JP2010275878A - Impeller, supercharger, and method for manufacturing the impeller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability of an impeller 27 by sufficiently securing fatigue strength of a wheel 55. <P>SOLUTION: The impeller 27 includes an impeller body 53 formed by sintering a molding 53F molded by metal powder injection molding, and a solid cylindrical member 61 is compressively fitted into the fitting hole 59 of the wheel 55 in the impeller body 53. The cylindrical member 61 is so configured that with the cylindrical member inserted into a portion 59F corresponding to the fitting hole in the molding 53F, heat contraction when the molding 53F is sintered is regulated to thereby generate a residual stress in the center of the wheel 55. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an impeller used for a supercharger such as a supercharger for a vehicle.

  A general configuration of a turbine impeller (an example of an impeller) in a supercharger for a vehicle will be described as follows (see Patent Document 1, Patent Document 2, and Patent Document 3).

  The turbine impeller generates a rotational force (rotational torque) using the pressure energy of the exhaust gas, and is usually formed of a molded body formed by precision casting. The turbine impeller includes a solid turbine wheel rotatably provided in a turbine housing of the vehicle supercharger, and the turbine wheel is integrally connected to a rotor shaft in the vehicle supercharger. Therefore, the outer peripheral surface of the turbine wheel extends radially outward from the axial direction of the turbine impeller. Further, a plurality of turbine blades are integrally formed on the outer peripheral surface of the turbine wheel at intervals in the circumferential direction, and the outer edge of each turbine blade extends along the shroud (inner wall surface) of the turbine housing. .

  Accordingly, during operation of the vehicle supercharger, the exhaust gas taken into the turbine housing is circulated from the inlet side of the turbine impeller to the outlet side (from the upstream side to the downstream side of the turbine impeller as viewed from the exhaust gas flow direction). Thus, the rotor shaft can be rotated integrally with the turbine impeller by generating a rotational force using the pressure energy of the exhaust gas.

JP 2000-265844 A JP 2007-56791 A Japanese Patent Laid-Open No. 11-62603

  By the way, during operation of the turbocharger for the vehicle, centrifugal stress is generated in the turbine wheel. When the rotational speed of the turbine impeller is increased, the centrifugal stress of the turbine wheel is increased, and when the rotational speed of the turbine impeller is decreased, Centrifugal stress decreases. Therefore, when the fluctuation range of the rotation speed of the turbine impeller is increased, the stress amplitude of the turbine wheel (fluctuation range of centrifugal stress) is also increased, so that the fatigue strength of the turbine wheel is sufficiently secured, and the durability of the turbine impeller is increased. There is a problem that it is difficult to improve the performance.

  Therefore, an object of the present invention is to provide an impeller or the like having a novel configuration that can solve the above-described problems.

  A first feature of the present invention is that an impeller used in a supercharger is formed by sintering a molded body formed by metal powder injection molding, and an outer peripheral surface is directed from the axial direction to the radially outer side. And a plurality of blades integrally formed on the outer peripheral surface of the wheel at intervals in the circumferential direction, and a circular fitting hole is formed along the axial direction in the center of the wheel. An impeller body and a compression fitting (fitted in a compressed state) in the fitting hole of the impeller body, and in a state of being inserted into a portion corresponding to the fitting hole in the molded body, The gist of the invention is to provide a cylindrical member that regulates thermal shrinkage during sintering and generates residual stress in the wheel.

  The “impeller” includes a compressor impeller that compresses air using centrifugal force, in addition to a turbine impeller that generates rotational force (rotational torque) using pressure energy of exhaust gas. The “fitting hole” includes a bottomed fitting hole (through hole) in addition to a bottomless fitting hole (through hole), and the “cylindrical member” includes a solid hole. In addition to the cylindrical member, a hollow cylindrical member is also included.

  According to the first feature, since the cylindrical member regulates thermal shrinkage during sintering of the molded body and generates residual stress in the wheel, the impeller rotates during operation of the supercharger. Even if the number decreases, the width of the centrifugal stress of the wheel can be reduced. Thereby, even if the fluctuation range of the rotation speed of the impeller increases, an increase in the stress amplitude of the wheel (the fluctuation range of the centrifugal stress) can be suppressed.

  Further, the impeller body is formed by sintering the molded body formed by metal powder injection molding, and the circular fitting hole is formed along the axial direction at the center of the wheel. Therefore, in other words, since the molded body before sintering has a portion corresponding to the fitting hole at the center, the portion corresponding to the wheel in the molded body before sintering is thinned. Can be realized.

  The second feature of the present invention is that the supercharger that supercharges the air supplied to the engine using the energy of the exhaust gas from the engine comprises the impeller comprising the first feature. And

  According to the 2nd characteristic, there exists an effect | action similar to the effect | action by a 1st characteristic.

  According to a third aspect of the present invention, in the manufacturing method for manufacturing an impeller according to the first aspect, an injection having a molding surface similar to a shape (a complementary shape) that reverses the final shape of the impeller body. By using a molding die and injecting a mixture of metal powder and a binder into a cavity defined by the molding surface of the injection molding die, the shape is similar to the final shape and the central portion is An injection process for forming a molded body having a portion corresponding to a fitting hole, a degreasing process (removing process) for degreasing (removing) the binder contained in the molded body after the injection process, and the degreasing process After completion of the process, the molded body is heat-shrinked to the final shape by firing and sintering the molded body in a state where the cylindrical member is inserted into a portion corresponding to the fitting hole in the molded body. And a sintering step of producing the impeller body made of the molded body and regulating thermal contraction of the molded body by the cylindrical member to generate residual stress in the wheel. And

  According to a third feature, in the sintering step, the molded body is fired and sintered in a state where the cylindrical member is inserted into a portion corresponding to the fitting hole in the molded body. In addition to producing the impeller body made of a body, the cylindrical member regulates the thermal contraction of the molded body and generates residual stress in the wheel, so that the impeller rotates during operation of the supercharger. Even if the number decreases, the width of the centrifugal stress of the wheel can be reduced. Thereby, even if the fluctuation range of the rotation speed of the impeller increases, an increase in the stress amplitude of the wheel (the fluctuation range of the centrifugal stress) can be suppressed.

  Further, in the injection process, since the molded body having a portion corresponding to the fitting hole is formed at the center, the portion corresponding to the wheel in the molded body before sintering is thinned. can do.

  According to the present invention, even if the fluctuation range of the rotation speed of the impeller is increased, an increase in the stress amplitude of the wheel can be suppressed, so that the fatigue strength of the wheel is sufficiently ensured and the impeller is durable. (The durability of the supercharger) can be improved.

  Further, since it is possible to realize a thin portion corresponding to the wheel in the molded body before sintering, a portion such as a nest is formed in a portion corresponding to a hole in the molded body when the molded body is sintered. The impeller can be stably manufactured while suppressing the occurrence of defects.

It is an enlarged view of the arrow I part in FIG. It is sectional drawing of the supercharger for vehicles which concerns on 1st Embodiment. It is sectional drawing of the turbine impeller which concerns on 1st Embodiment. It is a figure explaining the injection process in the manufacturing method of the impeller concerning a 2nd embodiment. It is a figure explaining the degreasing process in the manufacturing method of the impeller which concerns on 2nd Embodiment. It is a figure explaining the sintering process in the manufacturing method of the impeller which concerns on 2nd Embodiment. It is sectional drawing of the turbine impeller which concerns on the modification of this invention.

[First Embodiment]
The vehicle supercharger according to the first embodiment will be described with reference to FIGS. In the drawings, “L” indicates the left direction and “R” indicates the right direction.

  As shown in FIGS. 1 and 2, the vehicular supercharger 1 according to the first embodiment supercharges the air supplied to the engine using the energy of the exhaust gas from the engine (not shown). Compression). And the specific structure of the supercharger 1 for vehicles is as follows.

  The vehicular supercharger 1 includes a bearing housing 3, and a radial bearing 5 and a pair of thrust bearings 7 are provided in the bearing housing 3. A rotor shaft (turbine shaft) 9 extending in the direction is rotatably provided. In other words, the rotor shaft 9 is rotatably provided in the bearing housing 3 via a plurality of bearings 5 and 7. .

  A compressor housing 11 is provided on the right side of the bearing housing 3, and a compressor impeller 13 that compresses air using centrifugal force is rotatably provided in the compressor housing 11. The specific components of the compressor impeller 13 will be described. A compressor wheel 15 is provided in the compressor housing 11, and the compressor wheel 15 is integrally connected to the right end portion of the rotor shaft 9. Thus, the compressor impeller 13 can rotate around the axis C (in other words, the axis of the rotor shaft 9) C. Further, the outer peripheral surface of the compressor wheel 15 extends radially outward from the axial direction of the compressor impeller 13 (compressor wheel 15). Further, a plurality of compressor blades 17 are integrally formed on the outer peripheral surface of the compressor wheel 15 at intervals in the circumferential direction, and the outer edge of each compressor blade 17 is along the shroud (inner wall surface) of the compressor housing 11. It extends like so.

  An air intake port 19 for taking in air is formed on the inlet side of the compressor impeller 13 in the compressor housing 11 (upstream side of the compressor impeller 13 when viewed from the air flow direction). It can be connected to an air cleaner (not shown) via a tube (not shown). An annular diffuser passage 21 for increasing the pressure of the compressed air is provided on the outlet side of the compressor impeller 13 between the bearing housing 3 and the compressor housing 11 (downstream side of the compressor impeller 13 as viewed from the air flow direction). The diffuser flow path 21 is formed and communicates with the air intake port 19. Further, a compressor scroll passage 23 is formed inside the compressor housing 11 so as to surround the compressor impeller 13, and the compressor scroll passage 23 communicates with the diffuser passage 21. An air discharge port (not shown) for discharging the compressed air is formed at an appropriate position of the compressor housing 11, and this air discharge port communicates with the compressor scroll passage 23, and Can be connected to an air supply manifold (not shown).

  A turbine housing 25 is provided on the left side of the bearing housing 3, and a turbine impeller 27 that generates rotational force (rotational torque) using the pressure energy of the exhaust gas is rotatable in the turbine housing 25. Is provided. Note that specific components of the turbine impeller 27 will be described later.

  A variable nozzle unit 29 is provided in the turbine housing 25 so as to surround the turbine impeller 27. The specific components of the variable nozzle unit 29 will be described. A nozzle ring 31 is provided on the radially outer side of the turbine impeller 27 in the turbine housing 25 via a mounting ring 33. The shroud ring 35 is provided integrally and spaced apart from the left and right via a plurality of (only one shown) connecting pins 37. A plurality of variable nozzles 39 are provided between the nozzle ring 31 and the shroud ring 35 at intervals in the circumferential direction, and each variable nozzle 39 has an axis parallel to the axis C of the turbine impeller 27. The nozzle shafts 41 of the plurality of variable nozzles 39 are pivotally connected (swingable) around the center, and are interlocked and connected by a synchronization mechanism 43 as shown in Patent Document 1.

  A transmission shaft 45 is rotatably provided at the lower left portion of the bearing housing 3, and a right end portion of the transmission shaft 45 is an actuator such as a cylinder that rotates a plurality of variable nozzles 39 synchronously. (Not shown) is connected (linked and linked) via a connection lever 47, and the left end of the transmission shaft 45 is connected to the synchronization mechanism 43.

  A gas intake (not shown) for taking in exhaust gas is formed at an appropriate position of the turbine housing 25, and this gas intake can be connected to an exhaust manifold (not shown) of the engine. Further, a turbine scroll passage 49 is formed inside the turbine housing 25 so as to surround the turbine impeller 27. The turbine scroll passage 49 communicates with a gas intake port to collect exhaust gas. It is possible to enter. Further, a gas discharge port 51 for discharging exhaust gas is formed on the outlet side of the turbine impeller 27 in the turbine housing 25 (downstream side of the turbine impeller 27 when viewed from the flow direction of the exhaust gas). 51 is communicated with the turbine scroll flow path 49 and can be connected to an exhaust gas purification device (not shown) via a connecting pipe (not shown).

  Then, the specific structure of the turbine impeller 27 which is the principal part of 1st Embodiment is demonstrated.

  As shown in FIG. 3, the turbine impeller 27 includes a turbine impeller body 53. The turbine impeller body 53 is a molded body 53F (see FIGS. 6 and 7A) formed by metal powder injection molding. ) And is manufactured through an injection process, a degreasing process, and a sintering process, which will be described later. The turbine impeller main body 53 includes a turbine wheel 55 provided in the turbine housing 25, and this turbine wheel 55 is integrally connected to the left end portion of the rotor shaft 9, and It can rotate around an axis (in other words, the axis of the turbine impeller body 53 or the axis of the rotor shaft 9) C. Further, the outer peripheral surface of the turbine wheel 55 extends outward in the radial direction from the axial direction of the turbine impeller 27 (turbine impeller body 53). Further, a plurality of turbine blades 57 are integrally formed on the outer peripheral surface of the turbine wheel 55 at intervals in the circumferential direction, and the outer edge of each turbine blade 57 is along the shroud (inner wall surface) of the shroud ring 35. It extends like so. A circular bottomless fitting hole (through hole) 59 is formed in the center of the turbine wheel 55 along the axial direction of the turbine impeller 27.

  A solid cylindrical member 61 is compression-fitted (fitted in a compressed state) into the fitting hole 59 of the turbine wheel 55, and this cylindrical member 61 corresponds to a fitting hole in the molded body 53F. In the state inserted in the part 59F (refer to FIG. 6 and FIG. 7A), the thermal contraction at the time of sintering of the molded body 53F is regulated to generate a residual stress in the central portion of the turbine wheel 55. A hollow cylindrical member may be compression-fitted into the fitting hole 59 of the turbine wheel 55 instead of the solid cylindrical member 61.

  Then, the effect | action and effect of the supercharger 1 for vehicles which concern on 1st Embodiment are demonstrated.

  The exhaust gas taken into the turbine scroll passage 49 from the gas inlet is circulated from the inlet side of the turbine impeller 27 to the outlet side (from the upstream side to the downstream side of the turbine impeller 27 as viewed from the flow direction of the exhaust gas). The rotor shaft 9 and the compressor impeller 13 can be rotated integrally with the turbine impeller 27 by generating a rotational force (rotational torque) using the pressure energy of the gas. Thereby, the air taken in from the air intake port 19 can be compressed and discharged from the air discharge port via the diffuser passage 21 and the compressor scroll passage 23, and the air supplied to the engine is supercharged. be able to.

  Here, when the flow rate of the exhaust gas is small (in other words, when the engine speed is in the low speed range), the turbine is rotated by synchronizing the plurality of variable nozzles 39 in the direction in which the plurality of variable nozzles 39 are throttled. The flow rate of the exhaust gas supplied to the impeller 27 side is increased to ensure a sufficient work amount of the turbine impeller 27. On the other hand, when the flow rate of the exhaust gas is large (in other words, when the engine speed is in the low speed range), the variable nozzles 39 are rotated in synchronization with the opening direction of the plurality of variable nozzles 39 by the actuator. The throat area of 39 is increased and a large amount of exhaust gas is supplied to the turbine impeller 27 side. As a result, the rotational force can be generated sufficiently and stably by the turbine impeller 27 regardless of the flow rate of the exhaust gas (normal action by the vehicle supercharger 1).

  In addition to the normal operation of the vehicle supercharger 1 described above, the cylindrical member 61 regulates thermal shrinkage during the sintering of the molded body 53F and generates residual stress in the central portion of the turbine wheel 55. Even when the rotational speed of the turbine impeller 27 is reduced during the operation of the vehicle supercharger 1, it is possible to reduce the decrease in the centrifugal stress of the turbine wheel 55. Thereby, even if the fluctuation range of the rotation speed of the turbine impeller 27 increases, an increase in the stress amplitude of the turbine wheel 55 (the fluctuation range of the centrifugal stress) can be suppressed.

  The turbine impeller main body 53 is formed by sintering a molded body 53F formed by metal powder injection molding, and a circular fitting hole 59 is formed in the axial direction of the turbine impeller 27 at the center of the turbine wheel 55. In other words, since the molded body 53F before sintering has a portion 59F (see FIGS. 6 and 7A) corresponding to the fitting hole at the center, the sintered body 53F is sintered. It is possible to reduce the thickness of a portion 55F (see FIGS. 6 and 7A) corresponding to the turbine wheel in the molded body 53F before linking (a specific action by the vehicle supercharger 1 (turbine impeller 27)). ).

  Therefore, according to the vehicle supercharger 1 (turbine impeller 27) according to the first embodiment, even if the fluctuation range of the rotational speed of the turbine impeller 27 increases, the stress amplitude of the turbine wheel 55 (the fluctuation range of the centrifugal stress). ) Can be suppressed, the fatigue strength of the turbine wheel 55 can be sufficiently secured, and the durability of the turbine impeller 27 (the durability of the vehicle supercharger 1) can be improved.

  Further, since it is possible to reduce the thickness of the portion 55F corresponding to the turbine wheel in the green body 53F before sintering, the portion 55F corresponding to the turbine hole in the green body 53F is sintered when the green body 53F is sintered. The occurrence of defects such as nests can be suppressed and the turbine impeller 27 can be stably manufactured.

[Second Embodiment]
The injection mold according to the second embodiment and the method for manufacturing the impeller according to the second embodiment will be described with reference to FIGS. In the drawings, “L” indicates the left direction and “R” indicates the right direction.

  As shown in FIG. 4, an injection mold 63 according to the second embodiment is used for carrying out the impeller manufacturing method according to the second embodiment, and is for injection molding according to the second embodiment. The specific configuration of the mold 63 is as follows.

  That is, an injection molding integrated mold 67 is detachably provided on the left side of the fixed frame 65 in the injection molding machine, and this injection molding integrated mold 67 is mounted on the left side of the rear surface of the turbine impeller body 53 (turbine wheel). The sub-molding surface 69 has a shape similar to the shape (complementary shape) of reversing the final shape of the rear surface of 55. A guide block 73 is detachably provided on the right side of the movable frame 71 movable in the left-right direction in the injection molding machine, and a truncated cone-shaped recess 75 is formed on the right side of the guide block 73. ing. In the recess 75 of the guide block 73, a plurality of split molds 77 for injection molding (the same number as the number of turbine blades 57) are provided so as to be able to expand and contract in the radial direction. The main molding surface 79 is opposite to the injection molding integral mold 67 and has a main molding surface 79 similar in shape to the inner shape of the turbine impeller main body 53 except for the rear surface of the turbine impeller main body 53, which is reversed to the final shape. ing. Here, when the movable frame 71 is moved in the left-right direction when the plurality of split molds 77 for injection molding are in a non-contact state with the integral mold 67 for injection molding, the plurality of split molds 77 are separated from the integral mold 67 for injection molding. When the movable frame 71 is moved in the left-right direction when it is in contact with the injection-molding integrated die 67, it is expanded and contracted in the radial direction. .

  When the injection molding die 63 is clamped, the cavity 81 is defined by the sub molding surface 69 of the injection molding integral mold 67 and the main molding surface 79 of the plurality of split molds for injection molding 77. In addition, a plurality of gates 83 are formed on the sub-molding surface 69 of the injection molding integrated mold 67, and a runner 85 communicating with the plurality of gates 83 is formed inside the injection molding integrated mold 67. The runner 85 can be connected to an injection nozzle 87 in the injection molding machine via a spool 89.

  A core 91 is set at the back (bottom) of the recess 75 of the guide block 73 so as to be positioned at the center of the cavity 81, and the core 91 is the last of the fitting hole 59 of the turbine wheel 55. It has an outer shape similar to the shape that reverses the shape.

  Then, the specific structure of the manufacturing method of the impeller which concerns on 2nd Embodiment is demonstrated.

  The impeller manufacturing method according to the second embodiment is a method for manufacturing the turbine impeller 27 according to the first embodiment, and includes an injection process, a degreasing process, and a sintering process. And the concrete content of each process is as follows.

(i) Injection Step As shown in FIG. 4, the movable frame 71 is moved rightward by driving an actuator (not shown) such as a hydraulic cylinder, so that a plurality of split molds 77 for injection molding are integrally moved rightward. And is brought into contact with the injection molding integrated die 67. Subsequently, by moving the movable frame 71 to the right with respect to the plurality of split molds 77 for injection molding by driving the actuator, the plurality of split molds 77 for injection molding are contracted and moved radially inward, and injection molding is performed. The mold 63 is clamped.

  After the clamping of the injection molding die 63 is completed, the spool 91, the runner 85, and the gate 83 are moved from the injection nozzle 87 in a state where the core 91 is set to be positioned at the center of the cavity 81 of the injection molding die 63. A mixture M of a heat-resistant metal powder (an example of a metal powder) and a molten binder is injected into the cavity 81 via the, and the binder is cured in the cavity 81. Thereby, the molded object 53F (refer FIG. 6) which is a shape similar to the final shape of the turbine impeller main body 53, and has the site | part 59F equivalent to a fitting hole in center part can be shape | molded. In addition, as a binder, what consists of multiple types of resin, such as a polystyrene and a polymethylmethacrylate, and waxes, such as paraffin wax, is used.

  After the binder is hardened in the cavity 81, the movable frame 71 is moved leftward with respect to the plurality of split molds 77 for injection molding by driving the actuator, so that the plurality of split molds 77 for injection molding are radially outward. Move to expand. Subsequently, by moving the movable frame 71 to the left by driving the actuator, the plurality of split molds 77 for injection molding are integrally moved to the left, and the mold for injection molding 63 is opened. And the molded object 53F is removed from the injection mold 63 by performing an appropriate mold release process.

(ii) Degreasing process (removal process)
After completion of the injection process, as shown in FIG. 5, the molded body 53 </ b> F is set at a predetermined position in the degreasing furnace 93 using a degreasing jig (not shown). Then, the molded body 53F is heated to a predetermined degreasing temperature by a heater (not shown) of the degreasing furnace 93 while keeping the inside of the degreasing furnace 93 in a nitrogen gas atmosphere. Thereby, the binder contained in the molded body 53F can be degreased (removed).

  Note that the method of degreasing the binder is not limited to the above-described heat degreasing, and other methods such as elution degreasing and solvent degreasing may be employed.

(iii) Sintering Step After the degreasing step, as shown in FIG. 6A, the compact 53F is set at a predetermined position in the sintering furnace 95 using a sintering furnace jig (not shown). At the same time, the cylindrical member 61 is inserted into a portion 59F corresponding to the fitting hole in the molded body 53F. The outer diameter of the cylindrical member 61 (in other words, the cross-sectional area of the cylindrical member 61) corresponds to the inner diameter of the portion 59F corresponding to the fitting hole in the molded body 53F (in other words, the fitting hole in the molded body 53F). Is smaller than the cross-sectional area of the portion 59F.

  Then, while the inside of the sintering furnace 95 is maintained in a vacuum atmosphere, the molded body is inserted by a heater (not shown) of the sintering furnace 95 in a state where the cylindrical member 61 is inserted into the portion 59F corresponding to the fitting hole in the molded body 53F. 53F is heated to a predetermined sintering temperature, and the compact 53F is fired and sintered. As a result, as shown in FIG. 6B, the compact 53 </ b> F is densified and thermally contracted to the final shape to produce a turbine impeller body 53 including the compact 53 </ b> F, and the compact 53 </ b> F is formed by the cylindrical member 61. The residual stress is generated in the central portion of the turbine wheel 55. The inner diameter of the fitting hole 59 of the turbine wheel 55 (in other words, the transverse area of the fitting hole 59 of the turbine wheel 55) is equal to the outer diameter of the cylindrical member 61 (in other words, the transverse area of the cylindrical member 61). It is the same.

  Thus, the turbine impeller 27 can be manufactured.

  Then, the effect | action and effect of 2nd Embodiment are demonstrated.

  In the sintering process, the molded body 53F is fired and sintered in a state in which the cylindrical member 61 is inserted into the portion 59F corresponding to the fitting hole in the molded body 53F, whereby the turbine impeller body 53 made of the molded body 53F is sintered. In addition to manufacturing, the thermal contraction of the molded body 53F is regulated by the cylindrical member 61, and residual stress is generated in the turbine wheel 55. Therefore, the rotational speed of the turbine impeller 27 decreases during operation of the vehicle supercharger 1. Even so, it is possible to reduce the decrease width of the centrifugal stress of the turbine wheel 55. Thereby, even if the fluctuation range of the rotation speed of the turbine impeller 27 increases, an increase in the stress amplitude of the turbine wheel 55 (the fluctuation range of the centrifugal stress) can be suppressed.

  Further, in the injection process, since the molded body 53F having the portion 59F corresponding to the fitting hole is formed in the central portion, the thickness of the portion 55F corresponding to the turbine wheel in the molded body 53F before sintering is reduced. can do.

  Therefore, according to 2nd Embodiment, there can exist an effect similar to 1st Embodiment.

  The present invention is not limited to the description of the above-described embodiment. For example, instead of forming a circular bottomless fitting hole 59 at the center of the turbine wheel 55, as shown in FIG. In addition, a circular bottomed fitting hole (hollow hole) 59 is formed, the technical idea applied to the turbine impeller 27 is applied to the compressor impeller 13, and other various embodiments. Is possible. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

DESCRIPTION OF SYMBOLS 1 Vehicle supercharger 3 Bearing housing 9 Rotor shaft 11 Compressor housing 13 Compressor impeller 15 Compressor wheel 17 Compressor blade 25 Compressor blade 25 Turbine housing 27 Turbine impeller 29 Variable nozzle unit 31 Nozzle ring 33 Mounting ring 35 Shroud ring 39 Variable nozzle 53 Turbine impeller body 53F molded body 55 turbine wheel 55F part 57 equivalent to turbine wheel 59 turbine blade 59 fitting hole 59F part equivalent to fitting hole 61 cylindrical member 63 injection mold 67 injection molding integral 69 sub molding surface 73 guide block 75 Indentation 77 Split mold for injection molding 79 Main molding surface 81 Cavity 91 Core 93 Degreasing furnace 95 Sintering furnace

Claims (4)

In impellers used for turbochargers,
A molded body formed by metal powder injection molding is sintered, and has an outer circumferential surface extending radially outward from the axial direction, and a circumferential interval between the outer circumferential surface of the wheel. A plurality of blades integrally formed, and an impeller body in which a circular fitting hole is formed along the axial direction in the center of the wheel;
The wheel is compressed and fitted into the fitting hole of the impeller body and inserted into a portion corresponding to the fitting hole in the molded body to regulate heat shrinkage during sintering of the molded body. An impeller comprising: a cylindrical member that generates residual stress. In the supercharger that supercharges the air supplied to the engine using the energy of the exhaust gas from the engine,
A supercharger comprising the impeller according to claim 1. In the manufacturing method of the impeller for manufacturing the impeller of Claim 1,
A mixture of metal powder and a binder in a cavity defined by the molding surface of the injection molding die, using an injection molding die having a molding surface similar to the shape that reverses the final shape of the impeller body Injection step of forming a molded body having a portion similar to the final shape and having a portion corresponding to the fitting hole at the center,
After the completion of the injection process, a degreasing process for degreasing the binder contained in the molded body,
After the degreasing step, the molded body is sintered to the final shape by firing and sintering the molded body in a state where the cylindrical member is inserted into a portion corresponding to the fitting hole in the molded body. A heat-shrinking step for producing the impeller body made of the molded body, and a sintering step for regulating the thermal shrinkage of the molded body by the cylindrical member and generating residual stress in the wheel. An impeller manufacturing method characterized by the above.   The injection step uses a core having an outer shape similar to the shape that inverts the fitting hole, and the core is set to be positioned at the center of the cavity of the injection mold The method for manufacturing an impeller according to claim 3, wherein the mixture is injected into the cavity of the injection mold.

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