JP2010242596A - Control device for internal combustion engine - Google Patents

Abstract

A control device for an internal combustion engine capable of appropriately releasing oxygen from a three-way catalyst at the time of starting the engine even when a power mode is selected.
An electronic control unit (22) is a mode for determining a control characteristic of a throttle valve (15) with respect to an accelerator operation amount. A normal mode and the control characteristic of the control characteristic so that a throttle opening is larger than that in the normal mode. A set power mode is provided. Further, the electronic control unit 22 increases the fuel injection amount at the time of starting the engine so that the air-fuel ratio is temporarily rich so that the oxygen stored in the three-way catalyst 21 for exhaust purification is released while the engine is stopped. Yes. Even when the power mode is set, the electronic control unit 22 controls the throttle valve 15 with the control characteristics of the normal mode until a specified time elapses after the engine is started.
[Selection] Figure 1

Description

  According to the present invention, as a mode for determining the control characteristic of the throttle valve with respect to the accelerator operation amount, a normal mode and a power mode in which the control characteristic is set so that the throttle opening is larger than that in the normal mode. The present invention relates to a control device for an internal combustion engine that increases the fuel injection amount at the time of starting the engine so that the air-fuel ratio is temporarily rich to release oxygen stored in a three-way catalyst for exhaust purification while the engine is stopped.

  In a vehicle, a power mode may be set in order to satisfy a high driving force requirement of the driver. In such a vehicle, when the driver selects the power mode, the driving characteristics of the vehicle are changed to increase the driving force. The power mode includes a mode in which the drive characteristic of the vehicle is changed by changing the shift characteristic of the transmission and a mode in which the drive characteristic of the vehicle is changed by changing the output characteristic of the internal combustion engine. In the latter case, as a mode for determining the control characteristic of the throttle valve with respect to the accelerator operation amount, a normal mode and a power mode in which the control characteristic is set so that the throttle opening is larger than that in the normal mode. Will be set. Conventionally, as a control device for an internal combustion engine in which the normal mode and the power mode are set, for example, a device described in Patent Document 1 is known.

  On the other hand, in an internal combustion engine mounted on a vehicle that uses gasoline or the like as a fuel, a three-way catalyst is provided in the exhaust passage, and the air-fuel ratio of air and fuel combusted in the combustion chamber of the engine is theoretically calculated. By controlling to the air-fuel ratio, the three-way catalyst appropriately purifies the three components of HC, CO, and NOx in the exhaust. When the three-way catalyst is exposed to air in an activated state while the internal combustion engine is stopped, the three-way catalyst occludes oxygen. Therefore, if the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber at engine start is controlled to the stoichiometric air-fuel ratio, the exhaust gas passes through the catalyst in a state where the oxygen concentration in the three-way catalyst is high, and NOx purification can be achieved. It becomes difficult. Therefore, when the engine is started, the amount of fuel is increased by a predetermined amount and the air-fuel ratio of the mixture is controlled to a predetermined low air-fuel ratio lower than the stoichiometric air-fuel ratio, thereby reducing the oxygen concentration of the exhaust gas. Thus, oxygen stored in the three-way catalyst is released into the exhaust gas.

JP 2007-091073 A

  By the way, in an internal combustion engine in which the control characteristic of the throttle valve can be switched with respect to the accelerator operation amount, even when a three-way catalyst is provided in the exhaust passage, the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber when the engine is started is more than the stoichiometric air-fuel ratio. Also, it is necessary to control to a rich predetermined low air-fuel ratio.

  Here, when the normal mode is selected at the time of starting the engine, the amount of fuel supplied to the combustion chamber is increased by a predetermined amount, so that the air-fuel ratio at the time of starting becomes a predetermined low air-fuel ratio. . On the other hand, when the power mode is selected in the internal combustion engine, the amount of fuel and air supplied to the combustion chamber is increased so that an engine output higher than the original engine output corresponding to the accelerator operation amount can be obtained. . Therefore, when the power mode is set when the engine is started, even if the amount of fuel supplied to the combustion chamber is increased by the predetermined amount, which is the same as the normal mode, the air-fuel ratio of the mixture is set to a predetermined value suitable for starting the engine. Therefore, it is impossible to achieve a low air-fuel ratio. For this reason, the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber becomes higher than the predetermined low air-fuel ratio, and oxygen cannot be released appropriately from the three-way catalyst. There may be a situation in which NOx purification cannot be achieved through the catalyst.

  The present invention has been made in view of such circumstances, and the problem to be solved is an internal combustion engine that can appropriately release oxygen from a three-way catalyst when the engine is started even when the power mode is selected. It is to provide a control device.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
In order to solve the above-mentioned problem, the invention according to claim 1 is a mode for determining the control characteristic of the throttle valve with respect to the accelerator operation amount so that the throttle opening is larger than the normal mode and the normal mode. And the power mode in which the control characteristics are set, and by increasing the fuel injection amount at the time of starting the engine, the air-fuel ratio is temporarily made rich and stored in the three-way catalyst for exhaust purification while the engine is stopped. The gist of the control device for an internal combustion engine that releases oxygen is that the throttle valve is controlled with the control characteristics of the normal mode until a specified time elapses after the engine is started even when the power mode is set. .

  In the above configuration, two modes of the normal mode and the power mode are set as modes for determining the control characteristics of the throttle valve with respect to the accelerator operation amount. In the power mode, the throttle valve control characteristics are set so that the throttle opening is larger than in the normal mode, and even with the same accelerator operation amount, a larger engine output than in the normal mode can be obtained. ing.

  In the above configuration, the fuel injection amount is increased when the engine is started, so that the air-fuel ratio is temporarily made rich so that the oxygen stored in the three-way catalyst for exhaust purification is released while the engine is stopped. If the throttle valve at this time is controlled by the control characteristics of the power mode, the throttle valve is opened more widely than in the normal mode so that the amount of air and fuel supplied to the combustion chamber is increased. Become. For this reason, even if the fuel injection amount at the time of starting the engine is increased by the same amount as that in the normal mode, the ratio of the fuel injection amount increase is reduced, and the air-fuel ratio cannot be sufficiently enriched. There is a possibility that oxygen stored in the original catalyst cannot be released satisfactorily.

  In that respect, in the above configuration, even when the power mode is set, the throttle valve is controlled with the control characteristics of the normal mode until a specified time has elapsed since the engine start. That is, the throttle control in the power mode is temporarily disabled until a specified time has elapsed since the engine was started. Therefore, it becomes possible to suitably enrich the air-fuel ratio by increasing the fuel injection amount when starting the engine. Therefore, according to the above configuration, even when the power mode is selected, oxygen can be appropriately released from the three-way catalyst when the engine is started.

  By the way, the release of the oxygen stored in the catalyst due to the increase in the fuel injection amount at the time of starting the engine as described above becomes meaningless unless the three-way catalyst is activated. That is, if the three-way catalyst is inactive, oxygen storage during engine stoppage does not occur so much, and even if the oxygen stored in the catalyst can be released before the three-way catalyst is activated, the catalyst is sufficiently warmed up. Until the catalyst is activated, the exhaust gas purifying action of the catalyst cannot be obtained.

  On the other hand, in recent years, vehicles that automatically execute an idling stop when the vehicle is stopped and hybrid vehicles having two drive sources of an internal combustion engine and a motor have been put into practical use. In these vehicles, the internal combustion engine is often intermittently stopped during a trip. May be. When the engine is started from such an intermittent stop state, the stop period of the internal combustion engine is short, and thus the internal combustion engine is started in a state where the active state of the three-way catalyst is maintained. Therefore, as described in claim 2, the control of the throttle valve with the control characteristics of the normal mode at the time of setting the power mode as described above is performed only when the engine is started from the intermittent stop state of the internal combustion engine. If this is done, oxygen can be appropriately released from the three-way catalyst when the engine is started, but it is possible to avoid disabling the power mode that is unnecessary for that purpose.

  In addition, in a vehicle in which the internal combustion engine is intermittently stopped as described above, in addition to the case where the driver depresses the accelerator pedal, the internal combustion engine is automatically started due to insufficient charging of the battery or the like. The engine may be started. However, in cases other than those caused by depressing the accelerator pedal, the internal combustion engine after starting is in an idle state, and the throttle valve is set to a small opening, so that the fuel supplied to the combustion chamber in the power mode or in the normal mode There will be little difference in the amount of air. Therefore, as described in claim 3, the control of the throttle valve with the control characteristics of the normal mode at the time of setting the power mode as described above is limited to the time when the engine is started from the intermittent stop state according to the depression of the accelerator pedal. If implemented, it becomes possible to avoid invalidating the power mode, which is unnecessary for that purpose, while appropriately releasing oxygen from the three-way catalyst when the engine is started.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows typically the structure of the internal combustion engine to which the control apparatus of the internal combustion engine which concerns on one Embodiment of this invention is applied. The graph which shows the setting of the control characteristic of the throttle valve with respect to the amount of accelerator operation in the power mode and normal mode in the embodiment. The flowchart of the throttle control routine at the time of start employ | adopted for the embodiment.

Hereinafter, an embodiment of a control device for an internal combustion engine according to the present invention will be described with reference to FIGS.
FIG. 1 schematically shows the configuration of an internal combustion engine to which the present embodiment is applied. The internal combustion engine is mounted on a hybrid vehicle having two drive sources, the internal combustion engine and a motor.

  As shown in the figure, the internal combustion engine generally includes an intake passage 10, a combustion chamber 11, and an exhaust passage 12. An air cleaner 13 for purifying intake air, an air flow meter 14 for detecting the intake air amount, a throttle valve 15 for adjusting the intake air amount, and an injector 18 for injecting fuel are disposed in the intake passage 10 from upstream. The throttle valve 15 is driven by a throttle motor 16, and its opening is detected by a throttle sensor 17.

  On the other hand, the combustion chamber 11 is provided with a spark plug 19 for igniting a mixture of fuel and air supplied into the combustion chamber 11. The exhaust passage 12 is provided with an air-fuel ratio sensor 20 that detects the oxygen concentration of the exhaust, and a three-way catalyst 21 that purifies the exhaust.

  The electronic control unit 22 that controls the internal combustion engine includes a central processing unit (CPU) that performs various arithmetic processes related to engine control, a read-only memory (ROM) that stores programs and data for engine control, A random access memory (RAM) for temporarily storing CPU calculation results and sensor signals, and an input / output port (I / O) for exchanging signals with the outside are provided. Detection signals from various sensors including the air flow meter 14, the throttle sensor 17, and the air-fuel ratio sensor 20 are input to the electronic control unit 22. The electronic control unit 22 outputs a command signal to the throttle motor 16, the injector 18, the spark plug 19 and the like based on the detection signals of these sensors, thereby controlling the engine such as throttle control, fuel injection control, ignition timing control, etc. To implement.

  Note that this internal combustion engine is mounted on a hybrid vehicle, and the internal combustion engine is intermittently stopped when the power of the internal combustion engine is unnecessary, such as when the vehicle is driven only by a motor. Control relating to such intermittent pause of the internal combustion engine is also performed by the electronic control unit 22. The electronic control unit 22 also performs control to automatically start the internal combustion engine when the battery is insufficiently charged during intermittent pause.

  On the other hand, an accelerator sensor 23 for detecting an accelerator operation amount and a power switch 24 for switching between enabling and disabling of a power mode, which will be described later, are installed in a cab of a vehicle in which such an internal combustion engine is mounted. A detection signal from the accelerator sensor 23 and an ON / OFF signal from the power switch 24 are also input to the electronic control unit 22.

  In the control apparatus for an internal combustion engine of the present embodiment configured as described above, as a mode for determining the control characteristic of the throttle valve 15 with respect to the accelerator operation amount, the throttle opening is compared with the normal mode and the normal mode. And a power mode in which the control characteristics are set to be larger. FIG. 2 shows how the control characteristics of the throttle valve 15 are set with respect to the accelerator operation amount in the power mode and the normal mode. As shown in the figure, in the power mode, the throttle opening at the same accelerator operation amount is set larger than in the normal mode. The switching between the power mode and the normal mode is performed by the driver switching between valid and invalid of the power mode through the operation of the power switch 24.

  Further, in the present embodiment, the electronic control unit 22 increases the fuel injection amount and temporarily makes the air-fuel ratio rich when the engine is started from the intermittent stop state, so that the three-way catalyst 21 is stopped during the engine stop. The stored oxygen is released. If the throttle valve 15 at this time is controlled with the control characteristics of the power mode, the throttle valve 15 is opened more largely than in the normal mode, and the amount of air and fuel supplied to the combustion chamber 11 is further increased. Become so. For this reason, even if the fuel injection amount at the time of starting the engine is increased by the same amount as that in the normal mode, the ratio of the fuel injection amount increase is reduced, and the air-fuel ratio cannot be sufficiently enriched. There is a possibility that oxygen stored in the original catalyst cannot be released satisfactorily.

  Therefore, in the present embodiment, when the engine is started from the intermittently resting upper body corresponding to the depression of the accelerator pedal when the power mode is set, the power mode is temporarily changed until a specified time elapses after the engine is started. The throttle valve 15 is controlled by the normal mode control characteristics. Therefore, it becomes possible to suitably enrich the air-fuel ratio by increasing the fuel injection amount at the time of starting the engine, and even when the power mode is selected, oxygen is appropriately released from the three-way catalyst 21 at the time of starting the engine. Be able to.

  FIG. 3 shows a flowchart of a start time throttle control routine related to the throttle control at the time of engine start in such a mode. The processing of this routine is repeatedly performed periodically by the electronic control unit 22 during vehicle startup.

  When this routine is started, the electronic control unit 22 confirms whether or not the power switch 24 is “ON” in step S101. If the power switch 24 is “OFF” (S101: NO), since it is in the normal mode, the electronic control unit 22 proceeds to step S105, and in step S105, the throttle valve 15 is in the normal mode. The opening degree control is performed, and the process of this routine is terminated.

  On the other hand, if the power switch 24 is “ON” (S101: YES), the electronic control unit 22 normally proceeds to step S106, and in step S106, the opening degree control of the throttle valve 15 is performed in the power mode. Then, the process of this routine is finished. However, the electronic control unit 22 is currently starting the engine from the intermittent stop state (S102: YES), and the engine start is due to depression of the accelerator pedal (accelerator on) (S103: YES), and If the elapsed time after the start is less than the prescribed time α (S104: YES), the process proceeds to step S105. In step S105, the opening degree control of the throttle valve 15 is performed in the normal mode, and this routine is performed. Terminate the process. That is, at this time, the power mode is temporarily invalidated.

According to this embodiment described above, the following effects can be obtained.
(1) In the present embodiment, the electronic control unit 22 is a mode for determining the control characteristic of the throttle valve 15 with respect to the accelerator operation amount so that the throttle opening is larger than the normal mode and the normal mode. A power mode in which the control characteristics are set is provided. Further, the electronic control unit 22 increases the fuel injection amount at the time of starting the engine so that the air-fuel ratio is temporarily rich so that the oxygen stored in the three-way catalyst 21 for exhaust purification is released while the engine is stopped. Yes. In the present embodiment, even when the power mode is set, the electronic control unit 22 controls the throttle valve 15 with the control characteristics of the normal mode until a specified time α elapses after the engine is started. . That is, in the present embodiment, the throttle control in the power mode is temporarily invalidated until a predetermined time α elapses after the engine is started. Therefore, it becomes possible to suitably enrich the air-fuel ratio by increasing the fuel injection amount at the time of starting the engine, and even when the power mode is selected, oxygen is appropriately released from the three-way catalyst 21 at the time of starting the engine. Will be able to.

  (2) In the present embodiment, the control of the throttle valve 15 with the control characteristics of the normal mode when the power mode is set is performed only when the engine is started from the intermittent stop state of the internal combustion engine. If the three-way catalyst 21 is inactive, oxygen storage during the engine stop does not occur so much, and even if the oxygen stored in the catalyst can be released before the three-way catalyst 21 is activated, the catalyst is sufficiently warmed up. Until the catalyst is activated, the exhaust gas purifying action of the catalyst cannot be obtained. On the other hand, when the engine is started from the intermittent resting state, the resting period of the internal combustion engine is short, so that the internal combustion engine is started in a state where the active state of the three-way catalyst 21 is maintained. Therefore, if the control of the throttle valve with the control characteristics of the normal mode at the time of setting the power mode as described above is performed only when the engine is started from the intermittent stop state of the internal combustion engine, the three-way catalyst is While properly releasing oxygen from 21, it is possible to avoid disabling the power mode that is unnecessary for that purpose.

  (3) In the present embodiment, the control of the throttle valve 15 with the control characteristics of the normal mode at the time of setting the power mode is performed only when the engine is started according to the depression of the accelerator pedal from the intermittent stop state. . In a vehicle in which the internal combustion engine is intermittently stopped, the engine is started from the intermittent stop state not only by the driver's depression of the accelerator pedal but also by the automatic start of the internal combustion engine due to insufficient charging of the battery or the like. Sometimes. However, in cases other than those caused by depression of the accelerator pedal, the internal combustion engine after starting is in an idle state, and the throttle valve 15 is set to a small opening, so that it is supplied to the combustion chamber 11 in either the power mode or the normal mode. There is almost no difference in the amount of fuel and air. Therefore, if the control of the throttle valve 15 with the control characteristics of the normal mode at the time of setting the power mode as described above is performed only when the engine is started according to the depression of the accelerator pedal from the intermittent stop state, the engine While properly releasing oxygen from the three-way catalyst 21 at the time of starting, it is possible to avoid invalidating the power mode that is unnecessary for that purpose.

The above embodiment can also be implemented with the following modifications.
In the above embodiment, the control of the throttle valve 15 with the control characteristics of the normal mode when the power mode is set, that is, the power mode is temporarily disabled only when the engine is started from the intermittent stop state according to the depression of the accelerator pedal. We are trying to implement. However, even if the opening is small, if there is a significant difference in the throttle opening between the power mode and the normal mode, the normal mode when the power mode is set even when the internal combustion engine is automatically started due to insufficient battery charge, etc. The throttle valve 15 may be controlled with the above control characteristics.

  In the above embodiment, only when the engine is started from the intermittent stop state, the control of the throttle valve 15 with the control characteristics of the normal mode when the power mode is set, that is, the power mode is temporarily invalidated. Yes. However, if the stored oxygen of the three-way catalyst 21 is released by increasing the fuel injection amount even when the engine other than that in the intermittent stop state is started, the normal mode at the time of setting the power mode is also used when starting the engine. The throttle valve 15 may be controlled with the above control characteristics.

  In the above embodiment, the power switch 24 can be switched between the power mode and the normal mode by operating the power switch 24. However, the power request of the driver is determined from the operation state of the accelerator pedal, and the power mode is automatically set. Can also be set. In this case as well, even when the power mode is set, the three-way catalyst 21 can be used when the engine is started if the throttle valve 15 is controlled with the control characteristics of the normal mode until a specified time elapses after the engine is started. Oxygen can be appropriately released from the water.

  In the above-described embodiment, the case where the internal combustion engine mounted on the hybrid vehicle is controlled is described. However, the present invention can also be applied to internal combustion engines other than those mounted on the hybrid vehicle. Application of an internal combustion engine that implements intermittent pause is suitable.

  DESCRIPTION OF SYMBOLS 10 ... Intake passage, 11 ... Combustion chamber, 12 ... Exhaust passage, 13 ... Air cleaner, 14 ... Air flow meter, 15 ... Throttle valve, 16 ... Throttle motor, 17 ... Throttle sensor, 18 ... Injector, 19 ... Spark plug, 20 Air-fuel ratio sensor, 21 Three-way catalyst, 22 Electronic control unit, 23 Accelerator sensor, 24 Power switch.

Claims (3)

As a mode for determining the control characteristic of the throttle valve with respect to the accelerator operation amount, it has a normal mode and a power mode in which the control characteristic is set so that the throttle opening is larger than that in the normal mode, In a control device for an internal combustion engine that temporarily enriches the air-fuel ratio by increasing the fuel injection amount at the start and releases the oxygen stored in the three-way catalyst for exhaust purification while the engine is stopped.
A control apparatus for an internal combustion engine, wherein the throttle valve is controlled with control characteristics of a normal mode until a specified time elapses after the engine is started even when the power mode is set. The control device for an internal combustion engine according to claim 1, wherein the control of the throttle valve with the control characteristics of the normal mode at the time of setting the power mode is performed only when the engine is started from an intermittent stop state of the internal combustion engine. 2. The internal combustion engine according to claim 1, wherein the control of the throttle valve with the control characteristics of the normal mode when the power mode is set is performed only when the engine is started from an intermittent stop state in response to depression of an accelerator pedal. Control device.

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