JP2003048029A - Method for manufacturing turbine frame capable of turnably holding variable blade in exhaust guide assembly of vgs type turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method in which a turbine frame capable of turnably holding a variable blade in a VGS type turbocharger can be efficiently mass-produced without needing a cutting process. SOLUTION: This manufacturing method comprises a work preparing step in which a blank punched so as to integrate a boss forming part 24a with a flange forming part 23a forms a blank work W of a frame segment 21, a prepared hole opening step of opening a prepared hole 24b for burring in a substantially center part of the work W at a state where either of both of the work W and an opening device 6 are heated at 50-200 deg.C, and a burring step of ejecting the boss forming part 24a of the work W to the flange forming part 23a at a state where either or both of the work W and a burring device 7 are heated at 50-200 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbocharger used in an automobile engine or the like,
In particular, the present invention relates to a novel method for efficiently manufacturing a turbine frame which is incorporated in this and holds a variable blade rotatably.

[0002]

BACKGROUND OF THE INVENTION A turbocharger is known as a supercharger used as a means for increasing the output and improving the performance of an automobile engine. This turbocharger drives a turbine by the exhaust energy of the engine, It is a device that rotates the compressor by the output and brings the engine into a supercharged state that is higher than natural intake. By the way, in this turbocharger, when the engine is rotating at a low speed, the exhaust turbine hardly works due to a decrease in the exhaust flow rate, and therefore, in the case of an engine that can rotate up to a high rotation range, the turbine has a feeling of rattling until it rotates efficiently, It was inevitable that the so-called turbo lag, etc., required for the subsequent blowing up of the air all at once. Also, the diesel engine, which has a low engine speed, has a drawback that it is difficult to obtain a turbo effect.

For this reason, a VGS type turbocharger has been developed which operates efficiently even in a low rotation range. Even in low-speed rotation, this type uses multiple variable blades (wings) arranged on the outer circumference of the exhaust turbine to narrow down the exhaust gas with a small flow rate, increase the speed of exhaust, and increase the work of the exhaust turbine. It is designed to exhibit high output. For this reason, the VGS type turbocharger requires a separate variable blade variable mechanism,
The peripheral components also had to be more complicated in shape and the like than conventional ones.

In manufacturing a turbine frame for rotatably holding variable blades in such a VGS type turbocharger, for example, a precision casting method typified by lost wax casting or the like is used to form a boss portion and a flange portion. After first forming a metal material (form material that is the original form of the turbine frame) that includes and, and then cutting such a form material as appropriate to finish it to the desired shape and size. It was

However, such a cutting method has the following problems. That is, since this type of turbo equipment is generally used in a high temperature and exhaust gas atmosphere, heat resistant stainless steel such as SUS310S having excellent heat resistance and oxidation resistance is also applied to the turbine frame. However, such a material is generally a material that is difficult to cut, and there is a problem that it takes a long time for cutting and it takes time and effort for processing. Therefore, eliminating the cutting process from the manufacturing process of the turbine frame as much as possible has been a problem in realizing mass production.

In recent years, especially in diesel vehicles,
Exhaust gas emitted into the atmosphere is currently strongly regulated from the viewpoint of environmental protection, and NO _x and particulate matter (P
In order to reduce M) and the like, mass production of a VGS type turbocharger that can improve the efficiency of the engine from a low rotation range has been earnestly desired.

[0007]

The present invention has been made in view of such a background, and a turbine frame that rotatably holds a variable blade can be efficiently mass-produced without cutting. This is an attempt to develop a new manufacturing method as described above.

[0008]

That is, a method of manufacturing a turbine frame for rotatably holding a variable blade in an exhaust guide assembly of a VGS type turbocharger according to claim 1 is provided with a plurality of variable blades at an outer peripheral position of an exhaust turbine. Is rotatably held, relatively small exhaust gas discharged from the engine is appropriately narrowed down by the variable vanes, the speed of the exhaust gas is amplified, the exhaust turbine is rotated by the energy of the exhaust gas, and directly connected to this exhaust turbine. In manufacturing a turbine frame incorporated in a VGS type turbocharger that allows the engine to exhibit high output even at low speed rotation, the process is as follows: The boss forming part and the flange forming part are made of a metal material having a substantially constant plate thickness. A blank material punched so as to have in the body is used as a raw material that is a prototype of a turbine frame, and either or both of the raw material and the opening device are set to 50 to 200. In a state of being heated to ℃, a pre-hole for burring is opened in the substantially central part of the raw material, and either one or both of the raw material opening step and the raw material or the burring device are heated at 50 to 200 ℃.
And a burring step of forming the boss forming portion of the base material in the state of being heated to the flange forming portion. According to the present invention, the turbine frame of the VGS type turbocharger can be efficiently manufactured without cutting. That is, this type of turbine frame is a heat-resistant material, and the plate thickness is, for example, as thick as about 5 mm, so that it is extremely difficult to manufacture by burring, and conventionally, it was forced to perform time-consuming cutting after casting. However, according to the present invention, it is possible to efficiently mass-produce a difficult-to-machine turbine frame by burring. In particular, since the raw material and equipment are heated in the pilot hole opening process and the burring process, the raw material is easily deformed, the workability of the raw material is improved, and wrinkles, cracks and local parts of the raw material in the burring process are improved. Defects such as lack of wall thickness can be eliminated.

Further, in the method for manufacturing a turbine frame in which the variable vanes are rotatably held in the exhaust guide assembly of the VGS type turbocharger according to claim 2, in addition to the requirements according to claim 1, , An austenitic heat resistant material is applied, and heating of the raw material or opening device in the process of opening the pilot hole, and heating of the raw material or burring device in the burring process, It is characterized in that the heating temperature is set according to the Md ₃₀ value which is a work-induced martensitic transformation index. According to the present invention, the optimum heating temperature can be determined from the Md ₃₀ value of the material type used, and smooth burring processing can be realized.

Furthermore, a method of manufacturing a turbine frame for rotatably holding variable blades in an exhaust guide assembly for a VGS type turbocharger according to claim 3 is
In addition to the requirements of claim 1 or 2, a water-soluble heat-resistant lubricant is applied in the burring step. According to the present invention, since the water-soluble heat-resistant lubricant is applied in the burring process, the burring process can be performed smoothly and reliably, and the coating property, the drying property, the high temperature lubricity, and the removal property associated with the use of the lubricant are removed. Therefore, the turbine frame can be manufactured more efficiently. By the way, a general lubricant cannot be used in a high temperature atmosphere such as the turbocharger of the present application because the viscosity decreases due to heating and the lubricity deteriorates, and high viscosity such as WS ₂ and MoS ₂ The above-mentioned lubricant is poor in workability, particularly in removability, and is not suitable for the present application.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the illustrated embodiments. In the description, an exhaust guide assembly A in a VGS type turbocharger incorporating the turbine frame 2 to which the present invention is applied will be described, and the turbine frame 2 will also be described therein.
Then, a method of manufacturing the turbine frame material of the present invention will be described. The exhaust guide assembly A is for adjusting the exhaust flow rate by appropriately narrowing the exhaust gas G when the engine is rotating at a low speed.
As an example, as shown in FIG. 1, a plurality of variable blades 1 that are provided on the outer circumference of the exhaust turbine T and that substantially set the exhaust flow rate.
And a turbine frame 2 for rotatably holding the variable blade 1.
And a variable mechanism 3 for rotating the variable blade 1 at a constant angle so as to appropriately set the flow rate of the exhaust gas G.
Each component will be described below.

First, the variable blade 1 will be described. As an example, as shown in FIG. 1, a plurality of these are arranged in an arc shape along the outer periphery of the exhaust turbine T (one exhaust guide assembly A
Approximately ten to fifteen of them are disposed, and each of them is rotated by approximately the same degree to appropriately adjust the exhaust gas flow rate. Each variable blade 1 comprises a blade portion 11 and a shaft portion 12. The blade portion 11 is formed so as to have a constant width mainly according to the width dimension of the exhaust turbine T, the cross-section in the width direction thereof is formed into a substantially blade shape, and the exhaust gas G is effectively exhaust turbine. It is configured to go to T. Here, the width dimension of the blade portion 11 is referred to as a blade height h for convenience. In addition, the shaft portion 12 is formed so as to be continuous with the wing portion 11 integrally, and is a portion corresponding to a rotating shaft when the wing portion 11 is moved.

At the connecting portion between the blade portion 11 and the shaft portion 12, there is provided a taper portion 13 that narrows from the shaft portion 12 toward the blade portion 11, and a flange portion 14 having a diameter slightly larger than that of the shaft portion 12. Are formed to be continuous. The bottom surface of the collar portion 14 is formed substantially on the same plane as the end surface of the blade portion 11 on the shaft portion 12 side, and this plane serves as a sliding surface when the variable blade 1 is attached to the turbine frame 2, The smooth rotating state of the blade 1 is ensured. Furthermore, at the tip of the shaft 12,
A reference surface 15 is formed which serves as a reference for the mounting state of the variable blade 1. The reference surface 15 is a portion that is fixed to the variable mechanism 3 described later by crimping or the like. As an example, as shown in FIG. And is formed in a substantially constant inclination state.

Next, the turbine frame 2 manufactured according to the present invention will be described. This is configured as a frame member that rotatably holds a plurality of variable blades 1. As an example, as shown in FIG. 1, the variable blade 1 is sandwiched by a frame segment 21 and a holding member 22. Is configured as follows. And frame segment 2
1 is a flange portion 23 that receives the shaft portion 12 of the variable blade 1.
And a boss portion 24 for fitting the variable mechanism 3 described later on the outer periphery. Due to such a structure, the flange portion 23 has the same number of receiving holes 25 as the variable blades 1 formed at the peripheral edge portion at equal intervals.

Further, the holding member 22 is formed in a disc shape having a central portion opened as shown in FIG. The dimension of the variable blade 1 sandwiched between the frame segment 21 and the holding member 22 is substantially constant (generally, the blade width of the variable blade 1 is approximately constant so that the blade portion 11 of the variable blade 1 can always be smoothly rotated. The dimension between the two members is maintained by the caulking pins 26 provided at four places on the outer peripheral portion of the receiving hole 25, for example. Here, the holes formed in the frame segment 21 and the holding member 22 to receive the crimping pins 26 are referred to as pin holes 27.

In this embodiment, the flange portion 23 of the frame segment 21 has two flange portions, that is, a flange portion 23A having substantially the same diameter as the holding member 22 and a flange portion 23B having a diameter slightly larger than the holding member 22. , Which are made of the same material,
In the case where processing with the same member becomes complicated, it is also possible to form two flange portions having different diameters by dividing them and then to join them by caulking or brazing.

Here, the “method for manufacturing a turbine frame” of the present invention substantially refers to a method for manufacturing the frame segment 21. The frame segment 21 is made of a blank material punched from a heat-resistant metal material having a substantially constant plate thickness so as to integrally have a flange portion 23 and a boss portion 24. Frame segment 21 as a finished product
Is what you get. A blank material that is in the original shape of the segment and a member until the blank material is formed into a segment as a finished product are referred to as a blank material W.

Next, the variable mechanism 3 will be described. This is provided on the outer peripheral side of the boss portion 24 of the turbine frame 2 and rotates the variable blade 1 in order to adjust the exhaust flow rate. As an example, as shown in FIG. The variable blade 1 includes a rotating member 31 that causes the variable blade 1 to rotate, and a transmission member 32 that transmits the rotation to the variable blade 1. The rotating member 31 is formed in a substantially disc shape with an opening in the central portion as shown in the figure, and the same number of transmitting members 32 as the variable blades 1 are provided at equal intervals on the peripheral portion thereof. The transmission member 32 includes a drive element 32A rotatably attached to the rotating member 31 and the variable blade 1.
Element 32 fixedly mounted on the reference plane 15 of the
B is included, and the rotation is transmitted in a state where the drive element 32A and the passive element 32B are connected. Specifically, a rectangular piece-shaped drive element 32A is rotatably pinned to the rotating member 31, and a passive element 32B formed in a substantially U shape so as to receive the drive element 32A is variable. Fixed to the reference surface 15 at the tip of the wing 1, and the square-piece-shaped drive element 32A is replaced by the U-shaped passive element 32.
The rotation member 31 is fitted in the B and is engaged with both.
Is attached to the boss portion 24.

In the initial state in which a plurality of variable vanes 1 are attached, in order to align them in a circumferential shape, each variable vane 1 and the passive element 32B need to be attached at a substantially constant angle. In the above embodiment, the reference surface 15 of the variable vane 1 mainly plays this role. Further, when the rotating member 31 is simply fitted in the boss portion 24, when the rotating member 31 is slightly separated from the turbine frame 2,
Since there is concern that the engagement of the transmission member 32 may be released, in order to prevent this, a ring 33 or the like is provided so as to sandwich the rotating member 31 from the opposite side of the turbine frame 2,
The rotation member 31 is given a tendency to be pressed toward the turbine frame 2 side. With such a configuration, when the engine rotates at a low speed, the rotating member 31 of the variable mechanism 3 is appropriately rotated, and the shaft portion 12 is moved through the transmission member 32.
And the variable blade 1 is rotated as shown in FIG. 1, the exhaust gas G is appropriately narrowed, and the exhaust flow rate is adjusted.

An example of the exhaust guide assembly A to which the present invention is applied is configured as described above, and a method for manufacturing a turbine frame of the present invention will be described below (see FIG. 2). The “turbine frame” here substantially refers to the frame segment 21 as described above. The frame segment 21 is made of a blank material (cutting material W) punched out to have a substantially constant plate thickness as a starting material, and after forming a burring pilot hole at approximately the center of the cutting material W. , Forming the boss portion 24 in a protruding state, opening the receiving hole 25 and the pin hole 27, etc.
Appropriate processing is performed to obtain the target frame segment 21. Here, when distinguishing the flange portion 23 and the boss portion 24 formed on the blank W from the completed one, the flange forming portion 23a and the boss forming portion 24, respectively.
a.

(1) Preparation Step of Blank Material (Punching of Blank Material) In this step, a blank material (blank material) having a substantially constant plate thickness and having a size capable of realizing the target frame segment 21 is formed. This is a step of preparing the material W), in which a blank material having a substantially circular shape in plan view and having a plate thickness of about 5 mm is punched from a strip steel or the like. Here, the material of the blank W is, for example, SUS3.
An austenitic heat-resistant rolled material such as 10S, SUH310, and SUH660 is applied. By the way, when the raw material W is obtained by casting, that is, when a heat-resistant cast material is applied as the raw material of the raw material W, burring processing or the like performed in the subsequent step is extremely difficult to perform, so in the present invention, the heat-resistant rolled material is used. The blank material punched out is used as the raw material W. Note that the blank material does not necessarily need to be prepared by punching from such a plate-like member, and if a blank material punched into an appropriate shape in advance (particularly a commercial product) is applicable, carry it in and It can also be used as a step of preparing the profile.

(2) Opening process of the pilot hole The blank W punched to an appropriate size has the burring pilot hole 24b at the substantially central portion thereof, and here, as an example, FIG. As shown in
The punching hole 24b is punched by the opening device 6 having the punch 62 as a main member. Of course, the prepared hole 24b is formed to have a diameter smaller than the inner diameter of the boss portion 24 in the completed state, and for example, has a diameter dimension of about 70% of the boss portion 24 in the completed state. Then, the raw material W having the lower hole 24b opened is formed in a substantially donut shape in a plan view, as also shown in FIG.

In the step of opening the pilot hole, one or both of the blank W and the opening device 6 is set to Md which is a work-induced martensitic transformation index of the material.
_The heating is performed at 50 to 200 ° C. according to the value of ₃₀ . This Md ₃₀ is peculiar to an austenitic (stainless steel) material, and when a uniaxial tensile true strain of 0.30 is applied to an austenitic raw plate, 50 vol% of the austenitic phase is a martensite with high ferromagnetic strength. It indicates the temperature of transformation into the site phase, and the higher this value is, the stronger the tendency of the material to change to martensite. Then, it is a value determined in advance by the component composition of the heat-resistant material applied to the raw material W and the micro crystal grain size.

Where Md ₃₀ = 25 ° C. and Md ₃₀ = 50 ° C.
The relationship between the deformation temperature and the martensite transformation amount in each case is shown in FIG. 3. From this figure, in order to obtain the same amount of martensite transformation amount, the higher the value of Md ₃₀ , the It turns out that the temperature must be raised. Therefore, the higher the value of Md ₃₀ is,
The heating temperature of the opposite type is set to a high temperature, and as an example, when the Md ₃₀ = 0 ° C.
Set the heating temperature to about 150 ° C and set Md ₃₀ =
When the temperature is 20 ° C., the heating temperature is set to about 200 ° C.

By opening the pilot hole 24b at an appropriate working temperature according to the material type of the blank W in this manner, the metal material of the blank W becomes easy to flow, and the burring in the opening process and the next process is performed. It is easy to process. That is, the number vo
Since an appropriate small amount of 1% or less of martensite is uniformly distributed with transformation with a dislocation density equal to that of austenite, it is possible to perform burring in the next step (processing according to the Md ₃₀ value of the material even during burring). Temperature, but)
The stretch flangeability and the fracture resistance are simultaneously improved, and the deformation allowance at the time of burring is increased. By the way, the hole expansion ratio in the normal case is about 1.2 (depending on the material), but the heating in accordance with the Md ₃₀ value of the material causes 1.
It has been confirmed by the applicant that the degree of improvement is significantly increased to about 5. The hole expansion ratio is a value obtained by dividing the limit burring diameter by the lower hole diameter, and the larger this value, the larger the deformation allowance. Of course, by setting the processing temperature according to the Md ₃₀ value, the pressing force of the punch 62 required for opening the prepared hole can be reduced, and the opening operation itself can be easily performed.

(3) Burring Process The material W formed in a substantially donut shape in plan view is then extruded by the burring device 7 so as to expand the pilot hole 24b, and formed into a tubular shape (pipe shape). It
At this time, as shown in FIG. 2 as an example, the burring device 7 includes a die 71 and a plate retainer 72 for holding the peripheral edge portion (flange forming portion 23a) of the raw material W so as to sandwich it, and a lower portion of the raw material W. The central portion including the hole 24b (the boss forming portion 24
The main member is a punch 73 projecting a) to the peripheral portion. Then, the blank W is pressed by the punch 73, is pushed into the substantial molding action portion 74 formed in the die 71, and is subjected to burring processing. It should be noted that the burring device 7 is appropriately provided with an opposing punch 75 or the like that presses the blank W from the opposite side of the punch 73, and mainly by the opposing punch 75.
The tips of a are aligned on substantially the same plane. Further, the opposing punch 75 can also have a knockout function of ejecting the blank W that has been subjected to the burring process from the forming action portion 74 of the die 71.

Also in the burring step, either one or both of the blank W and the burring device 7 is heated at 50 to 200 ° C. depending on the value of Md ₃₀ which is the index of martensitic transformation of the material. It is done by heating to. When performing pilot hole opening and burring in this way, by heating according to the Md ₃₀ value of the material,
This is to increase the deformation allowance of the blank W during burring. Here, the raw material W that the present applicant conducted
An example of the relationship between the heating temperature and the hole expansion ratio is shown in FIG. The material W used here is SUS310S.
The annealed material has a plate thickness of about 5 mm and Md ₃₀ = −10 ° C. Incidentally, in this table, it can be seen that the hole expansion ratio at room temperature was 1.1, but it was significantly increased to about 1.7 by setting the processing temperature to about 80 ° C.

(4) During the application of the lubricant and the burring process, the burring device 7 and the blank W are formed.
The water-soluble heat-resistant lubricant for reducing the frictional force is applied to the contact surface with, for example, the contact portion between the punch 73 and the inner surface of the boss forming portion 24a. This lubricant is a special heat-resistant lubricant prepared by adding wax to either or both of trimethyl borate and phosphate, and mixing them in an organic solvent or water. The coating or coating is formed by coating, a roll coater, a dropping method, a preliminary reaction treatment, or the like. By the way, a general lubricant cannot be used in a high temperature atmosphere such as that of the present application because the viscosity is lowered by heating and the lubricity is deteriorated, and a high viscosity lubricant such as WS ₂ or MoS _{2 is} used. Is poor in workability, especially in removability, and is not comparable to the present application. On the other hand, the above-mentioned water-soluble heat-resistant lubricant not only enables smooth and reliable burring, but also improves the coating properties, drying properties, high-temperature lubricity, and removability associated with the use of the lubricant. This contributes to more efficient manufacturing of the frame 2.

The burring process is completed, and the blank W having the boss forming portion 24a raised against the flange forming portion 23a is taken out from the burring device 7. Note that FIG.
In the frame segment 21 shown in (1), the flange portion 23 is composed of two different diameters, so that the flange portion 23 is generally thicker than the boss portion 24 as a whole. However, in the present application, since a blank material having a substantially constant plate thickness is used as a starting material, it is almost impossible to form the flange forming portion 23a of the raw material W to be thicker than the boss forming portion 24a. Therefore, for example, the flange forming portion 23a formed on the raw material W is a small-diameter side flange portion 23A, and the large-diameter side flange portion 23B is formed separately from the flange portion 23A. It is possible to join with. Of course, the flange forming portion 23a formed on the blank W may be utilized as the large-diameter flange portion 23B, and the small-diameter flange portion 23A may be separately formed and joined.

Further, since the forming hole W and the pin hole 27 are not opened in the flange forming portion 23a in the state where the burring process is completed, the forming material W is appropriately opened by punching or the like, or other portions. Are finished to the desired shape and size as required. By the way, the processing of the receiving hole 25 after the burring is performed because the stress of the raw material W received at the time of the opening of the pilot hole, the burring, etc.
This is to minimize the deviation due to (including thermal stress due to heating). However, if these do not particularly affect the receiving hole 25, the receiving hole 25 may be opened at the stage of the raw material W. It is possible.

The burring process itself on a metal plate has been devised in the past, but this is intended for thin steel plates such as stainless steel. Moreover, the present situation is that it cannot be applied to a relatively thick plate thickness of about 5 mm. However, in the present embodiment, as described above, various technical measures such as heating at the time of opening the pilot hole, heating at the time of burring, application of a special lubricant during burring, etc. For this, the burring process is actually applicable.

[0032]

According to the invention described in claim 1, first, by heating at the time of opening a pilot hole for burring or at the time of burring,
The burring process of a heat-resistant material having a relatively large plate thickness (about 5 mm as an example) and difficult to process is made practical. Therefore, it is possible to realize mass production of the turbine frame 2 of the VGS type turbocharger.

According to the second aspect of the present invention, the blank W is subjected to burring and the like under appropriate temperature conditions according to the amount of processing-induced martensite transformation of the heat-resistant material used. Therefore, the turbine frame 2 with higher accuracy can be manufactured.

Furthermore, according to the third aspect of the invention, since a special water-soluble heat-resistant lubricant is applied, the frictional resistance between the burring device 7 and the base material W is effectively reduced during the burring process. In addition to being able to do, the coating property and the removability can be improved.

[Brief description of drawings]

FIG. 1 shows a V incorporating a turbine frame according to the present invention.
It is a perspective view (a) which shows a GS type turbocharger, and an exploded perspective view (b) which shows an exhaust guide assembly.

FIG. 2 is an explanatory diagram showing a process of opening a pilot hole and a burring process together with a processed blank.

FIG. 3 is a graph showing the relationship between the deformation temperature and the amount of martensite transformation in each case of Md ₃₀ = 25 ° C. and Md ₃₀ = 50 ° C.

FIG. 4 is a table showing an example of the relationship between the hole expansion ratio of the base material and various processing temperatures.

[Explanation of symbols]

1 variable wings 2 turbine frame 3 variable mechanism 6 opening device 7 Burling machine 11 wings 12 Shaft 13 Tapered part 14 Tsubabe 15 Reference plane 21 frame segments 22 Holding member 23 Flange 23a Flange forming part 23A Flange (small) 23B Flange (large) 24 Boss 24a Boss forming part 24b pilot hole 25 receiving hole 26 Caulking pins 27 pin hole 31 Rotating member 32 transmission member 32A drive element 32B passive element 33 ring 61 dice 62 punch 71 dice 72 Plate clamp 73 Punch 74 Molding part 75 Opponent punch A Exhaust guide assembly G exhaust gas h blade height T exhaust turbine W material

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02B 39/00 F02B 39/00 U 37/12 301Q

Claims (3)

[Claims] 1. A plurality of variable blades are rotatably held at an outer peripheral position of an exhaust turbine, and a relatively small amount of exhaust gas discharged from an engine is appropriately narrowed down by the variable blades to amplify the speed of the exhaust gas. A VGS-type turbo that rotates the exhaust turbine with the energy of the exhaust gas and sends air above the naturally aspirated air to the engine with a compressor directly connected to this exhaust turbine so that the engine can deliver high output even at low speed rotation. In manufacturing a turbine frame to be incorporated in a charger, the process is to prepare a blank material punched from a metal material having a substantially constant plate thickness so as to integrally have a boss forming portion and a flange forming portion. One of the raw material or the opening device and the raw material preparation process, which is the original raw material In the state where both are heated to 50 to 200 ° C., a pilot hole for burring is opened at approximately the center of the blank, and either one or both of the blank and the burring device are opened. Variable in the exhaust guide assembly of the VGS type turbocharger, characterized in that it has a burring step of forming the boss forming portion of the blank into the flange forming portion in a state of being heated to 50 to 200 ° C. A method for manufacturing a turbine frame that rotatably holds a blade. 2. An austenitic heat-resistant material is applied to the raw material, and the raw material or the heating device for the raw material in the step of opening the pilot hole and the raw material in the burring step. Alternatively, the heating of the burring device is performed by using Md ₃₀ which is a work-induced martensitic transformation index of the raw material.
The method for manufacturing a turbine frame according to claim 1, wherein the heating temperature is set according to the value, and the variable blade is rotatably held in the exhaust guide assembly of the VGS type turbocharger according to claim 1. 3. A turbine for rotatably holding variable blades in an exhaust guide assembly of a VGS type turbocharger according to claim 1, wherein a water-soluble heat resistant lubricant is applied in the burring step. Frame manufacturing method.