JP2010121590A - Variable displacement turbocharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable displacement turbocharger with a turbine housing in a twin scroll structure, having reduced flow joining loss during a large flow amount, increased reliability with a reduction of moving parts, and reduced thermal stress due to a temperature difference by increasing the flow velocity of exhaust gas flowing into an impeller moving blade with reduced loss during a small flow amount. <P>SOLUTION: The variable displacement turbocharger includes the turbine housing 20 having an annular flow path 22, and a small-flow-amount scroll 24 and a large-flow-amount scroll 26 having a junction 25 of joining each other near their radial outer ends, the small-flow-amount of scroll 24 having a plurality of small-flow-amount stationary blades 27 on the upstream side of the junction 25 for swirling a gas flow. It also includes a flow control valve installed in a gas flow-in manifold for opening/closing the gas flow-in port of the large-flow-amount scroll 26 to control the flow, and a control device for controlling the flow control valve. The flow control valve is fully closed during the small flow amount of exhaust gas, and the opening of the flow control valve is controlled corresponding to a gradual increase/reduction in the flow amount of the exhaust gas. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a variable capacity turbocharger having a twin scroll structure of a turbine housing that surrounds a turbine impeller and supplies exhaust gas to the outer periphery thereof.

  In a turbocharger, a turbine and a compressor are mechanically connected, and the turbine is rotated by engine exhaust gas, and compressed air is compressed by compressing intake air with the compressor connected to the turbocharger. Is a device that improves the performance of the engine.

  A turbine for a turbocharger is generally a radial turbine, and a scroll is used to supply exhaust gas to the outer periphery of the radial turbine. That is, the scroll is a spiral chamber that distributes the exhaust gas flow from the engine in a swirl flow and distributes it uniformly to the outer periphery of the turbine impeller.

The turbocharger described above has a problem that the flow rate range of the exhaust gas in which the turbine can operate at a high load is narrow because the turning flow rate is determined by the flow path shape of the scroll and the flow rate is insufficient at a low flow rate.
Therefore, various structures have been proposed in order to expand the flow range of exhaust gas that can be supplied to the turbocharger (for example, Patent Documents 1 to 3).

Patent Document 1 uses supercharging by a twin-scroll supercharger to reduce the pressure pulsation of exhaust gas in the exhaust passage at high revolutions, improve the supercharging efficiency, and improve the combustion of the engine. It aims to be in a state.
Therefore, as shown in FIG. 9, this engine exhaust system is connected to a separate combustion chamber in the engine 50, and the first exhaust passage 52 and the second exhaust passage 52 that guide the exhaust gas to the twin scroll supercharger 51 independently of each other. The exhaust passage 53, the connection passage 54 that communicates with each of the exhaust passages 52, 53, the openable / closable communication control valve 55 provided in the connection passage 54, and the communication control valve 55 is opened when the engine 50 is rotating at high speed. And a control unit that closes the communication control valve 55 at the time of low rotation, and when the engine 50 is at high rotation, the pressure pulsation of the exhaust gas in each of the exhaust passages 52 and 53 is made uniform.
In this figure, 56 is an exhaust control valve, 57 is a first scroll chamber, 58 is a second scroll chamber, and 59 is a turbine.

Patent document 2 aims at maintaining the efficiency of the performance of a turbocharger favorable when expanding the variable capacity in a variable capacity turbocharger.
Therefore, as shown in FIG. 10, the variable capacity turbocharger uses the reference position scroll area S of the outer peripheral scroll portion 60 as the sum S1 of the opening areas of all the communication holes 62 of the partition wall 61 (reference position scroll area S / total It is set to 1.2 times or less of the sum S1) of the opening areas of the communication holes.
In this figure, 63 is a turbine housing, 64 is a turbine rotor, and 65 is a control valve.

Patent Document 3 can significantly reduce the hysteresis of the turbine rotation speed and the sliding resistance of the variable nozzle blade when the nozzle is opened and closed, thereby facilitating automatic control of the turbine rotation speed and scratching the nozzle mounting surface and the gap adjustment plate. It aims to reduce wear and wear.
Therefore, as shown in FIG. 11, the variable nozzle device of the variable capacity supercharger includes a nozzle support in which each variable nozzle blade 70 penetrates the nozzle drive shaft 72 that penetrates the nozzle mounting surface 71 and the gap adjustment plate 73. Both ends are supported by a shaft 74. The pressure in the hollow chamber 76 of the link chamber 75 and the gap adjusting plate 73 is adjusted so that the axial force due to the gas pressure acting on the nozzle drive shaft 72 and the nozzle support shaft 74 is substantially balanced.
In this figure, 77 is a turbine housing, 78 is a turbine impeller, 79 is a scroll chamber, and 80 is a variable nozzle device.

JP 2004-68631 A, “Engine exhaust system and control method of engine exhaust system” JP 2001-263080 A, “Variable capacity turbocharger” Japanese Patent Application Laid-Open No. 2007-40251, “Variable Nozzle Device for Variable Capacity Supercharger”

As in Patent Document 1, the conventional twin scroll structure having two independent scrolls has the following problems.
In this structure, the two scroll outlets meet at the upstream portion of the impeller rotor blade. here,
(1) If a flow path partition that separates the two scroll flow paths is installed immediately upstream of the impeller rotor blades and the merging section is eliminated, it is necessary to widen the flow path width of that part by the thickness of the impeller. A step must be set in the flow path at the blade inlet, and the loss due to the step increases.
(2) In order to avoid this, if a confluence portion is formed in the upstream portion of the impeller rotor blade, a sudden expansion portion of the flow passage corresponding to the plate thickness of the flow passage partition wall is formed. The exhaust gas flow velocity flowing in is separated and loss is increased, while the swirl flow velocity is also slowed and the reaction degree R of the turbine rotor blade cannot be increased.
The reaction degree means the ratio R = Δi / W of the enthalpy change Δi with respect to the step work W in the impeller rotor blade.
(3) Moreover, since the flow path partition has a disk shape, thermal stress due to a temperature difference in the radial direction is large, and cracks tend to occur. That is, when connecting to the outer wall having a relatively low temperature, the temperature of the partition wall is low, and the temperature near the junction is high without a heat escape. At this time, if the flow path partition is disk-shaped, there is no escape from the difference in thermal expansion, and a high stress tends to be generated.

  In the twin scroll structure of Patent Document 2, since there is no front stator blade at the scroll outlet that flows only at a small flow rate, the flow velocity of the exhaust gas flowing into the impeller rotor blade at a very small flow rate becomes slow, and the reaction rate R of the turbine rotor blade is reduced. Can not be raised.

In the variable stator blade structure of Patent Document 3, in order to increase the impulsivity of the turbine rotor blade, the swirl flow velocity must be greatly accelerated in the stator blade portion, and the blade load of the stator blade needs to be set high.
In addition, the variable stationary blade structure of Patent Document 3 has many movable parts in the high-temperature part, so it easily breaks down, and exhaust gas leaks from many sliding parts, which deteriorates the performance especially at a low flow rate. There was a point.

  In other words, in the conventional twin scroll structure, since the twin scroll outlets are arranged in parallel with the rotor blade inlet and the flow path is enlarged at the rotor blade inlet, the flow is decelerated. Therefore, the circumferential flow velocity of air cannot be increased at the outlet of the low-speed side scroll.

  The present invention has been developed to solve the above-described conventional problems. That is, the object of the present invention is to increase the flow velocity of the exhaust gas flowing into the impeller rotor blade at low flow rate with low loss, reduce the merging loss of the flow at high flow rate, and increase the reliability by reducing the moving parts, An object of the present invention is to provide a variable capacity turbocharger having a twin scroll structure of a turbine housing that can reduce thermal stress due to a temperature difference.

According to the present invention, a turbine housing that surrounds a turbine impeller that is rotationally driven by engine exhaust gas and that supplies exhaust gas to the outer periphery thereof is provided.
The turbine housing surrounds the gas inlet of the turbine impeller and extends radially outward, and has an annular flow path without a sudden change in flow path area including a step,
A small flow scroll and a large flow scroll having a merge point that merges in the vicinity of the radially outer end of the annular flow path;
A gas inflow manifold for supplying exhaust gas from the engine to the gas inlet of the scroll for small flow rate and scroll for large flow rate,
The small flow scroll has a plurality of small flow vanes for swirling the gas flow flowing out to the annular flow path upstream of the junction.
Furthermore, a flow rate adjusting valve that is installed in the gas inflow manifold, always opens the gas inlet of the scroll for small flow rate, and opens and closes the gas inlet of the scroll for large flow rate so that the flow rate can be adjusted,
A control device for controlling the flow control valve;
A variable capacity turbocharger is provided, wherein the flow rate control valve is fully closed when the exhaust gas flow rate is small, and the opening degree of the flow rate control valve is adjusted in accordance with a gradual increase or decrease in the exhaust gas flow rate. .

  According to a preferred embodiment of the present invention, the radial position R of the merging point from the axis of the turbine impeller is not less than 1.2 times and not more than 10 times the radial position r of the gas inlet of the turbine impeller.

  In addition, it is preferable that a plurality of large flow rate stationary blades are provided on the upstream side of the merging point of the large flow rate scroll and rotate the gas flow flowing out to the annular flow path.

Further, according to the present invention, the turbine housing that surrounds the turbine impeller that is rotationally driven by the exhaust gas of the engine and that supplies the exhaust gas to the outer periphery thereof is provided.
The turbine housing surrounds the gas inlet of the turbine impeller and extends radially outward, and has an annular flow path without a sudden change in flow path area including a step,
A small flow scroll and a large flow scroll having a merge point that merges in the vicinity of the radially outer end of the annular flow path;
A gas inflow manifold for supplying exhaust gas from the engine to the gas inlet of the scroll for small flow rate and scroll for large flow rate,
A plurality of large flow vanes provided on the upstream side of the merging point of the large flow scroll, for rotating a gas flow flowing out to the annular flow path;
A variable nozzle device that oscillates the large flow rate stationary blade and variably controls the outlet flow passage area thereof,
A variable capacity turbocharger is provided, wherein the variable nozzle device is fully closed when the exhaust gas flow rate is small, and the opening degree of the variable nozzle device is adjusted in accordance with the gradual increase or decrease of the exhaust gas flow rate. .

  According to the configuration of the present invention, the turbine housing has the annular flow path that surrounds the gas inlet of the turbine impeller and extends radially outward, and has no sudden change in the flow path area including the step. Since the gas flow from the small flow scroll and the large flow scroll merge together at the merge point near the radially outer end of the path, there is a sudden expansion portion or a stepped portion in the exhaust gas flow channel (that is, the annular flow channel) after the merge. Less loss can be reduced.

Further, when the exhaust gas is at a low flow rate, the flow control valve or the variable nozzle device is fully closed, and the exhaust gas flows out only from the small flow rate scroll having a plurality of small flow rate stationary vanes. A swirling flow can be formed in the vicinity of the radially outer end.
Here, since the swirling speed of the swirling flow increases according to the angular momentum conservation law while flowing inward in the radial direction in the annular flow path, the flow velocity of the exhaust gas flowing into the impeller rotor blade (turbine impeller) can be increased. Accordingly, it is possible to improve the acceleration characteristics of the turbocharger particularly when the exhaust gas has a small flow rate.
In addition, when the small flow rate stationary blade or the large flow rate stationary blade is separated from the impeller rotor blade, the excitation force by the stationary blade is reduced, and resonance damage of the impeller rotor blade can be suppressed.

  On the other hand, when the opening degree of the flow rate control valve or the variable nozzle device is adjusted in accordance with the gradual increase or decrease of the exhaust gas flow rate, the exhaust gas from the small flow rate scroll and the large flow rate scroll are merged in the annular flow path. However, since the flow is merged in the vicinity of the outer end in the radial direction of the annular flow path, the flow velocity of the portion where the flow path is widened becomes slow, and the merge loss can be reduced.

  Furthermore, since the partition wall that divides the scroll for small flow rate and the scroll for large flow rate can be formed in a cylindrical shape or a prefix cone shape surrounding the axis of the turbine impeller, the thermal stress generated even if there is a temperature difference across the partition wall can be reduced. .

  Hereinafter, preferred embodiments 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 first embodiment of a variable capacity turbocharger according to the present invention, and FIG. 2 is a view taken along the line AA in FIG.
1 and 2, the variable capacity turbocharger of the present invention includes a turbine housing 20 that surrounds a turbine impeller 10 and supplies exhaust gas 1 to the outer periphery 12 thereof, a flow rate adjusting valve 30, and a control device 40.

  In this example, the turbine impeller 10 is a turbine impeller for a radial turbine. The turbine impeller 10 is rotationally driven by the engine exhaust gas 1 supplied inward from the outer periphery 12 to rotationally drive a compressor (not shown) of a turbocharger.

1 and 2, the turbine housing 20 includes outer walls 20a, 20b, 20c, an inner wall 20d, and partition walls 20e, 20f. An annular flow path 22, a small flow scroll 24, a large flow scroll 26, and a gas inflow are contained therein. It has a manifold 28.
In this example, the turbine housing 20 is manufactured by being divided in the vicinity of the outer peripheral end of the outer wall 20a, and is joined by welding or the like at the joining portion 21. In this case, the divided portion, that is, the joint portion 21 is, for example, a cylindrical surface surrounding the axis of the turbine impeller 10.

The annular flow path 22 surrounds the gas inlet (that is, the outer periphery 12) of the turbine impeller 10 and extends radially outward.
In this example, the annular flow path 22 is located between the disk-shaped outer wall 20 b that is located on the compressor side of the turbine housing 20 and extends in the radial direction, and the large-flow volume scroll 26, and extends in the radial direction. It is a hollow disk-shaped space formed between the partition walls 20e.
In addition, although the axial direction space | interval of the outer wall 20b and the partition 20e is increasing gradually in the radial direction in this example, it may be mutually parallel.

The small flow scroll 24 and the large flow scroll 26 have a merge point 25 that merges in the vicinity of the radially outer end of the annular flow path 22.
In this example, the small flow scroll 24 is located radially outside and the large flow scroll 26 is located radially inside, and is partitioned by a partition wall 20f.

Further, the partition wall 20f does not have a sudden expansion portion or a step portion in the gas flow path flowing out from the small flow scroll 24 to the annular flow path, and is configured in a cylindrical shape and a prefix cone shape so as to reduce thermal stress. .
Similarly, the partition wall 20e has no abruptly expanding portion or stepped portion in the gas flow channel flowing out from the large flow scroll 26 to the annular flow channel, and the tip portion is cylindrical or prefix conical so as to reduce thermal stress. It is configured.

  Further, the radial position R from the axial center of the turbine impeller 10 to the confluence point 25 is preferably sufficiently larger than the radial position r of the gas inlet 12. For example, the radial position R is 1.2 times or more the radial position r. It is set to 10 times or less.

  The gas inflow manifold 28 communicates with the gas inlets 24 a and 26 a of the small flow scroll 24 and the large flow scroll 26, and supplies the exhaust gas 1 from the engine to the small flow scroll 24 and the large flow scroll 26. It is supposed to be. The number of gas inflow manifolds 28 is one in this example, but may be plural if necessary.

1 and 2, the small flow scroll 24 has a plurality of small flow stationary vanes 27 installed on the upstream side of the junction 25 so as to swirl the gas flow 1 flowing out to the annular flow path 22. . This turning direction is the rotational direction of the turbine impeller 10.
In this example, the small flow vane 27 is formed integrally with the outer wall 20c or the partition wall 20f of the turbine housing 20, but is manufactured separately and fixed to the outer wall 20c or the partition wall 20f with welding or bolts. May be.

In FIG. 2, the flow rate adjusting valve 30 is installed in the gas inflow manifold 28, always opens the gas inlet 24 a of the small flow scroll 24, and opens and closes the gas inlet 26 a of the large flow scroll 26 so that the flow rate can be adjusted. A flow control valve 32 is provided.
The control device 40 controls the flow rate control valve 30, fully closes the flow rate control valve 30 when the exhaust gas flow rate is small, and adjusts the opening degree of the flow rate control valve in accordance with the gradual increase or decrease of the exhaust gas flow rate. . The flow control valve is opened and closed when the exhaust gas flow rate is medium / large flow rate, and the exhaust gas flow rate may be measured or calculated based on a command value (for example, rotational speed) from an engine control device (not shown). Good.

FIG. 3 is a diagram of a second embodiment of the variable capacity turbocharger of the present invention.
In this example, the turbine housing 20 is manufactured by being divided by flanges 21a and 21b provided on the outer peripheral portions of the outer walls 20a and 20c, and connected by bolts or the like.
Other configurations are the same as those of the first embodiment.

FIG. 4 is a diagram showing a third embodiment of the variable capacity turbocharger of the present invention, and FIG. 5 is a view taken along the line AA in FIG.
In this example, the turbine housing 20 is manufactured by being divided at the turbine side end portions of the outer wall 20c and the inner wall 20d, and joined by welding or the like at the joining portion 21.
In this example, the small flow scroll 24 is positioned radially inward and the large flow scroll 26 is positioned radially outward, and is partitioned by a partition wall 20f.
Furthermore, in this example, the small flow stationary vane 27 is formed integrally with the partition wall 20e or the partition wall 20f of the turbine housing 20.

Also, in this example, the partition wall 20f has a cylindrical shape and a prefix cone shape so that the gas flow path flowing out from the large flow scroll 26 to the annular flow path does not have a sudden expansion part or a step part, and reduces thermal stress. It is configured.
Similarly, the partition wall 20e has no abruptly enlarged portion or stepped portion in the gas flow channel flowing out from the small flow rate scroll 24 to the annular flow channel, and the tip portion is cylindrical or prefix conical so as to reduce thermal stress. It is configured.
Other configurations are the same as those of the first embodiment.

FIG. 6 is a diagram showing a fourth embodiment of the variable capacity turbocharger according to the present invention.
In this example, the turbine housing 20 is manufactured by being divided by flanges 21a and 21b provided on the outer peripheral portions of the outer walls 20a and 20c, and connected by bolts or the like.
Other configurations are the same as those of the third embodiment.

FIG. 7 is a diagram of a fifth embodiment of the variable capacity turbocharger of the present invention.
In this figure, the variable capacity turbocharger of the present invention is provided on the upstream side of the junction 25 of the large flow scroll 26 and a plurality of large flow stationary vanes 42 that swirl the gas flow flowing out to the annular flow path 22. Have both. Further, 20 g is a partition wall added along with the installation of the large flow stationary vane 42.
Other configurations are the same as those of the third embodiment shown in FIG.
With this configuration, the gas flow flowing out to the annular flow path 22 can be swirled by the plurality of large flow rate stationary vanes 42 provided on the upstream side of the junction 25 of the large flow rate scroll 26. The turning direction in this case is also the rotational direction of the turbine impeller 10.

  FIG. 8 is a diagram of a sixth embodiment of the variable capacity turbocharger of the present invention. In this figure, (A) is a cross-sectional view similar to that of the third embodiment of FIG. 4, (B) is a partial cross-sectional view taken along the line BB, and (C) is a view taken along the line CC.

In this example, there is no flow rate adjustment valve 32 that opens and closes the gas inlet 26a of the large flow rate scroll 26 in FIG. 5 of the third embodiment so that the flow rate can be adjusted. A nozzle device 44 is provided.
The plurality of high flow rate stationary blades 43 are variable nozzles integrated with the spindle portion 43 a and are provided on the upstream side of the merging point 25 of the large flow rate scroll 26 so as to swirl the gas flow flowing out to the annular flow path 22. It has become.
In this example, the variable nozzle device 44 includes a synchronization ring 45 that can swing in the circumferential direction, and a vane lever 46 that is fixed to the spindle portion 43a and rotatably connected to the synchronization ring 45. By swinging, the plurality of high flow vanes 43 are swung to variably control the outlet channel area.
Other configurations are the same as those of the fifth embodiment shown in FIG.

  With this configuration, the variable nozzle device 44 can be fully closed when the exhaust gas flow rate is small, and the opening degree of the variable nozzle device 44 can be adjusted in accordance with the gradual increase or decrease of the exhaust gas flow rate.

  According to the configuration of the present invention described above, the turbine housing 20 has the annular flow path 22 that surrounds the gas inlet 12 of the turbine impeller 10 and extends outward in the radial direction, and has no sudden change in flow path area including a step. Since the gas flows from the small flow rate scroll 24 and the large flow rate scroll 26 are merged together at the merging point 25 in the vicinity of the radially outer end of the annular channel 22, the exhaust gas channel after merging (that is, the annular channel) ), There are few suddenly enlarged parts and step parts, and loss can be reduced.

Further, when the exhaust gas has a small flow rate, the flow rate control valve 30 or the variable nozzle device is fully closed, and the exhaust gas 1 flows out into the annular flow path 22 only from the small flow rate scroll 24 having the plurality of small flow rate stationary vanes 27. A swirling flow can be formed in the vicinity of the radially outer end of the annular flow path 22.
Here, since the swirling speed of the swirling flow increases according to the angular momentum conservation law while flowing inward in the radial direction in the annular flow path, the flow velocity of the exhaust gas flowing into the impeller rotor blade (turbine impeller) can be increased. Accordingly, it is possible to improve the acceleration characteristics of the turbocharger particularly when the exhaust gas has a small flow rate.
Further, when the small flow rate stationary blade or the large flow rate stationary blade is separated from the impeller rotor blade, the excitation force by the stationary blade is reduced, and resonance damage of the impeller rotor blade can be suppressed.

  Further, when the opening degree of the flow rate control valve 30 or the variable nozzle device is adjusted in accordance with the gradual increase or decrease of the flow rate of the exhaust gas, the exhaust gas 1 from the small flow rate scroll 24 and the large flow rate scroll 26 is moved into the annular flow path. Although merging is performed at the merging point 25, the merging is performed in the vicinity of the outer end in the radial direction of the annular flow path 22.

  Further, the partition wall 20f that partitions the small flow scroll 24 and the large flow scroll 26 is formed in a cylindrical shape or a prefix cone shape that surrounds the axis of the turbine impeller 10, so that even if there is a temperature difference across the partition wall 20f. Thermal stress can be reduced.

Furthermore, according to the present invention, the following effects can be obtained.
(1) The step of the flow path at the impeller rotor blade inlet can be avoided.
(2) The blade chord length of the low flow vane can be shortened, the number of blades can be reduced, and the blade shape can be simplified.
(3) The failure rate can be reduced by adjusting the gas flow rates of the small flow rate scroll 24 and the large flow rate scroll 26 with one flow rate control valve 30 or a variable nozzle device.
(4) By flowing a small amount of gas even when the flow rate of gas flowing through the scroll 26 for large flow rate is small, the influence of channel expansion is not exerted downstream, and at the small / medium flow rate, the merge portion of the flow channel The merging loss can be suppressed by merging so that the low-speed gas oozes out at the inflow portion.
(5) The choke flow rate at the inlet portion of the impeller rotor blade can be set large by decelerating the swirling flow velocity with the exhaust gas joined from the scroll without installing a stationary blade at the outlet of the large flow scroll 26.
(6) A stationary blade can be installed at the exit of the scroll 26 for large flow rate, the swirl flow rate can be adjusted by the exhaust gas that merges from the scroll, and the impulsiveness of the impeller blade can be maintained even at medium / large flow rates. .
(7) By making the stationary blade variable, the swirl flow rate can be adjusted more finely by the exhaust gas that merges from the scroll, and the turbine performance can be improved.

  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.

1 is a first embodiment of a variable capacity turbocharger according to the present invention. It is an AA arrow line view of FIG. It is a 2nd embodiment figure of the variable capacity turbocharger of the present invention. It is a 3rd embodiment figure of the variable capacity turbocharger of the present invention. It is an AA arrow line view of FIG. It is a 4th embodiment figure of the variable capacity turbocharger of the present invention. It is a 5th embodiment figure of the variable capacity turbocharger of the present invention. It is a 6th embodiment figure of the variable capacity turbocharger of the present invention. 1 is a schematic diagram of an engine exhaust system of Patent Document 1. FIG. FIG. 3 is a schematic diagram of a variable capacity turbocharger disclosed in Patent Document 2. It is a schematic diagram of the variable nozzle apparatus of patent document 3. FIG.

Explanation of symbols

1 exhaust gas,
10 turbine impeller, 12 outer periphery (gas inlet),
20 turbine housing, 20a, 20b, 20c outer wall,
20d inner wall, 20e, 20f, 20g partition, 21 joints,
21a, 21b flange, 22 annular flow path,
24 Scroll for small flow rate, 24a Gas inlet,
25 merging point, 26 scroll for large flow, 26a gas inlet,
27 Small flow vane, 28 Gas inflow manifold,
30 flow control valve, 32 swing valve, 40 control device,
42 High-flow stationary vane, 43 Large-flow stationary vane (variable nozzle),
43a spindle unit, 44 variable nozzle device,
45 synchronization ring, 46 vane lever

Claims (4)

A turbine housing that surrounds a turbine impeller that is rotationally driven by engine exhaust gas and that supplies exhaust gas to the outer periphery thereof;
The turbine housing surrounds the gas inlet of the turbine impeller and extends radially outward, and has an annular flow path without a sudden change in flow path area including a step,
A small flow scroll and a large flow scroll having a merge point that merges in the vicinity of the radially outer end of the annular flow path;
A gas inflow manifold for supplying exhaust gas from the engine to the gas inlet of the scroll for small flow rate and scroll for large flow rate,
The small flow scroll has a plurality of small flow vanes for swirling the gas flow flowing out to the annular flow path upstream of the junction.
Furthermore, a flow rate adjusting valve that is installed in the gas inflow manifold, always opens the gas inlet of the scroll for small flow rate, and opens and closes the gas inlet of the scroll for large flow rate so that the flow rate can be adjusted,
A control device for controlling the flow control valve;
A variable capacity turbocharger, wherein the flow rate control valve is fully closed when the exhaust gas flow rate is small, and the opening degree of the flow rate control valve is adjusted in accordance with a gradual increase or decrease in the exhaust gas flow rate.   The radial position R from the axial center of the turbine impeller to the confluence is 1.2 times or more and 10 times or less the radial position r of the gas inlet of the turbine impeller. Variable capacity turbocharger.   2. The high-flow-rate scroll is provided on the upstream side of the merging point of the high-flow-rate scroll, and has a plurality of large-flow-rate vanes that swirl the gas flow flowing out to the annular flow path. Variable capacity turbocharger. A turbine housing that surrounds a turbine impeller that is rotationally driven by engine exhaust gas and that supplies exhaust gas to the outer periphery thereof;
The turbine housing surrounds the gas inlet of the turbine impeller and extends radially outward, and has an annular flow path without a sudden change in flow path area including a step,
A small flow scroll and a large flow scroll having a merge point that merges in the vicinity of the radially outer end of the annular flow path;
A gas inflow manifold for supplying exhaust gas from the engine to the gas inlet of the scroll for small flow rate and scroll for large flow rate,
A plurality of large flow vanes provided on the upstream side of the merging point of the large flow scroll, for rotating a gas flow flowing out to the annular flow path;
A variable nozzle device that oscillates the large flow rate stationary blade and variably controls the outlet flow passage area thereof,
A variable capacity turbocharger, wherein the variable nozzle device is fully closed when the exhaust gas flow rate is small, and the opening degree of the variable nozzle device is adjusted in accordance with a gradual increase or decrease in the exhaust gas flow rate.

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