JP2007032320A - Controller of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly perform fuel cut control according to operating conditions. <P>SOLUTION: When fuel cut conditions are established (determined to be YES in S100), an engine ECU compares a vehicle speed at that time with a reference value Vth. While a vehicle is traveling (determined to be YES in S110), A delay period Tfd is secured by T1 between a time when the fuel cut conditions are satisfied and a time when the fuel injection is actually stopped so that deceleration shock is not increased by the execution of rapid fuel cut according to S120. When the delay period is secured in the same manner as in a vehicle traveling state when the vehicle is stopped, a catalyst may be excessively heated due to the occurrence of misfire in a combustion chamber before fuel cut. To prevent this problem, the engine ECU sets the delay period Tfd to T2 shorter than in the traveling state in the fuel cut when the vehicle is stopped. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device that performs control to stop fuel supply to an internal combustion engine (hereinafter also referred to as fuel cut) under predetermined operating conditions.

  Conventionally, as disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 8-144814) and the like, in an electronically controlled fuel injection control device for an internal combustion engine, a fuel cut for stopping fuel supply to the internal combustion engine in a predetermined operating state Control is taking place. Typically, when the throttle is fully closed and the engine speed is equal to or higher than a predetermined speed, it is judged that the fuel supply is in an unnecessary deceleration state, and the fuel injection and the exhaust properties are improved by stopping the fuel injection. The fuel cut at the time of deceleration is performed to prevent the heating of the fuel. In addition, in order to prevent engine damage due to the engine speed rising to the red zone or higher, fuel cut at high revolutions that stops fuel injection at a predetermined limit rotational speed or higher and suppresses the increase in rotational speed, or more than predetermined There is also known a fastest fuel cut that stops fuel injection when the high speed / high rotation speed state continues for a predetermined time.

In particular, in Patent Document 1, when the catalyst temperature detected by the catalyst temperature detecting means is higher than a predetermined value, the execution of the fuel supply stop control is stopped to prevent the catalyst from being deteriorated due to the high temperature lean atmosphere. It is disclosed that measures are taken.
JP-A-8-144814

  When actually performing fuel cut control, from the viewpoint of alleviating deceleration shocks and ensuring driving comfort, from the establishment of a predetermined fuel cut condition such as full closing of the throttle valve to the actual stop of fuel supply It is necessary to set a delay period in between.

  Therefore, it is necessary to appropriately set the length of the delay period in order to smoothly perform fuel cut control. In particular, if the delay period is set inappropriately and misfire occurs in the combustion chamber, unburned fuel is discharged to the catalyst during the period from the misfire until fuel cut starts. When the minute and air react, there is a possibility that the exhaust system will be overheated.

  The present invention has been made in order to solve such problems, and an object of the present invention is to smoothly perform fuel cut in accordance with an operation state in a control device for an internal combustion engine.

  The control apparatus for an internal combustion engine according to the present invention can execute a fuel cut for stopping the fuel supply to the internal combustion engine when a predetermined operating condition is satisfied. The control device includes detection means, delay period setting means, and fuel cut start means. The detecting means detects establishment of a predetermined operating condition. The delay period setting means sets a delay period from the time when the driving condition is satisfied to the start of fuel cut according to the vehicle speed at that time when the detection means detects that the predetermined driving condition is satisfied. The fuel cut start means starts fuel cut from the time when the delay period set by the delay period setting means from the time when the predetermined operating condition is established by the detection means.

  According to the control apparatus for an internal combustion engine, the delay period until the fuel cut is started when a predetermined operating condition (fuel cut condition) is satisfied can be variably set according to the vehicle speed. Therefore, operating conditions should be avoided so as to avoid the occurrence of deceleration shock, which is a problem when the delay period is too short, and the occurrence of catalyst temperature rise due to misfire in the combustion chamber, which is a problem when the delay period is too long. The delay period can be set appropriately according to (vehicle speed). Thereby, a fuel cut can be smoothly performed according to a condition.

  Preferably, in the control apparatus for an internal combustion engine according to the present invention, the delay period setting means sets the delay period to the first period when the vehicle speed is higher than the reference speed, while the delay period is set when the vehicle speed is equal to or less than the reference speed. Is set to a second period shorter than the first period. In particular, the reference speed is set to a value for determining whether or not the vehicle is stopped.

  According to the control apparatus for an internal combustion engine, the deceleration shock due to the fuel cut does not occur at a low speed (especially when the vehicle is stopped), and the delay period is set particularly when the fuel cut is performed after racing (high-speed idling) while the vehicle is stopped. Considering the fact that taking a long time may lead to misfire (light load misfire) due to exceeding the light load side combustion limit, the delay period at low speed (especially when the vehicle is stopped) should be set short and the combustion chamber It is possible to prevent the catalyst temperature from increasing due to misfire in the reactor. In addition, even during high speeds during traveling, air amount correction to avoid light load conditions that exceed the misfire limit can be performed without impairing driving comfort (drivability), so a certain delay period is secured. Even so, the possibility of light load misfire is low. Therefore, during non-low speed (during traveling), it is possible to secure a delay period and reduce the deceleration shock at the time of fuel cut.

  Alternatively, preferably, in the control device for an internal combustion engine according to the present invention, the delay period setting means detects a fully closed state of a throttle valve that adjusts an intake air amount to the internal combustion engine, and the rotational speed of the internal combustion engine is a predetermined value. When it is higher, the establishment of a predetermined operating condition is detected.

  According to the control apparatus for an internal combustion engine, fuel injection can be stopped in a deceleration state where fuel supply is unnecessary, so that fuel efficiency and exhaust properties can be improved and catalyst heating can be prevented.

  According to the control device for an internal combustion engine according to the present invention, it is possible to prevent the occurrence of an excessively high temperature in the catalyst due to a misfire in the combustion chamber and the occurrence of a deceleration shock during operation, and perform smooth fuel cut control according to the operating condition. Can do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and detailed description thereof will not be repeated.

  FIG. 1 shows a schematic configuration diagram of an engine system controlled by an engine ECU (Electronic Control Unit) which is a control device for an internal combustion engine according to an embodiment of the present invention.

  Referring to FIG. 1, air necessary for combustion of engine 100 is filtered by air cleaner 2, passes through throttle body 5, and is distributed to intake pipe 13 of each cylinder by surge tank (intake manifold) 11. The intake air amount is adjusted by a throttle valve 6 provided in the throttle body 5 and measured by an air flow meter 4. The intake air temperature is detected by the intake air temperature sensor 3. Further, the intake pipe pressure is detected by the vacuum sensor 12.

  The opening of the throttle valve 6 is detected by a throttle opening sensor 9. When the throttle valve 6 is in the fully closed state, the idle switch 10 is turned on, and the throttle fully closed signal, which is the output thereof, becomes active.

  The idle adjustment circuit 7 that bypasses the throttle valve 6 is provided with an idle speed control valve (ISCV) 8 for adjusting the air flow rate during idling.

  On the other hand, the fuel stored in the fuel tank 15 is pumped up by the fuel pump 17 and injected into the intake pipe 13 by the fuel injection valve 21 through the fuel pipe 19.

  In the intake pipe 13, such air and fuel are mixed, and the air-fuel mixture is sucked into the engine body, that is, a cylinder (cylinder) 100 through the intake valve 23.

  In the cylinder 100, the air-fuel mixture is compressed by a piston and then ignited by an igniter and a spark plug to explode and burn to generate power.

  The ignition distributor 43 has a crank angle sensor 45 that generates a reference position detection pulse every 720 ° CA in terms of its axis, for example, converted to a crank angle (CA), and a reference position detection pulse every 30 ° CA. A crank angle sensor 47 for generating The engine 100 is cooled by the cooling water introduced into the cooling water passage 49, and the cooling water temperature is detected by the water temperature sensor 51.

The burned air-fuel mixture is discharged as exhaust gas to the exhaust manifold 27 through the exhaust valve 24 and then led to the exhaust pipe 29. The exhaust pipe 29 is provided with an O ₂ sensor 31 for detecting the oxygen concentration in the exhaust gas. Further, a catalytic converter 33 is provided in the exhaust system downstream from the exhaust system, and the catalytic converter 33 simultaneously promotes oxidation of unburned components and reduction of nitrogen oxides in the exhaust gas. Is housed. Thus, the exhaust gas purified in the catalytic converter is discharged into the atmosphere.

  The engine electronic control unit (engine ECU) 60 is a microcomputer system that executes fuel injection control, ignition electrical control, idle rotation speed control, and the like.

  In accordance with a program stored in a ROM (Read Only Memory) 62, a CPU (Central Processing Unit) 61 inputs a signal from each sensor via an A / D conversion circuit 64 or an input interface circuit 65, and outputs the input signal to the input signal. Based on the calculation result, various actuator control signals are output via the output interface circuit 66. A RAM (Random Access Memory) 63 is used as a temporary data storage location in the calculation / control process. Each component in these ECUs is connected by a system bus 69.

  The ignition control timing is to comprehensively determine the state of the engine based on the engine rotation speed and signals from each sensor, determine an optimal ignition timing, and send an ignition signal to the igniter. The idle rotation speed control is to maintain an optimum idle rotation speed by detecting an idle state by a throttle fully closed signal from the idle switch 10 and controlling the ISCV 8 to adjust the air amount.

  In the fuel injection control, basically, a predetermined air-fuel ratio is set for the intake air amount per one rotation of the engine calculated from the intake air flow rate measured by the air flow meter 4 and the engine rotation speed obtained from the crank angle sensor 45. In order to achieve this, the fuel injection amount, that is, the injection time by the fuel injection valve 21 is calculated, and fuel is injected when a predetermined crank angle is reached.

The intake air amount may be estimated from the intake pipe pressure obtained from the vacuum sensor 12 and the engine speed. In this calculation, correction based on signals from the throttle opening sensor 9, the water temperature sensor 51, the intake air temperature sensor 3, the O ₂ sensor 31 and the like is applied.

  The fuel injection control by the engine ECU 60 includes fuel cut control for stopping fuel supply when a predetermined fuel cut condition is satisfied. Typically, when the throttle valve 6 is in a fully closed state and the engine speed is equal to or higher than a predetermined speed, it is determined that the fuel supply is in an unnecessary deceleration state and fuel cut is performed. As for the fuel cut, it is possible to perform a fuel cut at a high rotation speed at a predetermined limit rotation speed or higher, or a maximum speed fuel cut when a high speed / high rotation speed state of a predetermined speed or more continues for a predetermined time. In this embodiment, the fuel cut started in response to the throttle fully closed state will be mainly described.

FIG. 2 is an operation waveform diagram illustrating a control operation at the start of fuel cut.
Referring to FIG. 2, at time t0 when throttle valve 6 is fully closed (throttle opening = 0), the throttle fully closed signal is activated. If the engine speed is equal to or greater than the reference value Nth during the active period of the throttle fully closed signal, the fuel cut condition is satisfied.

  When the fuel cut condition satisfaction flag is activated, the fuel cut is executed and the fuel injection from the fuel injection valve 21 is stopped at time t1 when the delay period Tfd set according to the flowchart shown in FIG. 3 has elapsed. The delay period Tfd can be determined as an elapsed time measured by a timer (not shown), or the number of fuel injections or the number of ignitions (that is, the number of elapsed cycles).

  Referring to FIG. 3, when the fuel cut condition is satisfied (when YES is determined in step S100), engine ECU 60 compares the vehicle speed at that time with reference value Vth in step S110. For example, in step S110, the reference value Vth is set near zero so that the running state and the stopped state can be distinguished.

  In the traveling state (when YES is determined in step S110), the engine ECU 60 ensures the delay period Tfd in step S120 in consideration of the fact that the deceleration shock does not increase due to the rapid fuel cut.

  On the other hand, when the vehicle is stopped (when YES is determined in step S110), if the delay period is ensured to be equal to that in the running state with a relatively high engine speed such as after racing, a light load state exceeding the combustion limit. This may lead to misfire (light load misfire) in the combustion chamber before the fuel cut. If such a misfire in the combustion chamber is caused, unburned fuel is discharged to the catalyst in the period from the misfire until the fuel cut starts, so that after the fuel cut starts, the unburned fuel residue and air react in the catalyst. This may cause an excessively high temperature.

  Therefore, the engine ECU 60 sets the delay period Tfd to T2 that is shorter than that in the traveling state when the vehicle is stopped. In the running state, since there is a low possibility of a light load state exceeding the combustion limit even at a high speed, the possibility of misfire in the combustion chamber is low even if the delay period Tfd is secured.

  On the other hand, when the fuel cut condition is not satisfied (when NO is determined in step S100), it is not necessary to set the delay period in the fuel cut, and thus the delay setting process is terminated without executing steps S110 to S130.

  As described above, in the embodiment of the present invention, the delay period until the fuel cut is started when the fuel cut condition is satisfied is variably set according to the vehicle speed. This avoids the occurrence of decelerating shock, which is a problem when the delay period is too short, and the occurrence of a catalyst temperature increase due to misfire in the combustion chamber, which is a problem when the delay period is too long. The delay period can be set appropriately according to the situation (vehicle speed).

  In the present embodiment, an example is shown in which the delay period Tfd is set by distinguishing between the stopped state and the traveling state. However, the delay period may be set more finely by subdividing the vehicle speed classification. Alternatively, the delay period can be variably set according to operating conditions other than the vehicle speed (for example, engine speed) or according to a combination of the vehicle speed and other operating conditions.

  In the embodiment of the present invention, the fuel cut in the engine having the fuel injection valve for intake passage injection is exemplified. However, the application of the present invention is not limited to the arrangement form of the fuel injection valve. Absent. That is, the invention of the present application is commonly applied to an engine that performs fuel cut, such as an engine having a fuel injection valve for in-cylinder direct injection and an engine having both fuel injection valves for intake manifold injection and direct injection in cylinder Is applicable.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic configuration diagram of an engine system controlled by an engine ECU which is a control device for an internal combustion engine according to an embodiment of the present invention. It is an operation | movement waveform diagram explaining the control action at the time of the start of a fuel cut. It is a flowchart explaining the delay setting control in the fuel cut control by embodiment of this invention.

Explanation of symbols

2 Air cleaner, 3 Intake air temperature sensor, 4 Air flow meter, 5 Throttle body, 6 Throttle valve, 7 Idle adjustment circuit, 8 Idle speed control valve (ISCV), 9 Throttle opening sensor, 10 Idle switch, 12 Vacuum sensor, 13 Intake air Pipe, 15 Fuel tank, 17 Fuel pump, 19 Fuel pipe, 21 Fuel injection valve, 23 Intake valve, 24 Exhaust valve, 27 Exhaust manifold, 29 Exhaust pipe, 31 O ₂ sensor, 33 Catalytic converter, 43 Ignition distributor, 45, 47 Crank angle sensor, 49 Cooling water passage, 51 Water temperature sensor, 60 Engine ECU, 100 Engine (cylinder), Nth reference value (fuel cut condition regarding engine speed), Tfd Fuel cut delay period, Vth reference value (vehicle speed).

Claims (4)

A control device for an internal combustion engine capable of executing a fuel cut to stop fuel supply to the internal combustion engine when a predetermined operating condition is satisfied,
Detecting means for detecting establishment of the predetermined operating condition;
A delay period setting means for setting a delay period from the time when the driving condition is satisfied to the start of the fuel cut according to the vehicle speed at the time when the detection means detects that the predetermined driving condition is satisfied. When,
A control apparatus for an internal combustion engine, comprising: fuel cut start means for starting the fuel cut from a time point when a delay period set by the delay period setting means from a time point when the predetermined operating condition is established by the detection means.   The delay period setting means sets the delay period to the first period when the vehicle speed is higher than the reference speed, and sets the delay period to be higher than the first period when the vehicle speed is equal to or lower than the reference speed. The control device for an internal combustion engine according to claim 1, wherein the control device is set to a short second period.   The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the reference speed is set to a value for determining whether or not the vehicle is stopped.   The detection means satisfies the predetermined operating condition when a fully closed state of a throttle valve that adjusts an intake air amount to the internal combustion engine is detected and the rotational speed of the internal combustion engine is equal to or greater than a predetermined value. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein

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