JP6214214B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine mounted on a vehicle.

  In an internal combustion engine mounted on a vehicle, it is known to perform a fuel cut that interrupts fuel injection in accordance with the operation state (see, for example, Patent Document 1 below). Normally, when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed, the fuel cut is started assuming that the fuel cut condition is satisfied. Then, when any fuel cut end condition is satisfied, such as when the accelerator pedal depression amount exceeds the threshold value, or the engine speed decreases to the fuel cut return speed, the fuel cut ends and the fuel injection resumes. .

  Recently, it has also become common to implement an idle stop that stops the idle rotation of the internal combustion engine while the vehicle is stopped due to a signal waiting or the like (see, for example, Patent Document 2 below). In the known idling stop system, the internal combustion engine is stopped when various conditions such as the vehicle speed is lower than a predetermined value, the brake pedal is depressed, and the coolant temperature and the battery voltage are sufficiently high are satisfied. After the idling stop, the internal combustion engine is restarted when there is a restart request such as the driver removing his foot from the brake pedal or depressing the accelerator pedal.

  When the driver removes his or her foot from the accelerator pedal while the vehicle is running and the vehicle decelerates and stops, first the fuel cut condition is satisfied and the fuel cut is started, and then the engine shifts to idle stop. However, it does not mean that no fuel is injected between the start of fuel cut and the idle stop. Actually, the fuel cut end condition is satisfied when the vehicle speed of the vehicle drops to about 10 km / h, and fuel injection and ignition combustion are temporarily resumed. Then, the idle stop condition is established at a vehicle speed of about 9 km / h, and the fuel injection is stopped again, whereby the internal combustion engine and the vehicle are further decelerated, leading to an idle stop and a stop.

Japanese Patent Laid-Open No. 10-030477 JP 2012-137018 A

  Temporary fuel injection that occurs between the fuel cut and idle stop is a factor that deteriorates the effective fuel consumption. Therefore, the vehicle speed condition, which is one of the idle stop conditions, is raised. For example, when the vehicle speed is 13 km / h or less (assuming that other conditions are satisfied), the fuel cut is performed by permitting the idle stop. It is conceivable to consistently continue from to idle stop.

However, during a fuel cut in which the internal combustion engine rotates by inertia without fuel injection, air that does not contain a fuel component flows into the exhaust purification catalyst from the cylinder via the exhaust passage. As a result, a large amount of oxygen is occluded in the catalyst, and the ability of the catalyst to reduce NO _x decreases. When enters the idle stop remains in such a state, there is a concern that emissions of restart time on the NO _x subsequent engine increases.

The present invention, while achieving the further improvement of fuel economy, the intended purpose of suppressing the emission of the NO _x in the restart after idle stop of the internal combustion engine.

In order to solve the above-described problems, in the present invention, a fuel cut that temporarily stops fuel injection is performed when a predetermined fuel cut condition is satisfied, and idle rotation of the internal combustion engine is performed when a predetermined idle stop condition is satisfied. Idle stop to be stopped, the length of the period from the end of the fuel cut to the start of the idle stop is counted, and the internal combustion engine that has been idle stopped is restarted according to the length of the counted period The control device for the internal combustion engine is characterized in that the fuel injection amount at the time of changing is changed. When the idle stop condition is satisfied before the fuel cut end condition is satisfied and the fuel cut continuously shifts to the idle stop, the “length of the period from the end of the fuel cut to the start of the idle stop” is 0. Become.

When the idling stop is started after the fuel cut is once ended, the amount of oxygen stored in the catalyst is reduced by temporarily resuming the fuel injection between the fuel cut and the idling stop. If the period from the end of the fuel cut to the start of the idle stop is long, the NO _x emission amount at the restart after the idle stop does not increase particularly.

On the other hand, if the period is short or zero, there is a high possibility that the NO _x emission amount increases in the restart after the idle stop. Therefore, by increasing the fuel injection amount at the time of restart, the air-fuel ratio of the gas flowing into the catalyst is enriched, and the NO _x reduction reaction in the catalyst is promoted.

If the length of the period from the completion of the fuel cut and the start of the idle stop is the predetermined or less or 0, and increasing the fuel injection amount at the time of restarting the internal combustion engine as compared with the case not, the former If the fuel injection amount increment in this case is determined according to the length of the fuel cut period before the idle stop, the restart of the fuel injection amount according to the amount of oxygen that flows into the catalyst and is stored in the catalyst during the fuel cut. The fuel injection amount at the time is increased, and the increase in the NOx emission amount at the restart after the idle stop can be more reliably suppressed.

According to the present invention, while achieving the further improvement of fuel economy, emissions of the NO _x in the restart after idle stop can be suppressed.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The flowchart which shows the example of the procedure of the process which the control apparatus of the internal combustion engine of the embodiment implements.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition type four-stroke engine and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  An ECU (Electronic Control Unit) 0 that is a control device of the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. An accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (engine output required by the driver, so-called required load), and output from a sensor that detects the amount of depression of the brake pedal Indicating the brake pedaling amount signal d, the intake air temperature / intake pressure signal e output from the temperature / pressure sensor for detecting the intake air temperature and the intake pressure in the intake passage 3 (particularly, the surge tank 33), and the temperature of the internal combustion engine The coolant temperature signal f output from the coolant temperature sensor that detects the coolant temperature to be detected, the intake camshaft or the exhaust camshaft A cam angle signal g outputted by the cam angle from the cam angle sensor, battery status signal h or the like to be output from the sensor for detecting the battery current and the battery temperature suggesting the state of charge of the vehicle battery is input.

  From the output interface, an ignition signal i is output to the igniter of the spark plug 12, a fuel injection signal j is output to the injector 11, an opening operation signal k is output to the throttle valve 32, and the like.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, the intake air amount, and the like, various operating parameters such as required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, and ignition timing are determined. The ECU 0 applies various control signals i, j, k corresponding to the operation parameters via the output interface.

  Further, the ECU 0 inputs a control signal o to the electric motor (starter motor or motor generator) when the internal combustion engine is started (a cold start or a return from an idling stop). Cranking is performed by rotating the crankshaft. Cranking ends when the internal combustion engine starts from the first explosion to a continuous explosion and the engine speed, that is, the rotation speed of the crankshaft, exceeds a judgment value determined according to the coolant temperature, etc. (assuming that the explosion has been completed) To do.

  The ECU 0 of the present embodiment executes a fuel cut that interrupts the fuel supply to the cylinder 1 in accordance with the driving situation. In addition, the ECU 0 also performs an idle stop for stopping the idle rotation of the internal combustion engine when the vehicle stops due to a signal waiting or the like.

  FIG. 2 shows a procedure example of processing executed by the ECU 0 when the vehicle decelerates and stops. When a predetermined fuel cut condition is satisfied (step S1), the ECU 0 stops fuel cut, that is, fuel injection from the injector 11 (step S2). In step S1, it is determined that the fuel cut condition is satisfied, at least when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed.

  However, even if the fuel cut condition is satisfied, the fuel injection is not stopped immediately. If the fuel supply is cut off suddenly when the engine torque is relatively large, a torque shock that causes the engine speed and the vehicle speed to drop stepwise occurs, causing the passengers including the driver to feel the shock. In order to reduce the torque shock, the fuel injection is stopped only after the elapse of the delay time after the fuel cut condition is satisfied. During this delay time, the ignition timing is retarded and the engine torque is actively reduced.

  When a predetermined fuel cut end condition is satisfied after the start of fuel cut and before an idle stop condition described later is satisfied (step S4), the fuel cut is ended and fuel injection (and ignition) is resumed. (Step S5). In step S4, it is determined that the fuel cut end condition is satisfied, for example, when the accelerator pedal depression amount exceeds the threshold value or the engine speed has decreased to the fuel cut return speed.

  Further, when a predetermined idle stop condition is satisfied (steps S7 and S8), the ECU 0 executes an idle stop that stops the idle rotation of the internal combustion engine (step S9). In Steps S7 and S8, all conditions were met such that the vehicle speed was below a predetermined value (for example, a value of 10 km / h to 13 km / h), the brake pedal was depressed, and the coolant temperature and battery voltage were sufficiently high. Therefore, it is determined that the idle stop condition is satisfied.

  If the idle stop condition is satisfied without satisfying the fuel cut end condition after the start of the fuel cut (step S8), the fuel injection is not resumed and the state is shifted to the idle stop with the fuel cut state (step S9). . If the vehicle speed condition, which is one of the idle stop conditions, is increased, the vehicle speed condition is satisfied earlier than the engine speed decreases to the fuel cut return speed during the fuel cut, and before the fuel cut end condition. It becomes possible to establish an idle stop condition. In this case, temporary fuel injection and ignition combustion between the fuel cut and the idle stop can be omitted, which contributes to further improvement of fuel consumption performance.

  When a predetermined idle stop end condition is satisfied after the idle stop condition is satisfied (step S10), the internal combustion engine is restarted (steps S12 and S14). In step S10, the driver lifts his / her foot from the brake pedal, the brake pedal is further depressed, the accelerator pedal is depressed, a predetermined time (for example, 3 minutes) has elapsed in the idle stop state, etc. It is determined that any one of them satisfies the idle stop termination condition.

  Thus, in the present embodiment, depending on the length of the period from the end of the fuel cut to the start of the idle stop, that is, the length of the fuel injection period temporarily resumed between the fuel cut and the idle stop. The fuel injection amount at the time of restart after the idle stop is changed.

  The ECU 0 satisfies the idle stop condition after the fuel cut end condition is satisfied (or the fuel injection is stopped after the delay time elapses) (or the engine speed decreases to a predetermined threshold or less by the idle stop process). ) Is counted (step S6). The length of the period is the elapsed time or the number of rotations of the crankshaft (or the number of cycles in which intake-compression-expansion-exhaust is one cycle). Then, the length of the period is compared with a predetermined determination value (step S11). However, in the case of shifting to the idle stop with the fuel cut state (step S8), the length of the period is regarded as zero.

When the length of the period is longer than the determination value, it is considered that the amount of oxygen stored in the catalyst 41 during the fuel cut is somewhat reduced by the operation accompanied by fuel injection before the start of idle stop. . Therefore, there is little possibility that a large amount of NO _x is discharged when the engine is restarted after the idle stop, and the internal combustion engine is restarted with a normal fuel injection amount (step S12). However, in general, an increase correction for the purpose of facilitating the start is added to the fuel injection amount at the restart of the internal combustion engine.

On the other hand, when the length of the period is equal to or less than the determination value, oxygen stored in the catalyst 41 during the fuel cut remains almost as it is, and the NO _x reduction efficiency in the catalyst 41 remains lowered. There is a possibility that a large amount of NO _x may be discharged when the engine is restarted after the idle stop. Therefore, the fuel injection amount is increased from the normal value (step S12), and the internal combustion engine is restarted (step S14).

  Further, the fuel injection amount at this time is determined according to the length of the fuel cut period before the idle stop. ECU0 preliminarily satisfies the fuel cut end condition (or stops the fuel injection when the delay time elapses), and then satisfies the fuel cut condition or the idling stop condition (or the engine speed is predetermined by the idling stop process). The length of the period until it falls below the threshold) is counted (step S3). As the fuel cut period is longer, the ECU 0 sets a larger increment of the fuel injection amount in the restart step S14 (relative to the injection amount in normal restart (step S12)) (step S13).

  It supplements regarding the fuel injection quantity at the time of the restart of an internal combustion engine in step S13 and S14. The fuel injection amount increase correction is typically performed by increasing the injection amount from the injector 11 in one injection opportunity (increasing the valve opening time of the injector 11) and / or one cycle of one cylinder 1. This can be realized by increasing the number of times of fuel injection in.

  However, in reality, when the air-fuel ratio of the air-fuel mixture becomes excessively rich, the combustion becomes unstable and hinders restart. Therefore, a rich limit (lower limit) is set for the air-fuel ratio, and a restriction is imposed on the fuel injection amount so that the air-fuel ratio does not fall below the lower limit even in the increase correction at the time of restart.

  As already mentioned, at the time of restarting the internal combustion engine and at the time immediately after the restart, the fuel is compared with the normal operating range after the warm-up of the internal combustion engine is completed (basically the target is the theoretical air-fuel ratio). The injection amount is increased (increase at start-up). In steps S13 and S14, the fuel amount is further added to the starting increase in step S12. Therefore, depending on the increment determined in step S13, the air-fuel ratio of the air-fuel mixture in step S14 falls below the lower limit. There is a possibility.

  Therefore, in steps S13 and S14, instead of or in addition to increasing the injection amount and the number of injections from the injector 11 at one time (with the restart and immediately thereafter, the air-fuel ratio is within the rich limit range. The fuel injection amount (the integrated amount) at the time of restart may be increased in such a manner that the period during which the starting increase is performed is made longer than that in step S12.

  In the present embodiment, a fuel cut that temporarily stops fuel injection is performed when a predetermined fuel cut condition is satisfied, and an idle stop that stops idle rotation of the internal combustion engine is performed when a predetermined idle stop condition is satisfied. The internal combustion engine control device 0 is configured to change the fuel injection amount when restarting the internal combustion engine that has been idle-stopped according to the length of the period from the end of fuel cut to the start of idle stop. .

According to the present embodiment, the increase in the NO _x emission amount when the internal combustion engine is restarted when the idling stop is started in a state where a large amount of oxygen stored in the catalyst 41 remains during the fuel cut. It can suppress suitably.

In this embodiment, when the length of the period from the end of the fuel cut to the start of the idle stop is equal to or less than a predetermined value or 0, the fuel injection amount at the time of restarting the internal combustion engine is increased as compared with the case where it is not It is said. In addition, since the increment of the fuel injection amount in the former case is determined according to the length of the fuel cut period before the idle stop, the amount of oxygen that flows into the catalyst 41 during the fuel cut and is occluded therein Accordingly, it is possible to increase the fuel injection amount at the time of restart and more reliably suppress the increase in the NO _x emission amount at the restart after the idle stop. On the contrary, if the amount of oxygen stored in the catalyst 41 during the fuel cut is relatively small, it is allowed to reduce the increase in the fuel injection amount at the restart after the idle stop.

  The present invention is not limited to the embodiment described in detail above.

  For example, in the above-described embodiment, even if the temporary fuel injection is restarted between the fuel cut and the idle stop, if the fuel injection period is equal to or less than the determination value, the restart after the idle stop is performed. The fuel injection amount was corrected to increase at the start.

  As a mode other than this, there was no temporary resumption of fuel injection between the fuel cut and the idle stop, in other words, the length of the period from the end of the fuel cut to the start of the idle stop is zero. Only in the case where the fuel injection amount is present, the fuel injection amount may be corrected to be increased upon restart after the idle stop. In other words, the determination value in step S11 is 0.

  Further, the fuel injection amount at the time of restart after the idle stop may be changed according to the length of the period from the end of the fuel cut to the start of the idle stop counted in step S6. At this time, it is conceivable that the longer the period, the smaller the increment of the fuel injection amount set in step S13.

  In addition, the specific configuration of each unit, the processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 11 ... Injector 12 ... Spark plug

Claims (2)

Implementing a fuel cut that temporarily stops fuel injection when a predetermined fuel cut condition is established, and performing an idle stop that stops idle rotation of the internal combustion engine according to the establishment of a predetermined idle stop condition,
The length of the period from the end of the fuel cut to the start of the idle stop is counted, and the fuel injection amount at the time of restarting the idling-stopped internal combustion engine is changed according to the counted period length A control device for an internal combustion engine. If the length of the period from the completion of the fuel cut and the start of the idle stop is the predetermined or less or 0, and increasing the fuel injection amount at the time of restarting the internal combustion engine as compared with otherwise,
2. The control apparatus for an internal combustion engine according to claim 1, wherein the increment of the fuel injection amount in the former case is determined according to the length of the fuel cut period before the idle stop.

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