger T in which the turbocharger bearing device 1 is incorporated in the housing H. The turbocharger T rotates the turbine wheel 32 fixed to one end (the right side in FIG. 3) of the rotating shaft 31 by the exhaust gas flowing through the exhaust passage 30. The rotation of the rotating shaft 31 is transmitted to the compressor impeller 33 fixed to the other end (left side in FIG. 3) of the rotating shaft 31, and the air sucked in the intake passage 34 is compressed by the compressor impeller 33. Thereby, the compressed air together with fuel such as gasoline and light oil is sent into the cylinder chamber of the engine. The rotating shaft 31 of such a turbocharger T rotates at a high speed of several tens of thousands to several tens of thousands of times / minute, and the rotation speed frequently changes according to the operating state of the engine. Therefore, the rotating shaft 31 is supported with respect to the housing H with a small rotational resistance by the turbocharger bearing device 1 incorporated in the housing H in order to reduce the rotation loss.

Next, the turbocharger bearing device 1 will be described.
FIG. 1 is a cross-sectional view showing a turbocharger bearing device 1 according to an embodiment of the present invention. As shown in the figure, the turbocharger bearing device 1 includes a pair of angular ball bearings A and B that rotatably support a rotating shaft 31 and an inner ring 2 between the pair of angular ball bearings A and B. The inner ring spacer 6 is disposed, and the outer ring spacer 7 is disposed between the outer rings 3 of the pair of angular ball bearings A and B.

  One angular ball bearing A of the pair of angular ball bearings A and B is disposed on the compressor impeller 33 side, and the other angular ball bearing B is disposed on the turbine wheel 32 side. Each of the angular ball bearings A and B includes an inner ring 2 having a raceway surface 2 a on the outer periphery and an inner periphery fitted to the outer periphery of the rotary shaft 31, and a raceway surface 3 a on the inner periphery and the outer periphery fitted in the housing H. The combined outer ring 3, a plurality of rolling elements 4 disposed so as to roll freely between the raceway surface 2a of the inner ring 2 and the raceway surface 3a of the outer ring 3, and holding for holding these rolling elements 4 at predetermined intervals And 5. The inner ring 2 and the outer ring 3 are each formed of bearing steel (SUJ-2), which is a bearing steel other than heat-resistant steel, carburized steel, or the like, and the rolling elements 4 are made of ceramic balls. Lubricating oil is supplied to the angular ball bearings A and B through an oil supply passage 35 provided in the housing H.

Referring also to FIG. 2, the inner ring spacer 6 is formed of a cylindrical body and is fitted to the outer peripheral surface of the rotating shaft 31 so as to be integrally rotatable. The inner ring spacer 6 has a first cylindrical portion 6a on the compressor impeller 33 side from the axial center and a second cylindrical portion 6b on the turbine wheel 32 side from the axial center, and each cylindrical portion 6a, 6b. Are integrally formed with each other.
An annular concavo-convex portion 8 for promoting heat dissipation of the rotating shaft 31 is formed on the outer peripheral portion of the second cylindrical portion 6b over the entire length. The uneven portion 8 is formed by forming slits at regular intervals on the outer peripheral portion of the second cylindrical portion 6b. The unevenness portion 8 increases the heat dissipation area of the second cylindrical portion 6b and enhances the heat dissipation effect. As a material for the inner ring spacer 6, it is preferable to use a material having a high heat dissipation effect such as an aluminum alloy.

  The outer ring spacer 7 is formed by projecting the inner peripheral surface of the housing H toward the inner ring spacer 6 side. A pair of angular ball bearings A, B is provided by disposing the angular ball bearings A, B with the end faces of the outer rings 3 of the angular ball bearings A, B in contact with both axial end surfaces of the outer ring spacer 7. Is positioned in the housing H. The outer ring spacer 7 may be formed of a cylindrical body formed separately from the housing H.

  According to the turbocharger bearing device 1 configured as described above, the heat transferred from the turbine wheel 32 heated by the exhaust heat of the engine to the rotary shaft 31 is provided on the second cylindrical portion 6 b of the inner ring spacer 6. The portion 8 can effectively dissipate heat. As a result, it is possible to prevent the angular ball bearing B on the turbine wheel 32 side from becoming high temperature in particular, and as a material for the inner ring 2 of the angular ball bearing B, inexpensive bearing steel such as rolling bearing steel or carburized steel is provided. Can be used. As a result, the material cost of the angular ball bearing B can be reduced.

  Moreover, since the temperature difference between the angular ball bearings A and B can be reduced by suppressing the temperature rise of the angular ball bearing B, the rotational shaft 31 of the rotating shaft 31 is caused by the difference in thermal expansion due to this temperature difference. It can suppress that rotation accuracy falls.

  FIG. 4 is a side view showing a turbocharger bearing device 1 according to another embodiment of the present invention. This embodiment differs from the embodiment shown in FIGS. 1 and 2 in that an annular uneven portion 9 for promoting heat dissipation of the rotary shaft 31 is provided on the outer peripheral portion of the first cylindrical portion 6a of the inner ring spacer 6. Is formed. That is, the inner ring spacer 6 shown in FIG. 4 has an uneven portion 9 of the first cylindrical portion 6a in addition to the uneven portion 8 of the second cylindrical portion 6b, and radiates heat compared to the inner ring spacer 6 shown in FIG. The area is further increased. Therefore, since the heat of the rotating shaft 31 can be radiated more effectively by the uneven portions 8 and 9, the temperature rises of the rotating shaft 31 and the angular ball bearings A and B can be more effectively suppressed. Can do. Thereby, the amount of thermal expansion of both angular ball bearings A and B can be made smaller than that of the embodiment shown in FIG.

  Further, the number of slits formed in the uneven portion 9 of the first cylindrical portion 6a is configured to be smaller than the number of slits formed in the uneven portion 8 of the second cylindrical portion 6b. For this reason, the heat dissipation area of the uneven portion 9 of the first cylindrical portion 6a is smaller than the heat dissipation area of the uneven portion 8 of the second cylindrical portion 6b. That is, the heat dissipation effect of the uneven portion 9 of the first cylindrical portion 6a is lower than the heat dissipation effect of the uneven portion 8 of the second cylindrical portion 6b. Thereby, since the temperature rise of the angular ball bearing B on the turbine wheel 32 side is further suppressed than the angular ball bearing A on the compressor impeller 33 side, the temperature difference between the angular ball bearings A and B can be reduced. . As a result, the difference between the thermal expansion amounts of the angular ball bearings A and B can be reduced.

  Thus, in this embodiment, the difference between the thermal expansion amounts of the angular ball bearings A and B can be reduced while reducing the thermal expansion amounts of the angular ball bearings A and B. A decrease in rotational accuracy can be more effectively suppressed.

  The present invention is not limited to the above embodiment. For example, the shape, arrangement, and number of components of the annular concavo-convex portions 8 and 9 are appropriately changed according to the use conditions and the like. Further, the angular ball bearings A and B may be implemented in a plurality of pairs.

It is sectional drawing which shows the bearing apparatus for turbochargers which concerns on one Embodiment of this invention. It is a principal part side view of the bearing apparatus for turbochargers of FIG. It is sectional drawing of a turbocharger. It is a principal part side view of the bearing apparatus for turbochargers which shows other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bearing device for turbochargers 2 Inner ring 3 Outer ring 6 Inner ring spacer 7 Outer ring spacer 8, 9 Concavity and convexity part 31 Rotating shaft 32 Turbine wheel 33 Compressor impeller A, B Angular contact ball bearing (rolling bearing)

Claims (2)

A turbocharger bearing device that rotatably supports a rotating shaft having a turbine wheel at one end and a compressor impeller at the other end in a housing,
An inner ring fitted to the outer peripheral surface of the rotating shaft, an outer ring attached to the housing and arranged concentrically with the inner ring, and a plurality of rolling elements arranged to roll between the inner ring and the outer ring And at least a pair of rolling bearings,
An inner ring spacer disposed between the inner rings of the rolling bearing and fitted to the outer peripheral surface of the rotary shaft;
A turbocharger bearing device, wherein the inner ring spacer has an annular concavo-convex portion that promotes heat dissipation of the rotating shaft on an outer periphery on the turbine wheel side. On the outer periphery of the inner ring spacer on the compressor impeller side, an annular concavo-convex portion that promotes heat dissipation of the rotating shaft is formed,
The turbocharger bearing device according to claim 1, wherein a heat radiation area of the uneven portion is smaller than a heat radiation area of the uneven portion on the turbine wheel side.

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