JP2012067624A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that the acceleration performance at engine acceleration degrades when a fuel amount increase rate is set to 1 (0% increase) in most of the engine operation region including a supercharging area.SOLUTION: A device calculates a first fuel amount increase rate F1 corresponding to a current intake air amount (S11) and a second fuel amount increase rate F2 corresponding to an output mixture ration (S12), and determines whether or not an internal combustion engine is under an acceleration operation state (S14) on the basis of an intake air amount detected by an air flow meter and engine rotation speed. When the internal combustion engine is determined not to be under an acceleration operation state, the first fuel amount increase rate F1 is set to a fuel amount increase rate F0 (S17). When the engine internal combustion engine is determined to be under an acceleration operation state, the larger one of the first fuel amount increase rate F1 and second fuel amount increase rate F2 is set as the fuel amount increase rate F0 (S15-S17). Fuel injection control is executed on the basis of the set fuel amount increase rate F0.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to setting of a fuel increase rate.

  Patent Document 1 discloses a second fuel increase rate obtained based on a first fuel increase rate, an engine rotation speed, and an intake air amount in an internal combustion engine including a supercharger that performs supercharging using exhaust energy. The larger one is set as the fuel increase rate. The first fuel increase rate is 1 in the non-accelerated state where the accelerator opening is equal to or less than a predetermined reference value, that is, 0%, and supercharging is performed in the acceleration operation state where the accelerator opening exceeds the reference value. It is set according to the pressure, that is, if the supercharging pressure is equal to or higher than a predetermined reference value, the amount is increased by 16% which is the maximum value according to the power air-fuel ratio. On the other hand, when the supercharging pressure is less than the reference value, the first fuel increase rate is set according to the gear ratio, and is smaller than the maximum value (6% to 16%) for improving engine output and improving fuel efficiency. Increase).

JP 2008-144736

  In recent years, regulations on exhaust emissions have become stricter. For example, even in an internal combustion engine equipped with a turbocharger, in order to reduce fuel consumption and exhaust emissions, the turbocharger is excluded except for some high-speed and high-load areas. In most engine operation regions including the engine range, it is considered that the fuel increase rate is 1 (0% increase), that is, the operation is performed at the stoichiometric air-fuel ratio without increasing the fuel. In such an internal combustion engine, the intake air amount is used as a parameter for the injection control in order to perform the fuel injection control in consideration of the emission in the supercharging region.

  However, when the internal combustion engine is in an accelerating operation state due to the driver's acceleration request, if the fuel increase rate is 1 (0% increase) corresponding to the intake air amount, sufficient acceleration performance cannot be obtained, and the fuel increase amount Need to do.

  On the other hand, even if the fuel increase rate is set so that the output mixture ratio is simply determined when accelerating operation is determined, if the load is high, the increase rate set for protecting the exhaust system parts (output mix ratio Therefore, the exhaust system parts may not be sufficiently protected during acceleration operation.

  Therefore, in the present invention, in order to reduce fuel consumption and exhaust emissions, in the engine that does not perform fuel increase in most engine operation regions including the supercharge region except for a part of the high load region, the supercharge region However, it is an object of the present invention to provide a control device for an internal combustion engine that satisfies the emission and further can sufficiently protect the exhaust system parts while satisfying the acceleration even when the driver makes an acceleration request.

  The present invention has been made in view of such circumstances. That is, the present invention includes an intake air amount detection unit that detects an intake air amount, and a first fuel increase rate calculation unit that calculates a first fuel increase rate based on the intake air amount detected by the intake air amount detection unit. A second fuel increase rate calculating means for calculating a second fuel increase rate corresponding to the output mixture ratio, an acceleration determining means for determining whether or not the internal combustion engine is in an accelerated operation state, and an acceleration operation by the acceleration determining means When it is determined that it is not in the state, the first fuel increase rate is set as the fuel increase rate. On the other hand, when it is determined that it is in the acceleration operation state, the first fuel increase rate and the second fuel increase rate are set. And a fuel increase rate setting means for setting the fuel increase rate as the fuel increase rate and performing fuel injection control based on the set fuel increase rate.

  In the non-accelerated operation state, the first fuel increase rate corresponding to the current engine speed and intake air amount is set as the fuel increase rate used for fuel injection control. By setting the increase rate to 1 (0% increase) corresponding to the stoichiometric air-fuel ratio, it is possible to reduce fuel consumption and exhaust emission.

  On the other hand, when the driver suddenly depresses the accelerator, it is determined that the vehicle is in an accelerated operation state. In this case, the second fuel increase rate corresponding to the output air-fuel ratio exceeds the first fuel increase rate. Since the second fuel increase rate is set as the fuel increase rate, the fuel increase is quickly performed and the acceleration performance can be improved. In particular, in the case of an internal combustion engine equipped with a turbocharger, the exhaust volume increases due to the increase in fuel, and the start-up of supercharging can be accelerated.

  Further, in the high rotation and high load range where fuel increase is required from the viewpoint of component protection, the first fuel increase rate set according to the engine speed and the intake air amount (load) becomes a high value. By setting the increase rate as the fuel increase rate used for the fuel injection control, the exhaust gas temperature can be appropriately lowered by the fuel increase.

  According to the present invention, it is possible to reduce fuel consumption and exhaust emission while ensuring acceleration performance in an accelerated operation state, and to achieve both exhaust performance and acceleration performance.

BRIEF DESCRIPTION OF THE DRAWINGS The system block diagram which shows simply the control apparatus of the internal combustion engine which concerns on one Example of this invention. The flowchart which shows the setting process of the fuel increase rate which concerns on a present Example. The flowchart which shows the subroutine of the acceleration determination process of FIG. The figure which shows the setting map of the 1st fuel increase rate which concerns on a present Example. The figure which shows the setting map of the 2nd fuel increase rate which concerns on a present Example. The timing chart which shows changes, such as a fuel increase rate before and behind acceleration which concerns on a present Example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 schematically shows a spark ignition type gasoline internal combustion engine equipped with a turbocharger as an embodiment of the present invention. A plurality (four in this example) of cylinders 2 are arranged in series in the cylinder block 1 of the internal combustion engine, and pistons are slidably fitted in the cylinders 2. In the intake passage 3 for supplying air to the cylinder 2, an electrically controlled throttle (valve) 4 for adjusting the intake air amount is arranged, and on the upstream side thereof, a turbocharger 9, specifically, a compressor 9a is provided. It is intervened. The throttle 4 is electrically controlled so that the opening degree can be adjusted independently of the operation of the accelerator pedal 17 by the driver. An exhaust turbine 9 b that drives the compressor 9 a is interposed in the exhaust passage 5. Further, a boost pressure sensor 12 for detecting an intake pressure downstream of the throttle, that is, a boost pressure Pb, is disposed downstream of the throttle 4 in the intake passage 3. A known three-way catalyst 21 is interposed in the exhaust passage 5 downstream of the exhaust turbine 9b.

  As a means for adjusting the supercharging pressure, in this embodiment, the outlet side and the inlet side of the exhaust turbine 9b are connected by an exhaust bypass passage 10, and an electrically controlled wastegate valve 11 is interposed in the bypass passage 10. ing. The waste gate valve 11 is opened on the engine high speed side so as to keep the supercharging pressure at a predetermined characteristic.

  The control unit 13 as a control unit includes an accelerator opening APO by an accelerator opening sensor 18 that detects an opening of an accelerator pedal 17 operated by a driver, an engine rotational speed detected by a rotational speed sensor 15, and intake air. In addition to the intake air amount detected by the air flow meter 16 as the amount detecting means and the supercharging pressure detected by the supercharging pressure sensor 12, detection signals such as cooling water temperature and hydraulic pressure are input. The control unit 13 then outputs an injector signal 19 and an ignition signal 20 to the fuel injection valve and the ignition device based on various detection signals representing these engine operating states, so that the fuel injection timing, the fuel injection amount, and the ignition timing are output. And a control signal is output to the throttle 4 to control the throttle opening and the like.

  FIG. 2 is a flowchart showing the flow of control processing according to this embodiment, and this routine is repeatedly executed by the control unit 13 every 10 ms, for example. Based on the fuel increase rate F0 set in this routine, fuel injection control by the fuel injection valve is performed.

In step S11, referring to a preset control map shown in FIG. 4 based on the engine speed and the intake air amount, the first fuel increase rate F1, which is the fuel increase rate corresponding to the current intake air amount, is determined. calculate. The engine rotation speed is detected by the rotation speed sensor 15 described above. The intake air amount is obtained using any one of the following [1] to [4]. Although not shown, the throttle opening sensor detects the opening of the throttle 4, the intake air temperature sensor detects the intake air temperature, and the atmospheric pressure sensor detects the atmospheric pressure. .
[1] Air flow meter 16
[2] Supercharging pressure sensor (collector pressure sensor) 12
[3] Throttle opening sensor, intake air temperature sensor, and atmospheric pressure sensor [4] Throttle opening sensor, intake air temperature sensor, and supercharging pressure sensor (throttle upstream pressure sensor)
As shown in FIG. 4, in this embodiment, supercharging by the turbocharger 9 is performed so that the three-way catalyst 21 (see FIG. 1) provided in the exhaust passage 5 functions effectively to reduce exhaust emissions. The first fuel increase rate F1 is set to 1 so that the air-fuel ratio becomes the stoichiometric air-fuel ratio in most engine operating regions except the high-speed high-load region including the supercharging region where the engine is operated. On the high rotation / high load side, in order to suppress an excessive increase in the exhaust gas temperature, the first fuel increase rate F1 is set higher than 1 to make the air-fuel ratio rich.

  Referring to FIG. 2 again, in step S12, a second fuel increase rate F2 corresponding to the output request is calculated. The second fuel increase rate F2 is a fuel increase rate corresponding to the output mixture ratio, and is obtained from the engine speed with reference to a preset control map as shown in FIG. The output mixture ratio is used at the time of transmission or acceleration, and is a value on the richer side than the stoichiometric air-fuel ratio in most of the operation range except for a low rotation speed range below a predetermined rotation speed Ne0 (1800 to 2800 rpm). Therefore, as shown in FIG. 5, the second fuel increase rate is set to 1 corresponding to the theoretical air-fuel ratio in the region where the predetermined rotational speed Ne0 or less, and in most of the rotational region exceeding the predetermined rotational speed Ne0, the output mixture ratio For example, a value greater than 1 corresponding to 1 is set to about 1.03 corresponding to a fuel increase of about 3%.

  In step S13 of FIG. 2, it is determined whether or not the internal combustion engine is in an acceleration operation state by a subroutine of FIG. 3 to be described later. If it is determined that the engine is not in the acceleration operation state, the process proceeds to step S17, and the first fuel increase rate F1 is set as the fuel increase rate F0 used for fuel injection control.

  If it is determined in step S14 that the vehicle is in the acceleration operation state, in steps S15 to S17, the larger value of the first fuel increase rate F1 and the second fuel increase rate F2 is used for fuel injection control. Set as F0. Specifically, in step S15, it is determined whether the second fuel increase rate F2 is greater than the first fuel increase rate F1. If the second fuel increase rate F2 is larger than the first fuel increase rate F1, the process proceeds to step S16, and the larger second fuel increase rate F2 is set as the fuel increase rate F0. On the other hand, if the second fuel increase rate F2 is equal to or less than the first fuel increase rate F1, the process proceeds to step S17, and the larger first fuel increase rate F1 is set as the fuel increase rate F0.

  FIG. 3 is a subroutine showing details of the acceleration determination process in step S13 of FIG. In this routine, it is determined that the internal combustion engine is in an acceleration operation state when either the fully open determination based on the throttle opening (step S21) or the rapid acceleration determination based on the accelerator opening (steps S22, S23) is satisfied. Yes.

  Specifically, in step S21, it is determined whether the target throttle opening TGTVO is equal to or greater than a predetermined determination value sTGTVO corresponding to full throttle. If the target throttle opening degree TGTVO is greater than or equal to the determination value sTGTVO, the process proceeds to step S24, where it is determined that the internal combustion engine is in the acceleration operation state.

  On the other hand, if the target throttle opening degree TGTVO is less than the determination value sTGTVO, the process proceeds to step S22, and it is determined whether the accelerator opening degree APO is equal to or greater than the predetermined determination value sAPO. In step S23, it is determined whether the accelerator opening increase rate DAPO is equal to or greater than a predetermined determination value sDAPO. The increase rate DAPO of the accelerator opening can be obtained, for example, from the difference between the accelerator opening before a predetermined period and the current accelerator opening. When the accelerator opening APO is equal to or greater than the predetermined determination value sAPO and the increase rate DAPO of the accelerator opening is equal to or greater than the predetermined determination value sDAPO, the acceleration request by the driver is large as in sudden acceleration. It progresses to step S24 and it determines with it being in an acceleration driving state. In other cases, the process proceeds to step S25, and it is determined that the engine is not in the accelerated operation state, that is, the non-accelerated operation state.

  FIG. 6 is a timing chart showing changes in the fuel increase rate and the like in the acceleration transition period according to this embodiment. Since the driving state before acceleration before time t1 is a non-acceleration state, the first fuel increase rate F1 is set as the fuel increase rate F0. Since the first fuel increase rate F1 is set to 1 (0% increase) in most regions including the supercharging region, fuel efficiency and exhaust performance can be improved.

  If it is determined at time t1 that the accelerator is operating due to a rapid increase in the accelerator opening (acceleration determination is ON), the larger of the first fuel increase rate F1 and the second fuel increase rate F2 is the fuel. The increase rate F0 is set. In the present embodiment, since the first fuel increase rate F1 is set to 1 in many regions including the supercharging region, in many cases in the operating state immediately after acceleration, as shown in FIG. The second fuel increase rate F2 corresponding to the mixture ratio is set as the fuel increase rate F0.

  Thus, acceleration performance can be improved by quickly increasing the fuel amount during acceleration. In particular, in the case of the internal combustion engine 1 having the turbocharger 9 as in the present embodiment, there is a supercharging delay when the amount of increase corresponding to the amount of intake air is increased. Therefore, the fuel increase rate corresponding to the amount of intake air is increased. Although the actual fuel increase may be delayed due to the low estimation, it may not be possible to satisfy the desired acceleration request. However, in this embodiment, the exhaust gas, which is the total mass flow rate of intake air and fuel, is increased by increasing the fuel. The volume will increase, and the rise of supercharging can be accelerated.

  In addition, under the condition of low atmospheric pressure such as high altitude, the amount of intake air decreases, and the fuel increase rate corresponding to the amount of intake air may not be able to satisfy the desired acceleration request. Even in such a situation, by using the second fuel increase rate F2 corresponding to the output air-fuel ratio, it is possible to perform an appropriate fuel increase regardless of a decrease in the intake air amount.

  Then, at the time t2 when the first fuel increase rate F1 exceeds the second fuel increase rate F2 as the engine load and the rotational speed increase, the first fuel increase rate F1 is set again as the fuel increase rate F0. That is, since the fuel increase rate F0 is switched from the second fuel increase rate F2 to the first fuel increase rate F1 at the time point t2 when the first fuel increase rate F1 reaches the second fuel increase rate F2, the fuel increase rate F0 Since the first fuel increase rate F1 (that is, the fuel increase rate F0) increases as the engine load and the rotational speed increase without causing a sudden change, the exhaust temperature excessively increases due to an appropriate fuel increase. Can be prevented.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes without departing from the spirit of the present invention. . For example, in the above embodiment, the second fuel increase rate F2 at a predetermined rotation speed Ne0 or higher is set to a constant value (1.03). However, as the engine speed increases, the second fuel increase rate F2 is increased stepwise or continuously. It may be changed as desired. The present invention is not limited to an internal combustion engine provided with a turbocharger, but can also be applied to a naturally aspirated (NA) type internal combustion engine that does not have a turbocharger.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 9 ... Turbocharger 13 ... Control unit 16 ... Air flow meter (intake air amount detection means)

Claims (3)

An intake air amount detection means for detecting an intake air amount;
First fuel increase rate calculating means for calculating a first fuel increase rate based on the intake air amount detected by the intake air amount detecting means;
A second fuel increase rate calculating means for calculating a second fuel increase rate corresponding to the output mixture ratio;
Acceleration determining means for determining whether or not the internal combustion engine is in an accelerated operation state;
When it is determined by the acceleration determining means that the engine is not in the accelerated operation state, the first fuel increase rate is set as the fuel increase rate. On the other hand, when it is determined that the engine is in the accelerated operation state, the first fuel increase rate is set. A fuel increase rate setting means for setting a larger one of the rate and the second fuel increase rate as a fuel increase rate, and performing fuel injection control based on the set fuel increase rate;
A control apparatus for an internal combustion engine, comprising: A turbocharger is provided for supercharging with the exhaust energy of the internal combustion engine;
2. The control device for an internal combustion engine according to claim 1, wherein the first fuel increase rate calculating means sets the first fuel increase rate to 1 in most engine operation regions including a supercharging region.   3. The control apparatus for an internal combustion engine according to claim 1, wherein the second fuel increase rate calculating means calculates a second fuel increase rate based on the engine speed.

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