JP2018141396A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an unreasonable decrease in idle speed after starting an internal combustion engine when a fuel having relatively low volatility is used. SOLUTION: When the engine speed does not rise to a threshold value within a predetermined time during cranking for starting an internal combustion engine, an internal combustion engine which increases and corrects the subsequent fuel injection amount as compared with the case where it does not. In the increase correction, the first correction term in which the increase amount decreases to 0 after a certain period of time and the increase amount are required for the first correction term to become 0. An internal combustion engine control device is configured in which a second correction term, which decreases to 0 after a period longer than the period elapses, is superimposed and added to the basic amount of fuel injection. In addition, in the increase correction, the correction term for the increase is added to the basic amount of the fuel injection amount, and when the increase due to the correction term is reduced to 0, the increase is gradually reduced for the internal combustion engine. The control device was configured. [Selection diagram] Fig. 2

Description

  The present invention relates to a control device that controls operation of an internal combustion engine.

The exhaust passage of the internal combustion engine, harmful substances HC contained in the exhaust gas discharged from the cylinders of the internal combustion engine, CO, three-way catalyst to harmless by oxidation / reduction of NO _x is mounted. In order to improve the efficiency of the purification process of harmful substances by the three-way catalyst, it is required to converge the air-fuel ratio of the gas flowing into the catalyst within a certain range near the theoretical air-fuel ratio. For this purpose, feedback control that measures the air-fuel ratio of the gas flowing through the exhaust passage through an air-fuel ratio sensor and increases or decreases the fuel injection amount in a direction to reduce the deviation between the measured air-fuel ratio and the target air-fuel ratio, that is, the theoretical air-fuel ratio. It is customary to implement.

  When starting an internal combustion engine that has been stopped, the crankshaft, which is the output shaft of the internal combustion engine, is driven to rotate by an electric motor, and fuel is injected from the injector and burned in the cylinder to accelerate the rotation of the crankshaft. Perform cranking. 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. finish. In addition, the fuel injection amount is adjusted so that the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio at the time immediately after the start of the internal combustion engine, but in order to suppress the deterioration of the emission, It is desirable to start feedback control that brings the air-fuel ratio closer to the stoichiometric air-fuel ratio as soon as possible after startup (see, for example, the following patent document).

Japanese Patent Laid-Open No. 10-288075

  When heavy fuel with low volatility is used, the engine speed may not be sufficiently accelerated during cranking for starting the internal combustion engine, and the start may be delayed. Therefore, in order to ensure that the internal combustion engine can be started even when heavy fuel is used, conventionally, when the engine speed does not reach the threshold value within a predetermined time during cranking, the fuel injection amount is set to be lower than normal. By further increasing the amount, the combustion of the air-fuel mixture is stabilized.

FIG. 3 shows a specific example thereof. When starting an internal combustion engine, increase the fuel injection amount to the basic amount (in principle, the amount of fuel whose ratio to the amount of air sucked into the cylinder is the stoichiometric air fuel ratio or a value close to it). By adding correction terms A, B, and C, the fuel injection amount is increased from the basic amount. The increase correction term A is attenuated after time t ₂ when cranking for starting the internal combustion engine is completed. Similarly, the increase correction term B attenuates after the cranking end time t ₂ , but the rate of attenuation is slower than that of the increase correction term A. The increase correction term B mainly compensates for a friction loss that increases when the internal combustion engine is at a low temperature, and is set to a larger value as the current temperature of the internal combustion engine is lower. Unlike the increase correction terms A and B, the increase correction term C increases or decreases stepwise.

In the conventional start control, when the engine speed does not reach the threshold value by the time t ₁ when the predetermined time has elapsed from the cranking start time t ₀ , the increase correction term C is set as shown in FIG. The fuel injection amount was increased by adding a further increase ΔC. Then, after the internal combustion engine has been completely exhausted and started, at a time t ₄ when it is considered that the combustion of the air-fuel mixture has sufficiently stabilized after a certain period of time has elapsed, the amount of increase in the fuel injection amount by the increase correction term C Was to be reduced step by step.

However, according to such control, at time t ₄ , the fuel injection amount suddenly decreases by ΔD, the air-fuel ratio of the air-fuel mixture temporarily becomes lean, and the engine torque output from the internal combustion engine fluctuates. Then, the engine speed is disturbed. Even if the feedback control of the air-fuel ratio has already started at this time, the disturbance generated at the time point t ₄ has not been absorbed, and the decrease in the engine speed could not be suppressed.

  The present invention has been made by paying attention to the above problems for the first time, and suppresses an undue drop in the idling speed after the start of the internal combustion engine when a fuel having a relatively low volatility is used. The intended purpose.

  In the present invention, when the engine speed does not rise to the threshold value within a predetermined time during cranking for starting the internal combustion engine, the internal combustion engine corrects the subsequent fuel injection amount by an increased amount as compared with the case where the engine speed does not increase. In the increase correction, in the increase correction, a first correction term that decreases to 0 after a certain period has elapsed, and the increase is required for the first correction term to become zero. A control device for an internal combustion engine is configured in which a superposition of a second correction term that decreases to 0 after a period longer than the period has been added to the basic amount of the fuel injection amount.

  In addition, in the present invention, when the engine speed does not increase to the threshold value within a predetermined time during cranking for starting the internal combustion engine, the subsequent fuel injection amount is corrected to be increased as compared with the case where the engine speed does not increase. In the control unit for an internal combustion engine, in the increase correction, the correction term for the increase is added to the basic amount of the fuel injection amount, and when the increase by the correction term is reduced to 0, the increase is A control device for an internal combustion engine that gradually decreases is configured.

  According to the present invention, it is possible to prevent an undue drop in the idling speed after the internal combustion engine is started when a fuel having a relatively low volatility is used.

The figure which shows schematic structure of the internal combustion engine and control apparatus in one Embodiment of this invention. The timing diagram explaining the content of the control which the control apparatus of the embodiment implements. The timing diagram explaining the content of the control at the time of starting of the conventional 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 4-stroke gasoline 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.

Air-fuel ratio sensors 43 and 44 for detecting the air-fuel ratio of the exhaust gas flowing through the exhaust passage are installed upstream and downstream of the catalyst 41 in the exhaust passage 4. Each of the air-fuel ratio sensors 43 and 44 may be an O ₂ sensor having a non-linear output characteristic with respect to the air-fuel ratio of the exhaust gas, or a linear A / F sensor having an output characteristic proportional to the air-fuel ratio of the exhaust gas. There may be. As for the output characteristics of the O ₂ sensor, the rate of change of the output with respect to the air-fuel ratio shows a large and steep slope in the range near the stoichiometric air-fuel ratio, and in the lean region where the air-fuel ratio is larger than that, it gradually approaches the lower saturation value. In a small rich region, a so-called Z characteristic curve that draws an asymptotic approach to a high saturation value is drawn. In the present embodiment, a linear A / F sensor is assumed as the air-fuel ratio sensor 43 on the upstream side of the catalyst 41, and an O ₂ sensor is assumed as the air-fuel ratio sensor 44 on the downstream side.

  The exhaust gas recirculation device 2 realizes a so-called high pressure loop EGR, and an EGR passage 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. 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. 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 a crank angle sensor that detects the rotation angle of the crankshaft and the engine speed, and depression of the 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 factor), an intake air temperature in the intake passage 3 (in particular, the surge tank 33), and An intake air temperature / intake pressure signal d output from a temperature / pressure sensor that detects intake pressure, a cooling water temperature signal e output from a water temperature sensor that detects a cooling water temperature indicating the temperature of the internal combustion engine, and upstream of the catalyst 41. The air-fuel ratio signal f output from the air-fuel ratio sensor 43 that detects the air-fuel ratio of the exhaust gas, the air-fuel combustion of the exhaust gas downstream of the catalyst 41 The air-fuel ratio signal g outputted from the air-fuel ratio sensor 44 for detecting the atmospheric pressure signal h or the like to be outputted from the atmospheric pressure sensor for detecting the atmospheric pressure is inputted.

  From the output interface, the ignition signal i for the igniter of 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 opening operation signal l for the EGR valve 23. Etc. are 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, h necessary for operation control of the internal combustion engine via the input interface, and requests the required fuel injection amount, fuel injection timing (once Operating parameters such as fuel injection pressure, ignition timing, required EGR amount (or EGR rate), etc. are determined. The ECU 0 applies various control signals i, j, k, and l corresponding to the operation parameters via the output interface.

  The ECU 0 controls the air-fuel ratio of the air-fuel mixture charged in the cylinder 1 and the air-fuel ratio of the exhaust gas discharged from the cylinder 1 and led to the catalyst 41 except during exceptional cases during cranking of the internal combustion engine or immediately after starting. Feedback control. The ECU 0 first calculates the amount of fresh air charged into the cylinder 1 from the intake pressure and intake temperature, the engine speed, the required EGR rate, etc., and determines the basic injection amount TP corresponding to this. The basic injection amount TP is typically an amount of fuel such that the ratio to the amount of air sucked into the cylinder 1 becomes a stoichiometric air fuel ratio or a value in the vicinity thereof.

  Next, the basic injection amount TP is corrected with a feedback correction coefficient FAF determined according to the air-fuel ratio on the upstream side and / or downstream side of the catalyst 41. Generally, the feedback correction coefficient FAF is adjusted according to the deviation between the air / fuel ratio of the gas actually measured through the air / fuel ratio sensors 43 and 44 and the target air / fuel ratio is lean relative to the target air / fuel ratio. It sometimes increases and decreases when the measured air-fuel ratio is rich with respect to the target air-fuel ratio. The normal target air-fuel ratio is set at or near the theoretical air-fuel ratio.

Then, the final fuel injection time (energization time for the injector 11) T is calculated in consideration of various correction factors K determined according to the state of the internal combustion engine and the invalid injection time TAUV of the injector 11. The fuel injection time T is
T = TP × FAF × K + TAUV
It becomes. Accordingly, the signal j is input to the injector 11 for the fuel injection time T, and the injector 11 is opened to inject fuel.

  The feedback control with reference to the air-fuel ratio signals f and g on the upstream side and / or downstream side of the catalyst 41 is, for example, that the cooling water temperature of the internal combustion engine is equal to or higher than a predetermined temperature, the fuel is not cut, and the power increase is not When a certain amount of time has elapsed since the start of the internal combustion engine, and the conditions such as the air-fuel ratio sensors 43 and 43 are active, the air-fuel ratio sensors 43 and 44 are active, and the intake pressure is normal are all satisfied. To implement.

  Further, when starting the stopped internal combustion engine, the ECU 0 inputs a control signal o for operating an electric motor (starter motor or ISG (Integrated Starter Generator)) to the electric motor, and rotates the crankshaft by the electric motor. Perform cranking. 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 as the cranking end condition can be increased or decreased according to the temperature of the internal combustion engine or the like. Specifically, the lower the cooling water temperature of the internal combustion engine, the higher the setting.

  Therefore, the ECU 0 of the present embodiment performs the subsequent fuel injection amount when the engine speed does not rise to the threshold value within a predetermined time during cranking for starting the internal combustion engine, as compared with the case where the engine speed does not increase. Correct the increase.

FIG. 2 shows a control pattern at the time of starting the internal combustion engine and after the start by the ECU 0 of the present embodiment. The solid line in FIG. 2 shows the transitions of the increase in the engine speed and the fuel injection amount when heavy fuel with low volatility is used. If the engine speed has not reached the threshold at a time t ₁ when a predetermined time has elapsed from the cranking start time t ₀ for starting the internal combustion engine, the ECU ₀ adds a correction that further increases the fuel injection amount. Thus, the combustion of the air-fuel mixture is stabilized, so that the internal combustion engine is surely brought to the complete explosion.

  There are three correction terms added to the basic fuel injection amount: an increase correction term A, an increase correction term B, and an increase correction term C. In order to increase the fuel correction amount, the basic injection amount TP is multiplied by (1 + increase correction term A + increase correction term B + increase correction term C) as part or all of the correction coefficient K to calculate the fuel injection time T. Will be. Note that the increase correction terms A, B, and C are assumed to be used even when the engine speed rises to a threshold value within a predetermined time during cranking, that is, fuel that is sufficiently high in volatility is used. 2 is not 0 as shown by a broken line in FIG. 2, but is added to the basic injection amount TP.

The increase correction term A is a correction term that is determined mainly according to the level of the engine speed during cranking and after the end of cranking, for acceleration of acceleration of the engine speed or suppression of blow-up. Time t ₁ after the value of the incremental correction term A in the case where the engine speed has not increased to the threshold value within a predetermined time during cranking, by ΔA than increasing correction term A in cranking in the case of normal extender To do. The magnitude of this increase ΔA is set larger as the engine speed during cranking is lower. The increase correction term A is gradually reduced to 0 after the time t ₂ when the internal combustion engine reaches a complete explosion. The speed of attenuation of the increase correction term A at that time is increased as the engine speed after the complete explosion time t ₂ is higher. In other words, the amount of decrease per unit time of the increase correction term A is increased as the engine speed after the complete explosion time t ₂ increases.

The increase correction term B is a correction term for compensation of the friction loss of the internal combustion engine, which is mainly determined according to the temperature of the internal combustion engine (cooling water temperature) during and after the cranking. The value of time t ₁ after the increasing correction term B in the case where the engine speed has not increased to the threshold value within a predetermined time during cranking, only ΔB than increasing correction term B in cranking in the case of normal extender To do. The magnitude of this increase ΔB is set larger as the cooling water temperature of the internal combustion engine during cranking is lower. Then, the increase correction term B is gradually reduced to 0 after time t ₂ when the internal combustion engine reaches a complete explosion. The speed of attenuation of the increase correction term B at that time is increased as the cooling water temperature of the internal combustion engine after the complete explosion time t ₂ is higher. In other words, the amount of decrease per unit time of the increase correction term B is increased as the cooling water temperature after the complete explosion time t ₂ becomes higher. The rate of attenuation of the increase correction term B is slower and slower than the rate of attenuation of the increase correction term A, and the increase correction term B becomes 0 after the increase correction term A becomes 0. .

The increase correction term C is, in principle, a correction term that does not decrease like the increase correction terms A and B, maintains the same magnitude for a certain period, and varies stepwise. The value of time t ₁ after the increasing correction term C when engine speed is not increased to the threshold value within a predetermined time during cranking, by ΔC than increasing correction term C in cranking in the case of normal extender To do. The magnitude of this increase ΔC is smaller than the increase ΔC of the increase correction term C in the conventional start control shown in FIG. The increase correction term C is gradually reduced after the time point t ₂ when the internal combustion engine reaches a complete explosion.

The ECU 0 finishes cranking at a time t ₂ when the internal combustion engine reaches a complete explosion state, and is measured by the air-fuel ratio sensors 43 and 44 at a time t ₃ when a certain amount of time has elapsed after the complete explosion. Air-fuel ratio feedback control for causing the air-fuel ratio to follow the target air-fuel ratio is started. On the other hand, due to the decrease in the increase correction terms A, B, and C, the air-fuel ratio of the air-fuel mixture approaches the stoichiometric air-fuel ratio from a richer state than the stoichiometric air-fuel ratio.

Thus, after starting the air-fuel ratio feedback control, the increase correction term C is gradually decreased to 0 (instead of stepwise) after time t ₄ when the combustion of the air-fuel mixture is considered to be sufficiently stabilized. Go. The increase correction terms A and B have decreased to 0 before reaching the time point t4.

  In the present embodiment, when the engine speed does not increase to the threshold value within a predetermined time during cranking for starting the internal combustion engine, the internal combustion engine that corrects the fuel injection amount thereafter is increased as compared with the case where the engine speed does not increase. In the engine control apparatus 0, in the increase correction, a first correction term (an increase correction term A or an increase correction term B) that decreases to 0 after a certain period has elapsed, and the increase amount A second correction term (an increase correction term B or an increase correction term C for the increase correction term A, or an increase correction) that decreases to 0 after a period longer than the time required for the first correction term to become zero has elapsed. A control device 0 for an internal combustion engine is configured in which a superposition of an increase correction term C) with respect to the term B is added to the basic fuel injection amount (basic injection amount TP).

  In addition, in this embodiment, when the engine speed does not increase to the threshold value within a predetermined time during cranking for starting the internal combustion engine, the subsequent fuel injection amount is increased and corrected as compared to the case where the engine speed does not increase. In the internal combustion engine control device 0, the correction term for the increase (increase correction term A, B or C) is added to the basic amount of fuel injection amount (basic injection amount TP) in the increase correction, When the amount of increase by the correction term is reduced to 0, the control device 0 for the internal combustion engine is configured to gradually decrease the amount of increase instead of stepwise.

According to the present embodiment, it is possible to prevent an undue drop in the idling speed after the internal combustion engine is started when a fuel having a relatively low volatility is used. In particular, as shown in FIG. 3, the increase in the fuel injection amount when the engine speed does not rise to the threshold value within a predetermined time during cranking is distributed to the increase correction terms A, B and C. Therefore, the remaining amount ΔD of the increase at the time point t ₄ when the increase correction is finished is smaller than ΔD in the conventional start control. Accordingly, the rate at which the fuel injection amount decreases before and after the time point t ₄ when the increase correction is finished can be reduced, that is, the disturbance generated at the time point t ₄ can be reduced, and the engine torque fluctuations and the engine It is possible to minimize the width of the decrease in the rotational speed.

In addition, the time t ₄ after ending the increasing correction of the fuel injection amount, and to gradually reduce the residual amount ΔD bulking, this also contributes to the suppression of the fluctuation of the engine torque and the engine speed fall Can do.

  The present invention is not limited to the embodiment described in detail above. In the above embodiment, the fuel injection amount increase correction terms A, B, and C are coefficients multiplied by the fuel injection amount basic injection amount TP. However, the increase correction terms A, B, and C are used as the basic injection amount TP (or A correction amount that is added to the basic injection amount TP multiplied by a feedback correction coefficient FAF or the like may be used.

  In addition, the specific configuration of each part can be variously modified without departing from the gist 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 4 ... Exhaust passage 41 ... Catalyst 43 ... Air-fuel ratio sensor upstream of catalyst 44 ... Air-fuel ratio sensor downstream of catalyst f ... Air-fuel ratio signal upstream of catalyst g ... Air-fuel ratio signal downstream of catalyst j ... Fuel injection signal o ... Cranking motor control signal

Claims (2)

When the engine speed does not rise to the threshold value within a predetermined time during cranking for starting the internal combustion engine, the control device for the internal combustion engine corrects the subsequent fuel injection amount as compared with the case where the engine speed does not increase. There,
In the increase correction, a first correction term that decreases to 0 after a certain period elapses and a period longer than the period required for the increase to become zero in the first correction term A control apparatus for an internal combustion engine that adds a superimposition of a second correction term that decreases to 0 to a basic amount of fuel injection amount. When the engine speed does not rise to the threshold value within a predetermined time during cranking for starting the internal combustion engine, the control device for the internal combustion engine corrects the subsequent fuel injection amount as compared with the case where the engine speed does not increase. There,
In the increase correction, the correction term for the increase is added to the basic amount of the fuel injection amount, and when the increase due to the correction term is reduced to 0, the control unit for the internal combustion engine gradually decreases the increase. .

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