JP2008169767A - Variable displacement supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately adjust opening area of a bypass passage in a variable displacement supercharger adjusting opening area of the bypass passage bypassing an inside of an blade part of a turbine impeller and a downstream side of the turbine impeller for inhibiting occurrence of choke phenomenon of exhaust gas. <P>SOLUTION: This variable displacement supercharger is provided with a communication path 21e bypassing part of exhaust gas from an exhaust pass near a throat part T of the turbine impeller 23 to a downstream side of the turbine impeller 23, and a third control valve 29 adjusting opening area of the communication path 21e. Opening of the third control valve 29 is adjusted to be larger as intake air quantity largely depending on existence of occurrence of choke phenomenon become larger. The pressure ratio of exhaust gas pressure in a downstream side and exhaust gas pressure in an upstream side of the turbine impeller 23 is thereby inhibited from getting larger than critical pressure ratio, and then occurrence of choke phenomenon is inhibited. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a variable capacity supercharger.

  In general, in a supercharger of an internal combustion engine (hereinafter also simply referred to as “engine”), the pressure of exhaust gas upstream of the turbine impeller (hereinafter referred to as “upstream pressure”). The exhaust gas flowing toward the turbine impeller (hereinafter referred to as “turbine inflow exhaust gas”) increases as the mass flow rate increases. On the other hand, the pressure of the exhaust gas downstream of the turbine impeller (hereinafter referred to as “downstream pressure”) is substantially constant regardless of the mass flow rate of the turbine inflowing exhaust gas. The ratio to the side pressure (hereinafter referred to as “pressure ratio”) increases as the mass flow rate of the turbine inflowing exhaust gas increases. Further, the volumetric flow rate of the turbine inflowing exhaust gas and the exhaust gas flowing out from the blade part of the turbine impeller (particularly, the part having the smallest opening area of the exhaust gas passage in the blade part) (hereinafter referred to as “turbine outflowing exhaust gas”). The volumetric flow rate increases as the mass flow rate of the turbine inflowing exhaust gas increases.

  When the pressure ratio reaches a predetermined value (critical pressure ratio) due to an increase in the mass flow rate of the turbine inflowing exhaust gas, the flow rate of the turbine outflowing exhaust gas reaches the speed of sound. As a result, when the mass flow rate of the turbine inflowing exhaust gas further increases, the flow rate of the turbine outflowing exhaust gas is maintained at the sonic speed, and the volumetric flow rate of the turbine inflowing exhaust gas does not increase (that is, the volumetric flow rate of the turbine inflowing exhaust gas also increases. A so-called “choke phenomenon” occurs.

  When the choke phenomenon occurs, the increase gradient of the upstream pressure with respect to the increase in the mass flow rate of the turbine inflowing exhaust gas is very large. For this reason, when the mass flow rate of the turbine inflow exhaust gas is increased, the upstream pressure can be greatly increased. In this case, due to the fact that high-temperature exhaust gas tends to remain in the cylinder of the engine, the combustion temperature of the air-fuel mixture in the cylinder may become excessively high and knocking may occur. Further, it becomes difficult for fresh air to be sucked into the cylinder, and the engine output decreases. From the above, it is required to suppress the occurrence of the choke phenomenon.

From such a viewpoint, as the supercharger, for example, the turbine impeller and the turbine impeller are rotatably accommodated by inflow of all the exhaust gas discharged from the engine into the accommodation chamber formed inside. A housing, a compressor impeller for compressing air in an intake passage of the internal combustion engine that is rotated by the rotation of the turbine impeller, and a blade portion of the turbine impeller on an inner wall of the housing chamber are enclosed from the radially outer side. A bypass passage that has one end provided in the portion and bypasses a part of the exhaust gas in the blade portion downstream of the turbine impeller, and a control valve that is interposed in the bypass passage and adjusts an opening area of the bypass passage. There are those provided, which are described in Patent Document 1 below.
JP-A-8-61076

  According to the configuration related to the supercharger described in Patent Document 1, the control valve interposed in the bypass passage is opened and the bypass passage is communicated, so that the exhaust gas in the blade portion of the turbine impeller is communicated. The opening area of the passage is substantially enlarged, and the upstream pressure is reduced. As a result, the occurrence of the choke phenomenon can be suppressed. In addition, all the exhaust gas from the engine flows into the turbine impeller. Therefore, compared with the case where a part of the exhaust gas on the upstream side of the turbine impeller is bypassed to the downstream side of the turbine impeller in order to suppress the occurrence of the choke phenomenon, the energy of the exhaust gas can be used more effectively.

  By the way, in this supercharger, when the pressure of the air compressed by the compressor impeller (hereinafter referred to as “supercharging pressure”) is within a predetermined pressure Pc or less, When the opening area becomes “0” and the supercharging pressure is larger than the predetermined pressure Pc, the control valve is controlled so that the opening area of the bypass passage becomes larger as the supercharging pressure becomes larger. It has become. When the opening area of the bypass passage is adjusted according to the supercharging pressure as described above, the following problem occurs in suppressing the occurrence of the choke phenomenon described above. Such a problem will be described with reference to FIG.

  FIG. 7 is a graph showing the relationship between the engine operating speed, the supercharging pressure, the mass flow rate of air in the intake passage, and the occurrence of the choke phenomenon. As is apparent from FIG. 7, even if the supercharging pressure is higher than the predetermined pressure Pc, the choke phenomenon may not occur if the engine operating speed is low (see, for example, point A in FIG. 7). ).

  In this case, in the turbocharger described in the above document, since the bypass passage is communicated even though the choke phenomenon does not occur, a part of the exhaust gas in the blades of the turbine impeller is turbine blades. It will be bypassed downstream of the car. Therefore, the problem that the energy of exhaust gas cannot be used effectively occurs.

  On the other hand, even if the supercharging pressure is equal to or lower than the predetermined pressure Pc, the choke phenomenon may occur when the engine operating speed is high (see, for example, point B in FIG. 7). In this case, in the supercharger described in the above-mentioned document, the bypass passage is blocked, and thus the problem that the occurrence of the choke phenomenon cannot be suppressed occurs. As described above, in the supercharger described in the above document, the opening area of the bypass passage is adjusted only in accordance with the supercharging pressure, so that the opening of the bypass passage is suppressed in order to suppress the occurrence of the choke phenomenon. There was a problem that the area could not be adjusted appropriately.

  Accordingly, an object of the present invention is to provide a variable capacity supercharger that can appropriately adjust the opening area of the bypass passage in order to suppress the occurrence of the choke phenomenon.

  The first variable displacement supercharger according to the present invention includes the turbine impeller, the housing, the compressor impeller, and an exhaust gas flowing toward the turbine impeller according to the operating state of the engine ( The first adjustment means for adjusting the first opening area, which is the opening area of the inlet of the turbine inflowing exhaust gas), and one end provided on the inner wall of the storage chamber at a portion surrounding the blade portion of the turbine impeller from the outside in the radial direction A first bypass passage that bypasses a part of the exhaust gas in the blade portion to the downstream side of the turbine impeller, and a second opening area that is interposed in the first bypass passage and is an opening area of the first bypass passage. And second adjusting means for adjusting.

  Here, the “first adjusting means” adjusts, for example, the first opening area so as to be smaller as the operating speed of the engine is smaller. Thereby, when the engine operating speed is low, the flow rate of the turbine inflowing exhaust gas can be increased, and the rotational speed (that is, the supercharging pressure) of the turbine impeller can be increased. Therefore, it is possible to improve the torque characteristics at low speed of the engine.

  The first variable displacement supercharger according to the present invention is characterized in that the second adjusting means adjusts the second opening area so that the larger the flow rate of air in the intake passage of the engine, the larger the second opening area. It is configured to do. Here, the “air flow rate” is a mass flow rate of air, a volume flow rate of air, and the like, and is not limited thereto.

  As shown in FIG. 7, whether or not the choke phenomenon occurs greatly depends on the air flow rate. Therefore, according to the above configuration, the opening area of the exhaust gas passage in the blade portion is set in accordance with the air flow rate (hence, the volume flow rate of air) that greatly depends on the occurrence of the choke phenomenon. As a result, the second opening area can be appropriately adjusted in order to suppress the occurrence of the choke phenomenon.

  In the first variable displacement supercharger according to the present invention, the second adjusting means has the second opening area when the air flow rate is in a range in which the choke phenomenon of the exhaust gas in the blade portion does not occur. Is preferably set to “0”. According to this, the occurrence of the problem that the first bypass passage is communicated even though the choke phenomenon does not occur can be avoided.

  The second variable displacement supercharger according to the present invention is the same as the turbine impeller, the housing, the compressor impeller, and the first one that the first variable displacement supercharger according to the present invention has. An adjustment means, the first bypass passage, and a second adjustment means different from the first variable displacement supercharger according to the present invention are provided.

  The second variable displacement supercharger according to the present invention is characterized in that the second adjusting means determines the second opening area, the exhaust gas pressure upstream of the downstream end of the blade portion, and the turbine. This is because it is configured to adjust so as to increase as the degree of difference from the pressure on the downstream side of the impeller (the downstream pressure) increases.

  Here, “the pressure of the exhaust gas upstream from the downstream end of the blade portion” refers to, for example, the pressure of the exhaust gas in the exhaust gas passage formed by the adjacent blade and the inner wall of the housing chamber of the housing, the turbine It is the pressure of the exhaust gas upstream of the impeller (the upstream pressure) and the like, and is not limited to these. The “degree of difference” refers to, for example, the differential pressure between the pressure of the exhaust gas upstream of the downstream end of the blade and the downstream pressure, or upstream of the downstream end of the blade. The ratio of the exhaust gas pressure to the downstream pressure is not limited to these.

  As described above, whether or not the choke phenomenon occurs largely depends on the degree of pressure difference. Therefore, according to the above configuration, the opening area of the passage of the exhaust gas in the blade portion is set according to the degree of the pressure difference that greatly depends on whether or not the choke phenomenon occurs. Accordingly, the second opening area can be appropriately adjusted in order to suppress the occurrence of the choke phenomenon.

  In the second variable capacity turbocharger according to the present invention, when the second adjusting means has a degree of difference in the pressure within a range in which the choke phenomenon of the exhaust gas in the blade portion does not occur, It is preferable that the two opening areas are configured to be set to “0”. This also avoids the problem that the bypass passage is communicated even though the choke phenomenon does not occur.

  In the first and second variable displacement turbochargers according to the present invention, a second bypass passage that bypasses a part of the exhaust gas upstream of the turbine impeller to the downstream side of the turbine impeller, When the pressure of the air (the supercharging pressure) that is interposed in the second bypass passage and is compressed in the second bypass passage by the compressor impeller is below a predetermined pressure, the supercharging pressure is the same as the predetermined pressure. It is preferable to provide a means for communicating if larger.

  Thereby, when the supercharging pressure becomes larger than a predetermined pressure, a part of the exhaust gas upstream of the turbine impeller is bypassed downstream of the turbine impeller. As a result, an excessive increase in the supercharging pressure can be suppressed. In this case, the opening area of the second bypass passage is adjusted according to the supercharging pressure. On the other hand, as described above, the second opening area in the first bypass passage is adjusted according to the flow rate of the air or the degree of difference in the pressure, unlike the supercharging pressure. In other words, the communication / blocking of the second bypass passage is performed independently of the adjustment of the second opening area in the first bypass passage.

  Therefore, compared with the case where both the opening area of the second bypass passage and the second opening area are adjusted in accordance with the flow rate of the air, the second bypass passage is suppressed in order to suppress an excessive increase in supercharging pressure. The opening area of the bypass passage can be adjusted more appropriately.

  Embodiments of a variable capacity supercharger according to the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 shows a schematic configuration of a variable capacity supercharger according to a first embodiment of the present invention. The variable capacity supercharger is configured by a turbine unit 20 and a compressor unit 30 that are connected to each other via a connecting unit 10.

  The connecting portion 10 includes a bearing housing 11 and a shaft 15 that is rotatably supported in the bearing housing 11 via a bearing 13. The shaft 15 projects left and right ends from the bearing housing 11. ing. One end side of the shaft 15 faces the turbine housing 21 constituting the turbine part 20, and the other end side of the shaft 15 faces the compressor housing 31 constituting the compressor part 30. A turbine impeller 23 constituting the turbine unit 20 is integrally rotatable and coaxially fixed to one end side of the shaft 15, and a compressor impeller 33 constituting the compressor unit 30 is attached to the other end side of the shaft 15. Are integrally rotatable and coaxially assembled.

  The turbine unit 20 includes a turbine housing 21, a turbine impeller 23 housed in a housing chamber of the turbine housing 21, and a wastegate passage (second bypass passage) 25 that bypasses the turbine impeller 23. The turbine housing 21 is attached to one side of the bearing housing 11 constituting the connecting portion 10. The turbine impeller 23 penetrates one side of the bearing housing 11 and is fixed to the one end side of the shaft 15 facing the turbine housing 21 so as to be integrally rotatable and coaxially, and is formed in the turbine housing 21. It is arranged in the passage. The turbine impeller 23 includes a plurality of turbine blades 23a, and an exhaust passage is formed between adjacent turbine blades 23a. The opening area of the exhaust passage is sequentially reduced along the flow direction of the exhaust gas so as to be minimized at the throat portion T that is the downstream end portion of the turbine blade 23a (that is, the outlet of the exhaust passage in the turbine blade 23a). Is formed. The wastegate passage 25 is disposed so as to communicate the exhaust passage upstream of the turbine impeller 23 and the exhaust passage downstream of the turbine impeller 23.

  The turbine housing 21 includes an exhaust introduction port 21a and an exhaust discharge port 21b, and a space between the exhaust introduction port 21a and the exhaust discharge port 21b is formed in the exhaust passage, and the upstream side of the turbine impeller 23 in the exhaust passage is spiral. The scroll portion 21c is formed. The scroll portion 21c includes a partition wall 21c1 that equally divides the volume of the exhaust passage in the scroll portion 21c. The exhaust passage in the scroll portion 21c is divided into a first scroll exhaust passage 21c2 and a second scroll exhaust passage by the partition wall 21c1. It is partitioned into 21c3.

  Further, the turbine housing 21 includes a ring-shaped groove portion 21d formed coaxially with the turbine impeller 23 in a portion surrounding the turbine impeller 23 on the inner wall of the accommodation chamber from the radially outer side, and a downstream end face of the groove portion 21d. A communication passage 21e that communicates a part of the exhaust passage with the downstream side of the turbine impeller 23 is provided. The groove 21d and the communication passage 21e constitute the first bypass passage. The downstream end face of the groove portion 21d is formed in the vicinity of the throat portion T and at the position of the inner wall of the storage chamber corresponding to the upstream side of the throat portion T. That is, one end of the first bypass passage is formed at a position corresponding to the downstream end of the turbine blade 23 a on the inner wall of the storage chamber of the turbine housing 21.

  The turbine unit 20 includes a butterfly-type first control valve 27 (a part of the first adjusting means) interposed in the second scroll exhaust passage 21c3 and a butterfly-type butterfly interposed in the wastegate passage 25. A second control valve 28 and a butterfly-type third control valve 29 (a part of the second adjusting means) interposed in the communication path 21e are provided.

  The first control valve 27, the second control valve 28, and the third control valve 29 are rotatably supported by the second scroll exhaust passage 21c3, the waste gate passage 25, and the communication passage 21e, respectively. By being driven by the actuators 27a, 28a, 29a of the second control valve 28 and the third control valve 29, the position indicated by the two-dot chain line in FIG. 1 from the position indicated by the solid line in FIG. The opening is adjusted until the passage is communicated at the maximum opening. That is, the opening area of the second scroll exhaust passage 21c3 (accordingly, the opening area of the exhaust passage in the scroll portion 21c (the first opening area)), the opening area of the wastegate passage 25, and the opening area of the communication passage 21e (described above) The second opening area) is variable.

  The compressor unit 30 includes a compressor housing 31 and a compressor impeller 33 accommodated in the compressor housing 31, and the compressor housing 31 is attached to the other side of the bearing housing 11 constituting the connecting unit 10. . The compressor impeller 33 passes through the other side of the bearing housing 11 and is integrally rotatable and coaxially assembled to the other end of the shaft 15 facing the compressor housing 31. The compressor impeller 33 is formed in the compressor housing 31. Is contained in the intake passage.

  The compressor housing 31 includes a compressor introduction port 31a and a compressor discharge port 31b. A space between the compressor introduction port 31a and the compressor discharge port 31b is formed in the intake passage, and is downstream of the position where the compressor impeller 33 is disposed in the intake passage. The side is formed in the scroll-shaped scroll part 31c.

  On the other hand, this variable displacement supercharger includes an air flow meter 41 disposed in the intake passage upstream of the compressor impeller 33, a pressure sensor 43 disposed in the intake passage downstream of the compressor impeller 33, A first control valve opening sensor 45 that detects the opening of the first control valve, a second control valve opening sensor 47 that detects the opening of the second control valve, and a third that detects the opening of the third control valve. A control valve opening sensor 49 is provided.

  The air flow meter 41 is configured by a known hot-wire air flow meter, and outputs a voltage corresponding to the mass flow rate (intake air flow rate Ga) of intake air flowing through the intake passage per unit time. The pressure sensor 43 detects air pressure (supercharging pressure P) in the intake passage compressed by the compressor impeller 33 and outputs a signal representing the supercharging pressure P. The first control valve opening sensor 45, the second control valve opening sensor 47, and the third control valve opening sensor 49 are the opening TA1 of the first control valve 27, the opening TA2 of the second control valve 28, and The opening degree TA3 of the third control valve 29 is detected, and signals representing TA1, TA2, and TA3 are output. Signals from the sensors 41 to 49 and the crank position sensor 51 that detects an operation speed NE of an engine (not shown) and outputs a signal representing the operation speed NE are transmitted to the electric control unit ECU, and the electric control unit ECU outputs a drive signal. The first control valve 27, the second control valve 28, and the third control valve 29 are sent to the actuators 27a, 28a, 29a.

  The variable capacity supercharger configured as described above operates by introducing all exhaust gas discharged from an engine (not shown) into the exhaust passage through the exhaust introduction port 21a of the turbine housing 21 constituting the turbine unit 20. Then, the boost pressure P set in the compressor unit 30 is generated, and the air at the boost pressure P is supplied to the intake port of the engine.

  At this time, the target value TA1t of the opening degree of the first control valve 27 is determined so as to become smaller as the engine operating speed NE becomes smaller, and the opening degree TA1 of the first control valve 27 coincides with the target value TA1t. Thus, PID control is performed. Thereby, when the operation speed NE is low, the opening area of the second scroll exhaust passage 21c3 (that is, the exhaust passage in the scroll portion 21c) is set small, and the flow velocity of the exhaust gas flowing toward the turbine impeller 23 is increased. As a result, the rotational speed (that is, the supercharging pressure P) of the turbine impeller 23 can be increased. Therefore, it is possible to improve the torque characteristics at low speed of the engine.

  The target value TA2t of the opening degree of the second control valve 28 is determined so as to increase as the supercharging pressure P increases, and the second control valve 28 performs PID control so that the opening degree TA2 matches the target value TA2t. It has come to be. As a result, the higher the supercharging pressure P, the greater the extent that a part of the exhaust gas upstream of the turbine impeller 23 is bypassed downstream of the turbine impeller 23. As a result, an excessive increase in the supercharging pressure P can be suppressed.

  The target value TA3t of the opening degree of the third control valve 29 defines the relationship between the intake air flow rate Ga and the intake air flow rate Ga shown by the graph in FIG. 2 and the target value TA3t of the opening degree of the third control valve 29. Based on the table MapTA3t (Ga), the third control valve 29 is PID-controlled so that the opening degree TA3 coincides with the target value TA3t. Hereinafter, functions and effects relating to the adjustment of the third control valve 29 according to the intake air flow rate Ga will be described in detail.

  A predetermined upstream side of the upstream end portion of the turbine blade 23a and a downstream side of the throat portion T of the exhaust gas pressure (hereinafter referred to as "upstream side pressure") at a predetermined position of the scroll portion 21c. When the pressure ratio, which is a ratio to the pressure of the exhaust gas at the position (hereinafter referred to as “downstream pressure”), reaches the critical pressure ratio, the choke phenomenon described above occurs in the throat portion T having the smallest opening area in the exhaust passage. appear. The upstream pressure increases as the intake air flow rate Ga increases, while the downstream pressure is substantially constant regardless of the intake air flow rate Ga.

  For this reason, the pressure ratio increases as the intake air flow rate Ga increases. Therefore, when the communication path 29e is blocked, the choke phenomenon occurs in the throat portion T when the intake air flow rate Ga reaches the value Ga1 corresponding to the critical pressure ratio (see FIG. 7). That is, whether or not the choke phenomenon occurs in the throat portion T greatly depends on the intake air flow rate Ga.

  Here, when the communication passage 29e is communicated, a part of the exhaust gas flowing through the exhaust passage in the turbine blade 23a moves from the vicinity of the throat portion T to the downstream side of the turbine impeller 23 through the groove portion 21d and the communication passage 21e. Bypassed. That is, the substantial opening area of the exhaust passage in the vicinity of the throat portion T (that is, the sum of the opening area of the exhaust passage in the throat portion T and the opening area of the communication passage 21e) is expanded, and the pressure ratio is reduced. In this way, the communication passage 21e is communicated, whereby the pressure ratio can be suppressed to be equal to or lower than the critical pressure ratio.

  Here, from the viewpoint of increasing the supercharging pressure P (that is, the rotational speed of the turbine impeller 23) as much as possible, the pressure ratio is maintained as large as possible within a range not exceeding the critical pressure ratio. Is preferred. That is, it is preferable that the degree of decrease in the pressure ratio is reduced within a range where the intake air flow rate Ga is greater than the value Ga1. Therefore, the second adjusting means is configured such that when the flow rate of air in the intake passage is within a range where the choke phenomenon of the exhaust gas in the vane portion occurs, the second opening area is determined so that the degree of difference in the pressure is critical. Adjust to maintain a value corresponding to the pressure ratio.

  More specifically, in this apparatus, according to the table MapTA3t (Ga), the target value TA3t of the opening degree of the third control valve 29 is within the range where the intake air flow rate Ga is larger than the value Ga1. The larger the intake air flow rate Ga, the larger the value, and the pressure ratio is set to be maintained at the critical pressure ratio (see FIG. 2). Thereby, when the intake air flow rate Ga is larger than the value Ga1, the supercharging pressure P can be increased by maintaining the pressure ratio at the critical pressure ratio while suppressing the occurrence of the choke phenomenon in the throat portion T. .

  As described above, according to the first embodiment of the variable capacity supercharger according to the present invention, a part of the exhaust gas flowing through the exhaust passage in the turbine blade 23 a is bypassed downstream of the turbine impeller 23. The opening area of the passage 21e is adjusted according to the intake air flow rate Ga that greatly depends on whether or not the choke phenomenon occurs in the throat portion T. Thereby, in order to suppress generation | occurrence | production of the choke phenomenon in the throat part T, the opening area of the communicating path 21e can be adjusted appropriately.

  Moreover, it replaces with the structure of this embodiment, for example, the structure by which the groove part 21d is formed in the edge part vicinity of the upstream of the turbine blade 23a can be considered. On the other hand, most of the conversion from the energy of the exhaust gas to the energy for rotating the turbine impeller 23 is performed in the vicinity of the upstream end of the turbine blade 23a. Therefore, in the above configuration, when the communication passage 21e is communicated, a part of the exhaust gas flowing through the exhaust passage of the turbine blade 23a is bypassed before the above-described energy conversion is sufficiently performed. For this reason, it is difficult to increase the supercharging pressure P (that is, the rotational speed of the turbine impeller 23). On the other hand, the groove portion 21d is formed in the vicinity of the throat portion T as in the configuration of the present embodiment, so that a part of the exhaust gas is bypassed after the above-described energy conversion is sufficiently performed. Thereby, the supercharging pressure P can be increased while the occurrence of the choke phenomenon in the throat portion T is suppressed.

  Further, when the intake air flow rate Ga is equal to or less than the above value Ga1, the choke phenomenon in the throat portion T does not occur. Therefore, it is preferable that the communication path 21e is blocked from the viewpoint of effectively using the energy of the exhaust gas. Therefore, according to the table MapTA3t (Ga), the target value TA3t of the opening degree of the third control valve 29 is related to the magnitude of the intake air flow rate Ga within the range where the intake air flow rate Ga is not more than the above value Ga1. It is maintained at “0” (see FIG. 2). As a result, the communication path 21e can be prevented from communicating even though the choke phenomenon in the throat portion T does not occur. Therefore, the problem that the energy of the exhaust gas cannot be used effectively can be avoided.

  In addition, as described above, the opening area of the wastegate passage 25 is adjusted according to the supercharging pressure P. In other words, the adjustment of the opening area of the wastegate passage 25 is performed independently of the adjustment of the opening area of the communication passage 21e. Therefore, in order to suppress an excessive increase in the supercharging pressure P compared to the case where the opening area of the waste gate passage 25 and the opening area of the communication passage 21e are both adjusted according to the intake air flow rate Ga, The opening area of the passage 25 can be adjusted more appropriately.

(Second Embodiment)
Next, a variable capacity supercharger according to a second embodiment of the present invention will be described. In the second embodiment, the opening area of the communication passage 21e is set such that the pressure of the exhaust gas at the predetermined position of the scroll portion 21c (the upstream pressure) and the pressure of the exhaust gas at the predetermined position downstream of the throat portion T (the downstream) This is different from the first embodiment that is adjusted according to the intake air flow rate Ga only in that the pressure is adjusted according to the differential pressure ΔP. Hereinafter, only such a difference will be described with reference to FIG. 3 which is an enlarged view of the turbine section 20 and FIG. 4 which is a diagram showing the relationship between the differential pressure ΔP and the opening area of the communication passage 21e. 3, the same members and parts as those shown in FIG. 1 described above and parts, or equivalent members and parts, are denoted by the same reference numerals as those shown in FIG.

  This variable displacement supercharger includes a differential pressure actuator 60 fixed to the turbine housing 21. The differential pressure actuator 60 includes a casing 61, a diaphragm 63 that defines the internal space of the casing 61 as two spaces, a first pressure chamber 61 a and a second pressure chamber 61 b, and one end connected to the diaphragm 63. A valve body 65 assembled so as to be relatively movable, and a spring 67 (attached) interposed between the casing 61 and the diaphragm 63 in the second pressure chamber 61b to urge the valve body 65 in the valve closing direction via the diaphragm 63. A first communication pipe 61a1 communicating with the first scroll exhaust passage 21c2 and the first pressure chamber 61a, an exhaust passage downstream of the throat portion T of the turbine blade 23a, and the second pressure chamber 61b. A second communication pipe 61b1 is provided.

  In particular, the spring 67 has an initial load (in the state shown by the solid line in FIG. 5 and a load in a state where the differential pressure ΔP is “0”) when the pressure ratio is equal to the critical pressure ratio (hereinafter, It is designed to be equal to the force represented by the product of the value ΔP1 which is the differential pressure ΔP in “the choke generation start state” and the pressure receiving area of the diaphragm 63.

  Therefore, when the differential pressure ΔP is larger than the value ΔP1, the valve body 65 is opened. In this case, the opening area of the communication passage 21e increases as the differential pressure ΔP increases (see FIG. 4). As a result, as described above, the pressure ratio can be made smaller than when the valve body 65 is closed, and the degree to which the differential pressure ΔP deviates from the value ΔP1 can be made smaller.

  On the other hand, when the differential pressure ΔP is equal to or less than the value ΔP1, the valve body 65 is closed and the communication passage 21e is shut off (see FIG. 4). Thereby, it can be avoided that the communication passage 21e communicates even though the choke phenomenon in the throat portion T does not occur, and the problem that the energy of the exhaust gas cannot be used effectively can be avoided.

  As described above, according to the second embodiment of the variable capacity supercharger according to the present invention, the differential pressure ΔP is within the range equal to or larger than the value ΔP1 that is the differential pressure ΔP in the choke generation start state. The opening area of the passage 21e is adjusted to be larger as the differential pressure ΔP is larger. Thereby, when the differential pressure ΔP is equal to or greater than the above value ΔP1, the degree to which the differential pressure ΔP deviates from the same value ΔP1 can be reduced. As a result, the upstream pressure can be suppressed from becoming very large, and the occurrence of knocking due to the occurrence of the choke phenomenon described above and the reduction in engine output can be suppressed.

(Third embodiment)
Next, a variable capacity turbocharger according to a third embodiment of the present invention will be described. As will be described in detail later, the third embodiment is different from the second embodiment in that the pressure of the exhaust gas in the groove 21d is used as the upstream pressure at the differential pressure ΔP. Hereinafter, only such a difference will be described with reference to FIG. 5 which is an enlarged view of the turbine section 20 and FIG. 6 which is a diagram showing the relationship between the differential pressure ΔP and the opening area of the communication passage 21e. In FIG. 5, the same members and parts as those shown in FIG. 3 described above and parts, or equivalent members and parts, are given the same reference numerals as those shown in FIG.

  In the second embodiment, the first communication pipe 61a1 is configured to communicate the first scroll exhaust passage 21c2 and the first pressure chamber 61a, but instead, the groove 21d and the first pressure are communicated. It is conceivable that the chamber 61a is communicated (that is, the pressure of the exhaust gas in the groove 21d is used as the upstream pressure at the differential pressure ΔP) (hereinafter, this configuration is referred to as a “deformed configuration”). ). In this case, since the downstream end face of the groove portion 21d is formed in the vicinity of the throat portion T, the differential pressure in the choke generation start state becomes minute. For this reason, it is necessary to make the initial load of the spring 67 minute.

  By the way, the differential pressure ΔP increases as the intake air flow rate Ga increases. On the other hand, the intake air flow rate Ga varies according to the operating state of the engine or varies due to disturbance. For this reason, the differential pressure ΔP also varies with a predetermined variation width according to the variation of the intake air flow rate Ga. In the configuration described above, there may occur a case where the fluctuation range of the fluctuation of the differential pressure ΔP due to the fluctuation of the intake air flow rate Ga becomes larger than the differential pressure ΔP in the minute choke generation start state. In this case, due to the fluctuation of the differential pressure ΔP, there arises a problem that the valve element 65 opens even though the choke phenomenon does not occur.

  In order to avoid this, the differential pressure ΔP in the choke generation start state needs to be sufficiently larger than the fluctuation range of the fluctuation of the differential pressure ΔP due to the fluctuation of the intake air flow rate Ga. In other words, the distance from the downstream end face of the groove 21d to the position where the downstream pressure is introduced needs to be large. Based on such knowledge, in the third embodiment, the groove 21d is formed on the upstream side of the groove 21d in the second embodiment, and the first communication pipe 61a1 includes the groove 21d and the first pressure chamber 61a. To communicate.

  Thus, the differential pressure ΔP in the choke generation start state becomes a value ΔP2 (<the above value ΔP1) sufficiently larger than the fluctuation range, and the initial load of the spring 67 can be set to a load corresponding to the same value ΔP2. Therefore, when the differential pressure ΔP is smaller than the above value ΔP2, as shown in the relationship between the opening area of the communication passage 21e and the differential pressure ΔP shown in FIG. 6 corresponding to FIG. 4, the opening area of the communication passage 21e is “ 0 "is maintained. As a result, it is possible to avoid the problem that the valve element 65 opens due to the fluctuation of the differential pressure ΔP, although the choke phenomenon does not occur.

  As described above, according to the third embodiment of the variable capacity turbocharger according to the present invention, as in the second embodiment, the differential pressure ΔP is a value that is the differential pressure ΔP in the choke generation start state. Within the range of ΔP2 or more, the opening area of the communication passage 21e is adjusted to be larger as the differential pressure ΔP is larger. Thereby, when the differential pressure ΔP is equal to or greater than the value ΔP2, the degree to which the differential pressure ΔP deviates from the same value ΔP2 can be reduced. As a result, the upstream pressure can be suppressed from becoming very large, and the occurrence of knocking due to the occurrence of the choke phenomenon described above and the reduction in engine output can be suppressed. In addition, unnecessary opening of the valve body 65 due to fluctuations in the differential pressure ΔP due to fluctuations in the intake air flow rate Ga can be avoided more reliably than in the modified configuration.

  The present invention is not limited to the above embodiments, and various modifications can be adopted within the scope of the present invention. For example, in the second and third embodiments, the opening area of the communication path 21e is set by the differential pressure actuator 60 according to the pressure difference ΔP introduced from the first communication pipe 61a1 and the second communication pipe 61b1. However, instead of this, a butterfly control valve that adjusts the opening area of the same communication passage 21e as in the first embodiment and its actuator are provided at the downstream end of the turbine blade 23a. Pressure sensors that detect the pressure of exhaust gas are disposed at predetermined positions in the exhaust passage upstream from a certain throat portion T and at predetermined positions in the exhaust passage downstream from the throat portion T. The opening degree of the control valve may be electrically adjusted according to the differential pressure ΔP acquired from the above.

1 is a schematic view showing a variable capacity supercharger according to a first embodiment of the present invention. 3 is a graph showing a table that defines a relationship between a target value of the opening degree of a third control valve referred to by a CPU of an electric control device provided in the variable capacity supercharger shown in FIG. 1 and an intake air flow rate. It is an enlarged view of the turbine part with which the variable capacity | capacitance supercharger which concerns on 2nd Embodiment of this invention is provided. The relationship between the opening area of the communication path with which the variable capacity | capacitance supercharger which concerns on 2nd Embodiment of this invention is equipped, and the pressure difference of the exhaust gas in a 1st scroll exhaust passage, and the pressure of the exhaust gas downstream from a turbine impeller It is the graph which showed. It is an enlarged view of the turbine part with which the variable capacity | capacitance supercharger which concerns on 3rd Embodiment of this invention is provided. The graph which showed the relationship between the opening area of the communicating path with which the variable capacity | capacitance supercharger which concerns on 3rd Embodiment of this invention is equipped, and the pressure difference of the exhaust gas in a groove part, and the pressure of the exhaust gas downstream from a turbine impeller It is. FIG. 6 is a diagram for explaining the relationship between the air pressure in the intake passage of the engine, the operating speed of the engine, and the mass flow rate of air in the intake passage of the engine, and the occurrence of the choke phenomenon in the turbocharger according to the prior art. is there.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Turbine part, 21 ... Turbine housing, 21c2 ... 1st scroll exhaust passage, 21c3 ... 2nd scroll exhaust passage, 21d ... Groove part, 21e ... Communication passage, 23 ... Turbine impeller, 23a ... Turbine blade, 25 ... Westgate Passage 27: first control valve 27a ... first control valve actuator 28 ... second control valve 28a ... second control valve actuator 29 ... third control valve 29a ... third control valve actuator 30 ... compressor 33: Compressor impeller, 41: Air flow meter, 43 ... Pressure sensor, 45 ... First control valve opening sensor, 47 ... Second control valve opening sensor, 49 ... Third control valve opening sensor, 51 ... Crank position sensor, 60 ... Differential pressure actuator, 61 ... Casing, 61a ... First pressure chamber, 61b ... Second pressure chamber, 61a1 First communicating pipe, 61b1 ... second communication pipe, 63 ... diaphragm, 65 ... valve body, 67 ... spring, ECU ... electric control unit

Claims (5)

A turbine impeller,
A housing that accommodates the turbine impeller rotatably by inflow of all the exhaust gas discharged from the internal combustion engine into the accommodation chamber formed inside,
A compressor impeller for compressing air in the intake passage of the internal combustion engine rotated by rotation of the turbine impeller;
A variable capacity supercharger comprising a first adjusting means for adjusting a first opening area which is an opening area of an inflow port of exhaust gas flowing into the turbine impeller according to an operating state of the internal combustion engine. ,
One end is provided at a portion of the inner wall of the housing chamber that surrounds the blade portion of the turbine impeller from the outside in the radial direction, and a first bypass passage that bypasses a part of the exhaust gas in the blade portion downstream of the turbine impeller; ,
A second adjusting means that is interposed in the first bypass passage and adjusts a second opening area that is an opening area of the first bypass passage;
With
The second adjusting means includes
A variable capacity supercharger configured to adjust the second opening area such that the second opening area increases as the flow rate of air in the intake passage increases. In the variable capacity supercharger according to claim 1,
The second adjusting means includes
A variable capacity supercharger configured to set the second opening area to "0" when the flow rate of air in the intake passage is within a range where no choke phenomenon of exhaust gas in the blades occurs. A turbine impeller,
A housing that accommodates the turbine impeller rotatably by inflow of all the exhaust gas discharged from the internal combustion engine into the accommodation chamber formed inside,
A compressor impeller for compressing air in the intake passage of the internal combustion engine rotated by rotation of the turbine impeller;
A variable capacity supercharger comprising a first adjusting means for adjusting a first opening area which is an opening area of an inflow port of exhaust gas flowing into the turbine impeller according to an operating state of the internal combustion engine. ,
One end is provided at a portion of the inner wall of the housing chamber that surrounds the blade portion of the turbine impeller from the outside in the radial direction, and a first bypass passage that bypasses a part of the exhaust gas in the blade portion downstream of the turbine impeller; ,
A second adjusting means that is interposed in the first bypass passage and adjusts a second opening area that is an opening area of the first bypass passage;
With
The second adjusting means includes
The second opening area is adjusted so as to increase as the degree of difference between the exhaust gas pressure upstream of the downstream end of the blade and the exhaust gas pressure downstream of the turbine impeller increases. A variable capacity turbocharger configured as described above. The variable capacity supercharger according to claim 3,
The second adjusting means includes
The variable capacity supercharger configured to set the second opening area to "0" when the degree of difference is within a range in which the choke phenomenon of the exhaust gas in the blade portion does not occur. The variable capacity supercharger according to any one of claims 1 to 4,
A second bypass passage for bypassing a part of the exhaust gas upstream of the turbine impeller to the downstream side of the turbine impeller;
If the pressure of the air that is interposed in the second bypass passage and is compressed by the compressor impeller is below a predetermined pressure, the second bypass passage is shut off, and if the pressure of the air is greater than the predetermined pressure, the communication is established. Means to
Variable capacity turbocharger with

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