JP2016098653A - Engine with variable capacity supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine with a variable capacity supercharger capable of recirculating exhaust when the engine is in an operation state with pressure in an intake passage higher than the same in an exhaust passage.SOLUTION: An engine with a variable capacity supercharger comprises: pressure inverted region control means 8E which make throttle valve control means 8G close a throttle valve and bypass valve control means 8C open a bypass valve 71 when control of a variable nozzle vane 34 is executed by nozzle vane control means 8A, the control of an EGR valve 61 is executed by EGR valve control means 8B, and the engine is in an operation state with pressure in an intake passage at a downstream side of a compressor higher than the same in an exhaust passage at an upstream side of the variable nozzle vane 34.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an engine with a variable displacement supercharger, and more specifically to an engine with a variable displacement supercharger capable of exhaust gas recirculation.

  The applicant of the present application has proposed an engine with a variable displacement supercharger that is capable of exhaust gas recirculation when the operating state of the engine is in a state where the pressure of the intake passage is higher than the pressure of the exhaust passage. Such an engine with a variable displacement supercharger includes a variable displacement supercharger provided with a variable nozzle vane upstream of a turbine, an exhaust passage upstream of the turbine, and an intake passage downstream of a compressor of the variable displacement supercharger. An EGR passage that connects to the EGR passage, an EGR valve that adjusts an exhaust gas flow rate that is provided in the EGR passage and is supplied from an exhaust passage on the upstream side of the turbine to an intake passage on the downstream side of the compressor, and an intake passage on the downstream side of the compressor To a bypass passage connected to an exhaust passage between the variable nozzle vane and the turbine, a bypass valve interposed in the bypass passage for opening and closing the bypass passage, and an opening degree of the variable nozzle vane according to an operating state of the engine Nozzle vane control means, EGR valve control means for controlling the opening of the EGR valve in accordance with the operating state of the engine, engine And a, and the bypass valve control means for controlling the opening degree of the bypass valve according to the operating state. Further, in an engine with a variable capacity supercharger, variable nozzle vane control by the nozzle vane control means is executed, control of the EGR valve by the EGR valve control means is executed, and the operating state of the engine is changed in the intake passage. When the pressure is higher than the pressure in the exhaust passage, the bypass valve control means further includes a control device that opens the bypass valve (see, for example, Patent Document 1).

JP 2001-355502 A

However, in the engine with a variable displacement supercharger described above, the bypass passage has an air distribution path formed in the entire back surface side of the bearing plate embedded in the turbine housing, and an air formed in the entire width direction in the variable nozzle vane. Since the jet passage, the communication passage formed in the turbine housing, and the bypass pipe having one end connected to the communication passage, the structure is complicated.
In view of the above circumstances, the present invention is a variable displacement supercharger that is simple in structure and capable of exhaust gas recirculation when the operating state of the engine is in a state where the pressure in the intake passage is higher than the pressure in the exhaust passage. The purpose is to provide an aircraft engine.

  The present invention includes a variable displacement supercharger having a variable nozzle vane upstream of a turbine blade, an exhaust passage upstream of the variable nozzle vane, and an intake passage downstream of a compressor of the variable displacement supercharger. An EGR passage to be connected, an EGR valve that is interposed in the EGR passage and adjusts an exhaust gas flow rate supplied from an exhaust passage upstream of the variable nozzle vane to an intake passage downstream of the compressor, and upstream of the variable nozzle vane A bypass passage that is connected to an exhaust passage on the side of the turbine and an exhaust passage on the downstream side of the turbine blade, bypasses the variable nozzle vane and the turbine blade, and is bypassed to open and close the bypass passage. A valve, nozzle vane control means for controlling the opening of the variable nozzle vane according to the operating state of the engine, and the engine EGR valve control means for controlling the opening degree of the EGR valve according to the operating state of the engine, and bypass valve control means for controlling the opening degree of the bypass valve according to the operating state of the engine, the nozzle vane Control of the variable nozzle vane by the control means is executed, control of the EGR valve by the EGR valve control means is executed, and the operating state of the engine is such that the pressure in the intake passage downstream from the compressor is the variable nozzle vane. The bypass valve control means further includes a control device for opening the bypass valve when the pressure is higher than the pressure in the upstream exhaust passage.

  According to the present invention, when the operating state of the engine is such that the pressure in the intake passage downstream from the compressor is higher than the pressure in the exhaust passage upstream from the variable nozzle vane, the bypass valve is opened in the bypass valve control means. Since it is operated, a part of the exhaust gas is diverted to the bypass passage, and the inflow amount to the turbine rotor blade is adjusted. As a result, the supercharging pressure of the compressor decreases, the pressure in the intake passage downstream from the compressor becomes lower than the pressure in the exhaust passage upstream from the variable nozzle vane, and the downstream of the compressor from the exhaust passage upstream from the variable nozzle vane. Exhaust gas is introduced into the intake passage and exhaust gas recirculation becomes possible.

In one aspect of the present invention, a throttle valve that is provided in an intake passage on the downstream side of the compressor, opens and closes the intake passage, and throttle valve control means that controls the opening of the throttle valve in accordance with the operating state of the engine The control device causes the throttle valve control means to close the throttle valve when the bypass valve control means causes the bypass valve to open.
In this way, when the operating state of the engine is such that the pressure in the intake passage downstream from the compressor is higher than the pressure in the exhaust passage upstream from the variable nozzle vane, the bypass valve is opened in the bypass valve control means. In addition, the throttle valve control means causes the throttle valve to be closed, so that a part of the exhaust gas is diverted to the bypass passage and the intake flow rate taken into the engine is limited. As a result, the bypass valve and the throttle valve are coordinated and controlled according to the operating state of the engine, and the turbine rotational speed is reduced less when a part of the exhaust gas is diverted to the bypass valve when the bypass valve is opened. Is also possible.

In one aspect of the present invention, the control device causes the bypass valve control means to open the opening of the bypass valve to a small opening when the operating state of the engine is at least a medium rotating load.
In this way, when the engine is operating at a mid-rotating load and the pressure in the intake passage downstream from the compressor is higher than the pressure in the exhaust passage upstream from the variable nozzle vane, the bypass is performed. Since the valve control means is operated to open the bypass valve with a small opening, a part of the exhaust gas is diverted to the bypass passage, and the inflow amount to the turbine rotor blade is adjusted. As a result, the supercharging pressure of the compressor decreases, the pressure in the intake passage downstream from the compressor becomes lower than the pressure in the exhaust passage upstream from the variable nozzle vane, and the downstream of the compressor from the exhaust passage upstream from the variable nozzle vane. Exhaust gas is introduced into the intake passage and exhaust gas recirculation becomes possible.

In one aspect of the present invention, the nozzle vane control means sets the opening of the variable nozzle vane within a range from a small opening to a medium opening when the engine operating state is a medium rotating load.
In this way, the flow rate of the exhaust gas supplied to the turbine rotor blades when the engine operating state is a medium rotating load is increased, and the supercharging effect by the compressor can be enhanced.

In one aspect of the present invention, the control device further causes the bypass valve control means to open the bypass valve and increase the rotational speed of the engine when the operating state of the engine is overloaded. Accordingly, the opening of the bypass valve is set to a large opening.
In this way, when the engine operating state is overloaded, the bypass valve control means opens the bypass valve, so that a part of the exhaust gas is diverted to the bypass passage and supplied to the turbine blades. The flow rate is adjusted. Thereby, the supercharging pressure of the compressor is reduced, and the compressor can be prevented from exceeding the flow limit (choke line).

In one aspect of the present invention, the nozzle vane control means and the bypass valve control means control the opening degree of the variable nozzle vane and the bypass valve based on a map in which the opening degree is associated with the engine speed and the load. .
In this way, since the opening degree of the variable nozzle vane and the bypass valve is controlled based on the map in which the opening degree is related to the engine speed and the load, the variable nozzle vane and the bypass valve can be changed by changing the map. The opening can be easily changed.

  As described above, according to the present invention, when the operating state of the engine is in a state where the pressure of the intake passage downstream of the compressor is higher than the pressure of the exhaust passage upstream of the turbine, the bypass valve control means Since the bypass valve is opened, a part of the exhaust gas is diverted to the bypass passage, and the amount of inflow into the turbine is adjusted. As a result, the supercharging pressure of the compressor decreases, the pressure in the intake passage downstream from the compressor becomes lower than the pressure in the exhaust passage upstream from the variable nozzle vane, and the intake air downstream from the compressor from the exhaust passage upstream from the turbine. Exhaust gas is introduced into the passage to enable exhaust gas recirculation.

It is a mimetic diagram showing the machine composition of the engine with a variable capacity type supercharger concerning the embodiment of the present invention. It is sectional drawing which shows the principal part of the variable capacity | capacitance supercharger shown in FIG. It is the III-III arrow directional view of the principal part of the variable capacity | capacitance supercharger shown in FIG. It is a block diagram which shows the control structure of the engine with a variable displacement supercharger shown in FIG. It is a flowchart which shows the control procedure of the control apparatus shown in FIG. It is a figure which shows the operation | movement map of the variable nozzle vane and bypass valve which were shown in FIG. It is a figure which shows the performance curve of the compressor considered when selecting a variable displacement supercharger. It is a figure which shows the performance curve of the compressor considered when selecting the variable capacity | capacitance supercharger which concerns on embodiment of this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments suitable for an engine with a variable displacement supercharger according to the invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this embodiment, and all the structures demonstrated by this embodiment are not essential as a solution means of this invention. Further, in the present embodiment, the configuration, structure, and control specifications shown in the present embodiment are changed according to the required performance and function within a range where the effects of the present invention can be obtained.

  FIG. 1 is a schematic diagram showing a mechanical configuration of an engine with a variable displacement supercharger according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a main part of the variable capacity supercharger shown in FIG. 1, and FIG. 3 is a view taken along the line III-III of the variable capacity supercharger shown in FIG. .

  An engine with a variable displacement supercharger according to an embodiment of the present invention can be mounted in general automobiles, and as shown in FIG. 1, an engine body 2, a variable displacement supercharger 3, an exhaust passage 4, an intake passage. 5, a throttle valve 54, an EGR passage 6, an EGR valve 61, a bypass passage 7, and a bypass valve 71 are provided.

  The engine body 2 may be a gasoline engine in addition to a diesel engine. Here, the variable capacity supercharger 3 effectively increases engine output, downsizing, and improves fuel efficiency. The description will be made assuming a multi-cylinder diesel engine mounted on middle class passenger cars. However, the present invention is not limited to this.

  As shown in FIG. 2, the variable capacity turbocharger 3 (hereinafter also referred to as “VG turbo 3”) is referred to as a variable capacity turbo or a variable nozzle turbo, and includes a turbine 31 and a compressor 36. Yes.

  The turbine 31 is for driving the compressor 36 using the internal energy of the exhaust gas discharged from the engine body 2, and as shown in FIGS. 2 and 3, the turbine 31 of the variable capacity supercharger 3. Includes a housing (turbine housing) 32 and a turbine blade (turbine impeller) 33 rotatably accommodated in the turbine housing 32, as well as a variable nozzle vane 34 (hereinafter referred to as "VG") that varies the exhaust gas passage area in the turbine housing 32. Vane 34 "). The opening degree of the variable nozzle vane 34 can be arbitrarily adjusted by an actuator 35 (see FIG. 1) provided outside the turbine housing 32, and is adjusted to an arbitrary opening degree according to a command from the control device 8 described later. Thereby, the variable nozzle vane 34 arbitrarily changes the exhaust gas passage area in the turbine housing 32.

  The compressor 36 is for supplying compressed air to the engine body 2 and rotatably accommodates a compressor blade (compressor impeller) (not shown) provided coaxially with the turbine impeller 33 and a compressor impeller. A housing (compressor housing) (not shown). Thereby, the variable capacity type supercharger 3 controls the flow rate to the turbine impeller 33 by changing the exhaust gas passage area in the turbine housing 32 according to the engine speed, thereby enhancing the supercharging effect. .

  The exhaust passage 4 is for exhausting exhaust gas exhausted from each cylinder (not shown) provided in the engine body 2 to the outside. As shown in FIG. 1, an exhaust manifold 41, an exhaust pipe 42, It has.

  The exhaust manifold 41 is a multi-tracheal tube that collects exhaust gas discharged from each cylinder provided in the engine main body 2, and the exhaust manifold 41 according to the present embodiment includes the engine main body 2 and a variable capacity supercharger. Between the three turbines 31. As a result, the exhaust gases discharged from the cylinders provided in the engine body 2 are collected together and supplied to the turbine 31 of the variable capacity supercharger 3.

  The exhaust pipe 42 is a single pipe that detoxifies exhaust gas collected by the exhaust manifold 41 and discharges it to the outside. The exhaust pipe 42 according to this embodiment is a turbine 31 of the variable capacity turbocharger 3. It is provided downstream. As a result, the exhaust gas supplied to the turbine 31 of the variable capacity turbocharger 3 passes through the variable nozzle vane 34 and rotates the turbine impeller 33, and then is discharged outside through the exhaust pipe 42.

  The intake passage 5 is for supplying air supplied from the outside to each cylinder provided in the engine body 2, and includes an intake pipe 51 and an intake manifold 52. The intake pipe 51 is a single pipe that cleans and sucks external air, and the intake pipe 51 according to the present embodiment is provided upstream of the compressor 36 of the variable displacement supercharger 3. As a result, the purified air passes through the intake pipe 51 and is supplied to the compressor 36 of the variable displacement supercharger 3.

  The intake manifold 52 is a multi-air pipe that distributes air to each cylinder provided in the engine body 2, and the intake manifold 52 according to this embodiment is provided downstream of the compressor 36 of the variable capacity supercharger 3. The intercooler 53 and the engine body 2 are provided. As a result, the air supplied to the compressor 36 of the variable displacement turbocharger 3 is compressed by the compressor 36 and cooled by the intercooler 53, and then passes through the intake manifold 52 to each cylinder provided in the engine body 2. Distributed to.

  The throttle valve 54 is for adjusting the amount of intake air (air) flowing into the engine body 2 and adjusting the output of the engine body 2. The throttle valve 54 includes an intake passage 5 on the downstream side of the compressor 36, an intercooler 53, and the like. It is interposed between the intake manifold 52. The throttle valve 54 can be opened and closed and can be adjusted to an arbitrary opening degree, and is adjusted to an arbitrary opening degree according to a command from the control device 8 to be described later.

  The EGR passage 6 is a passage for supplying part of the exhaust gas discharged from the engine body 2 to the engine body 2 again for the purpose of reducing nitrogen oxide (NOX) in the exhaust gas and improving fuel efficiency. In the embodiment, the variable capacity turbocharger 3 is connected to an exhaust manifold 41 upstream of the turbine 31 and an intake manifold 52 downstream of the compressor 36.

  The EGR valve 61 is for adjusting the flow rate of exhaust gas supplied from the exhaust side of the engine body 2 to the intake side of the engine body 2, and is interposed in the EGR passage 6. The EGR valve 61 can be opened and closed and can be adjusted to an arbitrary opening degree, and is adjusted to an arbitrary opening degree according to a command from the control device 8 to be described later.

  The bypass passage 7 is for bypassing the turbine 31 of the variable capacity supercharger 3, and is connected to an exhaust manifold 41 on the upstream side of the turbine 31 and an exhaust pipe 42 on the downstream side of the turbine 31. Yes.

  The bypass valve 71 is for adjusting the exhaust gas flow rate for bypassing the turbine 31 of the variable capacity supercharger 3, and is interposed in the bypass passage 7. The bypass valve 71 can be opened and closed and can be adjusted to an arbitrary opening degree, and is adjusted to an arbitrary opening degree according to a command from the control device 8 to be described later.

FIG. 4 is a block diagram showing a control configuration of the engine with the variable displacement supercharger shown in FIG.
The engine with a variable capacity supercharger according to the present embodiment corresponds to the engine operating state including the engine speed, engine load, intake passage pressure (intake pressure), and exhaust passage pressure (exhaust pressure). The throttle valve 54, the variable nozzle vane 34, the EGR valve 61, and the bypass valve 71 are controlled. Various controls of the engine with a variable capacity supercharger according to this embodiment are performed by a control device (ECU (Engine Control) shown in FIG. Unit)) 8.

  The control device 8 includes a CPU (not shown) that executes various arithmetic processes, a ROM (not shown) that stores programs and data necessary for the control, and a RAM (not shown) that temporarily stores the calculation results of the CPU. And an input / output port (not shown) for inputting / outputting signals to / from the outside. The engine speed detector 81, the engine load detector 82, the intake passage pressure detector 83, and the exhaust passage detector 84 are connected to the input port, and the throttle valve 54 and the variable nozzle vane 34 described above are connected to the output port. The EGR valve 61 and the bypass valve 71 are connected. As shown in FIG. 4, the control device 8, that is, the CPU, the ROM, and the RAM constitutes a throttle valve control means 8G, a nozzle vane control means 8A, an EGR valve control means 8B, and a bypass valve control means 8C.

  The throttle valve control means 8G is for controlling the opening degree of the throttle valve 54, and the opening degree of the throttle valve 54 is controlled based on the depression amount of the accelerator or the like.

  The nozzle vane control means 8A is for controlling the opening degree of the variable nozzle vane 34 in accordance with the operating state of the engine. The opening degree of the variable nozzle vane 34 is controlled based on the engine speed and the engine load. The More specifically, the opening degree of the variable nozzle vane 34 is controlled based on a map (see FIG. 6) in which the opening degree of the variable nozzle vane 34 is associated with the engine speed and the engine load. The opening of the variable nozzle vane 34 is about 70 to 100% large opening and about 30 to about 70% medium opening when the maximum opening of the variable nozzle vane 34 is 100% and the minimum opening is 0%. The opening degree is set to 0 to about 30% as a small opening degree, but can be arbitrarily set if there is a relation of large, medium and small.

  The EGR valve control means 8B is for controlling the opening degree of the EGR valve 61 according to the operating state of the engine. The opening degree of the EGR valve 61 is controlled based on the engine speed and the engine load. Is done.

  The bypass valve control means 8C is for controlling the opening degree of the bypass valve 71 in accordance with the operating state of the engine. The opening degree of the bypass valve 71 is controlled based on the engine speed and the engine load. Is done. More specifically, the opening degree of the bypass valve 71 is controlled based on a map (see FIG. 6) in which the opening degree of the bypass valve 71 is associated with the engine speed and the engine load. Here, with respect to the opening degree of the bypass valve 71, when the maximum opening degree of the bypass valve 71 is 100%, the opening degree is about 70 to 100%, the opening degree is about 30 to about 70%, and the opening degree is about 0 to about 30. % Is a small opening, but can be arbitrarily set if there is a relation of large, medium and small.

  Further, the control device 8 controls the bypass valve control means 8C in the region where the variable nozzle vane 34 is controlled by the nozzle vane control means 8A and the turbine impeller 33 is not rotated or is extremely low speed which does not contribute to improvement of engine performance. An extremely low rotation region control means 8D for opening the bypass valve 71 is provided. The degree of opening of the bypass valve 71 that the bypass valve control means 8C opens in the region where the turbine impeller 33 does not rotate or is extremely low which does not contribute to improving engine performance (hereinafter also referred to as “very low rotation region”) It is controlled based on the engine speed and engine load. Specifically, the opening degree of the bypass valve 71 is controlled based on a map (see FIG. 6) associated with the engine speed and the engine load. In this embodiment, the opening degree of the bypass valve 71 is fully open. Controlled to open.

  Further, the control device 8 executes control of the variable nozzle vane 34 by the nozzle vane control means 8A, control of the EGR valve 61 by the EGR valve control means 8B, and the engine operating state is on the downstream side of the compressor 36. When the pressure in the intake passage 5 is higher than the pressure in the exhaust passage 4 upstream of the turbine 31 (hereinafter also referred to as “pressure reversal region”), the bypass valve control means 8C opens the bypass valve 71. Pressure reverse region control means 8E is provided. The opening degree of the bypass valve 71 that is opened by the bypass valve control means 8C in the pressure reversal region is controlled based on the engine speed and the engine load. Specifically, the opening degree of the bypass valve 71 is controlled based on a map (see FIG. 6) associated with the engine speed and the engine load. When the above is true, the opening of the bypass valve 71 is controlled to open at a small opening. Further, the pressure reverse rotation region control means 8E may include means for causing the throttle valve control means 8G to close the throttle valve 54 when the bypass valve control means 8C opens the bypass valve 71.

  Further, the control device 8 includes a flow rate limit control unit 8F that opens the bypass valve 71 in the bypass valve control unit 8C when the engine load becomes overloaded and the flow rate of the compressor 36 approaches the flow rate limit. The opening degree of the bypass valve 71 opened by the bypass valve control means 8C when the compressor 36 approaches the flow limit is controlled based on a map (see FIG. 6) associated with the engine speed and the engine load. Is done. In the present embodiment, control is performed so that the opening is performed with a small opening at a low rotation, an intermediate opening at a middle rotation, and a large opening at a high rotation.

  FIG. 5 is a flowchart showing a control procedure of the control device shown in FIG. 4, and FIG. 6 is a diagram showing an operation map of the variable nozzle vane and the bypass valve shown in FIG. 5 and 6, the variable nozzle vane is represented as “VG” and the bypass valve is represented as “B / V”.

  As shown in FIG. 5, when the engine with a variable displacement supercharger according to the present embodiment is started, the nozzle vane control means 8A executes control of the variable nozzle vane 34, and the EGR valve control means 8B controls the EGR valve 61. Are executed (step S1 and step S2). Immediately after the engine is started, the engine is extremely low in rotation and has a very small load. Therefore, the turbine impeller 33 of the variable capacity supercharger 3 is not rotated or is in an extremely low rotation region that does not contribute to improvement in engine performance (step S3: YES). ). Therefore, the extremely low rotation region control means 8D causes the bypass valve control means 8C to open the bypass valve 71 (step S4).

  The opening degree of the bypass valve 71 opened by the bypass valve control means 8C is controlled based on the engine speed and the engine load in a region where the turbine impeller 33 is non-rotating or extremely low speed that does not contribute to improvement in engine performance. Is done. Specifically, the opening degree of the bypass valve 71 is controlled based on a map (see FIG. 6) associated with the engine speed and the engine load. Therefore, the bypass valve control means 8C according to the present embodiment controls the opening degree of the bypass valve 71 to be fully open, and the nozzle vane control means 8A controls the opening degree of the variable nozzle vane 34 to be the minimum opening degree. To do. As a result, the exhaust gas discharged from the engine body 2 is discharged from the exhaust manifold 41 through the bypass passage 7 to the exhaust pipe 42, and the turbine impeller 33 of the variable displacement turbocharger 3 is prevented from becoming a resistance. it can.

  Then, when the turbine impeller 33 goes through a region where the turbine impeller 33 does not rotate or does not contribute to improvement of engine performance (step S3: NO) and the engine accelerates (step S5: YES), the bypass valve control means 8C performs bypass valve 71. Is fully closed (step S6). Thereby, the exhaust gas discharged from the engine body 2 passes through the turbine impeller 33 of the variable capacity supercharger 3 and is discharged to the exhaust pipe 42.

  Further, even if the turbine impeller 33 passes through a region where the turbine impeller 33 does not rotate or does not contribute to improving engine performance (step S3: NO) and the engine does not accelerate (step S5: NO), the intake air on the downstream side of the compressor 36 If the pressure in the passage 5 does not become higher than the pressure in the exhaust passage 4 upstream from the variable nozzle vane 34 (step S7: NO), the bypass valve control means 8C fully closes the bypass valve 71 (step S8).

  On the other hand, when the engine is not accelerated (step S5: NO) and the pressure in the intake passage 5 downstream from the compressor 36 is higher than the pressure in the exhaust passage 4 upstream from the variable nozzle vane 34 (step S7: YES), the pressure The reverse rotation region control means 8E causes the bypass valve control means 8C to open the bypass valve 71. When the pressure in the intake passage 5 on the downstream side of the compressor 36 becomes higher than the pressure in the exhaust passage 4 on the upstream side of the variable nozzle vane 34, the opening degree of the bypass valve 71 opened by the bypass valve control means 8C depends on the engine speed and the engine. And control based on the load.

  Specifically, the opening degree of the bypass valve 71 is controlled based on a map (see FIG. 6) associated with the engine speed and the engine load. In this embodiment, on the condition that the engine is not overloaded (step S9: NO), when the engine speed is low (step S10: YES), the opening degree of the bypass valve 71 is reduced from the fully closed state to the small amount. The opening is controlled to be the opening degree (step S11). When the engine speed is medium (step S12), the opening of the bypass valve 71 is controlled so as to change from fully closed to medium (step S13), and the engine speed is not medium. That is, when the engine speed is high (step S12: NO), the opening degree of the bypass valve 71 is controlled so as to change from fully closed to a large opening degree (step S14).

  Thus, at least when the engine is at medium speed or medium load, the opening degree of the bypass valve 71 is controlled so as to change from fully closed to a small opening degree (see FIG. 6), and the opening degree of the variable nozzle vane 34 is small. It is controlled in the range from the opening to the middle opening.

  As a result, part of the exhaust gas discharged from the engine body 2 is discharged from the exhaust manifold 41 through the bypass passage 7 to the exhaust pipe 42, and the rotation of the turbine impeller 33 is suppressed. When the rotation of the turbine impeller 33 is suppressed in this way, the rotation of the compressor impeller is also suppressed, so that the pressure in the intake passage 5 downstream from the compressor 36 eventually becomes the pressure in the exhaust passage 4 upstream from the variable nozzle vane 34. A part of the exhaust gas is supplied from the exhaust passage 4 upstream of the variable nozzle vane 34 through the EGR passage 6 to the intake passage 5 downstream of the compressor 36, and the exhaust gas is recirculated.

  The pressure reverse rotation region control means 8E may cause the throttle valve control means 8G to close the throttle valve 54 when the bypass valve control means 8C opens the bypass valve 71. Specifically, the pressure reverse rotation region control means 8E controls the bypass valve control means 8C and the throttle valve control means 8G in a coordinated manner, and a part of the exhaust gas is diverted to the bypass passage 7 by opening the bypass valve 71. The recirculation amount of the exhaust gas may be ensured while controlling the decrease in the rotational speed of the turbine 31 due to the above.

  Further, in the present embodiment, a part of exhaust gas (EGR) is introduced in the middle rotation or middle load region. However, for example, in a rotation region higher than the middle rotation where the exhaust gas pressure becomes higher or a load region higher than the middle load. EGR may be introduced with the variable nozzle vane 34 having a large opening.

  On the other hand, when the engine load is overloaded (step S9: YES) and the flow rate of air supercharged by the compressor 36 approaches the flow limit, the flow limit control means 8F sets the bypass valve 71 to the bypass valve control means 8C. Open. The opening degree of the bypass valve 71 that is opened by the bypass valve control means 8C when the flow rate of the air supercharged by the compressor 36 approaches the flow limit is controlled based on the engine speed and the engine load. . Specifically, the opening degree of the bypass valve 71 is controlled based on a map (see FIG. 6) associated with the engine speed. The bypass valve control means 8C according to the present embodiment is controlled so that the opening degree of the bypass valve 71 becomes a small opening degree when the engine speed is low (step S15: YES) (step S16). ). When the engine speed is medium (step S17), the opening of the bypass valve 71 is controlled to be medium (step S18). When the engine speed is not medium, that is, When the engine speed is high (step S17: NO), the opening degree of the bypass valve 71 is controlled to be a large opening degree (step S19).

FIG. 7 is a diagram illustrating a performance curve of a compressor that is considered when selecting a variable displacement supercharger, and FIG. 8 is a compressor that is considered when selecting a variable displacement turbocharger according to the embodiment of the present invention. It is a figure which shows a performance curve.
As shown in FIG. 7, the variable displacement supercharger is selected so that the compressor 36 operates in a region surrounded by the surge line SL and the choke line CL in the operating range of the engine. Therefore, the variable capacity supercharger 3 is selected so that the compressor 36 operates in a range from the low rotation to the high rotation of the engine and from a low load to a high load. As described above, when the variable displacement supercharger is selected so that the compressor 36 operates in the range from the low rotation to the high rotation of the engine and from the low load to the high load, the compressor 36 can be operated in an efficient region. Cannot operate.

  On the other hand, the variable displacement supercharger-equipped engine according to the embodiment of the present invention includes the bypass valve 71. Therefore, as shown in FIG. 8, the variable displacement supercharger 3 has an area where the compressor 36 is efficient. You can choose to work with. Thus, if the compressor 36 is selected to operate in an efficient region, the air flow rate and the supply air pressure ratio approach the choke line CL when the engine is rotated at a high speed. In this case, in the engine with a variable displacement supercharger according to the embodiment of the present invention, the flow rate limit control means 8F causes the bypass valve control means 8C to open the bypass valve 71, so that the air flow rate and the supply pressure ratio are The compressor 36 will not exceed the choke line CL.

  As described above, in the engine with a variable displacement supercharger according to the embodiment of the present invention, the variable nozzle vane 34 is controlled by the nozzle vane control means 8A, and the turbine impeller 33 is non-rotating or the engine performance is improved. Since the bypass valve 71 is opened by the bypass valve control means 8C in a region where the rotation is extremely low and does not contribute, the exhaust gas bypasses the turbine impeller 33 and avoids the turbine impeller 33 becoming a resistance. Thereby, the scavenging of the exhaust gas can be improved even in the extremely low rotation region where the turbine impeller 33 does not rotate or contributes to the improvement of the engine performance.

  Further, when the engine is operating at a very low rotation and a very small load, the bypass valve control means 8C is operated to open the bypass valve 71 fully open, so that the exhaust gas bypasses the turbine impeller 33 and the turbine impeller 33 To avoid resistance. Thereby, the scavenging of the exhaust gas can be improved even in the extremely low rotation region where the turbine impeller 33 does not rotate or contributes to the improvement of the engine performance.

  Further, when the engine is operating at a very low rotation and a minimal load, the opening of the variable nozzle vane 34 is set to the minimum opening, so that the exhaust gas distributed to the turbine impeller 33 is minimized, and most of the exhaust gas is a turbine impeller. 33 is bypassed to prevent the turbine impeller 33 from becoming a resistance. Thereby, the scavenging of the exhaust gas can be improved even in the extremely low rotation region where the turbine impeller 33 does not rotate or contributes to the improvement of the engine performance.

Further, when the operating state of the engine is such that the pressure in the intake passage 5 downstream of the compressor 36 is higher than the pressure in the exhaust passage 4 upstream of the variable nozzle vane 34, the bypass valve 71 is provided with the bypass valve 71. Is opened, a part of the exhaust gas is diverted to the bypass passage 7 and the amount of inflow into the turbine impeller 33 is adjusted. As a result, the supercharging pressure of the compressor 36 decreases, the pressure of the intake passage 5 downstream of the compressor 36 becomes lower than the pressure of the exhaust passage 4 upstream of the variable nozzle vane 34, and the exhaust passage upstream of the variable nozzle vane 34. 4, exhaust gas is introduced into the intake passage 5 downstream of the compressor 36, and exhaust gas recirculation becomes possible.
When the pressure reverse rotation region control means 8E causes the bypass valve control means 8C to open the bypass valve 71, if the throttle valve control means 8G closes the throttle valve 54, the decrease in the rotational speed of the turbine 31 is reduced. It becomes possible to secure the recirculation amount of exhaust gas while controlling.

  Specifically, the operating state of the engine is not less than medium rotation or medium load, and the pressure of the intake passage 5 downstream of the compressor 36 is higher than the pressure of the exhaust passage 4 upstream of the variable nozzle vane 34. Since the bypass valve control means 8C opens the bypass valve 71 with a small opening, a part of the exhaust gas is diverted to the bypass passage 7 and the inflow amount to the turbine impeller 33 is adjusted. . As a result, the supercharging pressure of the compressor 36 decreases, the pressure of the intake passage 5 downstream of the compressor 36 becomes lower than the pressure of the exhaust passage 4 upstream of the variable nozzle vane 34, and the exhaust passage upstream of the variable nozzle vane 34. 4, exhaust gas is introduced into the intake passage 5 downstream of the compressor 36, and exhaust gas recirculation becomes possible. If the pressure reversal region control means 8E controls the bypass valve control means 8C and the throttle valve control means 8G in a coordinated manner and a part of the exhaust gas is diverted to the bypass passage 7 by opening the bypass valve 71, It becomes possible to ensure the recirculation amount of the exhaust gas while controlling the decrease in the rotational speed to a low level.

  Further, when the engine operating state is overloaded, the bypass valve 71 is opened by the bypass valve control means 8C, so that a part of the exhaust gas is diverted to the bypass passage 7 and the flow rate to the turbine impeller 33 is adjusted. The As a result, the supercharging pressure of the compressor 36 is reduced, and the compressor 36 can be prevented from exceeding the flow limit (choke line).

  Moreover, since the opening degree of the variable nozzle vane 34 and the bypass valve 71 is controlled based on the map (see FIG. 6) in which the opening degree is associated with the engine speed and the load, the variable nozzle vane can be changed by changing the map. 34 and the opening degree of the bypass valve 71 can be easily changed.

  As mentioned above, although one embodiment of the present invention has been described, of course, the present invention is not limited to the above-described embodiment, and addition, omission, replacement, etc., of a configuration is possible without departing from the spirit of the present invention. And other changes are possible.

  As described above, in the engine with a variable displacement supercharger according to the present invention, the operating state of the engine is such that the pressure in the intake passage downstream from the compressor is higher than the pressure in the exhaust passage upstream from the variable nozzle vane. Since the exhaust gas can be recirculated even when the engine is in the range, it is effective in improving fuel consumption and reducing NOX contained in the exhaust gas.

2 Engine body 3 Variable capacity turbocharger (VG turbo)
31 Turbine 32 Turbine housing 33 Turbine impeller (turbine blade)
34 Variable nozzle vane (VG vane)
35 Actuator 36 Compressor 4 Exhaust passage 41 Exhaust manifold 42 Exhaust pipe 5 Intake passage 51 Intake pipe 52 Intake manifold 53 Intercooler 54 Throttle valve 6 EGR passage 61 EGR valve 7 Bypass passage 71 Bypass valve 8 Control device 8A Nozzle vane control means 8B Valve control Means 8C Bypass valve control means 8D Extremely low rotation area control means 8E Pressure reverse rotation area control means 8F Flow rate limit control means 8G Throttle valve control means 81 Engine speed detector 82 Engine load detector 83 Intake passage pressure detector 84 Exhaust passage detection vessel

Claims (6)

A variable displacement supercharger with a variable nozzle vane upstream of the turbine blade,
An EGR passage connecting an exhaust passage on the upstream side of the variable nozzle vane and an intake passage on the downstream side of the compressor of the variable displacement supercharger;
An EGR valve which is interposed in the EGR passage and adjusts an exhaust gas flow rate supplied from an exhaust passage upstream of the variable nozzle vane to an intake passage downstream of the compressor;
A bypass passage connected to an exhaust passage on the upstream side of the variable nozzle vane and an exhaust passage on the downstream side of the turbine blade, and bypassing the variable nozzle vane and the turbine blade;
A bypass valve interposed in the bypass passage and opening and closing the bypass passage;
Nozzle vane control means for controlling the opening of the variable nozzle vane according to the operating state of the engine;
EGR valve control means for controlling the opening of the EGR valve in accordance with the operating state of the engine;
Bypass valve control means for controlling the opening of the bypass valve according to the operating state of the engine,
Control of the variable nozzle vane by the nozzle vane control means is executed, control of the EGR valve by the EGR valve control means is executed, and the operating state of the engine is such that the pressure of the intake passage downstream from the compressor is With a variable displacement supercharger, further comprising a control device for opening the bypass valve in the bypass valve control means when the pressure in the exhaust passage upstream of the variable nozzle vane is higher. engine. A throttle valve that is provided in an intake passage downstream of the compressor and opens and closes the intake passage;
Throttle valve control means for controlling the opening of the throttle valve according to the operating state of the engine,
2. The variable displacement supercharging according to claim 1, wherein the control device causes the throttle valve control means to close the throttle valve when the bypass valve control means opens the bypass valve. 3. Engine with a machine.   2. The control device according to claim 1, wherein when the operating state of the engine is at least a mid-rotation load, the bypass valve control means causes the bypass valve control means to open the opening of the bypass valve to a small opening. 2. The engine with a variable capacity supercharger as described in 2.   The said nozzle vane control means makes the opening degree of the said variable nozzle vane into the range of a small opening degree to a middle opening degree when the driving | running state of the said engine is a middle rotation middle load. The engine with a variable capacity supercharger as described in any one of the items.   Further, the control device causes the bypass valve control means to open the bypass valve when the operating state of the engine is overloaded, and opens the bypass valve according to an increase in the engine speed. The engine with a variable displacement supercharger according to any one of claims 1 to 4, wherein the degree of opening is a large opening.   The nozzle vane control means and the bypass valve control means control the opening degrees of the variable nozzle vane and the bypass valve based on a map in which the opening degree is associated with the engine speed and the load. The engine with a variable capacity supercharger as described in any one of -5.

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