JP2016183583A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a start failure when restarting an internal combustion engine which is stopped before the completion of warmup in a short time after the stop.SOLUTION: A control device of an internal combustion engine which sets a fuel injection amount at a restart of a stopped internal combustion engine larger as a temperature of the cooling water of the internal combustion engine at the restart is low reduces a fuel injection amount in the case that deviation between a temperature of a combustion chamber of a cylinder at the restart and the temperature of the cooling water is large by comparing it with a fuel injection amount in the case that the deviation between the temperature of the combustion chamber and the temperature of the cooling water is small on condition that the temperature of the cooling water at the restart is the same.SELECTED DRAWING: Figure 3

Description

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

  The fuel injection amount at the start of the internal combustion engine, more specifically, the fuel injection amount during cranking for start-up is usually adjusted to increase or decrease according to the coolant temperature indicating the temperature of the internal combustion engine. (For example, see the following patent document). This is because, when the internal combustion engine is at a low temperature, the friction loss increases, the fuel is less likely to vaporize in the combustion chamber of the cylinder, and the amount of fuel that does not contribute to combustion even when injected is increased.

  Also, in a port injection type internal combustion engine in which the injector is arranged near the intake port of the cylinder, part of the fuel injected from the injector becomes liquid and adheres to the wall surface of the intake port, the umbrella portion of the intake valve, etc. Port wet occurs. In starting control of a port injection type internal combustion engine, it is necessary to set the fuel injection amount in anticipation of the occurrence of this port wet.

JP 2012-0777718 A

  When the operation of the internal combustion engine is stopped before the warm-up to sufficiently raise the temperature of the started internal combustion engine is completed and the internal combustion engine is started again in a short time after the stop, the fuel is based only on the cooling water temperature of the internal combustion engine. By determining the injection amount, a starting failure may be caused.

  FIG. 3 shows an example of changes in the temperature of the cooling water and the temperature of the combustion chamber (wall) of the cylinder when the internal combustion engine is stopped after the internal combustion engine is started and before the warm-up is completed. In FIG. 3, the temperature of the cooling water of the internal combustion engine is represented by a broken line, and the temperature of the combustion chamber is represented by a solid line. The time 0 second is the time when the operation of the internal combustion engine is stopped, and the period before that is the time when the internal combustion engine is operated. While the temperature of the combustion chamber of the internal combustion engine that has been cold-started at time -30 seconds rises relatively quickly, the temperature of the cooling water rises relatively slowly. For this reason, the temperature of the combustion chamber and the temperature of the cooling water are greatly different at the time of 0 second when the internal combustion engine is stopped before the warm-up is completed.

  When the internal combustion engine is restarted within several tens of seconds after the operation is stopped, the temperature of the combustion chamber is still considerably higher than the temperature of the cooling water. Therefore, when the fuel injection amount is determined with reference to the temperature of the cooling water, an amount of fuel corresponding to the low cooling water temperature, that is, a large amount of fuel that does not meet the high combustion room temperature is injected from the injector. Most of the gas is vaporized in the combustion chamber, and the air-fuel ratio of the air-fuel mixture becomes overrich. As a result, ignition / combustion of the air-fuel mixture does not work well, causing a delay or failure in starting the internal combustion engine. Such an event may occur, for example, in a situation where the driver stops on the road and waits for another passenger.

  The present invention, which has been made by paying attention to the above problems for the first time, is intended to prevent a starting failure when an internal combustion engine that has been stopped before the completion of warm-up is restarted in a short time after the stop.

  In the present invention, the fuel injection amount at the time of restarting the stopped internal combustion engine is set so as to increase as the temperature of the cooling water of the internal combustion engine at the time of restarting decreases. If the temperature difference between the combustion chamber of the cylinder and the temperature of the cooling water at the time of restart is large under the condition that the temperatures are the same, the fuel injection amount is the difference between the temperature of the combustion chamber and the temperature of the cooling water. The control device for the internal combustion engine is configured so as to be smaller than the fuel injection amount when the is smaller.

  Estimate the temperature of the combustion chamber at the time of the most recent stop of the internal combustion engine or the temperature of the combustion chamber at the time of restart, and set the combustion injection amount at the time of restart according to the estimated temperature of the combustion chamber Is also preferable.

  Whether or not the difference between the temperature of the combustion chamber of the cylinder and the temperature of the cooling water at the time of restarting is large is easily determined based on the elapsed time from the last stop of the operation of the internal combustion engine to the restart and the temperature of the cooling water. I can judge. That is, when the internal combustion engine is restarted before a predetermined time has elapsed since the most recent stop, and when the temperature of the cooling water at the stop or restart is less than a predetermined value, It can be determined that the difference between the temperature of the combustion chamber of the cylinder and the temperature of the cooling water is large.

  The temperature of the combustion chamber at the time of the most recent stop of the internal combustion engine is the temperature of the cooling water at the start of the previous internal combustion engine, and the intake amount or fuel injection amount supplied to the cylinder between the start and stop of the previous internal combustion engine It can be estimated based on the total accumulated amount.

  According to the present invention, it is possible to prevent a start failure when an internal combustion engine that has been stopped before the completion of warm-up is restarted in a short time after the stop.

The figure which shows schematic structure of the internal combustion engine for vehicles in one Embodiment of this invention. The flowchart which shows the example of the procedure of the process which the control apparatus of the embodiment performs. The figure which illustrates transition of the temperature of a cooling water and the temperature of a combustion chamber in the case of stopping an internal combustion engine after starting of an internal combustion engine, before warming-up is completed.

  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 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 external EGR (Exhaust Gas Recirculation) device 2 realizes a so-called high-pressure loop EGR. The EGR device 2 includes an external EGR passage 21 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, an EGR cooler 22 provided on the EGR passage 21, and an EGR passage 21. And an EGR valve 23 that controls the flow rate of the EGR gas flowing through the EGR passage 21. 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, specifically to a 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 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. The coolant temperature signal d, the battery current / voltage signal e output from the current / voltage sensor for detecting the current and / or voltage of the vehicle-mounted battery, the intake air temperature and the intake pressure in the intake passage 3 (particularly, the surge tank 33). The intake air temperature / intake pressure signal f output from the temperature / pressure sensor to be detected and the multiple cam angles of the intake camshaft A cam angle signal g output from the angular sensor, an atmospheric pressure signal h or the like to be output from the sensor for detecting the atmospheric pressure is inputted.

  From the output interface, an ignition signal i is output to the igniter 13, a fuel injection signal j is output to the injector 11, an opening operation signal k is output to the throttle valve 32, an opening operation signal l is output to the EGR valve 23, and the like. To do.

  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.

  Further, the ECU 0 inputs a control signal o to an electric motor (starter motor or ISG (Integrated Starter Generator)) when the internal combustion engine is started (a cold start or a return from an idling stop). Then, 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.

  The fuel injection amount during cranking is determined with reference to the temperature of the cooling water of the internal combustion engine. As a general rule, the lower the coolant temperature at the start of the internal combustion engine, the greater the basic fuel injection amount. In the memory of the ECU 0, map data or a function expression that defines the relationship between the coolant temperature and the basic fuel injection amount is stored in advance. The ECU 0 searches the map using the coolant temperature at the start as a key, or substitutes the coolant temperature at the start into the function formula to obtain a basic amount of fuel injection amount.

  In addition to this, correction according to engine speed, intake air temperature, and / or atmospheric pressure during cranking may be added to the basic amount. That is, when the rate of increase in engine speed (the amount of increase in engine speed per unit time) is low, the basic fuel injection amount can be increased compared to when the engine speed is high. When the intake air temperature is low, the basic fuel injection amount can be increased compared to when the intake air temperature is high, and / or when the atmospheric pressure is low, the fuel injection amount can be increased compared to when the atmospheric pressure is high. The basic amount can be reduced.

  However, the ECU 0 of the present embodiment does not always execute cranking of the internal combustion engine using the basic fuel injection amount described above as it is. As shown in FIG. 2, when the ECU 0 is considered to have a large difference between the temperature of the combustion chamber of the cylinder 1 and the temperature of the cooling water when starting the internal combustion engine (step S1), the fuel based on the cooling water temperature at the time of starting The basic amount of the injection amount is not used as it is, and an amount of fuel smaller than the basic amount is injected from the injector 11 (step S2).

  With regard to step S1, a plurality of methods are conceivable for determining whether or not the difference between the temperature of the combustion chamber and the temperature of the cooling water at the start of the internal combustion engine is large. For example, when the internal combustion engine is restarted before a predetermined time (for example, 10 seconds) has elapsed since the most recent stop of the internal combustion engine, and the cooling water temperature at the time of the stop or restart is a predetermined value ( For example, when the temperature is less than 50 ° C., it can be determined that the difference between the combustion room temperature and the cooling water temperature is large. In other words, when the internal combustion engine is restarted after a lapse of a predetermined time after the most recent internal combustion engine is stopped, or the cooling water temperature at the time of the latest operation stop or the current restart is equal to or higher than a predetermined value (that is, When the internal combustion engine has been warmed up or completed during the previous operation), it is determined that the difference between the combustion room temperature and the cooling water temperature is small. When this method is adopted, the coolant temperature measured when the internal combustion engine is stopped is stored in the memory and the supply of electric power from the in-vehicle battery to the ECU 0 is maintained until at least a predetermined time has elapsed. After the predetermined time has elapsed, it is possible to cut off the power supply to the ECU 0 and avoid the consumption of the electric power stored in the battery.

  Even in step S1, the temperature of the combustion chamber at the time of the most recent internal combustion engine stoppage is estimated, and it is determined whether or not the difference between the temperature of the combustion chamber at the start of this time and the temperature of the cooling water is large. Good. Assuming that the difference between the combustion room temperature and the coolant temperature at the start of the previous internal combustion engine was small, the coolant temperature at the start of the previous internal combustion engine (can be counterfeited with the combustion room temperature at the previous start), and the previous internal combustion engine The total amount of intake air or fuel injection supplied to the cylinder 1 from the start to the stop of the engine, that is, the total amount of heat generated in the combustion chamber (the increase in the combustion room temperature during the period from the previous start to the stop is this It is possible to estimate the combustion room temperature when the most recent internal combustion engine is stopped. With such an estimation method, it is not necessary to separately mount a temperature sensor for detecting the temperature of the combustion chamber in the cylinder 1. In addition, when the cooling water temperature at the time when the operation of the most recent internal combustion engine is stopped is less than a predetermined value and the internal combustion engine is restarted before a certain determination time has elapsed since the stop, the combustion room temperature and the cooling water temperature are The determination time is set to be longer as the estimated temperature of the combustion chamber when the internal combustion engine is stopped is higher. Alternatively, the difference between the estimated temperature of the combustion chamber when the internal combustion engine is stopped and the temperature of the cooling water when the latest internal combustion engine is stopped or restarted this time is obtained, and when this difference exceeds a predetermined value, It may be determined that the difference between the combustion room temperature at the start and the coolant temperature is large.

  Further, the temperature of the combustion chamber at the start of the current internal combustion engine may be estimated and compared directly with the temperature of the cooling water at the start. The combustion room temperature at the time of restart of the internal combustion engine can be estimated based on the combustion room temperature at the time of the latest stop of the internal combustion engine, the elapsed time from the latest stop to the restart, and the cooling water temperature during the stop of the internal combustion engine. According to Newton's cooling law (approximate empirical rule), the speed at which heat is transferred from the combustion chamber to the cooling water is proportional to the temperature difference between the combustion room temperature and the cooling water temperature. It goes without saying that the difference between the estimated temperature of the combustion chamber at the start and the temperature of the cooling water at the start is obtained, and that the difference between the combustion room temperature and the cooling water temperature is determined to be large when this difference exceeds a predetermined value. Yes.

  Regarding step S2, a plurality of methods are conceivable as to how to reduce the fuel injection amount during cranking from the basic amount based on the coolant temperature at the start of the internal combustion engine. For example, when it is determined that the difference between the combustion room temperature at the start and the coolant temperature is large, the fuel injection amount during cranking is reduced by a uniform amount from the basic amount or by a uniform rate from the basic amount. Alternatively, the amount or ratio of reducing the fuel injection amount from the basic amount is set to increase as the elapsed time from the latest stop time of the internal combustion engine to the current restart time becomes shorter. This is because the difference between the temperature of the combustion chamber of the cylinder 1 and the temperature of the cooling water is considered to be larger as the time from the stop to restart of the internal combustion engine is shorter.

  When the temperature of the combustion chamber at the time of the most recent internal combustion engine shutdown is estimated, the fuel injection amount is reduced from the basic amount as the difference between the estimated combustion room temperature and the coolant temperature at the start of this time is larger The quantity or proportion can be large. Further, in addition to this, as the time from the latest stop to restart of the internal combustion engine is shorter, the amount or ratio of reducing the fuel injection amount from the basic amount may be increased.

  In addition, when the temperature of the combustion chamber at the start of the current internal combustion engine is estimated, the fuel injection amount is reduced from the basic amount as the difference between the estimated combustion room temperature and the coolant temperature at the start of the current start is larger. Increase the amount or rate of reduction. The basic fuel injection amount based on the cooling water temperature at the time of restart is an amount that takes into account the fuel for the port wet generated in the port injection internal combustion engine. The liquid fuel adhering to the wall surface of the intake port or the umbrella portion of the intake valve as the port wet is not sucked into the combustion chamber of the cylinder 1 during cranking for starting the internal combustion engine, and is used for combustion and acceleration of the internal combustion engine. Does not contribute. The amount of port wet increases as the temperature in the vicinity of the intake port where fuel is injected is lower. However, the temperature in the vicinity of the intake port when the internal combustion engine is restarted is higher than the temperature of the combustion chamber of the cylinder 1. Even the temperature of the cooling water is close. Therefore, even if the combustion room temperature at the time of restart of the internal combustion engine is estimated and grasped, the basic amount of the fuel injection amount based on the coolant temperature at the time of restart is used as a base (subtracted from the basic amount). It is meaningful to determine the amount of fuel actually injected. However, in step S2, the fuel injection amount during cranking is determined without taking into account the basic amount based on the coolant temperature at the time of restart. That is, the lower the estimated combustion room temperature at the time of restart, the more during the cranking. You may control to increase the quantity of the fuel to inject.

  Conversely, when it is considered that the difference between the temperature of the combustion chamber of the cylinder 1 and the temperature of the cooling water at the start of the internal combustion engine is small, the basic amount of fuel based on the cooling water temperature at the start is being cranked. Inject from the injector 11 (step S3). If the cooling water temperature at the restart of the internal combustion engine is equal, the combustion injection amount determined through step S2 is less than the basic fuel injection amount used in step S3.

  In the present embodiment, the fuel injection amount at the restart of the stopped internal combustion engine is set so as to increase as the temperature of the coolant of the internal combustion engine at the time of restart decreases. If the difference between the temperature of the combustion chamber of the cylinder 1 and the temperature of the cooling water at the time of restart is large, the fuel injection amount is expressed as the temperature of the combustion chamber and the temperature of the cooling water. The control device 0 for the internal combustion engine is configured so as to be smaller than the fuel injection amount in the case where the difference between the two is smaller. According to the present embodiment, it is possible to prevent a starting failure when the internal combustion engine that has been stopped before the completion of warm-up is restarted in a short time after the stop.

  In addition, the temperature of the combustion chamber at the time of the most recent stop of the internal combustion engine or the temperature of the combustion chamber at the time of restart is estimated, and then restarted according to the estimated temperature of the combustion chamber and the temperature of the cooling water at the time of restart If the fuel injection amount at the time is set, the fuel injection amount during cranking can be optimized, and unnecessary fuel consumption can be avoided.

  The present invention is not limited to the embodiment described in detail above. The specific configuration 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 12 ... Spark plug 3 ... Intake passage 32 ... Throttle valve 4 ... Exhaust passage d ... Cooling water temperature signal j ... Fuel injection signal

Claims (4)

The fuel injection amount at the restart of the stopped internal combustion engine is set so as to increase as the temperature of the cooling water of the internal combustion engine at the restart is lower,
Under the condition that the temperature of the coolant at the time of restart is the same, the fuel injection amount when the difference between the temperature of the combustion chamber of the cylinder at the time of restart and the temperature of the coolant is large is the temperature of the combustion chamber. A control apparatus for an internal combustion engine that reduces the fuel injection amount when the deviation from the temperature of the cooling water is smaller. The combustion injection amount at the time of restart is set according to the estimated temperature of the combustion chamber after estimating the temperature of the combustion chamber at the latest stop of the internal combustion engine or the temperature of the combustion chamber at the time of restart. The internal combustion engine control device described. When restarting the internal combustion engine before the predetermined time has passed since the most recent stop of the internal combustion engine, and when the temperature of the cooling water at the stop or restart is less than the predetermined value The control apparatus for an internal combustion engine according to claim 1 or 2, wherein it is determined that the difference between the temperature of the combustion chamber of the cylinder and the temperature of the cooling water is large. The most recent stop of the internal combustion engine based on the temperature of the cooling water at the start of the previous internal combustion engine and the total cumulative amount of intake air or fuel injection supplied to the cylinder between the start and stop of the previous internal combustion engine The internal combustion engine according to claim 2, wherein the temperature of the combustion chamber at the time is estimated.

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