JP6896331B2 - Internal combustion engine control device - Google Patents

Description

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

When starting an internal combustion engine that has been stopped, the crankshaft, which is the output shaft of the internal combustion engine, is rotationally driven by an electric motor, and fuel is injected from the injector to burn it in the cylinder, accelerating the rotation of the crankshaft. Perform cranking. Cranking is when the internal combustion engine goes from the first explosion to the continuous explosion and the rotation speed of the crankshaft, that is, the engine speed exceeds the complete explosion judgment value determined according to the cooling water temperature of the internal combustion engine, etc. (For example, refer to the patent document below).

In a port-injection type internal combustion engine that injects fuel from an injector toward an intake port connected to a cylinder, the timing at which fuel injection from the injector ends, that is, the timing at which the injector is closed, immediately after the start of the engine. Is the timing when a predetermined crank angle elapses after the intake valve of the cylinder is opened, more specifically, the timing of 90 ° CA (crank angle) after the exhaust top dead center, which is the majority while the intake valve is open. Inject fuel. This is because when the temperature of the internal combustion engine is low, port wet, that is, the amount of fuel injected from the injector liquefies and adheres to the inner wall of the intake port and the valve body of the intake valve, and the amount of fuel that is not properly sucked into the cylinder increases. In view of this, it is a measure for surely supplying the required amount of fuel into the cylinder while avoiding port wet.

On the other hand, after a certain amount of time has passed since the start and the cooling water temperature of the internal combustion engine has risen to the threshold value, the timing to end the fuel injection from the injector is set to a relatively early timing after the intake valve of the cylinder is opened. More specifically, the timing is switched to 30 ° CA after the exhaust top dead center, and the majority of the fuel is injected before the intake valve opens. When fuel is injected from the injector after the intake valve is opened, the fuel reaches the inside of the cylinder directly, and the latent heat (heat of vaporization) when this is vaporized lowers the temperature inside the cylinder (combustion chamber temperature) of the internal combustion engine. This leads to a decrease in the output engine torque. Therefore, by performing the majority of fuel injection before opening the intake valve, the decrease in the in-cylinder temperature is suppressed.

Japanese Unexamined Patent Publication No. 2017-008865

When low volatility heavy fuel is used, the engine speed may not accelerate sufficiently 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 if heavy fuel is used, if the engine speed does not reach a certain value within a predetermined time during cranking, the fuel injection amount is further increased than usual. By doing so, the combustion of the air-fuel mixture is stabilized.

As already mentioned, when the cooling water temperature rises to the threshold after starting the internal combustion engine, the timing of the end of fuel injection from the injector is switched, and the majority of fuel injection is performed after the intake valve is opened. Transition to the state performed before valve opening. In the past, the timing of this switching, in other words, the threshold value to be compared with the cooling water temperature was fixed regardless of the fuel properties.

However, when heavy fuel is used, the amount of port wet generated increases as compared with the case where it is not used. Therefore, when the fuel injection timing is switched, the amount of fuel sucked into the cylinder decreases, the actual air-fuel ratio of the air-fuel mixture filled in the cylinder becomes lean, and combustion destabilization or misfire occurs. As a result, the engine speed (idle speed) sometimes dropped.

In addition, the degree of fuel vaporization also depends on the fuel temperature, and the lower the fuel temperature, the more difficult it is for the fuel to vaporize. This tendency is particularly remarkable in heavy fuels, and heavy fuels having a low temperature generate a large amount of port wet, and the amount of fuel sucked into the cylinder is further reduced by that amount.

If the fuel injection amount is excessively increased in order to compensate for the port wet portion when heavy fuel is used, the fuel efficiency performance deteriorates. Not only that, after the fact, the port wet fuel is vaporized and sucked into the cylinder, so that the air-fuel ratio of the air-fuel mixture becomes excessively rich, which may lead to instability of combustion and misfire.

An object of the present invention is to prevent an unreasonable decrease in engine speed after starting an internal combustion engine when a fuel having relatively low volatility is used.

In the present invention, a port injection type internal combustion engine that injects fuel from an injector toward an intake port connected to a cylinder is controlled, and after the start of the internal combustion engine is completed, the temperature of the internal combustion engine (the temperature of the internal combustion engine). Some correlated temperature, that is, some temperature at which the higher the temperature, the higher the temperature of the internal combustion engine may be regarded as the temperature of the internal combustion engine referred to here. Typically, the cooling water temperature of the internal combustion engine). In the period before the temperature rises and reaches the threshold value, the timing at which the fuel injection from the injector ends is set to the timing when a predetermined crank angle elapses after the exhaust top dead point of the cylinder, and the temperature of the internal combustion engine reaches the threshold value. After reaching the threshold, the timing to finish the fuel injection from the injector is set to be earlier than before the temperature of the internal combustion engine reaches the threshold, and the engine is within a predetermined time during cranking for starting the internal combustion engine. When the rotation speed does not rise to a certain value, the fuel injection amount thereafter is increased and corrected, the threshold value is set higher, and the fuel temperature (correlates with the fuel temperature) as compared with the case where the rotation speed does not rise to a certain value. Some temperature, that is, some temperature at which it can be said that the higher the temperature, the higher the temperature of the fuel, may be regarded as the temperature of the fuel referred to here. For example, in the engine room of a vehicle in which an internal combustion engine is mounted. When the temperature) is less than the predetermined value, the control device of the internal combustion engine which sets the threshold value higher than the case where the fuel temperature is equal to or higher than the predetermined value is configured.

According to the present invention, it is possible to prevent an unreasonable decrease in the engine speed after the start of the internal combustion engine when a fuel having a relatively low volatility is used.

The figure which shows the schematic structure of the internal combustion engine and the control device in one Embodiment of this invention. The figure which shows the fuel injection timing in the normal case in the same embodiment. The figure which shows the fuel injection timing when the fuel with low volatility is used in the same embodiment.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle according to the present embodiment. The internal combustion engine of the present embodiment is a spark-ignition 4-stroke gasoline engine, and includes a plurality of cylinders 1 (one of which is illustrated in FIG. 1). An injector 11 for injecting fuel toward the intake port is provided upstream of the intake valve of each cylinder 1 and in the vicinity of the intake port connected to each cylinder 1. Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives an induction voltage generated by the ignition coil to induce a spark discharge between the center electrode and the ground electrode. The ignition coil is integrally built in the coil case together with the igniter which 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. 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 on the intake passage 3.

The exhaust passage 4 for discharging the exhaust guides the exhaust generated by burning the fuel in the cylinder 1 to the outside from the exhaust port of each cylinder 1. An exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gas are arranged on the exhaust passage 4.

The exhaust gas recirculation device 2 realizes a so-called high-pressure loop EGR, and is an EGR passage that connects 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 elements are 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 position downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined position downstream of the throttle valve 32 in the intake passage 3, specifically, the surge tank 33.

The ECU (Electronic Control Unit) 0, which is a control device for an internal combustion engine of 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 crank shaft and the engine rotation speed, and depression of the accelerator pedal. Accelerator opening signal c output from a sensor that detects the amount or opening of the throttle valve 32 as the accelerator opening (so to speak, the required engine load factor), intake temperature and intake pressure in the surge tank 33 of the intake passage 3. The intake air temperature / intake pressure signal d output from the temperature / pressure sensor that detects, the intake air temperature signal e that is output from the temperature sensor that detects the intake air temperature directly under the air cleaner 31 of the intake passage 3, and the cooling water temperature of the internal combustion engine. The cooling water temperature signal f output from the water temperature sensor to be detected, the cam angle signal g output from the cam angle sensor at a plurality of cam angles of the intake cam shaft or the exhaust cam shaft, and the air-fuel ratio of the gas flowing into the catalyst 41 are detected. The air fuel ratio signal h or the like output from the air fuel ratio sensor is input.

The cooling water temperature of the internal combustion engine suggests the temperature of the internal combustion engine. Further, the intake air temperature immediately below the air cleaner 31 of the intake passage 3 suggests the temperature in the engine room of the vehicle in which the internal combustion engine is mounted. This temperature correlates with the temperature of the fuel.

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 ECU 0 interprets and executes a program stored in the memory in advance, calculates an operation parameter, 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 the operation control of the internal combustion engine via the input interface, and obtains the required fuel injection amount and fuel injection timing (once). Operating parameters such as fuel injection pressure (including the number of fuel injections for combustion), fuel injection pressure, ignition timing, required EGR amount (or EGR rate), and the like are determined. The ECU 0 applies various control signals i, j, k, l corresponding to the operation parameters via the output interface.

Further, when starting the stopped internal combustion engine, 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. Crank. The cranking for starting the internal combustion engine is considered to be complete when the internal combustion engine goes from the first explosion to the continuous explosion and the engine speed, that is, the rotation speed of the crankshaft exceeds the complete explosion judgment value. finish. The complete explosion determination value, which is the end condition of cranking, may fluctuate depending on 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.

The ECU 0 has a reference value (which may be the same as the complete explosion determination value, which is a value higher than the complete explosion determination value) having the engine speed within a predetermined time during cranking for starting the internal combustion engine. If it does not rise to (may be good), the fuel injection amount after that is increased and corrected as compared with the normal case where it is not. With such correction control, even if a heavy fuel having low volatility is used, it is possible to stabilize the combustion of the air-fuel mixture and surely bring the internal combustion engine to the complete explosion.

Hereinafter, the control of the fuel injection timing after the engine speed reaches the complete explosion determination value and the cranking is completed, that is, the start of the internal combustion engine is completed will be described in detail. In the period after the start of the internal combustion engine is completed and before the cooling water temperature of the internal combustion engine rises and reaches the threshold value, the timing TC for ending the fuel injection from the injector 11, that is, the timing for closing the injector 11 is set. The timing is set at a timing at which a predetermined crank angle has elapsed after the intake valve of the cylinder 1 is opened, for example, at a timing of 90 ° CA after the exhaust top dead center. As a result, the majority of fuel injection is performed after the intake valve is opened. The timing TO for starting fuel injection, that is, the timing for opening the injector 11, is a timing that goes back by the required fuel injection amount from the timing for ending fuel injection. Assuming that the fuel injection end timing TC is constant, the larger the required fuel injection amount, the earlier the fuel injection start timing TO in order to lengthen the fuel injection time, that is, the valve opening time of the injector 11.

Then, after the cooling water temperature of the internal combustion engine reaches the threshold value, the timing TC for ending the fuel injection from the injector 11 is set earlier, for example, at a timing of 30 ° CA after the exhaust top dead center. As a result, the majority of fuel injection is performed before the intake valve is opened. Needless to say, if the timing TC at the end of fuel injection is advanced, the timing TO at the start of fuel injection is also advanced accordingly.

In the normal case where the engine speed rises to the reference value within a predetermined time during cranking for starting the internal combustion engine, the above threshold value to be compared with the cooling water temperature is set to, for example, 20 ° C. That is, after the start of the internal combustion engine is completed, until the cooling water temperature reaches 20 ° C., as shown in FIG. 2 (I), the majority of the fuel injection is performed after the intake valve is opened, and the cooling water temperature becomes high. After reaching 20 ° C., as shown in FIG. 2 (II), the majority of fuel injection is performed before the intake valve is opened.

On the other hand, if the engine speed does not rise to the reference value within a predetermined time during cranking, the above threshold value is set to a value higher than normal. Setting a high threshold indicates the time to switch the end timing of fuel injection, that is, the time to shift from the state where the majority of fuel injection is performed after the intake valve is opened to the state where the fuel injection is performed before the intake valve is opened. It means to delay more.

Further, the above threshold value when the engine speed does not rise to the reference value within a predetermined time during cranking also fluctuates depending on the temperature of the fuel. The ECU 0 of the present embodiment regards the intake air temperature directly below the air cleaner 31 of the intake passage 3 as the temperature of the fuel injected from the injector 11, and when the intake air temperature is low, it is compared with the case where the intake air temperature is high. , Set the above threshold high. For example, if the intake air temperature immediately below the air cleaner 31 is less than a predetermined value, the above threshold value is set to 40 ° C., and if the intake air temperature is equal to or more than a predetermined value, the above threshold value is set to 30 ° C.

If the engine speed does not rise to the reference value within the predetermined time during cranking, FIG. 3 (I) shows that the cooling water temperature reaches 20 ° C. after the start of the internal combustion engine is completed. As shown, the timing TC of the end of fuel injection is set to the timing of 90 ° CA after the exhaust top dead center, and the fuel injection amount is increased as compared with the normal case. For the convenience of extending the valve opening time of the injector 11 from the normal case, the timing TO of the start of fuel injection is ahead of the normal case shown in FIG. 2 (I). The fuel injection amount gradually decreases as the cooling water temperature rises, and approaches that of the normal case. That is, as shown in FIG. 3 (II), the timing TO of the start of fuel injection is gradually delayed while keeping the timing TC of the end of fuel injection at 90 ° CA after the exhaust top dead center, and FIG. 2 (I) ), We will approach the normal case. The states of FIGS. 3 (I) and 3 (II) are the states in which the majority of the fuel injection is performed after the intake valve is opened, as in the case of FIG. 2 (I). After that, if the cooling water temperature rises to a threshold value corresponding to the intake air temperature directly under the air cleaner 31, specifically, 30 ° C. to 40 ° C., as shown in FIG. 3 (III), the timing TC of the end of fuel injection To the timing of 30 ° CA after the exhaust top dead center. That is, there is a transition from a state in which the majority of the fuel injection is performed after the intake valve is opened to a state in which the majority of the fuel injection is performed before the intake valve is opened. The fuel injection amount at this time may be about the same as the fuel injection amount in the normal case. That is, the timing TO of the start of fuel injection is about the same as in the normal case shown in FIG. 2 (II).

In the present embodiment, the port injection type internal combustion engine that injects fuel from the injector 11 toward the intake port connected to the cylinder 1 is controlled, and the temperature of the internal combustion engine rises after the start of the internal combustion engine is completed. In the period before the threshold is reached, the timing TC for ending the fuel injection from the injector 11 is set to the timing when a predetermined crank angle elapses after the intake valve of the cylinder 1 is opened, and the temperature of the internal combustion engine rises. After reaching the threshold value, the timing TO for ending the fuel injection from the injector 11 was set to be earlier, and the engine speed did not rise to a certain value within a predetermined time during cranking for starting the internal combustion engine. In the case, the fuel injection amount thereafter is increased and corrected as compared with the case where the fuel injection amount is not provided, and the threshold value is set higher. Further, when the fuel temperature is low, the fuel injection amount is higher than when the fuel temperature is high. A control device 0 for an internal combustion engine that sets a higher threshold is configured.

According to this embodiment, it is possible to avoid leaning the air-fuel ratio of the air-fuel mixture after the start of the internal combustion engine is completed when a fuel having a relatively low volatility is used. As a result, it is possible to prevent an unreasonable decrease in the idle speed after the start of the internal combustion engine. Further, since the increase correction of the fuel injection amount can be suppressed to the minimum necessary amount, the fuel efficiency performance does not deteriorate unnecessarily, and the air-fuel ratio is not enriched due to the excessive increase correction.

The present invention is not limited to the embodiments described in detail above. For example, in the above embodiment, the intake air temperature immediately below the air cleaner 31 in the intake passage 3 is regarded as the current fuel temperature, but when a temperature sensor for detecting the fuel temperature is mounted, the temperature sensor is considered. The temperature of the fuel can be directly measured and used for control.

In addition, 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 the control of an internal combustion engine mounted on a vehicle or the like.

0 ... Control device (ECU)
1 ... Cylinder 11 ... Injector 3 ... Intake passage 31 ... Air cleaner b ... Crank angle signal e ... Intake temperature signal f ... Cooling water temperature signal j ... Fuel injection signal o ... Motor control signal for cranking

Claims (1)

It controls a port-injection type internal combustion engine that injects fuel from an injector toward the intake port connected to the cylinder.
In the period after the start of the internal combustion engine is completed and before the temperature of the internal combustion engine rises and reaches the threshold value, the predetermined crank angle is set after the exhaust top dead center of the cylinder to end the fuel injection from the injector. After the internal combustion engine temperature reaches the threshold value, the timing at which the fuel injection from the injector ends is earlier than before the internal combustion engine temperature reaches the threshold value.
If the engine speed does not rise to a certain value within a predetermined time during cranking for starting the internal combustion engine, the subsequent fuel injection amount is increased and corrected, and the threshold value is set as compared with the case where the engine speed does not rise to a certain value. Set higher,
Further, a control device for an internal combustion engine that sets the threshold value higher when the fuel temperature is less than a predetermined value, as compared with the case where the fuel temperature is equal to or higher than a predetermined value.

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