JP2003314290A - Variable capacity turbocharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable capacity turbocharger for an internal combustion engine, in which variation in performance characteristics is reduced, and reliability of vanes (partition walls) is improved. <P>SOLUTION: The partition wall 23 comprises a plurality of vanes 29a, which are formed as members separated from a cast turbine-housing 21. The vanes 29a are integrally formed with the turbine housing 21 at the time of cast-molding of the housing 21. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable capacity turbocharger for supercharging an internal combustion engine.

[0002]

2. Description of the Related Art A conventional variable capacity turbocharger is disclosed in, for example, Japanese Patent Laid-Open No. 10-8977. This variable capacity turbocharger is designed to ensure performance in the low speed range and performance in the medium and high speed ranges.
The turbine housing is provided with inner / outer scroll portions and vanes (compartment walls) separating the inner / outer scroll portions. By the way, in this variable displacement turbocharger, the vanes (compartment walls) are integrally formed with the turbine housing by casting. However, since the vane shape is formed by casting, in order to ensure the performance in the medium and high speed ranges, when the exhaust gas flows in the inner and outer scrolls are smoothly joined, there is a limit to the guide function of the exhaust gas flow. . Further, the variation in performance characteristics becomes large. Since the temperature of the exhaust gas is increasing due to the higher output of the diesel engine and the direct injection of the gasoline engine, the stress concentration due to the thermal expansion due to the temperature rise of the vanes may cause cracks and reduce the reliability. I'm worried. In addition, since the housing type has a complicated structure, the flow of molten metal deteriorates, the number of defective products increases, and the cost increases.

[0003]

SUMMARY OF THE INVENTION Therefore, the present invention aims to reduce the variation in the performance characteristics of the variable capacity turbocharger in the variable capacity turbocharger of the internal combustion engine and to improve the reliability of the vanes (compartment walls). To
This is a technical issue.

[0004]

A first technical means for solving the above-mentioned problems is to provide a shaft, a turbine rotor fixed to one end of the shaft, a turbine rotor, and an exhaust inlet. An exhaust outlet, the turbine inlet having the exhaust inlet and the exhaust outlet communicated with each other via the turbine rotor, and a turbine housing having a scroll portion whose cross-sectional area is gradually reduced, and fixed to the other end of the shaft,
A compressor rotor housed in a compressor housing and the turbine housing are provided to divide the scroll portion in a radial direction into an inner peripheral scroll portion and an outer peripheral scroll portion, and exhaust gas flowing through the outer peripheral scroll portion to the inner peripheral scroll. Partition wall having a plurality of communication holes that regulate the flow velocity of exhaust gas flowing into the inner peripheral scroll portion and flowing through the inner peripheral scroll portion, and an inflow provided on the exhaust inlet side of the outer peripheral scroll portion. In a variable capacity turbocharger having a control valve that opens and closes an opening to control the flow rate of exhaust gas to the scroll parts, the partition walls are formed as a plurality of members separate from the turbine housing that is cast. Of vanes, the plurality of vanes being formed in the turbine housing during casting of the turbine housing. It is to be molded.

According to the above-mentioned means, the vane was conventionally cast integrally with the turbine housing, but it can be formed as a separate body, and high precision molding such as metal injection molding, lost wax molding and machining is performed. Can be adopted. Therefore, it is possible to improve the reliability of the vane with respect to thermal expansion, reduce the variation in performance, and improve the performance. Also,
The housing mold can be simplified, the flow of molten metal can be improved, defective products can be reduced, casting precision can be improved, and cost can be reduced.

A second technical means for solving the above-mentioned problem is that the vane has both axial end portions of the shaft cast into the turbine housing.

According to the above-mentioned means, both ends of the vane are cast into the turbine housing, so that the vane is supported by the both ends and the strength is secured, and at the same time, leakage due to the gap between the vane end and the turbine housing is prevented. It can be prevented and performance can be secured.

A third technical means for solving the above-mentioned problems is that the vane is made of a different material different from that of the turbine housing.

According to the above means, by selecting a different kind of material for the vane, for example, a high temperature resistant vane material, stress concentration due to thermal expansion can be prevented and quality and reliability can be improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS. 1 and 2 show a variable capacity turbocharger 1 according to an example of the present invention. The variable capacity turbocharger 1 is composed of a turbine section 20 and a compressor section 30 which are connected to each other via a bearing section 10. ing.

The bearing portion 10 includes a bearing housing 11
And a shaft 13 rotatably supported in the bearing housing 11 via a bearing 12, and the shaft 13 has left and right end portions protruding from the bearing housing 11. One end of the shaft 13 faces the inside of the turbine housing 21 that constitutes the turbine unit 20, and the other end of the shaft 13 faces the inside of the compressor housing 31 that constitutes the compressor unit 30. A turbine rotor 22 forming a turbine unit 20 is integrally rotatably joined to one end of the shaft 13, and a compressor rotor 32 forming a compressor 30 is integrally rotatably assembled to the other end of the shaft 13. It is attached.

The turbine section 20 is a turbine housing 2.
1 and a turbine rotor 22 located inside the turbine housing 21.
Is attached to one side of a bearing housing 11 that constitutes the bearing portion 10. The turbine rotor 22 passes through one side of the bearing housing 11 and faces the shaft 13.
Is integrally rotatably joined to one end of the turbine housing 21 and is located in an exhaust passage (passage) formed in the turbine housing 21.

The turbine housing 21 has an exhaust gas inlet (exhaust gas inlet) 21a and an exhaust gas exhaust port (exhaust gas outlet) 21b, and an exhaust passage is formed between the exhaust gas exhaust port 21a and the exhaust gas exhaust port 21b. An introduction wall 27 and a partition wall 23 are provided upstream of the position where the turbine rotor 22 is disposed in the exhaust passage. The introduction wall 27 and the partition wall 23 are
A portion of the exhaust passage on the upstream side of the arrangement position of the turbine rotor 22 is divided into an inner scroll portion 24 and an outer scroll portion 25. The partition wall 23 has a plurality of vanes 2
9a and a communication hole 29c, as shown in FIGS. 3 and 4, each of the vanes 29a is fixed to the turbine housing 21 by casting both axial end portions of the shaft 13 of the vane 29a. As a result, the vane 29a is supported by both ends to secure the strength, and the vane 29a
Leakage due to the gap between the end a and the turbine housing 21 can be prevented, the airtightness between the inner peripheral scroll portion 24 and the outer peripheral scroll portion 25 can be secured, and the performance can be secured. By forming the vane 29a as a separate body, it can be molded with high precision by metal injection molding, lost wax molding, machining processing, or the like. In addition, compared with the conventional cast molding vane shown in FIG.
The surface roughness of the vane 29a can be made smooth as in the embodiment of the present invention shown in FIG. 3, the variation in the dimension due to the deviation of the mold can be reduced, the minimum R can be made small, and the porosity can be eliminated. Can be improved and the performance can be improved. Further, as the vane 29a, a different material different from the turbine housing 21 such as a high temperature resistant vane material can be selected. Thereby, stress concentration due to thermal expansion can be prevented, and quality and reliability can be improved. The communication hole 29c is formed such that the upstream side thereof has a gentle inclination shape and the downstream side thereof has a tight inclination shape, and is oriented at a predetermined inclination angle toward the axial center of the turbine rotor 22.

In the turbine section 20, a control valve 26 is arranged on the exhaust gas inlet 21a side of the turbine housing 21. The control valve 26 controls the degree of opening of the inflow opening 25 a (valve opening) of the outer peripheral scroll portion 25, and its tip end is seated on the valve seat portion at the tip end of the introduction wall 27. The control valve 26 is in this state the outer peripheral scroll portion 2
The inflow opening 25a of No. 5 is closed, and the opening / closing operation is controlled by operating means (not shown) according to the rotation speed of the engine.

The compressor section 30 is provided with a compressor housing 31 and a compressor rotor 32 located inside the compressor housing 31, and the compressor housing 31 corresponds to the bearing housing 11 constituting the bearing section 10. It is installed on the other side. The compressor rotor 32 is integrally rotatably assembled to the other end side of the shaft 13 which penetrates the other side of the bearing housing 11 and faces the compressor housing 31.
It is located in the intake passage formed inside.

The compressor housing 31 has a compressor inlet 31a and a compressor outlet 31b. The compressor housing 31 is provided between the compressor inlet 31a and the compressor outlet 31b.
An annular scroll portion 33 is formed along the outer periphery of
The scroll portion 33 forms a compressor passage.
The scroll portion 33 is formed in a tapered shape from a position adjacent to the compressor discharge port 31b toward the compressor introduction port 31a side.

Next, the operation of the variable capacity turbocharger 1 described above will be described.

In the variable capacity turbocharger 1,
It operates by introducing the exhaust gas from the engine into the exhaust passage through the exhaust introduction port 21a of the turbine housing 21 that constitutes the turbine unit 20, and the compressor unit 30 generates a set supercharging pressure. Is supplied to the intake port of the engine (not shown).

In the variable displacement turbocharger 1, the inflow opening 25a of the outer peripheral scroll portion 25 is closed by the control valve 26 in the low speed region of the engine with a small displacement, and is introduced through the exhaust gas introduction port 21a of the turbine housing 21. The exhaust gas flows into the inner peripheral scroll portion 24. The exhaust gas flowing through the inner peripheral scroll portion 24 strikes the turbine rotor 22 from the tangential direction of the turbine rotor 22, and rotates the turbine rotor 22 efficiently. Then, the exhaust gas is discharged to an exhaust pipe (not shown) through the exhaust gas discharge port 21b. During this period, the shaft 13 is rotated by the rotation of the turbine rotor 22, and the compressor rotor 32 is rotated. As a result, the atmosphere is introduced into the intake passage of the engine (not shown) from the compressor introduction port 31a of the compressor housing 31, is compressed by the compressor rotor 32, and becomes the supercharging pressure according to the rotation speed of the variable capacity turbocharger 1, The high-density intake air is introduced into the intake port of the engine through the compressor discharge port 31b.

As a result, the variable capacity turbocharger 1
Functions as a turbocharger having a small volume having the volume of the inner scroll portion 24, and can efficiently rotate the turbine rotor 22 even with a small amount of exhaust gas.

On the other hand, in the medium speed range or high speed range of the engine where the displacement is large, the inflow opening 25a of the outer peripheral scroll portion 25 is opened by the operation of the control valve 26 in accordance with the rotation speed of the engine, and the turbine housing 21 is closed. Exhaust gas inlet 2
The exhaust gas introduced through 1a flows into both the inner peripheral scroll portion 24 and the outer peripheral scroll portion 25, and the exhaust gas that flows into the inner peripheral scroll portion 24 rotates the turbine rotor 22 in the same manner as described above to set the exhaust gas exhaust port 21b. After that, it is discharged to the exhaust pipe.

During this time, the exhaust gas that has flowed into the outer peripheral scroll portion 25 flows into the inner peripheral scroll portion 24 through each communication hole 29c of the partition wall 23. In this case, the inflow direction of the exhaust gas to the inner peripheral scroll portion 24 is the direction along the directing direction of each communication hole 29c, that is, the direction toward the axial center of the turbine rotor 22. The flow of exhaust gas flowing in the inner peripheral scroll portion 24 hits the turbine rotor 22 from the tangential direction of the turbine rotor 22 as described above, but due to the flow of exhaust gas flowing from the outer peripheral scroll portion 25 into the inner peripheral scroll portion 24, The flow velocity of the exhaust gas flowing through the inner peripheral scroll portion is regulated and changed to a flow toward the rotation center of the turbine rotor 22. Further, the velocity of the exhaust flow that hits the turbine rotor 22 also decreases. As a result, the rotation of the turbine rotor 22 is controlled so as to prevent the compressor rotor 32 from rotating more than necessary, and the boost pressure is set to the set supercharging pressure even in a region where the engine displacement is large in the medium speed region or the high speed region. The turbine rotor 22 can be controlled and efficiently rotated.

By the way, in the variable capacity turbocharger 1, the capacity of the inner peripheral scroll portion 24 and the scroll cross-sectional area are set small, and the capacity of the outer peripheral scroll portion 25 and the scroll cross-sectional area are set large, depending on the operating condition of the engine. And has a variable range by controlling the amount of exhaust gas flowing into the inner scroll portion and the outer scroll portion,
Although an efficient variable capacity turbocharger is configured, the scroll cross section of the inner scroll section 24 is similar from the scroll start point position (A) to the predetermined scroll position (B) of the inner scroll section 24. Between the predetermined scroll position (B) and the scroll end position (C), while maintaining the axial length of the inflow port 24a of the inner peripheral scroll portion 24 to the turbine rotor 22 in the radial direction. It is configured to be gradually reduced.

Due to the shape of the scroll cross section of the inner peripheral scroll portion 24, the axial length of the cross section of the inner peripheral scroll portion is smaller than the axial length of the outlet 24a of the inner peripheral scroll portion 24 to the turbine rotor 22. This can be prevented from occurring even between the scroll predetermined position (B) and the scroll end position (C).
The exhaust gas flowing through No. 4 can smoothly flow without hindering the flow of the exhaust gas into the turbine rotor 22. Accordingly, the resistance of the inner scroll portion 24 can be reduced and the efficiency of the variable capacity turbocharger 1 can be improved. Further, in the variable capacity turbocharger 1, the axial length of the communication hole 29c is set to the outlet of the inner peripheral scroll portion 24 to the turbine rotor 22 between the predetermined scroll position (B) and the scroll end position (C). Since the length coincides with the axial length of 24a, the exhaust gas can smoothly flow from the outer peripheral scroll portion 25 to the inner peripheral scroll portion 24 without hindering it.

7 and 8 show a second embodiment of the present invention. In the second embodiment, one end of each of the plurality of vanes 29a is integrally formed with the pedestal 29b to form the partition member 29. The pedestal portion 29b of the partition member 29 and the other end of the vane 29a are cast and fixed to the turbine housing 21 to form a partition wall 23 including a plurality of vanes 29a and communication holes 29c. Accordingly, when the vane 29a is cast and formed on the turbine housing 21, a plurality of vanes 29a can be set at one time by setting the partition member 29 in a housing mold (not shown), and the vane 29a can be easily handled. It is possible to improve productivity. Also in this second embodiment,
By forming the partition member 29 as a separate body, it is possible to perform molding with high precision by metal injection molding, lost wax molding, machining molding, or the like. Further, by these molding methods, surface roughness can be made smoother than that of conventional cast molding vanes, dimensional variation due to mold misalignment can be reduced, minimum R can be made small, and voids can be eliminated. Therefore, it is possible to improve reliability and performance. Further, for the partition member 29, a different material different from that of the turbine housing 21 such as a high temperature resistant vane material can be selected. Thereby, stress concentration due to thermal expansion can be prevented, and quality and reliability can be improved. The second embodiment is the same as the first embodiment except that the partition member 29 is different.

9 and 10 show a third embodiment of the present invention. In this third embodiment, the plurality of vanes 29
Each one end of a forms a plurality of partition members 29A integrally formed with the pedestal portion 29Ab. The pedestal portion 29Ab of the partition member 29A and the other end portion of the vane 29a are cast into the turbine housing 21 and fixed to the pedestal portion 29Ab.
The partition wall 23 is formed by a and the communication hole 29c. Thus, by using a plurality of partition members 29A, it is possible to reduce the distortion of the partition member 29A, it is possible to easily set the partition member 29A in a housing mold (not shown) at the time of casting molding of the turbine housing 21. Productivity can be improved. Also in the third embodiment, by forming the partition member 29A as a separate body, it is possible to perform molding with high precision by metal injection molding, lost wax molding, machining processing, or the like. Further, by these molding methods, surface roughness can be made smoother than that of conventional cast molding vanes, dimensional variation due to mold misalignment can be reduced, minimum R can be made small, and voids can be eliminated. Therefore, it is possible to improve reliability and performance. Further, the partition member 29A includes the turbine housing 21.
Different materials such as high temperature resistant vane materials can be selected. Thereby, stress concentration due to thermal expansion can be prevented, and quality and reliability can be improved. In addition,
The third embodiment is the same as the first embodiment except that the partition member 29A is different.

[0027]

As described above, according to the technical means taken in the invention of the above-mentioned claim 1, the vane is conventionally cast integrally with the turbine housing, but can be formed separately. High precision molding such as metal injection molding, lost wax molding and machining can be adopted. Therefore, it is possible to improve the reliability of the vane with respect to thermal expansion, reduce the variation in performance, and improve the performance. In addition, the housing mold can be simplified, the flow of molten metal can be improved, defective products can be reduced, casting precision can be improved, and cost can be reduced.

According to the technical means taken in the invention of claim 2, the both ends of the vane are cast into the turbine housing so that the vane is supported by the both ends and the strength is secured. Leakage due to a gap between the vane end and the turbine housing can be prevented, and performance can be secured.

According to the technical means taken in the third aspect of the present invention, by selecting a different material for the vane, for example, a high temperature resistant vane material, stress concentration due to thermal expansion can be prevented, and quality and reliability can be prevented. It is possible to improve the sex.

[Brief description of drawings]

FIG. 1 shows an axial sectional view of a variable capacity turbocharger according to a first embodiment of the present invention.

FIG. 2 shows a front view of the turbine section 20 taken along the line − shown in FIG. 1 of the present invention.

FIG. 3 is an enlarged cross-sectional view of a main part of a vane 29a according to the first embodiment of the present invention.

FIG. 4 shows a plan view of a vane 29a according to the first embodiment of the present invention.

FIG. 5 shows an enlarged plan view of a vane in the prior art.

FIG. 6 shows an enlarged plan view of a vane 29a according to the first embodiment of the present invention.

FIG. 7 is a partition member 29 according to the second embodiment of the present invention.
An enlarged sectional view of a main part of the (vane 29a) is shown.

FIG. 8 shows a plan view of a partition member 29 according to a second embodiment of the present invention.

FIG. 9 is a partition member 29A according to a third embodiment of the present invention.
An enlarged sectional view of a main part of the (vane 29a) is shown.

FIG. 10 is a partition member 29 according to a third embodiment of the present invention.
The top view of A is shown.

[Explanation of symbols]

1 ... Variable capacity turbocharger 10 ... Bearing part 11 ... Bearing housing 12 ... Bearing 13 ... Shaft 20 ... turbine 21 ... Turbine housing 21a ... Exhaust gas inlet (exhaust gas inlet) 21b ... Exhaust exhaust port (exhaust outlet) 22 ... Turbine rotor 23 ... Partition wall 24 ... Inner scroll part (scroll part) 24a ... outlet 25 ... Peripheral scroll part (scroll part) 25a ... inflow opening 26 ... Control valve 29a ... Vane 29c ... communication hole 30 ... Compressor 31 ... Compressor housing 32 ... Compressor rotor

Claims (3)

[Claims] 1. A shaft, a turbine rotor fixed to one end of the shaft, a turbine rotor, and an exhaust inlet, an exhaust outlet, and the exhaust inlet and the exhaust outlet via the turbine rotor. A turbine housing that is in communication with a scroll portion that has a cross-sectional area that gradually decreases, a compressor rotor that is fixed to the other end of the shaft and is housed in a compressor housing, and a turbine housing that is provided in the turbine housing. A plurality of communication holes that divides the inner peripheral scroll portion into an inner peripheral scroll portion and the outer peripheral scroll portion, and exhaust gas flowing through the outer peripheral scroll portion flows into the inner peripheral scroll portion to regulate the flow velocity of the exhaust gas flowing through the inner peripheral scroll portion. A partition wall having, and disposed on the exhaust inlet side of the outer peripheral scroll portion and on the exhaust inlet side. In a variable capacity turbocharger having a control valve that opens and closes a column inlet opening to control an exhaust flow rate to both scroll portions, the partition wall is formed as a separate member from the turbine housing that is cast. A variable capacity turbocharger, comprising a plurality of vanes, the plurality of vanes being integrally molded with the turbine housing during casting of the turbine housing. 2. The variable capacity turbocharger according to claim 1, wherein both end portions of the vane in the axial direction of the shaft are cast into the turbine housing. 3. The variable capacity turbocharger according to claim 1, wherein the vane is made of a different material different from that of the turbine housing.