JP2009221886A - Method for controlling operation of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein change of an air-fuel ratio changes torque and causes rotation fluctuation when an internal combustion engine is started at an rich air-fuel ratio and the air-fuel ratio is made lean after that in order to avoid start failure in a cold start due to characteristics of gasoline. <P>SOLUTION: Fuel correction quantity and intake air correction quantity with which operation of the internal combustion engine can be surely continued under a rich air-fuel ratio condition after the start of the internal combustion engine are set as limit adaptation injection quantity and limit adaptation intake correction quantity. Fuel injection quantity in operation with fuel injection quantity less than the limit adaptation injection quantity is defined as lean adaptation injection quantity. Intake air correction quantity set larger as difference between the limit adaptation injection quantity and the lean adaptation injection quantity is larger is set as lean adaptation intake air correction quantity with corresponding to the limit adaptation injection quantity and the lean adaptation injection quantity. The internal combustion engine is operated using the lean adaptation injection quantity and the lean adaptation intake air correction quantity if it is possible to do so in operation of the internal combustion engine after the start. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an operation control method for an internal combustion engine after increasing a fuel injection amount at start-up.

  Conventionally, in an engine using gasoline as an internal combustion engine as fuel, the fuel injection amount is temporarily increased in order to improve starting, and thereafter the fuel injection amount is gradually decreased so that the air-fuel ratio becomes the stoichiometric air-fuel ratio. It is known to control driving so that In this case, the amount by which the fuel injection amount is reduced is, for example, the air-fuel ratio in order to prevent the air-fuel ratio from becoming lean due to the influence of the properties of the gasoline or system variations and causing fluctuations in the rotation. Is set to be rich.

On the other hand, in order to reduce the total hydrocarbon (THC) emissions until the O ₂ sensor is activated at the time of starting, the engine tends to operate with the air-fuel ratio as lean as possible during that period. is there. For example, in the one disclosed in Patent Document 1, the fuel injection amount is corrected and increased at start-up while monitoring the engine rotational fluctuation, and the increased fuel injection amount is decreased, so that the empty fuel is discharged immediately after the cold start. The operation is controlled by making the fuel ratio lean. In this case, in the predetermined period after the completion of the start-up, the reduction in the fuel injection amount is set to be larger than that after the predetermined period has elapsed.
JP-A-10-184422

  However, with such a configuration, since the air-fuel ratio is adjusted to be lean only by reducing the fuel injection amount, the torque may change due to the change in the air-fuel ratio, resulting in rotational fluctuations. is there. In such a case, for example, when heavy gasoline is used, if the amount of fuel is reduced as described above, there is a possibility that torque will decrease and rotational fluctuation will occur. In such a case, it is necessary to correct the intake air amount. However, if the intake air amount is to be corrected by feedback control, it takes time until the corrected intake air is reflected in the operation of the engine.

  Therefore, the present invention aims to eliminate such problems.

  That is, according to the internal combustion engine operation control method of the present invention, after the internal combustion engine is started, the fuel correction amount and the intake air correction value that can reliably continue the operation of the internal combustion engine in a state where the air-fuel ratio is rich are limit-adapted injection. The fuel injection amount when operating with a fuel injection amount smaller than the limit adaptation injection amount is set as the lean adaptation injection amount, and the difference between the limit adaptation injection amount and the lean adaptation injection amount is set. When the difference is larger and the difference is larger, the intake air correction amount that is set to be larger is set as the lean compatible intake correction amount, and when it is possible in the operation after starting the internal combustion engine, the lean compatible injection amount and the lean compatible intake correction amount are And operating an internal combustion engine.

  According to such a configuration, by operating the internal combustion engine with the intake air correction amount, that is, the lean adaptive intake correction amount, in accordance with the fuel amount reduced from the lean adaptive injection amount with reference to the limit adaptive injection amount, The difference in torque when the fuel ratio is changed is grasped as a lean compatible intake correction amount. Therefore, it is possible to stabilize the rotation of the internal combustion engine.

  The present invention is configured as described above, and even if the air-fuel ratio is made lean after starting and the total hydrocarbon amount is reduced, the engine rotation is prevented from lowering due to torque fluctuations. be able to.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

An engine 100 schematically shown in FIG. 1 is a spark ignition type four-cycle four-cylinder for an automobile, and the intake system 1 is a so-called electronic type that opens and closes by driving a motor in response to an accelerator pedal (not shown). The throttle valve 2 is disposed, and a surge tank 3 is provided downstream thereof. A fuel injection valve 4 is further provided in the vicinity of one end communicating with the surge tank 3, and the fuel injection valve 4 is controlled by the electronic control device 5. The cylinder head 7 forming the combustion chamber 6 is provided with an intake valve 8 and an exhaust valve 9, and a spark plug 10 that generates a spark is attached. Further, in the exhaust system 11, an O ₂ sensor 12 that constitutes an air-fuel ratio detecting means for measuring the oxygen concentration in the exhaust gas is a ternary that is a catalyst disposed in a pipeline leading to a muffler (not shown). It is attached at a position upstream of the catalyst 13. In FIG. 1, the configuration of one cylinder of engine 100 is shown as a representative.

The electronic control unit 5 that detects and controls the operating state of the engine 100 is mainly composed of a microcomputer system including a central processing unit 14, a storage unit 15, an input interface 16, and an output interface 17. Has been. The input interface 16 outputs an intake pressure signal a output from an intake pressure sensor 18 for detecting the pressure in the surge tank 3, that is, an intake pipe pressure, and an output from a cam position sensor 19 for detecting the rotation state of the engine 100. Cylinder discriminating signal G1, crank angle reference position signal G2, engine speed signal b, vehicle speed signal c output from the vehicle speed sensor 20 for detecting the vehicle speed, idle switch for detecting the open / closed state of the throttle valve 2 The IDL signal d output from the engine 21, the water temperature signal e output from the water temperature sensor 22 for detecting the coolant temperature of the engine 100, the current signal h output from the O ₂ sensor 12, and the like are input. On the other hand, from the output interface 17, a fuel injection signal f is output to the fuel injection valve 4 and an ignition pulse g is output to the spark plug 10.

  The electronic control unit 5 uses the intake pressure signal a output from the intake pressure sensor 18 and the rotation speed signal b output from the cam position sensor 19 as main information, and various kinds of information determined according to the operating state of the engine 100. The basic injection time (basic injection amount) is corrected by the correction coefficient to determine the fuel injection valve opening time, that is, the final injector energization time T, and the fuel injection valve 4 is controlled based on the determined energization time to correspond to the engine load. A program for injecting fuel into the intake system 1 is incorporated. Further, while the fuel injection of the engine 100 is controlled in this way, after the engine 100 is started, the fuel correction amount and the correction value of the intake air that can reliably continue the operation of the engine 100 with the air-fuel ratio being rich are limited. The fuel injection amount that is set as the adaptive injection amount and the limit adaptive intake correction amount, the fuel injection amount when operating with a fuel injection amount that is smaller than the limit adaptive injection amount is the lean adaptive injection amount, and the limit adaptive injection amount and the lean adaptive injection amount The correction amount of intake air that is set to be larger as the difference is larger is set as the lean compatible intake correction amount, and when it is possible to operate after the engine 100 is started, the lean compatible injection amount and the lean compatible intake correction An operation control program for operating the internal combustion engine using the amount is built in the electronic control unit 5.

The operation of this operation timing control program will be described with reference to the flowchart of FIG. The operation timing control program is repeatedly executed at predetermined intervals after the engine 100 is started and until the O ₂ sensor 12 is activated and the air-fuel ratio feedback control is executed. In this operation control program, initial values of the fuel injection amount and the intake correction amount corresponding to the coolant temperature or engine temperature, the load (intake air amount or intake air pressure), and the engine speed are set as control data at the time of starting. For example, it is set as a map. The map includes a limit adaptation injection amount and a limit adaptation intake correction amount, and a lean adaptation injection amount.

The limit adaptation injection amount and the limit adaptation intake correction amount are determined when the engine 100 is started and the O ₂ sensor 12 is activated in the cold start regardless of the property of gasoline that can be generally used as a fuel. The amount is set so that the engine 100 can be continuously operated until the air-fuel ratio feedback control can be executed. In particular, for example, even when heavy gasoline is used, the engine 100 can be started in the cold state, and after the start, for example, the air-fuel ratio feedback control is performed so that the idling operation is continued to become the stoichiometric air-fuel ratio. The limit-adapted injection amount and the limit-adapted intake correction amount are set so as to maintain an air-fuel ratio that can execute the above. Therefore, the state in which the air-fuel ratio is rich in claim 1 may be an air-fuel ratio state with a fuel amount sufficient to start the engine 100, and is slightly different from a state in which the air-fuel ratio is rich with respect to the theoretical air-fuel ratio. Including a lean state, and is not necessarily limited to a state where the air-fuel ratio is richer than the stoichiometric air-fuel ratio. In FIG. 2, the change in the air-fuel ratio when the limit-fit injection amount is injected is shown by a solid line.

On the other hand, the lean compatible injection amount is slightly changed from the vicinity of the theoretical air fuel ratio as soon as possible in the period from immediately after starting with the limit compatible injection amount and the limit compatible intake correction amount until the O ₂ sensor 12 is activated. It is set by calculation so as to become lean, and is equivalent to the limit-adapted injection amount up to the point when the air-fuel ratio is made the richest. In particular, for example, when using high-quality gasoline opposite to heavy gasoline, lean operation can be continued even if the injection amount is reduced more rapidly than the change in the limit-fit injection amount. An appropriate injection amount is set. In FIG. 2, the change of the air-fuel ratio when the lean compatible injection amount is injected is shown by a dotted line.

  When the operation control program is executed, first, in step S1, a limit compatible injection amount and a limit compatible intake correction amount are calculated. In this calculation, the initial values of the limit-adapted injection amount and the limit-adapted intake correction amount are determined based on the coolant temperature and the load at this time, and then calculated based on the respective initial values.

  Next, in step S2, the lean compatible injection amount is calculated in the same manner as the calculation of the limit compatible injection amount. In step S3, the difference between the limit compatible injection quantity obtained by calculation and the lean compatible fuel injection quantity is calculated.

  In step S4, it is determined whether or not the obtained difference is zero. If the difference is not 0, the process proceeds to step S5, and if it is 0, the process proceeds to step S6.

  In step S5, a lean adaptive intake correction amount is calculated based on the obtained difference. In this case, the lean adaptive intake correction amount may be set by a map, for example. For example, as shown in FIG. 3, the larger the difference is, the larger the intake correction amount, that is, the correction amount for increasing the intake air amount in idle rotation control (ISC) is set to be larger. On the other hand, in step S6, the operation of the engine 100 is controlled based on the calculated limit adaptive injection amount and limit adaptive intake correction amount.

  In step S7, the fuel of the lean compatible injection amount is injected, the intake air amount is corrected based on the lean compatible intake correction amount, and the internal combustion engine is operated.

  In such a configuration, when the engine 100 is started and the difference between the calculated limit adaptive injection amount and the lean optimal injection amount is 0, the control proceeds to step S1 to step S4 and step S6, and the limit compliance is achieved. The engine 100 is operated with the injection amount and the limit adaptive intake correction amount. As a result, engine 100 is operated in a state where the air-fuel ratio is rich, and therefore engine 100 can be reliably started without misfire.

  If the operation is continued with the air-fuel ratio being rich in this way and the difference is not 0, that is, it is determined that the difference is greater than 0, Steps S1 to S5 and Step S7 are executed, and the difference is determined. The engine 100 is operated based on the lean-adapted intake correction amount and the lean-adapted injection amount calculated in the above. In this case, since the initial value is set so that the lean compatible injection amount is less than the limit compatible injection amount, when operating with the lean compatible injection amount and the lean compatible intake correction amount, the limit compatible injection amount and the limit compatible injection amount are set. The air-fuel ratio becomes leaner than when operating with the intake correction amount. In this case, the lean adaptive intake correction amount increases as the difference increases, and therefore the intake air amount is increased in the idle rotation control.

  Therefore, although the lean adaptive injection amount is decreased from the limit adaptive injection amount, the intake air amount increases, so that a decrease in torque due to a change in the air-fuel ratio can be suppressed. Therefore, the engine 100 can be operated with stable rotation, and the air-fuel ratio can be made closer to the stoichiometric air-fuel ratio than the rich air-fuel ratio by the limit-fit injection quantity, so that the total hydrocarbon emissions can also be reduced. it can.

  In addition, this invention is not limited to the above-mentioned embodiment.

  In the above-described embodiment, the lean adaptive intake correction amount is calculated based on the difference between the limit adaptive injection amount and the lean adaptive injection amount. However, this difference may be used as the correction limit amount of the lean adaptive injection amount. . That is, when calculating the lean compatible injection amount, the lean limit injection amount is regulated by the correction limit amount set based on the difference to prevent the lean compatible injection amount from being excessively reduced. . The correction limit amount is set larger as the difference becomes larger.

Therefore, for example, when heavy gasoline is used, even if the rotational speed decreases due to the lean compatible injection amount, the maximum and limit compatible injection can be achieved by correcting and setting the lean compatible injection amount using the correction limit amount. By injecting the fuel according to the amount, rotation fluctuation due to torque fluctuation can be suppressed. Therefore, the engine operation can be controlled without detecting the air-fuel ratio until the O ₂ sensor is activated.

  In the above-described embodiment, the idle rotation control is performed by adjusting the opening of the throttle valve. However, a bypass route that bypasses the throttle valve is provided, and an electromagnetic on-off valve is provided in the bypass route, and passes through the bypass route. The structure which increases / decreases air quantity may be sufficient.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows schematic structure of the engine of embodiment of this invention. The graph which shows the change of the air fuel ratio at the time of injecting the limit adaptation injection quantity and lean adaptation injection quantity of the embodiment. The graph which shows the relationship between the lean compatible intake correction amount and difference of the embodiment. The flowchart which shows the control procedure of the embodiment.

Explanation of symbols

14 ... Central processing unit 15 ... Storage device 16 ... Input interface 17 ... Output interface

Claims (1)

After starting the internal combustion engine, set the fuel correction amount and intake air correction value that can reliably continue the operation of the internal combustion engine in a state where the air-fuel ratio is rich, as the limit adaptation injection amount and the limit adaptation intake correction amount,
The fuel injection amount when operating with a fuel injection amount smaller than the limit adaptation injection amount is set as the lean adaptation injection amount, and the intake corresponding to the difference between the limit adaptation injection amount and the lean adaptation injection amount is set to be larger as the difference is larger Set the air correction amount as the lean compatible intake correction amount,
An operation control method for an internal combustion engine, wherein the internal combustion engine is operated using a lean compatible injection amount and a lean compatible intake correction amount when the internal combustion engine can be operated after starting.

Images