JP5966417B2 - Turbocharger - Google Patents

Description

  The present invention relates to a turbocharger in which a turbine impeller is fixed and accommodated at one end of a turbine shaft.

  2. Description of the Related Art Conventionally, a turbocharger is known in which a turbine shaft having a turbine impeller provided at one end and a compressor impeller provided at the other end is rotatably held by a bearing housing. When such a supercharger is connected to an engine, for example, the turbine impeller is rotated by exhaust gas discharged from the engine, and the compressor impeller is rotated through the turbine shaft by the rotation of the turbine impeller.

  Since the turbine impeller is exposed to high-temperature exhaust gas, an electron beam welding process is used for fixing the turbine shaft and the turbine impeller in consideration of heat resistance. In order to improve the durability in the vicinity of the welded portion of the turbine shaft and the turbine impeller, Patent Document 1 provides a hollow portion that is recessed in the axial direction at one end of the turbine shaft, and is surrounded by one end of the turbine shaft and the wheel. The structure which secured the space is described. When the internal space is provided in this way, the rigidity of the portion of the turbine shaft that forms the radially outer wall surface of the internal space is reduced. Therefore, even if a load is applied to one end of the turbine shaft due to centrifugal force due to the rotation of the turbine impeller, the wall surface portion is elastically deformed, thereby suppressing stress concentration on one end of the turbine shaft and improving durability.

Japanese Examined Patent Publication No. 04-027363

  When one end of the turbine shaft and the turbine impeller are fixed by electron beam welding, since air becomes a hindrance to welding, the welding process is performed in a vacuum work space. However, in the configuration in which the recess is provided as described above, air may remain in the internal space closed by the turbine shaft and the turbine impeller. Then, in the electron beam welding process, there is a risk of causing defects in the welded portion. Further, as compared with a configuration in which no recess is provided, it is necessary to ensure a sufficient time for the vacuuming process in order to surely exclude air from the internal space, and work efficiency is reduced.

  The objective of this invention is providing the supercharger which can suppress the fall of the precision of an electron beam welding, and the fall of work efficiency, maintaining the durability of the fixed part vicinity with the turbine impeller in a turbine shaft. .

In order to solve the above-described problems, a turbocharger according to the present invention includes a turbine shaft in which a recess that is recessed in the axial direction is formed at one end, a wheel that is welded to one end of the turbine shaft, and closes the recess. A turbine impeller having a plurality of blades on the outer periphery of a wheel is a turbocharger that is rotatably accommodated in a turbocharger body, and an internal space in which the recess is closed with the wheel in the turbine shaft And a protruding portion that protrudes toward the inside of the internal space, and the protruding portion is positioned closer to the bottom surface side of the recess than the welded portion between the wheel and the turbine shaft. It is characterized by.

  The protrusion may protrude from the bottom surface of the recess.

  ADVANTAGE OF THE INVENTION According to this invention, the precision fall of electron beam welding and the fall of work efficiency can be suppressed, maintaining the durability of the fixed part vicinity with the turbine impeller in a turbine shaft.

It is a schematic sectional drawing of a supercharger. It is sectional drawing of a turbine shaft and a turbine impeller. It is sectional drawing of the turbine shaft and turbine impeller in a comparative example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is a schematic cross-sectional view of the supercharger C, and FIG. 2 is an external perspective view of the supercharger C. Hereinafter, the direction of arrow F shown in FIG. 1 will be described as the front side of the supercharger C, and the direction of arrow R will be described as the rear side of the supercharger C. As shown in FIG. 1, the supercharger C includes a supercharger main body 1. The supercharger body 1 includes a bearing housing 2, a turbine housing 4 connected to the front side of the bearing housing 2 by a fastening bolt 3, a compressor housing 6 connected to the rear side of the bearing housing 2 by a fastening bolt 5, Are formed integrally.

  The bearing housing 2 is formed with a bearing hole 2a penetrating in the front-rear direction of the supercharger C, and the turbine shaft 7 is rotatably supported by the bearing hole 2a via a bearing. A turbine impeller 8 is integrally fixed to a front end portion (one end) of the turbine shaft 7, and the turbine impeller 8 is rotatably accommodated in the turbine housing 4. A compressor impeller 9 is integrally fixed to the rear end (other end) of the turbine shaft 7, and the compressor impeller 9 is rotatably accommodated in the compressor housing 6.

  The compressor housing 6 is formed with an air inlet 10 that opens to the rear side of the supercharger C and is connected to an air cleaner (not shown). Further, in a state where the bearing housing 2 and the compressor housing 6 are connected by the fastening bolt 5, a diffuser flow path 11 that compresses and pressurizes air is formed by the facing surfaces of both the housings 2 and 6. The diffuser passage 11 is formed in an annular shape from the radially inner side to the outer side of the turbine shaft 7 (compressor impeller 9), and communicates with the intake port 10 via the compressor impeller 9 on the radially inner side. ing.

  Further, the compressor housing 6 is provided with an annular compressor scroll passage 12 positioned on the radially outer side of the turbine shaft 7 (compressor impeller 9) with respect to the diffuser passage 11. The compressor scroll passage 12 communicates with an intake port of an engine (not shown) and also communicates with the diffuser passage 11. Therefore, when the compressor impeller 9 rotates, fluid is sucked into the compressor housing 6 from the intake port 10, and the sucked fluid is boosted in the diffuser flow path 11 and the compressor scroll flow path 12 to be sucked into the engine intake port. Will be led to.

  The turbine housing 4 is formed with a discharge port 13 that opens to the front side of the supercharger C and is connected to an exhaust gas purification device (not shown). Further, the turbine housing 4 is provided with a flow path 14 and an annular turbine scroll flow path 15 positioned on the radially outer side of the turbine shaft 7 (turbine impeller 8) with respect to the flow path 14. The turbine scroll channel 15 communicates with a gas inlet (not shown) through which exhaust gas discharged from the exhaust port of the engine is guided, and also communicates with the channel 14 described above. Therefore, the exhaust gas guided from the gas inlet to the turbine scroll flow path 15 is guided to the discharge port 13 through the flow path 14 and the turbine impeller 8 and rotates the turbine impeller 8 in the flow process. . Then, the rotational force of the turbine impeller 8 is transmitted to the compressor impeller 9 via the turbine shaft 7, and the fluid is boosted by the rotational force of the compressor impeller 9 as described above, and the intake port of the engine Will be led to.

  Since the turbine impeller 8 described above is exposed to high-temperature exhaust gas, an electron beam welding process is used for fixing the turbine shaft 7 and the turbine impeller 8 in consideration of heat resistance. Hereinafter, a fixed portion between the turbine shaft 7 and the turbine impeller 8 will be described in detail.

  FIG. 2 is a cross-sectional view of the turbine shaft 7 and the turbine impeller 8. Here, the compressor impeller 9 side of the turbine shaft 7 is omitted, and the turbine impeller 8 side is shown. Moreover, FIG. 3 is sectional drawing of the position corresponding to FIG. 2 in a comparative example.

  As shown in FIG. 2, the turbine impeller 8 includes a wheel (hub) 20 and blades (blades) 21.

  The wheel 20 has an outer peripheral surface 20a that extends radially outward from one end to the other end, a bottom surface 20b that faces the turbine shaft 7, and an upper surface 20c that is smaller in area than the bottom surface 20b, and the bottom surface 20b and the upper surface 20c. It is a rotating body that rotates around the center of.

  The blades 21 are bent thin plate-like members, and a plurality of blades 21 are equally distributed on the outer peripheral surface 20 a of the wheel 20 in the circumferential direction, extend radially outward from the outer peripheral surface 20 a of the wheel 20, and Bent to tilt in the direction. The blades 21 are integrally formed with the wheel 20 by casting or the like.

  The turbine shaft 7 is a rod member, and a recess 7a that is recessed in the axial direction is formed at one end to which the turbine impeller 8 is fixed.

  An annular projection 20 d extending in the circumferential direction is formed on the bottom surface 20 b of the wheel 20, and this projection 20 d and the tip 7 b of the turbine shaft 7 that is the edge of the recess 7 a of the turbine shaft 7 are formed. After the contact, the contact portion is electron beam welded. In this way, the bottom surface 20 b is fixed to one end of the turbine shaft 7.

  At this time, the recessed part 7a is obstruct | occluded by the bottom face 20b of the wheel 20, and the internal space E enclosed by the said bottom face 20b and the wall surface which forms the recessed part 7a will be provided. When the internal space E is provided, the rigidity of the portion of the turbine shaft 7 that constitutes the radially outer wall surface of the internal space E is reduced, so that the wall surface portion is elastically deformed to the end of the turbine shaft 7. It is possible to suppress the stress concentration and improve the durability.

  By the way, when the end of the turbine shaft 7 and the bottom surface 20b of the wheel 20 are fixed by electron beam welding, since air becomes a hindrance to welding, a vacuum is evacuated to the space where the electron beam welding operation is performed.

  This evacuation process is performed in a state where the protrusion 20d on the bottom surface 20b of the wheel 20 and the tip 7b of the turbine shaft 7 are brought into contact with each other and clamped by a jig. Therefore, there is a possibility that air cannot be sufficiently removed from the internal space E.

  In addition, if air stays in the internal space E, air may enter the welded portion and cause defects (voids). Therefore, in order to reliably remove air from the internal space E, the vacuuming process is sufficient. It is necessary to secure time, and as a result, work efficiency decreases.

  Therefore, in the present embodiment, a protruding portion 22 that protrudes toward the inside of the internal space E is provided on the wall surface that forms the internal space E of the recess 7 a closed by the wheel 20. Here, the protrusion 22 is provided so as to protrude in the axial direction from the bottom surface of the recess 7 a in the turbine shaft 7, more specifically, the turbine shaft 7.

  As described above, the turbocharger C of the present embodiment is provided with the protruding portion 22 on the wall surface of the internal space E at the fixed portion between the turbine shaft 7 and the turbine impeller 8, as in the comparative example shown in FIG. 3. The volume of the internal space E is smaller than that of a configuration that does not have a simple protrusion. Therefore, the supercharger C can quickly remove air from the internal space E in the electron beam welding process between the turbine shaft 7 and the turbine impeller 8, and can suppress a reduction in work efficiency due to the provision of the recess 7a. Further, if air remains in the internal space E, defects may occur in the electron beam welding process. However, since the volume of the internal space E is small in the supercharger C, the air when the vacuum is evacuated as in the conventional case. Is less likely to remain, and the occurrence of defects can be suppressed.

  Since the turbine shaft 7 is formed by cutting a solid bar, even if the projection 22 is provided on the turbine shaft 7, it is difficult to increase the material cost. Therefore, the supercharger C can suppress an increase in manufacturing cost due to the provision of the protrusion 22.

  Moreover, the protrusion part 22 is protruding in the axial direction from the bottom face of the recessed part 7a. Thus, the structure which raises a bottom face can form the protrusion part 22 easily by a lathe process, for example, and the supercharger C can further suppress the raise in the manufacturing cost by having provided the protrusion part 22. FIG.

  In the embodiment described above, the case where the protrusion 22 is provided on the turbine shaft 7 has been described. However, the protrusion may be provided on the wheel 20 of the turbine impeller 8 and protrude in the axial direction.

  Moreover, although embodiment mentioned above demonstrated the case where the one protrusion part 22 was provided, multiple protrusion parts may be received.

  Moreover, although embodiment mentioned above demonstrated the case where the protrusion part 22 was provided in the bottom face of the recessed part 7a, a protrusion part is the radial direction wall surface of the internal space E, ie, the circumferential direction among the recessed parts 7a. It may be provided on an annular inner peripheral surface extending to the surface. In this case, the protruding portion protrudes radially inward from the inner peripheral surface, and for example, a plurality of protruding portions are arranged at equal intervals in the circumferential direction. By arranging a plurality of protrusions at intervals, the rigidity of the portion constituting the radially outer wall surface of the internal space E can be reduced and stress concentration can be reduced compared to a case where one annular protrusion is formed. It can be suppressed to improve durability.

  In the above-described embodiment, the case where the protrusion 20d is formed on the wheel 20 has been described. However, the protrusion 20d is not formed, and the tip 7b of the turbine shaft 7 is directly welded to the bottom 20b of the wheel 20. Also good.

  Moreover, the fixed part of the turbine shaft 7 and the wheel 20 may have an inlay structure. In this case, for example, the outer diameter of the tip 7b of the turbine shaft 7 is set to a size that can be fitted inside the protrusion 20d, and the protrusion is an annular protrusion that protrudes radially outward from the turbine shaft 7. An abutting portion that abuts against the end face in the axial direction of 20d is provided. Then, the end face in the axial direction of the protrusion 20d and the contact portion may be electron beam welded.

  Further, the inlay structure of the fixed portion between the turbine shaft 7 and the wheel 20 may be configured such that the projection 20 d of the wheel 20 is fitted into the recess 7 a of the turbine shaft 7.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  The present invention can be used for a supercharger in which a turbine impeller is fixed and accommodated at one end of a turbine shaft.

C ... supercharger E ... internal space 1 ... supercharger body 7 ... turbine shaft 7a ... recess 8 ... turbine impeller 20 ... wheel 21 ... blade 22 ... projection

Claims (2)

A turbine shaft in which a hollow that is recessed in the axial direction is formed at one end, a wheel that is welded to one end of the turbine shaft to close the hollow, and a turbine impeller that has a plurality of blades on the outer periphery of the wheel are supercharged. A turbocharger that is rotatably accommodated in the machine body,
Of the turbine shaft, a wall surface forming an internal space in which the recess is closed with the wheel is provided with a protruding portion that protrudes toward the inside of the internal space ,
The supercharger , wherein the protruding portion is located on a bottom surface side of the recessed portion with respect to a welding portion between the wheel and the turbine shaft . The supercharger according to claim 1 , wherein the protruding portion protrudes from a bottom surface of the recess.

Images