WO2010137609A1

WO2010137609A1 - Impeller applied to supercharger and method of manufacturing same

Info

Publication number: WO2010137609A1
Application number: PCT/JP2010/058878
Authority: WO
Inventors: 智裕井上; 高橋　幸雄; 松山　良満
Original assignee: 株式会社Ihi
Priority date: 2009-05-26
Filing date: 2010-05-26
Publication date: 2010-12-02
Also published as: JP2010275880A

Abstract

A rotor assembly used for a supercharger and rotating about the axis, comprising: a rotary shaft extending along the axis and configured to transmit torque; and an impeller molded as a single body by sintering and having a recess which is engaged with the rotary shaft by means of pressure-fitting by contraction in the sintering operation.

Description

Impeller applied to supercharger and method for manufacturing the same

The present invention relates to an impeller applied to a supercharger and a manufacturing method thereof.

∙ Superchargers are often used for the purpose of sending more air into an internal combustion engine. The supercharger includes a compressor impeller, and the compressor impeller is driven to pressurize and supply air to the engine. A turbocharger of a type called a turbocharger includes a turbine impeller that receives engine exhaust, and energy taken out from the exhaust by the turbine impeller drives a compressor impeller. On the other hand, in a supercharger in a narrow sense, an engine crankshaft is connected to a compressor impeller and drives it.

Since the turbine impeller is exposed to high-temperature exhaust, it must withstand high heat of, for example, about 800 ° C. Therefore, the design and manufacture of a turbine impeller is more difficult than the compressor impeller in terms of material, structure, and manufacturing method, and requires advanced technology. For example, the coupling between the compressor impeller and the rotor shaft can be fastened by bolts, but such a simple coupling cannot withstand high temperatures, and therefore other means are required for coupling the turbine impeller. As an example, a turbine impeller includes a so-called inlay (a seat into which a mating part fits) at the bottom, and is coupled to a rotor shaft by electron beam welding in the inlay to form a rotor assembly. Since the rotor assembly rotates at a high speed of several hundred thousand rpm, a slight tilt caused by welding is not allowed. How to ensure the accuracy of the rotor assembly is an important technical challenge.

Related technology is disclosed in Japanese Patent Publication No. 2001-254627.

An object of the present invention is to provide a rotor assembly that does not depend on coupling means that causes a problem in accuracy such as welding and screw fastening, and a method for manufacturing the same.

According to a first aspect of the present invention, a rotor assembly for use in a supercharger and rotating about an axis extends along the axis and is configured to transmit torque and by sintering. An impeller formed into a single body, and an impeller provided with a recess that is crimped and fitted to the rotor shaft by shrinkage due to the sintering.

According to a second aspect of the present invention, there is a rotor shaft configured to extend along an axis and transmit torque, and an impeller formed into a single body by sintering, wherein the impeller is contracted by the sintering. A method of manufacturing a rotor assembly having a recess that is crimped onto a rotor shaft and adapted to mold the recess and the outer diameter of the impeller. A green body having a cavity corresponding to the structure, by assembling a mold that can be divided into a plurality of cavities, injecting a kneaded material containing a metal or ceramic powder and a binder into the mold The rotor shaft is inserted into the recess, the green body is contracted, and the recess is crimped to the rotor assembly, so that the impeller and the low To couple the shaft, sintering the green body, it consists of.

FIG. 1 is a partial cross-sectional view of a supercharger according to an embodiment of the present invention, corresponding to a portion indicated by an arrow I in FIG. FIG. 2 is a cross-sectional view showing the entire supercharger. FIG. 3 is a cross-sectional view of the rotor assembly of the supercharger including an impeller. 4A and 4B are cross-sectional views illustrating the coupling between the impeller and the rotor shaft, wherein FIG. 4A is an enlarged view of IVA in FIG. 3, and FIG. 4B is taken from line IVB-IVB in FIG. FIG. FIG. 5 is a cross-sectional view of an impeller according to a modification of the embodiment. FIG. 6 is a diagram illustrating a process of injection molding the impeller, and is a cross-sectional view of the mold and the green body. FIG. 7 is a schematic cross-sectional view showing the stage of degreasing the green body. FIG. 8 is a schematic cross-sectional view showing the stage of sintering the degreased green body in combination with the rotor shaft. FIG. 9 is a diagram illustrating a process of injection molding the impeller according to the modification, and is a cross-sectional view of the mold and the green body.

Embodiments of the present invention will be described below with reference to the accompanying drawings. For convenience of explanation, a direction indicated as L in the drawing is expressed as a left direction, and a direction indicated as R is expressed as a right direction, but these expressions are not limited to the present invention.

A rotor assembly according to an embodiment of the present invention can be used for the purpose of driving a compressor in a turbocharger for a vehicle, for example, but can also be used for other purposes. Hereinafter, for convenience of explanation, a case of a rotor assembly that drives a compressor of a turbocharger will be described.

Referring to FIG. 2, the turbocharger 1 generally includes a turbine portion drawn on the left in the drawing, a shaft portion drawn in the center in the drawing, and a compressor portion drawn on the right in the drawing. Energy is extracted from the exhaust of the engine by the turbine unit, and the energy is transmitted to the compressor unit through the shaft unit, and the compressor unit compresses the air and sends it to the engine.

The shaft portion includes a bearing housing 3, a radial bearing 5 and a thrust bearing 7 supported by the bearing housing 3, and a rotor shaft 9 rotatably supported by both bearings 5 and 7. The radial bearing 5 supports the rotor shaft 9 in the radial direction, and the thrust bearing 7 supports the rotor shaft 9 in the axial direction, so that the rotor shaft 9 can rotate around the axis C. As shown in FIG. 3, the rotor shaft 9 includes a flange 61 for coupling to the turbine impeller 27 at the left end in the axial direction. As will be described in detail later, the rotor shaft 9 is combined with a turbine impeller 27 to constitute a rotor assembly 29.

Compressor impeller 13 is coupled to the right end of rotor shaft 9 in the axial direction so as to rotate together about axis C. Such coupling is performed by fastening with bolts, but if possible, other means such as welding or fitting may be used. A compressor housing 11 is coupled to the right end of the bearing housing 3 so as to cover the compressor impeller 13. The connection can be by fastening bolts, but may be by other means. The compressor housing 11 secures an appropriate gap with respect to the impeller 13 so as not to interfere with the rotation.

The compressor impeller 13 includes a wheel 15 around the axis C and a plurality of blades 17 extending in the radial direction from the wheel 15. The blades 17 are arranged at equal intervals around the wheel 15, but the arrangement is not necessarily limited to equal intervals. Each blade 17 is inclined with respect to the axial direction, more preferably has an airfoil shape, and air is supplied in a centrifugal direction in a centrifugal direction as the wheel 15 rotates. Each outer edge of each blade 17 is close to the inner wall of the compressor housing 11 so as to minimize airflow diversion.

The compressor housing 11 includes an air intake port 19 and a diffuser passage 21 communicating with the air intake port 19. The air intake 19 is for taking in outside air, and is configured to be coupled to an intake pipe having an air cleaner (not shown). The diffuser passage 21 is a slit-like passage formed so as to surround the outer edge of the base end of the compressor impeller 13, and the air pressurized in the centrifugal direction by the compressor impeller 13 passes through the diffuser passage 21. The compressor housing 11 further includes a compressor scroll passage 23 that communicates with the diffuser passage 21. The compressor scroll channel 23 is a spiral channel that goes around the compressor impeller 13 at least once, and the outer periphery of the diffuser channel 21 opens to the compressor channel 23 over the entire circumference. The opening at the end of the compressor scroll passage 23 is configured to be coupled to an intake manifold (not shown) of the engine.

Referring to FIG. 1, a turbine impeller 27 is coupled to the left end in the axial direction of the rotor shaft 9 so as to rotate together around the axis C to form a rotor assembly 29. As will be described in detail later, such coupling is realized by engagement and pressure bonding using a sintering process, regardless of means such as welding, brazing, or screw fastening. Further welding or brazing may be applied additionally. A turbine housing 25 is coupled to the left end of the bearing housing 3 so as to cover the turbine impeller 27. Such coupling is by fastening bolts or other suitable means. The turbine housing 25 secures an appropriate gap with respect to the turbine impeller 27 so as not to interfere with the rotation.

The turbine housing 25 includes a turbine scroll passage 51 having one end opened to the outside. The turbine scroll flow path 51 is a spiral flow path that makes at least one round around the turbine impeller 27, and the inner periphery thereof opens toward the turbine impeller 27. The externally open end is configured to couple with an exhaust manifold (not shown) to take in exhaust from the engine.

The turbine housing 25 includes a variable nozzle unit 31 disposed so as to be interposed between the turbine scroll passage 51 and the turbine impeller 27. The variable nozzle unit 31 includes a ring 33, a shroud ring 37, and a plurality of nozzles 41. The ring 33 is fixed to the turbine housing 25 via the attachment ring 33. The shroud ring 37 is fixed to the mounting ring 33 via a plurality of connecting pins 39, and a throat through which exhaust gas can pass is secured between the ring 33 and the shroud ring 37. The plurality of nozzles 41 are arranged around the turbine impeller 27 at equal intervals, and are fitted to the

rings

33 and 37 so as to be swingable. Each nozzle 41 includes a vane positioned at the throat between the

rings

33 and 37. The vane can adjust the opening degree of the throat by swinging the nozzle 41. Each nozzle 41 includes a shaft 43 extending rightward in the drawing, and is connected to a synchronization mechanism 45 at the right end of the shaft 43.

As an example, the synchronization mechanism 45 includes a ring member that can rotate around the axis C, and a plurality of links that are respectively connected to the shaft 43 from the ring member. That is, the synchronization mechanism 45 is configured so that the links are driven by the rotation of the ring members, and the shafts 43 are respectively rotated to swing the plurality of nozzles 41 in synchronization. The synchronization mechanism 45 is connected to the lever 49 via the transmission shaft 47 and can be driven by an external actuator.

Note that the variable nozzle unit 31 and the synchronization mechanism 45 described above are necessary only when the turbocharger 1 is a variable displacement type, and may be omitted in other cases. In that case, the turbine scroll flow path 51 communicates with the turbine impeller 27 through an appropriate throat.

The turbine housing 25 includes a discharge port 53 so as to communicate with the left end in the axial direction of the turbine impeller 27. The discharge port 53 is for discharging exhaust gas that has passed through the turbine impeller 27, and is configured to be coupled to an exhaust pipe that includes a purification device (not shown).

As shown in FIG. 3, the turbine impeller 27 is made of metal or ceramic formed into a single body by powder injection molding described later, and includes a wheel portion 55 and a plurality of blades 57 extending in the radial direction from the wheel portion 55. Prepare. The turbine impeller 27 is coupled to the rotor shaft 9 at the right end of the wheel portion 55, thereby configuring the rotor assembly 29.

The plurality of blades 57 are formed integrally with the wheel portion 55 and arranged around the axis C at equal intervals. If possible, it may not be equally spaced. Each blade 57 has an inclination with respect to the direction of the axis C, and more preferably has an airfoil shape, in order to generate torque by receiving an exhaust airflow. Accordingly, the turbine impeller 27 can extract energy from the exhaust and drive the compressor impeller 13 via the rotor shaft 9. Each outer edge of each blade 57 is proximate to the shroud ring 35 to minimize airflow diversion. When there is no variable nozzle unit 31, each outer edge is close to the inner wall of the turbine housing 25.

3 and 4, the wheel portion 55 has a concave portion 59 for coupling with the rotor shaft 9 at the right end thereof. The recess 59 may be a recess that is slightly retracted from the right end of the wheel portion 55, a hole that penetrates considerably into the wheel portion 55, or a hole that penetrates to the left end. Preferably, an inward flange 63 projecting inward from the edge of the recess 59 is provided. The inward flange 63 may be on the same plane as the bottom surface (the rightmost surface in the drawing) of the wheel portion 55, or may protrude from the bottom surface as shown in FIG. The inward flange 63 is configured to engage with the flange 61 of the rotor shaft 9. Preferably, in order to strengthen the engagement, one or more grooves 65 extending in the axial direction may be provided on the outer periphery of the rotor shaft 9, and the protrusions 67 may be provided in the recesses 59 correspondingly. Or conversely, a protrusion extending in the axial direction may be provided on the outer periphery of the rotor shaft 9 and a groove may be provided in the recess 59 so as to correspond thereto.

Alternatively, as shown in FIG. 5, the wheel portion 55 of the rotor assembly 29 </ b> A may include a hole 69 that extends around the axis C from the apex (right end in the drawing) toward the bottom surface. FIG. 5 illustrates a non-through hole 69 having a bottom, which may pass through into the recess 59 if possible. The wheel portion 55 is made thinner due to the hole 69, which is advantageous in preventing the occurrence of internal defects due to sintering.

Exhaust gas discharged from the engine passes through the turbine scroll passage 51 from the intake port, and then flows in a spiral shape into the throat of the variable nozzle unit 31 (the throat of the turbine housing when there is no variable nozzle unit), and further, the turbine impeller 27. The exhaust gives torque to the turbine impeller 27 when passing between the plurality of blades 57 and is discharged to the discharge port 53. Such torque is transmitted to the compressor impeller 13 by the rotor shaft 9 and is used for air compression by rotating the compressor impeller 13. Depending on the flow rate of the exhaust gas, the throat opening degree may be adjusted by swinging the plurality of nozzles 41.

The rotor assembly 29 is manufactured by powder injection molding as follows.

Referring to FIG. 6, a mold 71 and an injection molding machine are used for powder injection molding. The injection molding machine includes a fixed frame 73 and a movable frame 79 for supporting the mold 71. In addition, the injection molding machine includes an injection machine (not shown), an injection nozzle 95, an actuator for driving the movable frame 79, and the like.

The mold 71 is made of an appropriate metal such as SKD11 (JIS G 4404) and can be appropriately divided. In the example of FIG. 6, the mold 71 is divided into a base 75 and an outer mold 85, and each of the base 75 and the outer mold 85 is further divided into a plurality in the circumferential direction. The combination of the forming surface 77 of the pedestal 75 and the forming surface 87 of the outer mold 85 defines a cavity 89 that is adapted to form the outer shape of the turbine impeller 27. The base 75 has a structure suitable for forming the recess 59. Since the volume shrinkage of about 20% occurs due to the sintering, the mold 71 and the base 75 are designed in consideration of the volume shrinkage.

Preferably, a block 81 is interposed between the mold 71 and the movable frame 79. The block 81 has a conical concave surface 83, and the mold 71 has a corresponding tapered surface. When the movable frame 79 presses the mold 71 by the contact between the concave surface 83 and the tapered surface, the portions of the outer mold 85 are in close contact with each other in the circumferential direction. Preferably, an actuator is provided to move each of the outer molds 85 in the radial direction. Such an actuator may be configured to drive the outer mold 85 in synchronization with the movable frame 79.

The fixed frame 73 further includes a spool 97 that communicates with the injection nozzle 95, and the base 75 includes a runner 93 and a gate 91 that communicate with the spool 97 and allow the ejected material to pass therethrough. The runner 93 is provided so as to penetrate the table 75. The gate 91 opens at the right end of the cavity 89. The gate 91 and the spool 97 may be provided in the outer mold 85 or other elements in place of or in addition to the table 75.

Alternatively, in order to manufacture the rotor assembly 29A according to the modification, the core 103 may be provided as in the modification shown in FIG. The core 103 is adapted to mold the hole 69 of the turbine impeller 27. The core 103 may be slightly tapered to facilitate extraction after injection molding. The core 103 may be made of a disappearing material instead of being made of metal. Examples of the evanescent material include thermoplastic resins such as styrene, acrylic, cellulose, polyethylene, vinyl, nylon, and fluorocarbon resins. Appropriate additives may be added. Since the vanishing core is decomposed and evaporated in the degreasing step described later, the extraction after the injection molding can be omitted.

First, the injection M is kneaded. For the injection M, a mixture of metal powder or ceramic powder and a binder is suitable.

As the metal powder or ceramic powder, powders of various materials can be used according to required characteristics. In consideration of heat resistance necessary for the turbine impeller, for example, Ni-base heat-resistant alloy (Inconel 713C, IN100, MAR-M246, etc.) powder and ceramic powder, such as silicon nitride and sialon, can be exemplified.

As the binder, a known powder injection molding binder can be used. As such a powder injection molding binder, for example, a material obtained by adding an additive such as paraffin wax to a thermoplastic resin such as polystyrene or polymethyl methacrylate can be suitably used. Such a binder, after solidifying after injection, retains the form of the injection product until the degreasing step described later, decomposes and evaporates in the degreasing step, and leaves no trace on the sintered product.

The mixture of the metal powder or ceramic powder and the binder is heated to, for example, 100 to 150 ° C. and kneaded. The kneading temperature can be appropriately selected depending on the composition of the kneaded product. After kneading, the injection M is obtained by cooling appropriately.

After preparing the injection M, the elements of the base 75 and the outer mold 85 are placed on the fixed frame 73. If the core 103 is a separate body, it is placed on the base 75. A known release agent may be applied to these in advance. The outer mold 85 is moved inward in the radial direction by the actuator, and the components of the outer mold 85 are brought into contact with each other. Next, the block 81 is brought into contact with these and pressed by the movable frame 79. The movement of the outer mold 85 by the actuator may be synchronized with the movement of the movable frame 79. Therefore, the outer mold 85 and the base 75 are in close contact with each other, and the mold 71 is assembled.

The injection M is heated to, for example, 160 to 200 ° C. to give sufficient fluidity, and is injected into the mold 71 through the injection nozzle 95 with pressurization of about 100 MPa. The heating temperature and the injection pressure can be appropriately selected depending on the composition of the kneaded product. By appropriately cooling, the injection is solidified and the green body 27F is formed.

Next, by driving the actuator, the movable frame 79 is pulled away from the mold 71, and the outer mold 85 is further pulled away from the green body 27F. Moreover, the stand 75 is removed from the inward flange 63F by being displaced from each other. Accordingly, the green body 27F is taken out from the mold 71.

Alternatively, when the mold 71 includes the core 103, the green body 27F can be handled by having the core 103. The core 103 is extracted from the extracted green body 27F using an appropriate jig. When a vanishing core is used, the core 103 may be subjected to a degreasing step described later while being fitted in the green body 27F. In the degreasing process, the vanishing core 103 is decomposed and evaporated to disappear.

As described above, the molded green body 27F is about 20% larger in volume ratio than the final shape in consideration of shrinkage due to sintering. The green body 27F includes a recess 59F that becomes the recess 59 after sintering, and more preferably includes an inward flange 63F, which are also about 20% larger in volume ratio than the final shape. These structures may be formed by machining after injection.

Referring to FIG. 7, the green body 27F is introduced into an appropriate atmosphere control furnace 99. While introducing nitrogen gas into the furnace and maintaining the nitrogen atmosphere, the inside of the furnace is heated to an appropriate high temperature not exceeding 800 ° C. by appropriate heating means such as a carbon heater, and is maintained for 30 minutes or more. The Through such a degreasing process, the binder contained in the green body 27F (and the core 103 when the vanishing core 103 is used) is melted, decomposed, and evaporated to be removed.

The degreasing step may be replaced with other known methods such as elution with an appropriate solvent instead of the above-described method.

As shown in FIG. 8A, the flange 61 of the rotor shaft 9 is inserted into the recessed portion 59F of the degreased green body 27F, and the whole is supported by an appropriate jig, and is placed in an appropriate atmosphere control furnace 101. be introduced. At this time, since it is before shrinkage due to sintering, a slight gap is maintained between the flange 61 and the hole 59F.

The inside of the furnace 101 is placed under an appropriate reduced pressure, and the inside of the furnace is heated to an appropriate sintering temperature, for example, 1000 to 1500 ° C. by an appropriate heating means such as a carbon heater, for an appropriate time, for example, 1 hour or more. Retained. By this sintering process, the sintering progresses and the green body 27F contracts. As a result, the recess 59F is reduced in diameter and comes into contact with the flange 61, and the flange 61 is pressure-bonded to the recess 59 after sintering. Since the flange 61 resists the force that the concave portion 59 tends to contract, the compressive stress can be left, so that the coupling can be stabilized. This residual stress can be appropriately adjusted by the difference in diameter between the recess 59F and the flange 61 and the shrinkage rate of the green body 27F via the composition of the injection.

In the above description, the degreasing step and the sintering step are independent, but these may be carried out continuously.

After cooling appropriately, nitrogen or the like is introduced to bring the inside of the furnace 101 to atmospheric pressure, and the sintered rotor assembly 29 is taken out. It may be used as it is, or an appropriate surface treatment may be applied to remove the film covering the surface.

Note that the mutual crimping of the recess 59 and the flange 61 is similar to a so-called interference fit, but it should be noted that this is not the case. An interference fit is a fit in which one part is forcibly pressed into a space provided by a counterpart part. Usually, an interference fit is achieved by press-fitting the one part into the space. On the contrary, in the pressure bonding between the recess 59 and the flange 61, the space provided by the impeller 27, that is, the recess 59 is forcibly pressed against the flange 61 by shrinkage due to sintering. In other words, this is the opposite of normal interference fit.

According to the present embodiment, since the mutual connection of components does not depend on a process involving local heat input such as welding or brazing, the rotor assembly can be manufactured with high accuracy. Since the impeller is molded and the rotor shaft is not coupled again, but the impeller can be molded and the rotor shaft can be coupled at the same time, the productivity is remarkably improved.

The present embodiment can be preferably applied to a rotor assembly of a turbocharger, but can be applied to various machine parts including a coupling requiring accuracy.

Although the present invention has been described with reference to preferred embodiments, the present invention is not limited to the above embodiments. Based on the above disclosure, a person having ordinary skill in the art can implement the present invention by modifying or modifying the embodiment.

A rotor assembly independent of coupling means that causes problems in accuracy such as welding and screw fastening, and a method for manufacturing the same are provided.

Claims

A rotor assembly for use in a supercharger and rotating about an axis,
A rotor shaft configured to extend along the axis and transmit torque;
An impeller formed into a single body by sintering, and an impeller provided with a recess that is crimped and fitted to the rotor shaft by shrinkage due to the sintering;
Rotor assembly with
The rotor assembly according to claim 1, wherein the rotor shaft includes a groove extending in an axial direction, and the recess includes a protrusion corresponding to the groove.
The rotor assembly of claim 1, wherein the rotor shaft comprises a flange and the recess comprises an inward flange configured to engage the flange.
The rotor assembly according to claim 1, wherein the impeller has a hole extending from the apex toward the bottom surface.
A supercharger comprising the rotor assembly according to claim 1.
A rotor shaft configured to transmit torque by extending along an axis, and an impeller formed into a single body by sintering, and having a recess to be crimped and fitted to the rotor shaft by shrinkage due to the sintering An impeller with a method of manufacturing a rotor assembly with
Having a structure suitable for molding the recess and a cavity suitable for molding the outer diameter of the impeller, and assembling a mold that can be divided into a plurality of parts;
Injecting a kneaded product containing a metal or ceramic powder and a binder into the mold to form a green body having a recess corresponding to the structure,
Inserting the rotor shaft into the recess;
Sintering the green body to shrink the green body and crimp the recess to the rotor assembly to join the impeller and the rotor shaft;
A method consisting of things.