JP5832145B2 - Fuel supply device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel supply device for an internal combustion engine that can suppress deterioration of a catalyst when the internal combustion engine is operated in an overspeed region.

  2. Description of the Related Art Conventionally, there has been known an apparatus that performs over-rotation fuel cut control for stopping fuel supply in order to suppress further increase in engine speed when the engine operating state is in an over-speed region. For example, in Patent Document 1, the engine speed is increased after an over-rotation fuel cut (fuel supply is stopped) in order to prevent an increase in engine exhaust gas temperature and improve an engine overheat prevention performance. When the fuel pressure becomes lower than the fuel cut return rotational speed for restarting the fuel supply, the fuel supply is restarted. In this fuel supply restart, the fuel supply amount is made lean according to at least one of the engine load and the vehicle speed.

  Normally, in the overspeed region, if the overspeed fuel cut and the fuel cut return (resumption of fuel supply) are continued intermittently, the temperature of the catalyst may increase excessively. This is because when the engine operating state is in the overspeed range, the air / fuel ratio is almost rich because the engine is operating at the output air / fuel ratio. On the other hand, when the overspeed fuel cut is being performed, Since the gas discharged from the engine is diluted with air, the air-fuel ratio of the gas flowing into the catalyst becomes leaner than the rich air-fuel ratio before that, and the temperature of the catalyst is raised. to cause.

  In particular, under operating conditions in which over-rotation fuel cut control is performed, there are many cases of high-rotation and high-load operation states, and the air-fuel ratio is often richer than the stoichiometric air-fuel ratio. In such an operation situation, when the over-rotation fuel cut and the fuel cut return are repeated, the air-fuel ratio of the gas flowing into the catalyst approaches the stoichiometric air-fuel ratio at which the temperature of the catalyst rises most. Since the fuel supply amount is made lean at the time of the fuel cut return in Patent Document 1, this is promoted. As described above, when the air-fuel ratio of the inflowing gas approximates the stoichiometric air-fuel ratio, when the temperature of the catalyst is raised, the catalyst is deteriorated or melted.

JP-A-9-195829

  Therefore, the present invention focuses on the above points and aims to protect the catalyst when the fuel supply is repeatedly stopped and restarted in the overspeed region.

That is, the fuel supply device for an internal combustion engine of the present invention is a fuel supply control device for controlling the supply of fuel to the internal combustion engine, in which the internal combustion engine includes a catalyst in the exhaust system, and detects the engine speed of the internal combustion engine. And a fuel supply means for supplying fuel, and the fuel supply means for stopping the fuel supply when the detected engine speed exceeds the first speed, Fuel supply control means for resuming fuel supply when the engine speed falls below a lower second rotational speed, and the fuel supply control means is leaner than the stoichiometric air-fuel ratio when resuming fuel supply in the overspeed region. The fuel supply means is controlled so as to supply the fuel so that the air / fuel ratio becomes the same, and the excessive increase in the temperature of the catalyst is suppressed, and the engine speed exceeds the first speed or the operating range is the engine Rotational speed is predetermined Above rolling speed and to the opening of the throttle valve becomes non constant over overspeed region, the air-fuel ratio is equal to or to continue the supply of the fuel quantity to be leaner than the stoichiometric air-fuel ratio.

  According to such a configuration, after restarting the fuel supply, by supplying the fuel so that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio, the combustion temperature becomes higher than the stoichiometric air-fuel ratio where the combustion temperature becomes the highest. The air-fuel ratio of the exhaust gas entering the catalyst becomes leaner than the stoichiometric air-fuel ratio, and the temperature of the catalyst can be reduced.

  The present invention is configured as described above, and the temperature of the catalyst can be reduced, so that the catalyst can be prevented from being melted and deterioration of the catalyst can be suppressed. In addition, since fuel is supplied at an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio when fuel supply is resumed, fuel efficiency can be improved, and drivability can be improved by suppressing torque fluctuations.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic structure explanatory drawing of the engine of embodiment of this invention. The flowchart which shows the control procedure of the embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  An engine 100 schematically showing the structure of one cylinder in FIG. 1 is for an automobile, and an intake system 1 is provided with a throttle valve 2 that opens and closes in response to an accelerator pedal (not shown). A bypass passage 3 that bypasses the valve 2 is provided, and a flow rate control valve 4 for controlling the idle speed is interposed in the bypass passage 3.

  This flow control valve 4 is opened at an opening based on the coolant temperature, which is the temperature of the engine 100, in idle speed control when the throttle valve 2 is almost fully closed. In this case, the lower the cooling water temperature is, the larger the opening degree is, and the flow control valve 4 is opened. This is to increase the resistance to rotational fluctuations at low temperatures with many mechanical losses. This flow control valve 4 is also open when the throttle valve 2 is open, that is, when the accelerator pedal is being operated.

  The intake system 1 is further provided with a fuel injection valve 5, and the fuel injection valve 5 and the flow rate control valve 4 are controlled by an electronic control device 6. As the engine itself, those widely known in this field can be used.

On the other hand, a three-way catalyst 21 for purifying the exhaust gas is attached to the exhaust system 20, and an O ₂ sensor 22 for detecting the air-fuel ratio of the exhaust gas is attached upstream of the three-way catalyst 21.

The electronic control device 6 is mainly configured by a microcomputer system including a central processing unit 7, a storage device 8, an input interface 9, and an output interface 11. The input interface 9 includes an intake pressure signal a output from an intake pressure sensor 13 for detecting the pressure in the surge tank 12, a rotation speed signal b output from a rotation speed sensor 14 for detecting the engine speed, a vehicle speed. The vehicle speed signal c output from the vehicle speed sensor 15 for detecting the engine speed, the IDL signal d output from the idle switch 16 for detecting the open / close state of the throttle valve 2, and the coolant temperature of the engine 100, which is the engine temperature, are detected. Therefore, a water temperature signal e output from the water temperature sensor 17 and an air-fuel ratio signal g output from the O ₂ sensor 22 are input. From the output interface 11, a drive signal f corresponding to the calculated fuel injection time is supplied to the fuel injection valve 5, and a control signal g based on the calculated duty ratio is supplied to the flow rate control valve 4. An ignition signal k is output to each spark plug 23.

  The electronic control unit 6 determines the opening time of the fuel injection valve 5 by using the intake pressure signal a output from the intake pressure sensor 13 and the rotation speed signal b output from the rotation speed sensor 14 as main information. A program for controlling the fuel injection valve 5 to inject fuel corresponding to the load from the fuel injection valve 5 into the intake system 1 is stored.

  Further, the electronic control unit 6 stops the fuel when the engine speed exceeds the overspeed fuel cut speed that is the first speed, and the second speed is lower than the overspeed fuel cut speed. The fuel supply is resumed when the rotational speed of the over-rotation fuel cut is less than the return speed, and when the fuel supply is resumed in the over-rotation region, the fuel ratio is set so that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio. An over-rotation fuel supply control program for supplying the engine is stored. The overspeed fuel supply control program is executed when the operating state of the engine 100 is in the overspeed region. The overspeed region is set on condition that the engine speed is equal to or higher than a predetermined speed and the opening degree of the throttle valve 2 is equal to or higher than a certain value. The control procedure of the over-rotation fuel supply control program will be described with reference to FIG.

  First, in step S1, the engine speed is detected. The engine speed is detected based on a speed signal b output from the speed sensor 14. Accordingly, the rotational speed sensor 14 and the electronic control unit 6 constitute a rotational speed detection means.

  In step S2, it is determined whether or not the detected engine speed exceeds the overspeed fuel cut speed. The over-rotation fuel cut speed is set according to the characteristics of the engine 100. If it is determined that the detected engine speed exceeds the overspeed fuel cut speed, step S3 is executed to stop the fuel supply.

  In step S3, after stopping the fuel supply, in step S4, the engine speed in the operation state in which the fuel supply stop is continued is detected. That is, once the fuel supply is stopped after exceeding the overspeed fuel cut speed, the fuel supply stop state is continued until the engine speed falls below the overspeed fuel cut return speed.

  In step S5, it is determined whether or not the engine speed detected in step S4 is lower than the overspeed fuel cut return speed. In step S5, steps S4 and S5 are repeated until the detected engine speed falls below the overspeed fuel cut return speed. On the other hand, if the detected engine speed falls below the overspeed fuel cut return speed, the process proceeds to step S6.

  In step S6, the fuel supply is resumed so that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio. After the fuel supply is resumed, the fuel injection amount becomes such that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio until the engine speed exceeds the over-rotation fuel cut speed or until the operating range is outside the over-speed range. Supply continues. In this embodiment, when the fuel supply is resumed, the fuel supply is performed so that the air-fuel ratio becomes leaner than the above-described stoichiometric air-fuel ratio, and is equal to or lower than the combustion temperature at the first fuel supply stop. The air / fuel ratio is set to the combustion temperature. The fuel injection valve 5 and the electronic control device 6 constitute fuel supply means and fuel supply control means.

  That is, since the engine 100 is operated in the overspeed region, the engine 100 is operated with an output air-fuel ratio richer than the stoichiometric air-fuel ratio until the fuel supply is stopped. In this case, the combustion temperature is lower than the combustion temperature at the stoichiometric air-fuel ratio, but is about the same as when the air-fuel ratio is lean or higher than when it is lean. Therefore, when resuming the fuel supply, by supplying the fuel so that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio and the combustion temperature equal to or lower than the combustion temperature at the first fuel supply stop time, The temperature of the gas flowing into the three-way catalyst 21 is reduced.

  In step S7, it is determined whether or not the operating state of engine 100 is an overspeed region. If it is determined that the operating state is the overspeed region, step S1 is executed again. Accordingly, when the operating state is the overspeed region, Steps S1 to S6 are repeatedly executed.

  In such a configuration, when engine 100 is operated in the overspeed region and the engine speed exceeds the overspeed fuel cut speed (in step S2 (“Yes”)), the fuel supply is stopped. Since the fuel supply is stopped until the rotational speed falls below the overspeed fuel cut return rotational speed, the engine speed gradually decreases during that time (steps S3 to S5). Since the fuel supply is continuously stopped until the fuel cut return rotational speed is below, a gas containing a large amount of oxygen flows into the three-way catalyst 21. Thereby, the inside of the three-way catalyst 21 The air-fuel ratio of the engine is temporarily close to the stoichiometric air-fuel ratio by being diluted with the inflowing gas from the rich air-fuel ratio before the fuel supply is stopped. Temperature of 21, inlet gas air-fuel ratio which has been retained therein by reaction with rich gas, temporarily increases and then descends in the early stages of the supply stop of the fuel.

  Thereafter, when the engine speed falls below the overspeed fuel cut return speed (“Yes” in step S5), the air-fuel ratio is leaner than the stoichiometric air-fuel ratio and is equal to or lower than the combustion temperature at the time of stopping the first fuel supply. Fuel is supplied so that the air-fuel ratio becomes the combustion temperature (step S6). As a result, the combustion temperature is lower than that in the case of the stoichiometric air-fuel ratio, and the air-fuel ratio of the gas flowing into the three-way catalyst 21 becomes leaner than the stoichiometric air-fuel ratio, so the reaction heat in the three-way catalyst 21 is also reduced. To do.

  In the conventional one, when the fuel supply is resumed at the output air-fuel ratio according to the operating state at that time, the three-way catalyst 21 in which the air-fuel ratio has become lean due to the stop of fuel supply has a rich air-fuel ratio. As the gas flows in, the temperature of the three-way catalyst 21 rises. However, in this embodiment, when the fuel supply stop and the supply restart are repeatedly performed in the overspeed region, the fuel supply restart is performed at an air fuel ratio leaner than the stoichiometric air fuel ratio and at the first time. By supplying the fuel so that the air-fuel ratio becomes a combustion temperature equal to or lower than the combustion temperature at the time of stopping the fuel supply, the air-fuel ratio in the three-way catalyst 21 changes to an air-fuel ratio leaner than the stoichiometric air-fuel ratio. As a result, since the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, it is possible to prevent the temperature of the three-way catalyst 21 from rising excessively.

  Therefore, deterioration of the three-way catalyst 21 due to heat can be suppressed, and in addition, the three-way catalyst 21 can be prevented from being melted. Further, in the operation state in which the fuel supply is stopped and restarted in the over-rotation region, the fuel temperature is reduced by restarting the fuel supply so that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio as described above. As a result, the heat load on engine 100 can be reduced.

  Further, when the fuel supply is resumed, the fuel is supplied such that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, so that the amount of fuel consumption can be reduced and the fuel consumption can be improved. In addition, when the fuel supply is resumed, the fuel is supplied so that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio, so that the torque becomes lower than when the air-fuel ratio is rich. During the repetition, the difference in torque can be reduced, and drivability can be improved.

  The present invention is not limited to the above embodiment.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  As an application example of the present invention, an internal combustion engine including a catalyst in an exhaust system can be cited.

DESCRIPTION OF SYMBOLS 5 ... Fuel injection valve 6 ... Electronic control unit 14 ... Speed sensor 20 ... Exhaust system 21 ... Three-way catalyst

Claims (1)

A fuel supply control device for controlling supply of fuel to an internal combustion engine, wherein the internal combustion engine includes a catalyst in an exhaust system,
A rotational speed detecting means for detecting the engine rotational speed of the internal combustion engine;
Fuel supply means for supplying fuel;
Fuel supply to the fuel supply means is stopped when the detected engine speed exceeds the first speed, and fuel supply is stopped when the detected engine speed falls below a second speed lower than the first speed. Fuel supply control means for restarting,
When the fuel supply control means restarts the fuel supply in the overspeed region, the fuel supply control means controls the fuel supply means to supply the fuel so that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio. While the temperature rise is suppressed, the engine speed is higher than the first speed , or until the operating range is outside the overspeed range where the engine speed is equal to or higher than the predetermined speed and the opening of the throttle valve is higher than a certain level. A fuel supply apparatus for an internal combustion engine that continues to supply an amount of fuel that makes the fuel ratio leaner than the stoichiometric air-fuel ratio.

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