JP6906856B2 - Internal combustion engine control device - Google Patents

Description

The present invention relates to a control device for controlling an internal combustion engine mounted on a vehicle or the like.

Conventionally, an internal combustion engine is provided with a fuel evaporative emission control device that captures fuel vapor evaporated in a fuel tank (see, for example, the following patent documents). A universal fuel evaporative emission control device is called a charcoal canister. It absorbs the generated fuel vapor on a canister filled with activated carbon, captures it, and sends the fuel vapor to the intake passage of the internal combustion engine for intake. It is mixed with the fuel and burned in the cylinder.

In addition to a recovery path for recovering fuel vapor in the fuel tank, the canister is connected to an atmosphere introduction path open to the atmosphere and a purge flow path that connects the canister to the downstream of the throttle valve in the intake passage of the internal combustion engine. is doing. In the process of purging the fuel vapor adsorbed on the canister, the control valve provided on the purge flow path is opened, and the intake negative pressure generated downstream of the throttle valve is used to take in the fuel vapor while taking in the outside air into the canister. Pull into the aisle.

While the internal combustion engine is stopped, the above-mentioned purging process cannot be executed, and fuel vapor accumulates in the canister. Immediately after the start of the internal combustion engine, a large amount of fuel vapor is stored in the canister, and it is necessary to release it into the intake passage as soon as possible.

The amount of fuel vapor released at one release opportunity, in other words, the length of the valve opening time of the control valve, is the concentration (or fuel component) of the fuel component contained in the purge gas flowing from the canister to the intake passage through the purge flow path. Set according to the amount of The concentration of fuel components in the purge gas increases as the amount of fuel vapor currently captured by the canister increases. Then, the concentration of the fuel component in the purge gas can be estimated based on the magnitude of the fluctuation of the air-fuel ratio of the exhaust gas flowing through the exhaust passage of the internal combustion engine, which occurs when the control valve is opened. As is well known, the air-fuel ratio can be measured via an air-fuel ratio sensor installed in the exhaust passage in advance.

Japanese Unexamined Patent Publication No. 2012-117415

However, when the amount of fuel injected from the injector to the cylinder increases or decreases due to individual differences in the internal combustion engine, aging, or other temporary factors, the concentration of fuel components in the purge gas, that is, the fuel vapor captured by the canister. The air-fuel ratio of the exhaust gas fluctuates regardless of the amount of the exhaust gas. As a result, if the amount of fuel vapor is underestimated, the opening time of the control valve in the purge process is shortened, and the fuel vapor cannot be sufficiently discharged from the canister.

The present invention has been made by paying attention to the above problems for the first time, and an object of the present invention is to sufficiently release fuel vapor from a canister immediately after the start of an internal combustion engine.

The present invention controls an internal combustion engine equipped with a fuel evaporative emission control device that captures fuel vapor and releases the captured fuel vapor to an intake passage connected to a cylinder of the internal combustion engine in a timely manner. Later, the cumulative flow rate of purge gas containing fuel vapor released from the canister of the fuel evaporative emission control device to the intake passage is estimated, and after the internal combustion engine is started, until the cumulative flow rate of purge gas reaches a predetermined value. The period constituted an internal combustion engine control device that sets a larger amount of purge gas released into the intake passage at one opportunity for purge gas release as compared to the subsequent period.

More specifically, the amount of fuel vapor currently captured in the canister of the fuel evaporative emission control device is estimated, and the fuel evaporative gas at one opportunity of releasing purge gas according to the estimated amount of fuel vapor. The length of the valve opening time of the control valve that opens and closes the purge flow path that connects the canister of the emission control device and the intake passage of the internal combustion engine is adjusted, and the cumulative flow rate of purge gas after the start of the internal combustion engine is a predetermined value. For the period until the fuel vapor reaches, the length of the valve opening time of the control valve for the same amount of fuel vapor is set to be larger than that after that.

Correct the fuel injection amount by referring to the output signal of the air-fuel ratio sensor that detects the air-fuel ratio of the exhaust gas flowing through the exhaust gas purification catalyst installed in the exhaust passage of the internal combustion engine, and learn the correction amount of the fuel injection amount. It is preferable that the correction amount of the fuel injection amount is not learned during the period from the start of the internal combustion engine until the cumulative flow rate of the purge gas reaches a predetermined value. Then, it becomes possible to preferentially execute the purging process of the fuel vapor immediately after the start of the internal combustion engine.

According to the present invention, the fuel vapor can be sufficiently released from the canister of the fuel evaporative emission control device immediately after the start of the internal combustion engine.

The figure which shows the schematic structure of the internal combustion engine and the control device of one Embodiment of this invention. The figure which illustrates the length of the valve opening time of the control valve set by the control device of the internal combustion engine of 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 into the cylinder 1 is provided in the vicinity of the intake port of 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 the application of the induced voltage generated by the ignition coil and induces a 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. 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 fuel evaporative emission control device adsorbs the fuel vapor evaporated in the fuel tank to the canister 35 filled with activated charcoal, captures the fuel vapor, sends the fuel vapor to the intake passage 3 at appropriate time, mixes it with the intake air, and mixes it with the intake air in the cylinder 1. It is a combustion process. The canister 35 is connected to a predetermined position (surge tank 33 or intake manifold 34) on the downstream side of the throttle valve 32 in the intake passage 3.

A purge VSV (Vacum Switching Valve) 36, which is a control valve for opening and closing the purge flow path, is provided on the purge flow path connecting the canister 35 and the intake passage 3. While the VSV 36 is open, the canister 35 and the intake passage 3 communicate with each other through the purge flow path, and the fuel vapor in the canister 35 enters the intake passage 3 due to the intake negative pressure generated downstream of the throttle valve 32. Be drawn in.

The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of 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.

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, and is a linear A / F sensor having an output characteristic proportional to the air-fuel ratio of the exhaust gas. There may be. The output characteristics of the O ₂ sensors 43 and 44 show a steep slope with a large rate of change in output with respect to the air-fuel ratio in the range near the stoichiometric air-fuel ratio, and asymptotically approach the low saturation value in the lean region where the air-fuel ratio is larger than that. In the rich region where the air-fuel ratio is small, a so-called Z characteristic curve that gradually approaches the high saturation value is drawn.

Further, the exhaust gas recirculation device 2 realizes a so-called high-pressure loop EGR, and communicates between 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 EGR passage 21, the EGR cooler 22 provided on the EGR passage 21, and the EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of the EGR gas flowing through the EGR passage 21 are elements. 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 (surge tank 33) downstream of the throttle valve 32 in the intake passage 3.

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 of ECU0 has a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle output from a crank angle sensor (engine rotation sensor) that detects the rotation angle of the crank shaft and the engine rotation speed. The signal b, the accelerator opening signal c output from the sensor that detects the accelerator pedal depression amount or the opening degree of the throttle valve 32 as the accelerator opening (so to speak, the required engine load ratio), and the temperature of the internal combustion engine are suggested. Cooling water temperature signal d output from the water temperature sensor that detects the cooling water temperature, intake air temperature / intake pressure signal output from the temperature / pressure sensor that detects the intake air temperature and intake pressure in the intake passage 3 (particularly, surge tank 33). e, the air-fuel ratio signal f output from the air-fuel ratio sensor 43 that detects the air-fuel ratio of the exhaust gas on the upstream side of the catalyst 41, and the air-fuel ratio sensor 44 that detects the air-fuel ratio of the exhaust gas on the downstream side of the catalyst 41. The air-fuel ratio signal g, the atmospheric pressure signal h output from the pressure sensor that detects the atmospheric pressure, and the like are input.

From the output interface of ECU 0, 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 for the EGR valve 23. The opening operation signal m and the like are output to the signal l and the purge VSV36.

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, obtains the engine speed, and fills the cylinder 1. Estimate the amount of intake air (amount of fresh air and amount of EGR gas). Then, various operating parameters such as the required fuel injection amount, fuel injection timing, fuel injection pressure, ignition timing, required EGR rate, etc. are determined based on the engine speed, the intake amount, and the like. The ECU 0 applies various control signals i, j, k, l, and m corresponding to the operation parameters via the output interface.

The fuel injection amount from the injector 11 is set according to the amount of intake air (fresh air amount) filled in the cylinder 1 in order to match the air-fuel ratio with the target air-fuel ratio near the stoichiometric air-fuel ratio. However, due to individual differences in the injector 11 and changes over time, even if the injector 11 is opened for a certain period of time, it is not guaranteed that the same amount of fuel will always be injected. Therefore, the ECU 0 learns the valve opening time of the injector 11 each time the ignition switch (or the ignition key) is operated from OFF to ON to cold start the internal combustion engine.

In learning the valve opening time of the injector 11, the injector 11 is opened for a time proportional to the amount of intake air charged in the cylinder 1, and fuel is injected from the injector 11. At this time, the purge VSV 36 and the EGR valve 23 are closed. Next, the air-fuel mixture obtained as a result is burned in the cylinder 1, and the air-fuel ratio of the generated exhaust gas is actually measured via the air-fuel ratio sensor 43.

Then, from the deviation between the measured air-fuel ratio and the target air-fuel ratio, the correction amount of the valve opening time of the injector 11, that is, the correction amount of the fuel injection amount is calculated. That is, if the measured air-fuel ratio is richer than the target air-fuel ratio, the correction amount is determined so as to shorten the valve opening time of the injector 11 and reduce the fuel injection amount. On the contrary, if the measured air-fuel ratio is leaner than the target air-fuel ratio, the correction amount is determined so as to extend the valve opening time of the injector 11 and increase the fuel injection amount. The absolute value of the correction amount increases as the absolute value of the deviation between the measured air-fuel ratio and the target air-fuel ratio increases. The correction amount is stored in the memory of ECU 0 and used in the subsequent fuel injection control.

However, the learning of the valve opening time of the injector 11 is not performed immediately after the cold start of the internal combustion engine. This is because it is necessary to purge the fuel vapor accumulated in the canister 35 while the internal combustion engine is stopped as soon as possible. As already mentioned, it is not allowed to open the purge VSV 36 while learning the valve opening time of the injector 11. On the flip side, the valve opening time of the injector 11 cannot be learned while purging the fuel vapor.

The ECU 0 of the present embodiment immediately opens the purge VSV 36 after the cold start of the internal combustion engine to start purging the fuel vapor adsorbed on the canister 35. At the same time, the concentration (or the amount of the fuel component) of the fuel component contained in the purge gas flowing from the canister 35 into the intake passage 3 through the purge flow path is estimated. The concentration of the fuel component in the purge gas increases as the amount of fuel vapor currently captured by the canister 35 increases. Therefore, estimating the concentration of the fuel component in the purge gas is equivalent to estimating the amount of fuel vapor captured by the canister 35.

In estimating the concentration of the fuel component in the purge gas, with the purge VSV36 opened, the injector 11 is opened for a time that takes into account the correction amount of the valve opening time learned in the past so that the air-fuel ratio matches the target air-fuel ratio. It valves and injects fuel from the injector 11. At this time, the EGR valve 23 is closed. Next, the resulting air-fuel mixture mixed with purge gas is burned in the cylinder 1, and the air-fuel ratio of the generated exhaust gas is actually measured via the air-fuel ratio sensor 43.

Then, the concentration of the fuel component contained in the purge gas is estimated from the deviation between the measured air-fuel ratio and the target air-fuel ratio. The deviation between the measured air-fuel ratio and the target air-fuel ratio is the ratio of the purge gas to the intake air charged in the cylinder 1 (partial pressure or the flow rate of the purge gas flowing through the purge flow path) and the concentration of the fuel component contained in the purge gas. Depends on. Since the fuel injection amount from the injector 11 is proportional to the amount of intake air (including the purge gas), the higher the concentration of the fuel component contained in the purge gas, the richer the air-fuel ratio. Therefore, ECU 0 calculates the concentration of the fuel component contained in the purge gas based on the ratio of the purge gas to the intake air and the deviation between the measured air-fuel ratio and the target air-fuel ratio.

The ratio of the purge gas to the intake air can be estimated based on the engine speed at that time, the opening degree of the throttle valve 32, the intake pressure, the atmospheric pressure, the opening degree of the purge VSV36, and the like. Map data that defines the relationship between the engine speed, the opening degree of the throttle valve 32, the intake pressure, the atmospheric pressure, the opening degree of the purge VSV36, and the ratio of the purge gas to the intake air is stored in the memory of the ECU 0 in advance. There is. The ECU 0 searches the map using the current engine speed, the opening degree of the throttle valve 32, the intake pressure, the atmospheric pressure, the opening degree of the purge VSV36, and the like as keys, and obtains the ratio of the purge gas to the intake air.

In the fuel vapor purging process after the cold start of the internal combustion engine, the purge VSV 36 is opened and closed a plurality of times, that is, the purge gas containing the fuel vapor is discharged from the canister 35 to the intake passage 3 in a plurality of times. Then, the ECU 0 of the present embodiment purges at one purge gas discharge opportunity until the cumulative flow rate of the purge gas discharged from the canister 35 to the intake passage 3 reaches a predetermined value after the cold start of the internal combustion engine. The length of the valve opening time of VSV36 is set to be larger. Prolonging the valve opening time of the purge VSV 36 means increasing the amount of purge gas discharged from the canister 35 to the intake passage 3 at one purge gas release opportunity.

FIG. 2 shows the concentration of the fuel component in the purge gas estimated at the previous purge gas release opportunity, and the accumulation of the purge gas flowing through the purge flow path between the cold start of the internal combustion engine and the previous purge gas release opportunity. The relationship between the flow rate and the length of the valve opening time of the purge VSV36 at the next purge gas discharge opportunity is illustrated. As shown in FIG. 2, the valve opening time of the purge VSV36 at the next purge gas release opportunity is longer as the concentration of the fuel component in the purge gas is higher, and is longer as the cumulative flow rate of the purge gas is smaller.

The flow rate of the purge gas flowing through the purge flow path is determined from the amount of intake air filled in the cylinder 1 and the ratio of the purge gas to the intake air. By integrating (or time-integrating) the flow rate of the purge gas, the cumulative flow rate of the purge gas after the cold start of the internal combustion engine can be calculated.

When opening and closing the purge VSV 36, the flow rate of the purge gas flowing into the intake passage 3 through the purge flow path is gradually increased or decreased by gradually expanding or contracting the opening degree thereof. Then, by the feedback control of the air-fuel ratio with reference to the output signals of the air-fuel ratio sensors 43 and 44, the air-fuel ratio of the air-fuel mixture and the exhaust gas does not deviate significantly from the target air-fuel ratio.

After the cold start of the internal combustion engine, the ECU 0 does not learn the correction amount of the valve opening time of the injector 11 until the cumulative flow rate of the purge gas reaches a predetermined value, and the fuel vapor accumulated in the canister 35 is not executed. Priority is given to the purging process of. Then, after the cumulative flow rate of the purge gas reaches a predetermined value, the learning of the correction amount of the valve opening time of the injector 11 is executed.

In the present embodiment, the internal combustion engine is controlled by the fuel evaporative emission control devices 35 and 36 that capture the fuel vapor and release the captured fuel vapor to the intake passage 3 connected to the cylinder 1 of the internal combustion engine in a timely manner. After the internal combustion engine is started, the cumulative flow rate of the purge gas containing the fuel vapor released from the canister 35 of the fuel evaporative emission control devices 35 and 36 to the intake passage 3 is estimated, and after the internal combustion engine is started, the purge gas of the purge gas is estimated. During the period until the cumulative flow rate reaches a predetermined value, the control device 0 of the internal combustion engine that sets the amount of purge gas released to the intake passage 3 at one opportunity of discharge of purge gas is larger than that after that. Configured.

The control device 0 of the internal combustion engine of the present embodiment estimates the amount of fuel vapor currently captured by the canister 35 by estimating the concentration of the fuel component contained in the purge gas flowing through the purge flow path. Then, according to the estimated fuel vapor amount, the amount of purge gas released to the intake passage 3 at one opportunity of discharge of purge gas, more specifically, the length of the valve opening time of the control valve 36 is increased or decreased. As shown in FIG. 2, if the amount of fuel vapor captured in the canister 35 is the same, the smaller the cumulative flow rate of the purge gas after the start of the internal combustion engine, the more control at the opportunity of one purge gas release. The valve opening time of the valve 36 becomes long, and the amount of purge gas released becomes large.

According to the present embodiment, the fuel vapor can be sufficiently released from the canister 35 of the fuel evaporative emission control devices 35 and 36 to the intake passage 3 of the internal combustion engine immediately after the start of the internal combustion engine. Even if a large amount of fuel vapor is stored in the canister 35 while the internal combustion engine is stopped, the fuel vapor can be quickly purged, so that leakage of the fuel vapor to the outside can be reliably suppressed.

The present invention is not limited to the embodiments described in detail above. For example, in the above embodiment, the amount of purge gas released from the canister 35 to the intake passage 3 is increased or decreased by extending or shortening the length of the valve opening time of the control valve 36 at one purge gas release opportunity. Along with this, or in place of this, the amount of purge gas released from the canister 35 to the intake passage 3 can also be increased or decreased by increasing or decreasing the opening (maximum value) of the control valve 36 at one purge gas release opportunity. It is possible to make it. Needless to say, if the opening degree of the control valve 36 is further increased, the amount of purge gas released increases, and if the opening degree of the control valve 36 is further reduced, the amount of purge gas released decreases.

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

0 ... Control device (ECU)
1 ... Cylinder 11 ... Injector 3 ... Intake passages 35, 36 ... Fuel evaporative emission control device (canister, control valve (purge VSV))
4 ... Exhaust passage 41 ... Catalyst 43 ... Air-fuel ratio sensor

Claims (2)

It controls an internal combustion engine equipped with a fuel evaporative emission control device that captures fuel vapor and releases the captured fuel vapor to the intake passage connected to the cylinder of the internal combustion engine in a timely manner.
After starting the internal combustion engine, the cumulative flow rate of purge gas containing fuel vapor released from the canister of the fuel evaporative emission control device into the intake passage is estimated.
The period from the start of the internal combustion engine until the cumulative flow rate of the purge gas reaches a predetermined value sets the amount of the purge gas released to the intake passage at one opportunity of the purge gas to be released larger than that after that. It is a thing
Estimate the amount of fuel vapor currently captured in the canister of the fuel evaporative emission control device, and according to the estimated amount of fuel vapor, with the canister of the fuel evaporative emission control device at the opportunity of one purge gas release We decided to adjust the length of the valve opening time of the control valve that opens and closes the purge flow path that communicates with the intake passage of the internal combustion engine.
The period from the start of the internal combustion engine until the cumulative flow rate of the purge gas reaches a predetermined value sets the length of the valve opening time of the control valve for the same amount of fuel vapor to be larger than that after that. Internal combustion engine control device. Correct the fuel injection amount by referring to the output signal of the air-fuel ratio sensor that detects the air-fuel ratio of the exhaust gas flowing through the exhaust gas purification catalyst installed in the exhaust passage of the internal combustion engine, and learn the correction amount of the fuel injection amount. To do
After the start of the internal combustion engine, the period until a flow rate of accumulation of the purge gas reaches a predetermined value, the control device for an internal combustion engine according to claim 1, wherein not performing learning of the correction amount of the fuel injection amount.

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