Patent Application
20140090375
The present invention relates to a cooling structure for a bearing housing which rotatably supports a turbine rotor and a compressor of a turbocharger and, in particular to, improvement of a cooling water path formed in a bearing housing.
There are bearing housings for a turbocharger, which are provided with a cooling structure using water or air to protect from a high temperature environment caused by exhaust gas a supporting part of a shaft which integrally connects a turbine rotor to a compressor.
For instance, there is a cooling structure configured to promote a flow of cooling water in a water jacket by connecting an inlet and an outlet of a circulation water passage to the water jacket and providing a partition board at the connection part to partition the passage into an inlet side and an outlet side (Patent Document 1). There is another cooling structure in which a top part partitioning wall is provided at a top part of a cooling water jacket and an inlet and an outlet for cooling water are formed in both sides with respect to the partitioning wall (Patent Document 2).
According to
According to
In Patent Document 1, by providing the portioning board 5, the cooling water introduced to the water inlet passage 2 is regulated by the portioning board 5, and it is made easier for the cooling water to flow along a peripheral wall of the water jacket 16. However, the water passage flange 1 is fixed to the center housing 6 with a plurality of screws 4 and thus, the number of parts is large and the productivity is low.
Further, when a water pump stops during engine shutdown, the portioning board 5 hinders occurrence of natural convection in the water inlet passage 2, the water jacket 7 and the water outlet passage 3, respectively. Thus, under a harsh temperature environment due to the heat transferred from the turbine side to the center housing 6 and the turbine shaft 13 during operation of the engine, a heat-soak back phenomenon takes place, and a radial metal 12 becomes subjected to high temperature, resulting in carbonization of the lubricating oil around a radial metal 12.
In Patent Document 2, the cooling water jacket 31 is partitioned in the upper part by the top part portioning wall 32 and thus, the cooling water flow tends to stagnate in a section of the cooling water jacket 31 between the inlet 33 and the outlet 34 of the cooling water jacket 31 and the top part portioning wall 32. If the air gets mixed in the cooling water, the air tends to accumulate in the above section, resulting in reduced cooling performance. Further, the above-mentioned heat-soak back phenomenon is likely to occur.
Moreover, in the case of casting the bearing housing 3, as the cooling water jacket 31 is partitioned by the top part portioning wall 32, it is difficult to discharge core sand in the cooling water jacket 31, resulting in a productivity issue.
It is an object of the present invention to provide a cooling structure for a bearing housing for a turbocharger, which makes it possible to improve cooling performance while improving productivity and suppressing occurrence of a heat-soak back phenomenon.
To achieve the above object, the present invention provides a cooling structure for a bearing housing for a turbocharger in which a turbine housing for housing a turbine rotor is attached to a compressor housing for housing a compressor rotor via the bearing housing, the turbine rotor and the compressor is connected by a shaft and the shaft is rotatably supported via the bearing in the bearing housing, the cooling structure comprising:
an annular cooling water path formed in the bearing housing and surrounding the shaft and the bearing so as to cool the bearing housing and the bearing with cooling water flowing in the annular cooling water path;
a water path inlet provided in the bearing housing to communicate with the annular cooling water path, the cooling water being supplied to the annular cooling water path from the water path inlet;
a water path outlet provided in the bearing housing to communicate with the annular cooling water path, the cooling water being discharged from the water path outlet; and
a partial partition for partially closing a water path disposed between the water path inlet and the water path outlet, and
the partial partition is arranged in a shortest path of the water path between the water path inlet and the water path outlet.
According to the present invention, by means of the partial partition, the cooling water supplied to an interior of the bearing housing from the water path inlet flows to the annular cooling water path without directly flowing to the water path outlet. As a result, the circulating amount of the cooling water in the annular cooling water path increases.
By arranging the partial partition in the shortest bath between the water path inlet and the water path outlet, the cooling water does not flow directly to the water path outlet from the water path inlet. This facilitates the flow of the cooling air passing outside the partial partition wall and to the annular cooling water path side so as to increase the circulation amount of the cooling water in the annular cooling water path.
With the above configuration, it is possible to facilitate heat transfer to the cooling water in the bearing, the bearing housing and the annular cooling water path from the shaft. As a result, the cooling performance of cooling the bearing can be enhanced.
Moreover, the annular cooling water path is not completely closed by the partial partition and thus, in the case of producing the bearing housing by casting and forming the annular cooling water path using a sand mold core, core sand can be easily removed by shot blasting. As a result, it is possible to improve the productivity of the bearing housing and reduce the cost.
Further, when a water pump stops during engine shutdown, forced circulation of the cooling water in the annular cooling water path is stopped. However, by providing the partial partition, natural convection of the cooling water occurs through unclosed sections of the water path between the water path inlet and the water path outlet and the annular cooling water path. As a result, it is possible to secure the cooling performance, and the heat soak-back phenomenon does not easily occur, hence avoiding carbonization of the lubricant circulating in the bearing.
Furthermore, the air that enters the water path between the water path inlet and the water path outlet and the annular cooling water path is discharged through the unclosed section of the water path. Therefore, reduction in cooling ability caused by air entrainment can be avoided to secure the cooling performance.
In the present invention, the cooling structure may further comprise:
a side water path arranged to be offset in an axial direction with respect to the annular cooling water path, in the side water path, the water path inlet and the water path outlet being provided and the shortest path being formed, and
the partial partition is arranged at a height in the flow path formed by the annular cooling water path and the side water path, the height being 20 to 80% of an axial height of the flow path along the axial direction of the flow path.
According to the present invention, by setting the height of the partial partition in the axial direction to 20 to 80% of an axial height of the flow path along the axial direction of the flow path, the circulating amount of the cooling water in the annular cooling water path can be changed by changing a shape and size of the annular cooling water path, positions and inner diameters of the water path inlet and the water path outlet, and the number of the water path inlets and the water path outlets. Therefore, the circulating amount of the cooling water in the annular cooling water path can be adjusted in accordance with use conditions of the turbocharger.
It is preferable in the present invention that the partial partition is configured to almost completely close the side water path at said axial height.
With this configuration, the cooling water entering the side water path through the water path inlet flows in the axial direction along the partial partition, reaches the annular cooling water path and then flows along the partial partition to the water path outlet to flow out of the side water path. As a result, it is possible to facilitate the cooling water circulation in the annular cooling water path and improve the cooling performance.
In the present invention, the partial partition may have an inclined face inclining relative to the axial direction of the shaft so as to facilitate a flow of the cooling water to the annular cooling water path from the water path inlet or to the water path outlet from the annular cooling path.
By providing the inclined face in the partial partition, the cooling water can flow easily from the water path inlet to the annular cooling water path, or from the annular cooling water path to the water path outlet. Therefore, the circulating cooling water amount in the annular cooling water path can be increased to improve the cooling performance.
In the present invention, plural sets of the water path inlet and the water path outlet may be provided, and the partial partition may be provided in each of the plural sets of the water path inlet and the water path outlet.
With this configuration, it is made easy to select a set from the plural sets of the water path inlet and the water path outlet, which is at a position corresponding to an engine where the turbocharger is to be mounted. Therefore, regardless of the water path inlet and outlet of each engine model, it is possible to enhance stability of the cooling performance of the turbocharger.
Further, in the present invention, the partial partition may be divided into a plurality of sections.
By dividing the partial partition into a plurality of sections, the cooling air entering through the water path inlet can be easily introduced to the annular cooling water path, and the circulation cooling water amount in the annular cooling water path can be further increased.
According to the present invention, the cooling water supplied to the turbine housing through the water path inlet can be circulated in the annular cooling water path by means of the partial partition. Thus, it is possible to facilitate circulation of the cooling water in the annular cooling water path and increase the circulating water amount. Therefore, it is possible to facilitate heat transfer to the cooling water in the bearing, the bearing housing and the annular cooling water path from the shaft. As a result, the cooling performance of cooling the bearing can be enhanced.
Further, the annular cooling water path is not closed by the partial partition and thus, in the case of producing the bearing housing by casting and forming the annular cooling water path using a sand mold core, core sand can be easily removed by shot blasting. Therefore, it is possible to improve the productivity of the bearing housing and reduce the cost.
Furthermore, even when the water pump stops during engine shutdown, natural convection of the cooling water occurs in the water path between the water path inlet and the water path outlet and the annular cooling water path. As a result, it is possible to secure the cooling performance, and the heat soak-back phenomenon does not occur easily, hence avoiding carbonization of the lubricant which circulates in the bearing.
Moreover, the air that enters the water path between the water path inlet and the water path outlet and the annular cooling water path can be easily discharged. Therefore, reduction in cooling ability caused by air entrainment can be avoided so as to maintain the cooling performance.
Further, by providing plural sets of the water path inlet and the water path outlet, it is possible to enhance the cooling performance stability of the turbocharger regardless of the water path inlet and outlet of each engine model. By making it as a casting having plurality sets of the water path inlet and the water path outlet, the single casting can be used flexibly for a variety of water supply discharge layouts.
Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It is intended, however, that unless particularly specified, dimensions, materials, shapes, relative positions and the like of components described in the embodiments shall be interpreted as illustrative only and not limitative of the scope of the present invention.
As illustrated in
The turbine 11 is provided with a turbine housing 16 coupled to an end of the bearing housing 13 by a coupling member 15 and a turbine rotor 17 rotatably housed in the turbine housing 16.
The turbine housing 16 is formed by an exhaust gas introduction port 21, a scroll part 22 and an exhaust gas exhaust port 23 are formed. The scroll part 22 is an exhaust gas passage which is formed into a scroll shape from the exhaust gas introduction port 21 and which gradually decreases in cross-sectional area toward the turbine rotor 17.
Further, a wastegate valve 25 is provided to regulate the amount of the exhaust gas supplied to the turbine rotor 17 by diverting a part of the exhaust gas, and an actuator 26 is provided to open and close the wastegate valve 25.
The compressor 12 is provided with a compressor housing 32 coupled to the other end of the bearing housing 13 and a compressor rotor 33 rotatably housed in the compressor housing 32.
In the compressor housing 32, a compressor introduction port 35 for introducing the air, a scroll part 36 formed into a scroll shape and a compressor exhaust port (not shown) are formed. The scroll part 36 communicates with the compressor introduction port 35. The compressor exhaust port is connected to the engine side to discharge the air.
One end of the shaft 41 is attached to the turbine rotor 17 and the other end of the shaft 41 is formed into a male screw 41a. With this male screw 41a and a nut 42, the compressor rotor 33 is attached to the other end of the shaft 41.
The shaft 41 is rotatably supported by bearing housing 13 via the journal bearings 52, 53.
As illustrated in
To cool a part of the bearing housing 13 and the bearings 52, 53 which is on the side nearer to the turbine 11, the annular cooling water path 13f is arranged to overlap an inner side of the coupling member in an extending direction of an axis 41c of the shaft 41 (an axial direction of the shaft 41), and the water path inlet 13h and the water path outlet 13j are arranged to be offset by an offset amount 6 in the axial direction of the shaft 41 with respect to the annular cooling water path 13f and in the direction of moving away from the turbine 11.
The lubricant supply path 13k is formed by a lubricant introduction port 13p for introducing the lubricant and a plurality of oil paths 13q, 13r, 13s, 13t which branch from the lubricant introduction port 13p. Through these oil paths 13q, 13r, 13s, 13t, the lubricant is supplied to sliding parts of the journal bearings 52, 53 and the thrust bearing 56.
After lubricating the sliding part of each of the bearings 52 to 55, the lubricant oil is allowed to escape to the space 13m from the sliding part to be discharged through the lubricant exhaust port 13n and then returned to an oil pan of the engine.
The inlet side water path 13w is formed in the water path inlet 13h, and the outlet side water path 13x is formed in the water path outlet 13j.
On a side of the annular cooling water path 13f, a port part 13z where the side water path 13v is formed is provided. In this port part 13z, the water path inlet 13h and the water path outlet 13j are provided.
The side water path 13v allows communication between: the water path inlet 13h and the water path outlet 13j; and the annular cooling water path 13f.
In the port part 13z, a partial partition 14a is integrally formed in the bearing housing 13. The partial partition 14a is arranged at a position higher than the inlet side water path 13w and lower than the outlet side water path 13x. The partial partition 13a is configured to partially partition the section where the side water path 13V is connected to the annular cooling water path 13f.
Specifically, the partial partition 14a is configured to extend in the axial direction of the shaft 14 (see
The following relationship is set, HS/HT=0.2˜0.8, where HS is a height of the partial partition 14a in the axial direction and HT is a height of the annular cooling water path 13f and the side water path 13v in the axial direction (the height of the housing cooling water path 60 in the axial direction). HS/HT=0.2 is a value of overlap of the partial partition 13f partially overlapping a water path in such a case that the water path is provided to linearly connect the inlet side water path 13w and the outlet side water path 13x. HS/HT=0.2˜0.8 is a value which is set with production variations in mind.
It is preferable that HS=W where W is a width of the side water path 13v. With HS=W, the partial partition 14a does not project in the annular cooling water path 13f so as not to interfere circulation of the cooling water in the annular cooling water path 13f.
Specifically, the partial partition 14a extends outward toward the annular cooling water path 13f from the side wall 14f of the port part 13z.
Operation of the cooling structure for the bearing housing as described above is now explained in reference to
In a first embodiment illustrated in
A part of the cooling water having circulated the annular cooling water path 13f continues to circulate as indicated by an arrow D, while the rest of the cooling water hits the partial partition 14a to change its direction to flow upward and then discharged through the water path outlet 13j as indicated by an arrow D.
In a first comparative example illustrated in
In a second comparative example illustrated in
In the first embodiment illustrated in
In the first comparative example illustrated in
Further, by the natural convection of the cooling water in the annular cooling water path 102 from the lower part to the upper part, cooling water circulation is generated as indicated by arrows R, R. However, by the natural convection in the annular cooling water path 102 alone, it is difficult to circulate the cooling water compared to the first embodiment illustrated in
In the second comparative example illustrated in
As explained in reference to
By partially closing the annular cooling water path 13f and the side water path 13v by the partial partition 14a, in the case of producing the bearing housing 13 by casting and forming the annular cooling water path 13f using a sand mold core, core sand can be easily removed by shot blasting.
Therefore, it is possible to improve the productivity of the bearing housing 13 and to reduce the cost.
Further, it is possible to easily remove the air mixed in the side water path 13v, the annular cooling water path 13f, and the like between the water path inlet 13h and the water path outlet 13j from the unclosed section 14b (see
As illustrated in
As illustrated in
As illustrated in
As illustrated in
The first partition 75a and the second partition 75b are not aligned. Thus, the cooling water hits the first partition 75a and the second partition 75b to change its flow direction as indicated by arrows, which substantially coincide with each other. As a result, it is possible to facilitate circulation of the cooling water in the annular cooling water path 13f.
As illustrated in
The first partition 77a has flat inclined faces 77c, 77d formed on both sides. The second partition 77b has flat inclined faces 77e, 77f formed on both sides. The inclined face 77c of the first partition 77a and the inclined face 77e of the second partition 77b are in the same plane, and the inclined face 77d of the first partition 77a and the inclined face 77f of the second partition 77b are in the same plane.
With this configuration, it is possible to further facilitate the cooling water flow to the annular cooling water path 13f from the water path inlet 13h and to the water path outlet 13j from the annular cooling water path 13f.
As illustrated in
By providing a plurality of the port part, i.e. the first port part 81a and the second port part 81b, it is possible to select either one of the first port part 81a and the second port part 81b, that has the partial partition 81e or 81h with higher effect (the facilitation effect of facilitating the cooling water circulation in the annular cooling water path 13f, which is different for each port part due to production variations
As illustrated in
Further, a partial partition 83e is provided in the first port part 83a, and a partial partition 83h is provided in the second port part 83b.
As illustrated in the drawing, the water path inlets 83c, 83f are directed toward the partial partitions 83e, 83h, respectively. This makes it easy for the cooling water to hit the partial partitions 83e, 83h. As a result, the cooling water can easily flow toward the annular cooling water path 13f, and the cooling water circulation in the annular cooling water path 13f can be facilitated so as to further enhance the cooling performance.
As illustrated in
In the first port 85a, a water path inlet 85c, a water path outlet 85d and a partial partition 85e are provided. In the second port 85b, a water path inlet 85f, a water path outlet 85g and a partial partition 85h are provided.
By providing the first port part 85a and the second port part 85b in the upper and lower parts of the bearing housing 85, it is possible to select a connecting location of cooling water piping depending on an engine to which the turbocharger is mounted. This facilitates connection of the cooling water piping.
In fourth and fifth embodiments illustrated in
Further, as illustrated in
The present invention is suitable for cooling the bearing housing for the turbocharger.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-145859 | Jun 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/066030 | 6/22/2012 | WO | 00 | 12/16/2013 |
