JP2014058926A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve restarting performance of an internal combustion engine in a case when the internal combustion engine is stopped in a low temperature state in the last operation.SOLUTION: A length of time to continue cranking without supplying a fuel to a cylinder in starting the present operation, is determined according to a level of a temperature of an engine before stopping the last operation. It is estimated that the lower the temperature of the engine before stopping the last operation, the more a degree of fogging of an ignition plug is. Therefore, the time of cranking the internal combustion engine without accompanied with fuel supply can be taken long, when a temperature of the engine before stopping the last operation is low, in comparison with a case when the temperature is high. Thus the cylinder is ventilated, and the degree of fogging of the ignition plug can be reduced.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to control at engine start.

  When starting an internal combustion engine, it is usual to perform cranking by rotating the crankshaft of the engine by a starter motor (cell motor) which is an electric motor (see, for example, Patent Document 1 below). Cranking ends when the engine starts from the first explosion to the consecutive explosion and the rotational speed of the crankshaft exceeds a determination value determined according to the coolant temperature or the like.

  When starting in a cold region and / or in winter, the viscosity of the lubricating oil is high, the rotational speed of cranking by the starter motor tends to decrease, and the pressure in the combustion chamber of the cylinder tends to increase. In addition, since the temperature in the combustion chamber and the temperature of the spark plug are low, an appropriate spark discharge is not caused in the gap between the center electrode and the ground electrode of the spark plug, and the ignition of the air-fuel mixture fails and the starting failure Fall into. Therefore, it is conceivable that fuel injection and ignition are not started until the engine speed is sufficiently increased by cranking (see, for example, Patent Document 2 below).

JP 2011-202643 A JP 09-170543 A

  However, if fogging has already occurred on the spark plug before the internal combustion engine is started, there is a risk that the air-fuel mixture cannot be ignited well even if fuel injection and ignition are started after the engine speed has increased sufficiently. There is. In particular, in the previous operation, if the operation time of the internal combustion engine is short and the internal combustion engine is stopped before the warm-up of the internal combustion engine is completed, liquid fuel remains in the cold intake port or the combustion chamber and ignition occurs. The plug electrode gets wet. Such fogging of the spark plug reduces the insulation resistance between the electrodes and hinders spark discharge necessary for ignition. If ignition of the air-fuel mixture fails, the unburned fuel component liquefies and wets the spark plug further, making it difficult to start the engine.

  The present invention has been made by paying attention to the above-mentioned problem for the first time, and is intended to improve the restartability of the internal combustion engine when the internal combustion engine is stopped at a low temperature in the previous operation. It is aimed.

  The present invention is characterized in that the length of time for which cranking is continued without supplying fuel to the cylinder at the time of the current start is set according to the temperature level of the internal combustion engine before the stop of the previous operation. A control device for an internal combustion engine is configured.

  The lower the temperature of the internal combustion engine before the stop of the previous operation, the higher the degree of fogging that liquid fuel adheres to the electrode of the spark plug. Therefore, in the present invention, when the temperature of the internal combustion engine before the stop of the previous operation is low, compared with the case where the temperature is high, the time for cranking the internal combustion engine without fuel supply at the time of starting is further increased. Take longer. By cranking without fuel injection, the cylinder is ventilated and the amount of liquid fuel adhering to the electrode of the spark plug is reduced, that is, the fogging of the spark plug is alleviated or eliminated. Then, the probability of succeeding in spark ignition of the air-fuel mixture increases.

  According to the present invention, it is possible to improve the restartability of the internal combustion engine when the internal combustion engine is stopped at a low temperature in the previous operation.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The figure which shows the area | region of the water temperature at the time of a stop which ventilates a cylinder at the time of start, and the water temperature at the time of start. The flowchart which shows the example of a procedure of the process which the control apparatus of this embodiment performs. The flowchart which shows the example of a procedure of the process which the control apparatus of the modification of this invention performs.

  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 for an internal combustion engine 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 (N signal) b output from an engine rotation sensor that detects the rotation angle of the crankshaft and the engine speed, An accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal or the opening of the throttle valve 32 as an accelerator opening (so-called required load), and a brake that is output from a sensor that detects the amount of depression of the brake pedal Stepping amount signal d, intake air temperature / intake pressure signal e output from a temperature / pressure sensor for detecting intake air temperature and intake pressure in intake passage 3 (especially surge tank 33), water temperature sensor for detecting engine cooling water temperature Output from the cam angle sensor at a plurality of cam angles of the cooling water temperature signal f output from the intake camshaft or exhaust camshaft. A cam angle signal (G signal) g is, the battery voltage indicating the state of charge of the vehicle battery, a battery signal h or the like to be output from the sensor for detecting the battery current and the battery temperature are input.

  From the output interface, an ignition signal i is output to the igniter 13 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. As the operation parameter determination method itself, a known method can be adopted. The ECU 0 applies various control signals i, j, k corresponding to the operation parameters via the output interface.

  The ECU 0 inputs a control signal l to a starter motor (cell motor, not shown) when starting the internal combustion engine (a cold start or a return from an idling stop). Cranking is performed by rotating the crankshaft by engaging the pinion gear with the ring gear on the outer periphery of the flywheel (in the case of MT vehicle) or the drive plate (in the case of AT vehicle). Then, from the first explosion to the consecutive explosion, when the engine speed, that is, the rotation speed of the crankshaft exceeds a determination value determined according to the cooling water temperature or the like, it is considered that the explosion has been completed and the cranking is finished.

  Thus, the ECU 0 according to the present embodiment responds to the level of the temperature of the internal combustion engine before stopping the previous operation in order to improve the restartability when the internal combustion engine is stopped at a low temperature in the previous operation. The length of time during which cranking is continued without supplying fuel to the cylinder 1 at the time of the current start is set. Cranking is performed without injecting fuel from the injector 11 because the intake port and the combustion chamber of the cylinder 1 of the internal combustion engine are ventilated and liquid fuel adhering to the electrode of the spark plug 12 is removed even a little, that is, ignition. This is intended to reduce the fogging of the plug 12.

  Note that “previous operation stop” basically means that the internal combustion engine has been stopped in response to the ignition switch being turned OFF. An idle stop in a vehicle having an idle stop function does not correspond to a “previous operation stop”, but a stop of an internal combustion engine in a hybrid vehicle may correspond to a “previous operation stop”.

  In principle, cranking without fuel supply is performed when the internal combustion engine is restarted in response to the ignition switch being operated from OFF to ON. When returning from idle stop in a vehicle with an idle stop function, it is required to restart as soon as possible, and it is normal that the engine is already warmed up, so there is no fuel supply. Cranking is not performed. However, when restarting the internal combustion engine in a hybrid vehicle, cranking without fuel supply may be performed.

  The ECU 0 stores in advance a memory and holds at least the temperature of the internal combustion engine at the time immediately before the internal combustion engine stops, that is, the coolant temperature of the engine. Then, when the internal combustion engine is restarted, the stored coolant temperature value is read out, and based on this, the length of the cranking time without fuel supply is determined. Specifically, the lower the coolant temperature immediately before the previous stop of the internal combustion engine, the longer the cranking time without fuel supply. Further, when the coolant temperature immediately before the previous stop is higher than a predetermined value, it is considered that the amount of liquid fuel adhering to the electrode of the spark plug 12 is small before the engine is restarted. It is not necessary to carry out cranking without accompanying, and fuel injection may be started from the beginning of the starting process.

  In this embodiment, every time the internal combustion engine is started (especially every time the ignition switch is turned on), the coolant temperature of the engine is stored and held in the memory, and every time the internal combustion engine is stopped (particularly, the ignition switch is turned off). The engine coolant temperature is stored in a memory and held.

Hereinafter, the stop water temperature Tt stored at the time of the most recent stop of the internal combustion engine is referred to as “previous stop water temperature Tt”, and the start-up water temperature Ts stored at the latest start is referred to as “previous start-up water temperature Ts ₀ ”. Each is called. In addition, the operation state in the period from the start to the stop of the latest internal combustion engine is referred to as “previous operation state”.

When the internal combustion engine is started, the previous stop water temperature Tt falls below the threshold value Thw, and the previous start water temperature Ts ₀ and the previous stop water temperature Tt are within a predetermined region A (hatched in FIG. 2). If this is the case, it is suggested that the previous operating state was not sufficiently warmed up. Region A is a region lower than the upper limit G0 of the previous stop water temperature Tt is determined depending on the starting temperature Ts ₀ last. The upper limit G0 is determined based on an experiment that observes the relationship between the starting water temperature Ts and the stopping water temperature Tt at which ignition failure occurs due to fogging or smoldering of the spark plug 12.

  FIG. 3 shows a procedure example of processing executed by the ECU 0 according to the program in the startup processing of the internal combustion engine. The ECU 0 starts cranking of the engine by the starter motor (step S2) when the ignition switch is operated to be turned on or when a condition for ending the idle stop and restarting the engine is established (step S1). .

Further, based on the level of the temperature of the internal combustion engine at the start of the previous operation (previous start water temperature Ts ₀ ) and the temperature of the internal combustion engine before the stop (previous stop water temperature Tt) stored in the memory. Thus, the length of the cranking time without fuel supply is set (step S3). When the previous operation state is not in the region A shown in FIG. 2 (the previous stop water temperature Tt was higher than the predetermined value G0), or when the current start is a return from the idle stop. The time length of cranking without fuel supply is set to zero. In the case where the previous operation state is in the region A shown in FIG. 2, the lower the water temperature Tt at the previous stop, the longer the cranking time without fuel supply.

  Then, after the elapse of the time determined in step S3 (step S4), fuel injection from the injector 11 to each cylinder 1 and ignition of the air-fuel mixture by spark discharge of the spark plug 12 are started (step S5). ).

  If the rotational speed of the crankshaft that has been started exceeds the judgment value (step S6), it is considered that the explosion has been completed and the cranking of the engine is terminated (step S7).

  In this embodiment, the length of time for which cranking is continued without supplying fuel to the cylinder 1 at the time of the current start is set according to the temperature level of the internal combustion engine before the stop of the previous operation. A control device 0 of the characteristic internal combustion engine was configured.

  The lower the temperature of the internal combustion engine before the stop of the previous operation, the higher the degree of fogging that liquid fuel adheres to the electrode of the spark plug 12. Therefore, when the temperature of the internal combustion engine before the stop of the previous operation is low, it takes a longer time to crank the internal combustion engine without fuel supply at the time of starting than when the temperature is high. By cranking without fuel injection, the cylinder 1 is ventilated and the amount of liquid fuel adhering to the electrode of the spark plug 12 is reduced, that is, fogging of the spark plug 12 is reduced or eliminated, and the mixture is ignited. The probability of success is increased. Moreover, the smoldering which carbon etc. which generate | occur | produce by incomplete combustion of a fuel adhere to the electrode of the spark plug 12 can also be suppressed. According to the present embodiment, it is possible to improve the restartability of the internal combustion engine when the internal combustion engine is stopped at a low temperature in the previous operation.

  The present invention is not limited to the embodiment described in detail above. In the above embodiment, a cranking period without fuel supply is provided from the beginning of the starting process of the internal combustion engine. On the other hand, as shown in FIG. 4, at the beginning of the starting process, while performing fuel injection and ignition as usual (step S8), cranking is performed (step S2), and even if a predetermined time elapses, the explosion is completed. If not reached (steps S9, S10), cranking without fuel supply may be performed for the first time (steps S11, S3, S4).

  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 or the like.

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

Claims (1)

The internal combustion engine is characterized in that the length of time for which cranking is continued without supplying fuel to the cylinder at the time of the current start is set according to the temperature level of the internal combustion engine before the stop of the previous operation. Control device.

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