JP2003049661A - Formation method for receiver hole rotatably retaining variable vane in exhaust guide assembly of vgs type turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new formation method highly precisely providing the bore dimension and inner surface roughness of a receiver hole of a turbine frame rotatably retaining a variable vane without any cutting in a VGS(Variable Geometry System) type turbocharger. SOLUTION: This formation method for the receiver hole 25 is characterized in that a prepared hole 25b further smaller than a prepared hole 25a is opened before opening the prepared hole 25a having a dimension of the diameter or less in its completion state by fine blanking, and when the receiver hole 25 is finished, a steel ball having an almost equal diameter of the receiver hole 25 in its completion state is press-fitted in the prepared hole 25a so as to provide the desired precision of the hole diameter and the surface roughness of the hole inner surface.

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 method for efficiently and highly accurately forming a receiving hole for rotatably holding a variable vane in an exhaust guide assembly incorporated in this product.

[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 (a raw material that will be the original form of the turbine frame) with and, the receiving hole that accepts the shaft part of the variable blade is machined on the flange part, specifically, drilled with a drill Later, it was finished by a precision reamer. This receiving hole is a part that receives the variable blade and holds it rotatably, and is an important part for delicately controlling the flow rate of exhaust gas, so it has high hole diameter accuracy and high inner surface roughness. Is the required part.

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. In addition, variable vanes range from 10 to 1 per turbocharger.
Since about 5 units are required, when the actual monthly production of about 30,000 cars is mass-produced, the number of receiving holes to be formed will be about 300,000 to 450,000 places per month, which is very suitable for cutting. It wasn't exhaustive.

Further, in the cutting method, due to the fact that the material is difficult to cut, variations in hole diameter, eccentricity of holes, etc. are relatively likely to occur, so that the hole diameter dimension and the surface roughness of the inner surface of the hole are high. There was a problem that it was difficult to achieve with accuracy. If the desired accuracy in terms of hole diameter, surface roughness, etc. cannot be achieved, for example, the clearance between the receiving hole and the shaft portion of the variable blade becomes inadequate, and smooth rotation of the variable blade, and thus delicate flow rate control, can be performed. There was a problem that it could not be done.

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.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of such a background, and has a hole diameter size without cutting a receiving hole of a turbine frame for rotatably holding a variable blade. This is an attempt to develop a new forming method that can realize both the inner surface roughness and the inner surface roughness with high accuracy.

[0009]

That is, in the method of forming the receiving hole for rotatably holding the variable blade in the exhaust guide assembly of the VGS type turbocharger according to claim 1, a plurality of variable blades are provided at the outer peripheral position of the 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 order to manufacture a turbine frame to be incorporated into a VGS type turbocharger that allows the engine to exhibit high output even at low speed rotation, the variable blade The receiving hole formed in the turbine frame to hold it rotatably is completed. Prior to the diameter below the lower holes in the state is opened, which smaller preliminary hole than the lower hole is opened, when the finish receiving hole,
A steel ball having a diameter substantially equal to the diameter of the receiving hole in the completed state is press-fitted into the lower hole to obtain a desired hole diameter accuracy and surface roughness of the inner surface of the hole. According to the present invention, the receiving hole of the turbine frame for rotatably holding the variable blade is formed by first forming a preliminary hole, then re-forming this preliminary hole into a pilot hole, and further adding a steel ball to this pilot hole. Press fit,
Can be finished. For this reason, the receiving hole can be realized with high accuracy in terms of both the hole diameter and the inner surface roughness without requiring cutting for finishing. Further, the rotation of the variable vanes is stabilized, the exhaust flow rate can be controlled more reliably, and the performance of the exhaust guide assembly and eventually the turbocharger is improved. Further, since the plurality of receiving holes can be finished with high accuracy without requiring cutting, a high quality turbine frame can be efficiently manufactured.

Further, the method of forming the receiving hole for rotatably holding the variable blade in the exhaust guide assembly of the VGS type turbocharger according to the second aspect is the receiving hole of the turbine frame in addition to the requirements of the first aspect. Is characterized in that the pilot hole is opened by fine blanking. According to the present invention, fine blanking (FB) processing is performed on a portion where a preliminary hole smaller than the pilot hole is already opened, and the pilot hole is opened (reformed), so that the force required for the FB processing is small. Finished,
Simultaneous formation of pilot holes at multiple locations is made possible. Further, the re-formation of the preliminary hole by the FB processing can be performed more reliably and with high accuracy, and especially when the flange portion is thick and the processing length is long (about 30 mm as an example).

Further, in the exhaust gas guide assembly of the VGS type turbocharger according to claim 3, a method of forming the receiving hole for rotatably holding the variable vane is the turbine frame in addition to the requirements of claim 1 or 2. The metal base material that is the original form of has a boss portion and a flange portion integrally, and in forming this base material, a precision casting method or a metal injection molding method is applied. The preliminary hole is also opened at this stage of forming the. According to the present invention, it is troublesome in all steps of forming the receiving hole, that is, from the opening of the preliminary hole to the reforming of the preliminary hole, and the finishing of the preliminary hole into the receiving hole. It eliminates all the cutting and makes the mass production of turbine frame a reality.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the illustrated embodiments. The present invention is substantially applied to the turbine frame 2. In the description, first, the exhaust guide assembly A in the VGS type turbocharger in which the turbine frame 2 is incorporated will be described, and in addition, the turbine guide 2 will be described. The frame 2 will be referred to, and then the method for forming the receiving hole of the present invention will be described. The exhaust guide assembly A adjusts the exhaust gas flow rate by appropriately narrowing the exhaust gas G when the engine is rotating at a low speed, and is provided on the outer periphery of the exhaust turbine T as shown in FIG. A plurality of variable blades 1 for setting the flow rate, a turbine frame 2 for rotatably holding the variable blade 1, and a variable mechanism 3 for rotating the variable blade 1 by a certain angle so as to appropriately set the flow rate of the exhaust gas G.
It consists of and. 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, a turbine frame 2 to which the present invention is substantially applied 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 is formed with the same number of receiving holes 25 as the variable blades 1 at the peripheral edge portion. In the present invention, the receiving holes 2 are particularly formed.
5 is formed with high efficiency and finished with high accuracy. Therefore, the substantial application target of the present invention is the frame segment 21.

Further, as shown in FIG. 1, the holding member 22 is formed in a disc shape having a central portion opened. 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 opened in the frame segment 21 and the holding member 22 for receiving 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.

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 constituted as described above, and the method of forming the receiving hole of the present invention will be described below. The receiving hole 25 is formed in the frame segment 21 of the turbine frame 2 described above, and will be described below.
A method of manufacturing the frame segment 21, which is a substantial application object, will be described. Also frame segment 21
Is the flange portion 23 and the boss portion 24 before the completed state,
First, a metal material (hereinafter referred to as a raw material W) integrally provided is formed, and the raw material W is partially modified in shape as necessary or a receiving hole 25 is formed. hand,
The frame segment 21 as a finished product is obtained. Here, the respective portions of the flange portion 23 and the boss portion 24 before being formed on the blank W are defined as a flange forming portion 23a and a boss forming portion 24a, respectively.
In addition, a pre-hole for the receiving hole 25, which is opened by fine blanking (hereinafter referred to as FB) processing or the like, is formed on the material W by 25.
a.

Further, in the present embodiment, the blank W is formed by the precision casting method or the metal injection molding method. At this stage, the pilot hole 25a is prepared as a pilot hole (a pilot hole smaller than the pilot hole 25a. In the present specification, this is designated as the preliminary hole 25b.
(Referred to as) is secured in the blank W (FIG. 2).
(See (a)). This is because a plurality of receiving holes 25 are formed in one frame segment 21, and therefore a plurality of receiving holes 25 are formed at the same time (a spare hole 25b is opened, so it is strictly reformed). Is. Further, by securing the preliminary hole 25b in the material W in advance, even if the flange portion 23 is thick and has a long working length of, for example, about 30 mm, the prepared hole 25a can be formed smoothly and reliably.

(1) Step of Preparing Forming Material In this step, the flange forming portion 23a and the boss forming portion 24a are integrally provided as described above, and the frame segment 2
This is a step of preparing a metal base material W which is the original shape of 1.
In this embodiment, in order to secure the preliminary hole 25b at the stage of forming the blank W, the casting of the blank W is performed by precision casting or metal injection molding. Both methods will be briefly described below.

(A) Precision casting For example, the lost wax method, which is a representative of the precision casting method, reproduces a target product (here, the frame segment 21) in a wax model substantially faithfully in terms of shape and size. After coating the surrounding area with a refractory material, the brazing part inside is melted out to obtain only the refractory material (coating material), and casting is performed using this as a mold. As described above, in the precision casting, the casting product (form material W) is reproduced with high accuracy by forming the mold almost exactly according to the intended product. However, in the present embodiment, when casting,
A virgin material with heat-resistant steel (alloy) as the main base material is applied, and the amount of C (carbon), Si (silicon), and O (oxygen) contained is optimized, for example, the weight of each of C, Si, and O. % To 0.05 to 0.5%, 0.5 to 1.5%, 0.01 to
By setting the content to 0.1%, it is possible to improve the flowability of the molten metal and further improve the dimensional accuracy of the cast product. In addition, for example, by rapidly cooling the metal material cast together with the mold after pouring, the time until the mold is crushed is shortened, the solidified grains of the raw material W are made finer, and a technical device for enhancing the strength and toughness. Can also be taken as appropriate. By adopting such various technical ideas, the preliminary hole 25b of the desired accuracy can be realized in the raw material W with high accuracy in the casting stage. It should be noted that, here, holes other than the receiving hole 25, for example, the pin hole 27, etc., may be opened to be somewhat smaller than the completed state.

(B) Metal injection molding In this method, a binder (mainly an additive for binding metal powders to each other, which is a mixture of polyethylene resin, wax, and phthalate ester) is kneaded with a metal powder as a material. It is a method in which, after imparting plasticity, it is injected into a mold to form a desired shape, the binder is removed, and then the metal is sintered. The (form material W) is obtained. At this time, in order to generate small and uniform independent bubbles (spherical gaps between metal particles), sintering is performed for about 30 minutes to 2 hours, or the molded product is subjected to HIP (Hot Isostatic).
Abbreviation of Pressing; hot isostatic pressing) can be performed to improve the bulk density of the molded product. Further, it is also possible to appropriately take technical measures to make the shape of the metal powder spherical and fine by air atomization, water atomization, or the like as much as possible to improve the high temperature rotary bending fatigue property of the raw material W. At the stage of this metal injection molding, it is possible to form the preliminary hole 25b of the desired accuracy in the material W by various technical means. Also here, holes other than the receiving holes 25, for example, the pin holes 27, etc., can be opened somewhat smaller than the completed state.

(2) Modification of shape, size, etc. After forming the base material W as the original form of the frame segment 21 by the precision casting method or the metal injection molding method as described above, for example, the boss portion 24 of the base material W. (Boss forming portion 24a)
Alternatively, the shapes and sizes (lengths) of the two flange portions 23A and 23B having different diameters are corrected to a desired state (almost completed state) as necessary. Of course, in this correction stage, for example, the pin hole 27 and the like can be appropriately corrected.

(3) Formation (re-formation) of the pilot hole Before and after such modification of the blank W, the preliminary hole 25b opened in the flange forming portion 23a of the blank W has a smaller number than that. It is re-formed in the prepared hole 25a having a larger diameter. Specifically, for example, with respect to the preliminary hole 25b, the precision press device 6
FB processing is performed. The FB processing is a method of performing punching in a so-called zero clearance state in which the clearance of the tool is extremely small while applying a high compressive force to the sheared contour portion of the work material (here, the flange forming portion 23a of the blank W). That is, this is a method in which the cut surface is obtained in a smooth and good state over the entire plate thickness. As shown in FIG. 2B as an example, the precision press device 6 that performs this includes a plate retainer 62 having an annular protrusion 61, a die 63 for sandwiching and holding the template W together with the plate retainer 62, The punch 64, which substantially punches out the blank W, and the reverse presser 65, which is provided opposite to the punch 64, are provided. The plate presser 62 and the reverse presser 65 form the blank W (flange formation). The portion 23a) is pressed against the die 63 and the punch 64 to be compressed.

It should be noted that a plurality of simultaneous punches by FB processing (opening the prepared holes 25a at about 10 to 15 locations at the same time) is originally extremely difficult, but in the present embodiment, the prepared hole is mainly used. Prior to the opening of 25a, the pilot hole 25
By preliminarily opening the preliminary hole 25b corresponding to the pilot hole of a, a plurality of simultaneous punches can be performed. That is, the portion of the raw material W (flange forming portion 23a) punched out by the precision press device 6 has a substantially cylindrical shape, but in the present embodiment, this thickness (shearing allowance punched by FB processing). As an example, the force required for the FB press is minimized and the simultaneous opening (reforming) of a plurality of pilot holes 25a can be realized.

Incidentally, as a technical device other than the above that enables a plurality of simultaneous punching by FB processing, there is a device for manufacturing a die of the precision press machine 6. Specifically, when electric discharge machining of the die of the precision press machine 6 is performed, in order to further improve the diameter dimension and the positional accuracy of the holes, the workpiece machined by electric discharge with the electrode (in this case It is possible to devise to maintain the temperature of the working fluid for immediately cooling the die of the press device 6 within a range of ± 0.5 ° C.

(4) Finishing of receiving hole (steel ball) After the pilot hole 25a is re-formed in the flange forming portion 23a of the blank W as described above, this pilot hole 25a is next time.
Further, the receiving hole 25 in the completed state and the steel ball B having substantially the same size are press-fitted to finish the hole diameter dimension and the surface roughness of the inner surface of the hole to a desired accuracy. At the time of finishing the receiving hole 25, the steel ball B is press-fitted with a punch or the like, so that the substantial finishing process can be performed. However, when the steel ball B and the punch are formed separately, the steel ball B is formed. Since it is a fine member, it is easy to lose it, and when replacing the steel ball B, it takes a lot of time to attach and detach. Therefore, in the present embodiment, as an example, as shown in FIG. 3A, the steel ball B and the punch are integrally formed to improve the handleability of the steel ball B. Here, when distinguishing the punched portion from the steel ball B, the punched portion P is designated by a reference numeral.

Since the steel ball B is integrally formed at the tip of the punch portion P for pressing the steel ball B as described above, the steel ball B in the present embodiment is as shown in FIG. As described above, the connecting portion between the steel ball B and the punch portion P is formed in a tapered shape. Of course, the punch portion P is formed to have a size slightly smaller than the steel ball B due to the action of press-fitting the steel ball B into the lower hole 25a. For example, this relief size is 0.02 to 0.02.
It is formed to have a thickness of about 0.05 mm.

Incidentally, since the wear resistance and the high toughness are required as the material of the steel ball B including the punched portion P, ferro titanite (an alloy of iron and titanium) is used as an example, and the hardness HRC ( A Rockwell hardness of 70 or more is applied. As described above, the steel ball B can be formed separately from the punch part P. In this case, in order to stably hold the steel ball B on the punch part P, as shown in FIG. As shown together with the enlarged view of a), it is preferable that the working tip portion of the punch portion P is formed into a spherical recess (this portion is referred to as a recess Pa). Incidentally, when this form is adopted, the steel ball B can be surely attracted to the concave portion Pa of the punch portion P by magnetic force or the like, and the holding of the steel ball B can be further stabilized.

(5) Finishing of the receiving hole (substantially operating mode) The receiving hole 25 is substantially finished by press-fitting the steel ball B integrally formed with the punch P into the lower hole 25a. Is. Then, in the present embodiment, as shown in FIG. 3B, the steel ball B once penetrating the lower hole 25a is press-fitted so as to be pulled back to the lower hole 25a (reception hole 25), and at least the steel ball The receiving hole 25 is finished by one reciprocating movement of the ball B.

The finish of the receiving hole 25 with the steel ball B is
Rather than shaving off the excess metal material (excessive thickness) on the inner peripheral surface of the pilot hole 25a like a so-called precision reamer, the steel ball B to be press-fitted rather removes the excess metal material on the inner surface side In a substantially orthogonal direction (horizontal direction in this case), or is pushed out (Fig. 3).
(See (a)). Of course, once the surplus meat is pushed away,
After passing the steel ball B, it has a tendency to return in the direction of narrowing the hole diameter, that is, what is called springback. Therefore, in the present embodiment, considering this springback,
The diameter of the steel ball B with respect to the completed diameter (the receiving hole 25) is appropriately determined, and the receiving hole 25 is finished by one or more reciprocating operations of the steel ball B.

Further, the size at which the steel ball B pushes away the excess thickness of the inner peripheral surface of the lower hole 25a at the time of press-fitting is set as a sizing size. As an example, this sizing size is 0.03 to 0.
It is suppressed to about 05 mm or less. Here, the relationship between the sizing dimension and the press-fitting speed (processing speed) of the steel ball B is shown in FIG. 4, and the press-fitting speed of the steel ball B is appropriately adjusted according to the sizing dimension. In the graph, the curve sandwiched between the hatched parts shows the standard for the relationship between the sizing dimension and the press-fitting speed of the steel ball B, and the upper and lower hatched parts show the allowable range for this. By setting the speed within this range, appropriate processing conditions can be obtained.

As described above, according to the present invention, the receiving hole 25 is finished by press-fitting the steel ball B, which makes it possible to realize a high hole diameter accuracy and a high surface roughness of the inner surface of the hole. It can be finished. Further, since finishing of the receiving hole 25 does not require time-consuming cutting, mass production of the turbine frame 2 becomes more practical. Further, since the steel ball B is formed integrally with the working tip of the punch P, the steel ball B can be completely held and the finished length is long, that is, the flange 23 has a large wall thickness (for example, about 30 mm). In addition, the finishing process can be efficiently performed, which is a particularly effective form.

[0036]

Other Embodiments The present invention has the above-described embodiments as one basic technical idea, but the following modifications are possible. That is, in the above-described embodiment, the blank W is formed by the precision casting method or the metal injection molding method, and at this stage, the preliminary hole 25 of the receiving hole 25 is also combined.
b is opened. However, for example, the blank W can be formed by deep-drawing a blank material punched to a substantially constant thickness (about 5 mm as an example) in addition to the above method. in this case,
It is extremely difficult to open the preliminary hole 25b at the same time as the blanking process or the deep drawing process because the accuracy of the preliminary hole 25b cannot be maintained and the processing itself and the apparatus become complicated. Therefore, the opening of the preliminary hole 25b is formed by deep drawing a blank material to form the boss forming portion 24a.
After forming so as to protrude, it is generally performed separately before finishing.

[0037]

According to the first aspect of the present invention, the receiving hole 25 of the frame segment 21 for rotatably holding the variable blade 1 first opens the preliminary hole 25b, and then the preliminary hole 25b is formed.
Since the steel balls B are re-formed into 5a and the steel balls B are press-fitted therein for finishing, efficient finishing can be performed according to the actual mass production system without requiring time-consuming cutting. For this reason, the rotation of the variable vane 1 is further stabilized, which contributes to the improvement of the performance of the exhaust guide assembly A and thus the turbocharger.

According to the invention of claim 2, the pilot hole 2
Since the opening (reforming) of the pilot hole 25a, which is performed for the preliminary hole 25b that is slightly smaller than 5a, is performed by the FB processing, the load on the precision press device 6 that performs the FB processing is reduced. It is possible to realize simultaneous opening of the pilot holes 25a at about 15 places.

Further, according to the third aspect of the present invention, since the raw material W of the frame segment 21 is formed by the precision casting method or the metal injection molding method, the raw material material W having a near net shape close to the finished state can be obtained. can get. The spare hole 2
Since 5b is also formed at the stage of obtaining the blank W, the preliminary hole 25b can be realized with high accuracy, and the pre-hole 2 in the post-process can be formed.
The formation of 5a can be performed smoothly and reliably. Furthermore, the preliminary hole 25b is formed at the stage of obtaining the blank W, and FB processing is applied to this to open (reform) the lower hole 25a, and the steel ball B is press-fitted therein to finish the receiving hole 25. Therefore, it is possible to eliminate all the cutting work from the forming process of the frame segment 21, which makes the mass production of the frame segment 21 even more practical.

[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 a cross-sectional view showing in stages how a receiving hole is formed in a frame segment.

FIG. 3 is a cross-sectional view showing stepwise how a receiving hole is formed in a frame segment.

[Fig. 4] Sizing dimensions when finishing the receiving hole,
It is a graph which shows the relationship with the press-fit speed (processing speed) of a steel ball.

[Explanation of symbols]

1 variable wings 2 turbine frame 3 variable mechanism 6 Precision press equipment 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 25 receiving hole 25a pilot hole 25b spare hole 26 Caulking pins 27 pin hole 31 Rotating member 32 transmission member 32A drive element 32B passive element 33 ring 61 annular protrusion 62 Plate retainer 63 dice 64 punch 65 Reverse presser A Exhaust guide assembly B steel ball G exhaust gas h blade height P punch part Pa recess T exhaust turbine W material

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 incorporated in a charger, in order to rotatably hold the variable blade, a receiving hole formed in the turbine frame has a prepared hole which is smaller than or equal to a diameter in a completed state. Prior to this, a preliminary hole that is smaller than the pilot hole is opened.When finishing the receiving hole, A variable blade is used in the exhaust guide assembly of the VGS type turbocharger, which is characterized in that a steel ball having a diameter substantially equal to the diameter of the receiving hole in the completed state is press-fitted to obtain desired hole diameter accuracy and surface roughness of the inner surface of the hole. A method for forming a receiving hole that holds a rotatable member. 2. The variable blade in the exhaust guide assembly of a VGS type turbocharger according to claim 1, wherein the receiving hole of the turbine frame has a lower hole formed by a fine blanking process. Method for forming holding hole for holding. 3. The metal base material that is the original form of the turbine frame has a boss portion and a flange portion integrally, and when forming the base material, a precision casting method or a metal injection molding is used. The variable blade is rotated in the exhaust guide assembly of the VGS type turbocharger according to claim 1 or 2, wherein the preliminary hole is also opened at this stage of forming a blank by applying the method. Method of forming receiving hole that holds freely.