JP2012172607A - Control device of internal combustion engine with supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit deterioration in atomization of fuel due to an opening change of a waste gate valve, when a control device of an internal combustion engine with a supercharger includes the waste gate valve that opens and closes an exhaust bypass passage bypassing a turbine of a turbo supercharger.SOLUTION: The internal combustion engine with the supercharger includes: a fuel injection valve 28 injecting fuel to an intake port 12b; the turbo supercharger 20 having the turbine 20b operated by exhaust energy in an exhaust passage 14; the exhaust bypass passage 42 bypassing the turbine 20b; and the WGV 44 opening and closing the exhaust bypass passage 42. When a valve overlap period is provided, in the case where an opening of the WGV 44 is large, port injection fuel pressure is adjusted such that pressure difference between the port injection fuel pressure and intake manifold pressure becomes larger compared with the case where an opening of the WGV 44 is smaller.

Description

  The present invention relates to a control device for an internal combustion engine with a supercharger, and in particular, a control device for an internal combustion engine with a supercharger that is suitable for adjusting the fuel pressure supplied to a fuel injection valve that injects fuel into an intake port. About.

  Conventionally, for example, Patent Document 1 discloses a control device for an internal combustion engine that includes a port injection valve that injects fuel into an intake port and an in-cylinder injection valve that injects fuel into the cylinder. In this conventional control device, in order to avoid an excessive increase in the amount of fuel adhering to an intake passage component such as an intake port, a port injection ratio (port) is determined based on the differential pressure between the intake port pressure and the in-cylinder pressure. The ratio of the port injection amount to the sum of the injection amount and the in-cylinder injection amount) is changed.

JP 2008-51067 A

  The atomization state of the fuel injected into the intake port is the difference between the pressure of the fuel supplied to the fuel injection valve and the intake passage pressure (intake manifold pressure) downstream of the throttle valve, which is the injection atmosphere of the fuel injection valve. It depends on the pressure. On the other hand, the atomization state of the injected fuel adhering to the wall surface of the intake port indicates that when the valve overlap period is provided, the amount of intake air blown back from the cylinder to the intake port during the valve overlap period It also changes depending on. In this case, the blowback amount itself is determined by the differential pressure between the in-cylinder pressure and the intake passage pressure (intake manifold pressure). Here, the cylinder pressure during the valve overlap period is substantially determined by the exhaust pressure. Therefore, during the valve overlap period, the amount of return of the intake air changes according to the level of the exhaust pressure, and as a result, the atomization state of the fuel changes.

  When an internal combustion engine including a turbocharger is provided with a waste gate valve that opens and closes an exhaust bypass passage that bypasses the turbine, the exhaust pressure changes according to the opening of the waste gate valve. Therefore, when the valve overlap period is provided, the fuel atomization state may deteriorate depending on the opening of the waste gate valve.

  The present invention has been made to solve the above-described problems. When a configuration including a waste gate valve that opens and closes an exhaust bypass passage that bypasses the turbine of the turbocharger is used, the waste gate valve is opened. It is an object of the present invention to provide a control device for an internal combustion engine with a supercharger capable of suppressing deterioration of the atomization state of fuel accompanying a change in degree.

1st invention is a control apparatus of the internal combustion engine with a supercharger,
A fuel injection valve for injecting fuel into the intake port;
A turbocharger having a turbine operating by exhaust energy in the exhaust passage;
An exhaust bypass passage that branches off from the exhaust passage at a portion upstream of the turbine and merges with the exhaust passage at a portion downstream of the turbine;
A waste gate valve for opening and closing the exhaust bypass passage;
Fuel pressure adjusting means for adjusting the fuel pressure supplied to the fuel injection valve;
With
In the case where a valve overlap period in which the valve opening period of the intake valve overlaps the valve opening period of the exhaust valve is provided, the fuel pressure adjusting means is configured to cancel the waste gate valve when the opening degree of the waste gate valve is large. The fuel pressure is adjusted so that the differential pressure between the fuel pressure and the intake passage pressure in the atmosphere of the fuel injection valve is larger than when the opening of the gate valve is small.

  Since the exhaust pressure (on the upstream side of the turbine) changes according to the opening of the waste gate valve, the amount of blowback during the valve overlap period changes, and the atomization state of the fuel changes. According to the first invention, in the case where the valve overlap period is provided, the fuel pressure and the fuel injection valve are larger when the waste gate valve opening is larger than when the waste gate valve opening is small. The fuel pressure is adjusted so that the differential pressure from the intake passage pressure in the atmosphere increases. Thereby, the deterioration of the atomization state of the fuel accompanying the change of the exhaust pressure according to the change of the opening degree of the waste gate valve can be suppressed.

It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 1 of this invention. It is a figure showing the relationship between the particle size of a fuel and port injection fuel pressure under the same intake manifold pressure. It is a figure for demonstrating the influence of the return of intake air during the valve overlap period to the atomization state of fuel. FIG. 4 is a diagram for explaining the control of the port injection fuel pressure in the first embodiment of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration of an internal combustion engine 10 according to Embodiment 1 of the present invention. The system of this embodiment includes a spark ignition type internal combustion engine (gasoline engine) 10. An intake passage 12 and an exhaust passage 14 communicate with each other in the cylinder of the internal combustion engine 10.

  An air cleaner 16 is attached in the vicinity of the inlet of the intake passage 12. An air flow meter 18 that outputs a signal corresponding to the flow rate of air taken into the intake passage 12 is provided in the vicinity of the downstream side of the air cleaner 16. A compressor 20 a of the turbocharger 20 is installed downstream of the air flow meter 18. The compressor 20a is integrally connected to a turbine 20b disposed in the exhaust passage 14 via a connecting shaft.

  An intercooler 22 that cools the compressed air is provided downstream of the compressor 20a. An electronically controlled throttle valve 24 is provided downstream of the intercooler 22. An intake pressure sensor 26 for detecting intake pressure (supercharging pressure) is disposed downstream of the throttle valve 24 (intake manifold 12a).

  Each cylinder of the internal combustion engine 10 is provided with a fuel injection valve 28 for injecting fuel into the intake port 12b (see FIG. 2) and a spark plug 30 for igniting the air-fuel mixture. Each fuel injection valve 28 is connected to a common fuel supply pipe 32. The fuel supply pipe 32 communicates with the fuel tank 36 via the fuel pump 34. A variable pressure regulator 38 is attached to the fuel supply pipe 32. The variable pressure regulator 38 includes a fuel pressure (hereinafter referred to as “port injection fuel pressure”) supplied to the fuel injection valve 28, and an intake pressure (intake manifold) downstream of the throttle valve 24, which is an injection atmosphere of the fuel injection valve 28. The port injection fuel pressure is continuously adjusted so that the differential pressure (hereinafter simply referred to as “injection differential pressure”) may be constant. The variable pressure regulator 38 is connected to a return pipe 40 for returning surplus fuel during pressure regulation to the fuel tank 36. Here, it is assumed that the variable pressure regulator 38 is configured to be able to continuously adjust the port injection fuel pressure, for example, by being electromagnetically driven based on a command from the ECU 56 described later. However, the variable pressure regulator is not limited to the one that can continuously adjust the port injection fuel pressure as described above. For example, the variable pressure regulator may be capable of adjusting the port injection fuel pressure stepwise (for example, in two steps). Good.

  Further, the exhaust passage 14 branches from the exhaust passage 14 at a portion upstream of the turbine 20b, and merges with the exhaust passage 14 at a portion downstream of the turbine 20b (that is, bypasses the turbine 20b). The exhaust bypass passage 42 constructed in (i) is connected. A waste gate valve (WGV) 44 that opens and closes the exhaust bypass passage 42 is provided in the middle of the exhaust bypass passage 42. Here, it is assumed that the WGV 44 is configured to be adjustable to an arbitrary opening degree by an electric or pressure regulating actuator (not shown). If the opening degree of the WGV 44 is adjusted, the amount of exhaust energy flowing into the turbine 20b changes. As a result, since the rotation speed (turbo rotation speed) of the turbine 20b changes, the supercharging pressure can be adjusted. Further, a catalyst 46 for purifying exhaust gas is disposed in the exhaust passage 14 further downstream than the connection portion with the exhaust bypass passage 42 on the downstream side of the turbine 20b.

  The internal combustion engine 10 also includes an intake variable valve mechanism 52 and an exhaust variable valve mechanism 54 for opening and closing the intake valve 48 (see FIG. 2) and the exhaust valve 50 (see FIG. 2). Here, it is assumed that these variable valve mechanisms 52 and 54 are variable valve timing (VVT (Variable Valve Timing) mechanisms that can change the opening / closing timing of the intake valve 48 or the exhaust valve 50. According to the valve mechanisms 52 and 54, the valve overlap period in which the valve opening period of the intake valve 48 and the valve opening period of the exhaust valve 50 overlap can be adjusted to an arbitrary value.

  Further, the system shown in FIG. 1 includes an ECU (Electronic Control Unit) 56. In addition to the air flow meter 18 and the intake pressure sensor 26 described above, various sensors for detecting the operating state of the internal combustion engine 10 such as a crank angle sensor 58 for detecting the engine speed NE are connected to the input portion of the ECU 56. Has been. Further, in the output portion of the ECU 56, the operating state of the internal combustion engine 10 such as the throttle valve 24, the fuel injection valve 28, the spark plug 30, the fuel pump 34, the variable pressure regulator 38, the WGV 44, and the variable valve mechanisms 52 and 54 described above. Various actuators for controlling are connected. The ECU 56 controls the operating state of the internal combustion engine 10 by operating various actuators according to a predetermined program based on the outputs of the various sensors described above.

[Change in atomization state of fuel adhering to the port due to intake air blowback during valve overlap]
FIG. 2 is a graph showing the relationship between the fuel particle size and the port injection fuel pressure under the same intake manifold pressure. FIG. 3 is a diagram for explaining the influence of the return of intake air during the valve overlap period to the atomized state of fuel.
The atomization state of the fuel injected into the intake port 12b is the difference between the fuel pressure supplied to the fuel injection valve 28 (port injection fuel pressure) and the intake manifold pressure that is the injection atmosphere of the fuel injection valve 28 (injection difference). Pressure). For this reason, under the same intake manifold pressure, as the port injection fuel pressure increases, the injection differential pressure increases. Therefore, as shown in FIG. 2, the particle size of the fuel becomes smaller (that is, the fuel becomes more atomized). ).

  On the other hand, when the valve overlap period is provided, the atomized state of the injected fuel adhering to the wall surface of the intake port 12b indicates that the intake air from the cylinder to the intake port 12b during the valve overlap period. It also changes depending on the amount of blow back. That is, as shown in FIG. 3, the fuel adhering to the wall surface of the intake port 12b is torn off and atomized by the blow-back of the intake air.

  The intake blowback amount itself in the above case is determined by the differential pressure between the in-cylinder pressure and the intake manifold pressure. Here, the in-cylinder pressure during the valve overlap period is substantially determined by the exhaust pressure (exhaust pressure on the upstream side of the turbine 20b). Therefore, during the valve overlap period, the amount of return of the intake air changes according to the level of the exhaust pressure, and as a result, the atomization state of the fuel changes.

  When the WGV 44 that opens and closes the exhaust bypass passage 42 is provided as in the present embodiment, the exhaust pressure changes according to the opening degree of the WGV 44. Therefore, when the valve overlap period is provided, the fuel atomization state changes depending on the opening degree of the WGV 44. More specifically, even when the amount of gas in the cylinder is the same, when the WGV 44 is controlled to the opening degree on the closing side, the exhaust pressure increases, so that the amount of intake air blown back increases. Fuel atomization is improved. On the contrary, when the WGV 44 is controlled to the opening degree on the opening side, the exhaust pressure becomes low, so that the amount of blow-back of the intake air decreases and the atomization of the fuel worsens.

[Control of Port Injection Fuel Pressure in Embodiment 1]
In the ECU 56, the opening degree of the WGV 44 for the purpose of optimizing the fuel consumption of the internal combustion engine 10 is set in advance in relation to the operating range of the internal combustion engine 10 (for example, defined by the load and the engine speed). Hereinafter, the opening degree of the WGV 44 set in advance in the ECU 56 in relation to the operation region is referred to as a “base WGV opening degree”.

FIG. 4 is a diagram for explaining the control of the port injection fuel pressure in the first embodiment of the present invention.
The above-described base WGV opening is expressed as a relationship with the intake manifold pressure (≈load) as shown in FIG. That is, here, as indicated by a thick line in FIG. 4, the base WGV opening is set to decrease as the intake manifold pressure increases.

  If the port injection fuel pressure is constant, the injection differential pressure decreases as the intake manifold pressure increases. For this reason, as the intake manifold pressure increases, the atomization state of the fuel becomes worse. Further, as described above, when the opening degree of the WGV 44 is large (WGV 44 is on the open side), the fuel atomization state is worse than when the opening degree of the WGV 44 is small (the WGV 44 is on the closing side). Therefore, as shown in FIG. 4, when the intake manifold pressure decreases and the opening of the WGV 44 decreases, the atomization state of the fuel improves, while the intake manifold pressure increases and the opening of the WGV 44 increases. When becomes larger, the atomization state of the fuel becomes worse.

  Therefore, in this embodiment, the port injection fuel pressure is changed according to the base WGV opening in order to suppress the deterioration of the atomization state of the fuel accompanying the change in the WGV opening described above. Specifically, when the WGV opening is large, the port injection fuel pressure is adjusted so that the differential pressure (injection differential pressure) between the port injection fuel pressure and the intake manifold pressure is larger than when the WGV opening is small. I did it.

  Further, the opening degree of the WGV 44 used during the operation of the internal combustion engine 10 may not be the base WGV opening degree. The cases where the base WGV opening is not used include, for example, when the catalyst 46 is required to be warmed up, when a failure occurs in an actuator provided in the internal combustion engine 10, and when detecting an imbalance between cylinders with an air-fuel ratio. is there. If the base WGV opening is used, as shown in FIG. 4, an unambiguous relationship is set between the opening of the WGV 44 and the intake manifold pressure, whereas the base WGV opening is If is not used, no such relationship exists. Therefore, in this embodiment, when the base WGV opening is not used as described above, the following control is performed in order to appropriately control the injection differential pressure. That is, based on the intake manifold pressure in addition to the opening of the WGV 44 that deviates from the base WGV opening, the difference between the port injection fuel pressure and the intake manifold pressure is larger when the WGV opening is larger than when it is small. The port injection fuel pressure was adjusted to increase the pressure.

  Next, referring to FIG. 4, the difference in the configuration of the system for changing the port injection fuel pressure (whether it is continuously variable or variable stepwise (for example, two steps)) A specific method for determining the port injection fuel pressure will be described.

  First, a method for determining the port injection fuel pressure in a system in which the port injection fuel pressure can be continuously varied as in the case where the variable pressure regulator 38 of the present embodiment is provided will be described.

  As shown in FIG. 4, the port injection fuel pressure is set so as to increase as the intake manifold pressure increases and the WGV opening increases in relation to the intake manifold pressure and the WGV opening. In the case of the base WGV opening, as shown in FIG. 4, the relationship with the intake manifold pressure is set in advance. Therefore, when the opening degree of the WGV 44 is controlled according to the current base WGV opening degree, the opening degree of the WGV 44 is obtained by calculating the port injection fuel pressure based on the base WGV opening degree according to the relationship shown in FIG. Accordingly, the port injection fuel pressure is calculated. That is, according to the setting shown in FIG. 4 described above, by increasing the port injection fuel pressure as the intake manifold pressure increases, a stable injection difference can be achieved regardless of changes in the intake manifold pressure during operation of the internal combustion engine 10. The pressure can be secured. In addition, since the port injection fuel pressure is set to increase as the opening of the WGV 44 increases, the port injection fuel pressure can be adjusted so that the injection differential pressure increases as the WGV opening increases.

  When the opening degree of the WGV 44 is controlled to deviate from the base WGV opening degree, the port injection fuel pressure is calculated based on the current WGV opening degree and the intake manifold pressure according to the relationship shown in FIG. Thus, even when the opening degree of the WGV 44 is controlled to deviate from the base WGV opening degree, it is possible to ensure a stable injection differential pressure regardless of the change in the intake manifold pressure during the operation of the internal combustion engine 10. The port injection fuel pressure can be adjusted so that the injection differential pressure increases as the WGV opening increases.

  Next, unlike the case where the variable pressure regulator 38 of the present embodiment is provided, a method for determining the port injection fuel pressure in a system in which the port injection fuel pressure can be varied in two stages will be supplementarily described.

  As shown in FIG. 4, the port injection fuel pressure in this case is a relationship between the intake manifold pressure and the WGV opening, and the low fuel pressure value on the side where the intake manifold pressure is low and the WGV opening is small, and the intake manifold pressure is high. In addition, a high fuel pressure value (> low fuel pressure value) on the side where the WGV opening is large is set in two stages. When the opening degree of the WGV 44 is controlled according to the current base WGV opening degree, as shown in FIG. 4, the current opening degree of the WGV 44 is the boundary line between the low fuel pressure value and the high fuel pressure value, and the base WGV opening degree. When the value is equal to or less than the value at the time when the degree line intersects, the port injection fuel pressure is determined to be a low fuel pressure value. On the other hand, when the current opening degree of the WGV 44 is larger than the above value, the port injection fuel pressure is high fuel pressure. Determined by value. Thereby, even when the port injection fuel pressure is controlled in two stages, when the intake manifold pressure is high, the port injection fuel pressure is made higher than when the intake manifold pressure is low, so that the internal combustion engine 10 is operating. Stable injection differential pressure can be secured regardless of the change in intake manifold pressure. In addition, when the opening degree of the WGV 44 is large, the port injection fuel pressure is set higher than when it is small. When the WGV opening degree is large, the injection differential pressure is larger than when the opening degree is small. Thus, the port injection fuel pressure can be adjusted.

  Further, when the opening degree of the WGV 44 is controlled to deviate from the base WGV opening degree, the port injection fuel pressure is set to a low fuel pressure value and a high value based on the current WGV opening degree and the intake manifold pressure according to the relationship shown in FIG. The fuel pressure value is selected. Thus, even when the opening degree of the WGV 44 is controlled to deviate from the base WGV opening degree, it is possible to ensure a stable injection differential pressure regardless of the change in the intake manifold pressure during the operation of the internal combustion engine 10. The port injection fuel pressure can be adjusted so that the injection differential pressure increases as the WGV opening increases.

  FIG. 5 is a flowchart showing a port injection fuel pressure determination routine executed by the ECU 56. This routine is repeatedly executed every predetermined control cycle. Further, at the start of this routine, a valve overlap period is provided by control of the variable valve mechanisms 52 and 54 or by valve timings of the intake and exhaust valves 48 and 50 set in advance in the internal combustion engine 10. To do.

  In the routine shown in FIG. 5, first, it is determined whether or not the current opening degree of the WGV 44 is controlled according to the base WGV opening degree (step 100). Specifically, it is determined whether or not the base WGV opening is not used, such as when the catalyst 46 is warmed up.

  When it is determined in step 100 that the current opening degree of the WGV 44 is controlled according to the base WGV opening degree, the port injection fuel pressure is calculated according to the function f (WGV opening degree) based on the WGV opening degree. (Step 102). The function f (WGV opening) in this step 102 defines the relationship shown in FIG. 4 described above (relationship at the time of the base WGV opening). The opening degree of the WGV 44 can be acquired based on, for example, a drive command value for an actuator (such as an electric motor) that drives the WGV 44.

  On the other hand, when it is determined in step 100 that the current opening degree of the WGV 44 is not controlled in accordance with the base WGV opening degree, the port injection fuel pressure is a function f (intake air pressure based on the intake manifold pressure and the WGV opening degree). It is calculated according to the manifold pressure and the WGV opening (step 104). The function f (intake manifold pressure, WGV opening) in step 102 also defines the relationship shown in FIG.

  According to the routine shown in FIG. 5 described above, when the WGV opening is large in consideration of the magnitude of the WGV opening controlled during the operation of the internal combustion engine 10, the port is compared with the case where the WGV opening is small. The port injection fuel pressure is determined so that the differential pressure (injection differential pressure) between the injection fuel pressure and the intake manifold pressure increases. In other words, when the WGV opening is large, the port injection fuel pressure is corrected to be larger in the direction in which the port injection fuel pressure becomes higher than when the WGV opening is small.

  In the system of the present embodiment, the port injection fuel pressure is adjusted by the variable pressure regulator 38 so that the port injection fuel pressure determined in this way is obtained. As described above, when the injection differential pressure increases, fuel atomization is promoted. Therefore, by adjusting (correcting) the port injection fuel pressure according to the opening degree of the WGV 44 as described above, the deterioration of the atomization state of the fuel accompanying the change in the exhaust pressure according to the change in the opening degree of the WGV 44 is suppressed. can do. As described above, according to the control of the port injection fuel pressure of the present embodiment, in addition to the atomization of the injected fuel and the reduction in the amount of fuel attached to the port wall surface due to the atomization, the intake air blown back due to the change in the opening degree of the WGV 44. Since the influence on the atomization of the fuel can be suppressed to the minimum, the optimum atomization state of the fuel can always be obtained even when the opening degree of the WGV 44 is changed as compared with the case where this control is not performed. .

  In the first embodiment described above, the ECU 56 controls the variable pressure regulator 38 so as to obtain the port injection fuel pressure determined by the routine processing shown in FIG. "Pressure adjusting means" is realized.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake passage 12a Intake manifold 12b Intake port 14 Exhaust passage 18 Air flow meter 20 Turbocharger 20a Compressor 20b Turbine 24 Throttle valve 26 Intake pressure sensor 28 Fuel injection valve 30 Spark plug 32 Fuel supply piping 34 Fuel pump 36 Fuel Tank 38 Variable pressure regulator 40 Return pipe 42 Exhaust bypass passage 44 Waste gate valve (WGV)
48 Intake valve 50 Exhaust valve 52 Intake variable valve mechanism 54 Exhaust variable valve mechanism 56 ECU (Electronic Control Unit)
58 Crank angle sensor

Claims (1)

A fuel injection valve for injecting fuel into the intake port;
A turbocharger having a turbine operating by exhaust energy in the exhaust passage;
An exhaust bypass passage that branches off from the exhaust passage at a portion upstream of the turbine and merges with the exhaust passage at a portion downstream of the turbine;
A waste gate valve for opening and closing the exhaust bypass passage;
Fuel pressure adjusting means for adjusting the fuel pressure supplied to the fuel injection valve;
With
In the case where a valve overlap period in which the valve opening period of the intake valve overlaps the valve opening period of the exhaust valve is provided, the fuel pressure adjusting means is configured to cancel the waste gate valve when the opening degree of the waste gate valve is large. With a supercharger, wherein the fuel pressure is adjusted so that the differential pressure between the fuel pressure and the intake passage pressure in the atmosphere of the fuel injection valve is larger than when the opening of the gate valve is small Control device for internal combustion engine.

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