JP3620210B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine, and more specifically, an internal combustion engine in which fuel vapor generated in a fuel tank is sucked into the intake side of the internal combustion engine (engine) and burned to control the operating state of the internal combustion engine. The present invention relates to an engine control device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is an apparatus for processing fuel vapor generated in a fuel tank as an apparatus provided accompanying an internal combustion engine (engine). This processing apparatus collects fuel vapor generated in the fuel tank in a canister, and purges the collected fuel from the canister to the intake passage of the engine as necessary. The fuel purged into the intake passage is supplied to the combustion chamber of the engine for combustion.
[0003]
On the other hand, there is a device for controlling an air-fuel ratio related to a mixture of air and fuel supplied to a combustion chamber in an engine. In this type of control device, the computer calculates a required air-fuel ratio that changes according to the engine speed, load state, warm-up state, and the like. The computer controls the air-fuel ratio of the air-fuel mixture by correcting the amount of fuel supplied to the combustion chamber by the fuel supply device so that the actual air-fuel ratio detected by the sensor matches the calculated required air-fuel ratio. To do. By this control, various characteristics such as engine output characteristics, exhaust characteristics, and drivability are optimized for various operating conditions.
[0004]
By the way, in order to adapt the air-fuel ratio control to the engine equipped with the fuel vapor processing apparatus as described above, the fuel by the purge is added to the original air-fuel mixture supplied to the combustion chamber. It is necessary to perform air-fuel ratio control in consideration of fuel.
[0005]
An air-fuel ratio control apparatus for an internal combustion engine disclosed in Japanese Patent Laid-Open No. 5-288107 has been proposed as an air-fuel ratio control that allows for a fuel component by purging. In this control device, the evaporated fuel generated in the fuel tank is adsorbed to the canister, and the evaporated fuel adsorbed to the canister is purged together with air to the intake side of the internal combustion engine via the purge valve. At this time, the oxygen concentration in the exhaust gas is detected by an oxygen sensor as an air-fuel ratio detecting means provided in the exhaust pipe, and this detected value is output as an air-fuel ratio feedback value. At this time, the purge rate is changed by the purge valve so that the air-fuel ratio feedback value output from the oxygen sensor is in a predetermined region. Then, the concentration of the evaporated fuel sucked into the internal combustion engine through the purge valve is detected based on the purge rate before and after the purge rate is changed and the air-fuel ratio feedback value, and the detected concentration is used for air-fuel ratio control. Use.
[0006]
Further, there is an evaporative fuel control device for an internal combustion engine disclosed in Japanese Patent Application Laid-Open No. 7-119560 as one that performs air-fuel ratio control in consideration of the fuel content by purge. In this control device, the concentration of evaporated fuel sucked into the intake passage is detected by a concentration sensor as an evaporated fuel concentration detection means provided near the branch point between the purge passage and the intake passage, and the detected concentration is controlled by air-fuel ratio control. Used for.
[0007]
[Problems to be solved by the invention]
However, the air-fuel ratio control apparatus for an internal combustion engine disclosed in Japanese Patent Application Laid-Open No. 5-288107 detects the concentration of evaporated fuel by using an air-fuel ratio feedback value detected by an oxygen sensor on the exhaust side. For this reason, since the concentration of the evaporated fuel cannot be detected unless the purge is repeated several times, a delay occurs, and good air-fuel ratio control cannot be performed immediately after the start of the purge control.
[0008]
Further, as an apparatus for performing air-fuel ratio control in anticipation of the fuel component by purging, an evaporative fuel control device for an internal combustion engine disclosed in Japanese Patent Laid-Open No. 7-119560 detects the concentration of evaporative fuel by a concentration sensor on the intake side. However, the responsiveness of the concentration sensor itself is low, a delay occurs, and good air-fuel ratio control cannot be performed immediately after the start of purge.
[0009]
The present invention has been made in view of the above-described circumstances, and its purpose is to detect the concentration of fuel vapor adsorbed in the canister at the time of purge control or before purge control is performed and immediately after the start of purge control. It is an object of the present invention to provide a control device for an internal combustion engine that makes it possible to perform stable air-fuel ratio control.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is a canister for storing fuel vapor generated in a fuel tank, and a purge for controlling the amount of fuel vapor purged from the canister to an intake system of an internal combustion engine. A control valve; an injector for supplying fuel to the intake system of the internal combustion engine by injecting fuel; a purge concentration calculating means for calculating a purge concentration of fuel vapor purged by the purge control valve; and a purge concentration A control device for an internal combustion engine, comprising: control means for controlling an air-fuel ratio by adjusting an amount of fuel supplied from an injector based on a purge concentration calculated by a calculation means and an operating state of the internal combustion engine, The purge concentration calculation means calculates the intake pressure during the purge execution and the intake pressure during the purge non-execution operation state that is the same as the operation state during the purge execution. As its gist to calculate the purge concentration based on the pressure difference.
[0011]
According to a second aspect of the present invention, in the control apparatus for an internal combustion engine according to the first aspect of the invention, an intake pressure sensor for detecting the intake pressure of the internal combustion engine is provided, and the purge concentration calculating means is detected by the intake pressure sensor. The gist is to calculate the purge concentration based on the intake pressure.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an internal combustion engine control apparatus according to the present invention embodied in an automobile will be described below in detail with reference to the drawings.
[0015]
(First embodiment)
A control apparatus for an internal combustion engine according to a first embodiment will be described with reference to FIGS.
FIG. 1 is a schematic configuration diagram showing a control device for an internal combustion engine. A gasoline engine system mounted on an automobile includes a fuel tank 1 containing fuel. This tank 1 has an inlet pipe 2 for use in refueling. The pipe 2 includes an oil filler port 2a at the tip. When the tank 1 is supplied with fuel, an oil supply nozzle (not shown) is inserted into the oil supply port 2a. A cap 3 is detachably attached to the fuel filler opening 2a.
[0016]
The electric fuel pump 4 provided in the tank 1 incorporates a motor (not shown). The pump 4 sucks up and discharges the fuel in the tank 1 when the motor is driven by energization. The amount of fuel discharged from the pump 4 is determined based on the current value supplied to the motor, that is, the rotational speed of the motor.
[0017]
A fuel line 5 extending from the pump 4 is connected to a delivery pipe 6. A plurality of injectors (only one is shown in the figure) 7 provided on the pipe 6 is arranged corresponding to each cylinder (not shown) of the internal combustion engine (engine) 8. Each injector 7 is a nozzle with an electromagnetic valve, which opens when energized and closes when energized is interrupted. The delivery pipe 6 is connected to a return pipe 9 that returns excess fuel into the fuel tank 1.
[0018]
An intake passage 10 connected to the engine 8 guides outside air (air) to each cylinder. The intake passage 10 includes an air cleaner 11 and a surge tank 10a. Air purified through the air cleaner 11 is introduced into the intake passage 10.
[0019]
The throttle valve 12 provided in the intake passage 10 selectively opens and closes the passage 10 by operating by operating an accelerator pedal (not shown). By adjusting the opening degree (throttle opening degree) VTA of the valve 12, the air amount (intake amount) taken into each cylinder through the intake passage 10 is adjusted.
[0020]
By operating the pump 4, the fuel in the tank 1 is discharged to the line 5. The discharged fuel is pumped to the delivery pipe 6 through the line 5 and further distributed to the injectors 7. The distributed fuel is injected by each injector 7. A mixture of injected fuel and air is supplied to each cylinder for combustion. Due to this combustion, the crankshaft 8 a is rotated and power is obtained for the engine 8. Exhaust gas after combustion is discharged from each cylinder through the exhaust passage 12 to the outside.
[0021]
The canister 14 collects fuel vapor generated in the tank 1 through the vapor line 13. The canister 14 contains an adsorbent 15 made of a plurality of activated carbons. The first atmospheric valve 16 provided in the canister 14 is a check valve. The atmospheric valve 16 opens when the internal pressure of the canister 14 is smaller than the atmospheric pressure, allows the introduction of outside air (atmospheric pressure) to the canister 14 and prevents the gas flow in the opposite direction. A pipe 17 extending from the atmospheric valve 16 is connected to the air cleaner 11. Accordingly, the outside air purified by the air cleaner 11 is introduced into the canister 14.
[0022]
The second atmospheric valve 18 provided in the canister 14 is a check valve. The atmospheric valve 18 opens when the internal pressure of the canister 14 becomes larger than the atmospheric pressure, allows the gas (internal pressure) to be derived from the canister 14 to the outlet pipe 19, and prevents the gas flow in the opposite direction.
[0023]
A vapor control valve 20 provided in the canister 14 controls fuel vapor flowing from the tank 1 to the canister 14. The control valve 20 opens based on the difference between the internal pressure on the tank 1 side including the vapor line 13 (tank side internal pressure) and the internal pressure on the canister 14 side (canister side internal pressure). When the control valve 20 is opened, fuel vapor is allowed to flow into the canister 14. That is, the control valve 20 opens when the internal pressure on the canister side is substantially the same as the atmospheric pressure, and the internal pressure is larger than the internal pressure on the tank side, and allows the fuel vapor to flow into the canister 14. In addition, the control valve 20 allows gas flow from the canister 14 to the tank 1 when the canister side internal pressure is larger than the tank side internal pressure.
[0024]
A purge line 21 extending from the canister 14 is connected to the surge tank 10a. The canister 14 adsorbs and collects only the fuel component in the fuel vapor introduced through the vapor line 14 by the adsorbent 15, and when the atmospheric valve 18 is opened, only the gas not containing the fuel component is collected to the outside. Discharge. An intake negative pressure generated in the intake passage 10 acts on the purge line 21 during operation of the engine 8. At this time, the fuel collected in the canister 14 or the fuel introduced from the tank 1 into the canister 14 and before being adsorbed by the adsorbent 15 is purged to the intake passage 10 through the purge line 21.
[0025]
A purge control valve 22 provided in the purge line 21 adjusts the amount of fuel passing through the line 21 as necessary. The control valve 22 is an electromagnetic valve that moves the valve body upon receiving an electric signal (duty signal), and its opening degree is duty-controlled.
[0026]
An intake air temperature sensor 31 provided in the vicinity of the air cleaner 11 detects the temperature (intake air temperature) THA of air sucked into the intake passage 10 and outputs a signal corresponding to the magnitude.
[0027]
The intake pressure sensor 32 provided in the surge tank 10a detects the pressure (intake pressure) Pim in the intake passage 10 and outputs a signal corresponding to the magnitude.
A throttle sensor 33 provided in the vicinity of the throttle valve 12 detects the throttle opening degree VTA and outputs a signal corresponding to the magnitude. This sensor 33 incorporates a known idle switch (not shown). This switch is turned “ON” when the valve 12 is fully closed, and outputs an idle signal IDL indicating that the valve 12 is fully closed.
[0028]
A water temperature sensor 34 provided in the engine 8 detects the temperature (cooling water temperature) THW of the cooling water flowing through the engine 8 and outputs a signal corresponding to the magnitude thereof.
A rotational speed sensor 35 provided in the engine 8 detects a rotational speed (engine rotational speed) NE of the crankshaft 8a and outputs a signal corresponding to the magnitude thereof.
[0029]
The oxygen sensor 36 provided in the exhaust passage 12 detects the oxygen concentration Ox in the exhaust gas flowing through the exhaust passage 12 and outputs a signal corresponding to the magnitude. The sensor 36 detects oxygen in the air-fuel mixture supplied to each cylinder of the engine 8 as a specific component.
[0030]
The atmospheric pressure sensor 37 detects the atmospheric pressure Pa and outputs a signal corresponding to the magnitude.
An electronic control unit (ECU) 41 constitutes a purge concentration calculation unit and a control unit. The ECU 41 is connected to the various sensors 31 to 37, the fuel pump 4, the injector 7, and the purge control valve 22 described above. ECU41 inputs the signal output from various sensors 31-37. Based on the input signal, the ECU 41 controls the members 4, 7, and 22 in order to execute fuel injection control including air-fuel ratio control, fuel purge control, and purge concentration calculation processing, respectively.
[0031]
The fuel injection control is to control the amount of fuel injected from each injector 7 by controlling the valve opening time of each injector 7 in accordance with the operating state of the engine 8. The air-fuel ratio control is to control the amount of fuel injected from each injector 7 so that the air-fuel ratio of the air-fuel mixture supplied to each cylinder becomes a target air-fuel ratio suitable for the operating state of the engine 8.
[0032]
The fuel purge control is to control the purge of fuel from the canister 14 to the intake passage 10 by controlling the purge control valve 22 according to the operating state of the engine 8. Here, the fuel purged into the intake passage 10 is added to a normal air-fuel mixture formed based on the fuel injected from each injector 7 and changes its air-fuel ratio from the target value. Therefore, in order to prevent the air-fuel ratio of the air-fuel mixture from deviating from the target value due to the purge fuel, the ECU 41 executes air-fuel ratio control in consideration of the fuel amount due to the purge.
[0033]
As shown in the block circuit diagram of FIG. 2, the ECU 41 includes a central processing unit (CPU) 42, a read only memory (ROM) 43, a random access memory (RAM) 44, and a backup RAM 45. The ECU 41 includes these parts 42 to 45, an external input circuit 46 and an external output circuit 47 connected by a bus 48.
[0034]
Here, the ROM 43 stores in advance a control program for executing the various controls described above, a basic purge concentration map used for purge concentration calculation, and the like. This basic purge concentration map is created based on the intake pressure Pim, the engine speed NE, and the throttle opening VTA when the purge control is not performed. The RAM 44 temporarily stores the calculation result of the CPU 42 and the like. The backup RAM 45 stores previously stored data. The external input circuit 46 includes a buffer, a waveform shaping circuit, a hard filter (a circuit composed of an electric resistor and a capacitor), an A / D converter, and the like. The external output circuit 47 includes a drive circuit and the like. Various sensors 31 to 37 are connected to an external input circuit 46. Each member 4, 7, 22 is connected to an external output circuit 47.
[0035]
CPU42 reads the signal from the various sensors 31-37 input via the external input circuit 46 as an input value. The CPU 42 controls the members 4, 7, and 22 in order to execute the various controls described above based on these input values.
[0036]
FIG. 3 is a flowchart showing a “fuel purge control routine” regarding the processing contents of the fuel purge control. The ECU 41 periodically executes this routine at predetermined intervals when the engine 8 is operated.
[0037]
In step 100, the ECU 41 is detected by various sensors 32, 33, and 35, and reads values relating to the intake pressure Pim, the throttle opening VTA, the idle signal IDL, and the engine speed NE reflecting the operating state of the engine 8 as input values. .
[0038]
In step 110, the ECU 41 determines whether a condition for performing the fuel purge is satisfied. For example, as the purge condition, the intake pressure Pim and the engine rotational speed NE are each equal to or higher than a predetermined value, and a sufficient intake negative pressure is generated in the surge tank 10a.
[0039]
In step 110, if the purge condition is not satisfied, in step 120, the ECU 41 closes the purge control valve 22 in order to prohibit the fuel purge. Subsequently, since the fuel purge is prohibited, in step 130, the ECU 41 sets the purge flag XPG to “0”, and the subsequent processing is once ended.
[0040]
In step 110, if the purge condition is satisfied, in step 140, the ECU 41 calculates the value of the target opening degree DPG based on the values of the intake pressure Pim and the engine speed NE. This target opening degree DPG is a duty signal supplied to the valve 22 in order to duty-control the opening degree of the purge control valve 22. The ECU 41 calculates the value of the target opening degree DPG by referring to predetermined function data using the target opening degree DPG, the intake pressure Pim, and the engine speed NE as parameters. By determining the target opening degree DPG, the amount of fuel purged from the canister 14 to the intake passage 10 (fuel concentration) is determined.
[0041]
In step 150, the ECU 41 controls the purge control valve 22 based on the calculated target opening degree DPG in order to allow fuel purge. Subsequently, since the fuel purge is permitted, in step 160, the ECU 41 sets the purge flag XPG to “1”, and temporarily terminates the subsequent processing.
[0042]
FIG. 4 is a flowchart showing a “purge concentration calculation routine” during fuel purge control. The ECU 41 periodically executes this routine at predetermined intervals when the engine 8 is operated.
[0043]
In step 200, the ECU 41 purges the values related to the intake pressure Pim (n), the throttle opening VTA (n), the engine rotational speed NE (n), and the atmospheric pressure Pa detected by the various sensors 32, 33, 35, and 37. These are read as input values before control and stored in the RAM 44.
[0044]
In step 210, the ECU 41 determines whether purge control has been performed. If it is determined in step 210 that the purge control is not performed, the process returns to step 200.
[0045]
If it is determined in step 210 that the purge control has been performed, in step 220, the ECU 41 determines that the intake pressure Pim (n + 1), the throttle opening VTA (n + 1), the engine speed NE (n + 1), and the atmospheric pressure Pa after the purge control. The value related to is read.
[0046]
In step 230, the ECU 41 calculates the intake pressure change ΔPim, the rotational speed change ΔNE, and the opening change ΔVTA by subtracting the values of the parameters before the purge control from the values of the parameters after the purge control.
[0047]
In step 240, the ECU 41 calculates the purge concentration based on the intake pressure change ΔPim and the intake pressure change ΔPim (ΔNE, ΔVTA) after the purge control. The intake pressure change ΔPim (ΔNE, ΔVTA) is obtained from the basic purge concentration map, and is a change in the intake pressure corresponding to the rotational speed change ΔNE and the opening change ΔVTA when the purge control is not performed. .
[0048]
In the present embodiment, the ECU 41 that executes this routine corresponds to a purge concentration calculation unit.
FIG. 5 is a flowchart showing another “purge concentration calculation routine” at the time of fuel purge control, and shows a case where the change in the engine speed NE or the throttle opening VTA is large.
[0049]
In step 250, the ECU 41 reads values relating to the intake pressure Pim (n), the throttle opening VTA (n), the engine rotational speed NE (n), and the atmospheric pressure Pa as input values before the purge control, and stores them in the RAM 44. To do.
[0050]
In step 255, the ECU 41 determines whether purge control has been performed. If it is determined in step 210 that the purge control is not performed, the process returns to step 250.
[0051]
If it is determined in step 255 that the purge control has been performed, a delay of Xms (milliseconds) is delayed in step 260. In step 265, the ECU 41 controls the intake pressure Pim (n + 1), the throttle opening VTA (n + 1) after the purge control, The values relating to the engine speed NE (n + 1) and the atmospheric pressure Pa are read.
[0052]
In step 270, the ECU 41 calculates the intake pressure change ΔP by subtracting the intake pressure Pim (map) from the intake pressure Pim (n + 1) after the purge control. The intake pressure Pim (map) is obtained from the basic purge concentration map, and is an intake pressure corresponding to the rotational speed NE and the throttle opening VTA when the purge control is not performed.
[0053]
In step 275, the ECU 41 calculates the purge concentration based on the intake pressure change ΔP and the basic purge concentration map.
FIG. 6 is a flowchart showing a “fuel injection control routine” regarding the processing content of the fuel injection control. The ECU 41 periodically executes this routine at predetermined intervals when the engine 8 is operated.
[0054]
In step 300, the ECU 41 reads values relating to various parameters THA, Pim, VTA, IDL, THW, NE, Ox, which are detected by the various sensors 31 to 36 and reflect the operating state of the engine 8 as input values.
[0055]
In step 305, the ECU 41 calculates the value of the basic injection amount TAUb based on the values of the intake pressure Pim and the engine speed NE. This basic injection amount TAUb is a value with time as a unit. The ECU 41 calculates the value of the basic injection amount TAUb by referring to predetermined function data using the basic injection amount TAUb, the intake pressure Pim, and the engine speed NE as parameters. In the present embodiment, the ECU 41 that executes the processing of step 305 corresponds to a calculation means for calculating a basic injection amount TAUb that should be basically set according to the operating state of the engine 8.
[0056]
In step 310, the ECU 41 calculates the value of the air-fuel ratio correction coefficient FAF related to the air-fuel ratio A / F of the air-fuel mixture based on the value of the oxygen concentration Ox. The ECU 41 determines whether the air-fuel ratio A / F of the air-fuel mixture is rich or lean based on the value of the oxygen concentration Ox, and corrects the air-fuel ratio A / F to be a predetermined stoichiometric air-fuel ratio (stoichiometric) value. The coefficient FAF is determined. Therefore, the value of the correction coefficient FAF indicates that the air-fuel ratio A / F is rich or lean. In the present embodiment, the ECU 41 that executes the process of step 310 corresponds to a calculating means for calculating a correction coefficient FAF for making the air-fuel ratio A / F of the air-fuel mixture stoichiometric.
[0057]
In step 315, the ECU 41 calculates the value of the temperature correction coefficient KTH based on the values of the intake air temperature THA and the coolant temperature THW. The ECU 41 calculates the value of the temperature correction coefficient KTH by referring to predetermined function data using the temperature correction coefficient KTH, the intake air temperature THA, and the coolant temperature THW as parameters. In the present embodiment, the ECU 41 that executes the process of step 315 corresponds to a calculation means for calculating a temperature correction coefficient KTH for correcting the basic injection amount TAUb according to the temperature state of the engine 8.
[0058]
In step 320, the ECU 41 calculates the final value of the fuel injection amount TAU by multiplying the value of the basic injection amount TAUb by the values of the air-fuel ratio correction coefficient FAF and the temperature correction coefficient KTH. This fuel injection amount TAU is a value in units of time, and is a value that determines the valve opening time of the injector 7. In the present embodiment, the ECU 41 that executes the process of step 320 corresponds to a calculation means for calculating the final fuel injection amount TAU by correcting the basic injection amount TAUb with both correction coefficients FAF and KTH.
[0059]
In step 330, the ECU 41 determines whether or not the purge flag XPG is “1”. If the flag XPG is “0”, the fuel purge is prohibited, so the ECU 41 proceeds to step 340. If the flag XPG is “1”, the fuel purge is allowed, and the ECU 41 proceeds to step 350. In the present embodiment, the ECU 41 that executes the process of step 330 corresponds to a determination means for determining that the fuel purge is executed and the fuel is supplied to the engine 8.
[0060]
In step 340 after the transition from step 330, the fuel purge is prohibited. Therefore, the ECU 41 executes fuel injection based on the value of the fuel injection amount TAU. That is, the ECU 41 determines whether or not it is time to inject fuel for each cylinder based on the pulse signal related to the engine speed NE. When the injection timing arrives, the ECU 41 performs fuel injection by opening each injector 7 for a required time based on the calculated value of the fuel injection amount TAU. After completing this process, the ECU 41 once terminates the subsequent processes. In the present embodiment, the ECU 41 that executes the process of step 340 corresponds to an execution means for executing fuel injection at a predetermined injection timing.
[0061]
On the other hand, since the fuel purge is permitted in step 350 after shifting from step 330, the ECU 41 determines whether or not the air-fuel ratio A / F is rich. When the influence of the fuel purge on the air-fuel mixture is large, it indicates that the air-fuel ratio A / F is richer than the stoichiometry. The ECU 41 determines the air-fuel ratio A / F based on the calculated value of the air-fuel ratio correction coefficient FAF. When the air-fuel ratio A / F is not rich, that is, when the air-fuel ratio A / F is stoichiometric or lean, the ECU 41 executes the process of step 340 described above, and once ends the subsequent process. If the air-fuel ratio A / F is rich, the ECU 41 proceeds to step 360. In the present embodiment, the ECU 41 that executes the process of step 350 corresponds to a determination unit that determines whether the air-fuel ratio A / F is rich under the influence of the fuel purge.
[0062]
In step 360, the ECU 41 subtracts a value TD based on the calculated purge concentration from the calculated fuel injection amount TAU, thereby calculating the value of the subtracted injection amount TAUD. This value TD is a value in units of time, like the fuel injection amount TAU. In the present embodiment, the ECU 41 that executes the process of step 360 corresponds to a calculation means for correcting the decrease in the calculated fuel injection amount TAU by the value TD when the fuel purge is being executed.
[0063]
In step 370, the ECU 41 executes fuel injection based on the value of the subtracted injection amount TAUD. That is, when it is time to inject fuel for each cylinder, the ECU 41 performs fuel injection by opening each injector 7 for a required time based on the calculated post-subtraction injection amount TAUD. .
[0064]
Thus, the amount of fuel to be supplied from each injector 7 to each cylinder is adjusted according to the operating state of the engine 8 by adjusting the valve opening time of the injector 7. On the other hand, the fuel vapor generated in the tank 1 is collected in the canister 14 without being released into the atmosphere. In the fuel purge control, when a condition for performing the fuel purge is satisfied, the ECU 41 opens the purge control valve 22 with a required opening degree. As a result, the fuel collected in the canister 14 or the fuel vapor introduced into the canister 14 is purged to the intake passage 10 through the purge line 21 and supplied to each cylinder of the engine 8. This purge fuel is added to the original air-fuel mixture composed of the fuel injected from the injector 7 and air as described above, and is used for combustion in the engine 8.
[0065]
For this reason, in air-fuel ratio control, it is necessary to perform control in anticipation of the amount of purge fuel supplied to the engine 8. In the present embodiment, when the fuel purge is executed, the ECU 41 determines that, and first, the intake pressure before and after the start of the operation of the purge control valve 22 is detected by the intake pressure sensor 32 provided in the surge tank 10a. Then, the purge concentration of the fuel vapor is calculated based on the intake pressure change. Then, the ECU 41 decreases the value TD corresponding to the purge concentration calculated from the fuel injection amount TAU calculated based on the operating state of the engine 8. Thereby, the amount of fuel injected from each injector 7 is reduced. For this reason, the amount of fuel supplied to the engine 8 is not excessive due to the purged fuel. As a result, the air-fuel ratio A / F of the air-fuel mixture in the engine 8 can be suppressed from becoming rich, and the air-fuel ratio A / F can be stabilized immediately after the start of the fuel purge. In this sense, it is possible to prevent the drivability and emission of the engine 8 from deteriorating.
[0066]
In the present embodiment, when the fuel purge is performed, the amount of fuel injected from the injector 7 is reduced. Therefore, the amount of fuel consumed in the engine 8 can be reduced, and the fuel consumption can be improved.
[0067]
In the present embodiment, the purge concentration is detected based on the detection result of the intake pressure sensor 32 that is generally required for air-fuel ratio control. Therefore, it is not necessary to provide a concentration sensor, the cost increase can be suppressed, and the entire apparatus Can be simplified.
[0068]
(Second Embodiment)
Next, a control device for an internal combustion engine according to a second embodiment will be described with reference to FIGS. In addition, in order to avoid duplication description, the same reference number is attached | subjected about the same element as what was demonstrated in FIG. 1, FIG. Further, the description will focus on the differences from the first embodiment described above.
[0069]
FIG. 7 is a schematic configuration diagram showing the control device for the internal combustion engine of the present embodiment. In the present embodiment, a pressure sensor 51 is provided in the vapor control valve 20 provided in the canister 14. Other configurations are the same as those of the first embodiment.
[0070]
The pressure sensor 51 detects the pressure PTANK in the canister 14 and outputs a signal corresponding to the magnitude.
As shown in the block circuit diagram of FIG. 8, the pressure sensor 51 is connected to the external input circuit 46 in the same manner as the various sensors 31 to 37. The ECU 41 includes a central processing unit (CPU) 42, a read only memory (ROM) 43, a random access memory (RAM) 44, and a backup RAM 45. The ECU 41 includes these parts 42 to 45, an external input circuit 46 and an external output circuit 47 connected by a bus 48.
[0071]
Here, the ROM 43 stores in advance a control program for executing the various controls described above, a basic purge concentration map used for purge concentration calculation, and the like. This basic purge concentration map is created based on the pressure PTANK, the intake pressure Pim, the engine speed NE, and the throttle opening degree VTA in the canister 14 when the purge control is not performed.
[0072]
The CPU 42 reads signals from the various sensors 31 to 37 and 51 input via the external input circuit 46 as input values. The CPU 42 controls the members 4, 7, and 22 in order to execute the various controls described above based on these input values. In the present embodiment, the fuel purge control is similarly performed based on the “fuel purge control routine” shown in FIG. 3.
[0073]
FIG. 9 is a flowchart showing a “purge concentration calculation routine” regarding the processing contents of the fuel purge control. The ECU 41 periodically executes this routine at predetermined intervals when the engine 8 is operated.
[0074]
In step 400, the ECU 41 detects the intake pressure Pim (n), the throttle opening VTA (n), the engine speed NE (n), the atmospheric pressure Pa, the canister 14 detected by the various sensors 32, 33, 35, 37, 51. A value related to the pressure PTANK (n) is read as an input value before the purge control and stored in the RAM 44. Further, the ECU 41 estimates the purge concentration from the pressure PTANK (n).
[0075]
In step 410, the ECU 41 determines whether purge control has been performed. If it is determined in step 410 that the purge control is not performed, the process returns to step 400.
[0076]
If it is determined in step 410 that the purge control has been performed, in step 420, the ECU 41 determines that the intake pressure Pim (n + 1), the throttle opening VTA (n + 1), the engine rotational speed NE (n + 1), and the atmospheric pressure Pa after the purge control. The value relating to the pressure PTANK (n + 1) is read.
[0077]
In step 430, the ECU 41 calculates an intake pressure change ΔPim, a rotational speed change ΔNE, an opening change ΔVTA, and a pressure change ΔPTANK by subtracting the value of each parameter before the purge control from the value of each parameter after the purge control. To do. The ECU 41 calculates the purge concentration based on the pressure PTANK (n) and the pressure change ΔPTANK before the purge control, and the intake pressure change ΔPim and the intake pressure change ΔPim (ΔNE, ΔVTA) after the purge control. The intake pressure change ΔPim (ΔNE, ΔVTA) is obtained from the basic purge concentration map, and is a change in the intake pressure corresponding to the rotational speed change ΔNE and the opening change ΔVTA when the purge control is not performed. .
[0078]
In the present embodiment, the ECU 41 that executes this routine corresponds to a purge concentration calculation unit.
In the present embodiment, when the fuel purge is executed, the ECU 41 determines that, and first, the pressure in the canister 14 before and after the start of the operation of the purge control valve 22 is detected by the pressure sensor 51 provided in the canister 14. Then, the purge concentration of the fuel vapor is calculated based on the pressure change. Then, the ECU 41 decreases the fuel injection amount TAU by a value TD corresponding to the purge concentration. Also in this embodiment, the air-fuel ratio A / F of the air-fuel mixture in the engine 8 can be suppressed from becoming rich and the air-fuel ratio A / F can be stabilized immediately after the start of the fuel purge as in the first embodiment. .
[0079]
(Third embodiment)
Next, a control device for an internal combustion engine according to a third embodiment will be described with reference to FIGS. In addition, in order to avoid duplication description, the same reference number is attached | subjected about the same element as what was demonstrated in FIG. 1, FIG. Further, the description will focus on the differences from the first embodiment described above.
[0080]
FIG. 10 is a schematic configuration diagram showing the control device for the internal combustion engine of the present embodiment. In the present embodiment, the canister 14 is provided with a weight sensor 52 that detects the weight of the canister 14 and outputs a signal corresponding to its size. Other configurations are the same as those of the first embodiment.
[0081]
As shown in the block circuit diagram of FIG. 11, the weight sensor 52 is connected to the external input circuit 46 in the same manner as the various sensors 31 to 37. The ECU 41 includes a central processing unit (CPU) 42, a read only memory (ROM) 43, a random access memory (RAM) 44, and a backup RAM 45. The ECU 41 includes these parts 42 to 45, an external input circuit 46 and an external output circuit 47 connected by a bus 48.
[0082]
Here, the ROM 43 stores in advance a control program for executing the various controls described above, a basic purge concentration map used for purge concentration calculation, and the like. This basic purge concentration map is created based on the weight W of the canister 14 when the purge control is not performed, the intake pressure Pim, the engine speed NE, and the throttle opening VTA.
[0083]
The CPU 42 reads signals from the various sensors 31 to 37 and 52 input via the external input circuit 46 as input values. The CPU 42 controls the members 4, 7, and 22 in order to execute the various controls described above based on these input values. In the present embodiment, the fuel purge control is similarly performed based on the “fuel purge control routine” shown in FIG. 3.
[0084]
FIG. 12 is a flowchart showing a “purge concentration calculation routine” regarding the processing contents of the fuel purge control. The ECU 41 periodically executes this routine at predetermined intervals when the engine 8 is operated.
[0085]
In step 450, the ECU 41 detects the intake pressure Pim (n), the throttle opening VTA (n), the engine speed NE (n), the atmospheric pressure Pa, the canister 14 detected by the various sensors 32, 33, 35, 37, 52. The value related to the weight W (n) is read as an input value before the purge control, and is stored in the RAM 44. Further, the ECU 41 estimates the purge concentration from the weight W (n).
[0086]
In step 460, the ECU 41 determines whether purge control has been performed. If it is determined in step 460 that the purge control is not performed, the process returns to step 450.
[0087]
If it is determined in step 460 that the purge control has been performed, in step 470, the ECU 41 performs the intake pressure Pim (n + 1), the throttle opening VTA (n + 1), the engine rotational speed NE (n + 1), and the atmospheric pressure Pa after the purge control. Then, a value related to the weight W (n + 1) is read.
[0088]
In step 480, the ECU 41 calculates the intake pressure change ΔPim, the rotational speed change ΔNE, the opening change ΔVTA, and the weight change ΔW by subtracting the value of each parameter before the purge control from the value of each parameter after the purge control. To do. The ECU 41 calculates the purge concentration based on the weight W (n) and the weight change ΔW before the purge control, and the intake pressure change ΔPim and the intake pressure change ΔPim (ΔNE, ΔVTA) after the purge control. The intake pressure change ΔPim (ΔNE, ΔVTA) is obtained from the basic purge concentration map, and is a change in the intake pressure corresponding to the rotational speed change ΔNE and the opening change ΔVTA when the purge control is not performed. .
[0089]
In the present embodiment, the ECU 41 that executes this routine corresponds to a purge concentration calculation unit.
In this embodiment, when the fuel purge is executed, the ECU 41 determines that, and first, the canister including the fuel vapor before the operation of the purge control valve 22 is started by the weight sensor 52 that detects the weight of the canister 14. 14 is detected, and the purge concentration of the fuel vapor is calculated based on the weight of the canister 14. Then, the ECU 41 decreases the fuel injection amount TAU by a value TD corresponding to the purge concentration. Therefore, also in this embodiment, it is possible to suppress the air-fuel ratio A / F of the air-fuel mixture in the engine 8 from becoming rich and to stabilize the air-fuel ratio A / F immediately after the start of fuel purge.
[0090]
The present invention can be embodied in another embodiment as follows. In other embodiments described below, the same operations and effects as those of the above embodiments can be obtained.
In the above embodiment, as shown in the flowchart of FIG. 3, when the purge condition is satisfied, the opening degree of the purge control valve 22 is adjusted based on the target opening degree DPG calculated according to the operating state of the engine 8. The amount of fuel to be purged was adjusted. On the other hand, when the purge condition is satisfied, the fuel purge may be performed by opening the purge control valve 22 with a uniform opening.
[0091]
In the first embodiment, the intake pressure Pim (n), the throttle opening VTA (n), the engine rotational speed NE (n), and the atmospheric pressure Pa read in Step 200 of FIG. 4 and Step 250 of FIG. The basic purge concentration map stored in the ROM 43 may be updated based on the value relating to the above, and the purge concentration may be calculated based on the updated purge concentration map.
[0092]
Similarly, in the second embodiment, the intake pressure Pim (n), throttle opening VTA (n), engine speed NE (n), atmospheric pressure Pa, pressure PTANK (n) read in step 400 of FIG. The basic purge concentration map stored in the ROM 43 may be updated based on the value related to (), and the purge concentration may be calculated based on the updated purge concentration map. Further, in the third embodiment, the intake pressure Pim (n), the throttle opening degree VTA (n), the engine speed NE (n), the atmospheric pressure Pa, and the weight W (n) read in step 450 of FIG. The basic purge concentration map stored in the ROM 43 may be updated based on the value relating to the above, and the purge concentration may be calculated based on the updated purge concentration map.
[0093]
In this specification, means relating to the configuration of the invention are defined as follows.
(A) An injector means a nozzle with a solenoid valve for injecting fuel, and the solenoid valve injects fuel by opening based on an electric signal from the ECU. This fuel injection amount is determined by the opening time of the solenoid valve.
[0094]
【The invention's effect】
As described above in detail, according to the present invention, the concentration of the fuel vapor adsorbed in the canister is detected during the purge control or before the purge control is performed, and the stable air-fuel ratio control immediately after the purge control is started. It can be performed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a control apparatus for an internal combustion engine according to a first embodiment.
FIG. 2 is a block circuit diagram showing the configuration of the ECU according to the first embodiment.
FIG. 3 is a flowchart showing a “fuel purge control routine”.
FIG. 4 is a flowchart showing a “purge concentration calculation routine”;
FIG. 5 is a flowchart showing another “purge concentration calculation routine”;
FIG. 6 is a flowchart showing a “fuel injection control routine”.
FIG. 7 is a configuration diagram showing a control device for an internal combustion engine according to a second embodiment.
FIG. 8 is a block circuit diagram showing a configuration of an ECU according to the second embodiment.
FIG. 9 is a flowchart showing a “purge concentration calculation routine”.
FIG. 10 is a configuration diagram illustrating a control device for an internal combustion engine according to a third embodiment.
FIG. 11 is a block circuit diagram showing a configuration of an ECU according to a fourth embodiment.
FIG. 12 is a flowchart showing a “purge concentration calculation routine”.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 7 ... Injector, 8 ... Engine as internal combustion engine, 14 ... Canister, 22 ... Purge control valve, 32 ... Intake pressure sensor, 41 ... Purge concentration calculation means, ECU as control means, 51 ... Pressure sensor 52 Weight sensor

Claims (2)

A canister for storing fuel vapor generated in the fuel tank;
A purge control valve for controlling the amount of fuel vapor purged from the canister to the intake system of the internal combustion engine;
An injector for supplying fuel to an intake system of an internal combustion engine by injecting fuel;
Purge concentration calculating means for calculating the purge concentration of the fuel vapor purged by the purge control valve;
A control device for an internal combustion engine, comprising: control means for controlling the air-fuel ratio by adjusting the amount of fuel supplied from the injector based on the purge concentration calculated by the purge concentration calculation means and the operating state of the internal combustion engine. Because
The purge concentration calculation means calculates a purge concentration based on a pressure difference between an intake pressure at the time of purge execution and an intake pressure in an operation state at the time of purge non-execution that is the same as the operation state at the time of purge execution. A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to claim 1,
An intake pressure sensor for detecting the intake pressure of the internal combustion engine;
The control apparatus for an internal combustion engine, wherein the purge concentration calculation means calculates a purge concentration based on the intake pressure detected by the intake pressure sensor.

Images