JP5071150B2 - Bearing device for turbocharger - Google Patents

Description

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

The turbocharger of an automobile has a turbine attached to one end of the rotating shaft and an impeller attached to the other end, and an intermediate portion of the rotating shaft is inserted into a hole in the housing of the turbocharger. The rotating shaft is rotatably supported by the bearing device.
Conventionally, as such a turbocharger bearing device, a single row of angular ball bearings is arranged on both sides in the axial direction of the rotary shaft, and between them, the coil that elastically energizes the outer ring of both angular ball bearings on both sides in the axial direction. The thing provided with the spring and the spacer is known (for example, refer patent documents 1 and 2).

In this conventional turbocharger bearing device, in order to rotate the ball stably, a large axial load is usually applied as a preload to the extent that the rotation axis of the ball is fixed in a certain direction by the coil spring.
JP 11-101128 A Utility Model Registration No. 2577011

However, in the above turbocharger bearing device, each ball rolls along the inner ring and outer ring track while rotating with the rotation axis oriented in a fixed direction, so only the same part around the equator corresponding to the rotation axis is used. Will come into contact with the inner and outer ring raceways.
Therefore, when lubricating oil mixed with hard foreign matter is supplied to the bearing device in such a rolling state, the foreign matter bites into the rolling part of the ball and circulates around the outer equator of the ball. Wear marks may occur, and abnormal sounds may occur due to the wear marks.

  In view of such problems, the present invention provides a turbocharger bearing device that can prevent the occurrence of band-like wear marks on the balls of an angular ball bearing and prevent or suppress the generation of abnormal noise. The purpose is to provide.

Conventionally, in a turbocharger bearing device, in order to rotate a ball stably, it has been common technical knowledge to apply a preload to the outer ring so that the rotation axis of the ball is fixed in a certain direction.
However, as a result of repeated extensive research conducted by the present inventors, if the preload of the outer ring is set simply considering only the stable rotation of the ball, as described above, when hard foreign matter is mixed in the lubricating oil. Have found that wear marks are likely to occur in the rolling part of the ball whose rotation axis does not change, and this causes abnormal noise.

  The present invention has been completed based on the above knowledge, and is a bearing device for a turbocharger that rotatably supports a rotating shaft of a turbocharger within a housing, and a pair of inner rings separated in the axial direction of the rotating shaft. An inner ring provided on the rotating shaft side having a track, a pair of outer rings provided on the housing side having an outer ring track facing the inner ring track, and a plurality of freely rotatable between the inner ring track and the outer ring track A pair of angular ball bearings, and a preload applying member that applies a constant pressure preload in the axial direction to each angular ball bearing to such an extent that the rotation axis of each ball is not fixed in a certain direction. It is characterized by that.

According to the present invention, the preload applying member applies a constant pressure preload to each angular ball bearing to such an extent that the rotation shaft of each ball is not fixed in a certain direction. Fluctuates with the passage of time.
For this reason, even if hard foreign matter is mixed in the lubricating oil supplied between the balls of the angular ball bearings and the inner ring and outer ring raceway, band-shaped wear marks are prevented from being generated on the outer peripheral surface of the balls as much as possible. It is possible to prevent or suppress the generation of abnormal noise associated with such wear marks.

Specifically, the preload applying member includes a pair of sleeves interposed between the pair of outer rings and a pair of sleeves for applying a preload in the axial direction to the outer rings via the sleeves. And a preload spring interposed between the two.
In this case, in order to apply constant pressure preload to each angular ball bearing to such an extent that the rotation axis of each ball is not fixed in a certain direction, the preload load in the axial direction by the preload spring is a range in which the following inequality (1) is satisfied. not good if set within.

ただし、Ｆａ：予圧荷重（Ｎ）、μ：玉と軌道面との転がり摩擦定数、ｄ：玉径（ｍｍ）、Ｄ：玉のＰＣＤ（Pitch Circle Diameter）（ｍｍ）、Ｚ：玉の個数、θ：軸受接触角（度）、ｎ：軸受回転数（ｍｉｎ^-1）である。

However, Fa: Preload (N), μ: Rolling friction constant between ball and raceway surface, d: Ball diameter (mm), D: Ball PCD (Pitch Circle Diameter) (mm), Z: Number of balls, θ: bearing contact angle (degrees), n: bearing rotation speed (min ⁻¹ ).

The right side of the inequality (1) is a dynamic formula for calculating the minimum axial load necessary for fixing the rotation axis of the ball of the angular ball bearing in a fixed direction.
Accordingly, the elastic constant, the natural length, the compression amount, etc. of the preload spring are set so that the preload load Fa is smaller than the minimum value of the axial load that can be calculated by the dynamic formula on the right side of the equation (1). Thus, the preload in the axial direction with respect to the angular ball bearing can be set to such an extent that the rotation axis of each ball is not fixed in a certain direction.

  As described above, according to the present invention, since a light preload that does not fix the rotation axis of the ball in a certain direction is applied, it is possible to prevent the formation of band-shaped wear marks on the ball, thereby causing abnormalities. The generation of sound can be suppressed or prevented.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an embodiment of a bearing device 1 for a turbocharger according to the present invention.
FIG. 2 is a cross-sectional view showing a schematic configuration of a turbocharger T in which the turbocharger bearing device 1 is incorporated.
As shown in FIG. 2, the turbocharger T of the present embodiment rotates a turbine 33 fixed to one end side (the right side in FIG. 2) of the rotating shaft 32 by the exhaust gas flowing through the exhaust passage 31. Yes.

The rotation of the rotating shaft 32 is transmitted to the impeller 34 fixed to the other end side (left side in FIG. 2) of the rotating shaft 32, and the impeller 34 rotates in the air supply passage 35.
As a result, the air sucked from the upstream opening of the air supply passage 35 is compressed, and the compressed air together with fuel such as gasoline and light oil is sent into a cylinder chamber of an engine (not shown).

The rotating shaft 32 of the turbocharger T rotates at a high speed of tens of thousands to tens of thousands (times / minute), and the rotation speed frequently changes according to the operating state of the engine. Therefore, the rotating shaft 32 is supported with respect to the housing 36 with a small rotational resistance by the turbocharger bearing device 1 provided in the housing 36 in order to reduce the rotation loss.
The turbocharger bearing device 1 includes a cylindrical bearing support portion 36a provided in a housing 36 of the turbocharger T, and is incorporated inside the cylinder. The rotating shaft 32 having the turbine 33 attached to one end and the impeller 34 attached to the other end is rotatably supported by the bearing device 1 at an intermediate portion thereof.

As shown in FIG. 1, the turbocharger bearing device 1 includes a pair of bearing support portions 36a and a pair of shaft support portions 36a provided apart from each other in the axial direction of a rotating shaft 32 inserted coaxially into the bearing support portion 36a. Ball bearings 2a and 2b (first ball bearing 2a and second ball bearing 2b) are provided.
An inner ring spacer 7 is interposed between the inner rings 3 of the ball bearings 2a and 2b. A pair of sleeves 8 are interposed between the outer rings 4 of the ball bearings 2a and 2b, and a preload is applied between the sleeves 8 on the first ball bearing 2a and the second ball bearing 2b. Is provided with a preload spring 9.

The first and second ball bearings 2a and 2b incorporated in the bearing support portion 36a in the housing 36 are both angular ball bearings, and the basic configurations of both are the same.
The first ball bearing 2a is disposed on the turbine 33 side (right side in FIG. 1) of the rotating shaft 32, and the second ball bearing 2b is disposed on the impeller 34 side (left side in FIG. 1) of the rotating shaft 32. Yes. The ball bearings 2a and 2b are respectively composed of inner rings 3 and 3 having an inner ring raceway 3a on the outer peripheral side, outer rings 4 and 4 having an outer ring raceway 4a on the inner peripheral side, and between the inner ring raceway 3a and the outer ring raceway 4a. And a plurality of balls 5 arranged so as to be able to roll.

The inner ring 3 is formed in an annular shape, and the inner ring raceway 3a formed on the outer periphery thereof is an angular type raceway having a predetermined radius of curvature, and its axis is directed obliquely inward.
The outer ring 4 is also formed in an annular shape, and an angular outer ring raceway 4a having a predetermined radius of curvature is formed on the inner periphery of the outer ring 4 so as to face the inner ring raceway 3a. And in the angular ball bearings 2a and 2b of this embodiment, the inner ring 3 and the outer ring 4 have a cross-sectional shape having a so-called counterbore without a shoulder on one side.

The balls 5 as rolling elements are each held in a plurality of pockets 6a provided in an annular retainer 6 so as to be able to roll one by one, and by this retainer 6, the inner ring raceway 3a and the outer ring raceway 4a. Are arranged at predetermined intervals along the circumferential direction in an annular space formed between the two.
Each of the first and second ball bearings 2 a and 2 b is supported by a bearing support portion 36 a provided inside the housing 36.

More specifically, the outer rings 4 and 4 of the ball bearings 2a and 2b are relatively loose with respect to the inner peripheral surfaces of the both ends of the bearing support 8 so that axial displacement with respect to the bearing support 8 is allowed. It is fitted inside.
Further, the inner rings 3 and 3 of the ball bearings 2a and 2b are externally fitted and fixed to the intermediate portion of the rotating shaft 32 in a state in which axial displacement with respect to the rotating shaft 32 is also restricted. An axially intermediate portion of the shaft 32 is rotatably supported on the bearing support portion 8 of the housing 36 by a pair of ball bearings 2a and 2b separated in the axial direction.

The pair of sleeves 8, 8 are interposed between the outer rings 4, 4 separated in the axial direction so that the axially inner ends 8 a face each other in the axial direction of the rotating shaft 32. Each of the sleeves 8 and 8 is formed in a cylindrical shape whose outer diameter is the same as the outer diameter of the outer ring 4, so that the outer peripheral surface of the sleeve 8 is flush with the outer peripheral surface of the outer ring 4.
Each sleeve 8, 8 has an oil hole 10 formed so as to penetrate from the outer peripheral surface toward the inner peripheral surface, and the oil hole 10 has a through outlet on the inner peripheral surface side in the vicinity of the inner ring raceway 3 a. It inclines with respect to radial direction so that it may be located in.

Further, a pin 40 is loosely fitted to the boundary surface between the outer peripheral surface of the sleeve 8 on the left side of FIG. 1 and the inner peripheral surface of the bearing support portion 36a, and the spacer 8 is connected to the bearing support portion 36a by the pin 40. Are positioned in the axial and circumferential directions.
A stepped portion 8b for forming an annular space for accommodating the preload spring 9 is formed on the inner peripheral side of the pair of sleeves 8 and 8 arranged in the axial direction and on the opposite end side in the axial direction. The stepped portion 8b has a diameter slightly larger than the diameter of the coiled preload spring 9, and is formed by notching the thickness of the inner peripheral side of the sleeves 8 and 8 in an annular shape.

The inner ring spacer 7 between the inner rings 3 and 3 is formed in a cylindrical shape whose inner diameter is the same as the inner diameter of the inner ring 3, and the inner peripheral surface of the inner ring spacer 7 is the same as the inner peripheral surface of the inner ring 3. It is one.
Further, in a state where the sleeves 8 and 8 are opposed to each other, an annular space is formed by the stepped portion 8b and the outer peripheral surface of the inner ring spacer 7, and the preload spring 9 is stored in a compressed state in the annular space. Yes. In addition,
A gap s having an axial length of about several tens of μm is provided between the end faces 8a facing each other in the axial direction of the sleeves 8 and 8.

As described above, the turbocharger bearing device 1 is mainly constituted by the bearing support portion 36a, the angular ball bearings 2a and 2b, the sleeve 8, and the preload spring 9.
As shown in FIG. 2, an oil supply passage 37 is provided in the housing 36 in which the bearing support portion 36 a is accommodated, and the ball bearings 2 a and 2 b are lubricated with the lubricating oil passing through the oil supply passage 37. Yes.

More specifically, the lubricating oil is removed from the inner peripheral surface of the bearing support portion 36a by the filter 38 provided on the upstream side of the oil supply passage 37 when the engine equipped with the turbocharger T is operated. It is fed into an annular gap space (not shown) that exists between the second ball bearings 2 a and 2 b and the outer peripheral surface of each sleeve 8.
The gap space is provided by fitting the bearing support portion 36a with the first and second ball bearings 2a, 2b and the sleeve 8.

Then, by filling the gap space with lubricating oil, an oil film (oil film) is formed over the entire circumference between the outer peripheral surfaces of the first and second ball bearings 2a and 2b and the sleeve 8 and the inner peripheral surface of the bearing support portion 36a. ) To prevent the vibrations of the first and second ball bearings 2a and 2b and the sleeve 8 from being transmitted to the bearing support portion 36a.
Thus, an oil film damper that attenuates vibration based on the rotation of the rotating shaft 32 is formed by the lubricating oil filled in the gap space.

A portion of the lubricating oil fed into the gap space has a diameter from the oil holes 10 formed in the sleeves 8 and 8 toward the outer peripheral surface of the inner ring 3 of the first and second ball bearings 2a and 2b. It is designed to erupt diagonally from outside the direction. Further, the lubricating oil ejected toward the first and second ball bearings 2 a and 2 b is discharged from the oil discharge port 39 of the housing 36.
In the turbocharger bearing device 1 according to the present embodiment, the first and second ball bearings 2a and 2b are arranged in a back-combined state in which the directions of the contact angles are opposite to each other. A constant pressure preload is applied.

That is, the preload spring 9 is composed of a coil spring that applies a preload (a constant pressure preload) in a direction in which the pair of outer rings 4 and 4 are separated from each other in the axial direction.
Specifically, the preload spring 9 made of a coil spring is in a compressed state in the annular space of the sleeves 8 and 8, and both sleeves 8 and 8 are brought into contact with the sleeves 8 and 8. , The outer rings 4 and 4 are urged in the axial direction away from each other.

In the preload spring 9 of the present embodiment, the axial preload load Fa is set within a range in which the following inequality (1) is established.

However, in the inequality (1), the meaning and unit of each variable are as follows.
Fa: Axial load (N)
μ: Rolling friction constant between ball and raceway surface d: Ball diameter (mm)
D: Ball PCD (Pitch Circle Diameter) (mm)
Z: Number of balls θ: Bearing contact angle (degrees)
n: Bearing rotation speed (min ^-1 )
In the above inequality (1), the lower limit value of the axial load Fa is not described, as long as the constant pressure preload Fa in the axial direction is applied to the outer ring 4, that Fa is a predetermined value greater than 0 (Fa> 0). This is because it is self-evident.

The right side of the inequality (1) is a dynamic formula for calculating the minimum axial load necessary for fixing the rotation axis of the balls 5 of the angular ball bearings 2a and 2b in a fixed direction.
Therefore, in the present embodiment, the elastic constant and natural length of the preload spring 9 are set so that the preload load Fa in the axial direction is smaller than the minimum value of the axial load that can be calculated by the dynamic formula of the right side of the formula (1). By setting the compression amount and the like, the preload load in the axial direction on the angular ball bearings 2a and 2b is set to such an extent that the rotation shafts of the four balls are not fixed in a fixed direction.

  Therefore, in the bearing device 1 of the present embodiment, the pair of sleeves 8 and 8 interposed between the outer rings, and the constant pressure preload in the axial direction is applied to the outer rings 4 and 4 via the sleeves 8 and 8, respectively. The preload spring 8 to be applied constitutes a preload application member that applies a constant pressure preload in the axial direction to the angular ball bearings 2a and 2b to such an extent that the rotation axis of each ball 4 is not fixed in a certain direction.

According to the turbocharger bearing device 1 having the above-described configuration, the axial preload Fa satisfying the inequality (1), that is, the rotation speed of the ball 5 is relatively lighter than that of the conventional art. Preload force Fa is applied to each ball bearing 2a, 2b.
For this reason, the direction of the rotation axis of the ball 5 of each ball bearing 2a, 2b varies with time due to the gyro force generated during high-speed rotation, and as a result, the rolling surface of the ball 5 in contact with the tracks 3a, 4a is fixed. Therefore, it is possible to prevent the occurrence of band-shaped wear marks on each ball 5 and to prevent or suppress the occurrence of abnormal noise.

Further, according to the bearing device 1 of the present embodiment, since the preload load in the axial direction is applied by the preload spring 9 interposed between the sleeves 8 and 8, the gap s between the sleeves 8 and 8 is relatively increased. It is possible to manage with a large size range (for example, on the order of several tens of μm).
For this reason, compared with the case where the fixed position preload is applied by the sleeves 8 and 8, for example, the assembly accuracy may be rough, the assembly is simple, and the vibration in the axial direction can be absorbed by the preload spring 9. A bearing device 1 suitable for rotation can be obtained.

In addition, this invention is not limited to the said embodiment.
In the above embodiment, the pair of sleeves 8 face each other with an axial gap s, but the ends of the sleeves 8 and 8 do not have to face each other directly. For example, FIG. As shown in FIG. 5, a protrusion 36a1 protruding radially inward is formed on the inner surface side of the bearing support 36a, and the protrusion 36a1 and the sleeves 8 and 8 have an axial gap s (about several tens of μm). And may be opposed.

Further, in the above embodiment, the inner rings 3, 3 of the ball bearings 2a, 2b are separated in the axial direction, and the inner ring spacer 7 is interposed therebetween. However, the inner rings 3, 3 and the inner rings An inner ring cylinder having the spacer 7 integrally may be employed.
Furthermore, as a type of the cage 6, not only a hollow type as shown in FIG. 1 but also a wave type, for example, can be adopted.

It is sectional drawing which shows one Embodiment of the bearing apparatus for turbochargers. It is sectional drawing which shows schematic structure of the turbocharger which has the said bearing apparatus. It is sectional drawing which shows the modification of the bearing apparatus for turbochargers.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bearing device for turbochargers 2 Angular contact ball bearing 2a 1st ball bearing 2b 2nd ball bearing 3 Inner ring 4 Outer ring 5 Ball 6 Cage 7 Inner ring spacer 8 Sleeve (preloading member)
9 Preload spring (preload member)
32 Rotating shaft 33 Turbine 34 Impeller 36 Housing 36a Bearing support portion T Turbocharger

Claims (1)

A turbocharger bearing device for rotatably supporting a rotating shaft of a turbocharger in a housing,
An inner ring provided on the rotating shaft side having a pair of inner ring raceways separated in the axial direction of the rotating shaft;
A pair of outer rings provided on the housing side having an outer ring raceway facing the inner ring raceway;
A pair of angular contact ball bearings in which a plurality of balls are arranged to freely roll between the inner ring raceway and the outer ring raceway;
A preload applying member that applies a constant pressure preload in the axial direction to each angular ball bearing to such an extent that the rotation axis of each ball is not fixed in a certain direction ;
The preload applying member is interposed between the pair of sleeves so as to apply a constant pressure preload in the axial direction to the outer rings via the pair of sleeves interposed between the pair of outer rings. A preload spring,
A turbocharger bearing device, wherein a preload in the axial direction by the preload spring is set within a range in which the following inequality (1) is satisfied .

Where, Fa: Preload (N), μ: Rolling friction constant between ball and raceway surface, d: Ball diameter (mm), D: Ball PCD (mm), Z: Number of balls, θ: Bearing contact angle ( Degrees), n: bearing rotation speed (min ^-1 ).

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