JP2000291441A - Impeller of turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently improve durability, regardless of the difference of the temperature states by each part. SOLUTION: Intake air passing through a compressor impeller 12 in the operation of a turbocharger is thermally insulated and compressed by a compressor blade 12, and the temperature rises toward the discharge side, and therefore the temperature of the outer peripheral part to equivalent to the discharge side of the compressor impeller 11 is increased. The outer peripheral part of the compressor impeller 11 which becomes high in temperature to be raised is selectively formed of a material superior in high temperature strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a turbocharger impeller connected between an intake passage and an exhaust passage of an internal combustion engine.

[0002]

2. Description of the Related Art As is well known, a turbocharger for supercharging an internal combustion engine is provided with a turbine impeller and a compressor impeller which are connected by a shaft and rotate integrally. The rotation of the turbine impeller due to the exhaust of the internal combustion engine is transmitted through the shaft to rotate the compressor impeller. By rotating the compressor impeller in this manner, air is compressed by the compressor blades (blades) of the compressor impeller, and the compressed air is forcibly sent to the cylinder of the engine. In the turbocharger, the output of the internal combustion engine is improved by performing supercharging using the energy of the exhaust gas.

[0003] In such a turbocharger, the turbine impeller and the compressor impeller are usually used under severe conditions of high-speed rotation. Therefore, the impeller is required to have extremely high durability.

[0004] Conventionally, as a technique for improving the durability of such an impeller, for example, Japanese Patent Application Laid-Open No. 1-147118 is disclosed.
The publication describes that only the sliding portion of a blade (blade) of an impeller made of a light alloy material is made of fiber-reinforced metal. Thus, by using fiber reinforced metal for the sliding contact portion of the blade of the impeller, wear and deformation of the blade due to sliding contact can be prevented.

[0005]

However, the impeller described above is not limited to the wear and deformation of the sliding contact portion of the blade.
It has been confirmed by the inventors that the durability is also reduced by the factors described below.

FIG. 3 shows a partial cross-sectional structure of a compressor impeller portion of a turbocharger, and a stress distribution, a temperature distribution, and a material strength distribution corresponding to the same structure of the impeller portion during driving (during rotation). It is.

Here, as shown in FIG. 3A, the rotation of a turbine impeller (not shown) caused by blowing exhaust gas is
The power is transmitted to the compressor impeller 111 through the shaft 115. When the compressor impeller 111 is rotated in this manner, air is sent out as indicated by an arrow in FIG. 3A while being compressed by the compressor blade 112 of the compressor impeller 111.

At this time, a centrifugal force due to the rotation acts on the compressor impeller 111. That is, the compressor impeller 111 along the line B in FIG.
As shown in FIG. 3B, the stress distribution acting on the compressor impeller 111 based on the centrifugal force becomes smaller toward the outer periphery. However, the outer periphery of the compressor impeller 111 has a thinner disk portion and is also subjected to bending due to centrifugal force applied to the wing portion, so that a relatively large stress acts on this outer periphery as shown in FIG. I have.

On the other hand, when the compressor impeller 111 rotates, the intake air is adiabatically compressed by the compressor blade 112, so that the temperature increases from the suction side to the discharge side. That is, FIG.
As shown in FIG. 3C, the temperature distribution of the cross section of the compressor impeller 111 along the line B of FIG. Becomes

At this time, B in FIG.
As shown in FIG. 3 (d), the intensity distribution of the material constituting the compressor impeller 111 in the cross section along the line is as shown in FIG. 3 (d). The temperature is lower on the outer peripheral side of the compressor impeller 111 corresponding to the discharge side where the temperature becomes high. However, as shown in FIG. 3B, the stress applied thereto is relatively high even on the outer peripheral side.
As a starting point, damage due to fatigue, creep, or the like is likely to occur.

If the compressor impeller 111 is formed of a material having high strength under high-temperature conditions, the durability of such a high-temperature portion can be improved. However, such materials with high high-temperature strength generally have poor toughness and are expensive. For this reason, there are many issues regarding reliability other than high-temperature fatigue strength in the compressor impeller 111, and the manufacturing cost increases.

Further, as the rotational speed of the compressor impeller 111 increases, the temperature of the discharge-side portion increases, and the stress acting as the centrifugal force increases also increases. For this reason, if the durability of the compressor impeller 111 cannot be sufficiently ensured, the rotational speed of the impeller 111 is limited, and the performance as a turbocharger is naturally limited.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to improve the durability of a turbocharger impeller which can more efficiently improve the durability irrespective of the difference in temperature between parts. Is to provide.

[0014]

According to one aspect of the present invention, there is provided an impeller provided in a turbocharger connected between an intake passage and an exhaust passage of an internal combustion engine. The gist of the present invention is that the high-temperature strength is selectively enhanced in a portion on the side where the temperature gradient is high, of the portion on the inflow side and the portion on the gas discharge side.

According to the above configuration, of the gas inlet side and the gas outlet side of the impeller, the part having the higher temperature gradient, that is, the part having the higher temperature, has improved durability under high temperature conditions. . By selectively strengthening the impeller in accordance with the temperature state of each part of the impeller during the operation of the turbocharger, the durability of the entire impeller can be more efficiently improved.

The invention described in claim 2 is the first invention.
In the impeller of the turbocharger described in the above, the impeller is a compressor impeller provided on the side connected to the intake passage of the turbocharger,
The gist is that the portion for selectively enhancing the high-temperature strength is a portion on the gas outflow side.

In a turbocharger, a compressor impeller compresses and sends out the intake air that flows in. At this time, since the intake air is adiabatically compressed, its temperature increases toward the gas (intake air) outlet side of the compressor impeller. With the temperature rise of this intake air,
The internal temperature of the compressor impeller also becomes higher at the outflow side.

In this regard, according to the above configuration, the high-temperature strength of the portion of the compressor impeller on the gas (intake air) outflow side where the temperature becomes high is selectively enhanced, so that the durability of the entire compressor impeller is more efficient. Will be improved.

Further, the invention described in claim 3 is the first invention.
The impeller of a turbocharger according to claim 1, wherein the impeller is a turbine impeller provided on a side of the turbocharger connected to the exhaust passage, and the portion for selectively enhancing the high-temperature strength includes a gas inlet. The gist is that it is the side part.

In a turbocharger, a turbine impeller is rotated by blowing hot exhaust gas discharged from an internal combustion engine. For this reason, during operation of the turbocharger, the portion on the gas (exhaust) inflow side of the turbine impeller that receives high-temperature exhaust gas has a particularly high temperature.

In this regard, according to the above configuration, the high-temperature strength of the portion on the gas (exhaust) inflow side of the turbine impeller, to which high-temperature exhaust gas is blown, is selectively enhanced.
The durability of the entire turbine impeller is more efficiently improved.

The invention described in claim 4 is the first invention.
In the turbocharger impeller according to any one of (1) to (3), the gist is that the selective enhancement of the high-temperature strength is performed by selecting a material forming the portion.

According to the above configuration, the portion where the temperature gradient is high in the impeller is selectively formed of a material having high strength at high temperature. For this reason, the durability of the same portion under high temperature conditions is improved. In general, a material having high strength at high temperatures has relatively low toughness and is brittle, and thus does not have very high durability under conditions other than high temperature conditions. Therefore, by selectively using such a material only in the portion where the temperature is high, it is possible to increase the durability of the portion where the temperature is high while maintaining the durability of the portion other than the portion where the temperature is high. For this reason, the durability of the entire impeller can be more efficiently improved.

The invention described in claim 5 is the same as the invention in claim 4.
The impeller of a turbocharger according to claim 1, wherein the impeller is formed based on an aluminum alloy, and the portion for selectively strengthening high-temperature strength has a higher content of copper and silicon than other portions. The gist is to use an aluminum alloy.

According to the above-described structure, the high temperature portion has a higher content of copper and silicon than the other portions, so that
The high-temperature strength is increased, and the durability at the time of operating the turbocharger is improved. Although the high temperature portion and the other portions have different compositions of components, since both are formed based on an aluminum alloy, it is easy to ensure the bondability at the boundary between these two portions.

The invention according to claim 6 is the first invention.
4. The turbocharger impeller according to any one of items 1 to 3, wherein the selective enhancement of the high-temperature strength is performed by coating a heat insulating material film on a surface of the portion.

According to the above configuration, by coating the surface of the portion where the temperature becomes high during the operation of the turbocharger with the heat insulating material coating, the temperature rise inside the portion covered with the coating of the impeller is suppressed, and the strength is maintained. Will be done.
Therefore, the durability of the high-temperature portion is ensured, and the durability of the entire impeller is more efficiently improved.

The invention described in claim 7 is the same as the invention in claim 6
In the impeller of a turbocharger described in the above, the gist is that the heat insulating material coating is a ceramic coating. According to the above configuration, by coating the surface of the portion that becomes high temperature during the operation of the turbocharger with a coating made of ceramics, which is an excellent heat insulating material, the rise in the internal temperature of the portion covered with this coating is more efficiently suppressed. Will be done.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a turbocharger impeller according to the present invention will be described below.
This will be described in detail.

FIG. 1 shows a cross-sectional side view of a turbocharger employing an impeller according to the present embodiment. As shown in FIG. 1, the turbocharger 10 has a turbine impeller 13 that receives and rotates exhaust gas, and a compressor impeller that is rotated by the turbine impeller 13 to compress intake air and send it to a cylinder (not shown) of the engine. 11 are provided. The turbine impeller 13 and the compressor impeller 11 are connected so as to rotate integrally by a shaft 15 rotatably supported in the turbocharger 10. In the present embodiment, the shaft 15 is joined to the turbine impeller 13 by welding.

A scroll passage 33 extending spirally around the outer periphery of the turbine impeller 13 is formed in the turbine housing 30 in which the turbine impeller 13 is accommodated. Exhaust gas discharged from the internal combustion engine is introduced into the scroll passage 33. Then, the exhaust gas obtained the rotational force by the scroll passage 33, as indicated by an arrow in FIG.
Inlet 32 formed on the inner surface of scroll passage 33
Through the turbine impeller 13 to a turbine blade (blade) 14. The exhaust thus blown causes the turbine impeller 13 to rotate. The exhaust blown to the turbine impeller 13 is discharged through a discharge port 31 opened on the front side of the turbine impeller 13.

On the other hand, the compressor impeller 11 is housed inside a compressor housing 20. In the compressor housing 20, on the front side of the compressor impeller 11, an intake port 2 for introducing intake air is provided.
1 is formed. In the compressor housing 20, on the outer periphery of the compressor impeller 11,
A spirally extending compressor passage 23 is formed. The compressor passage 23 is connected to a discharge port 22 that opens on the outer periphery of the compressor impeller 11.

When the rotation of the turbine impeller 13 is transmitted through the shaft 15 and the compressor impeller 11 is rotated, the intake air is sucked through the suction port 21. The intake air thus sucked is compressed by the compressor blade 12 provided in the compressor impeller 11, and is forcibly sent to the compressor passage 23 through the discharge port 22. The intake air sent into the compressor passage 23 is sent to a cylinder (not shown) of the internal combustion engine, and supercharging of the engine is performed.

On the other hand, in the turbocharger 10 of the present embodiment, the compressor impeller 11 is formed by casting two kinds of materials. With such a structure, the durability of the compressor impeller 11 is improved.

Hereinafter, such a compressor impeller 11 will be described.
And a method of manufacturing the same will be described in detail with reference to FIG. FIG. 2A partially shows a side cross section of the compressor impeller 11.

As shown in FIG. 2A, the outer peripheral portion of the compressor impeller 11 corresponding to the discharge side of the intake air exhibits relatively high strength even at a high temperature, and is excellent in durability under high temperature conditions. Is formed by On the other hand, the portion of the compressor impeller 11 other than the outer peripheral portion is inferior in durability under high temperature conditions as compared with the material of the outer peripheral portion, but is rich in toughness and the like. It is formed of a material having higher durability. In the following description, the material of the outer peripheral portion is referred to as “high-temperature high-strength material”, and the other material is referred to as “high-toughness material”.

In this embodiment, the base material of each of the two materials is an aluminum alloy, and each has the following composition. First, the composition of the “high toughness material” is (Cu: 1.0 to 1.5, Si: 4.5 to 5.5, Mg: 0.4 to
0.6, Fe: 0.2 or less, Mn: 0.1 or less, Al: balance). On the other hand, the composition of the “high-temperature high-strength material” is (C
u: 4.5 to 5.5, Si: 5.0 to 7.0, Mg: 0.2 to 0.4, F
e: 0.5 or less, Mn: 0.1 to 0.4, Al: balance). Here, each numerical value indicates the weight percentage of each component contained in the material.

As shown here, “high-temperature high-strength material” is different from “high-toughness material” in that Cu (copper) and Si (silicon) are used.
Is increased, and such a composition enhances the strength under high-temperature conditions.

The compressor impeller 11 is manufactured as follows. First, after casting only the outer peripheral portion of the compressor impeller 11 using the “high-temperature high-strength material”, the other portions are cast using the “high-toughness material”. Both of these materials are aluminum alloys and their melting points are relatively close. At this time, a part of the “high-temperature high-strength material” on the outer periphery is melted and newly cast “high-toughness material”. Will be mixed. As a result, the boundary between the two materials is tough and joined without any seam.

Also, at the boundary between the two materials, the components of the two materials gradually change. Therefore, this boundary portion has characteristics as a functionally graded material in which the characteristics of both materials gradually change.

Thus, the compressor impeller 11
Is formed such that only the outer peripheral portion on the discharge side of the intake air becomes a material having excellent strength under high temperature conditions. Hereinafter, the characteristics of the compressor impeller 11 thus formed will be described with reference to FIGS. 2B and 2C.

FIG. 2B shows a temperature distribution during operation of the turbocharger 10 in a cross section of the compressor impeller 11 along the line A in FIG. 2A. FIG. 2C also shows the durability of the material forming the compressor impeller 11 when the turbocharger 10 is operating, in a cross section along the line A in FIG. 2A.

As described above, the compressor impeller 1
In 1, the compressor blade 12 adiabatically compresses the intake air with the operation of the turbocharger 10, so that the outer peripheral side corresponding to the discharge side becomes higher in temperature, as shown in FIG. Since the strength of the above-mentioned "high toughness material" greatly decreases as the temperature rises, as shown in FIG. 2 (c), the durability decreases greatly as the temperature approaches the discharge side of the compressor impeller 11 where the temperature becomes high. On the contrary,
Since the “high-temperature, high-strength material” retains relatively high strength even at high temperatures, as shown in FIG. 2C, the discharge side of the compressor impeller 11 at a high temperature is higher than the “high-toughness material”. Also show high durability.

In the present embodiment, only the discharge side of the compressor impeller 11, which is heated to a high temperature, is the "high-temperature high-strength material".
Thus, high durability is maintained both on the discharge side where the temperature is high and on other parts where the temperature is not as high as the discharge side. For this reason, the durability of the compressor impeller 11 as a whole is greatly improved.

As described above, according to the present embodiment, the following effects can be obtained. (1) By forming only the discharge side of the compressor impeller 11, which becomes high in temperature, from a material having excellent durability under high temperature conditions, it is possible to maintain high durability in other parts, which are not as high in temperature as the discharge side. In addition, it is possible to reduce a decrease in durability due to a high temperature on the discharge side. Therefore,
The durability of the compressor impeller 11 as a whole can be greatly improved.

(2) In addition, by improving the durability of the compressor impeller 11 in this way, it is possible to increase the rotational speed which is the limit of its use. (3) Further, with such a configuration, it is possible to reduce the weight of the compressor impeller 11 while maintaining durability. Also, by reducing the weight of the compressor impeller 11, the inertial mass of the impeller 11 during rotation can be reduced, the response can be improved, and the turbo lag can be reduced.

(4) Further, since the two types of materials constituting the compressor impeller 11 are both aluminum alloys, and by making their compositions different, suitable characteristics are provided according to the parts used for each. In addition, the joining property at the boundary between the two materials can be made very high.
Therefore, the strength and durability of the compressor impeller 11 as a whole can be kept high.

(5) By casting the above two types of materials, the compressor impeller 11 composed of these two types of materials can be easily formed. Further, by forming in this manner, it is also possible to enhance the joining property at the boundary between the two materials.

The impeller of the turbocharger according to the present embodiment described above can be modified as follows. In the above-described embodiment, the outer peripheral portion corresponding to the discharge side (discharge side) of the intake air that becomes hot in the compressor impeller 11 is formed of “high-temperature high-strength material”, and the high-temperature strength is enhanced. I have. However, depending on the configuration of the turbocharger, the exhaust side of the intake air, which becomes hot,
It may not correspond to the portion on the outer peripheral side of the compressor impeller 11. In such a case, an effect similar to that of the above-described embodiment can be obtained by appropriately changing a portion for enhancing the high-temperature strength according to the configuration of the turbocharger.

The choice of the two materials forming the compressor impeller 11, that is, the “high-temperature high-strength material” and the “high-toughness material” is arbitrary.
It is sufficient that the material of the portion which becomes high in temperature during the operation of the above is a material having excellent strength under high temperature conditions.

The method of enhancing the high-temperature strength of the portion that becomes hot during the operation of the turbocharger 10 is also optional. In addition to the method of selecting the material as in the above embodiment, for example, the surface of the reinforced portion The coating may be performed by coating a heat insulating material coating such as a ceramic material. In such a case, the rise in the internal temperature of the impeller in the portion where the coating is coated is suppressed,
Since the reduction in the strength is suppressed, the durability of the reinforced portion during the operation of the turbocharger can be improved.

In the above embodiment, the impeller according to the present invention is applied to a compressor impeller of a turbocharger. However, this may be applied to a turbine impeller. In this case, the gas (exhaust) of the turbine impeller that receives high-temperature exhaust during operation of the turbocharger
The high-temperature strength of the portion on the inflow side may be selectively enhanced.
In the turbocharger 10 of FIG. 1, the turbine impeller 1
3, the high-temperature strength of the portion on the outer peripheral side corresponding to the introduction port 32 into which the exhaust gas is introduced may be enhanced.

[0053]

According to the first aspect of the present invention, the durability of the entire impeller can be efficiently improved by selectively enhancing the high-temperature strength of a portion which becomes high in temperature when the turbocharger operates. Become like

According to the second aspect of the present invention, the durability of the entire compressor impeller is efficiently improved by selectively enhancing the high-temperature strength of the portion on the gas outflow side of the compressor impeller where the temperature is high. Will be able to

According to the third aspect of the present invention, the durability of the entire turbine impeller is efficiently improved by selectively enhancing the high-temperature strength of the portion on the gas inflow side of the turbine impeller to which high-temperature exhaust gas is blown. Can be improved.

According to the fourth aspect of the present invention, a material excellent in high-temperature strength is selectively used only in a portion where the temperature becomes high during operation of the turbocharger, so that a portion other than the portion where the temperature becomes high can be durable. While maintaining high performance, the durability of the high temperature portion can be increased, and the durability of the entire impeller can be efficiently improved.

According to the fifth aspect of the present invention, the high-temperature portion has a higher content of copper and silicon than other portions, so that the high-temperature strength is increased and the durability at the time of operating the turbocharger is improved. Performance can be improved. Moreover, although the material of the high temperature portion and the material of the other portion have different component compositions, since both are aluminum alloys,
It is also easy to ensure the bonding property at the boundary between these two materials.

According to the sixth aspect of the present invention, by coating the surface of the portion which becomes high in temperature during the operation of the turbocharger with the heat insulating material coating, the temperature rise inside the portion covered by the impeller coating can be prevented. Suppress and the strength is maintained. Therefore, the durability of the high-temperature portion is ensured, and the durability of the entire impeller can be efficiently improved.

According to the seventh aspect of the present invention, the surface of the portion which becomes high in temperature during the operation of the turbocharger is coated with a film made of ceramics which is excellent as a heat insulating material, so that the portion covered with the film can be formed. An increase in the internal temperature can be suppressed more efficiently.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a cross-sectional side structure of a turbocharger employing an impeller according to an embodiment of the present invention.

FIG. 2 is a view showing both a cross-sectional view showing a side cross-sectional structure of the compressor impeller of the embodiment and a graph showing a corresponding temperature distribution and the like.

FIG. 3 is a diagram showing a cross-sectional view illustrating a side cross-sectional structure of a conventional compressor impeller section and a graph illustrating a corresponding temperature distribution and the like.

[Explanation of symbols]

10 Turbocharger, 11, 111 Compressor impeller, 12, 112 Compressor blade, 13
... turbine impeller, 14 ... turbine blade, 15,
115: shaft, 20, 120: compressor housing, 21: suction port, 22: discharge port, 23: compressor passage, 30: turbine housing, 31: discharge port, 3
2. Inlet, 33 ... scroll passage.

Claims (7)

[Claims] An impeller provided in a turbocharger connected between an intake passage and an exhaust passage of an internal combustion engine, wherein an impeller on a gas inflow side and a gas discharge side has a higher temperature gradient. A turbocharger impeller characterized by selectively enhancing the high-temperature strength of parts. 2. The turbocharger impeller according to claim 1, wherein said impeller is a compressor impeller provided on a side of said turbocharger connected to said intake passage, and said selectively enhanced high-temperature strength. Wherein the portion to be applied is a portion on the gas outflow side. 3. The turbocharger impeller according to claim 1, wherein the impeller is a turbine impeller provided on a side of the turbocharger connected to the exhaust passage, and the selectively high-temperature strength is enhanced. Wherein the portion to be applied is a portion on the gas inflow side. 4. A turbocharger impeller according to claim 1, wherein said selective enhancement of high-temperature strength is performed by selecting a material forming said portion. Impeller. 5. The impeller of a turbocharger according to claim 4, wherein the impeller is formed on the basis of an aluminum alloy, and the portion where the high-temperature strength is selectively enhanced is compared with other portions. An impeller for a turbocharger, characterized by using an aluminum alloy having a high content of copper and silicon. 6. The turbocharger impeller according to claim 1, wherein the selective high-temperature strength enhancement is performed by coating a heat insulating material coating on a surface of the portion. Turbocharger impeller. 7. The impeller for a turbocharger according to claim 6, wherein the heat insulating material coating is a ceramic coating.