JP2010275880A - Rotor assembly, supercharger, and method for manufacturing the rotor assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve productivity (manufacturability) of a rotor assembly 29 and work efficiency of manufacture of the rotor assembly 29 by shortening time required for manufacturing the rotor assembly 29. <P>SOLUTION: A turbine impeller 27 is formed by sintering a molding 27F molded by metal powder injection molding, and is formed with a cylindrical fitting hole 59 opened in the center of the back surface of a turbine wheel 55 and fitted around the left end of a rotor shaft 9. With the rotor shaft 9 inserted into a portion 59F corresponding to the fitting hole in the molding 27F, the turbine wheel 55 and rotor shaft 9 are bonded to each other by heat contraction occurring when the molding 27F is sintered. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rotor assembly and the like used for a supercharger.

  Various types of assemblies in which a plurality of parts are combined are used in a supercharger for a vehicle. A rotor assembly (rotor unit) as one of the assemblies is coaxial with a rotor shaft and an end of the rotor shaft. A turbine impeller (an example of an impeller) provided integrally therewith (see Patent Document 1). The turbine impeller is made of a molded body formed by precision casting, and a circular fitting hole that can be fitted to the end of the rotor shaft is formed in the center of the rear surface of the turbine impeller. . And in order to manufacture a rotor assembly, it carries out as follows.

  That is, a molded body having a portion corresponding to the fitting hole on the back surface is formed by precision casting. Next, machining is performed on the inner peripheral surface of the portion corresponding to the fitting hole in the molded body to finish the fitting hole in a predetermined size and shape, and the production of the turbine impeller is completed. Then, the end of the rotor shaft is fitted into the fitting hole of the turbine impeller, and the turbine impeller and the end of the rotor shaft are joined by electron beam welding. This completes the manufacture of the rotor assembly including the rotor shaft and the turbine impeller.

JP 2001-254627 A

  By the way, in order to ensure a sufficient rotational balance of the rotor assembly, it is necessary to increase the dimensional accuracy and shape accuracy of the fitting hole (the inner peripheral surface of the fitting hole) of the turbine impeller. On the other hand, a heat-resistant alloy such as Inconel used as a constituent material of a turbine impeller is a difficult-to-process material, and it is very troublesome to finish fitting holes with high dimensional accuracy and shape accuracy by machining. Therefore, it takes a lot of time for finishing by machining, the manufacturing time of a series of rotor assemblies becomes long, and it is difficult to improve the productivity (manufacturability) of the rotor assemblies and the workability of manufacturing the rotor assemblies. There is a problem.

  Accordingly, an object of the present invention is to provide a rotor assembly having a novel configuration that can solve the above-described problems.

  A first feature of the present invention is that, in a rotor assembly (rotor unit) used in a supercharger, a rotor shaft and an end portion of the rotor shaft are integrally provided coaxially and molded by metal powder injection molding. And an impeller formed with a circular fitting hole that can be fitted to the end of the rotor shaft at the center of the back surface, and the fitting in the molded body. The gist is that the impeller and the rotor shaft are joined by thermal contraction during sintering of the molded body in a state where the end of the rotor shaft is inserted into a portion corresponding to the joint hole. .

  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.

  According to the first feature, since the impeller is formed by sintering the molded body formed by metal powder injection molding, in other words, a metal superior in dimensional accuracy and shape accuracy compared to precision casting. Since the impeller is manufactured by a powder injection molding method, the dimensional accuracy and shape accuracy of the fitting hole of the impeller can be sufficiently increased without machining the molded body after sintering.

  Further, the impeller and the rotor shaft are joined by thermal contraction during sintering of the molded body in a state where the end of the rotor shaft is inserted into a portion corresponding to the fitting hole in the molded body. Therefore, the impeller and the rotor shaft are not joined separately after the production of the impeller is completed, but the impeller and the rotor shaft are joined simultaneously with the production of the impeller. it can.

  According to a second aspect of the present invention, in the supercharger that supercharges the air supplied to the engine using the energy of the exhaust gas from the engine, the rotor assembly having the first characteristic is provided. The gist.

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

  A third feature of the present invention is an injection molding method having a molding surface similar to a shape (complementary shape) that reverses the final shape of the impeller in the manufacturing method for manufacturing the impeller according to the first feature. A metal mold and a binder are injected into a cavity defined by the molding surface of the injection mold, and the shape is similar to the final shape and the center of the back is An injection process for molding the molded body having a portion corresponding to a fitting hole, a degreasing process for degreasing the binder contained in the molded body after the completion of the injection process, and after the degreasing process, In a state where the end of the rotor shaft is inserted into a portion corresponding to the fitting hole in the molded body, the molded body is fired and sintered to thermally shrink the molded body to the final shape. , Together to produce said impeller comprising a serial moldings, and gist that and a sintering step of joining the rotor shaft and the impeller by the heat shrinkage of the green body.

  According to the third feature, since the impeller is manufactured through the injection process, the degreasing process, and the sintering process, in other words, a metal that is superior in dimensional accuracy and shape accuracy compared to precision casting. Since the impeller is manufactured by a powder injection molding method, the dimensional accuracy and shape accuracy of the fitting hole of the impeller can be sufficiently increased without machining the molded body after sintering.

  In addition to producing the impeller by firing and sintering the molded body in a state where the end of the rotor shaft is inserted into a portion corresponding to the fitting hole in the molded body, Since the impeller and the rotor shaft are joined by thermal contraction of the molded body, the impeller and the rotor shaft are joined instead of separately performing the joining process of the impeller and the rotor shaft after the production of the impeller is completed. The treatment can be performed simultaneously with the production of the impeller.

  According to the present invention, the dimensional accuracy and shape accuracy of the fitting hole of the impeller can be sufficiently increased without performing finishing by machining, and the impeller and the rotor shaft can be joined by the impeller. The time required for manufacturing the rotor assembly can be shortened to improve the productivity (manufacturability) of the rotor assembly and the workability of manufacturing the rotor assembly. it can.

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. 4A is an enlarged view of the arrow IVA in FIG. 3, and FIG. 4B is a cross-sectional view taken along line IVB-IVB in FIG. 4A. It is sectional drawing of the turbine impeller which concerns on the modification of 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 a figure explaining the injection process in the manufacturing method of the impeller which concerns on the modification of 2nd Embodiment.

[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 the right end portion of the rotor shaft 9 is located in the compressor housing 11, and centrifugal force is used for the right end portion of the rotor shaft 9. A compressor impeller 13 for compressing air is integrally provided. The specific components of the compressor impeller 13 will be described. A compressor wheel 15 is coaxially and integrally provided at the right end of the rotor shaft 9, and the compressor wheel 15 is an axial center of the compressor impeller 13. (In other words, the axis of the compressor wheel 15 or the axis of the rotor shaft 9) can be rotated around 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 the left end portion of the rotor shaft 9 is located in the turbine housing 25. The left end portion of the rotor shaft 9 has pressure energy of exhaust gas. A turbine impeller 27 that generates a rotational force (rotational torque) using the above is integrally provided on the same axis. Here, the rotor shaft 9 and the turbine impeller 27 constitute a rotor assembly (rotor unit) 29. Specific components of the rotor assembly 29 will be described later.

  A variable nozzle unit 31 is provided in the turbine housing 25 so as to surround the turbine impeller 27. The specific components of the variable nozzle unit 31 will be described. A nozzle ring 33 is provided on the radially outer side of the turbine impeller 27 in the turbine housing 25 via a mounting ring 35. The shroud ring 37 is provided integrally with a plurality of (only one shown) connecting pins 39 and spaced apart from each other on the left and right. A plurality of variable nozzles 41 are provided between the nozzle ring 33 and the shroud ring 37 at intervals in the circumferential direction, and each variable nozzle 41 has an axis parallel to the axis C of the turbine impeller 27. The nozzle shafts 43 of the plurality of variable nozzles 41 are interlocked and connected by a synchronization mechanism 45 as shown in Patent Document 1, which can rotate around the center (can swing).

  A transmission shaft 47 is rotatably provided at the lower left portion of the bearing housing 3, and a right end portion of the transmission shaft 47 is an actuator such as a cylinder that rotates a plurality of variable nozzles 41 in synchronization. (Not shown) is connected (linked and linked) via a connection lever 49, and the left end portion of the transmission shaft 47 is connected to the synchronization mechanism 45.

  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. In addition, a turbine scroll passage 51 is formed inside the turbine housing 25 so as to surround the turbine impeller 27. The turbine scroll passage 51 communicates with a gas intake port to collect exhaust gas. It is possible to enter. Further, a gas discharge port 53 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). 53 communicates with the turbine scroll passage 51 and can be connected to an exhaust gas purification device (not shown) via a connecting pipe (not shown).

  Next, a specific configuration of the rotor assembly 29 that is a main part of the first embodiment will be described.

  As shown in FIG. 3, the rotor assembly 29 includes the rotor shaft 9 extending in the left-right direction and the turbine impeller 27 provided integrally on the left end portion of the rotor shaft 9 coaxially as described above. ing. The turbine impeller 27 is formed by sintering a molded body 27F (see FIGS. 7 and 8A) formed by metal powder injection molding, and includes an injection process, a degreasing process, and a sintering process described later. It is manufactured through a process. The turbine impeller 27 includes a turbine wheel 55 that is integrally provided at the left end portion of the rotor shaft 9, and the turbine wheel 55 is an axis of the turbine impeller 27 (in other words, the axis of the turbine wheel 55). The center or the axis of the rotor shaft 9) can be rotated around C). Further, the outer peripheral surface of the turbine wheel 55 extends radially outward from the axial direction of the turbine impeller 27 (turbine wheel 55). 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 37. It extends like so.

  A circular fitting hole 59 that can be fitted to the left end portion of the rotor shaft 9 is formed at the center of the rear surface of the turbine wheel 55. The turbine wheel 55 and the rotor shaft 9 are joined by thermal contraction during sintering of the molded body 27F in a state where the rotor shaft 9 is inserted into a portion 59F corresponding to a fitting hole in the molded body 27F. It has become.

  An outer flange 61 (an example of an outer protrusion) that protrudes radially outward is formed on the periphery of the left end portion of the rotor shaft 9, and the periphery of the fitting hole 59 of the turbine wheel 55 is radially inward. A protruding inner flange 63 (an example of an inner protruding portion) is formed, and the inner flange 63 of the turbine wheel 55 is locked to the outer flange 61 of the rotor shaft 9 by heat shrinkage during sintering of the molded body 27F. It is like that. A groove 65 extending in the axial direction of the rotor shaft 9 is formed on the outer peripheral surface of the left end portion of the rotor shaft 9 so as to cross the outer flange 61, and the inner periphery of the fitting hole 59 of the turbine wheel 55. On the surface, a protrusion 67 that engages with the groove 65 is formed by heat shrinkage during sintering of the molded body 27F.

  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 51 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 region), the actuator is rotated in synchronization with the direction in which the plurality of variable nozzles 41 are throttled, whereby the turbine 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 41 are rotated by the actuator in synchronization with the opening direction. The throat area of 41 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 turbine wheel 55 is formed by sintering a molded body 27F formed by metal powder injection molding. Since the turbine impeller 27 is manufactured by a metal powder injection molding method that is superior in dimensional accuracy and shape accuracy, the fitting hole 59 of the turbine wheel 55 is not machined on the sintered compact 27F. The dimensional accuracy and shape accuracy can be sufficiently increased.

  Further, the turbine wheel 55 and the rotor shaft 9 are joined by heat shrinkage during sintering of the molded body 27F in a state where the left end portion of the rotor shaft 9 is inserted into the portion 59F corresponding to the fitting hole in the molded body 27F. Therefore, the process of joining the turbine wheel 55 and the rotor shaft 9 is not performed separately after the production of the turbine impeller 27 is completed, but the process of joining the turbine wheel 55 and the rotor shaft 9 is performed to produce the turbine impeller 27. It can be done simultaneously. Further, the inner flange 63 of the turbine wheel 55 is locked to the outer flange 61 of the rotor shaft 9 by thermal contraction during the sintering of the molded body 27F, and the protrusion 67 of the turbine wheel 55 is heated during the sintering of the molded body 27F. Since the engagement with the groove 65 is caused by the contraction, the turbine wheel 55 can be prevented from coming off / rotating with respect to the rotor shaft 9 simultaneously with the production of the turbine impeller 27 (the vehicle supercharger 1 (the rotor assembly 29). ) Unique action).

  Therefore, according to the first embodiment, the dimensional accuracy and shape accuracy of the fitting hole 59 of the turbine impeller 27 can be sufficiently increased without performing finishing by machining, and the turbine wheel 55 and the rotor shaft 9 And the turbine wheel 55 with respect to the rotor shaft 9 can be prevented from coming off / rotating simultaneously with the manufacture of the turbine impeller 27, so that the time required for manufacturing the rotor assembly 29 can be shortened. The productivity (manufacturability) of the assembly 29 and the workability of manufacturing the rotor assembly 29 can be improved.

(Modification of the first embodiment)
A rotor unit according to a modification of the first embodiment will be described with reference to FIG. In the drawings, “L” indicates the left direction and “R” indicates the right direction.

  As shown in FIG. 5, the rotor assembly 29A according to the modification of the first embodiment differs from the rotor assembly 29 according to the first embodiment in the axial direction (turbine A circular hollow 69 extending in the axial direction of the impeller 27 is formed.

  The rotor assembly 29A according to the modified example of the first embodiment is substantially the same as the rotor assembly 29 according to the first embodiment, except that a hollow hole 69 is formed at the center of the front end surface of the turbine wheel 55. It has the same configuration.

  According to the modification of the first embodiment, in addition to the effects of the first embodiment described above, a circular hollow 69 extending in the axial direction is formed at the center of the tip surface of the turbine wheel 55. In other words, since the green body before sintering (not shown, see the green body 27F according to the first embodiment) has a portion corresponding to the hollow hole in the center of the tip surface, It is possible to reduce the thickness of the portion corresponding to the turbine wheel in the molded body.

  Therefore, according to the modification of the first embodiment, in addition to the effects of the first embodiment described above, it is possible to reduce the thickness of the portion corresponding to the turbine wheel in the molded body before sintering. When the body is sintered, it is possible to suppress the occurrence of defects such as a nest in a portion corresponding to the turbine hole in the formed body, and to stably manufacture the turbine impeller 27.

[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. 6, an injection mold 71 according to the second embodiment is used for carrying out the method for manufacturing a rotor assembly according to the second embodiment, and is an injection molding according to the second embodiment. The specific configuration of the working mold 71 is as follows.

  That is, an injection molding integrated mold 75 is detachably provided on the left side of the fixed frame 73 in the injection molding machine, and this injection molding integrated mold 75 is mounted on the left side of the rear surface of the turbine impeller 27 (the turbine wheel 55). The sub-molding surface 77 has a shape similar to the shape (complementary shape) that inverts the final shape of the rear surface. A guide block 81 is detachably provided on the right side of the movable frame 79 movable in the left-right direction in the injection molding machine, and a truncated cone-shaped recess 83 is formed on the right side of the guide block 81. ing. In the recess 83 of the guide block 81, a plurality of split molds 85 for injection molding (the same number as the number of the turbine blades 57) are provided so as to be able to expand and contract in the radial direction. The main molding surface 87 is similar to a shape that is opposite to the final shape of the turbine impeller 27 excluding the rear surface of the turbine impeller 27 and that is opposite to the injection molding integral mold 75. . Here, when the plurality of split molds 85 for injection molding are in a non-contact state with the integral mold 75 for injection molding, the movable frame 79 is moved away from the integral mold 75 for injection molding when moved in the left-right direction. When the movable frame 79 is moved in the left-right direction when it is in contact with the injection molding integrated mold 75, it is expanded and contracted in the radial direction. .

  When the mold for injection molding 71 is clamped, the cavity 89 is defined by the sub molding surface 77 of the injection molding integral mold 75 and the main molding surface 87 of the plurality of split molds for injection molding 85. A plurality of gates 91 are formed on the sub-molding surface 77 of the injection molding integrated mold 75, and a runner 93 communicating with the plurality of gates 91 is formed inside the injection molding integrated mold 75. The runner 93 can be connected to an injection nozzle 95 in the injection molding machine via a spool 97.

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

  The rotor assembly manufacturing method according to the second embodiment is a method for manufacturing the rotor assembly 29 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. 6, the movable frame 79 is moved rightward by driving an actuator (not shown) such as a hydraulic cylinder, so that a plurality of divided molds 85 for injection molding are integrally moved rightward. And is brought into contact with the integral mold 75 for injection molding. Subsequently, by moving the movable frame 79 to the right with respect to the plurality of split molds 85 for injection molding by driving the actuator, the plurality of split molds 85 for injection molding are contracted and moved radially inward to perform injection molding. The mold 71 is clamped.

  After the clamping of the injection molding die 71 is completed, the mixture M of the heat-resistant metal powder (an example of the metal powder) and the molten binder M enters the cavity 89 from the injection nozzle 95 through the spool 97, the runner 93, and the gate 91. Is injected to cure the binder in the cavity 89. Thus, a molded body 27F (see FIG. 7) that has a shape similar to the final shape of the turbine impeller 27 and that has a portion 59F corresponding to the fitting hole at the center of the back surface can be formed. 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 89, the movable frame 79 is moved leftward with respect to the plurality of injection molding divided molds 85 by driving the actuator, so that the plurality of injection molding divided molds 85 are radially outward. Move to expand. Subsequently, by moving the movable frame 79 to the left by driving the actuator, the plurality of split molds 85 for injection molding are integrally moved to the left to open the mold for injection molding 71. And the molded object 27F is removed from the injection mold 71 by performing an appropriate mold release process.

(ii) Degreasing process (removal process)
After completion of the injection process, as shown in FIG. 7, the compact 27 </ b> F is set at a predetermined position of the degreasing furnace 99 using a degreasing jig (not shown). And while maintaining the inside of the degreasing furnace 99 in a nitrogen gas atmosphere, the molded body 27F is heated to a predetermined degreasing temperature by a heater (not shown) of the degreasing furnace 99. Thereby, the binder contained in the compact 27F 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. 8A, the compact 27F is set at a predetermined position in the sintering furnace 101 using a sintering furnace jig (not shown). At the same time, the end portion (left end portion) of the rotor shaft 9 is inserted into a portion 59F corresponding to the fitting hole in the molded body 27F. Note that the outer diameter of the outer flange 61 of the rotor shaft 9 (in other words, the area of the end surface of the rotor shaft 9) is equal to the inner diameter of the portion 59F corresponding to the fitting hole in the molded body 27F and the inner flange of the molded body 27F. The inner diameter of the corresponding portion 63F (in other words, the cross-sectional area of the portion 59F corresponding to the fitting hole in the molded body 27F and the cross-sectional area inside the portion 63F corresponding to the inner flange in the molded body 27F) is smaller. is there.

  Then, while maintaining the inside of the sintering furnace 101 in a vacuum atmosphere, the heater (not shown) of the sintering furnace 101 is inserted with the end of the rotor shaft 9 inserted into the portion 59F corresponding to the fitting hole in the compact 27F. ) To heat the molded body 27F to a predetermined sintering temperature, and fire and sinter the molded body 27F. As a result, as shown in FIG. 8 (b), the compact 27F can be densified and thermally contracted to the final shape to produce the turbine impeller 27 made of the compact 27F, and the heat of the compact 27F can be produced. With the contraction, the inner flange 63 of the turbine wheel 55 is locked to the outer flange 61 of the rotor shaft 9 and the protrusion 67 of the turbine wheel 55 is engaged with the groove 65 of the rotor shaft 9. 9 can be joined. The inner diameter of the inner flange 63 of the turbine wheel 55 (in other words, the cross-sectional area inside the inner flange 63 of the turbine wheel 55) is the outer diameter of the outer flange 61 of the rotor shaft 9 (in other words, the rotor shaft 9). The inner diameter of the fitting hole 59 of the turbine wheel 55 (in other words, the cross-sectional area of the fitting hole 59 of the turbine wheel 55) is smaller than the outer diameter of the outer flange 61 of the rotor shaft 9 (in other words, the area of the end face). For example, the area of the end surface of the rotor shaft 9 is the same.

  As described above, the rotor assembly 29 including the rotor shaft 9 and the turbine impeller 27 can be manufactured.

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

  Since the turbine impeller 27 is manufactured through an injection process, a degreasing process, and a sintering process, in other words, the turbine impeller 27 is formed by a metal powder injection molding method that has superior dimensional accuracy and shape accuracy compared to precision casting. Since it is manufactured, the dimensional accuracy and shape accuracy of the fitting hole 59 of the turbine impeller 27 can be sufficiently increased without performing machining on the sintered compact 27F.

  In addition to producing the turbine impeller 27 by firing and sintering the molded body 27F in a state where the end of the rotor shaft 9 is inserted into the portion 59F corresponding to the fitting hole in the molded body 27F, In a state where the inner flange 63 of the turbine wheel 55 is engaged with the outer flange 61 of the rotor shaft 9 and the protrusion 67 of the turbine wheel 55 is engaged with the groove 65 of the rotor shaft 9 due to the heat shrinkage of the compact 27F. In order to join the wheel 55 and the rotor shaft 9, the joining process between the turbine impeller 27 and the rotor shaft 9 and the retaining / rotating prevention process of the turbine wheel 55 with respect to the rotor shaft 9 are performed simultaneously with the production of the turbine impeller 27. be able to.

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

(Modification of the second embodiment)
A method for manufacturing a rotor assembly according to a modification of the second embodiment will be described with reference to FIG. In the drawings, “L” indicates the left direction and “R” indicates the right direction.

  As shown in FIG. 9, the method for manufacturing the rotor assembly according to the modification of the second embodiment is a method for manufacturing the rotor assembly 29A according to the modification of the first embodiment. In the injection process according to the modified example of the second embodiment, the core 103 having an outer surface similar to the shape that reverses the final shape of the hollow hole 69 of the turbine wheel 55 in the rotor assembly 29A is used. In a state where the core 103 is set so as to be positioned at the center of the cavity 89 of the injection mold 71, a mixture M of the heat-resistant metal powder and the molten binder is injected into the cavity 89, and the cavity 89 is injected. Cure the binder. As a result, a molded body (not shown in the figure, see the molded body 27F according to the first embodiment) having a portion corresponding to the hollow hole at the center of the tip surface is molded.

  The rotor assembly manufacturing method according to the modification of the second embodiment has substantially the same configuration as the rotor assembly manufacturing method according to the second embodiment, except that the core 103 is used.

  According to the modification of the second embodiment, in addition to the effects of the first embodiment described above, in the injection process, a molded body F having a portion corresponding to a hollow hole is formed in the center of the tip surface. Therefore, it is possible to reduce the thickness of the portion corresponding to the turbine wheel in the green body before sintering.

  Therefore, according to the modification of the second embodiment, the same effect as that of the modification of the first embodiment can be obtained.

  The present invention is not limited to the description of the above-described embodiment. For example, the technical idea applied to the rotor assembly including the rotor shaft 9 and the turbine impeller 27 includes the rotor shaft 9 and the compressor impeller 13. The present invention can be implemented in various other modes such as application to a rotor assembly. 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 impeller 15 Compressor wheel 17 Compressor blade 25 Turbine housing 27 Turbine impeller 27F Forming body 29 Rotor assembly 29A Rotor assembly 31 Variable nozzle unit 41 Variable nozzle 55 Turbine wheel 57 Turbine blade 59 Fitting hole 59F Site corresponding to fitting hole 61 Outer flange 63 Inner flange 65 Groove 67 Protrusion 69 Hole 71 Injection molding die 75 Injection molding integral 77 Sub molding surface 81 Guide block 83 Recess 85 Injection molding Split mold 87 Main molding surface 89 Cavity 99 Degreasing furnace 101 Sintering furnace 103 Core

Claims (6)

In a rotor assembly used for a supercharger,
A rotor shaft;
The end of the rotor shaft is integrally provided on the same axis and is formed by sintering a molded body formed by metal powder injection molding, and is fitted with the end of the rotor shaft at the center of the back An impeller formed with a possible circular fitting hole, and
The impeller and the rotor shaft are joined by thermal contraction during sintering of the molded body with the end of the rotor shaft inserted into a portion corresponding to the fitting hole in the molded body. A rotor assembly characterized by comprising: A groove extending in the axial direction is formed on the outer peripheral surface of the end portion of the rotor shaft,
2. The rotor assembly according to claim 1, wherein a protrusion that engages with the groove is formed on an inner peripheral surface of the fitting hole of the impeller by heat shrinkage during sintering of the molded body.   An outer projecting portion projecting radially outward is formed on the periphery of the end of the rotor shaft, and projecting radially inward on the periphery of the fitting hole of the impeller and heat shrinkage during sintering of the molded body The rotor assembly according to claim 2, wherein an inner projecting portion that engages with the outer projecting portion of the rotor shaft is formed.   The rotor assembly according to any one of claims 1 to 3, wherein a circular hollow extending in the axial direction is formed in a front end surface of the impeller. 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 rotor assembly according to any one of claims 1 to 4. A manufacturing method for manufacturing a rotor assembly according to claim 1,
Using an injection mold having a molding surface similar to the shape that reverses the final shape of the impeller, a mixture of metal powder and binder is placed in a cavity defined by the molding surface of the injection mold. An injection step of molding the molded body having a portion similar to the final shape and having a portion corresponding to the fitting hole at the center of the back surface by injection,
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 fired and sintered in a state where the end portion of the rotor shaft is inserted into a portion corresponding to the fitting hole in the molded body. And heat-shrinking to the final shape to produce the impeller made of the molded body, and further comprising a sintering step of joining the impeller and the rotor shaft by thermal shrinkage of the molded body. A method for manufacturing a rotor assembly.

Images