JP2018105164A - Device for controlling internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten time required for restarting an internal combustion engine after engine stall.SOLUTION: A device for controlling an internal combustion engine estimates an amount of unburned fuel remaining inside a suction port continuing to an inside of a cylinder or the cylinder in restarting an internal combustion engine that stops due to engine stall, and opens wider an opening degree of a throttle valve before starting of cranking or during cranking for starting the internal combustion engine as the estimated amount of unburned fuel is larger.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control device that controls an internal combustion engine mounted on a vehicle or the like.

  As is well known, when starting a stopped internal combustion engine, a crankshaft, which is an output shaft of the internal combustion engine, is driven to rotate by an electric motor, and fuel is injected from an injector and burned in a cylinder. Perform cranking to accelerate rotation. Cranking is considered to be complete explosion when the internal combustion engine goes from the first explosion to the continuous explosion and the rotational speed of the crankshaft, that is, the engine speed exceeds a threshold value determined according to the cooling water temperature of the internal combustion engine, etc. End (for example, see the following patent document).

JP, 2006-125364, A

  Controlled or scheduled, such as when the engine stalls (ignition switch (ignition key) OFF operation) that are not related to the driver's or user's intention, or when the idle stop condition is satisfied and the idle stop is performed When restarting an internal combustion engine that has been stopped due to an abnormal stop other than a stop), if the start process is executed in accordance with a normal routine, the start of the internal combustion engine is greatly delayed, that is, the crankshaft rotation is accelerated slowly and cranked. It may take a long time to finish.

  In recent internal combustion engines, the fuel injection amount during cranking is increased in advance so that the engine can be reliably started even if various types of fuel are used. In addition, when a sudden drop in engine speed that may cause engine stall occurs, fuel injection amount increase correction may be performed as control for avoiding engine stall. In addition, when the engine is stalled, fuel combustion failure occurs due to the low engine speed, and unburned fuel components remain in the cylinders of the stopped internal combustion engine and in the intake ports connected to the cylinders. Together, the air-fuel ratio during cranking is excessively rich compared to the oil-tight leak assumed in normal routines (a small amount of fuel leaks from the injector while the internal combustion engine is stopped). There was found.

  The present invention has been made by paying attention to the above points for the first time, and an object thereof is to shorten the time required for restarting the internal combustion engine after engine stall.

  In order to solve the above-described problems, the present invention estimates the amount of unburned fuel remaining in the cylinder and / or in the intake port connected to the cylinder when the internal combustion engine stopped due to the engine stall is restarted. As the estimated amount of unburned fuel is larger, the control device for the internal combustion engine is configured so that the opening degree of the throttle valve is greatly increased before and / or during the cranking for starting the internal combustion engine.

  According to the present invention, the time required for restarting the internal combustion engine after engine stall can be shortened.

The figure which shows schematic structure of the internal combustion engine for vehicles and control apparatus in one Embodiment of this invention. The timing diagram which shows the content of the start control of the internal combustion engine by the control apparatus of the embodiment.

  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 of the present embodiment is a spark ignition type four-stroke engine and includes a plurality of cylinders 1 (for example, three cylinders, 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 for each cylinder 1. 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 ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

  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.

  The exhaust gas recirculation device 2 realizes a so-called high pressure loop EGR, and an external EGR that communicates the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3. The passage 21, an EGR cooler 22 provided on the EGR passage 21, and an EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of EGR gas flowing through the EGR passage 21 are used as elements. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined location downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, particularly to the surge tank 33.

  An ECU (Electronic Control Unit) 0 serving as a control device for an internal combustion engine according to the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface of the ECU 0 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 a crank angle sensor that detects the rotation angle of the crankshaft and the engine speed, and an accelerator pedal. , An accelerator opening signal c output from a sensor that detects the amount of depression of the engine or the opening of the throttle valve 32 as an accelerator opening (so-called required engine load), an intake passage 3 (in particular, a surge tank 33) connected to the cylinder 1 ), An intake air temperature / intake pressure signal e output from a temperature / pressure sensor that detects the intake air temperature and intake pressure, a cooling water temperature signal f output from a water temperature sensor that detects a cooling water temperature suggesting the temperature of the internal combustion engine, Cam angle signal g output from the cam angle sensor at a plurality of cam angles of the intake cam shaft or the exhaust cam shaft, Battery current / voltage signal h or the like which is output from the sensor for detecting the terminal current or a terminal voltage of Tteri is input.

  From the output interface of the ECU 0, the ignition signal i for the igniter attached to the spark plug 12, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, and the EGR valve 23 open. Output the operation signal l.

  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, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR rate) Various operating parameters such as volume). The ECU 0 applies various control signals i, j, k, and l corresponding to the operation parameters via the output interface.

  In addition, when starting the stopped internal combustion engine, the ECU 0 inputs a control signal n for operating an electric motor (starter motor or ISG (Integrated Starter Generator)) to the electric motor, and cranks for rotating the crankshaft by the electric motor. I do. Cranking for starting the internal combustion engine ends when the internal combustion engine reaches from the first explosion to the continuous explosion and the engine speed, that is, the rotational speed of the crankshaft exceeds the threshold value, and is regarded as complete explosion. The threshold value of the engine speed, which is the cranking termination condition, can be increased or decreased according to the temperature of the internal combustion engine. Specifically, the lower the cooling water temperature of the internal combustion engine, the higher the setting, but it is approximately 500 rpm.

  Thus, when restarting the internal combustion engine that has been stopped due to engine stall, the ECU 0 of the present embodiment estimates the amount of unburned fuel remaining in the cylinder 1 and / or in the intake port connected to the cylinder 1, The larger the estimated amount of unburned fuel, the larger the opening of the throttle valve 32 that is performed before and / or during cranking for starting the internal combustion engine.

  As indicated by a chain line in FIG. 2, when restarting an internal combustion engine that has been stopped due to an engine stall not related to the intention of the driver or the user, The start of the engine is greatly delayed, that is, the acceleration of crankshaft rotation is slow and it may take a long time to finish cranking. As described above, this is because the air-fuel ratio of the air-fuel mixture filled in the cylinder 1 becomes excessively rich during cranking at the restart after the engine stall and causes combustion failure.

  In contrast, in the present embodiment, as indicated by a solid line in FIG. 2, when restarting the internal combustion engine that has been stopped due to engine stall, cranking is executed with the throttle valve 32 opened more than normal. Then, the air-fuel ratio of the air-fuel mixture filled in the cylinder 1 is brought close to the stoichiometric air-fuel ratio to suppress the occurrence of defective combustion so that the rotation of the crankshaft can be accelerated appropriately. The opening degree of the throttle valve 32 at this time increases as the amount of unburned fuel remaining in the cylinder 1 or the intake port at the start of the internal combustion engine increases, and doubles that in the normal routine. The above opening may be obtained.

  As shown in FIG. 2, the operation of increasing the opening of the throttle valve 32 is preferably performed before the start of cranking, that is, before starting the electric motor that rotationally drives the crankshaft.

  A method for estimating the amount of unburned fuel remaining in the cylinder 1 and the intake port at the start of the internal combustion engine will be described. The ECU 0 performs an engine stall, that is, an abnormal stop other than a controlled or scheduled stop, such as when the ignition switch is turned off or the idle rotation of the internal combustion engine is stopped when a predetermined idle stop condition is established. When the engine speed reaches the predetermined reference speed, the injection amount of the fuel injected from each injector 11 associated with each cylinder 1 is integrated during the stall period from when the engine speed reaches a predetermined reference speed until it becomes zero. However, when an increase in the engine speed, that is, acceleration is observed in the expansion stroke visiting the cylinder 1 immediately after the injection opportunity for injecting fuel from the corresponding injector 11 toward a certain cylinder 1, the fuel is injected at the injection opportunity. Since the fuel is considered to have burned, the amount of fuel injected at that opportunity is not added to the integrated value. In other words, only the amount of fuel injected at an injection opportunity in which no increase in the engine speed was observed in the expansion stroke visiting the cylinder 1 immediately after the injection opportunity is added to the integrated value. The integrated value of the fuel injection amount during the stall period thus counted is regarded as the amount of unburned fuel remaining in the cylinder 1 or the intake port after the internal combustion engine is stopped due to the engine stall.

  If the elapsed time from the stop of the internal combustion engine due to the engine stall to the restart is shorter than a predetermined value, the amount of unburned fuel remaining in the cylinder 1 or the intake port immediately after the stop of the internal combustion engine is calculated. The estimated amount of unburned fuel remaining in the cylinder 1 or the intake port at the start of restart of the internal combustion engine can be used as it is. The ECU 0 sets the opening degree of the throttle valve 32 before the start of cranking for restarting the internal combustion engine or during the cranking as the estimated amount of unburned fuel increases.

  On the other hand, if the elapsed time between the stop and restart of the internal combustion engine due to the engine stall exceeds a predetermined value, the amount of unburned fuel remaining in the cylinder 1 or the intake port during the elapsed time decreases. It is assumed that Therefore, the longer the elapsed time, the less the estimated amount of unburned fuel remaining in the cylinder 1 or the intake port at the start of restart of the internal combustion engine. After all, the longer the elapsed time, the smaller the opening of the throttle valve 32 before the start of cranking for restart or during cranking.

  The opening of the throttle valve 32 that is larger than that of the normal routine is preferably reduced to the normal opening before the end of cranking, that is, before the engine speed reaches the threshold value. May be maintained until the end of cranking.

  In addition, if the estimated amount of unburned fuel remaining in the cylinder 1 or the intake port at the start of restart after engine stall is greater than a predetermined value, the fuel injection amount during cranking is normal. It is preferable to reduce the weight. In this case, the ECU 0 reduces the amount of fuel injected from the injector 11 during cranking as the estimated amount of unburned fuel increases. The amount of fuel injection may be reduced by thinning out the opportunity to inject fuel from each injector 11 (so that fuel is not intentionally injected at a specific injection opportunity).

  Alternatively, when the estimated amount of unburned fuel remaining in the cylinder 1 or the intake port is greater than a predetermined value at the start of restart after engine stall, fuel is injected for a certain period from the start of cranking. It is also conceivable to scavenge the inside of the cylinder 1 and the intake port without doing so. In this case, the ECU 0 sets the scavenging period during which no fuel is injected from the injector 11 as the estimated amount of unburned fuel increases.

  In this embodiment, when restarting the internal combustion engine that has been stopped due to engine stall, the amount of unburned fuel remaining in the cylinder 1 or in the intake port connected to the cylinder 1 is estimated, and the estimated unburned fuel is estimated. The control device 0 of the internal combustion engine that opens the opening of the throttle valve 32 larger before or during the cranking for starting the internal combustion engine is configured as the amount of the engine increases.

  According to this embodiment, it is possible to prevent the air-fuel ratio of the air-fuel mixture that is charged into the cylinder 1 from being excessively rich during cranking during restart after an engine stall, thereby avoiding poor combustion of the air-fuel mixture. Is possible. As a result, the rotation of the internal combustion engine is appropriately accelerated during cranking, and the start of the internal combustion engine can be completed without delay. Shortening the cranking period also leads to a reduction in fuel waste during cranking.

  In addition, depending on the estimated amount of unburned fuel remaining in the cylinder 1 and the intake port at the start of restart after engine stall, the fuel injection amount during cranking is reduced, or from the start of cranking By performing scavenging without injecting fuel for a required period, it is possible to further increase the certainty of starting the internal combustion engine and further reduce the fuel consumption.

  The present invention is not limited to the embodiment described in detail above. Various modifications can be made to the specific configuration of each part, the contents of processing, and the like 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 or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 11 ... Injector 3 ... Intake passage 32 ... Throttle valve j ... Fuel injection signal k ... Opening operation signal n ... Motor control signal for cranking

Claims (1)

When restarting an internal combustion engine that has been stopped due to an engine stall,
Estimate the amount of unburned fuel remaining in the cylinder or in the intake port connected to the cylinder, and the larger the estimated amount of unburned fuel, the more before the start of cranking for cranking the internal combustion engine or cranking A control device for an internal combustion engine that greatly opens the opening of the throttle valve.

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