JP2016070125A - Internal combustion engine control engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control device for suppressing properly the deterioration of emission at a cold starting time of the internal combustion engine.SOLUTION: An internal combustion engine control device controls an internal combustion engine equipped with a variable valve timing mechanism capable of increasing/decreasing the length of a valve overlap period, for which both an intake valve and an exhaust valve are opened. At a cold starting time of the internal combustion engine, a fuel injection rate is corrected to increase, and a valve overlap period is provided. As the increment in the increasing correction of the fuel injection rate is the more, the upper limit of the length of the valve overlap period is set the lower, and the present warming degree of the intake port is estimated from the integration of the suction amount or the fuel injection rate from the start of the internal combustion engine and the valve overlap period, thereby to construct of the internal combustion engine to reduce the increment the more in the increasing correction of the fuel injection rate for the higher warming degree.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control device for controlling an internal combustion engine associated with a variable valve timing (Variable Valve Timing) mechanism.

  2. Description of the Related Art An internal combustion engine mounted on a vehicle or the like is known that includes a VVT mechanism that can variably control the opening / closing timing of an intake valve and / or an exhaust valve (see, for example, the following patent document).

JP 2014-031763 A

  At the time of cold start of the port injection type internal combustion engine in which the injector is disposed in the intake port, the temperature around the intake port is low, so the fuel injected from the injector becomes liquid and adheres to the wall surface of the intake port Port wet easily occurs. Since the fuel for the port wet is not properly drawn into the cylinder, the air-fuel ratio of the air-fuel mixture is disturbed, the combustion may become unstable, and the emission of harmful substances may increase.

  At present, by correcting the increase in the fuel injection amount at the time of cold start of the internal combustion engine and immediately after the cold start, the instability of combustion of the air-fuel mixture caused by port wet and the increase of emission of harmful substances Is avoiding.

  On the other hand, immediately after starting the internal combustion engine, the intake valve and / or exhaust valve opening / closing timing is operated via the VVT mechanism to provide a valve overlap period in which both the intake valve and the exhaust valve are open, thereby exhausting from the combustion chamber. It is also conceivable to promote the atomization of the liquid fuel by causing a part of the exhaust to be discharged to the intake port.

  However, if a valve overlap period is simply provided, the fuel injection amount increase correction is overlapped with the atomization of the port wet fuel, the air-fuel ratio of the air-fuel mixture becomes excessively rich, and the discharge amount of harmful substances increases. Could end up.

  An object of the present invention is to suitably suppress deterioration of emissions during cold start of an internal combustion engine.

  The present invention controls an internal combustion engine with a variable valve timing mechanism that can increase or decrease the length of a valve overlap period in which both an intake valve and an exhaust valve are opened. When the fuel injection amount is increased and corrected, a valve overlap period is provided, and as the increase in the fuel injection amount increase is increased, the upper limit of the valve overlap period is set lower. A control device for an internal combustion engine that estimates the current warming degree of the intake port from the integration of the intake air amount or fuel injection amount from the start and the valve overlap period, and decreases the increment in the fuel injection amount increase correction as the warming degree increases Configured.

  ADVANTAGE OF THE INVENTION According to this invention, the deterioration of the emission at the time of the cold start of an internal combustion engine can be suppressed suitably.

The figure which shows schematic structure of the internal combustion engine and control apparatus in one Embodiment of this invention. The figure which illustrates the relationship between the increment of the increase correction of fuel injection quantity, and the upper limit of the length of a valve overlap period in the time immediately after the cold start of an internal combustion engine. The figure which illustrates the relationship between the warming degree of an intake port and the increment of the increase correction of fuel injection quantity in the time immediately after the cold start of an internal combustion engine. The figure which illustrates the relationship between the length of the cumulative intake amount (or cumulative fuel injection amount) from the start and the valve overlap period and the degree of warming of the intake port at the time immediately after the cold start of the internal combustion engine.

  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 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 by 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 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.

  The internal combustion engine in the present embodiment is accompanied by a VVT mechanism 6 that can variably control the opening / closing timing of the intake valve. The VVT mechanism 6 is a known one (motor drive VVT) in which the rotation phase of the intake camshaft that opens and closes the intake valve of each cylinder 1 with respect to the crankshaft is changed by an electric motor.

  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 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 (in other words, a required load), and a water temperature sensor that detects a cooling water temperature indicating the temperature of the internal combustion engine. Cooling water temperature signal d, battery current / voltage signal e output from a current / voltage sensor that detects the current and / or voltage of the on-vehicle battery 17, intake temperature and intake pressure in the intake passage 3 (especially, the surge tank 33) The intake air temperature / intake pressure signal f output from the temperature / pressure sensor for detecting the intake air and the cam angle of the intake camshaft A cam angle signal g output from the cam angle sensor, a brake signal h output from a sensor (such as a brake switch or a master cylinder pressure sensor) for detecting that the brake pedal is depressed or the amount of depression of the brake pedal are input. Is done.

  From the output interface, the ignition signal i for the igniter 13, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, the opening operation signal l for the EGR valve 23, and the VVT mechanism 6, the control signal n for the intake valve timing is output.

  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) Volume), opening / closing timing of the intake valve, and the like. The ECU 0 applies various control signals i, j, k, l, and n corresponding to the operation parameters via the output interface.

  Further, the ECU 0 controls an electric motor (starter motor or ISG (Integrated Starter Generator), not shown) at the time of starting the internal combustion engine (a cold start or a return from an idling stop). The signal o is input and cranking is performed by rotating the crankshaft by the electric motor. 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.

  Thus, the ECU 0 of the present embodiment provides a valve overlap period in which both the intake port and the exhaust port are opened through the operation of the VVT mechanism 6 immediately after the cold start of the internal combustion engine, and is discharged from the combustion chamber of the cylinder 1. The exhaust gas is partially discharged to the intake port to warm the intake port and promote atomization of the liquid fuel.

  However, during the cranking at the time of cold start of the internal combustion engine and the timing immediately after the complete explosion (including during idling), correction is performed to increase the fuel injection amount from the basic injection amount. The basic injection amount referred to here is the amount of intake air (fresh air) charged in the cylinder 1 that is necessary for setting the air-fuel ratio of the air-fuel mixture to the stoichiometric air-fuel ratio or a target air-fuel ratio set in the vicinity thereof. It is a proportional injection amount. The air-fuel ratio of the air-fuel mixture becomes richer than the target air-fuel ratio due to the increase correction of the fuel injection amount at the time of cold start and immediately after the cold start.

  If a valve overlap period is simply provided immediately after the cold start, the fuel injection amount increase correction overlaps with the atomization of the port wet fuel, and the air-fuel ratio of the air-fuel mixture may become excessively rich. There is. Therefore, in the present embodiment, as shown in FIG. 2, the upper limit of the length of the valve overlap period is set lower as the increment from the basic injection amount by the increase correction of the fuel injection amount at the time immediately after the cold start increases. To do. That is, when the fuel injection amount increase correction is relatively large, the valve overlap period is shortened, and when the increase correction is relatively small, the valve overlap period is lengthened to prevent the air-fuel ratio from becoming excessively rich. .

  As shown in FIG. 3, the increase from the basic injection amount in the fuel injection amount increase correction at the time immediately after the cold start is reduced as the degree of warming of the intake port increases. This is based on the fact that the amount of liquid fuel adhering to the wall surface of the intake port as port wet decreases as the temperature of the intake port rises.

  The current degree of warming of the intake port is estimated based on the accumulated amount of the intake amount or fuel injection amount filled in the cylinder 1 counted from the start of the internal combustion engine and the length of the valve overlap period. can do. FIG. 4 shows the relationship between the integrated value (so-called time integration) of the intake amount or fuel injection amount from the start of the internal combustion engine, the length of the valve overlap period, and the degree of warming of the intake port. In FIG. 4, the solid line represents the transition of the intake port temperature rise when the valve overlap period is relatively short, the broken line represents the transition of the intake port temperature rise when the valve overlap period is relatively long, It shows the transition of the temperature rise of the intake port when the valve overlap period is medium. Naturally, as the cumulative total intake amount or total fuel injection amount from the start of the internal combustion engine increases, the warm-up of the internal combustion engine proceeds and the temperature of the intake port also rises. Further, as the valve overlap period is longer, the intake port is warmed by the internal EGR and its temperature rises.

  In the memory of the ECU 0, the integrated value of the intake amount or the fuel injection amount from the start of the internal combustion engine and the length of the valve overlap period (the accumulated valve overlap period up to the present (time integration) or the time average) Map data (or function equation) that defines the relationship between the intake port warming degree and the intake port warming degree, and a map that defines the relationship between the intake port warming degree and the increment from the basic injection amount in the fuel injection amount increase correction Data (or function formula) and map data (or function formula) defining the relationship between the increment from the basic injection amount in the fuel injection amount increase correction and the upper limit of the valve overlap period are stored. .

  At the time immediately after the cold start of the internal combustion engine, the ECU performs the integrated value of the intake air amount or the fuel injection amount from the start to the present time and the length of the valve overlap period (the accumulated time or the valve overlap period up to the present time). The map is searched using the key (which may be an average) as a key (or calculated by substituting it into a function expression), and the current warming degree of the intake port is obtained. Next, the map is searched using the current degree of warming of the intake port as a key (or calculated by substituting it into a function equation), and the increment to be set at present in the increase correction of the fuel injection amount is obtained. Further, the map is searched using the increment in the increase correction of the current fuel injection amount as a key (or calculated by substituting it into the function formula), and the upper limit of the length of the valve overlap period to be set is obtained. After that, the fuel injection amount increase correction and the intake valve timing operation via the VVT mechanism 6 are executed. In the intake valve timing operation, the correction amount is added to the original valve overlap period determined according to the current engine speed within the upper limit range obtained from the above map, and the valve overlap period is set to the original period. Than to expand.

  If the integrated value of the intake air amount (or fuel injection amount) filled in the cylinder 1 reaches a predetermined value, it is considered that each part of the internal combustion engine has been warmed up to some extent. Decrease the correction amount.

  The above-described correction for increasing the length of the valve overlap period is executed only at the cold start, that is, at the start in a low temperature state where the temperature of the internal combustion engine is equal to or lower than a predetermined value. The temperature of the internal combustion engine can be obtained by referring to the coolant temperature signal d. When the internal combustion engine is stopped for a short time, such as when the engine is idle, if the internal combustion engine temperature at the start is already equal to or higher than the predetermined value, the amount of port wet generation is small and correction for expansion of the valve overlap period is unnecessary. is there. Therefore, the correction amount for the valve overlap period remains 0.

  In the present embodiment, the internal combustion engine attached with the VVT mechanism 6 capable of increasing or decreasing the length of the valve overlap period in which both the intake valve and the exhaust valve are opened is controlled. When the fuel injection amount is increased and corrected, a valve overlap period is provided, and as the increase in the fuel injection amount increase is increased, the upper limit of the valve overlap period is set lower. A control device for an internal combustion engine that estimates the current warming degree of the intake port from the integration of the intake air amount or fuel injection amount from the start and the valve overlap period, and decreases the increment in the fuel injection amount increase correction as the warming degree increases 0 was configured.

  According to the present embodiment, when port wet occurs and the combustion state deteriorates, a part of the exhaust discharged from the combustion chamber of the cylinder 1 is caused to flow out to the intake port by extending the valve overlap period. It becomes possible to promote atomization of the liquid fuel adhering to the wall surface of the port. Therefore, an increase in the emission amount of harmful substances at the time of cold start of the internal combustion engine can be suitably suppressed. In addition to avoiding the problem that the air-fuel ratio of the air-fuel mixture becomes excessively rich due to the increase correction of the fuel injection amount at the time immediately after the cold start and the expansion correction of the valve overlap period, the increase in the fuel injection amount can be avoided. Can be reduced as much as possible to reduce unnecessary fuel consumption, which contributes to improved fuel efficiency. In addition, it is allowed to reduce the amount of noble metal used in the catalyst 41 in preparation for deterioration of emissions during cold start, which contributes to cost reduction.

  The present invention is not limited to the embodiment described in detail above. For example, the specific mode of the VVT mechanism for increasing / decreasing the valve overlap period is arbitrary and not uniquely limited. In addition to those that advance / retard the rotation phase of the intake camshaft with respect to the crankshaft, those that advance / retard the rotation phase of the exhaust camshaft that opens and closes the exhaust valve with respect to the crankshaft, intake valves or exhaust valves There are several known cams that use multiple cams to open the valve and use them appropriately, those that change the lever ratio of the rocker arm via an electric motor, and those that use an intake or exhaust valve as an electromagnetic solenoid valve. These various mechanisms are allowed to be selected and adopted.

  Other specific configurations of each part 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 or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 11 ... Injector 6 ... Variable valve timing (VVT) mechanism

Claims (1)

Controlling an internal combustion engine with a variable valve timing mechanism that can increase or decrease the length of the valve overlap period in which both the intake valve and the exhaust valve are opened,
When the internal combustion engine is cold started, the fuel injection amount is corrected to be increased and a valve overlap period is provided.The larger the increment in the fuel injection amount increase correction, the lower the upper limit of the valve overlap period. ,
Furthermore, the current warming degree of the intake port is estimated from the sum of the intake air amount or fuel injection amount from the start of the internal combustion engine and the valve overlap period, and the increase in the fuel injection amount increase correction decreases as the warming degree increases. Control device for internal combustion engine.

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