JP2008045527A - Controller for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply evaporation fuel to an engine without hindering operation of an automatic stop/restart device. <P>SOLUTION: Both an automatic stop/restart operation of the engine and a purging operation of the evaporation fuel are used together. In the case that engine stop condition is satisfied when purging condition of the evaporation fuel is satisfied, a condition means forcibly closes a purge control valve. Preferably, after the purge control valve is forcibly stopped, a scavenge process for each cylinder for scavenging the evaporation fuel is conducted and, after conducting the scavenge process for each cylinder, a piston stop position adjusting process is conducted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine control device, and more particularly to an engine control device having an automatic stop / restart device and an evaporated fuel purge device.

  The present applicant automatically stops the engine of the vehicle in an idling state when a predetermined automatic stop condition is satisfied, and restarts the stopped engine when the predetermined restart condition is satisfied. Proposed an automatic stop / restart device (Patent Documents 1 and 2).

  On the other hand, in recent years, various measures have been taken to prevent air pollution caused by evaporated fuel. As a countermeasure, a negative pressure sealed tank that communicates the fuel tank with the intake pipe of the engine via a canister and appropriately reduces the pressure inside the fuel tank so that it is not released to the evaporated fuel outside air generated in the fuel tank. There is an evaporative fuel purge apparatus that includes an apparatus and purges (discharges) evaporative fuel generated from a fuel tank to the engine based on an opening / closing operation of a purge control valve when a predetermined purge condition is satisfied.

When such an evaporative fuel purge device is used in combination with an automatic engine stop / restart device, it takes longer for the pressure in the fuel tank to reach the target negative pressure or does not reach the target negative pressure after the automatic stop condition is satisfied. There was a case. If the engine is automatically stopped in such a state, unburned fuel is discharged into the exhaust passage, and there is a risk that the exhaust performance will deteriorate. Therefore, when the fuel vapor purge device is used together with the engine automatic stop / restart device, conventionally, when the pressure in the fuel tank is higher than a predetermined pressure, regardless of whether the engine automatic stop condition is satisfied, The automatic engine stop was stopped (Patent Document 3).
JP 2004-293474 A JP 2004-124754 A JP 2002-213268 A

  Naturally, if the automatic stop condition is canceled even if the automatic engine stop condition is satisfied, the saving of fuel consumption, which is the original purpose, cannot be achieved. There is a risk of adversely affecting the problem.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an engine control device that can supply evaporated fuel to the engine without hindering the operation of the automatic stop / restart device.

  In order to solve the above problems, the present invention automatically stops / restarts the engine when a predetermined engine stop condition is satisfied, and restarts the engine when a predetermined engine restart condition is satisfied after the stop. A starter, an evaporated fuel purge device that purges the engine with evaporated fuel generated from a fuel tank when a predetermined purge condition is satisfied, based on an opening / closing operation of a purge control valve, the automatic stop / restart device, and the An engine control device comprising control means for controlling the operation of the evaporated fuel purge apparatus, wherein the control means is configured to control the purge control valve when the engine stop condition is satisfied when the purge condition is satisfied. The engine control device is characterized in that the engine is forcibly closed. In this embodiment, the purge control valve of the evaporated fuel purge device is closed before the engine is automatically stopped, and the purge of evaporated fuel is stopped, so that unburned fuel is discharged during the automatic stop control by the engine automatic stop / restart device. The risk of being lost is eliminated.

  In a preferred aspect, the control means executes a scavenging process for each cylinder after the purge control valve is forcibly closed when the engine stop condition is satisfied when the purge condition is satisfied. is there. In this aspect, since the automatic stop control can be executed after scavenging the remaining evaporated fuel by the purge operation, it becomes possible to execute more accurate automatic stop control.

  In a preferred aspect, the control means ends the scavenging process and starts automatic engine stop control when a predetermined scavenging end condition is satisfied. In this aspect, since the engine is automatically stopped immediately after scavenging the evaporated fuel, the consumption of both the evaporated fuel and the supplied fuel can be improved.

  In a preferred embodiment, an air-fuel ratio sensor is provided that outputs a detection value related to the oxygen concentration of the exhaust gas to the control means, and the control means is configured to engine based on the detection value of the oxygen concentration detection sensor and the characteristics of the air-fuel ratio feedback correction constant. The target air-fuel ratio is feedback-controlled, and the scavenging process is terminated based on a change in the air-fuel ratio feedback correction constant after the purge control valve is forcibly closed. In this aspect, when feedback control of the target air-fuel ratio of the engine is performed, the scavenging process of the evaporated fuel is terminated based on the change in the air-fuel ratio feedback correction constant, so that the actual scavenging state can be grasped and the scavenging completion timing Can be grasped appropriately.

  In a preferred aspect, the control means performs restart of the engine body by combustion when the restart condition is satisfied. In this aspect, the purge control valve is forcibly closed before the process for adjusting the air-fuel ratio at the time of restart is performed, and the scavenging process of each cylinder is executed. It is possible to reliably prevent deviation, and to reliably start the engine when stopped due to fuel combustion.

  In a preferred aspect, the control means executes a piston stop position adjusting process for stopping the piston at a position suitable for combustion restart in the automatic stop process of the piston engine body after the scavenging process. In this aspect, since the evaporated fuel scavenging is executed before the piston position adjustment process is executed, there is no possibility of the piston position adjustment being hindered by the evaporated fuel remaining in the purge path, and combustion restart is performed. It is possible to increase the probability of stopping the engine body at a suitable piston position.

  As described above, according to the present invention, since there is no possibility of unburned fuel being discharged in the process of automatic stop control, evaporated fuel is supplied to the engine without hindering the operation of the automatic stop / restart device. There is a remarkable effect that it can.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a system diagram of an engine 1 according to an embodiment of the present invention.

  With reference to FIG. 1, an engine body 10 according to the engine 1 of the present embodiment is provided with a plurality of cylinders 11, and pistons 12 connected to a crankshaft (not shown) are provided in each cylinder 11. By being inserted, a combustion chamber 14 is formed above. Each combustion chamber 14 faces an electrode of a spark plug 15.

  The engine body 10 is provided with a pair of crank angle sensors SW1 for detecting the engine rotation speed Ne and the rotation direction of the crankshaft. The crank angle sensor SW1 detects the engine rotation speed Ne based on a detection signal output from one side, and detects the rotation direction and phase of the crankshaft based on a detection signal out of phase output from both sides. It is like that.

  In the cylinder head of the engine body 10, an intake port 16 and an exhaust port 17 that open toward the combustion chamber 14 are formed for each cylinder 11, and an intake valve 18 and an exhaust port are provided in these ports 16 and 17, respectively. Each valve 19 is equipped. The intake valve 18 and the exhaust valve 19 are each provided with a variable valve opening timing mechanism (not shown) so that scavenging can be performed by changing the valve opening timing.

  An intake system 20 is provided at the intake port 16, and an exhaust system 30 is provided at the exhaust port 17.

  The intake system 20 includes an air cleaner 21 for purifying intake air at the upstream end. An element 22 is built in the air cleaner 21. A throttle body 23 is provided on the downstream side of the air cleaner 21. The throttle body 23 is provided with a throttle valve 24 that adjusts the intake air amount Qa flowing through the intake system 20. An intake manifold 25 is provided on the downstream side of the throttle body 23, and a branch intake passage 26 provided at the downstream end of the intake manifold 25 is connected to the intake port 16 of the corresponding cylinder 11. In the illustrated example, a direct injection type fuel injection valve 27 is provided in the engine body 10. In the intake system 20, an air flow sensor SW <b> 2 is disposed between the air cleaner 21 and the throttle body 23. The air flow sensor SW2 outputs the intake air amount Qa of the intake air filtered by the element 22. Further, the throttle body 23 is provided with a throttle sensor SW3 for detecting the throttle opening TVO of the throttle valve 24.

  The exhaust system 30 is disposed on the exhaust manifold 31 connected to the exhaust port 17, the exhaust passage 32 provided on the downstream side of the exhaust manifold 31, and on the downstream side of the exhaust passage 32, and is exhausted into the exhaust passage 32. And a three-way catalyst 33 for purifying the burned gas. The exhaust system 30 is provided with a linear air-fuel ratio sensor SW4 disposed upstream of the three-way catalyst 33 and an oxygen concentration sensor SW5 disposed downstream. The linear air-fuel ratio sensor SW4 is for outputting a signal PF that is approximately proportional to the oxygen concentration from the burned gas. The oxygen concentration sensor SW5 is configured so that the output voltage changes suddenly at an oxygen concentration corresponding to the stoichiometric air-fuel ratio, detects whether the oxygen concentration is higher or lower than the stoichiometric air-fuel ratio, and outputs a signal SF. By doing so, the feedback control of the air-fuel ratio is executed. The linear air-fuel ratio sensor SW4 calculates an output corresponding to the actual air-fuel ratio of feedback control, whereas the oxygen concentration sensor SW5 calculates a detection value corresponding to the oxygen concentration of the burned gas after purification. Is. In this embodiment, the target air-fuel ratio of the engine is set to the theoretical air-fuel ratio (λ = 1) in principle.

  The fuel supply system 40 that supplies fuel to the fuel injection valve 27 includes a fuel tank 41, in which a fuel pump 42, a low-pressure fuel filter 43, a high-pressure fuel filter 44, and a pressure are provided. A regulator 45 is arranged. A fuel passage 46 downstream of the pressure regulator 45 is connected between the fuel tank 41 and the fuel injection valve 27, and a high-pressure fuel pump 47 is provided in the middle of the fuel passage 46. The fuel is stored in the fuel tank 41 and sucked up by the fuel pump 42 through the fuel filter 43 on the low pressure side. Then, it passes through the high-pressure fuel filter 44, is adjusted to a predetermined pressure by the pressure regulator 45, flows through the fuel passage 46, and is supplied from the high-pressure fuel pump 47 to the fuel injection valve 27 through the supply passage 47 </ b> A. The high-pressure fuel pump 47 is driven by a camshaft. In the illustrated example, the high pressure fuel pump 47 is provided with a relief passage 47B, and the relief passage 47B is connected to the fuel injection valve 27 via a relief valve 47C. The relief valve 47C is configured to open when the fuel pressure becomes a predetermined value or more.

  Further, as an evaporative fuel purge device that adsorbs and traps evaporative fuel generated in the fuel tank 41, purges it when a predetermined condition is established, and purges it to the intake side, an evaporative fuel passage 48 is connected to the upper portion of the fuel tank 41, The other end of the evaporative fuel passage 48 is connected to an upper portion of a canister 49 that stores activated carbon for trapping adsorption. Further, a purge passage 50 is provided to connect the upper portion of the canister 49 and the intake manifold 25 of the intake system, and a solenoid type purge valve 51 for controlling the flow rate by the control of the engine control unit 100 is arranged in the purge passage 50. It is installed. A catch tank 52 that captures liquefied evaporated fuel is disposed between the canister 49 and the purge valve 51. An atmospheric passage 53 for introducing purge air is connected to the lower portion of the canister 49.

  Each of the sensors SW1 to SW5, the throttle valve 24, the fuel injection valve 27, and the EGR opening / closing valve 61 are connected to the engine control unit 100. In the present embodiment, in order to detect the operating state of the engine 1, a water temperature sensor SW6 that detects the coolant temperature of the engine body 10, a vehicle speed sensor SW7 that detects the vehicle speed, and a brake depression amount are detected. A brake sensor SW8 is connected.

  The engine control unit 100 includes a CPU 101, a memory 102, an interface 103, and a bus 104 for connecting these units 101 to 103.

  Various sensors including the sensors SW1 to SW8 are connected to the interface 103 as input elements, and the operating state can be determined by receiving detection signals from these sensors SW1 to SW8 and the like. The interface 103 is connected to an unillustrated controller and driver as output elements, and through these units, the variable valve opening timing mechanism of the intake valve 18 and the exhaust valve 19, the throttle valve 24, the fuel injection The valve 27 and the purge valve 51 can be driven.

  The memory 102 stores programs and data for controlling the entire engine. By executing such a program based on a flowchart described in detail later, the engine control unit 100 functionally operates an automatic stop / restart device, its control means, and control means for controlling the operation of the evaporated fuel purge device. It is configured.

  The memory 102 stores a control map based on the characteristic diagram of FIG.

  FIG. 2 is a characteristic diagram showing the relationship between the required torque and the engine speed according to the embodiment of FIG.

  With reference to FIG. 2, in order to execute the purge operation for purging the evaporated fuel for each operation region, a characteristic diagram as shown in FIG. 2 is set in advance by an experiment or the like, and the set value is stored in the memory 102 as a control map. It is remembered.

  The memory 102 also has various control maps M1, M2 (see FIG. 8), M3, M4 (see FIG. 9) in order for the engine control unit 100 to function as control means for the automatic stop / restart device of the engine 1. ) And M5 (see FIG. 10) are stored.

  FIG. 3 is a flowchart illustrating an example of operation control according to the embodiment of FIG. 1.

  Referring to FIG. 3, when this operation control is executed, engine control unit 100 first reads various data and grasps the operation state (step S20). Next, the engine control unit 100 determines whether or not a predetermined engine stop condition is satisfied (step S21). Here, the predetermined engine stop condition is a condition determined based on the vehicle speed, the operating condition of the brake, the engine water temperature, etc. For example, the vehicle speed is lower than the predetermined speed, the brake is operating, and the engine water temperature is If it is within a predetermined range and there is no particular inconvenience for stopping the engine body 10, it is assumed that the automatic stop condition is satisfied.

  When the engine stop condition in step S21 is satisfied (YES in step S21), the engine control unit 100 executes an engine automatic stop preparation subroutine (step S22).

  Next, the engine control unit 100 executes an automatic stop subroutine for the engine 1 (step S23).

  Next, the engine control unit 100 waits for the restart condition to be satisfied (step S24). Here, the restart condition is when the brake is released to start from a stopped state, when an accelerator operation or the like is performed, or when the engine needs to be operated for the operation of an air conditioner or the like. is there. When the restart condition is satisfied, the engine control unit 100 executes restart control (engine combustion restart subroutine) of the engine body 10 (step S25). Here, in the present embodiment, as will be described later, a reverse combustion restart system is employed in which the engine body 10 is once reversely rotated by fuel combustion and then forwardly rotated. However, the present invention is not limited to this, and a normal combustion restarting system that performs normal rotation immediately may be adopted. Moreover, the motor combined use restart which used the starter motor not shown in figure may be sufficient.

  Next, the engine control unit 100 executes a normal operation subroutine (step S26). In this normal operation subroutine, the engine control unit 100 is an evaporative fuel purge operation region when a predetermined purge execution condition based on the engine rotational speed Ne, the engine load, the engine water temperature, etc. is satisfied, that is, based on the characteristic diagram of FIG. Is determined based on the control map (step S261), and if it is the purge operation region, the evaporated fuel purge operation subroutine is executed (step S262).

  The purge execution condition is, for example, that the execution condition for air-fuel ratio feedback is satisfied when the engine water temperature is equal to or higher than a predetermined value in a predetermined low rotation / low load region.

  In the purge operation subroutine of step S262, the purge valve 51 is opened, the evaporated fuel trapped in the canister 49 is purged and supplied to the surge tank of the intake manifold 25. The purge rate (the ratio of the purge amount to the intake air amount of the engine) is set so that the supply amount of air (purge amount) containing 0 gradually increases from 0 to the required amount according to the engine operating state. The duty ratio for driving the purge valve 51 is controlled according to the amount of air. In the control for gradually increasing the purge rate at the start of the purge of evaporated fuel, the purge rate is set to a predetermined amount, for example, a target purge rate (corresponding to the required purge amount) in synchronization with the inversion of the output of the linear air-fuel ratio sensor SW4 at the beginning of the gradually increasing period. The purge rate is increased by 1%, and the purge rate is increased by, for example, 0.025% every predetermined time, for example, 65 ms in the latter period of the gradual increase period. In this case, at the beginning of the purge of evaporated fuel with a particularly high evaporated fuel concentration, the purge amount is increased at a long time interval in synchronization with the inversion of the output of the linear air-fuel ratio sensor SW4, thereby suppressing fluctuations in the air-fuel ratio. In the latter part of the gradual increase period in which the fuel vapor concentration decreases, the purge amount is quickly increased to the required amount at short time intervals. Further, based on the correction amount of the air-fuel ratio feedback, estimation learning of the concentration of the evaporated fuel in the purge gas is performed. In this learning, the evaporated fuel concentration is estimated based on a value obtained by dividing the average value of the predetermined number of times of the air-fuel ratio feedback correction amount by the average purge rate during the purge. The purge correction amount is determined according to the learned evaporated fuel concentration.

  Further, when the air-fuel ratio feedback correction amount exceeds a predetermined threshold during purging, a purge amount reduction process is performed. The threshold value is changed between when evaporative fuel concentration learning is completed and when it is not completed. This change is to increase the threshold value when density learning is not completed, compared to when density learning is completed. The deviation of the air-fuel ratio due to the supply of the evaporated fuel is detected by the linear air-fuel ratio sensor SW4, and the air-fuel ratio is feedback-corrected based on the sensor output. In addition, feedback response delay is compensated for by correcting the fuel injection amount based on evaporative fuel concentration learning. Further, when the air-fuel ratio feedback correction amount exceeds the threshold value, the purge amount is reduced. The deviation of the air-fuel ratio due to is suppressed. When the evaporative fuel concentration concentration learning is not completed, the threshold value is increased so that the concentration learning is executed in preference to the purge reduction based on the air-fuel ratio feedback correction amount.

  When the evaporated fuel purge operation subroutine (step S262) is executed or not in the purge operation region (NO in step S261), the engine control unit 100 executes the air-fuel ratio feedback subroutine (step S263). ). In this air-fuel ratio feedback subroutine, the basic fuel injection amount is calculated based on the engine speed Ne calculated from the output of the crank angle sensor SW1 and the intake air amount calculated from the output of the airflow sensor SW2, and the basic fuel injection is calculated. Various corrections corresponding to the engine water temperature and the like calculated from the output of the water temperature sensor SW6 are added to the amount, and feedback correction based on the output of the linear air-fuel ratio sensor SW4 is added thereto to converge the air-fuel ratio of the engine 1 to the target air-fuel ratio. Is. Then, the engine control unit 100 returns to step S20 and repeats the above-described processing.

  If it is determined in step S21 that the engine stop condition is not satisfied (NO in step S21), the engine control unit 100 immediately proceeds to step S26 and executes steps S261 to S263 described above. Then, the steps after step S20 are repeated.

  FIG. 4 is a flowchart of the engine automatic stop preparation subroutine in FIG.

  Referring to FIG. 4, in the engine automatic stop preparation subroutine (step S22), engine control unit 100 first determines whether or not a vaporized fuel purge operation is being performed (step S220). If the purge operation is being executed, the purge valve 51 is closed and the purge operation is forcibly terminated (step S211). Next, the engine control unit 100 executes a scavenging process (step S222). In this scavenging process, the engine operation is continued with the purge valve 51 closed, and the evaporated fuel remaining in the branch intake passage 26 is scavenged (combusted in the combustion chamber 14).

  Next, the engine control unit 100 waits for the timing to end the scavenging process (step S232). The end timing of the scavenging process can be determined by various methods.

  5 and 6 are timing charts showing an operation example according to the embodiment of FIG.

  With reference to each figure, these driving examples show a case where the brake is depressed at a certain timing t1, the vehicle speed becomes 0 at t2, the automatic stop condition is satisfied, and the purge operation of the evaporated fuel is forcibly stopped. ing. In addition, the virtual line of the purge correction amount in the figure shows the case of normal control (or conventional technology).

  Here, referring to FIG. 5, in the present embodiment, since the air-fuel ratio feedback control is executed in the normal operation subroutine (step S26) (step S263), the purge operation of the evaporated fuel is forcibly stopped. Then, the purge correction amount becomes 0, and the detected value of the linear air-fuel ratio sensor SW4 becomes rich due to scavenging. Therefore, the value of the air-fuel ratio feedback correction constant is transiently updated to the rich side after timing t2, The characteristic of returning to the lean side at a predetermined timing t3 is shown. Therefore, in the present embodiment, in embodying the determination in step S223 of FIG. 4, the characteristic of the air-fuel ratio feedback correction constant is used to forcibly stop the purge operation of the evaporated fuel, and then return to the rich side. When the updated air-fuel ratio feedback correction constant returns to the lean side, it is determined that the purge scavenging has ended.

  On the other hand, FIG. 6 can be adopted as another embodiment.

  With reference to FIG. 6, in this embodiment, the timer function of the engine control unit 100 is used, and after the evaporative fuel purge operation is forcibly terminated, the termination determination is made after a predetermined time has elapsed.

  If it is determined in step S223 in FIG. 4 that the purge scavenging has been completed, the process returns to the main routine in FIG. 3, and the engine automatic stop subroutine (step S23) is executed. If it is determined in step S220 in FIG. 4 that the evaporated fuel purge operation has not been executed, the engine control unit 100 immediately proceeds to step S23.

  FIG. 7 is a flowchart of the engine automatic stop control subroutine in FIG.

  Referring to FIG. 7, in the engine automatic stop control subroutine (step S23), engine control unit 100 executes a torque reduction process for each piston 12 (step S231). This torque reduction process is realized, for example, by retarding the ignition timing of the spark plug 15. Alternatively, a method of delaying the valve closing timing of the intake valve 18 may be employed. By doing this, the air-fuel ratio at the time of stop can be adjusted, the air-fuel ratio control at the time of restart can be refined, the generated torque of the engine body 10 is reduced, and torque fluctuations are suppressed. Variations in the rotational speed reduction characteristics at the time of stopping can be reduced, and the probability that the piston 12 stops at an appropriate position can be improved.

  Further, the engine control unit 100 opens the throttle valve 24 by a predetermined opening (step S232). The opening of the throttle valve 24 is performed to increase scavenging of burned gas in the cylinder 11 by increasing the intake air amount.

  Subsequently, the engine control unit 100 determines whether or not the engine rotational speed Ne is in the fuel cut allowable rotational speed range (650 ± 10 rpm) (step S233). If “NO” here, the steps S231 and S232 are repeated, and the process waits until “YES”. When it is determined that the engine rotational speed Ne is within the fuel cut allowable rotational speed range (650 ± 10 rpm) (YES in step S233), the fuel supply from the fuel injection valve 27 and the operation of the spark plug 15 are stopped (fuel cut (Step S234). As described above, in the present embodiment, the fuel cut allowable rotational speed region is provided, and the fuel cut is performed aiming at the time when the engine rotational speed Ne is within the fuel cut allowable rotational speed region. For example, when the engine speed Ne during idling is feedback controlled to 650 ± 50 rpm, the fuel cut allowable rotational speed range is set to 650 ± 10 rpm as described above. In other words, when idling, the engine speed Ne fluctuates in the range of 650 ± 50 rpm, and the fuel cut is performed aiming at the moment when it enters the range of 650 ± 10 rpm. This is done to stop the piston 12 within a preferable range for restarting, and if the fuel cut is performed in the fuel cut allowable rotational speed region, the probability that the piston 12 stops within the preferable range increases. It has been confirmed. If the engine rotation speed Ne at the end timing of the scavenging process of each cylinder 11 is within the fuel cut allowable rotation speed range, the fuel cut is performed in synchronization with the end timing of the scavenging process of each cylinder 11. However, if this is not the case, the fuel cut is suspended until the engine rotational speed Ne enters the fuel cut allowable rotational speed range.

  After executing the fuel cut, the engine control unit 100 determines whether or not the engine rotational speed Ne has dropped below a predetermined rotational speed range (500 rpm in the present embodiment) set in advance (step S235). If the engine rotational speed Ne reaches 500 rpm or less, the engine control unit 100 closes the throttle valve 24 (step S236). By the piston stop position adjustment process in steps S231 to S236 described above, the probability that the stop position of each piston 12 is within a preferable range is increased using the pressure of air in the cylinder 11. On the other hand, if the engine speed Ne exceeds 500 rpm, the fuel cut in step S234 is executed until the engine speed Ne decreases, and the system waits.

  Subsequently, the engine control unit 100 then waits for the engine main body 10 to stop completely (step S237), and if YES, stores the stop position of the piston 12 (step S238) and returns to the main flow.

  8 to 10 are flowcharts of the engine combustion restart subroutine in FIG.

  Referring to FIG. 8, in this combustion restart subroutine (step S25), engine control unit 100 estimates the in-cylinder temperature of each cylinder 11 from the water temperature, stop time, intake air temperature, and the like (step S251). Based on the detected stop position of the piston 12, the engine control unit 100 calculates the amount of air in the cylinder 11 that is in the compression stroke when stopped and the cylinder 11 that is in the expansion stroke when stopped (step S252). By this step S252, the combustion chamber volumes of the cylinder 11 in the compression stroke when stopped and the cylinder 11 in the expansion stroke when stopped are obtained. Further, when the engine main body 10 is automatically stopped, the engine is stopped after several revolutions after the fuel cut by the control in step S24, so that the cylinder 11 in the expansion stroke at the time of the stop is also filled with fresh air. In addition, since the inside of the cylinder 11 that is in the compression stroke when the engine is stopped and the cylinder 11 that is in the expansion stroke when the engine is stopped is substantially at atmospheric pressure, the amount of fresh air can be obtained from the combustion chamber volume. Become.

  Next, the engine control unit 100 has a relatively low dead center side within a predetermined combustion stop range (60 to 80 ° crank angle before compression top dead center) in the cylinder 11 whose piston stop position is in the compression stroke when stopped. It is determined whether or not (step S253).

  If YES is determined in step S253, the engine control unit 100 proceeds to step S254, where λ (excess air ratio) with respect to the air amount of the cylinder 11 in the compression stroke at the time of stop calculated in step S252> The fuel is injected so that the air-fuel ratio becomes 1 (for example, the air-fuel ratio = about 20) (first fuel injection). This air-fuel ratio is obtained from the compression stroke cylinder first-time air-fuel ratio map M1 set in advance according to the stop position of the piston. By setting the lean air-fuel ratio such that λ> 1, even when the amount of air in the cylinder 11 that is in the compression stroke at the time of stop is relatively large, the combustion energy for the reverse rotation direction is not excessive and the reverse rotation is performed. To prevent it from passing.

  On the other hand, if NO is determined in step S253, the engine control unit 100 proceeds to step S255, and the air-fuel ratio satisfying λ ≦ 1 with respect to the air amount of the cylinder 11 in the compression stroke at the time of stop calculated in step S252. The fuel is injected so as to become (first fuel injection). This air-fuel ratio is obtained from a compression stroke cylinder first-time air-fuel ratio map M2 set in advance according to the stop position of the piston. By setting the stoichiometric air-fuel ratio of λ ≦ 1 or a richer air-fuel ratio, sufficient combustion energy for the reverse direction can be obtained even when the amount of air in the cylinder 11 in the compression stroke at the time of stop is relatively small. be able to.

  In the present embodiment, when the engine body 10 is automatically stopped, the scavenging process for each cylinder 11 is executed in step S22, and then the piston stop position adjustment process (steps S231 to S236) is executed in step S23. Therefore, the calculation in step S254 or S255 is extremely precise.

  Next, the engine control unit 100 proceeds to step S256, and ignites the cylinder after elapse of a time set in consideration of the vaporization time from the first fuel injection to the cylinder 11 in the compression stroke at the time of stop. . Then, the engine control unit 100 determines whether or not the piston 12 has moved based on whether or not the edge of the crank angle sensor SW1 (rise or fall of the crank angle signal) is detected within a predetermined time after ignition (see FIG. Step S257).

  If it is determined as YES in this step S257 and it is confirmed that the piston 12 has moved, the engine control unit 100 proceeds to the next step.

  On the other hand, when it is determined NO in step S257 and it is confirmed that the piston 12 has not moved due to misfire, the engine control unit 100 performs re-ignition on the cylinder 11 in the compression stroke when stopped ( Step S258) and the determination of step S257 are repeated.

  Referring to FIG. 9, when it is determined as YES in step S257 and it is confirmed that the piston 12 has moved, the engine control unit 100 performs the stop based on the piston stop position and the in-cylinder temperature estimated in step S251. A division ratio of the split fuel injection to the cylinder 11 in the expansion stroke (ratio between the first stage injection (first time) and the second stage injection (second time)) is calculated (step S2512). As the piston stop position in the cylinder 11 that is in the expansion stroke at the time of stopping is closer to the bottom dead center, and the in-cylinder temperature is higher, the injection ratio at the subsequent stage is increased.

  Next, the engine control unit 100 calculates the fuel injection amount so that a predetermined air-fuel ratio (λ ≦ 1) is obtained with respect to the air amount of the cylinder 11 in the expansion stroke at the time of stop calculated in step S252 (step S2513). ). The air-fuel ratio at this time is obtained from the expansion stroke cylinder air-fuel ratio map M3 set in advance according to the stop position of the piston. In the present embodiment, when the engine body 10 is automatically stopped, the scavenging process for each cylinder 11 is executed in step S22, and then the piston stop position adjustment process (steps S231 to S236) is executed in step S23. Therefore, the calculation in step S2513 is extremely precise.

  Next, the engine control unit 100 uses the split ratio calculated in step S2512 and the fuel injection amount to the cylinder 11 that is in the expansion stroke at the time of stop calculated in step S2513 to the preceding stage for the cylinder 11 that is in the expansion stroke at the time of stop. The first fuel injection amount is calculated and injected (step S2514).

  Next, based on the in-cylinder temperature estimated in step S251, the engine control unit 100 calculates the second (second) fuel injection timing for the cylinder 11 that is in the expansion stroke when stopped (step S2515). This second injection timing is the time when the in-cylinder air is compressed after the piston 12 starts moving toward the top dead center (in the reverse direction of the engine), and the vaporization latent heat of the injected fuel is compressed. It is set so that the pressure is effectively reduced (the piston 12 is made as close to the top dead center as possible), and the time for the second injected fuel to evaporate by the ignition timing is as long as possible. The

  Next, the engine control unit 100 calculates the fuel injection amount at the second injection timing calculated in step S2515, and causes the fuel injection valve 27 to inject the calculated amount of fuel (step S2516). After the second fuel injection to the cylinder 11 in the expansion stroke at the time of this stop, the engine control unit 100 drives the spark plug 15 after a predetermined delay time has elapsed (steps S2517 and S2518). The predetermined delay time is obtained from an expansion stroke cylinder ignition delay map M4 set in advance according to the stop position of the piston. The engine turns from the reverse rotation direction to the normal rotation direction by the initial combustion in the cylinder 11 in the expansion stroke when the ignition is stopped. Therefore, when stopping, the piston 12 of the cylinder 11 in the compression stroke moves to the top dead center side and starts to compress the internal gas (burned gas burned by ignition in step S256).

  After ignition in the cylinder 11 in the expansion stroke at the time of stop in step S2518, the engine control unit 100 detects the edge of the crank angle sensor SW1 (rise or fall of the crank angle signal) within a predetermined time after ignition again. Whether or not the piston 12 has moved is determined based on whether or not it has been performed (step S2519). If it is determined as YES in step S2518 and it is confirmed that the piston 12 has moved, the engine control unit 100 proceeds to the next step.

  On the other hand, if it is determined NO in step S2519 and it is confirmed that the piston 12 has not moved due to misfire, the engine control unit 100 performs reignition on the cylinder 11 in the compression stroke at the time of stop ( Steps S2522) and S2519 are repeated.

  Next, referring to FIG. 10, when it is determined YES in step S2519 and it is confirmed that the piston 12 has moved, the engine control unit 100 performs fuel vaporization on the cylinder 11 in the compression stroke at the time of stoppage. An amount of the second fuel that takes time into account is injected into the fuel injection valve 27 (step S2521). The fuel injection amount at this time is such that the overall air-fuel ratio based on the total amount with the first injection amount becomes richer (for example, about 6) than the combustible air-fuel ratio (lower limit is 7 to 8). It is obtained from the second air-fuel ratio map M5 for the cylinder 11 in the compression stroke at the time of stop set in advance according to the stop position. Since the second vaporization latent heat of the injected fuel to the cylinder 11 in the compression stroke at the time of the stop reduces the compression pressure near the first compression top dead center of the cylinder 11 in the compression stroke at the time of the stop. The compression top dead center can be easily exceeded.

  Note that the second fuel injection to the cylinder 11 in the compression stroke at the time of the stop is performed exclusively for reducing the compression pressure in the cylinder, and no ignition or combustion is performed on this (combustible air) Because it is richer than the fuel ratio, self-ignition does not occur.) This incombustible fuel then reacts with oxygen stored in the three-way catalyst 33 in the exhaust passage 32 and is rendered harmless.

  Since the second injection fuel in the cylinder 11 that is in the compression stroke at the time of stop does not burn, the next combustion following the first combustion in the cylinder 11 that is in the expansion stroke at the time of stop is in the cylinder 11 that is in the intake stroke at the time of stop. It is burning. As energy for the piston 12 of the cylinder 11 in the intake stroke at the time of stopping to exceed the second compression top dead center, part of the energy of the first combustion in the cylinder 11 in the expansion stroke at the time of stop is used. That is, the energy of the first combustion in the cylinder 11 that is in the expansion stroke at the time of stoppage is that the cylinder 11 that is in the compression stroke at the time of stoppage exceeds the first compression top dead center, and then the cylinder 11 that is in the intake stroke at the time of stoppage is 2 Served for both exceeding the top dead center of compression.

  Therefore, for smooth start-up, it is desirable that the load when the cylinder 11 in the intake stroke exceeds the second compression top dead center when stopped is small. In that case, the second compression top dead center can be exceeded with small energy. The following flow is control for exceeding the second compression top dead center with as little energy as possible when performing combustion in the cylinder 11 in the intake stroke at the next stop.

  First, the engine control unit 100 estimates the in-cylinder air density, and calculates the air amount of the cylinder 11 in the intake stroke at the time of stoppage from the estimated value (step S2522). Next, the engine control unit 100 calculates an air-fuel ratio correction value for preventing self-ignition based on the in-cylinder temperature estimated in step S251 (step S2523). That is, when self-ignition occurs, a force (reverse torque) is generated that pushes the piston 12 back to the bottom dead center before reaching the second compression top dead center due to the combustion. This is undesirable because it consumes a lot of energy for exceeding the second compression top dead center. Therefore, in order to suppress this reverse torque, the air-fuel ratio is corrected to a rich value close to lean so that self-ignition does not occur.

  Next, the engine control unit 100 is in the intake stroke at the time of stop from the air amount of the cylinder 11 in the intake stroke at the time of stop calculated in step S2522 and the air-fuel ratio considering the air-fuel ratio correction value calculated in step S2523. A fuel injection amount to the cylinder 11 is calculated (step S2524).

  In the present embodiment, when the engine body 10 is automatically stopped, the scavenging process for each cylinder 11 is executed in step S22, and then the piston stop position adjustment process (steps S231 to S236) is executed in step S23. Therefore, the calculations in steps S2522 to S2524 are extremely precise.

  Then, the fuel injection to the cylinder 11 in the intake stroke is executed when stopped. This fuel injection is delayed until the later stage of the compression stroke so that the compression pressure is reduced by the latent heat of vaporization (that is, the energy required for exceeding the second compression top dead center is reduced) (step) S2525). The delay amount is calculated based on the engine automatic stop period, the intake air temperature, the engine water temperature, and the like.

  On the other hand, the engine control unit 100 calculates the inspection timing starting from the timing at which the edge of the crank angle sensor SW1 is detected in step S2519 (step S2526), and waits until this timing is reached (step S2527).

  Next, it is determined whether or not the engine rotation speed (engine rotation speed at the time of inspection) Ne at the calculated inspection timing is less than the required engine rotation speed (for example, 200 rpm) (step S2528). In this determination, if the engine speed Ne at the time of inspection is equal to or higher than the required engine speed (YES in step S2528), the engine control unit 100 determines that the second compression top dead center is exceeded, and The purge execution is permitted (step S2529), and the process returns to the main routine.

  On the other hand, if it is determined in step S2530 that the required engine speed Ne is not reached, starter motor combined drive control is executed (step S25210).

  Since the starter motor combined drive control itself can use a known technique, a detailed description thereof will be omitted.

  As described above, in the present embodiment, the purge valve 51 as the purge control valve is closed before the engine body 10 is automatically stopped, and the purge of the evaporated fuel is stopped. There is no risk of being discharged.

  In the present embodiment, after the purge valve 51 is forcibly closed, the scavenging process of each cylinder 11 is executed (see FIG. 4). For this reason, in this embodiment, since the evaporated fuel remaining in the purge operation is scavenged, the automatic stop control can be executed, so that more accurate automatic stop control can be executed.

  In the present embodiment, when a predetermined scavenging end condition is satisfied, the scavenging process is ended, and automatic stop control of the engine body 10 is started (see FIGS. 5 and 6). For this reason, in this embodiment, since the engine main body 10 is automatically stopped immediately after scavenging the evaporated fuel, the consumption of both the evaporated fuel and the supplied fuel can be improved.

  Further, in the present embodiment, as shown in FIGS. 4 and 5, a linear air-fuel ratio sensor SW4 that outputs a detection value related to the oxygen concentration of the exhaust gas to the engine control unit 100 is provided, and detection by this linear air-fuel ratio sensor SW4 is performed. The target air-fuel ratio of the engine 1 is feedback-controlled based on the value, and after the purge valve 51 is forcibly closed, the scavenging process is terminated based on a change in the air-fuel ratio feedback correction constant. For this reason, in this embodiment, the actual scavenging state can be grasped, and the scavenging completion timing can be grasped appropriately.

  In the present embodiment, when the restart condition is satisfied, the engine body 10 is restarted by combustion. Before the process for adjusting the air-fuel ratio at the restart is performed, the purge valve 51 is set. Forcibly closing and performing the scavenging process for each cylinder 11 makes it possible to reliably prevent the air-fuel ratio at the time of restart from shifting due to the evaporated fuel, and to ensure the engine at the time of stop due to fuel combustion. Can be started.

  In the present embodiment, after the scavenging process, the piston stop position adjustment process (steps S231 to S236) for stopping the piston 12 at a position suitable for combustion restart is executed in the automatic stop process of the engine body 10. . As described above, since the scavenging of the evaporated fuel is executed before the piston position adjusting process is executed, the position adjustment of the piston 12 may be hindered by the evaporated fuel remaining in the purge path in this embodiment. It becomes possible to increase the probability of stopping the engine body 10 at a piston position suitable for combustion restart.

  Therefore, according to this embodiment, since there is no possibility that unburned fuel is discharged in the process of automatic stop control, the evaporative fuel can be supplied to the engine without disturbing the automatic stop / restart operation. Has an effect.

  The above-described embodiment is merely a preferred specific example of the present invention, and the present invention is not limited to the above-described embodiment.

  For example, the scavenging process may be executed prior to the automatic stop of the engine body 10 regardless of whether or not the purge operation is performed. In that case, the scavenging process may be terminated by the timer shown in FIG.

  It goes without saying that various modifications can be made within the scope of the claims of the present invention.

1 is a system diagram of an engine according to an embodiment of the present invention. It is a characteristic view which shows the relationship between the request torque which concerns on embodiment of FIG. It is a flowchart which shows an example of the operation control which concerns on embodiment of FIG. It is a flowchart of the engine automatic stop preparation subroutine in FIG. It is a timing chart which shows the example of a driving | operation which concerns on embodiment of FIG. It is a timing chart which shows the operation example which concerns on another embodiment applicable to embodiment of FIG. 5 is a flowchart of an engine automatic stop control subroutine in FIG. 4. 6 is a flowchart of an engine combustion restart subroutine in FIG. 6 is a flowchart of an engine combustion restart subroutine in FIG. 6 is a flowchart of an engine combustion restart subroutine in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 10 Engine main body 20 Intake system 27 Fuel injection valve 30 Exhaust system 40 Fuel supply system 41 Fuel tank 48 Evaporative fuel passage 49 Canister 50 Purge passage 51 Purge valve (an example of purge control valve)
100 Engine control unit SW4 Linear air-fuel ratio sensor

Claims (6)

An automatic stop / restart device that automatically stops the engine when a predetermined engine stop condition is satisfied, and restarts the engine when a predetermined engine restart condition is satisfied after the stop;
An evaporative fuel purge device that purges evaporative fuel generated from the fuel tank to the engine based on an opening / closing operation of a purge control valve when a predetermined purge condition is satisfied;
An engine control device comprising: an automatic stop / restart device; and a control means for controlling the operation of the evaporated fuel purge device.
The control means for forcibly closing the purge control valve when the engine stop condition is satisfied when the purge condition is satisfied. The engine control device according to claim 1,
The control means is configured to execute a scavenging process for each cylinder after forcibly closing the purge control valve when the engine stop condition is satisfied when the purge condition is satisfied. Engine control device. The engine control device according to claim 2,
The engine control apparatus, wherein the control means ends the scavenging process and starts automatic engine stop control when a predetermined scavenging end condition is satisfied. The engine control device according to claim 2 or 3,
An air-fuel ratio sensor that outputs a detection value related to the oxygen concentration of the exhaust gas to the control means;
The control means feedback-controls the target air-fuel ratio of the engine based on the detected value of the oxygen concentration detection sensor and the characteristics of the air-fuel ratio feedback correction constant, and the air-fuel ratio after forcibly closing the purge control valve The scavenging process is terminated based on a change in a feedback correction constant. The engine control apparatus according to any one of claims 2 to 4,
The engine control device according to claim 1, wherein the control means executes restart of the engine body by combustion when the restart condition is satisfied. The engine control apparatus according to claim 5, wherein
The control means executes a piston stop position adjusting process for stopping the piston at a position suitable for combustion restart in the automatic stop process of the piston engine body after the scavenging process. Control device.

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