JP2007239482A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve startability, fuel economy and an exhaust emission composition in a vehicle including an operation mode temporarily stopping an internal combustion engine such as a hybrid vehicle. <P>SOLUTION: An air-fuel ratio range determination means determining whether an output from an air fuel-ratio sensor is in a predetermined air fuel ratio range at the restart of the internal combustion engine by motoring is provided. Air-fuel ratio feedback control is started under a condition that an output from the air-fuel ratio sensor is in the predetermined air fuel ratio range after the restart. Consequently, startability at the restart, operability, fuel economy and exhaust emission performance after a start can be improved since feedback control is started at an early stage only when an air fuel-ratio range is appropriate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air-fuel ratio control apparatus for an internal combustion engine, and more particularly to an improvement of an air-fuel ratio control apparatus suitable for a vehicle having an operating condition for temporarily stopping the internal combustion engine during traveling.

  In general, an internal combustion engine for a vehicle includes an air-fuel ratio control device that feedback-controls a fuel supply amount so that a target air-fuel ratio is obtained based on a signal from an exhaust air-fuel ratio sensor. As a problem when such an internal combustion engine is mounted on a vehicle having an operating condition for temporarily stopping the internal combustion engine while traveling, such as a hybrid vehicle or an idle stop vehicle, the engine is idle while the internal combustion engine is stopped. It is pointed out that the air-fuel ratio control cannot be started immediately upon restart because the activity of the fuel ratio sensor is reduced.

As a countermeasure, Patent Document 1 discloses that the air-fuel ratio control can be started early after restarting by operating the heater of the air-fuel ratio sensor in the same manner as during operation even when the engine is stopped. . Further, in the one disclosed in Patent Document 2, the air-fuel ratio control is started early after restarting while setting the heater current of the air-fuel ratio sensor to be lower than that during operation while the internal combustion engine is stopped, and suppressing the consumption current. I can do it.
JP-A-9-88688 JP 2003-148206 A

  A hybrid vehicle has an operation mode in which the internal combustion engine is stopped not only when the internal combustion engine is idling or when the vehicle is stopped, but also when the vehicle is running. In such an operation mode, a driving force is generated. In order to smoothly switch power to and from the electric motor, it is necessary to generate power more quickly at the time of restart.For this reason, the motoring operation restarts at a higher speed than at the cold start. I'm going to go to complete explosion.

  However, if air-fuel ratio feedback control is started early regardless of such motoring, it is necessary to supply a large amount of fuel before the complete explosion during motoring. May get worse.

  The present invention provides an operation control device for temporarily stopping the operation of an internal combustion engine according to a running condition of a vehicle, and feedback control of a fuel supply amount so that a target air-fuel ratio is obtained based on a signal from an exhaust air-fuel ratio sensor An air-fuel ratio control device that performs a complete explosion at high speed by motoring when the internal combustion engine is restarted from the temporarily stopped state. It is a control device.

  In the present invention, after the restart of the internal combustion engine, air-fuel ratio range determination means for determining whether or not the output from the air-fuel ratio sensor is within a predetermined air-fuel ratio range is provided. The air-fuel ratio control apparatus is configured to start air-fuel ratio feedback control on condition that the output from the sensor is within a predetermined air-fuel ratio range.

  According to the present invention, the actual air-fuel ratio is within the predetermined allowable range, that is, the air-fuel ratio feedback control is started even under the motoring condition where the smaller air-fuel ratio is applied outside the control target value. However, air-fuel ratio feedback control is not started until it falls within the acceptable range, so air-fuel ratio feedback control is performed during motoring, and there is no possibility of deterioration in combustibility and startability, and after restart as much as possible Since air-fuel ratio feedback control can be started at an early stage, the startability, fuel consumption, and exhaust composition can be improved in a vehicle having an operation mode in which the internal combustion engine is temporarily stopped, such as a hybrid vehicle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an engine system diagram showing an embodiment of the present invention.

  A throttle valve 3 is interposed in the intake passage 2 of the internal combustion engine 1 in the middle thereof. The fuel is supplied by a fuel injection valve 4 provided for each cylinder.

  The evaporative fuel processing apparatus is provided with a canister 7 that guides the evaporative fuel generated in the fuel tank 5 through the evaporative fuel introduction passage 6 and temporarily adsorbs it. The canister 7 is a container filled with an adsorbent 8 such as activated carbon.

  The canister 7 is formed with a fresh air inlet (atmospheric opening) 9 and a purge passage 10 is led out. The purge passage 10 is connected to the intake passage 2 downstream of the throttle valve 3 via the purge valve 11. The purge valve 11 is opened by a signal output from an engine control unit (hereinafter referred to as ECU) 20. Reference numeral 12 is an exhaust passage, 13 is a catalytic converter interposed in the middle, and 14 is an air-fuel ratio sensor that is located upstream of the catalytic converter 13 and detects an exhaust air-fuel ratio.

  The evaporated fuel generated in the fuel tank 5 while the internal combustion engine 1 is stopped is guided to the canister 7 by the evaporated fuel introduction passage 6 and adsorbed thereto. When the internal combustion engine 1 is started and a predetermined purge permission condition is satisfied, the purge valve 11 is opened, and the intake negative pressure of the internal combustion engine 1 acts on the canister 7, so that fresh air introduced from the fresh air inlet 9 is obtained. The vaporized fuel adsorbed by the canister 7 is desorbed by this, and the purge gas containing the desorbed vaporized fuel is sucked into the intake manifold 4 through the purge passage 10 and then burned in the combustion chamber of the internal combustion engine 1. It is processed.

  The ECU 20 is composed of a microcomputer comprising a CPU and its peripheral devices, and an operation control device that temporarily stops the operation of the internal combustion engine 1 in accordance with the running conditions of the vehicle, and a signal from the exhaust air-fuel ratio sensor 14. Is provided with a function as an air-fuel ratio control device that feedback-controls the fuel supply amount so that the target air-fuel ratio can be obtained based on the above. As a basic control operation as the operation control device, the ECU 20 causes the motoring to complete the explosion at a higher speed than the cold start by motoring when the internal combustion engine 1 is restarted from the temporarily stopped state. It is configured as follows. As the air-fuel ratio control device, the air-fuel ratio signal from the exhaust air-fuel ratio sensor 14 and the operation state signals such as the engine speed Ne, the intake air amount Qa, and the cooling water temperature Tw from other sensors (not shown) are input. Based on this, a fuel injection amount command value for the fuel injection device is output. Further, after the engine is restarted, air-fuel ratio feedback control is started on the condition that the output from the air-fuel ratio sensor 14 is within a predetermined air-fuel ratio range. That is, in relation to the present invention, the ECU 20 also has a function as air-fuel ratio range determination means for determining whether or not the output from the air-fuel ratio sensor 14 is within a predetermined air-fuel ratio range.

  As described above, the ECU 20 executes the stop or restart of the internal combustion engine 1 in accordance with the traveling condition of the vehicle. The control pattern of the operation or stop of the internal combustion engine in such hybrid vehicle control depends on the purpose and the specification. There are various variations depending on the situation. In general, the internal combustion engine is operated under a high-load running condition where the driving force is insufficient with a motor alone or under a condition that requires battery charging, and the internal combustion engine is controlled to stop under other conditions.

  FIG. 2 is a block diagram showing a control function portion of the ECU 20 during engine stop and restart. FIG. 3 (FIGS. 3-1 to 3-4) shows a cycle of the ECU 20 at regular intervals or by interruption processing. The control routine of the main part of the control to be executed automatically is represented by a flowchart. Hereinafter, the control of the ECU 20 when the engine is restarted will be described with reference to these drawings. In the following description and FIG. 3, the symbol S is a processing step number.

  In FIG. 2, reference numeral 101 denotes an air-fuel ratio control permission determination unit. The permission determination unit 101 basically has the air-fuel ratio sensor 14 (indicated as “A / F sensor” in the figure) activated, and the engine cooling water temperature is equal to or higher than a predetermined permission water temperature. In addition, the air-fuel ratio feedback control is permitted on the condition that a predetermined delay time has elapsed since the start of the start, and is not permitted if none of the above conditions is satisfied. This operation corresponds to S11 to S14 in FIG. 3-1, as a processing routine, and a permission flag indicating permission of air-fuel ratio feedback control is set when the condition is satisfied. As control functions, an activation condition determination unit 102, a water temperature condition determination unit 103, and a post-start delay condition determination unit 104 are provided for the determination. The activation condition determination unit 102 determines whether or not the air-fuel ratio sensor 14 is in an active state based on a known determination method, for example, that the sensor temperature is equal to or higher than a predetermined reference value. The water temperature condition determination unit 103 determines whether or not the engine cooling water temperature is equal to or higher than a predetermined permitted water temperature based on a signal from the cooling water temperature sensor. The post-startup delay condition determination unit 104 sets a delay time set in a table with characteristics that increase as the temperature decreases based on the engine coolant temperature when the starter motor is started at the start, and the delay time has elapsed. Whether or not is determined by a timer.

  The post-start-up delay time determination unit 104 is activated when the vehicle system is first activated by turning on the ignition switch, that is, at the start of operation. The hybrid traveling control includes a restart condition determining unit 200 including a function of determining a delay after starting when the internal combustion engine is temporarily stopped and then restarted. In FIG. 2, a portion surrounded by a broken line is the restart condition determination unit 200. The restart condition determination unit 200 mainly includes an early request determination unit 201, a second post-start delay condition determination unit 202, and an air-fuel ratio (indicated as “A / F” in the drawing) output range. The condition determination unit 203 is included.

  The early request determination unit 201 operates the signal switching unit 105 by determining the above-described temporarily stopped state of the internal combustion engine, and outputs the determination condition signal to the permission determination unit 101 as the first post-start delay condition. There is a function of switching to either the determination unit 104 or the restart condition determination unit including the second post-startup delay condition determination unit 202. This corresponds to S21 to 23 in FIG. For the above operation, the early request determination unit 201 includes a water temperature region request determination unit 201a and a sensor crack prevention request control unit 201b. The water temperature region request determination unit 201a determines whether or not the engine coolant temperature at the time of restart is within a water temperature region that is greater than or equal to a predetermined lower limit set value A and less than the upper limit set value B. The lower limit set value A is set to a water temperature that is higher than the permitted water temperature in the water temperature condition determination unit 103 and corresponds to a state in which the internal combustion engine has been warmed up. The sensor crack prevention request control unit 201b is assumed to perform control to supply current to the heater unit of the air-fuel ratio sensor 14 when the engine is restarted, and a predetermined delay time after the heater control is permitted and the sensor heating is started. Is set to wait for the temperature to rise to some extent in order to prevent the air-fuel ratio sensor 14 from being damaged. In this case, based on the engine coolant temperature at the start of the sensor heating, a delay time set in a table with characteristics that increase at lower temperatures is set, and a timer determines whether or not the delay time has elapsed. To do.

  In the early request determination unit 201, the engine coolant temperature is within the predetermined region and the predetermined delay time has elapsed in the sensor crack prevention request control unit 201b as determined by the water temperature region request determination unit 201a. If the restart condition determination unit side including the second post-start delay condition determination unit 202 is connected to the permission determination unit 101 on the condition that the signal switching unit 105 is not satisfied in any of the above conditions Connects the first post-start delay condition determination unit 104 to the permission determination unit 101.

  The second post-startup delay condition determination unit 202 sets a delay time set in a table with characteristics that increase at lower temperatures based on the engine coolant temperature during motoring (starter motor activation at restart). The timer determines whether the delay time has elapsed. This corresponds to S31 to S36 in FIG. 3-3 as a processing routine, and a condition satisfaction flag is set when the delay condition is satisfied. In relation to the present invention, the second delay condition determination unit 202 corresponds to a delay time setting unit.

  The air-fuel ratio output range condition determination unit 203 includes an air-fuel ratio output range determination unit 203a and a forced start determination unit 203b. The air-fuel ratio output range determination unit 203a determines whether the exhaust air-fuel ratio range is within a predetermined range as one of the air-fuel ratio feedback control start conditions after restart, and the forced start determination unit 203b Regardless of the case, the start of the air-fuel ratio feedback control is forcibly permitted when a certain time has elapsed since the restart. In relation to the present invention, the air-fuel ratio output range determination unit 203a corresponds to air-fuel ratio range determination means. Details will be described first from the forced start determination unit 203b. As a determination condition, the starter switch operation and the start of heater control of the air-fuel ratio sensor 14 are determined, and from these, the start of heater control for motoring or restart is determined. When either one is determined, the elapse of the predetermined time A is determined by the timer, and when the elapses, the start of the air-fuel ratio feedback control is permitted. This corresponds to S41 to S45 and S50 in FIG. 3-4 as a processing routine. When the permission condition is satisfied, a condition satisfaction flag is set. On the other hand, in the air-fuel ratio output range determination unit 203a, based on the output from the air-fuel ratio sensor 14, the exhaust air-fuel ratio at the time of restart is greater than or equal to a predetermined lower limit set value A and less than the upper limit set value B, and the state is predetermined Whether the exhaust air / fuel ratio is within the predetermined air / fuel ratio range is counted by a timer. When the exhaust air / fuel ratio remains within the predetermined air / fuel ratio range for a predetermined time or longer, permission flag processing is performed to permit air / fuel ratio feedback control. This corresponds to S46 to S50 in FIG. The permission flag is reset when the engine is stopped.

  The air-fuel ratio output range condition determination unit 203 outputs a permission signal when a condition satisfaction flag is set by the determination of either the air-fuel ratio output range determination unit 203a or the forced start determination unit 203b. At this time, if a condition satisfaction signal is also output from the second post-start delay condition determination unit, a permission signal is output to the permission determination unit 101. At this time, the air-fuel ratio sensor activation condition, the water temperature If both conditions are satisfied, air-fuel ratio feedback control is permitted. This operation corresponds to S23 to S25 in FIG.

  Based on the above control, when the air-fuel ratio range when the internal combustion engine is restarted from the temporarily stopped state during the hybrid control is within a predetermined range, the air-fuel ratio feedback control can be started promptly. It is possible to improve the startability at the time of restart by securing an opportunity to implement the fuel ratio feedback control at an early stage, and to improve the drivability, fuel consumption, exhaust performance, etc. of the internal combustion engine after the start. In this embodiment, the air-fuel ratio feedback control is forcibly started when a predetermined time has elapsed from the motoring during the restart. By performing this forced air-fuel ratio feedback control, even if the air-fuel ratio sensor 14 is out of order, this can be detected early.

  Further, in the internal combustion engine having the evaporative combustion processing apparatus as in this embodiment, the purge is performed early after the start of the air-fuel ratio feedback control by configuring the purge after the start of the air-fuel ratio feedback control. The amount of purge can be increased by starting, and the evaporated fuel can be processed efficiently.

1 is a system diagram showing an embodiment of the present invention. The block diagram showing the control function of an embodiment. The 1st flowchart showing the control contents of an embodiment. The 2nd flowchart showing the control contents of an embodiment. The 3rd flowchart showing the control contents of an embodiment. The 4th flowchart showing the control contents of an embodiment.

Explanation of symbols

1 Internal combustion engine 2 Air cleaner 3 Throttle valve 4 Fuel injection valve 5 Fuel tank 7 Canister 12 Exhaust passage 13 Catalytic converter 14 Exhaust air / fuel ratio sensor 20 ECU
101 permission determination unit 102 air-fuel ratio sensor activation condition determination unit 103 water temperature condition determination unit 104 first post-startup delay condition determination unit 105 output switching unit 200 restart condition determination unit 201 early request determination unit 202 after second start-up Delay condition judgment unit (delay time setting means)
203 Air-fuel ratio output range condition determination unit (air-fuel ratio range determination means)

Claims (5)

An operation control device that temporarily stops the operation of the internal combustion engine according to the running condition of the vehicle, and an air-fuel ratio control device that feedback-controls the fuel supply amount so that the target air-fuel ratio is obtained based on a signal from the air-fuel ratio sensor In the control device for an internal combustion engine configured to cause a complete explosion at high speed rotation by motoring when the internal combustion engine is restarted from the temporarily stopped state,
Air-fuel ratio range determining means for determining whether the output from the air-fuel ratio sensor is within a predetermined air-fuel ratio range after the restart of the internal combustion engine;
After the restart, the air-fuel ratio control device is configured to start the air-fuel ratio feedback control on condition that the output from the air-fuel ratio sensor is within a predetermined air-fuel ratio range. Control device.   The air-fuel ratio range determining means is configured to determine that the exhaust air-fuel ratio is within the air-fuel ratio range when the predetermined air-fuel ratio range continues for a predetermined time or longer. The internal combustion engine control device described.   2. The control device for an internal combustion engine according to claim 1, wherein the air-fuel ratio control device is configured to start air-fuel ratio feedback control after a predetermined time has elapsed after restart regardless of a determination result of the air-fuel ratio sensor range. . The internal combustion engine includes an evaporative fuel processing device that guides the evaporated fuel from the fuel tank to the canister, temporarily adsorbs the evaporated fuel, and sucks the evaporated fuel adsorbed by the canister into the intake passage of the internal combustion engine together with fresh air.
2. The control device for an internal combustion engine according to claim 1, wherein the evaporated fuel processing device is configured to perform a purge after the start of the air-fuel ratio feedback control after the restart.   2. The internal combustion engine according to claim 1, which is configured to detect that the air-fuel ratio sensor is in an active state and that the cooling water temperature of the internal combustion engine is equal to or higher than a predetermined reference value as permission conditions for the air-fuel ratio feedback control. Engine control device.

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