JP2007231934A - Turbocharger with variable nozzle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a turbocharger with a variable nozzle having a mechanism capable of maintaining temperature of a thrust bearing below critical temperature. <P>SOLUTION: This turbocharger with the variable nozzle is provided with a compressor impeller 4 rotated and driven by a turbine impeller 2 to compress air, a shaft 5 for connecting the turbine impeller 2 with the compressor impeller 4, a bearing housing 6 for supporting the shaft 5 rotatably, a turbine housing 7 for storing the turbine impeller 2 in the inside, and a variable nozzle mechanism 12 provided on a compressor impeller 4 side on an outer side in the radial direction of the turbine impeller 2 to adjust flow rate of exhaust gas flowing toward the turbine impeller 2. The bearing housing 6 is extended outward in the radial direction, is connected with the turbine housing 7 in an outward part in the radial direction, and has a diameter extended part 6a for storing the variable nozzle mechanism 12 between the turbine housing 7 and it. A heat shielding plate 21 for preventing heat transfer between the variable nozzle mechanism 12 and the diameter extended part 6a is provided between the diameter extended part 6a and the variable nozzle mechanism 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a turbocharger with a variable nozzle, and more particularly to a turbocharger with a variable nozzle having a mechanism capable of suppressing a temperature rise such as a thrust bearing on a compressor side.

  A turbocharger is a supercharger used for high output of, for example, an automobile engine. In the turbocharger, the turbine impeller is rotated by the exhaust energy of the engine, and the compressor impeller is rotated by the output of the turbine, whereby compressed air is supplied from the compressor to the engine. This brings the engine to a supercharged state that is higher than the natural intake.

  In this turbocharger, when the engine rotates at a low speed, the turbine hardly works due to a low exhaust flow rate. Therefore, in an engine that rotates to a high-speed rotation region, it takes time until the turbine rotates efficiently, and the turbo effect cannot be obtained quickly.

Therefore, a turbocharger with a variable nozzle (VGS (Variable Geometry System) turbocharger) that operates efficiently even in a low rotation range has been developed. This turbocharger with a variable nozzle is designed to obtain a high output even during low-speed rotation by narrowing a small exhaust flow rate with movable blades, increasing the exhaust speed, and increasing the amount of work of the turbine. Such a turbocharger with a variable nozzle is described in Patent Document 1, for example.
Japanese Patent Publication No. 7-13468 “Turbocharger”

  However, in a turbocharger with a variable nozzle, when the engine stops and the pressure oil that cools the bearing housing stops, heat is transferred from the turbine side of the bearing housing to the compressor side (heat soak) to the compressor side of the bearing housing. There was a problem that the temperature of the provided thrust bearing exceeded the limit temperature of 250 ° C and increased to about 300 ° C. Such a problem has not been pointed out particularly in a turbocharger without a variable nozzle.

  Accordingly, an object of the present invention is to provide a turbocharger with a variable nozzle in a turbocharger with a variable nozzle having a mechanism capable of maintaining the temperature of a thrust bearing or the like below a limit temperature.

  According to the present invention, in order to achieve the above object, a turbine impeller that is rotationally driven by exhaust gas, a compressor impeller that is rotationally driven by the turbine impeller and compresses air, and a shaft that connects the turbine impeller and the compressor impeller, , A bearing housing that rotatably supports the shaft, a turbine housing that houses the turbine impeller, and a variable compressor that is provided on the compressor impeller side radially outside the turbine impeller and adjusts the exhaust gas flow rate toward the turbine impeller A nozzle mechanism, and the bearing housing extends radially outward, is coupled to the turbine housing at a radially outer portion, and has an enlarged diameter portion that accommodates the variable nozzle mechanism with the turbine housing, There is a variable nozzle between the enlarged diameter part and the variable nozzle mechanism. Variable nozzle turbocharger, characterized in that the heat shield plate to prevent heat transfer between Le mechanism and the enlarged diameter portion is provided is provided.

  In a turbocharger with a variable nozzle, in order to accommodate the variable nozzle mechanism between the turbine housing and the bearing housing, the bearing housing has an enlarged diameter portion that extends radially and couples to a radially outer portion of the turbine housing. Therefore, the bearing housing becomes larger than before, and its heat capacity increases accordingly. The pressure oil cooling cannot cool the heat of the diameter-enlarged portion of the bearing housing. However, in the turbocharger with a variable nozzle according to the present invention, since a heat shield is provided between the variable nozzle mechanism and the diameter-enlarged portion of the bearing housing on the radially outer side, transmission from the turbine side to the diameter-enlarged portion is performed. Heat is prevented. In other words, by installing the heat shield plate with a space between the variable nozzle mechanism and the bearing housing, heat transfer is blocked so that the radiant heat of the turbine-side components that become high temperature does not directly heat the bearing housing. . As a result, heating of the diameter-enlarged portion of the bearing housing is suppressed, and as a result, even when the engine stops and the pressure oil for cooling the bearing housing stops, the temperature of the thrust bearing or the like can be maintained below the limit temperature. it can.

  According to a preferred embodiment of the present invention, the heat shield plate has a radially outer end sandwiched between the turbine housing and the bearing housing.

As a result, when the turbocharger is assembled, the heat shield plate can be fixed simply by sandwiching the heat shield plate between the turbine housing and the bearing housing, so that the heat shield plate can be easily fixed.
In addition, since the radially outer end portion of the heat shield plate is sandwiched between the turbine housing and the bearing housing, the radially outer end portion of the heat shield plate is brought into contact with the turbine housing and the bearing housing. A heat shield can be attached so that other parts do not contact the turbine housing and the bearing housing.
Therefore, even if heat transfer from the turbine side to the enlarged diameter portion of the bearing housing occurs through the contact portion at the radially outer end of the heat shield plate, the other portions of the heat shield plate are not in contact with each other. The amount of heat transferred from the turbine side to the enlarged diameter portion through this portion can be minimized. Therefore, heat transfer from the turbine side to the enlarged diameter portion can be more effectively prevented.

According to a preferred embodiment of the present invention, the heat shield plate is an annular member having an opening at the center,
The bearing housing has a reduced diameter portion that protrudes toward the turbine housing from the enlarged diameter portion and fits into the opening.

  As a result, when the turbocharger is assembled, the heat shield plate can be attached to the bearing housing simply by fitting the reduced diameter portion of the bearing housing to the opening portion of the heat shield plate. It is.

  Since the heat shield plate is provided between the variable nozzle mechanism and the enlarged diameter portion of the bearing housing, heat transfer from the turbine side to the enlarged diameter portion is prevented. As a result, heating of the diameter-enlarged portion of the bearing housing is suppressed, and as a result, even when the engine stops and the pressure oil for cooling the bearing housing stops, the temperature of the thrust bearing or the like can be maintained below the limit temperature. it can.

  A preferred embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a sectional view in the axial direction of a turbocharger 10 with a variable nozzle showing an embodiment of the present invention. FIG. 2 is an arrow diagram along line AA in FIG. 1 and shows the variable nozzle mechanism 12 that adjusts the exhaust gas flow rate from the engine to the turbine.

  A turbocharger 10 with a variable nozzle shown in FIG. 1 includes a turbine impeller 2 that is rotationally driven by exhaust gas from an engine, a compressor impeller 4 that is rotationally driven by a driving force of a turbine and supplies compressed air to the engine, and a turbine impeller 2. And a shaft housing 5 that couples the compressor impeller 4, a bearing housing 6 that rotatably supports the shaft 5, a turbine housing 7 that houses the turbine impeller 2 radially inward, and a compressor impeller 4 that accommodates the compressor impeller 4 radially inward. A compressor housing 8. An oil supply port 9a, an oil passage 9b, and an oil discharge port 9c for cooling the bearing housing 6 and the thrust bearing 3 are provided in the bearing housing 6.

  Inside the turbine housing 7, a scroll 11 into which exhaust gas from the engine is sent is formed. And the turbocharger 10 with a variable nozzle is further provided with the variable nozzle mechanism 12 which controls the flow volume of the exhaust gas sent into the scroll 11, and adjusts the exhaust gas flow volume to the turbine impeller 2 located inside radial direction.

  As shown in FIGS. 1 and 2, the variable nozzle mechanism 12 includes a plurality of movable blades 12 a arranged at intervals in the circumferential direction, and a first holding the movable blades 12 a so as to sandwich the movable blades 12 a in the axial direction. Engages the ring member 12b and the second ring member 12c, a plurality of transmission members 12e that are fixed to the roots of the shafts of the plurality of movable blades 12a and extend radially outward, and the radially outer ends of the transmission members 12e. And a third ring member 12d in which a plurality of grooves 14 are formed in the circumferential direction. As can be seen from FIG. 1, the variable nozzle mechanism 12 is provided on the compressor impeller 4 side on the radially outer side of the turbine impeller 2.

  By rotating the third ring member 12d in the circumferential direction by a cylinder (not shown) or the like, the groove 14 of the third ring member 12d is also moved in the circumferential direction, and a plurality of pieces respectively engaged with the groove 14 by this movement. The transmission member 12e swings in the circumferential direction, and accordingly, the movable blade 12a also swings. Thereby, the exhaust gas flow rate to the turbine impeller 2 is controlled by controlling the swing amount of the movable blade 12a.

  FIG. 3 is an enlarged view of a portion surrounded by a broken line B in FIG. As shown in FIGS. 1 and 3, the variable nozzle mechanism 12 is provided on the radially outer side of the turbine impeller 2, and the bearing housing 6 extends radially outward to attach the variable nozzle mechanism 12. It has an enlarged diameter portion 6a that is coupled to the outer end portion of the turbine housing 7 in the axial direction. The radially outer end of the enlarged diameter portion 6 a and the radially outer end of the turbine housing 7 are coupled in the axial direction by a bolt 17 using a coupling plate 16. The variable nozzle mechanism 12 has a mounting member 18 having one end 18a fixed to the second ring member 12c, and the other end 18b of the mounting member 18 is an outer end in the radial direction of the enlarged diameter portion 6a. And the radially outer end of the turbine housing 7. That is, the variable nozzle mechanism 12 is sandwiched between the turbine housing 7 and the bearing housing 6 by the mounting member 18. In this manner, the variable nozzle mechanism 12 is accommodated between the turbine housing 7 and the enlarged diameter portion 6 a of the bearing housing 6. The bearing housing 6 has a reduced diameter portion 6b having a small diameter at the turbine side end portion. An opening at the center in the radial direction of the third ring member 12d of the variable nozzle mechanism 12 is passed, and the third ring member 12d is attached to the reduced diameter portion 6b.

  As described above, in order to attach the variable nozzle mechanism 12 to the turbocharger, the bearing housing 6 is provided with the enlarged diameter portion 6a, so that the radial dimension of the bearing housing 6 is increased. If attention is paid to this point, the temperature of the thrust bearing of the turbocharger 10 with a variable nozzle that has risen above the limit temperature of 250 ° C. to about 300 ° C. will increase the size of the bearing housing 6 and its heat capacity. The cause is thought to have been. That is, in the conventional cooling structure using pressure oil, even if the bearing housing 6 is cooled during engine operation, the enlarged diameter portion 6a cannot be sufficiently cooled. For this reason, the diameter-expanded portion 6a is hotter than other portions (for example, the compressor side of the bearing housing 6). When the pressure oil stops after the engine is stopped, this heat is transmitted to the compressor side of the bearing housing 6 (heat soak), whereby the temperature on the compressor side of the bearing housing 6 rises, and the temperature of the thrust bearing 3 becomes the critical temperature 250. It is considered that the temperature has exceeded 300 ° C and has risen to about 300 ° C.

  In the present invention, based on the fact that the cause of the temperature increase of the thrust bearing is the increase in size of the bearing housing 6, the heat shield plate is provided by a method peculiar to the present application as described below.

According to the embodiment of the present invention, the heat shield plate 21 having the opening at the center in the radial direction is attached so that the cross section perpendicular to the axial direction is annular. As shown in FIG. 3, the heat shield plate 21 is attached to the bearing housing 6 by passing the reduced diameter portion of the bearing housing 6 through the opening of the heat shield plate 21. And the radial direction outer side edge part of this heat shield plate 21 is the radius of the radial direction outer side edge part of the turbine housing 7, and the diameter expansion part 6a with the other end part 18b of the above-mentioned attachment member 18, as shown in FIG. It is clamped between the direction outer side ends. Thereby, the heat shield 21 can be fixed between the turbine housing 7 and the bearing housing 6.
Further, by this fixing method, only the radially outer end portion of the heat shield plate 21 is brought into contact with the turbine housing 7 and the bearing housing 6, and the other portion of the heat shield plate 21 includes the turbine housing 7 and the bearing housing 6. It is possible to prevent contact with other members.

  In addition, as shown in FIG. 3, the communication hole 22 which makes the scroll 11 and the 2nd ring member 12c a communication state is provided. If the communication hole 22 is not provided, a pressure difference is generated between the scroll 11 side and the space between the second ring member 12c and the third ring member 12d with the second ring member 12c as a boundary. Thus, the exhaust gas flows into the space between the second ring member 12c and the third ring member 12d together with the unburned carbon of the fuel through the gap between the shafts of the movable blades 12a for a relatively long time. Carbon is clogged in the space between the ring member 12c and the third ring member 12d. When carbon accumulates in the sliding portion of the variable nozzle mechanism, there arises a problem that the sliding movement of the movable blade 12a is reluctant. Therefore, the communication hole 22 is provided to eliminate the pressure difference, and the flow through the gap between the shafts of the movable blades 12a from the scroll side to the space between the second ring member 12c and the third ring member 12d is relatively long. This makes it difficult to generate carbon and makes carbon boring. Further, the communication hole 22 has an effect of preventing carbon adhesion by eliminating the pressure and making the temperature of the variable nozzle mechanism portion uniform in a relatively short time. In consideration of this, in the embodiment of the present invention, the heat shield plate 21 is provided closer to the bearing housing 6 than the third ring member 12d. In addition, the code | symbol 23 has shown the heat shield conventionally attached.

  In addition, the material of the heat shield plate 21 is, for example, stainless steel such as SUS304 or SUS310 (JIS G 4305 or the like), but may be other suitable materials that can obtain a heat shield effect. In addition, the material of the heat shield plate 21 may be the same as the material of the heat shield plate 23 provided in another part.

  The heat shield plate 21 described above can prevent heat transfer between the turbine side and the enlarged diameter portion 6a of the bearing housing 6, and suppresses a temperature increase of the enlarged bearing housing 6 (particularly, the enlarged diameter portion 6a). it can. In addition, since the heat shield plate 21 can prevent cold heat from being transmitted from the bearing housing 6 to the turbine side, it is possible to prevent carbon from being deposited near the nozzle variable mechanism.

Further, since the radially outer end of the heat shield plate 21 is fixed between the turbine housing 7 and the bearing housing 6 together with the mounting member 18 of the variable nozzle mechanism 12, the heat shield plate 21 is fixed to the bearing housing 6. It can be easily mounted and fixed.
In addition, by this fixing method, the radially outer end of the heat shield plate 21 is brought into contact with the turbine housing 7 and the bearing housing 6, and other portions of the heat shield plate 21 are not brought into contact with the turbine housing 7 and the bearing housing 6. Therefore, the amount of heat transfer from the turbine side to the enlarged diameter portion through this non-contact portion can be minimized. Therefore, heat transfer from the turbine side to the enlarged diameter portion 6a can be more effectively prevented.

  In addition, this invention is not limited to embodiment mentioned above, Of course, a various change can be added in the range which does not deviate from the summary of this invention. For example, in the above-described embodiment, the turbocharger 10 with a variable nozzle that shields the radially outer end of the turbine housing 7 and the radially outer end of the enlarged diameter portion 6a of the bearing housing 6 by the bolts 17 is shielded. Although the plate 21 is applied, the turbine housing 7 and the bearing housing 6 are coupled at an appropriate location in the radially outer portion, and the turbocharger 10 that houses the variable nozzle mechanism 12 therebetween is also provided with a heat shield plate. 21 can be applied.

1 is an overall configuration diagram of a turbocharger with a variable nozzle according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1 and shows a variable nozzle mechanism. FIG. 2 is an enlarged view of a portion surrounded by a broken line B in FIG. 1.

Explanation of symbols

2 Turbine Impeller, 4 Compressor Impeller, 5 Shaft 6 Bearing Housing, 6a Expanded Part, 6b Reduced Part 7 Turbine Housing, 8 Compressor Housing 10 Turbocharger with Variable Nozzle, 11 Scroll, 12 Variable Nozzle Mechanism 12a Movable Blade, 12b First 1 ring member, 12c second ring member
12d Third ring member, 12e Transmission member, 14 Groove, 16 Coupling plate 17 Bolt, 18 Mounting member, 21 Heat shield plate, 23 Heat shield plate

Claims (3)

A turbine impeller driven by exhaust gas,
A compressor impeller that is rotationally driven by the turbine impeller and compresses air;
A shaft connecting the turbine impeller and the compressor impeller;
A bearing housing that rotatably supports the shaft;
A turbine housing that houses the turbine impeller;
A variable nozzle mechanism that is provided on the compressor impeller side on the radially outer side of the turbine impeller and adjusts the exhaust gas flow rate toward the turbine impeller, and
The bearing housing has a radially enlarged portion that extends radially outward, is coupled to the turbine housing at a radially outer portion, and accommodates a variable nozzle mechanism between the turbine housing,
A turbocharger with a variable nozzle, characterized in that a heat shield plate is provided between the enlarged diameter portion and the variable nozzle mechanism to prevent heat transfer between the variable nozzle mechanism and the enlarged diameter portion.   2. The turbocharger according to claim 1, wherein the heat shield plate has a radially outer end sandwiched between a turbine housing and a bearing housing. The heat shield is an annular member having an opening at the center,
2. The turbocharger according to claim 1, wherein the bearing housing has a reduced diameter portion that protrudes toward the turbine housing from the enlarged diameter portion and fits into the opening.

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