JP2016130489A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a boost pressure with high accuracy while avoiding choking of a turbocharger in a configuration in which the turbocharger and an electric supercharger are provided.SOLUTION: An engine 10 comprises: a turbocharger 22; an electric supercharger 24, a WGV 46, and the like. An ECU 50 executes a single supercharge mode using only the turbocharger 22 in a first operation range where an engine torque is lower than a torque boundary value. Furthermore, the ECU 50 executes a twin supercharge mode using the turbocharger 22 and the electric supercharger 24 in a second operation range where the engine torque is equal to or higher than the torque boundary value. Moreover, the ECU 50 determines whether choking occurs to the turbocharger 22 in the second operation range, and decreases an opening degree of the WGV 46 when determining that choking occurs.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a control device for an internal combustion engine including a turbocharger and an electric supercharger.

  As a prior art, for example, as described in Patent Document 1, a control device for an internal combustion engine provided with a two-stage turbocharger is known. In the prior art, the high-pressure turbo is composed of a variable nozzle type supercharger. When using the high-pressure stage turbo, the low-pressure stage turbo is operated by opening the vanes of the high-pressure stage turbo as necessary, and choke in the high-pressure stage turbo is avoided.

JP 2008-157236 A JP 2005-201243 A JP 2012-92797 A JP 2005-226505 A

  As a conventional internal combustion engine system capable of two-stage supercharging, for example, a configuration in which a turbocharger and an electric compressor are connected in series can be considered. In such a system, the fuel consumption can be improved by reducing the opening of the waste gate valve (WGV) on the output point side where the maximum output of the internal combustion engine is obtained, and supercharging by the electric compressor. However, when the electric compressor is driven on the high rotation / high load side, the gas flow rate is increased, but the pressure ratio of the turbocharger does not increase, and this may cause the turbocharger operating region to enter the choke region. . In this case, even if the control for opening the vane is executed as in the prior art, the pressure ratio is lowered, so it is difficult to avoid the choke region, and the problem can be solved by the prior art. Can not.

  The present invention has been made to solve the above-described problems. In a configuration in which a turbocharger and an electric supercharger are provided side by side, the supercharging pressure is reduced while avoiding choke of the turbocharger. An object of the present invention is to provide a control device for an internal combustion engine that can be controlled with high accuracy.

A first invention includes a turbocharger having a compressor disposed in an intake passage of an internal combustion engine and a turbine disposed in an exhaust passage, and supercharging intake air using exhaust energy as a power source;
An electric supercharger that supercharges intake air using an electric motor as a power source; and
An exhaust bypass passage for bypassing the turbine and circulating exhaust gas;
A waste gate valve for opening and closing the exhaust bypass passage;
In the first operation region where the torque index value correlated with the torque of the internal combustion engine is less than a preset boundary value, the WGV opening, which is the opening of the waste gate valve, decreases as the torque increases. First control means for controlling the WGV opening;
In the second operation region in which the torque index value is equal to or greater than the boundary value, the WGV opening is constant with respect to the change in the torque, or the WGV opening is increased as the torque is increased. And a second control means for controlling the WGV opening and operating the electric supercharger,
A choke avoiding unit configured to determine whether or not choke is generated in the turbocharger in the second operation region, and to reduce the WGV opening when it is determined that choke is generated;

  According to the second invention, the choke avoiding means is configured to reduce or maintain the output of the electric supercharger when determining that choke is generated and reducing the WGV opening.

A third aspect of the invention relates to an intake pressure detection means for detecting an intake pressure on the upstream side and an intake pressure on the downstream side of the compressor;
A choke limit that is a boundary of a region in which choke is not generated in an operation region defined based on a pressure ratio between the intake pressure on the upstream side and the intake pressure on the downstream side and a gas flow rate in the intake passage is previously stored. Storage means,
The choke avoiding means determines whether or not choke is generated based on the pressure ratio calculated based on the detection result of the intake pressure detecting means, the gas flow rate through the intake passage, and the choke limit data. It is set as the structure which determines.

  According to the fourth invention, the choke avoiding means determines that the choke is generated, and if the exhaust temperature of the internal combustion engine is higher than a preset exhaust temperature upper limit, the WGV opening is set. The output of the electric supercharger is reduced without being reduced.

According to a fifth aspect, the second operating region includes a low torque region where the torque index value is less than a second boundary value greater than the boundary value, and the torque index value is equal to or greater than the second boundary value. With high torque range,
The choke avoiding means determines that choke is generated in the turbocharger when the torque index value belongs to the high torque region, and reduces the WGV opening compared to the low torque region. Yes.

  According to a sixth aspect of the invention, the torque index value is a load torque required for the internal combustion engine, and the boundary value is changed according to the rotational speed of the internal combustion engine.

  According to the first invention, the choke avoiding means can determine whether or not choke is generated in the turbocharger, and if it is determined that choke is generated, the choke avoiding means can reduce the WGV opening. it can. As a result, the pressure ratio increases as the WGV opening decreases, so that choke generation can be avoided. Therefore, a desired supercharging pressure can be realized while avoiding choke of the turbocharger even in the high output operation region.

1 is a configuration diagram schematically showing a system configuration of an internal combustion engine according to a first embodiment of the present invention. In Embodiment 1 of this invention, it is explanatory drawing which shows the relationship between the driving | operation area | region of an engine, and supercharging control. In Embodiment 1 of this invention, it is a characteristic diagram which shows control of the WGV opening degree in each area | region of an engine torque, an electric motor output, and a throttle opening degree. It is explanatory drawing which shows the phenomenon in which the operating point of a turbocharger approaches a choke limit in twin supercharging mode. 5 is a timing chart showing an example of choke avoidance control in Embodiment 1 of the present invention. In Embodiment 1 of this invention, it is explanatory drawing which shows the operating point of the turbocharger which changes according to the presence or absence of choke avoidance control. 5 is a flowchart illustrating an example of choke avoidance control executed by an ECU in the first embodiment of the present invention. In Embodiment 2 of this invention, it is a flowchart which shows an example of chalk avoidance control. In Embodiment 3 of this invention, it is explanatory drawing which shows the driving | operation area | region map for switching a supercharging mode based on an engine speed and load.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
First, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram schematically showing a system configuration of an internal combustion engine according to Embodiment 1 of the present invention. As shown in this figure, the system of the present embodiment includes an engine 10 as an internal combustion engine. The engine 10 is constituted by a spark ignition engine such as a gasoline engine, for example, and is used as a power source of the vehicle. The engine 10 includes an engine main body 12 constituting the main body portion. An intake passage 14 and an exhaust passage 16 are connected to each cylinder of the engine body 12.

  In the intake passage 14, an air cleaner 18, an air flow meter 20, and a compressor 22 a of a turbocharger 22 are provided. The air flow meter 20 detects the amount of air flowing through the intake passage 14 (intake air amount of the engine 10). The turbocharger 22 supercharges intake air using exhaust energy as a power source. The turbocharger 22 is disposed on the downstream side of the air cleaner 18 and the air flow meter 20, and the turbine 22b is disposed in the exhaust passage 16. It has. When the turbocharger 22 operates, the turbine 22b receives exhaust pressure and rotates together with the compressor 22a, thereby driving the compressor 22a and supercharging intake air by the compressor 22a.

  The engine body 12 includes an electric supercharger 24 that supercharges intake air using an electric motor as a power source. The electric supercharger 24 includes a compressor 24a and an electric motor 24b. The compressor 24 a is driven by the electric motor 24 b to supercharge intake air, and is disposed in the intake passage 14 at a position downstream of the air cleaner 18 and upstream of the compressor 22 a of the turbocharger 22. The intake passage 14 is provided with an upstream intake pressure sensor 26 that detects intake pressure at a position downstream of the compressor 24a of the electric supercharger 24 and upstream of the compressor 22a of the turbocharger 22. ing. Further, the intake passage 14 is provided with an intake bypass passage 30 that bypasses the compressor 24 a and an intake bypass valve 32 that opens and closes the intake bypass passage 30. The intake bypass valve 32 is configured by, for example, an electric butterfly valve.

  The intake passage 14 is provided with an intercooler 34 and an electronically controlled throttle valve 36. The intercooler 34 cools the intake air compressed by the compressors 22a and 24a. The throttle valve 36 adjusts the amount of intake air of the engine 10 and is disposed on the downstream side of the intercooler 34. A portion of the intake passage 14 positioned downstream of the throttle valve 36 is configured as an intake manifold 38, and intake air is distributed to each cylinder via the intake manifold 38. The intake manifold 38 is provided with an intake pressure sensor 40 on the downstream side that detects intake pressure (supercharge pressure) on the downstream side of the compressor 22 a of the turbocharger 22. The intake pressure sensors 26 and 40 constitute the intake pressure detection means of the present embodiment.

  Exhaust gas from each cylinder is collected and discharged by an exhaust manifold 42 that constitutes a part of the exhaust passage 16. An exhaust bypass passage 44 that bypasses the turbine 22b of the turbocharger 22 and distributes exhaust gas is connected to the exhaust passage 16. A waste gate valve (WGV) 46 that opens and closes the exhaust bypass passage 44 is disposed in the exhaust bypass passage 44. The WGV 46 is constituted by, for example, an electric valve, and the opening degree of the WGV 46 can be set to any opening degree within a preset opening degree range. In the following description, the opening degree of the WGV 46 may be expressed as “WGV opening degree”. By changing the WGV opening, the amount of exhaust gas passing through the turbine 22b can be adjusted, and the driving force of the compressor 22a can be controlled. A catalyst 48 for purifying exhaust gas is disposed in the exhaust passage 16 on the downstream side of the turbine 22b.

  Further, the system of the present embodiment includes an ECU (Electronic Control Unit) 50 that controls the operating state of the engine 10. The ECU 50 includes an arithmetic processing unit (CPU), a storage circuit, and an input / output interface. The storage circuit stores various control programs and data maps for controlling the engine 10. In addition to the air flow meter 20 and the intake pressure sensors 26 and 40 described above, various sensors including a crank angle sensor 52 and the like are connected to the input side of the ECU 50. The crank angle sensor 52 is a sensor for detecting the crank angle and the rotational speed (engine rotational speed) of the engine 10. On the other hand, on the output side of the ECU 50, in addition to the electric motor 24b, the intake bypass valve 32, the throttle valve 36 and the WGV 46, a fuel injection valve 60 for injecting fuel into each cylinder, and an ignition device for igniting an air-fuel mixture in each cylinder Various actuators including 62 are connected. The ECU 50 executes engine control by driving each actuator based on the detection signal read from each sensor.

[Control by Embodiment 1]
Next, engine torque control executed by the ECU 50 will be described with reference to FIGS. First, FIG. 2 is an explanatory diagram showing the relationship between the engine operating range and the supercharging control in the first embodiment of the present invention.

  As shown in FIG. 2, the operation region on the low load (low engine torque) side is a natural intake region (non-supercharge region) where intake air is not supercharged. In this natural intake region, the intake air amount (in other words, engine torque) is controlled by adjusting the opening of the throttle valve 36 with the WGV opening set to the maximum opening. On the other hand, the intake air is supercharged in a region other than the natural intake region. At this time, the ECU 50 selects either a single supercharging mode or a twin supercharging mode described below according to the operation region.

(Single supercharging mode)
A single supercharging region for executing the single supercharging mode is set on the higher load side (high engine torque side) than the natural intake region. The single supercharging mode is a supercharging mode in which only the turbocharger 22 is operated to supercharge intake air. In the single supercharging mode, the electric supercharger 24 is stopped and the intake bypass valve 32 is kept fully open. Thus, in the single supercharging mode, the intake air supercharged by the turbocharger 22 is supplied to the combustion chambers of the respective cylinders while avoiding the compressor 24a of the electric supercharger 24 from becoming an intake resistance. In the single supercharging region, the supercharging pressure (in other words, engine torque) is controlled by controlling the WGV opening.

  In the single supercharging mode, when supercharging is performed in the high rotation / high load region with the WGV 46 closed, the supercharging pressure and the exhaust pressure increase upstream of the turbine 22b. In this state, the temperature of the exhaust gas (exhaust temperature) increases, and the pump loss increases. In the torque region near the torque limit in the single supercharging mode, the fuel efficiency is deteriorated due to an increase in pump loss. Note that the torque limit in the single supercharging mode is set in advance in accordance with, for example, parameter limits including exhaust temperature, exhaust pressure upstream of the turbine 22b, pump loss, and the like. The torque limit corresponds to a torque boundary value TQ2 described later. In the present embodiment, the case where the engine torque itself is used as the torque index value to be compared with the torque boundary value TQ2 is illustrated. Here, the engine torque means a load torque required for the internal combustion engine.

(Twin supercharge mode)
A twin supercharging region for executing the twin supercharging mode is set on the higher rotation / high load side than the single supercharging region. The twin supercharging mode is a supercharging mode in which both the turbocharger 22 and the electric supercharger 24 are operated to supercharge intake air. In the twin supercharging mode, the electric motor 24b is energized while the intake bypass valve 32 is basically kept fully closed. As a result, the intake air introduced into the intake passage 14 is sequentially supercharged by the electric supercharger 24 and the turbocharger 22 and then supplied to the combustion chamber of each cylinder. Thereby, supercharging by the turbocharger 22 can be assisted using the electric supercharger 24. Hereinafter, supercharging assistance by the electric supercharger 24 may be simply referred to as “electric assist”.

  According to the twin supercharging mode (that is, electric assist), the following effects can be obtained. First, in the single supercharging mode, the pump loss increases near the torque limit as described above, and the fuel consumption tends to deteriorate. On the other hand, in a high rotation / high load region or the like, the electric supercharger 24 shares a part of the supercharging required for the turbocharger 22 by performing the electric assist. For this reason, according to the twin supercharging mode, the burden on the turbocharger 22 can be reduced, and an engine torque equivalent to that in the single supercharging mode can be obtained with the WGV opening being further opened. Therefore, an increase in pump loss due to an increase in exhaust pressure can be suppressed, and improvement in fuel consumption can be promoted by electric assist. Moreover, it can suppress that exhaust temperature raises with a raise of exhaust pressure.

  Next, with reference to FIG. 3, the control in each operation region executed by the ECU 50 will be described. FIG. 3 is a characteristic diagram showing control of the WGV opening, the motor output, and the throttle opening in each region of the engine torque in the first embodiment of the present invention. Here, FIG. 3A shows the relationship between the engine torque and the WGV opening in the steady state. 3B shows the relationship between the engine torque in the steady state and the output of the electric motor 24b, and FIG. 3C shows the relationship between the engine torque and the throttle opening in the steady state. FIG. 3 shows a characteristic line when the engine speed is kept at a high speed (for example, NE1 in FIG. 2) in the twin supercharging mode.

(Control of natural intake area)
In FIG. 3, the torque region where the engine torque is lower than TQ1 corresponds to the natural intake region described above. In the natural intake region, as shown in FIG. 3A, the WGV opening is held at the maximum opening, and the supercharging by the turbocharger 22 is held in a stopped state. Further, as shown in FIG. 3B, the electric supercharger 24 is held in a stopped state. In this state, as shown in FIG. 3C, the throttle opening is controlled such that the higher the engine torque, the larger the throttle opening.

(Single supercharging area control)
A torque region where the engine torque is equal to or greater than TQ1 and less than TQ2 corresponds to a single supercharging region where the single supercharging mode is selected. In the single supercharging region, supercharging is performed using only the turbocharger 22, so that the electric supercharger 24 is held in a stopped state. Further, the throttle opening is kept in a fully opened state. On the other hand, the WGV opening in the single supercharging region is controlled such that the WGV opening decreases as the engine torque increases, as indicated by a characteristic line C1 in FIG. That is, in this region, the WGV opening decreases as the engine torque increases. Thereby, the output of the turbocharger 22 can be increased corresponding to the increase in engine torque.

(Twin supercharging area control)
The torque region where the engine torque is equal to or greater than TQ2 corresponds to the twin supercharging region where the twin supercharging mode is selected. In the twin supercharging region, both the turbocharger 22 and the electric supercharger 24 are driven. More specifically, the motor output is set to P1 when the engine torque is TQ2. P1 is an output necessary for rotating the compressor 24a to such an extent that the intake air amount at which the engine torque TQ2 is obtained does not become the intake resistance. In other words, the compressor 24a can be driven (supercharged) to the outside by being driven at an output higher than P1. The motor output is controlled to increase as the engine torque is higher than TQ2. Further, the throttle opening is kept in a fully opened state.

  On the other hand, the WGV opening in the twin supercharging region is controlled so that the WGV opening increases as the engine torque increases, as indicated by the characteristic line C2 in FIG. Accordingly, in the twin supercharging region, the WGV opening is set to the minimum value WGV1 when the engine torque is TQ2. In the present embodiment, control may be performed so that the WGV opening is maintained at a constant value (for example, WGV1) with respect to changes in engine torque in the region near TQ2 in the twin supercharging region.

  As described above, when supercharging is performed, either the single supercharging mode or the twin supercharging mode is selected based on the magnitude of the engine torque, and the WGV opening degree is determined based on the control characteristics illustrated in FIG. Control the motor output and throttle opening. According to this control characteristic, since the WGV opening is increased as the engine torque is higher in the twin supercharging region, an increase in exhaust pressure caused by an increase in both the engine torque and the motor output can be suppressed. Thereby, the fuel efficiency can be improved by using the electric assist, and the rise of the exhaust temperature can be suppressed.

  Here, the engine torque TQ2 serving as a boundary between the single supercharging region and the twin supercharging region will be described. In the following description, the engine torque TQ2 may be expressed as “torque boundary value TQ2”. For example, as indicated by a broken line in FIG. 2, the torque boundary value TQ2 has a characteristic of decreasing as the engine speed increases. More specifically, in the single supercharging region shown in FIG. 3 (A), when the WGV opening decreases as the engine torque increases, the exhaust temperature increases accordingly. The WGV opening when the exhaust temperature reaches a predetermined upper limit temperature is set as WGV1, and the engine torque that gives this WGV1 is set as the torque boundary value TQ2.

  That is, the torque boundary value TQ2 is set as the maximum engine torque that can suppress the exhaust gas temperature below the upper limit temperature in the single supercharging region. Since the engine torque when the exhaust temperature reaches the upper limit temperature decreases as the engine speed increases, the characteristic of the torque boundary value TQ2 described above can be obtained. If the torque boundary value TQ2 is set in this way, the torque boundary value TQ2 can be appropriately set in consideration of the exhaust gas temperature. Moreover, since single supercharging can be extended to the high engine torque side as long as the exhaust temperature permits, the twin supercharging region can be narrowed by that much, and the power consumption of the electric supercharger 24 can be suppressed. In the present embodiment, the exhaust temperature is exemplified as a parameter for setting the torque boundary value TQ2. However, the present invention is not limited to this, and for example, from the exhaust pressure upstream of the turbine 22b, the pump loss of the engine 10, and the like. The torque boundary value TQ2 may be set in accordance with other parameter restrictions.

(Choke avoidance control)
As described above, in the twin supercharging mode, the electric assist is executed in the operation region on the high rotation / high load side. However, when the electric supercharger 24 is driven on the high rotation / high load side, the gas flow rate increases, but the pressure ratio of the turbocharger does not increase, so the operating point of the turbocharger 22 approaches the choke limit. Will go. FIG. 4 is an explanatory diagram showing a phenomenon in which the operating point of the turbocharger approaches the choke limit in the twin supercharging mode. As shown in this figure, when the electric supercharger 24 is activated, the operating point of the turbocharger 22 moves from, for example, a point P to a point Q. As a result, the operating point approaches the choke limit as compared with a state where the electric supercharger 24 is stopped (broken line), and there is a possibility that choke may occur. In particular, in the twin supercharging mode, the supercharging state is changed by the operation of the electric supercharger 24, and the choke is more likely to occur than in the single supercharging mode.

  In order to solve this problem, in the present embodiment, choke avoidance control is executed in the twin supercharging region. FIG. 5 is a timing chart showing an example of the choke avoidance control in the first embodiment of the present invention. In FIG. 5, at the point A where the engine torque reaches the torque boundary value TQ2, the supercharging control of the engine 10 is switched from the single supercharging mode to the twin supercharging mode, and further at the point B where the engine torque becomes higher. The case where the choke avoidance control is started is illustrated.

  In the choke avoidance control, first, it is determined whether or not choke is generated in the turbocharger by a determination process described later. If it is determined that choke is generated, the WGV 46 is driven to the closed side as shown by the characteristic line La in FIG. 5 to reduce the WGV opening. Further, in the choke avoidance control, as indicated by a characteristic line Lc in FIG. 5, when it is determined that choke is generated and the WGV opening is decreased, the output of the electric supercharger 24 (that is, the rotational speed of the electric motor 24b). ) May be reduced.

  According to the choke avoidance control, it is possible to obtain the effects as shown in FIG. FIG. 6 is an explanatory diagram showing the operating point of the turbocharger that changes according to the presence or absence of the choke avoidance control in the first embodiment of the present invention. In this figure, the vertical axis indicates the pressure ratio between the upstream intake pressure and the downstream intake pressure of the compressor 22a of the turbocharger 22, and the horizontal axis indicates the gas flow rate passing through the compressor 22a. .

  Moreover, the thick line in FIG. 6 shows the choke limit of the compressor 22a. The choke limit represents a boundary (outside) of a region where choke is not generated in the compressor 22a in the operation region defined based on the pressure ratio and the gas flow rate. That is, in FIG. 6, when the operating point of the compressor 22a protrudes outside the choke limit, choke is generated, so that the operable range of the turbocharger 22 is limited to the inside of the choke limit. Data relating to the choke limit is stored in advance in the ECU 50 as a data map or the like using, for example, the gas flow rate and the pressure ratio as arguments. ECU50 comprises the memory | storage means of this Embodiment.

  First, it is assumed that the operating point of the compressor 22a is located, for example, on the characteristic line L1 in FIG. 6 in a state where the single supercharging mode is executed. From this state, as the engine torque increases, the pressure ratio and the gas flow rate gradually increase. Therefore, the operating point of the compressor 22a moves toward the point A on the characteristic line L1. When the operating point reaches point A and the engine torque becomes equal to or greater than the torque boundary value TQ2, the supercharging control is switched from the single supercharging mode to the twin supercharging mode, and the electric supercharger 24 operates. As a result, the operating point of the compressor 22a moves toward the point B on the characteristic line L2, for example.

  In this state, when the choke avoidance control is not executed, the operating point of the compressor 22a passes B and moves outside the choke limit, and choke is generated in the compressor 22a. On the other hand, according to the choke avoidance control, it is determined that choke is generated when the operating point reaches point B or the vicinity thereof, and the WGV opening can be reduced. As a result, the pressure ratio increases as the WGV opening decreases, so that the operating point of the compressor 22a moves, for example, from the point B on the characteristic line L3, and the operating point moves outside the choke limit. Can be avoided.

  Moreover, in the choke avoidance control, for example, the operating point of the compressor 22a moves along the inner edge of the choke limit along the characteristic line L3 by appropriately adjusting the WGV opening based on the previously stored characteristic data map of FIG. The position of the operating point can be controlled to move up. As a result, a desired supercharging pressure can be achieved while avoiding choking of the turbocharger 22 even in the high-power operation region.

  In the choke avoidance control, the WGV opening is decreased in order to avoid choke, so that the supercharging pressure tends to increase. For this reason, when decreasing the WGV opening, it is preferable to reduce the output of the electric supercharger 24. Thereby, the increase in the supercharging pressure resulting from the decrease in the WGV opening degree can be compensated by the decrease in the output of the electric supercharger 24. Therefore, the supercharging pressure can be brought close to the target value with high accuracy by the synergistic effect of the output control of the electric supercharger 24 and the WGV control.

  In the above description, as shown by the characteristic line L2 in FIG. 6, the case where the gas flow rate is changed in a state where the pressure ratio is constant in the twin supercharging mode is exemplified. However, the present invention is not limited to this, and in the twin supercharging mode, control may be performed so that the pressure ratio and the gas flow rate change toward an operating point where fuel consumption improves. More specifically, the control characteristic of the twin supercharging mode may be set so that, for example, the characteristic line L2 is inclined in the vertical direction with respect to the horizontal axis of FIG.

(Specific processing in Embodiment 1)
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 7 is a flowchart showing an example of the choke avoidance control executed by the ECU in the first embodiment of the present invention. Note that the routine shown in this figure is repeatedly executed during steady operation (including quasi-steady operation).

  In the routine shown in FIG. 7, first, in step S100, the intake air amount is acquired based on the detection result of the air flow meter 20. In step S100, the intake pressure on the upstream side of the compressor 22a of the turbocharger 22 is acquired based on the detection result of the intake pressure sensor 26, and the downstream of the compressor 22a is acquired based on the detection result of the intake pressure sensor 40. Get the side intake pressure. Next, in step S101, the pressure ratio between the upstream intake pressure and the downstream intake pressure is calculated, and based on this pressure ratio and the intake air amount (that is, the gas flow rate in the intake passage 14), FIG. 6 to calculate the current operating point of the compressor 22a in the operation region 6. Through the processing in steps S101 and S102, the current operating point is acquired in real time.

  Next, in step S102, by referring to the choke limit data map described above based on the calculation result of the current operating point, whether or not the current operating point exceeds the choke limit (or the current operation point). Whether or not the point has reached the choke limit). To give a more specific processing example, in step S102, it is determined whether or not the current operating point is outside the choke limit on the data map. If the determination in step S102 is established, the operating point of the compressor 22a has reached the choke limit, so it is determined that choke is generated in the turbocharger 22, and the process proceeds to step S103 to avoid the choke.

  If the determination in step S102 is not established, it is determined that choke does not occur because the current operating point is inside the choke limit (that is, the operable range of the turbocharger 22). Exit. In step S102, it is determined that the current operating point has reached the choke limit when the distance between the current operating point and the choke limit on the operating region is equal to or less than a preset limit determination value. May be. According to the determination processing in step S102, it is possible to accurately determine whether or not choke is generated in the compressor 22a based on the current operating point and choke limit data.

  Next, in step S103, the WGV opening is decreased by driving the WGV 46 to the closed side. In step S104, it is determined whether or not the supercharging pressure is higher than the target supercharging pressure. The target boost pressure is set based on the operating state of the engine 10 by the boost pressure control of the ECU 50. If the determination in step S104 is established, it is determined that the supercharging pressure has increased due to a decrease in the WGV opening or the like, and the process proceeds to step S105. In step S105, the output of the electric supercharger 24 is reduced by reducing the rotational speed of the electric motor 24b. On the other hand, if the determination in step S104 is not established, step S105 is not executed and this routine is terminated.

  As described above in detail, according to the present embodiment, when the operating point of the compressor 22a reaches the choke limit, the WGV opening can be reduced and the output of the electric supercharger 24 can be reduced. Thereby, as described above, it is possible to suppress the operating point of the compressor 22a from protruding outside the choke limit, and to achieve a desired supercharging pressure while avoiding choke.

  In the first embodiment, the single supercharging region corresponds to the first operating region, and the twin supercharging region corresponds to the second operating region. A characteristic line C1 of the WGV opening shown in FIG. 3A shows a specific example of the first control means. Further, the characteristic line C2 of the WGV opening shown in FIG. 3A and FIG. 3B show a specific example of the second control means. The routine shown in FIG. 7 shows a specific example of the choke avoiding means.

  In Embodiment 1, the WGV opening is decreased and the output of the electric supercharger 24 is decreased by the choke avoidance control. However, the choke avoidance control according to the present invention may be configured to decrease the WGV opening without decreasing the output of the electric supercharger 24.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. The present embodiment is characterized in that, in addition to the configuration of the first embodiment, an exhaust temperature sensor (not shown) for detecting the exhaust temperature is provided, and the exhaust temperature is taken into account when executing the choke avoidance control. More specifically, in the system of the first embodiment, when the electric supercharger 24 is operated with the WGV opening being small, the exhaust temperature is likely to rise excessively.

  For this reason, in the present embodiment, even when it is determined that choke is generated in the choke avoidance control, if the exhaust gas temperature is higher than the preset exhaust gas temperature upper limit value, the WGV opening degree is not decreased. The output of the electric supercharger 24 is reduced. Here, the exhaust gas upper limit value is set based on, for example, the upper limit value of the catalyst temperature, and is stored in the ECU 50 in advance.

(Specific processing in Embodiment 2)
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 8 is a flowchart showing an example of the choke avoidance control in the second embodiment of the present invention. The routine shown in this figure is repeatedly executed during steady operation. In the routine shown in FIG. 8, first, in steps S200 to S202, processing similar to that in steps S100 to S102 of the first embodiment (FIG. 7) is executed.

  Next, in step S203, it is determined whether or not the exhaust temperature is higher than the exhaust temperature upper limit value. If the determination in step S203 is not established, the exhaust gas temperature is within the allowable limit. Therefore, in steps S204 to S206, processing similar to that in steps S103 to S105 of the first embodiment is executed. That is, in this case, the WGV opening is decreased and the output of the electric supercharger 24 is decreased depending on the supercharging pressure.

  On the other hand, if the determination in step S203 is established, the exhaust gas temperature exceeds the allowable limit. Therefore, the process proceeds to step S206 without reducing the WGV opening in step S204, and the output of the electric supercharger 24 is output. Reduce.

  According to the present embodiment configured as described above, when the exhaust gas temperature is higher than the exhaust gas upper limit value, the output of the electric supercharger 24 can be reduced without reducing the WGV opening degree, Priority can be given to suppression of exhaust temperature. Thereby, it is possible to avoid control in which the exhaust temperature further increases beyond the allowable limit, and in addition to the same effects as in the first embodiment, it is possible to maintain the exhaust temperature at an appropriate temperature.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG. The present embodiment is characterized in that the supercharging mode is switched based on the engine speed and the load. FIG. 9 is an explanatory diagram showing an operation region map for switching the supercharging mode based on the engine rotation speed and the load in the third embodiment of the present invention. The operation region map shown in this figure is stored in advance in the ECU 50.

  As shown in FIG. 9, the operating region map of the present embodiment includes a first operating region and a second operating region as in the first embodiment, but the second operating region has a low torque. It is divided into a region and a high torque region. Here, the first operation region is set as a region where the engine torque is less than the torque boundary value TQ2. The second operation region is set as a region where the engine torque is equal to or greater than the torque boundary value TQ2. Further, the low torque region is set as a region in the second operation region where the engine torque is less than the second torque boundary value TQ3. The high torque region is set as a region in the second operation region where the engine torque is equal to or greater than the second torque boundary value TQ3.

  The second torque boundary value TQ3 is set to a value larger than the torque boundary value TQ2, and corresponds to the second boundary value in the present embodiment. The second torque boundary value TQ3 is set based on, for example, the minimum value of engine torque at which choke is generated in the turbocharger 22. Further, as shown in FIG. 9, the torque boundary value TQ2 and the second torque boundary value TQ3 are set so as to change according to the engine rotation speed. For example, as the engine rotation speed increases, the torque boundary value TQ2 and the second torque boundary value TQ3 decrease. Is set to Accordingly, the low torque region is set as a region on the higher rotation / high load side than the first operation region, and the high torque region is set as a region on the higher rotation / high load side than the low torque region.

  The ECU 50 executes the following control based on the above-described area division. First, when the current values of the engine speed and the load belong to the first operation region, the above-described single supercharging mode is executed. That is, in this case, with the electric supercharger 24 stopped, the WGV opening is controlled so that the WGV opening decreases as the torque increases. Further, when the current values of the engine speed and the load belong to the low torque region, the above-described twin supercharging mode is executed. That is, in this case, the WGV opening is controlled so that the WGV opening becomes constant with respect to the change of the torque, or the WGV opening increases as the torque increases. 24 is activated.

  Further, when the current values of the engine speed and the load belong to the high torque region, the aforementioned choke avoidance control is executed. However, in this case, when the engine torque enters the high torque region from the low torque region, it is determined that choke is generated in the turbocharger 22, and the WGV opening is decreased compared to the low torque region. At this time, when the supercharging pressure is higher than the target supercharging pressure, the output of the electric supercharger 24 may be reduced as in the first embodiment.

  In the present embodiment configured as described above, substantially the same effects as those of the first embodiment can be obtained. That is, it is possible to achieve a desired supercharging pressure while avoiding choking of the turbocharger 22 even in the high output operation region.

(Reference example)
On the other hand, in the present invention, the operation region map may be defined by using the supercharging pressure measured in real time and the intake air amount (gas flow rate) as control parameters. In this case, the operation region map is divided into a first operation region, a second operation region, and a third operation region based on the supercharging pressure and the intake air amount. When the current values of the supercharging pressure and the intake air amount belong to the first operating region, the single supercharging mode is executed, and when the current values of the supercharging pressure and the intake air amount belong to the second operating region. Performs the twin supercharging mode. Further, when the current values of the supercharging pressure and the intake air amount belong to the third operation region, the choke avoidance control is executed.

  In this reference example, the efficiency of the compressor 22a is calculated based on the supercharging pressure and the intake air amount, and the WGV opening and the electric supercharger 24 are set so that the efficiency of the compressor 22a is equal to or higher than a preset lower limit target value. Are preferably controlled. The reference example configured as described above can obtain substantially the same effect as that of the first embodiment.

  In the first and second embodiments, the case where the engine torque itself is used as the torque index value of the internal combustion engine is exemplified. However, the present invention is not limited to this, and various control parameters (for example, intake pressure, load, intake air amount, etc.) having a correlation with the engine torque may be used as the torque index value.

  In the first to third embodiments, the system in which the compressor 22a of the turbocharger 22 is arranged in series on the downstream side of the compressor 24a of the electric supercharger 24 is exemplified. However, the present invention is not limited to this, for example, a system in which two compressors 22 a and 24 a are arranged in parallel in the intake passage 14, and a compressor of the electric supercharger 24 on the downstream side of the compressor 22 a of the turbocharger 22. The present invention can also be applied to a system in which 24a is arranged. As the electric supercharger 24, an electrically assisted turbocharger may be used.

  Moreover, although Embodiment 1 thru | or 3 illustrated each individual control, this invention is not restricted to this, The structure which combined the control which can be combined among the control demonstrated in each embodiment is also included. . In each embodiment, the engine 10 which is a spark ignition type gasoline engine has been described as an example. However, the present invention is not limited to this, and may be applied to a compression ignition type engine such as a diesel engine.

10 Engine (Internal combustion engine)
12 Engine Body 14 Intake Passage 16 Exhaust Passage 18 Air Cleaner 20 Air Flow Meter 22 Turbocharger 22a Compressor 22b Turbine 24 Electric Supercharger 24a Compressor 24b Electric Motors 26, 40 Intake Pressure Sensor (Intake Pressure Detection Means)
30 Intake Bypass Path 32 Intake Bypass Valve 34 Intercooler 36 Throttle Valve 38 Intake Manifold 42 Exhaust Manifold 44 Exhaust Bypass Path 46 Waste Gate Valve 48 Catalyst 50 ECU (Storage Unit)
52 Crank angle sensor 60 Fuel injection valve 62 Ignition device TQ2 Torque boundary value (boundary value)
TQ3 Second torque boundary value (second boundary value)

Claims (6)

A turbocharger having a compressor disposed in an intake passage of an internal combustion engine and a turbine disposed in an exhaust passage, and supercharging intake air using exhaust energy as a power source;
An electric supercharger that supercharges intake air using an electric motor as a power source; and
An exhaust bypass passage for bypassing the turbine and circulating exhaust gas;
A waste gate valve for opening and closing the exhaust bypass passage;
In the first operation region where the torque index value correlated with the torque of the internal combustion engine is less than a preset boundary value, the WGV opening, which is the opening of the waste gate valve, decreases as the torque increases. First control means for controlling the WGV opening;
In the second operation region in which the torque index value is equal to or greater than the boundary value, the WGV opening is constant with respect to the change in the torque, or the WGV opening is increased as the torque is increased. And a second control means for controlling the WGV opening and operating the electric supercharger,
In the second operation region, it is determined whether or not choke is generated in the turbocharger, and when it is determined that choke is generated, choke avoiding means for decreasing the WGV opening degree;
A control device for an internal combustion engine, comprising:   2. The control device for an internal combustion engine according to claim 1, wherein the choke avoiding unit is configured to reduce or maintain an output of the electric supercharger when it is determined that choke is generated and the WGV opening is decreased. 3. Intake pressure detecting means for detecting the intake pressure on the upstream side and the intake pressure on the downstream side of the compressor, and
A choke limit that is a boundary of a region in which choke is not generated in an operation region defined based on a pressure ratio between the intake pressure on the upstream side and the intake pressure on the downstream side and a gas flow rate in the intake passage is previously stored. Storage means,
The choke avoiding means determines whether or not choke is generated based on the pressure ratio calculated based on the detection result of the intake pressure detecting means, the gas flow rate through the intake passage, and the choke limit data. The control device for an internal combustion engine according to claim 1 or 2, wherein the control device is configured to determine whether or not.   When the choke avoiding means determines that choke is generated and the exhaust gas temperature of the internal combustion engine is higher than a preset exhaust gas temperature upper limit value, the electric motor is operated without decreasing the WGV opening degree. The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the output of the supercharger is reduced. The second operation region is composed of a low torque region in which the torque index value is less than a second boundary value greater than the boundary value, and a high torque region in which the torque index value is greater than or equal to the second boundary value. ,
The choke avoiding means determines that choke is generated in the turbocharger when the torque index value belongs to the high torque region, and reduces the WGV opening compared to the low torque region. The control apparatus for an internal combustion engine according to any one of claims 1 to 4. The torque index value is a load torque required for the internal combustion engine,
The control apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the boundary value is configured to change according to a rotation speed of the internal combustion engine.

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