# Patent

## Title
Turbocharger having a bearing housing

## Abstract

There is provided a turbocharger which can reduce whirl vibration. The turbocharger includes a shaft connecting a turbine and a compressor, a bearing housing having a bearing portion turnably supporting the shaft, and a sliding bearing interposed between the shaft and the bearing portion. The bearing portion is formed of an aluminum-based material, the shaft is formed of a steel material, and the sliding bearing is formed of a copper-based material.

## Background
TECHNICAL FIELD
The present disclosure relates to a technique of a turbocharger provided in an internal combustion engine.
BACKGROUND ART
Conventionally, there has been publicly known a technique of a turbocharger provided in an internal combustion engine. Such a technique of a turbocharger is disclosed, for example, in Japanese Patent Application Laid-Open No. H9-310620.
The turbocharger rotatably supports a shaft, by a bearing housing, connecting a turbine driven by exhaust gas and a compressor for compressing intake air. Further, the turbocharger includes a sliding bearing interposed between the bearing housing and the shaft, and is configured such that the shaft is rotated smoothly.
However, in the case where the sliding bearing is used in a portion rotating at high speed like the shaft of the turbocharger, since clearances between the bearing housing and the sliding bearing and between the sliding bearing and the shaft are narrow, whirl vibration may occur in the portion. Further, in the case where the whirl vibration occurs, noise (abnormal sound) caused by the whirl vibration may occur.
SUMMARY
The present disclosure has been devised to solve the disadvantageous point described above, and an object thereof is to provide a turbocharger which can reduce whirl vibration.
The technical problem of the present disclosure is described above, and the solution to problem will be described hereafter.
A turbocharger according to the present disclosure includes a shaft connecting a turbine and a compressor, a bearing housing having a bearing portion turnably supporting the shaft, and a sliding bearing interposed between the shaft and the bearing portion. The bearing portion is formed of an aluminum-based material, the shaft is formed of a steel material, and the sliding bearing is formed of a copper-based material.
In the turbocharger according to the present disclosure, the bearing housing is divided into a turbine-side housing disposed at a turbine side and a compressor-side housing disposed at a compressor side. The turbine-side housing is formed of stainless steel, the bearing portion is formed in the compressor-side housing.
In the turbocharger according to the present disclosure, a metal gasket is interposed between the turbine-side housing and the compressor-side housing.
The advantageous effects of the disclosure will be described hereafter.
In the turbocharger according to the present disclosure, in the case where the temperature of the bearing portion rises, the inner diameter of the bearing portion formed of an aluminum-based material is expanded larger than the outer diameter of the sliding bearing formed of a copper-based material. Accordingly, the amount of the lubricating oil interposed between the bearing portion and the sliding bearing is increased so that whirl vibration can be reduced. Similarly, in the case where the temperature of the bearing portion rises, the inner diameter of the sliding bearing formed of a copper-based material is expanded larger than the outer diameter of the shaft formed of a steel material. Accordingly, the amount of the lubricating oil interposed between the sliding bearing and the shaft is increased so that whirl vibration can be reduced. Further, the inner diameter of the bearing portion formed of an aluminum-based material has a high thermal conductivity so that heat generated in the bearing portion is absorbed and conducted effectively, and by lowering the temperature of the bearing portion, deformation, damage, and the like due to the heat can be prevented effectively.
In the turbocharger according to the present disclosure, since the turbine-side housing to be at a relatively high temperature is formed of stainless steel, it is possible to prevent deformation, damage, and the like due to a high temperature. Further, since the turbine-side housing formed of stainless steel shields heat, it is possible to prevent deformation, damage, and the like, which are caused by heat, of the bearing portion formed of an aluminum-based material.
In the turbocharger according to the present disclosure, the metal gasket is interposed between the turbine-side housing and the compressor-side housing so that it is possible to shield heat from the turbine side, and to more effectively prevent deformation, damage, and the like, which are caused by heat, of the bearing portion formed of an aluminum-based material.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram showing an overview of operation for a turbocharger according to one embodiment of the present invention.
FIG. 2 is a sectional side view showing a configuration of the turbocharger according to one embodiment of the present invention.
FIG. 3 is a perspective view of the bearing housing.
FIG. 4 is a perspective view of a compressor-side housing.
FIG. 5A is a front view of the compressor-side housing.
FIG. 5B is a bottom view of the compressor-side housing.
FIG. 6 is a back view of the compressor-side housing.
FIG. 7A is a left-side view of the compressor-side housing.
FIG. 7B is a cross-sectional view of the compressor-side housing taken along line A-A of FIG. 5A.
FIG. 8A is a cross-sectional view of the compressor-side housing taken along line B-B of FIG. 5A.
FIG. 8B is a cross-sectional view of the compressor-side housing taken along line C-C of FIG. 5A.
FIG. 9 is a perspective view of a turbine-side housing.
FIG. 10A is a front view of the turbine-side housing.
FIG. 10B is a right-side view of the turbine-side housing.
FIG. 11 is a back view of the turbine-side housing.
FIG. 12A is a cross-sectional view of the turbine-side housing taken along line D-D of FIG. 10A.
FIG. 12B is a cross-sectional view of the turbine-side housing taken along line E-E of FIG. 10A.
FIG. 13A is a front view of the bearing housing.
FIG. 13B is a bottom view of the bearing housing.
FIG. 14 is a left-side view of the bearing housing.
FIG. 15 is a cross-sectional view of the bearing housing taken along line F-F of FIG. 13A.
FIG. 16 is a cross-sectional view of the bearing housing taken along line G-G of FIG. 13A.
FIG. 17A is a back view of a turbine-side housing according to another embodiment of the present invention.
FIG. 17B is a cross-sectional view of the turbine-side housing taken along line H-H of FIG. 17A.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the following description, in accordance with arrows shown in the figures, a front-back direction, an up-down direction, and a left-right direction are defined individually.
With reference to FIG. 1, description will be given of an overview of operation for a turbocharger 10 according to one embodiment of the present invention.
The turbocharger 10 is for feeding compressed air into a cylinder 2 of an engine. The air is supplied to the cylinder 2 via an intake passage 1. The air sequentially passes through an air cleaner 4, the turbocharger 10, an intercooler 5, and a throttle valve 6 which are disposed along the intake passage 1, and then the air is supplied to the cylinder 2. At this time, since a compressor 30 of the turbocharger 10 compresses the air, much more air can be fed into the cylinder 2.
High-temperature air (exhaust) after burning inside the cylinder 2 is discharged via an exhaust passage 3. At this time, the exhaust rotates a turbine 40 of the turbocharger 10, the rotation is transmitted to the compressor 30, and thereby the air inside the intake passage 1 can be compressed.
On the upstream side of the turbine 40, the exhaust passage 3 is branched, and a passage not via the turbine 40 is formed separately. The passage can be opened/closed by a waste gate valve 7. The waste gate valve 7 is driven to open/close by an actuator 8. Further, operation of the actuator 8 is controlled by a negative pressure generating mechanism 9 which is configured by a solenoid valve and the like. The waste gate valve 7 is opened/closed by the actuator 8 so that flow rates of exhaust to be fed to the turbine 40 can be adjusted.
Next, with reference to FIG. 2, description will be given of an overview of a configuration of the turbocharger 10.
The turbocharger 10 mainly includes a shaft 20, the compressor 30, the turbine 40, the bearing housing 100, a compressor housing 60, a turbine housing 70, a sliding bearing 80, a color turbo seal 81, a thrust bearing 82, and a retainer seal 83.
The shaft 20 is disposed such that the longitudinal direction thereof is directed toward the front-back direction. The compressor 30 is fixed to one end (back end) of the shaft 20, and the turbine 40 is fixed to the other end (front end) of the shaft 20. Thus, the shaft 20 connects the compressor 30 and the turbine 40. The shaft 20 is formed of a steel material.
The bearing housing 100 contains the shaft 20, and turnably supports the shaft 20. The shaft 20 is disposed so as to penetrate through the bearing housing 100 in the front-back direction. The compressor 30 is disposed at the back of the bearing housing 100, and the turbine 40 is disposed at the front of the bearing housing 100.
The compressor housing 60 is for containing the compressor 30. The compressor housing 60 is fixed to a back portion of the bearing housing 100, and is formed to cover the compressor 30.
The turbine housing 70 is for containing the turbine 40. The turbine housing 70 is fixed to a front portion of the bearing housing 100, and is formed to cover the turbine 40.
The sliding bearing 80 is interposed between the shaft 20 and the bearing housing 100, and is for turning the shaft 20 smoothly. The sliding bearing 80 is formed of a copper-based material.
The color turbo seal 81 is a member through which the shaft 20 is inserted at the back of the sliding bearing 80. The thrust bearing 82 is externally fitted onto the color turbo seal 81 at the back of the sliding bearing 80, and the retainer seal 83 is externally fitted onto the color turbo seal 81 at the back of the thrust bearing 82.
Next, with reference to FIGS. 2 to 16, description will be given of a configuration of the bearing housing 100.
The bearing housing 100 mainly includes a compressor-side housing 110, a turbine-side housing 120, and a metal gasket 150. The compressor-side housing 110 and the turbine-side housing 120 are disposed side by side and fixed in the front-back direction, thereby configuring the bearing housing 100.
The compressor-side housing 110 shown in FIGS. 2 to 8 is a member which configures a portion of a compressor 30 side in the bearing housing 100. The compressor-side housing 110 mainly includes a body portion 111 and a flange portion 112.
The body portion 111 is a portion formed into a roughly cylindrical shape such that the axis thereof is directed toward the front-back direction. At a lower portion of the body portion 111, a lower surface (bottom surface) that is a plane surface parallel to the front-back and the left-right directions is formed. In the body portion 111, an O-ring groove 111a, a bearing portion 111b, and a heat sink portion 111c are formed.
The O-ring groove 111a is formed at a roughly central portion of a back surface of the body portion 111, and is a recess having a predetermined depth. A cross-section (back view) of the O-ring groove 111a is formed to be a roughly circular shape.
The bearing portion 111b is a portion for turnably supporting the shaft 20. The bearing portion 111b includes a through-hole which is formed so as to penetrate through the body portion 111 in the front-back direction. More specifically, the bearing portion 111b is formed so as to communicate a front surface of the body portion 111 with a thrust bearing oil passage 143a to be described later, and additionally formed to be parallel to the front-back direction.
The heat sink portion 111c is a portion for dissipating heat transferred to the compressor-side housing 110. The heat sink portion 111c is formed on an outer peripheral surface of the body portion 111 (more specifically, front and back surfaces of the body portion 111 and a surface except a plane surface formed at the lower portion of the body portion 111). The heat sink portion 111c is formed to arrange a plurality of plate-shaped (fin-shaped) portions on the outer peripheral surface of the body portion 111.
The flange portion 112 is a portion formed into a roughly disc shape such that the plate surface thereof is directed toward the front-back direction. The flange portion 112 is integrally formed with the body portion 111 on the back end periphery of the body portion 111.
The compressor-side housing 110 configured as described above is formed of an aluminum die cast (die cast using an aluminum-based material).
The turbine-side housing 120 shown in FIGS. 2, 3, and 9 to 12 is a member which configures a portion of a turbine 40 side in the bearing housing 100. The turbine-side housing 120 mainly includes a flange portion 121, and a thick wall portion 122.
The flange portion 121 is a portion formed into a roughly disc shape such that the plate surface thereof is directed toward the front-back direction.
The thick wall portion 122 is a portion formed such that the plate thickness of a central portion of the flange portion 121 formed in a roughly disc shape is thicker than the plate thickness of other portions. More specifically, the thick wall portion 122 is formed into a roughly cylindrical shape such that the axis thereof is directed toward the front-back direction. The thick wall portion 122 is formed so as to protrude from a front surface of the flange portion 121 in the front direction. The thick wall portion 122 is integrally formed with the flange portion 121. The thick wall portion 122 is formed with a through-hole 122a. 
The through-hole 122a is formed so as to penetrate through the thick wall portion 122 of the turbine-side housing 120 in the front-back direction.
The turbine-side housing 120 configured as described above is formed by a sheet metal process using stainless steel.
In the compressor-side housing 110 and the turbine-side housing 120 configured as described above, as shown in FIGS. 2, 3, and 13 to 16, in a state where a front surface of the compressor-side housing 110 and a back surface of the turbine-side housing 120 abut on each other, by fastening (fixing) a fastening tool such as a bolt, a diffusion bonding or the like, the bearing housing 100 is formed.
Under the circumstance, the metal gasket 150 that is a gasket made of metal is interposed between the compressor-side housing 110 and the turbine-side housing 120, thereby retaining a liquid tightness between the compressor-side housing 110 and the turbine-side housing 120.
Further, the sliding bearing 80 is inserted into the inside of the bearing portion 111b formed in the compressor-side housing 110 of the bearing housing 100, and further the shaft 20 is inserted into the inside of the sliding bearing 80. Thus, the sliding bearing 80 is interposed between the shaft 20 and the bearing housing 100 (more specifically, the bearing portion 111b).
In the turbocharger 10 having the bearing housing 100 configured as described above, when the turbine 40 is rotated by exhaust of an engine, the temperature of the bearing housing 100 also becomes high due to the high-temperature exhaust. At this time, the temperature of a portion near the turbine 40 rotated by the exhaust, namely the turbine-side housing 120 in the bearing housing 100 particularly becomes high. Since the turbine-side housing 120 according to the present embodiment is formed of stainless steel, the turbine-side housing 120 is resistant to heat and is capable of resisting the high temperature caused by the exhaust of the engine.
A portion near the turbine 40 in the bearing housing 100 is configured with the turbine-side housing 120 formed of stainless steel so that it is possible to insulate (shield) exhaust heat in the turbine-side housing 120 and to prevent heat from easily transferring to the compressor-side housing 110. Further, according to the present embodiment, the metal gasket 150 is interposed between the compressor-side housing 110 and the turbine-side housing 120, and thereby the metal gasket 150 is capable of shielding heat. Thus, it is more possible to prevent heat from easily transferring to the compressor-side housing 110.
Further, since a portion far from the turbine 40 in the bearing housing 100, namely the compressor-side housing 110 has a heat shielding effect from the turbine-side housing 120, the compressor-side housing 110 does not easily become a high temperature, compared to the turbine-side housing 120. Accordingly, as the present embodiment, the compressor-side housing 110 can be formed of an aluminum-based material which is comparatively weak to heat compared to stainless steel. Thereby, it is possible to reduce the weight of the bearing housing 100 and to improve workability thereof.
Further, in the compressor-side housing 110, since the heat sink portion 111c for easily dissipating heat is formed therein, it is possible to effectively suppress a temperature rise in the compressor-side housing 110 (specifically, the bearing housing 100).
Generally, in a portion for rotating at high speed using a sliding bearing (in the present embodiment, in the bearing portion 111b of the compressor-side housing 110, a portion in which the shaft 20 is turnably supported via the sliding bearing 80), whirl vibration may occur. When the whirl vibration occurs, noise (abnormal sound) may occur due to the whirl vibration. Accordingly, it is important to reduce the whirl vibration.
In the present embodiment, by rotating the shaft 20 at high speed and transferring exhaust heat from the turbine 40 side, the temperature of the bearing portion 111b (more specifically, the bearing portion 111b, the sliding bearing 80 and the shaft 20 supported in the bearing portion 111b) rises. Thereby, each of the bearing portion 111b, the sliding bearing 80, and the shaft 20 expands (expands thermally).
A coefficient of thermal expansion of the sliding bearing 80 (copper-based material) is larger than that of the shaft 20 (steel material). A coefficient of thermal expansion of the bearing portion 111b (aluminum-based material) is larger than that of the sliding bearing 80 (copper-based material). Accordingly, an inner diameter of the sliding bearing 80 is expanded larger than an outer diameter of the shaft 20, and an inner diameter of the bearing portion 111b is expanded larger than an outer diameter of the sliding bearing 80. Thus, the amount of the lubricating oil interposed between the sliding bearing 80 and the shaft 20, and the amount of the lubricating oil interposed between the bearing portion 111b and the sliding bearing 80 are both increased. Thereby, it is possible to reduce the whirl vibration.
According to the present embodiment, by forming the bearing portion 111b with an aluminum-based material having a high thermal conductivity, heat generated in the bearing portion 111b is effectively absorbed and conducted (for example, dissipated from the heat sink portion 111c), and thereby a temperature rise of the bearing portion 111b can be suppressed. Thus, it is possible to effectively prevent deformation, damage, and the like, which are caused by heat, of the bearing portion 111b. 
A lubricating oil passage 140 for supplying lubricating oil to the bearing portion 111b will be described later.
Next, with reference to FIGS. 2 to 8, and 11 to 16, description will be given of a cooling water passage 130 and the lubricating oil passage 140 which are formed in the bearing housing 100.
The cooling water passage 130 is for supplying cooling water for cooling the bearing housing 100 to the inside of the bearing housing 100. The cooling water passage 130 mainly includes a compressor-side arc-shaped cooling water passage 131, a turbine-side arc-shaped cooling water passage 132, a water supply passage 133, and a water discharge passage 134.
The compressor-side arc-shaped cooling water passage 131 shown in FIGS. 4 to 8 is a groove formed on a front surface of the body portion 111 in the compressor-side housing 110. The compressor-side arc-shaped cooling water passage 131 is formed, in a front view (refer to FIG. 5), so as to have a shape (arc shape) such that a bottom portion of a circular shape centered around the bearing portion 111b is cut out. The front surface of the body portion 111 in the compressor-side housing 110 is subjected to machining such as cutting and grinding to thereby form the compressor-side arc-shaped cooling water passage 131.
The turbine-side arc-shaped cooling water passage 132 shown in FIG. 11 and FIG. 12 is a groove formed on a back surface of the thick wall portion in the turbine-side housing 120. The turbine-side arc-shaped cooling water passage 132 is formed, in a back view (refer to FIG. 11), so as to have a shape (arc shape) such that a bottom portion of a circular shape centered around the through-hole 122a is cut out. The turbine-side arc-shaped cooling water passage 132 is formed so as to correspond to the compressor-side arc-shaped cooling water passage 131 formed in the compressor-side housing 110 (refer to FIG. 5). The back surface of the thick wall portion 122 in the turbine-side housing 120 is subjected to machining such as cutting and grinding, or press working to thereby form the turbine-side arc-shaped cooling water passage 132.
The water supply passage 133 shown in FIG. 5 and FIG. 8 is formed in the compressor-side housing 110, and is for communicating the compressor-side arc-shaped cooling water passage 131 with a bottom surface of the body portion 111 in the compressor-side housing 110. More specifically, the water supply passage 133 is formed so as to communicate a neighborhood of a right end portion of the bottom surface of the body portion 111 in the compressor-side housing 110 with a right end portion of the compressor-side arc-shaped cooling water passage 131. The front surface of the body portion 111 in the compressor-side housing 110 (more specifically, inside of the compressor-side arc-shaped cooling water passage 131) and the bottom surface of the body portion 111 in the compressor-side housing 110 are subjected to machining such as cutting and grinding to thereby form the water supply passage 133.
The water discharge passage 134 shown in FIG. 5 is formed in the compressor-side housing 110, and is for communicating the compressor-side arc-shaped cooling water passage 131 with the bottom surface of the body portion 111 in the compressor-side housing 110. More specifically, the water discharge passage 134 is formed so as to communicate a neighborhood of a left end portion of the bottom surface of the body portion 111 in the compressor-side housing 110 with a left end portion of the compressor-side arc-shaped cooling water passage 131. The front surface of the body portion 111 in the compressor-side housing 110 (more specifically, inside of the compressor-side arc-shaped cooling water passage 131) and the bottom surface of the body portion 111 in the compressor-side housing 110 are subjected to machining such as cutting and grinding to thereby form the water discharge passage 134.
As shown in FIGS. 3, and 13 to 16, by fastening (fixing) the compressor-side housing 110 with the turbine-side housing 120, the water supply passage 133, the compressor-side arc-shaped cooling water passage 131, the turbine-side arc-shaped cooling water passage 132, and the water discharge passage 134 are communicatively connected with each other. Thereby, the cooling water passage 130 is formed.
In the cooling water passage 130 formed as described above, cooling water is supplied to the inside of the bearing housing 100 via the water supply passage 133. The cooling water is supplied from the water supply passage 133 to one end portion of the compressor-side arc-shaped cooling water passage 131 (right lower end portion in FIG. 5A), and to one end portion of the turbine-side arc-shaped cooling water passage 132 (right lower end portion in FIG. 11).
The cooling water circulates inside the compressor-side arc-shaped cooling water passage 131 and inside the turbine-side arc-shaped cooling water passage 132, and then the cooling water is supplied to the other end portion of the compressor-side arc-shaped cooling water passage 131 (left lower end portion in FIG. 5A) and to the other end portion of the turbine-side arc-shaped cooling water passage 132 (left lower end portion in FIG. 11). At this time, the compressor-side arc-shaped cooling water passage 131 and the turbine-side arc-shaped cooling water passage 132 are formed so as to be an arc shape centered at the bearing portion 111b and the through-hole 122a (specifically, the shaft 20). Accordingly, heat transferred from the turbine 40 side via the shaft 20 and heat generated by the rotation of the shaft 20 can be cooled effectively.
The cooling water is supplied from the other end portion of the compressor-side arc-shaped cooling water passage 131 and the other end portion of the turbine-side arc-shaped cooling water passage 132 to the water discharge passage 134. The cooling water is discharged from the water discharge passage 134 to the outside of the bearing housing 100.
As described above, by circulating cooling water inside the cooling water passage 130, a temperature rise of the bearing housing 100 can be suppressed effectively.
The lubricating oil passage 140 is for supplying lubricating oil for lubricating a sliding portion between the bearing housing 100 and the shaft 20 to the inside of the bearing housing 100. The lubricating oil passage 140 mainly includes the bearing portion 111b, a first lubricating oil passage 142, and a second lubricating oil passage 143.
The bearing portion 111b shown in FIGS. 4 to 8 is a through-hole which is formed so as to penetrate through the body portion 111 in the compressor-side housing 110 in the front-back direction as described above. The bearing portion 111b is a portion for turnably supporting the shaft 20, and is also a portion for forming a part of the lubricating oil passage 140. The compressor-side housing 110 (more specifically, inside of the thrust bearing oil passage 143a to be described later) is subjected to machining such as cutting and grinding from the front surface or the back surface thereof to thereby form the bearing portion 111b. 
The first lubricating oil passage 142 shown in FIGS. 4, 7, and 8 is for communicating an upper surface of the bearing housing 100 with the bearing portion 111b. More specifically, the first lubricating oil passage 142 is formed so as to communicate a roughly central portion of an upper surface (upper portion) of the body portion 111 in the compressor-side housing 110 with a roughly central portion in the front-back direction of the bearing portion 111b. The upper surface (upper portion) of the body portion 111 in the compressor-side housing 110 is subjected to machining such as cutting and grinding to thereby form the first lubricating oil passage 142.
In a middle portion of the first lubricating oil passage 142, a compressor-side branch oil passage 142a is formed so as to be branched therefrom. The compressor-side branch oil passage 142a communicates a middle portion in the vertical direction of the first lubricating oil passage 142 with a thrust bearing oil passage 143a to be described later. The thrust bearing oil passage 143a to be described later is subjected to machining such as cutting and grinding to thereby form the compressor-side branch oil passage 142a. 
The second lubricating oil passage 143 shown in FIGS. 4 to 7, 11, and 12 is for communicating a lower surface of the bearing housing 100 with the bearing portion 111b. The second lubricating oil passage 143 mainly includes a thrust bearing oil passage 143a, a compressor-side horizontal oil passage 143b, a turbine-side vertical oil passage 143c, and a discharge oil passage 143d. 
The thrust bearing oil passage 143a shown in FIG. 6 and FIG. 7 is a groove which is formed by cutting out, in the vertical direction, the inside of the O-ring groove 111a (back portion of the body portion 111) formed in the body portion 111 of the compressor-side housing 110. More specifically, the thrust bearing oil passage 143a is formed such that the body portion 111 is deeply cut out in the front direction from the roughly central portion of a back portion of the body portion 111 (back end portion of the bearing portion 111b (end portion at the compressor 30 side)) to the lower portion. The back surface of the compressor-side housing 110 (more specifically, inside of the O-ring groove 111a) is subjected to machining such as cutting and grinding to thereby form the thrust bearing oil passage 143a. 
The compressor-side horizontal oil passage 143b shown in FIGS. 4 to 7 is a through-hole which is formed so as to penetrate through the body portion 111 of the compressor-side housing 110 in the front-back direction. More specifically, the compressor-side horizontal oil passage 143b is formed so as to communicate the front surface of the body portion 111 with the thrust bearing oil passage 143a, and is further formed in the lower direction of the bearing portion 111b so as to be parallel to the bearing portion 111b. The compressor-side housing 110 (more specifically, inside of the thrust bearing oil passage 143a) is subjected to machining such as cutting and grinding, or casting using a casting mold from the front surface or the back surface thereof to thereby form the compressor-side horizontal oil passage 143b. 
The turbine-side vertical oil passage 143c shown in FIG. 11 and FIG. 12 is a groove which is formed by cutting out a back surface of the thick wall portion 122 of the turbine-side housing 120 in the vertical direction. More specifically, the turbine-side vertical oil passage 143c is formed from a roughly central portion of the back surface of the thick wall portion 122 (through-hole 122a) to a lower portion. The back surface of the turbine-side housing 120 is subjected to machining such as cutting and grinding, or press working to thereby form the turbine-side vertical oil passage 143c. 
The discharge oil passage 143d shown in FIG. 5 and FIG. 7 is formed in the compressor-side housing 110, and is for communicating the compressor-side horizontal oil passage 143b with the bottom surface of the body portion 111 of the compressor-side housing 110. More specifically, the discharge oil passage 143d is formed so as to communicate the right and left central portions of the bottom surface of the body portion 111 in the compressor-side housing 110 with a roughly central portion in the front-back direction of the compressor-side horizontal oil passage 143b. The bottom surface of the body portion 111 in the compressor-side housing 110 is subjected to machining such as cutting and grinding to thereby form the discharge oil passage 143d. 
As shown in FIGS. 3, 13 to 16, when the compressor-side housing 110 and the turbine-side housing 120 are fastened (fixed), the thrust bearing oil passage 143a, the compressor-side horizontal oil passage 143b, the turbine-side vertical oil passage 143c, and the discharge oil passage 143d are communicatively connected to each other. Thus, the second lubricating oil passage 143 is formed. Further, the first lubricating oil passage 142, the bearing portion 111b, and the second lubricating oil passage 143 form the lubricating oil passage 140.
In the lubricating oil passage 140 according to the present embodiment, a process for reducing a surface roughness of the lubricating oil passage 140 (for example, precision grinding, coating, and the like) is performed.
In the lubricating oil passage 140 formed as described above, lubricating oil is supplied from an upper surface of the bearing housing 100 (compressor-side housing 110) via the first lubricating oil passage 142 to the inside of the bearing housing 100. The lubricating oil circulates inside the first lubricating oil passage 142 in the lower direction, and then the lubricating oil is supplied to the bearing portion 111b. Further, part of the lubricating oil which circulates inside the first lubricating oil passage 142 is supplied to the thrust bearing oil passage 143a of the compressor-side housing 110 via the compressor-side branch oil passage 142a. 
The lubricating oil supplied to the bearing portion 111b circulates between the bearing portion 111b and the sliding bearing 80, and damps a vibration of the sliding bearing 80. Further, the lubricating oil circulates from a through-hole appropriately formed on an outer peripheral surface of the sliding bearing 80 to the inside of the sliding bearing 80. The lubricating oil circulates between the sliding bearing 80 and the shaft 20, lubricates a relative rotation of the sliding bearing 80 and the shaft 20, and cools the bearing portion.
The lubricating oil having lubricated the bearing portion 111b, the sliding bearing 80, and the shaft 20 circulates to a front end portion of the bearing portion 111b (end portion at the turbine 40 side) or a back end portion of the bearing portion 111b (end portion at the compressor 30 side), and then the lubricating oil is supplied to the compressor-side horizontal oil passage 143b via either the thrust bearing oil passage 143a or the turbine-side vertical oil passage 143c. The lubricating oil supplied to the compressor-side horizontal oil passage 143b is discharged from the bottom surface of the body portion 111 in the compressor-side housing 110 via the discharge oil passage 143d to the outside of the bearing housing 100.
Thus, the lubricating oil is circulated from the upper surface of the bearing housing 100 via the bearing portion 111b to a lower surface of the bearing housing 100 (bottom surface of the body portion 111) so that the lubricating oil can be smoothly circulated in accordance with gravity. Further, the lubricating oil is discharged from the front end and the back end of the bearing portion 111b so that the lubricating oil can be smoothly circulated and can be surely guided from the front end to the back end of the bearing portion 111b. 
As described above, the bearing housing 100 of the turbocharger 10 according to the present embodiment contains the shaft 20 connecting the turbine 40 and the compressor 30, and turnably supports the shaft 20. The bearing housing 100 of the turbocharger 10 is divided into the turbine-side housing 120 disposed at the turbine 40 side and the compressor-side housing 110 disposed at the compressor 30 side. The turbine-side housing 120 and the compressor-side housing 110 are subjected to machining to thereby form the cooling water passage 130 for supplying cooling water and the lubricating oil passage 140 for supplying lubricating oil.
With this configuration, since the cooling water passage 130 and the lubricating oil passage 140 formed in the bearing housing 100 are formed by performing machining, there is no necessity to use a core when the bearing housing 100 is manufactured by casting. Thus, it is possible to achieve cost reduction. Further, since there is no necessity to form the cooling water passage 130 and the lubricating oil passage 140 by using a sand core at the casting stage, inspecting whether foundry sand is remaining inside the cooling water passage 130 and inside the lubricating oil passage 140 is not needed. Further, by dividing the bearing housing 100 into two members, it is possible to improve workability (easily perform machining) of the cooling water passage 130 and the lubricating oil passage 140.
The lubricating oil passage 140 through which the shaft 20 is inserted, includes the bearing portion 111b that is a through-hole for turnably supporting the shaft 20, the first lubricating oil passage 142 which communicates the upper surface of the bearing housing 100 with the bearing portion 111b, and the second lubricating oil passage 143 which communicates the lower surface of the bearing housing 100 with the bearing portion 111b. 
With this configuration, it is possible to simplify a shape of the lubricating oil passage 140, and further to improve workability of the lubricating oil passage 140. Further, by supplying the lubricating oil to the inside of the bearing housing 100 via the first lubricating oil passage 142, the lubricating oil sequentially circulates through the first lubricating oil passage 142, the bearing portion 111b, and the second lubricating oil passage 143 in accordance with gravity. Thus, it is possible to circulate the lubricating oil smoothly.
The second lubricating oil passage 143 is formed so as to communicate each of an end portion of the bearing portion 111b at the compressor 30 side and an end portion of the bearing portion 111b at the turbine 40 side with the lower surface of the bearing housing 100.
With this configuration, the lubricating oil can be discharged from both the end portions of the bearing portion 111b in the lower direction of the bearing housing 100, and thereby the lubricating oil can be circulated smoothly. Further, the lubricating oil can be surely guided to both the ends of the bearing portion 111b, and thereby the bearing portion 111b can be lubricated and cooled effectively.
On at least one of a surface, which is in contact with the compressor-side housing 110, of the turbine-side housing 120 and a surface, which is in contact with the turbine-side housing 120, of the compressor-side housing 110, as the cooling water passage 130, an arc-shaped cooling water passage in an arc shape centered at the shaft 20 (the compressor-side arc-shaped cooling water passage 131 and the turbine-side arc-shaped cooling water passage 132) is formed.
With this configuration, by forming the cooling water passage so as to surround a periphery of the shaft 20, it is possible to effectively suppress a temperature rise of the bearing housing 100 caused by heat transferred from the turbine 40 side via the shaft 20 or heat generated by the rotation of the shaft 20.
A process for reducing the surface roughness is performed on the lubricating oil passage 140.
With this configuration, flow resistance of the lubricating oil passage 140 can be reduced, and thus machine efficiency of the turbocharger 10 can be improved. Further, since lubricating oil does not easily stay in the lubricating oil passage 140, occurrence of oil caulking can be reduced.
The bearing housing 100 of the turbocharger 10 according to the present embodiment contains the shaft 20 connecting the turbine 40 and the compressor 30, and turnably supports the shaft 20. The bearing housing 100 of the turbocharger 10 is divided into the turbine-side housing 120 disposed at the turbine 40 side and the compressor-side housing 110 disposed at the compressor 30 side. The compressor-side housing 110 is formed of an aluminum-based material.
With this configuration, since the compressor-side housing 110 to be at a relatively low temperature is formed of an aluminum-based material, the weight of the bearing housing 100 can be reduced.
On an outer peripheral surface of the compressor-side housing 110, a heat sink portion 111c for dissipating heat transferred to the compressor-side housing 110 is formed.
With this configuration, it is possible to suppress a temperature rise of the bearing housing 100 disposed under a high-temperature environment (specifically, heat from engine exhaust or heat generated by rotation of the shaft 20 are transferred).
The turbine-side housing 120 is formed of stainless steel.
Thus, since the turbine-side housing 120 to be at a relatively high temperature is formed of stainless steel, it is possible to prevent deformation, damage, and the like due to a high temperature. Further, since the turbine-side housing 120 formed of stainless steel shields heat, it is possible to prevent deformation, damage, and the like, which are caused by heat, of the compressor-side housing 110 formed of an aluminum-based material. Further, since stainless steel has a low surface roughness compared to the cast iron, lubricating oil does not easily stay in the turbine-side housing 120. Thus, it is possible to reduce the occurrence of oil caulking.
The turbocharger 10 according to the present embodiment includes the shaft 20 connecting the turbine 40 and the compressor 30, the bearing housing 100 having the bearing portion 111b which turnably supports the shaft 20, and the sliding bearing 80 interposed between the shaft 20 and the bearing portion 111b. The bearing portion 111b is formed of an aluminum-based material, the shaft 20 is formed of a steel material, and the sliding bearing 80 is formed of a copper-based material.
With this configuration, in the case where the temperature of the bearing portion 111b rises, the inner diameter of the bearing portion 111b formed of an aluminum-based material is expanded larger than the outer diameter of the sliding bearing 80 formed of a copper-based material. Accordingly, the amount of the lubricating oil interposed between the bearing portion 111b and the sliding bearing 80 is increased, and thereby it is possible to reduce the whirl vibration. Similarly, in the case where the temperature of the bearing portion 111b rises, the inner diameter of the sliding bearing 80 formed of a copper-based material is expanded larger than the outer diameter of the shaft 20 formed of a steel material. Accordingly, the amount of the lubricating oil interposed between the sliding bearing 80 and the shaft 20 is increased, and thereby it is possible to reduce the whirl vibration. Further, since the inner diameter of the bearing portion 111b formed of an aluminum-based material has a high thermal conductivity, heat generated in the bearing portion 111b is effectively absorbed and conducted. The temperature of the bearing portion 111b is lowered so that deformation, damage, and the like due to the heat can be prevented effectively.
The bearing housing 100 is divided into the turbine-side housing 120 disposed at the turbine 40 side and the compressor-side housing 110 disposed at the compressor 30 side. The turbine-side housing 120 is formed of stainless steel, and the bearing portion 111b is formed in the compressor-side housing 110.
Thus, since the turbine-side housing 120 to be at a relatively high temperature is formed of stainless steel, it is possible to prevent deformation, damage, and the like due to a high temperature. Further, since the turbine-side housing 120 formed of stainless steel shields heat, it is possible to prevent deformation, damage, and the like, which are caused by heat, of the bearing portion 111b formed of an aluminum-based material.
The metal gasket 150 is interposed between the turbine-side housing 120 and the compressor-side housing 110.
Thus, the metal gasket 150 is interposed between the turbine-side housing 120 and the compressor-side housing 110 so that it is possible to shield heat from the turbine 40 side, and to more effectively prevent deformation, damage, and the like, which are caused by heat, of the bearing portion 111b formed of an aluminum-based material.
In the present embodiment, the heat sink portion 111c formed in the body portion 111 of the compressor-side housing 110 is formed to have a plurality of plate-shaped (fin-shaped) portions. However, the present invention is not limited to this embodiment. Specifically, the heat sink portion 111c may be of a shape for increasing a surface area of the body portion 111, for example, the heat sink portion 111c can be formed into a lobe shape, a spiral shape, a pinholder shape, a bellows shape, and the like.
Further, in the present embodiment, the turbine-side housing 120 is formed by a sheet metal process using stainless steel. However, the present invention is not limited to this embodiment, and for example, the turbine-side housing 120 can be formed by casting using cast iron.
Further, in the present embodiment, a process is performed so as to reduce the surface roughness to the lubricating oil passage 140. However, the present invention is not limited to this embodiment, and it is possible to perform a process for reducing the surface roughness to the cooling water passage 130. Thereby, it is possible to reduce flow resistance of cooling water which circulates inside the cooling water passage 130.
As other embodiment, as shown in FIG. 17, it is also possible to form a recess 121a in the turbine-side housing 120.
The back surface of the turbine-side housing 120 is subjected to machining such as cutting and grinding, or press working to thereby form the recess 121a. The recess 121a is formed on the back surface of the turbine-side housing 120 over a wide range as much as possible.
The back surface of the turbine-side housing 120 as configured above and the front surface of the compressor-side housing 110 (refer to FIGS. 4 to 8) are fixed to each other in an abutting manner, so that the recess 121a is formed on the back surface of the turbine-side housing 120, thereby reducing a contact area between the turbine-side housing 120 and the compressor-side housing 110. Thus, in the case where the temperature of the turbine-side housing 120 becomes high, the heat is prevented from transferring to the compressor-side housing 110, and thus it is possible to prevent deformation, damage, and the like, which are due to a high temperature, of the compressor-side housing 110. Further, since space in which air exists inside the recess 121a is formed, it is possible to prevent heat from easily transferring to the compressor-side housing 110 by the space (layer of air).
As described above, in the bearing housing 100 of the turbocharger 10 according to the present embodiment, the recess 121a is formed on the surface (back surface), which is in contact with the compressor-side housing 110, of the turbine-side housing 120.
With this configuration, it is possible to prevent heat of the turbine-side housing 120 from easily transferring to the compressor-side housing 110.
In the present embodiment, the recess 121a is formed in the turbine-side housing 120, however, the present invention is not limited to this embodiment. Specifically, there may be a configuration in which a recess is formed on the surface (front surface), which is in contact with the turbine-side housing 120, of the compressor-side housing 110, or a configuration in which a recess is formed on both surface of the back surface of the turbine-side housing 120 and the front surface of the compressor-side housing 110.
INDUSTRIAL APPLICABILITY
The present invention can be applied to a turbocharger provided in an internal combustion engine.
REFERENCE SIGNS LIST


    
    
        20 shaft
        30 compressor
        40 turbine
        80 sliding bearing
        100 bearing housing
        110 compressor-side housing
        111b bearing portion
        111c heat sink portion
        120 turbine-side housing
        130 cooling water passage
        131 compressor-side arc-shaped cooling water passage
        132 turbine-side arc-shaped cooling water passage
        140 lubricating oil passage
        142 first lubricating oil passage
        143 second lubricating oil passage
        150 metal gasket

## Claims

1. A turbocharger comprising:
a shaft connecting a turbine and a compressor;
a bearing housing having a bearing portion turnably supporting the shaft; and
a sliding bearing interposed between the shaft and the bearing portion,
wherein the sliding bearing is disposed to be directly opposed to each of the shaft and the bearing portion,
wherein the bearing portion is formed of an aluminum-based material,
wherein the shaft is formed of a steel material,
wherein the sliding bearing is formed of a copper-based material,
wherein the bearing housing is divided into a turbine-side housing disposed at a turbine side which is at one side in the axial direction of the shaft, and the turbine-side housing is fixed with a turbine housing including the turbine at one side portion in the axial direction, and a compressor-side housing disposed at a compressor side which is at another side in the axial direction of the shaft,
wherein the turbine-side housing is formed of stainless steel,
wherein the bearing portion is formed in the compressor-side housing,
wherein the turbine-side housing has a side portion in the axial direction and the compressor-side housing has a side portion in the axial direction, and a metal gasket is interposed between the side portion of the turbine-side housing and the side portion of the compressor-side housing so as to maintain a liquid tightness between the compressor-side housing and the turbine-side housing, and
the turbocharger further includes a cooling water passage for supplying cooling water, and the cooling water passage extends from a recess within the turbine-side housing to the compressor-side housing through the metal gasket between the side portion of the turbine-side housing and the side portion of the compressor-side housing.

2. The turbocharger according to claim 1,
wherein the side portion of the turbine-side housing and the side portion of the compressor-side housing are planes that are parallel to each other and that face each other, and the metal gasket is disposed over the side portion of the turbine-side housing and the side portion of the compressor-side housing.