JP2010270644A - Impeller, supercharger, and method for manufacturing impeller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably manufacture a turbine impeller 27 by inhibiting occurrence of a defect such as a blowhole at a section 53F corresponding to a turbine hole of a formed body 27F when the formed body 27F is sintered. <P>SOLUTION: The turbine impeller 27 is provided by sintering a mold body 27F molded by metal powder injection molding. An extraction hole 57 of round shape extended in an axial direction is formed at a center part of a distal end surface of a turbine wheel 53. A bottom part of the extraction hole 57 is positioned at a back surface side of the turbine wheel 53 of a base end 55e of an outer edge of turbine blades 55. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  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. .

  Therefore, the pressure energy of the exhaust gas is utilized by circulating the exhaust gas taken into the turbine housing from the inlet side of the turbine impeller to the outlet side (from the upstream side to the downstream side of the turbine impeller when viewed from the exhaust gas flow direction). Thus, a rotational force can be generated to rotate the rotor shaft integrally with the turbine impeller.

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

  By the way, in recent years, the metal powder injection molding method (MIM method), which enables the production of high-dimensional accuracy and high-strength products (molded bodies), is the fifth generation precision following machining, die casting, powder metallurgy, and precision casting. It is attracting attention as a processing technology.

  However, when a turbine impeller formed by sintering a molded body formed by metal powder injection molding is actually manufactured, the following problems occur. That is, since the binder contained in the molded body is degreased (removed) before the molded body is sintered, defects such as nests are present in the portion corresponding to the turbine wheel in the molded body when the molded body is sintered. There is a problem that it is likely to cause a manufacturing defect of the turbine impeller.

  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 the axial direction (the axial direction of the impeller, in other words, at the center of the wheel) The gist is that a circular hollow hole extending in the axial direction of the wheel is formed.

  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 a first feature, the impeller is formed by sintering the molded body formed by metal powder injection molding, and the circular hollow extending in the axial direction is formed in the center of the wheel. In other words, since the formed body before sintering has a portion corresponding to the hollow hole at the center, the portion corresponding to the wheel in the formed body before sintering. Can be made thinner.

  A second feature of the present invention is that a supercharger that supercharges air supplied to the engine using energy of exhaust gas from the engine includes the impeller having the first feature. And

  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 is An injection process for forming the molded body having a portion corresponding to a hollow hole, a degreasing process (removing process) for degreasing (removing) the binder contained in the molded body after the completion of the injection process, The gist of the present invention is to include a sintering step in which the molded body is thermally contracted to the final shape by firing and sintering the molded body after the degreasing step.

  According to the third feature, in the injection step, since the molded body having a portion corresponding to the hollow hole is formed at the center, the portion corresponding to the wheel in the molded body before sintering. Can be made thinner.

  According to the present invention, it is possible to realize the thinning of the portion corresponding to the wheel in the molded body before sintering, and therefore the portion corresponding to the hole in the molded body during the sintering of the molded body. The impeller can be stably manufactured while suppressing the occurrence of defects such as nests.

  For the same reason, the impeller can be reduced in weight, the inertia moment of the impeller can be reduced, and the responsiveness of the impeller (transient response) can be improved.

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 sectional drawing of the turbine impeller of another aspect 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.

[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 is formed by sintering a molded body 27 </ b> F (see FIGS. 6 and 7) molded by metal powder injection molding. It is manufactured through a sintering process.

  The turbine impeller 27 includes a turbine wheel 53 provided in the turbine housing 25, and this turbine wheel 53 is integrally connected to the left end portion of the rotor shaft 9, and the axis of the turbine impeller 27 ( In other words, the rotor shaft 9 can rotate around the axis C). Further, the outer peripheral surface of the turbine wheel 53 extends from the axial direction of the turbine impeller 27 (turbine wheel 53) toward the radially outer side. Further, a plurality of turbine blades 55 are integrally formed on the outer peripheral surface of the turbine wheel 53 at intervals in the circumferential direction, and the outer edge of each turbine blade 55 is along the shroud (inner wall surface) of the shroud ring 35. It extends like so.

  A bottomed circular hollow 57 extending in the axial direction (the axial direction of the turbine impeller 27) is formed at the center of the front end surface of the turbine wheel 53. The inner diameter of the hollow 57 is axial. Is the same along. Further, the bottom (back) of the hollow hole 57 has a hemispherical shape and is located on the back side (right side) of the turbine wheel 53 with respect to the base end 55 e of the outer edge of the turbine blade 55. Instead of making the inner diameter of the hollow hole 57 the same along the axial direction, the diameter may be gradually reduced toward the rear side of the turbine wheel 53 as shown in FIG. Instead of making the hollow hole 57 with a bottom, as shown in FIG. 4B, a bottomless through hole may be used.

  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 turbine impeller 27 is formed by sintering a molded body 27F formed by metal powder injection molding. Since the circular hollow 57 extending in the axial direction is formed in the central portion, in other words, the molded body 27F before sintering has a portion 57F (FIG. 6) corresponding to the hollow in the central portion of the tip surface. Therefore, it is possible to reduce the thickness of the portion 53F (see FIGS. 6 and 7) corresponding to the turbine wheel in the compact 27F before sintering (see FIG. 7). 1 (specific action by the turbine impeller 27)).

  Therefore, according to the vehicle supercharger 1 (turbine impeller 27) according to the first embodiment, it is possible to reduce the thickness of the portion 53F corresponding to the turbine wheel in the molded body before sintering. During the sintering of 27F, the occurrence of defects such as nests in the portion 53F corresponding to the turbine hole in the compact 27F can be suppressed, and the turbine impeller 27 can be stably manufactured.

  For the same reason, the turbine impeller 27 can be reduced in weight, the moment of inertia of the turbine impeller 27 can be reduced, and the responsiveness (transient response) of the turbine impeller 27 can be improved.

[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. 5, an injection mold 59 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 59 is as follows.

  That is, an injection molding integral 63 is detachably provided on the left side of the fixed frame 61 in the injection molding machine. The injection molding integral 63 is disposed on the left side of the rear surface of the turbine impeller 27 (the turbine wheel 53). The sub-molding surface 65 has a shape similar to the shape (complementary shape) that reverses the final shape of the rear surface. A guide block 69 is detachably provided on the right side of the movable frame 67 movable in the left-right direction in the injection molding machine, and a truncated cone-shaped recess 71 is formed on the right side of the guide block 69. ing. A plurality of (in the same number as the number of turbine blades 55) injection-molding split dies 73 are provided in the recess 71 of the guide block 69 so as to be able to expand and contract in the radial direction. The main molding surface 75 is similar to the shape that is opposite to the final shape of the turbine impeller 27 excluding the back surface of the turbine impeller 27 and that is opposite to the injection molding integrated die 63. . Here, when the movable frame 67 is moved in the left-right direction when the plurality of split molds 73 for injection molding are in a non-contact state with the integral mold for injection molding 63, the plurality of split molds for injection molding approach and separate from the integral mold for injection molding 63. When the movable frame 67 is moved in the left-right direction when it is in contact with the injection molding integrated die 63, it expands and contracts in the radial direction. .

  When the injection molding die 59 is clamped, the cavity 77 is defined by the sub molding surface 65 of the injection molding integral die 63 and the main molding surface 75 of the plurality of split molds for injection molding 73. Further, a gate 79 is formed on the sub-molding surface 65 of the injection molding integral 63, and a runner 81 communicating with the gate 79 is formed inside the injection molding integral 63. The runner 81 can be connected to an injection nozzle 83 in the injection molding machine via a spool 85.

  A core 87 is set at the back (bottom) of the recess 71 of the guide block 69 so as to be positioned at the center of the cavity 77, and the core 87 reverses the final shape of the hollow hole 57. It has a similar external shape to 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. 5, the movable frame 67 is moved rightward by driving an actuator (not shown) such as a hydraulic cylinder, so that a plurality of split molds 73 for injection molding are integrally moved rightward. And is brought into contact with the integral mold 63 for injection molding. Subsequently, by moving the movable frame 67 to the right with respect to the plurality of split molds for injection molding 73 by driving the actuator, the plurality of split molds for injection molding 73 are contracted and moved inward in the radial direction. The mold 59 is clamped.

  After the clamping of the injection mold 59 is completed, the spool 87, the runner 81, and the gate 79 are moved from the injection nozzle 83 in a state where the core 87 is set to be positioned at the center of the cavity 77 of the injection mold 59. The mixture M of the heat-resistant metal powder (an example of the metal powder) and the molten binder is injected into the cavity 77 via, and the binder is cured in the cavity 77. As a result, a molded body 27F (see FIG. 6) that is similar to the final shape of the turbine impeller 27 and that has a portion 57F that corresponds to a hollow hole in the center of the tip 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 77, the movable frame 67 is moved to the left with respect to the plurality of split molds for injection molding 73 by driving the actuator, so that the plurality of split molds for injection molding 73 are radially outward. Move to expand. Subsequently, by moving the movable frame 67 to the left by driving the actuator, the plurality of split molds for injection molding 73 are integrally moved to the left, and the mold for injection molding 59 is opened. And the molded object 27F is removed from the injection mold 59 by performing an appropriate mold release process.

(ii) Degreasing process (removal process)
After completion of the injection process, as shown in FIG. 6, the compact 27 </ b> F is set at a predetermined position of the degreasing furnace 89 using a degreasing jig (not shown). And while maintaining the inside of the degreasing furnace 89 in the nitrogen gas atmosphere, the molded body 27F is heated to a predetermined degreasing temperature by a heater (not shown) of the degreasing furnace 89. 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, the compact 27F is set at a predetermined position of the sintering furnace 91 using a sintering furnace jig (not shown) as shown in FIG. Then, while maintaining the inside of the sintering furnace 91 in a vacuum atmosphere, the molded body 27F is heated to a predetermined sintering temperature by a heater (not shown) of the sintering furnace 91, and the molded body 27F is fired and sintered. . Thereby, the compact 27F is densified and thermally contracted to the final shape.

  As described above, the turbine impeller 27 obtained by sintering the compact 27F formed by metal powder injection molding can be manufactured.

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

  In the injection process, since the molded body 27F having the portion 57F corresponding to the hollow hole is formed at the center of the tip surface, the portion 53F corresponding to the turbine wheel in the molded body 27F before sintering is thinned. Can be realized.

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

  Note that the present invention is not limited to the description of the above-described embodiment, and can be implemented in various other modes, for example, the technical idea applied to the turbine impeller 27 is applied to the compressor impeller 13. 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 Molded body 29 Variable nozzle unit 53 Turbine wheel 53F Parts 55 equivalent to turbine wheel Turbine blade 55e Base edge 57 of outer edge 57 Hole 59F Corresponding to the hole 59 Injection mold 63 Injection molding integral 65 Sub molding surface 69 Guide block 73 Injection molding split mold 75 Main molding surface 77 Cavity 87 Child 89 Degreasing furnace 91 Sintering furnace

Claims (5)

In impellers used for turbochargers,
Sintered compact molded by metal powder injection molding,
A wheel whose outer peripheral surface extends radially outward from the axial direction;
A plurality of blades integrally formed on the outer peripheral surface of the wheel at intervals in the circumferential direction,
An impeller characterized in that a circular hollow extending in the axial direction is formed in the center of the wheel.   2. The impeller according to claim 1, wherein a bottom portion of the hollow hole is located on a back side of the wheel with respect to a base end of an outer edge of the blade. 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 or 2. In the manufacturing method for manufacturing the impeller of Claim 1,
A mixture of a 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 a shape reversing the final shape of the impeller An injection step of forming the molded body having a portion similar to the final shape and having a portion corresponding to the hollow hole in the central portion by injecting
After the completion of the injection process, a degreasing process for degreasing the binder contained in the molded body,
An impeller manufacturing method comprising: a sintering step of thermally shrinking the molded body to the final shape by firing and sintering the molded body after completion of the degreasing step.   The injection step uses a core having an outer shape similar to the shape that reverses the final shape of the hollow hole so that the core is positioned at the center of the cavity of the injection mold. The impeller manufacturing method according to claim 4, wherein the mixture is injected into the cavity of the injection mold in a set state.

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