JP2005054750A - Turbocharged engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a turbocharged engine driving a waste gate valve in a closing direction at high engine load and opening the waste gate valve at low engine load in a practical use zone with a simple structure excellent in cost. <P>SOLUTION: An actuator 18 opening and closing the waste gate valve 17 uses intake air pressure at a downstream of a compressor in an intake air passage 5 as a drive source for waste gate valve action. When intake air pressure rise to a predetermined pressure or higher, the actuator 18 having a structure driving the waste gate valve 17 in the closing direction is used. Consequently, the waste gate valve 17 is driven in the closing direction at high engine load and the waste gate valve 17 can be opened at low engine load in the practical (normal) use zone of an engine 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a turbocharged engine that performs supercharging with a turbocharger.

  Among engines, there is a turbocharged engine equipped with a turbocharger (hereinafter referred to as a turbocharger) to improve output. Usually, a turbocharger installed in an engine has a turbine and a compressor connected to the turbine. Of these, the turbine is disposed in the exhaust passage of the engine, the compressor is disposed in the intake passage of the engine, the turbine is rotationally driven by exhaust energy, and the intake air is supercharged by the compressor connected to the turbine. Yes.

  Such turbocharged engines are usually equipped with a wastegate system that bypasses the exhaust gas to control the boost pressure. In many cases, an exhaust gas bypass passage that bypasses the turbine of the turbocharger is provided, and a normally closed waste gate valve is provided in the exhaust gas bypass passage. When the boost pressure exceeds the maximum boost pressure, the waste gate valve A structure that opens is used.

  However, such waste gate valves are closed in most practical areas such as steady running. For this reason, in the practical range, that is, in the partial range where the exhaust energy of the engine is low (low load operation) such as low load and low rotation, the turbocharger turbine becomes a resistance and the exhaust from the engine to the turbine is exhausted. There is a problem that the pressure (hereinafter referred to as exhaust pressure) is extremely increased, imposes an unnecessary burden on the engine, and deteriorates fuel consumption.

Therefore, in a turbocharged engine, an electronic control device such as a motor is used as an actuator, and a structure in which the wastegate valve is directly opened and closed by the electronic device is used, and it becomes a practical range by a control signal that can be given from the outside. A technique has been proposed in which a wastegate valve is opened when the engine is under a low load (see, for example, Patent Document 1). As a result, when the engine is under a low load, exhaust gas escapes from the exhaust gas bypass passage, and an increase in exhaust pressure that causes deterioration in fuel consumption is reduced.
Japanese Examined Patent Publication No. 7-45831

  Incidentally, electronic control devices such as motors are devices that are susceptible to thermal influence.

  However, for the convenience of directly driving the wastegate valve, the electronic control device is forced to be disposed around the wastegate valve, that is, at a point where the temperature becomes high due to the heat of exhaust gas. For this reason, the device has a problem in reliability. In addition, the electronic control device has a problem that the structure is complicated because extreme heat resistance is required, and the cost is high.

  Accordingly, an object of the present invention is to provide a turbocharged engine that has a simple and cost-effective structure, is driven in the closing direction when the engine is heavily loaded, and the wastegate valve is opened when the engine is under a low load, which is a practical range. There is to do.

  In order to achieve the above object, according to the first aspect of the present invention, an intake pressure downstream of the compressor in the intake passage is used as a drive source for operating the wastegate valve as an actuator for opening and closing the wastegate valve. When the pressure rises above the specified pressure, the waste gate valve is driven in the closing direction. When the engine is under heavy load, the waste gate valve is driven in the closing direction. The wastegate valve was opened when loaded.

  According to the second aspect of the present invention, in order to further improve the accuracy of the opening operation of the wastegate valve, the load detection means for further detecting the load of the engine, and the engine load detected by the load detection means is less than a predetermined value. In some cases, a configuration including waste gate valve control means for controlling the intake air pressure not to be introduced into the actuator was adopted.

  According to a third aspect of the present invention, in order to prevent supercharging by the turbocharger, the wastegate valve control means includes a supercharge introduced into the actuator when the engine load is equal to or higher than a predetermined upper limit value. A configuration with limited pressure was adopted.

  According to a fourth aspect of the present invention, the actuator is configured to keep the wastegate valve in a fully open position until the intake pressure rises to a predetermined pressure so that the exhaust gas of the engine is favorably bypassed from the exhaust bypass passage. Adopted.

  According to the first aspect of the present invention, the pressure-driven actuator that operates using the intake pressure downstream of the compressor as a drive source has a simple structure as compared with the structure that drives the wastegate valve with an electronic control device such as a motor. However, high heat resistance is ensured.

  Therefore, the wastegate valve can be driven in the closing direction when the engine is heavily loaded and opened in the practical range of the engine with a simple structure and excellent cost structure.

  According to the second aspect of the present invention, there is an effect that the wastegate valve can be "opened" with any engine less than the desired engine load.

  According to the third aspect of the present invention, there is an effect that it is possible to prevent the engine from being excessively supercharged.

  According to the fourth aspect of the invention, there is an effect that the exhaust pressure of the engine can be surely reduced when the engine is under a low load, which is a practical range of the engine.

[First Embodiment]
The present invention will be described below based on the first embodiment shown in FIGS.

  FIG. 1 shows a turbocharged engine for traveling mounted on, for example, an automobile (vehicle). Reference numeral 1 in FIG. 1 denotes an engine body (ENG .: hereinafter referred to as an engine). As the engine 1, for example, an electronically controlled fuel injection type reciprocating engine is used. That is, in this engine 1, when a piston reciprocates in a cylinder (none of which is shown), the intake / exhaust valves are opened and closed at a predetermined time, fuel is injected from an injector (none of which is shown), and predetermined combustion is performed. A cycle, for example, an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke is repeatedly performed to output power. Reference numeral 2 denotes an intake port for introducing intake air into a combustion chamber (not shown) of the engine 1, and 3 denotes an exhaust port for leading exhaust gas from the combustion chamber of the engine 1 to the outside. .

  On the other hand, 10 is a turbocharger (hereinafter referred to as a turbocharger). The turbocharger 10 is configured by, for example, assembling a turbine 12 at one end of a shaft 11 and assembling a compressor 13 at the other end. Of these, the turbine 12 is interposed, for example, in the middle of the exhaust passage 4 extending from the exhaust port 3 of the engine 1 to the outside. The compressor 13 is interposed in the passage portion upstream of the throttle valve 6 located in the middle of the intake passage 5 extending from the intake port 2 of the engine 1 to an air cleaner (not shown), specifically, in the middle of the intake passage 5, for example. . That is, in the turbocharger 10, the turbine 12 is rotated by the exhaust energy of the exhaust gas discharged from the engine 1, and the compressor 13 is driven by the rotational force obtained by the turbine 12, so that the intake air in the intake passage 5 is (Intake) is supercharged. Reference numeral 28 denotes a catalyst assembled downstream of the turbine in the exhaust passage 4.

  The exhaust passage 4 is provided with a waste gate system 15. The wastegate system 15 includes an exhaust bypass passage 16 (hereinafter referred to as a bypass passage 16) that bypasses the turbine 12 by connecting upper and downstream portions sandwiching the turbine 12, and a wastegate valve (W · G · V) 17 and an actuator 18 for opening and closing the waste gate valve 17.

  Of these, the wastegate valve 17 includes, for example, a cylindrical valve chamber 17b formed on the upstream side of the bypass passage 16 and extending in the flow direction, and a wall surface that is housed in the valve chamber 17b and forms the upstream end of the valve chamber 17b. The structure which combined the valve body 17a which opens and closes the opening-and-closing port 17c formed in this is used. As the valve body 17a, a swing type is used in which one side is swingably supported to open and close the open / close port 17c. Specifically, for example, the swing type valve element 17a is rotatable by a fulcrum portion 19 formed on a wall portion forming a corner portion on the upstream side of the valve chamber 17b as shown in an enlarged view in FIG. A position A1 (hereinafter referred to as a closed position A1) where the entire valve body 17a closes the open / close port 17c (hereinafter referred to as a closed position A1) and a position A2 (hereinafter referred to as an open position A2) where the open / close port 17c is opened (fully open). A structure that pivots and displaces between them is used. Further, for example, the end of the valve body 17 a on the fulcrum part 19 side extends linearly in a direction away from the fulcrum part 19 and forms a link part 14. Accordingly, when the end of the link portion 14 is pushed / pulled in the flow direction of the bypass passage 16, the valve body 17a is displaced between the closed position A1 and the open position A2, and the opening degree of the open / close port 17c is changed. It is done. That is, the amount of exhaust gas to be bypassed can be changed.

  The actuator 18 employs a pressure-driven structure that uses intake pressure (including supercharging pressure) as a drive source. For example, the actuator 18 has a structure as shown in an enlarged manner in FIG. The structure of the actuator 18 will be described. Reference numeral 20 denotes a cylindrical housing disposed in parallel with the valve chamber 17b at a point adjacent to the valve chamber 17b of the waste gate valve 17, for example. The housing 20 is formed, for example, by connecting the open ends of a pair of bottomed cylinders 21a and 21b facing each other. In addition, a diaphragm 23 that divides the two cylinders is sandwiched between the coupling parts of the cylinders 21a and 21b, and the internal space of the housing 20 is divided into two. The diaphragm 23 has a shape that can be deformed in the axial direction of the housing 20. A space on the downstream side in the flow direction of the bypass passage 16 with the diaphragm 23 interposed therebetween is an atmospheric communication chamber 24, and an opposite upstream space is an intake pressure introduction chamber 25. Of these, the atmosphere communication chamber 24 is opened to the atmosphere through, for example, an atmosphere communication port 26 formed on the bottom wall of the cylindrical body 21b. Further, in the atmosphere communication chamber 24, an elastic member, for example, a compression spring 27, for biasing the diaphragm 23 toward the intake pressure introduction chamber 25 is interposed.

  A driven rod 29 is disposed in the axial center portion (center) of the intake pressure introduction chamber 25. The follower rod 29 extends along the axial center direction of the intake pressure introduction chamber 25, and one end thereof is connected to, for example, the central portion of the diaphragm 23. The other end of the driven rod 29 penetrates through the center of the bottom wall of the cylindrical body 21a so as to advance and retreat, and protrudes out of the housing 20. This protruding end is rotatably connected to the end of the link portion 14 of the valve body 17a. 29a shows the connected portion. As a result, the valve body 17a is positioned at the open position A2 in the normal state by the spring force of the compression spring 27 transmitted to the link portion 14 (normally open type).

  In addition, a pressure introduction path 31 branched from a portion of the intake passage 5 downstream of the compressor 13, for example, a passage portion 5 a between the compressor 13 and the throttle valve 6, is connected to the peripheral wall portion of the intake pressure introduction chamber 25. . As a result, the intake pressure downstream of the compressor (atmospheric pressure to positive pressure (plus side): including supercharging pressure) is introduced into the intake pressure introduction chamber 25 partitioned by the diaphragm 23. With this structure, when the pressure in the intake pressure introduction chamber 25 exceeds the spring force of the compression spring 27, the diaphragm 23 is deformed (displaced) toward the atmosphere communication chamber 24 and the valve body 17a is fully opened. The position is displaced in the closing direction (the closing position A1 side). Using the behavior of the diaphragm 23, the waste gate valve 17 is driven in the opening direction until the intake pressure (including the supercharging pressure) rises to a predetermined pressure P1, and the intake pressure (including the supercharging pressure) is further increased. When the valve rises, the waste gate valve 17 is driven in the closing direction. Specifically, for the spring force of the compression spring 27, for example, a value selected from a range balanced with an intake positive pressure of 0 to 13.3 KPa is used. The wastegate valve 17 is kept in the fully open position until the intake pressure is less than the predetermined pressure P1 determined by the spring force (that is, the engine low load side). When the intake pressure is equal to or higher than the predetermined pressure P1 (that is, the engine high load side), the intake pressure ( The waste gate valve 17 is closed according to the supercharging pressure.

  A seal member 30 is provided between the bottom wall of the cylinder 21a and the driven rod 29 to keep the intake pressure introduction chamber 25 airtight.

  In such a turbocharged engine, combustion air is sucked from the suction port 2 as the piston reciprocates, and exhaust gas that has finished combustion is discharged from the exhaust port 3.

  At this time, the waste gate valve 17 is opened and closed by the driving force generated by the actuator 18.

  Specifically, the wastegate valve 17 is a pressure guided to the intake pressure introduction chamber 25 as shown by “W / G / V fully open region” in the diagram of FIG. 3, that is, an intake air upstream of the throttle valve 6. Until the pressure (including supercharging pressure) exceeds the spring force of the compression spring 27, specifically, the engine 1 is fully opened by the spring force of the compression spring 27 on the low load side including the practical range (normal range). Driven to state. When the pressure guided to the intake pressure introduction chamber 25 reaches the operating range of the engine 1 where the pressure exceeds the spring force (supercharging pressure: positive pressure), the intake pressure overcomes the spring force and deforms the diaphragm 23. The waste gate valve 17 in the fully opened position is driven in the closing direction. At this time, the opening degree of the wastegate valve 17 is closed according to the supercharging pressure as shown in “region where W, G, and V close according to the supercharging pressure” in the diagram of FIG. 3. Driven by.

  As a result, in a partial region where the exhaust energy of the engine is small, such as a low load and low rotation that are normally used, the exhaust gas from the engine 1 is a turbine of the turbocharger 10 that causes drive loss in order to improve fuel efficiency. 12 passes through the exhaust passage 4 while bypassing 12. In addition, by driving the wastegate valve 17 in the closing direction at a high engine load that requires supercharging, more exhaust gas can flow to the turbine 12 side of the turbocharger 10 and the turbine speed can be increased.

  The actuator 18 that opens (opens) the wastegate valve 17 in such a practical range is a structure (pressure-driven type) that operates using the supercharging pressure downstream of the compressor as a drive source. High heat resistance. In addition, the pressure-driven actuator 18 has a simpler heat-resistant structure than a motor or the like, and does not need to be controlled by an electronic device, so that the cost is low. In particular, the actuator 18 has a structure in which the wastegate valve 17 is kept in the fully open position until the intake pressure rises to a predetermined intake pressure. Therefore, when the engine 1 in a practical range is under a low load, the wastegate valve 17 is always fully opened. The exhaust gas can be bypassed, and the exhaust pressure of the engine 1 can be reliably prevented from increasing.

  In the first embodiment, the intake pressure in the upstream region of the intake passage 5 sandwiching the throttle valve 6 is introduced to the actuator 18, but this is not limiting, and the intake air pressure is not limited to this, as shown by the two-dot chain line in FIG. 1. The same effect can be obtained by adopting a structure in which the intake pressure in the downstream region of the passage 5 sandwiching the throttle valve 6 is introduced to the actuator 18.

[Second Embodiment]
4 to 6 show a second embodiment of the present invention.

  In the present embodiment, the intake pressure introduced into the actuator 18 is controlled as shown in FIG. 4 so that the wastegate valve 17 can be opened with any engine 1 less than the desired load of the engine 1. An electronic control system 35 is added to the configuration of the first embodiment.

  The electronic control system 35 combines, for example, a passage system 36 that can release the supercharging pressure (intake pressure) introduced into the actuator 18 and an introduction pressure control system 37 that controls the escape from the passage system 36. Structure is used. Specifically, the passage system 36 connects, for example, the pressure introduction passage 31 and the passage portion 5b upstream of the compressor of the intake passage 5 with a relief passage 38 and introduces an intake pressure (excess pressure) introduced into the pressure introduction passage 31. A structure in which a control valve (for example, a solenoid valve 39) is provided in the escape passage 38 to change the passage area of the escape passage 38 is used. In addition, for example, a structure in which an air flow sensor 40 that detects an intake air amount taken in from the intake passage 5 and an ECU 41 are combined is used for the introduction pressure control system 37. The ECU 41 has a function of obtaining volumetric efficiency EV (ratio of the amount of air sucked in one stroke and the stroke volume) corresponding to the engine load from the amount of intake air detected by the airflow sensor 40 (corresponding to the load detection means of the present application), When the volumetric efficiency EV is less than a predetermined engine load value, for example, less than a threshold value D1 that is a low load side determination of the engine 1 including a practical range (normal range), the solenoid valve 39 is fully opened and the actuator 18 is supercharged. Function for preventing pressure from being introduced (corresponding to the wastegate valve control means of the present application), volumetric efficiency EV is greater than or equal to threshold D1 and less than a predetermined upper limit of engine load D2 (D1 <D2) Is a function for adjusting the opening of the solenoid valve 39 to, for example, an opening set in advance according to the engine speed, and the volumetric efficiency EV is a predetermined upper limit value of the engine load. It becomes equal to or larger than threshold D2 by fully opening the solenoid valve 39 has a function of limiting the boost pressure introduced into the actuator 18. With these functions, the opening degree of the wastegate valve 17 is controlled as desired according to the operating range of the engine 1.

  A control flow of the solenoid valve 39 is shown in FIG. Explaining the control flow, as the engine 1 is operated, the ECU 41 obtains the volumetric efficiency EV according to the intake air amount detected by the airflow sensor 40 (step S1). Next, the detected volumetric efficiency EV is compared with a preset threshold value D1 (step S2). That is, whether or not the current operation of the engine 1 is on the low load side including the practical range (normal range) is determined based on whether or not it is less than the threshold value D1. If it is determined that the load is on the low load side, the solenoid valve 39 is fully opened (step S4).

  Then, the intake pressure (including the boost pressure) from the throttle upstream toward the actuator 18 is not introduced into the intake pressure introduction chamber 25 but is returned to the compressor upstream side of the intake passage 5 through the escape passage 38. As a result, the waste gate valve 17 is kept open by the spring force of the compression spring 27, specifically, kept fully open.

  As a result, the waste gate valve 17 is opened in the entire region on the low load region side of the engine 1, which is difficult only by setting the spring force of the compression spring 27, as shown in the diagram of FIG. Therefore, exhaust gas from the engine 1 is exhausted from the exhaust passage 4 while bypassing the turbine 12 of the turbocharger 10 that causes drive loss.

  Until the detected volumetric efficiency EV exceeds the threshold value D1 and is less than the threshold value D2 that is a predetermined upper limit value of the engine load, the opening degree of the solenoid valve 39 is set in advance according to the engine speed. It is narrowed to the opening degree (by control map etc.). Thereby, the opening degree of the solenoid valve 39 is adjusted so as to obtain a supercharging effect according to the engine speed (step S6). Then, a supercharging pressure (intake pressure) that overcomes the spring force of the compression spring 27 is introduced into the intake pressure introduction chamber 25. Thereby, the wastegate valve 17 operates in a closing direction according to the supercharging pressure, and an optimum supercharging operation corresponding to the engine load is performed as shown in the diagram of FIG.

  Further, when the volumetric efficiency EV becomes equal to or greater than a threshold value D2 that is a predetermined upper limit value of the engine load, the solenoid valve 39 is fully opened (step S4). Then, the boost pressure introduced into the intake pressure introduction chamber 25 is returned to the compressor upstream side of the intake passage 5 through the relief passage 38. As a result, the wastegate valve 17 is driven fully open by the spring force of the compression spring 27 to prevent the turbocharger 10 from being supercharged, that is, overcharged. The restriction area of the wastegate valve 17 at this time is indicated by the crossed oblique line “area where the closing operation of W, G, and V is restricted” in the diagram of FIG.

  If the engine load is detected and the intake pressure introduced into the actuator 18 is controlled, the engine 1 can be compared with a technique in which the wastegate valve 17 is “opened” depending on the compression spring 27 alone. However, the wastegate valve 17 can be reliably “open” when the engine is under a low load that is in a practical range. In addition, it is possible to prevent overcharging by a simple control of changing a part of the intake pressure introduction control (limitation of the supercharging pressure introduced into the actuator 18). Unlike the actuator 18 that directly drives the wastegate valve 17, the solenoid valve 39 and the ECU 41 do not need to be installed near the turbocharger 10, and there is no fear that the solenoid valve 39 and the ECU 41 are thermally affected.

  However, in the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the second embodiment, the volumetric efficiency EV is used to detect the load of the engine 1, but the present invention is not limited to this. As shown by a two-dot chain line in FIG. The load of the engine 1 may be detected using the throttle opening signal of the valve 6.

[Third Embodiment]
FIG. 7 shows a third embodiment of the present invention.

  Unlike the structure in which the follower rod 29 penetrates the intake pressure introducing chamber 25 as in the first and second embodiments, the present embodiment allows the follower rod 29 to advance and retreat. The actuator 18 is configured to be fully opened by penetrating and causing the spring force of the compression spring 27 to act on the wastegate valve 17. The actuator 18 having a different direction acting on the waste gate valve 17 has the same effect as the first and second embodiments described above. Further, since the driven rod 29 does not penetrate the intake pressure introduction chamber 25, the seal member 30 does not need to be airtight, and the structure can be simplified.

  In the third embodiment, the same parts as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted.

The figure which shows the structure of the turbocharged engine of the 1st Embodiment of this invention. Sectional drawing which expands and shows the actuator which drives the wastegate valve of the turbocharged engine. The diagram for demonstrating the operating range of the wastegate valve driven with the actuator. The figure which shows the structure of the turbocharged engine of the 2nd Embodiment of this invention. The flowchart explaining the action | operation of the solenoid which controls the actuator of the turbocharged engine. The diagram for demonstrating the operating range of the wastegate valve driven with the actuator. Sectional drawing which shows the principal part of the 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 5 ... Intake passage, 10 ... Turbo type supercharger, 12 ... Turbine, 13 ... Compressor, 16 ... Exhaust bypass passage, 17 ... Waste gate valve, 18 ... Actuator, 23 ... Diaphragm, 27 ... Compression spring, 39 ... Solenoid (waist gate valve control means), 40, 41 ... Air flow sensor, ECU (load detection means).

Claims (4)

A turbocharger in which a turbine is disposed in an exhaust passage of the engine and a compressor connected to the turbine is disposed in an intake passage of the engine, and supercharges intake air using exhaust energy of the engine; In a turbocharged engine comprising an exhaust bypass passage for bypassing a turbine of a turbocharger, a wastegate valve for opening and closing the exhaust bypass passage, and an actuator for opening and closing the wastegate valve,
The actuator uses an intake pressure downstream of the compressor in the intake passage as a drive source for operating the waste gate valve. When the intake pressure rises above a predetermined pressure, the actuator moves the waste gate valve in the closing direction by the intake pressure. A turbocharged engine configured to be driven.   Furthermore, load detection means for detecting the load of the engine, and wastegate valve control means for controlling the intake air pressure not to be introduced into the actuator when the engine load detected by the load detection means is less than a predetermined value; The turbocharged engine according to claim 1, comprising:   The said wastegate valve control means is comprised so that the intake pressure introduced into the said actuator may be restrict | limited when the said engine load is more than predetermined | prescribed upper limit. Turbocharged engine.   The turbocharger according to any one of claims 1 to 3, wherein the actuator is configured to keep the waste gate valve in a fully open position until the pressure is increased to the predetermined pressure. engine.

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