JP4550627B2 - Internal combustion engine stop control method and stop control device - Google Patents

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine stop control method and a stop control apparatus for controlling a crank position based on a stop position of a piston when stopping the internal combustion engine in order to improve starting performance.

  In recent years, with the aim of reducing the fuel consumption and exhaust of the internal combustion engine, the number of vehicles that perform idle stop has been increasing, and when the internal combustion engine is in an idle state while the vehicle is stopped, the internal combustion engine is automatically stopped, Various techniques for automatically restarting the internal combustion engine have been proposed.

  In this case, if it takes time to restart the internal combustion engine, the start operation of the vehicle is delayed with respect to the driver's intention to start, and drivability deteriorates. Therefore, it is important to restart the internal combustion engine quickly and smoothly. . In addition, in an idle stop system that uses a starter motor or the like to perform cranking and restart, a large amount of power is required at the time of cranking, and a situation in which an electrical load does not temporarily operate at the time of restart occurs, The burden on the battery is large and the deterioration is accelerated.

  Therefore, for example, in a starter for a direct injection internal combustion engine described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2002-4929), ignition is performed after the fuel is injected into the expansion stroke cylinder of the stopped internal combustion engine, and rotational torque due to combustion Therefore, a restart method that does not use a starter motor has been proposed. In this restart method, the rotational torque that can be generated by the combustion at the beginning of the start is small, and the rotational torque that is generated by the combustion greatly changes depending on the crank position at which the combustion is started. That is, the stop position of the piston when the internal combustion engine is stopped is important.

  However, in the method of stopping the internal combustion engine by stopping the fuel supply and ignition to the internal combustion engine, the rotational load around the crankshaft has a large influence on the stop, so the stop position of the piston when the rotation of the internal combustion engine stops is indefinite. Become. Therefore, for example, in the stop control method and apparatus for an internal combustion engine described in Patent Document 2 (Japanese Patent Laid-Open No. 2000-213375), the piston is opened near the top dead center by opening the intake throttle valve before stopping the rotation of the internal combustion engine. The intake throttle valve is fully closed when the operation of the internal combustion engine is stopped in order to avoid the stop and to suppress the vibration of the internal combustion engine caused by opening the intake valve.

JP 2002-4929 A JP 2000-213375 A

  However, since the techniques described in Patent Documents 1 and 2 are methods mainly aimed at avoiding the piston of the internal combustion engine from stopping near the top dead center, the piston of the internal combustion engine is placed at a predetermined position. Sufficient consideration has not been given to stopping.

  The piston stop position of the internal combustion engine is determined from the balance between the torque generated by the rotation load acting around the crankshaft of the internal combustion engine and the compression pressure and expansion pressure of the compression stroke cylinder and the expansion stroke cylinder of the internal combustion engine. Therefore, it is necessary to stably stop the piston at a predetermined position when the rotational load other than the torque generated by the compression pressure and the expansion pressure of the compression stroke cylinder and the expansion stroke cylinder of the internal combustion engine is large and small. The compression pressure of the compression stroke cylinder and the expansion pressure of the expansion stroke cylinder are different.

  On the other hand, the compression pressure of the compression stroke cylinder and the expansion pressure of the expansion stroke cylinder cause vibration of the internal combustion engine. From the above, in order to stably control the stop position of the piston of the internal combustion engine and suppress the vibration during the stop control, the optimum (minimum) compression pressure corresponding to the rotational load of the internal combustion engine It is necessary to control the expansion pressure.

  The present invention has been made in view of such problems, and the object of the present invention is to suppress vibrations of the internal combustion engine that occur during the stop process of the internal combustion engine, and to change changes in the rotational load acting on the internal combustion engine. It is an object of the present invention to provide a control method and a control device that can stably stop a piston at a desired stop position without being affected by the difference variation.

  In particular, the piston is stably stopped at a desired stop position without being affected by the vibration suppression of the internal combustion engine that occurs during the stop process of the internal combustion engine, the change in rotational load acting on the internal combustion engine, and the machine difference variation, When starting the internal combustion engine by using the combustion energy generated by fuel injection and ignition into the cylinder in the expansion stroke of the stopped internal combustion engine at the time of subsequent startup, the combustion energy can be used to the maximum extent possible. An object of the present invention is to provide an internal combustion engine stop control apparatus and method that can be configured as described above.

  The present inventors have earnestly researched whether the position of the piston of the internal combustion engine can be stopped at a desired position in a vehicle with an idle stop device with little vibration and can be started smoothly when the internal combustion engine is started. As a result, the present invention having the following characteristics has been completed.

In order to achieve the above object, a stop control method for an internal combustion engine according to the present invention comprises a reciprocating piston and an air amount changing means for changing the amount of intake air into the combustion chamber, and changes the amount of intake air into the combustion chamber. Then, the method for controlling the stop position of the piston, wherein the air amount changing means reduces the intake air amount to a predetermined amount after the stop operation of the internal combustion engine and reduces the rotational load of the internal combustion engine. It estimated, when the rotation speed of the internal combustion engine reaches a predetermined rotational speed, and is characterized in that to change the intake air amount to increase to a predetermined amount that is set based on the estimated rotational load . That is, the crank stop position of the internal combustion engine is controlled by controlling the piston stop position. The state of the internal combustion engine to be estimated includes, for example, a rotational load due to a moment of inertia and a rotational load such as an attached device.

  The internal combustion engine stop control method of the present invention configured as described above estimates the state of the internal combustion engine, for example, the rotational load acting on the internal combustion engine when the internal combustion engine is stopped, and the amount of air according to this rotational load. Since the intake air amount to the combustion chamber is changed by the changing means, it is possible to perform control to change the optimal intake air amount at the optimal time according to the state of the internal combustion engine, and to minimize vibration during the stop process of the internal combustion engine. It is possible to realize both the suppression to a stable position and the stable stop position control. As a result, when the internal combustion engine is restarted, the starter motor can be downsized and the exhaust gas can be reduced because the engine can be started in a short time with less energy.

In the stop control method for an internal combustion engine, it is preferable that the timing for changing the intake air amount is further changed based on the estimated rotational load of the internal combustion engine.

  According to the stop control method for an internal combustion engine of the present invention configured as described above, in the stop process of the internal combustion engine, first, the intake air amount is reduced to control to the minimum compression pressure and expansion pressure, thereby controlling the vibration of the internal combustion engine. When the internal combustion engine speed reaches a predetermined speed, the intake air amount can be increased and the piston can be stopped at a desired position. be able to.

  Further, as another preferred specific aspect of the stop control method for an internal combustion engine according to the present invention, the state of the internal combustion engine is a rotational load caused by an inertia moment of the internal combustion engine and a rotational load connected to the internal combustion engine. It is characterized by being. It is preferable that the rotational load is estimated from a rotational speed drop speed of the internal combustion engine. According to this configuration, the rotational load such as the inertia load of the internal combustion engine is estimated, and the intake air amount is changed according to the rotational load. Therefore, at the desired piston position, that is, at the desired crank position based on this position. Since the internal combustion engine can be stopped, vibrations can be reduced when the engine is stopped, and the internal combustion engine can be stopped at a position where it can be easily restarted.

  Furthermore, as another preferred specific aspect of the stop control method for an internal combustion engine according to the present invention, the air amount changing means is based on an estimated state of the internal combustion engine, an elapsed time from the start of the stop operation, or The timing for changing the intake air amount is changed according to the rotational speed of the internal combustion engine or the moving rotational angle of the internal combustion engine. According to this configuration, since the state of the stop process of the internal combustion engine is estimated and the change timing of the intake air amount is changed, the piston can be stopped at a desired piston position according to the state of the internal combustion engine.

  The air amount changing means may increase the increase amount of the intake air amount when the estimated rotational load is large, and decrease the increase amount of the intake air amount when the estimated rotational load is small. preferable. Specifically, for example, when the rotational load is large, the throttle is opened widely, and when the rotational load is small, the throttle is opened small. According to this configuration, the amount of increase in the intake air amount can be increased / decreased in accordance with the magnitude of the rotational load, so that vibration during stoppage can be reduced in accordance with the rotational load.

  Moreover, it is preferable to reduce the rotational load of the internal combustion engine as a subsequent process of changing the intake air amount. Furthermore, it is preferable to increase the rotational load of the internal combustion engine immediately before the stop of the internal combustion engine as a subsequent step of the step of changing the intake air amount. The rotation load is increased or decreased by connecting or disconnecting at least one of an alternator, a power steering pump, an air conditioner compressor, a water pump, a fuel pump, and a transmission oil pump. If the rotational load is reduced, the vibration of the internal combustion engine at the time of stop can be reduced, and if the rotational load is increased immediately before the stop, the rebound of the crankshaft rotation immediately before the stop can be reduced.

The stop control device for an internal combustion engine according to the present invention includes a reciprocating piston and an air amount changing means for changing an intake air amount into the combustion chamber, and changes the intake air amount into the combustion chamber so as to stop the piston. An internal combustion engine stop control device for controlling the internal combustion engine, the control device further comprising a state estimation means for estimating the rotational load of the internal combustion engine, the air amount changing means , after the stop operation of the internal combustion engine, reduced to a predetermined amount set in advance the amount of intake air, and then where the rotational speed of the internal combustion engine when it reaches the predetermined rotational speed was set based on the intake air quantity estimated rotational load in said state estimation means It is characterized by changing to increase the quantity. The internal combustion engine stop control device configured as described above reduces the intake air amount to a predetermined amount after the stop operation of the internal combustion engine , estimates the rotational load of the internal combustion engine by the state estimation means , and estimates the rotation In order to change the intake air amount to a predetermined amount based on the load , the piston can be stopped at a desired position in the middle of the stroke with low vibration, and can be easily restarted. Is optimal.

  The air amount changing means is preferably at least one of a throttle provided in an intake pipe of the internal combustion engine or an intake valve or an exhaust valve provided in a combustion chamber of the internal combustion engine. The air amount changing means preferably changes the intake air amount to the combustion chamber and changes the timing for changing the intake air amount. The piston can be stopped at a desired position by changing the intake air amount into the combustion chamber using at least one of the throttle, the intake valve, and the exhaust valve and changing the timing of changing the intake air amount.

  Further, the state estimation means estimates a rotational load acting on the internal combustion engine. That is, it is preferable to estimate the rotational load by combining the inertial load at the time of rotation of the internal combustion engine and the rotational load of auxiliary devices connected to the internal combustion engine. According to this configuration, the internal combustion engine can be stopped at a desired position according to the rotational load, and can be restarted with low energy.

  According to the stop control method and the stop control apparatus for an internal combustion engine of the present invention, when the internal combustion engine is stopped, the vibration of the internal combustion engine generated in the stop process is suppressed, and the change in the rotational load acting on the internal combustion engine or the machine difference The piston can be stably stopped at a desired stop position without being affected by the change in the stop motion of the internal combustion engine, and the startability of the internal combustion engine can be improved. And the exhaust gas at the time of restart can be reduced. Further, since the piston stop position is stable, the discrimination can be completed earlier than the cylinder discrimination at the normal start, and the control of the fuel injection valve can be easily performed.

  Hereinafter, an embodiment of a stop control method and a stop control device for an internal combustion engine according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a main part configuration diagram of an internal combustion engine to which the stop control device for an internal combustion engine according to the present embodiment is applied, and FIG. 2 is a main part configuration diagram of the internal combustion engine showing a block diagram of the control unit of FIG.

  1 and 2 show an internal combustion engine to which an embodiment of a stop control device according to the present invention is applied. 1 and 2, the internal combustion engine 1 is configured as, for example, a four-cycle engine mounted on an automobile, and includes a plurality of cylinders (cylinders) 2. Although only a single cylinder 2 is shown in FIG. 1, the other cylinders 2 have the same configuration. The number of cylinders 2 of the internal combustion engine 1 includes 3, 4, 6, 8, etc., which are referred to as 3, 4, 6, and 8 cylinders, respectively.

  An internal combustion engine 1 directly injects fuel from a fuel injection valve 4 into a combustion chamber 5 in a cylinder 2, and ignites (ignites) an air-fuel mixture of the injected fuel and air in the combustion chamber by an ignition plug 6. It is configured as an injection internal combustion engine. Here, an internal combustion engine in which the fuel injection valve 4 is attached to the intake passage 7 and the fuel and air are mixed in advance and then sucked into the combustion chamber 5 may be used. In addition, gasoline is preferably used as the fuel injected from the fuel injection valve 4, but other fuels may be used.

  Further, the internal combustion engine 1 is provided with an intake valve 9 and an exhaust valve 10 that open and close between the combustion chamber 5 and the intake passage 7 and the exhaust passage 8, respectively, and cams 11 and 12 that drive the valves 9 and 10, respectively. A throttle 13 for adjusting the intake air amount (intake air amount) from the intake passage 7, a connecting rod 15 for transmitting the reciprocating motion of the piston 3 to the crankshaft 14 as a rotational motion, and a crank arm 16 are provided. The opening / closing timing and lift amount of the intake valve 9 and the exhaust valve 10 can be freely changed by the valve timing / lift control device 20. At least one of the throttle 13, the intake valve 9 and the exhaust valve 10 constitutes an air amount changing means for controlling the intake air amount taken into the combustion chamber 5.

  The internal combustion engine 1 includes a starter motor 17 that can rotate the crankshaft 14 via a gear mechanism 18. The starter motor 17 may be a motor that can control the rotation (cranking) speed of the crankshaft 14 by controlling the supplied current or voltage. -You may use only the on / off control of supplied energy, without performing voltage control. Further, it is possible to equip the crankshaft 14 around the crankshaft 14 with a motor that transmits rotation through a belt, for example.

  The control unit 19 is configured as a computer including peripheral devices such as a microprocessor, a RAM, and a ROM, and performs various processes necessary for controlling the operating state of the internal combustion engine 1 according to a program recorded in the ROM. For example, the fuel injection amount of the fuel injection valve 4 is controlled so that the air-fuel ratio measured by the air-fuel ratio sensor 21 installed in the exhaust passage 8 becomes a predetermined air-fuel ratio.

  Various sensors other than the above-described sensors are provided as sensors to be referred to by the control unit 19, but the sensors related to the present invention include a crank angle sensor 24 that outputs a signal corresponding to the crank angle of the crankshaft 14, A cam angle sensor 25 for outputting a signal corresponding to the cam angle of the cam 11 on the intake side is provided. Here, it is desirable that the crank angle sensor 24 is capable of measuring the rotation angle of the crankshaft 14 in the rotation direction and the reverse rotation direction like a resolver used for motor rotation control.

  Next, one example of the control unit 19 of the present invention will be described with reference to FIG. The control unit 19 is necessary for processing to take in a signal from a sensor that detects a state necessary for starting, stopping, and operating the internal combustion engine 1 and for starting, stopping, and operating the internal combustion engine 1. In order to normally start and operate the internal combustion engine 1, the input / output means 30 for performing output processing for controlling the fuel injection valve 4, spark plug 6, throttle 13, valve timing / lift control device 20, etc. In addition to the control means (not shown), a start control means 31 and a stop control means 32 are provided.

  The start control means 31 is a control means such as a starter motor for starting the internal combustion engine 1, and the stop control means 32 is a control means for stopping the internal combustion engine 1. Further, the stop control means 32 is estimated by a combustion end control means 33 for controlling the end of combustion when the internal combustion engine 1 is stopped, a rotational load estimation means 34 for estimating a rotational load that causes variation in the stop position, and Three means of the air amount changing means 35 for controlling the amount of intake air to the combustion chamber 5 according to the rotational load are provided. The rotational load is a load obtained by adding the inertia load calculated from the inertia moment of the internal combustion engine 1 and the loads of the auxiliary devices connected to the internal combustion engine 1.

  Next, a control flow in stop control of the stop control device for an internal combustion engine according to the present invention will be described.

  Before describing the details of the control flow of stop control, a series of operation outlines from start to stop in the internal combustion engine 1 of the present invention will be described using the processing flow of FIG. The start control and stop control are executed by the start control means 31 and stop control means 32 of the control unit 19. Further, the control unit 19 determines whether to stop or start the internal combustion engine 1 in a process flow different from this process, and stop control or start control is executed based on the stop request or start request.

  Stop and start requests include starter switches, vehicle speed sensors, water temperature sensors, fuel pressure sensors, brake switches, transmission gear position sensors, brake negative pressure sensors, intake air temperature sensors, electric load switches (air conditioners, headlamps, radiator fans, etc.) This represents the usage status of the electric load), battery voltage, and the like. For example, the stop request is determined when the internal combustion engine 1 is in a warm-up state, a brake operation state, and an idling state where the accelerator is not stepped on.

  The start condition is determined when there is an operation related to the start of the vehicle from the stop state of the internal combustion engine 1, such as a brake release, an accelerator pedal depression operation, a clutch pedal depression operation, a shift operation, or the like. That is, the series of processing flow from the stop to the start shown in FIG. 3 realizes an idle stop that stops the internal combustion engine 1 when the vehicle is stopped and restarts the internal combustion engine 1 before starting the vehicle.

  In FIG. 3, first, the starter motor 17 is driven by the driver's key operation or the like to start the internal combustion engine 1 (S101), and the internal combustion engine is activated (S102). During the operation of the internal combustion engine 1, it is determined whether or not there is a stop request (S103). When there is no request to stop the engine, normal operation control is continued (S104), the internal combustion engine 1 continues to be in an operating state (S102), and it is determined again whether or not the engine is stopped. When there is a request to stop the engine, stop control (S105) is performed.

  The stop control (S105) is based on the combustion end control (S200) for stopping the combustion of the internal combustion engine 1, the rotational load estimation (S300) for estimating the rotational load acting on the internal combustion engine 1 during the stop operation, and the estimated rotational load. Air amount control (S400) for controlling the amount of intake air into the combustion chamber 5 of the internal combustion engine 1 is performed. Details of these processing contents will be described later. When the stop control (S105) is completed, stop position detection (S106) is performed based on information from the crank angle sensor 24 and the cam angle sensor 25. In this stop position detection, stop position information of the crankshaft 14 and stroke information of each cylinder necessary for realizing a quick restart of the internal combustion engine 1 are detected.

  The internal combustion engine 1 that has stopped rotating enters a halt state (S107) and waits until a restart request is determined (S108). At this time, the stop position information and stroke information of the crankshaft 14 detected by the stop position detection (S106) are held even when the internal combustion engine 1 is in a stopped state, and are kept until the power source of the control unit 19 is cut off.

  Next, the internal combustion engine 1 determines whether or not there is a restart request (S108). If there is no restart request, the internal combustion engine 1 continues to maintain the hibernation state (S107) and determines again whether or not there is a restart request. When there is a restart request, start control (S109) is performed, and the internal combustion engine 1 is restarted promptly. At this time, the restart of the internal combustion engine 1 can be performed by the method of starting using the cranking of the starter motor 17 or the combustion energy obtained by igniting after the fuel injection in the expansion stroke of the internal combustion engine 1 during the rotation stoppage. You may use the method of starting using. When the start control (S109) is completed, the operation state (S102) is resumed, and a stop request is awaited.

  Next, details of one embodiment relating to the stop control (S105) executed when there is a stop request in the operating state (S102) of the internal combustion engine 1 will be described. In the stop control, as described above, combustion end control (S200), rotational load estimation (S300), and air amount control (S400) are executed.

  First, the processing flow of one embodiment of the combustion end control (S200) in the stop control (S105) will be described with reference to FIG. The combustion end control (S200) is first executed in the stop control (S105), and controls the end of combustion in order to stop the internal combustion engine 1. When the combustion end control is started (S201), it is determined whether fuel injection is performed in a predetermined cylinder (S202). If it is determined that the cylinder is not the predetermined cylinder, the determination is repeated until fuel injection is performed in the predetermined cylinder. When it is determined that the fuel injection is performed in the predetermined cylinder, the fuel supply is stopped (S203). At this time, even if all cylinders are stopped at the same time, for example, in the case of an in-line four-cylinder type internal combustion engine, the fuel is stopped in the order of fuel injection such as the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder. May be.

  Next, when the fuel supply stop (S203) is performed, it is determined whether or not the combustion has ended (S204). In this combustion end determination (S204), it is determined that the fuel supply stop of each cylinder has been completed, and if it is determined that the fuel supply stop has not been completed, the fuel supply stop (S203) is continued. To do. When it is determined that the fuel supply stop for all cylinders has been completed, air amount control (S205) is performed. Here, the ignition may be stopped for the cylinder determined to have ended the combustion, or the ignition may be stopped after the rotation of the internal combustion engine 1 is stopped. However, in a cylinder that has injected fuel, it is desirable to ignite and generate combustion in order to prevent exhaust deterioration.

  In the air amount control (S205), the amount of air taken into the combustion chamber 5 is reduced by controlling the throttle 13, the intake valve 9, the exhaust valve 10, or the like. As a result, the amount of intake air into the combustion chamber 5 of the internal combustion engine 1 is reduced, and the compression pressure and the expansion pressure can be suppressed. Therefore, it is possible to suppress the rotational fluctuation and reduce the vehicle vibration. Further, by suppressing the rotational fluctuation, it is expected that the estimation accuracy of the rotational load estimation described below is improved. When the air amount control (S205) is completed, the combustion end control is completed (S206).

  Next, an example of a processing flow of rotational load estimation (S300) in stop control (S105) will be described with reference to FIGS. In the rotational load estimation (S300), the rotational load of the internal combustion engine 1 that affects the stop position of the internal combustion engine 1 is estimated. As an example of the method, the rotational load is estimated from the rotational speed drop speed. This is because it can be considered that in the stop process of the internal combustion engine 1 after completion of combustion, the kinetic energy of the internal combustion engine 1 is taken away by the rotational load, so that the rotational speed of the internal combustion engine 1 decreases.

FIG. 5 shows an example of a processing flow related to the rotational load estimation method.
When the rotational load estimation is started (SA301), it is determined whether the rotational speed of the internal combustion engine 1 is equal to or lower than a predetermined rotational speed NeA (SA302). If the rotational speed is greater than NeA, the determination is repeated until the condition is satisfied. When the rotational speed is equal to or lower than NeA, the rotational speed Ne1 at that time and the elapsed time T1 from the end of combustion are measured (SA303). Subsequently, it is determined whether or not the rotational speed of the internal combustion engine 1 is equal to or less than a predetermined rotational speed NeB (SA304). If the rotational speed is greater than NeB, the determination is repeated until the condition is satisfied. If the rotational speed is equal to or less than NeB, The rotational speed Ne2 at that time and the elapsed time T2 from the end of combustion are measured (SA305). After the measurement of the rotational speed and elapsed time at the two points is completed, the rotational speed descent speed is obtained by equations (1), (2), and (3) (SA306).

Rotational speed descent speed = ΔNe / ΔT Equation (1)
ΔNe = (Ne2-Ne1) Formula (2)
ΔT = (T2-T1) Equation (3)
Formula (1) calculates | requires the rotation speed change per unit time.

Thereafter, using the calculated rotational speed descent speed, the conversion map shown in FIG. 11 or the following equation (4)
Rotational load = Inertia moment around crankshaft J × ΔNe / ΔT Equation (4)
The rotational load is estimated by (SA307), and the rotational load estimation process is terminated (SA308). The conversion map of FIG. 11 represents the rotational load with respect to the rotational speed drop speed ΔNe, and is an example in the case where the moment of inertia J around the crankshaft 14 corresponds to 0.15 kgm ² in equation (4). It represents that the rotational load acting on the crankshaft 14 increases as the rotational speed decrease speed increases. Thus, the state of the internal combustion engine 1 is estimated by estimating the rotational load from the rotational speed drop speed.

Furthermore, FIG. 6 shows another embodiment of the processing flow related to the rotational load estimation method.
When the rotational load estimation is started (SC301), it is determined whether or not a predetermined time T1 has elapsed since the end of combustion of the internal combustion engine 1 (SC302). If the elapsed time is shorter than T1, the determination is repeated until the condition is satisfied. When the elapsed time reaches T1, the rotation speed Ne1 at that time is measured (SC303). Subsequently, it is determined whether or not the elapsed time from the end of combustion of the internal combustion engine 1 has passed the predetermined time T2 (SC304). If the elapsed time is shorter than T2, the determination is repeated until the condition is satisfied, and the elapsed time reaches T2. When it reaches, the rotation speed Ne2 at that time is measured (SC305). After measuring the rotational speed at two points, the rotational speed descent speed is obtained by equations (1), (2), and (3) (SC306). Thereafter, the rotational load is estimated by using the calculated rotational speed descent speed according to the conversion map shown in FIG. 11 or Equation (4) (SC307), and the rotational load estimation process is terminated (SC308).

  Finally, a processing flow of air amount control (S400) in stop control (S105) will be described with reference to FIG. In the air amount control (S400), control is performed to stop the crankshaft 14 of the internal combustion engine 1 at a predetermined position by changing the amount of air sucked into the combustion chamber 5 in accordance with the rotational load. First, when the air amount control is started (S401), the intake air amount P to be taken into the combustion chamber 5 is calculated according to the estimated rotational load estimated in the previous stage (S402). Next, the operation amount Q of the air amount changing means for realizing the air amount P is calculated (S403).

  In order to calculate the intake air amount P from the estimated rotational load and the operation amount Q from the intake air amount P, a conversion map shown in FIG. Here, the air amount changing means is the throttle 13, the intake valve 9 or the exhaust valve 10, or a combination thereof, and the operation amount Q is the throttle opening, the intake valve 9 or the exhaust valve 10 respectively. Corresponds to lift amount or phase angle. Subsequently, a change timing R of the intake air amount into the combustion chamber 5 corresponding to the estimated rotational load is calculated (S404).

  In accordance with the change time R, an operation time S for operating the air amount changing means is calculated (S405). In order to calculate the change time R from the estimated rotational load and the operation time S from the change time R, a conversion map shown in FIG. Here, the change timing R and the operation timing S are the elapsed time from the end of combustion, the rotational speed of the internal combustion engine 1, or the rotational rotation angle of the crankshaft 14 from the end of combustion. The map for converting the change time R to the operation time S takes into account the time delay of the response of the intake air amount to the operation of the air amount changing means. The moving rotation angle corresponds to the rotation angle of the crankshaft after the stop operation.

  By the processing so far, the operation amount Q and the operation timing S of the air amount changing means for controlling the stop position are obtained. Thereafter, the air amount changing means is operated according to the calculation result. It is determined whether the operation of the air amount changing means is the operation time S (S406). If the condition is not satisfied, the determination is repeated. If the conditions are satisfied, the air amount changing means is changed to the operation amount Q (S407). ), The air amount control is completed (S408). Thereafter, when the rotation of the internal combustion engine 1 stops, the operation amount of the air amount changing means is made equal to the value at the time of restart or the normal idle operation.

  Here, in this processing flow, the operation amount Q and the operation timing S of the air amount changing means are determined after estimating the rotation load from the rotation descent speed, but in FIG. 12 (B) and FIG. 13 (B). As shown, the operation amount Q and the operation timing S of the air amount changing means may be calculated directly from the rotational descending speed. Further, the engine stop determination (engine stop determination) may be performed as an engine stop determination for idling stop, which is different from the engine stop determination performed when the engine is stopped normally. Here, the intake air amount P to be sucked into the combustion chamber 5 is calculated according to the estimated rotational load, and the operation amount Q of the air amount changing means is calculated. However, when the air amount changing means is the throttle 13 The intake pipe pressure may be controlled to be a predetermined value. This is because there is a correlation between the intake pipe pressure and the intake air amount into the combustion chamber 5, that is, the maximum compression pressure in the compression stroke.

  FIGS. 8, 9, and 10 show examples of time charts when the stop control of the internal combustion engine 1 is performed based on the stop control process flow of FIGS. FIG. 8 shows an example of a normal rotational load, FIG. 9 shows an example when the rotational load increases, and FIG. 10 shows an example when the rotational load decreases. Here, the throttle 13 is used as means for changing the air amount.

  First, stop control in a normal rotational load will be described using the time chart of FIG. In section A in which the internal combustion engine 1 is operating, it is determined whether or not there is a request to stop the internal combustion engine 1 according to various conditions. When there is a stop request at time X, stop control is started. In the stop control, the combustion is finished and the throttle opening is changed from TVO1 to TVO2 in order to reduce the intake air amount. TVO1 is a throttle opening degree that maintains an idle state when the internal combustion engine 1 is idling, and TVO2 is used to suppress the rotational vibration of the internal combustion engine 1 by reducing the compression pressure and the expansion pressure in the stop process. Throttle opening. The processing so far corresponds to the steps from S102 to S200 in the processing flow of FIG. The throttle opening TVO2 may be fully closed.

  Next, in the process in which the kinetic energy of the internal combustion engine 1 is gradually taken away by the rotational load and the rotational speed decreases (section B), first, the rotational downward speed is calculated from ΔNe and ΔT1, and the rotational load is calculated from the rotational speed downward speed. Is estimated. The rotational load is estimated by the method described above. The rotational load is a load obtained by combining the inertial load due to the moment of inertia of the internal combustion engine 1 and the rotational load of the auxiliary devices attached to the internal combustion engine 1.

  Further, the operation amount Q and the operation timing S of the air amount changing means corresponding to the estimated rotational load are calculated. In this embodiment, the operation timing is determined based on the rotational speed of the internal combustion engine 1. In other words, when the rotational speed of the internal combustion engine 1 is equal to or lower than the predetermined rotational speed, the intake air amount change control is performed. For example, if the rotation speed of the internal combustion engine 1 is Nej1 when the throttle 13 for controlling the intake air amount to the optimum amount to stabilize the stop position is assumed to be Nej1, in FIG. The rotational speed becomes Nej1, and it is determined that the operation time S has been reached. Here, if it is determined that the operation timing S has been reached, the amount of air taken into the combustion chamber 5 of the internal combustion engine 1 is optimized in order to stabilize the stop position from the controlled throttle opening TVO2 for vibration suppression. Change to throttle opening TVO3. The processing so far corresponds to steps S300 and S400 of the processing flow of FIG.

  By changing the throttle opening from TVO2 to TVO3, a predetermined amount of air is drawn into the combustion chamber 5 of the internal combustion engine 1 (section C), the compression pressure and the expansion pressure increase, and the crankshaft 14 of the internal combustion engine 1 Stop at a predetermined position (time Z). After the rotation is stopped, the throttle 13 changes the opening degree from TVO3 to the opening degree at the time of restart or TVO4 which is the opening degree equivalent to that at the time of normal stop, and the stop control is finished. At time Z, the crank angle is about 280 to 300 degrees, and the piston position of the predetermined cylinder is in the middle of the expansion stroke, so that it can be started in a short time at the next restart, and energy consumption is reduced. The position at which the predetermined piston is stopped is preferably 60 to 120 degrees or 240 to 300 degrees in terms of crank angle.

  Next, FIG. 9 shows a time chart of the stop control when the rotational load increases compared to the normal case. Due to the increase in rotational load, the time required for the same rotational speed drop ΔNe in section B1 is ΔT1 in the case of a normal rotational load, whereas it becomes as short as ΔT2 when the load increases. As a result, it is estimated that the rotational load is increasing as described above. In order to stabilize the stop position in response to the increase in the rotational load, it is necessary to increase the air sucked into the combustion chamber 5 of the internal combustion engine 1 more than the stop control in the case of the normal rotational load shown in FIG. is there.

  Therefore, as shown in FIG. 9, when it is estimated that the rotational load has increased, a command is output to open the throttle opening to TVO3U larger than the throttle opening TVO3 in the case of the normal rotational load. Opens greatly. In addition, when the rotational load is large, the rotational speed decreases more quickly. Therefore, it is necessary to make the timing for operating the throttle opening earlier than in the case of the normal rotational load. The timing for switching from the throttle opening TVO2 set for performing vibration suppression in the section B1 to the throttle opening TVO3U for stabilizing the stop position is defined as the rotational speed Nej2 of the internal combustion engine 1. The determined rotational speed Nej2 is higher than the determined rotational speed Nej1 in the case of a normal rotational load, and as a result, control for changing the intake air amount from a state in which the rotational speed of the internal combustion engine 1 is higher than in the case of a normal rotational load. Done.

  Furthermore, FIG. 10 shows a time chart of stop control when the rotational load is reduced as compared with the normal case. Due to the decrease in the rotational load, the time required for the same rotational speed drop ΔNe in the section B2 is ΔT1 in the case of the normal rotational load, whereas it becomes longer as ΔT3 when the load is decreased. As a result, it is estimated that the rotational load is reduced as described above. In order to stabilize the stop position in response to the reduction of the rotational load, it is possible to reduce the air sucked into the combustion chamber 5 of the internal combustion engine 1 as compared with the stop control in the case of the normal rotational load shown in FIG. It is. If the amount of intake air can be reduced, vibration during stoppage can be further reduced. Therefore, it is preferable to reduce the amount of intake air as much as possible.

  Therefore, as shown in FIG. 10, when it is estimated that the rotational load is reduced, a command to open the throttle opening to TVO3D smaller than the throttle opening TVO3 in the case of the normal rotational load is output. Opens small. Further, when the rotational load is small, the decrease in rotation is delayed, and therefore the timing for operating the throttle opening needs to be delayed as compared with the case of the normal rotational load. The timing for switching from the throttle opening TVO2 set for performing vibration suppression in the section B2 to the throttle opening TVO3D for stabilizing the stop position is defined as the rotational speed Nej3 of the internal combustion engine 1. The determined rotational speed Nej3 is lower than the determined rotational speed Nej1 in the case of a normal rotational load, and as a result, control for changing the intake air amount from a state where the rotational speed of the internal combustion engine 1 is lower than in the case of a normal rotational load. Done.

  As described above, as shown in the time charts of FIGS. 8, 9, and 10, the stop control is realized from two phases of vibration suppression control and stop position stabilization control. Sections B, B1, and B2 shown in FIGS. 8, 9, and 10 correspond to vibration suppression control, and section C corresponds to stop position stabilization control. In the vibration suppression control, the amount of intake air into the combustion chamber 5 is decreased by closing the throttle opening, and the vibration is suppressed by reducing the compression and expansion pressures.

  On the other hand, in the stop position stabilization control, by increasing the intake air amount into the combustion chamber 5 by opening the throttle opening, the pressure of compression and expansion is increased, and the influence of other factors affecting the stop position is affected. By making it relatively small, the stop position is stabilized by making the torque balance between compression and expansion the main factor. Thus, the vibration suppression control and the stop position stabilization control perform contradictory air amount control. For this reason, it is desirable that the switching time (time Y) for increasing the air amount for stabilizing the stop position from the vibration suppression control is performed as much as possible immediately before the stop.

  In the above-described embodiment, the idle stop has been described as an example. However, the same control is performed even when the internal combustion engine 1 is stopped due to the ignition off, and the piston is stopped at a desired stop position, so that the desired crank position is reached. Therefore, the next start can be easily achieved in a short time. As a result, exhaust gas reduction can be achieved at the same time.

  In the stop control method for an internal combustion engine according to the present invention, it is preferable to reduce the rotational load of the internal combustion engine as a subsequent step of the step of changing the intake air amount in the stop process of the internal combustion engine after the stop request. Although not shown, after the stop control (S105) of FIG. 3, for example, the connection between the power steering pump and the internal combustion engine 1 is released to reduce the rotational load of the internal combustion engine 1. In this way, when the rotational load of the internal combustion engine is reduced during the stop process of the internal combustion engine, the vibration of the internal combustion engine 1 at the time of stop can be further reduced.

  Further, in the stop control method for an internal combustion engine according to the present invention, as a step after the step of changing the intake air amount, immediately before the stop of the internal combustion engine, the rotational load of the internal combustion engine is increased and the crankshaft is swung back immediately before the stop. Can be reduced. In this case, although not shown, after the stop control (S105) in FIG. 3, for example, a power steering pump is connected to increase the rotational load of the internal combustion engine 1. When the rotational load is increased just before the internal combustion engine 1 is stopped, the rotational speed immediately before the crankshaft is stopped can be attenuated, the crankshaft can be reduced, and the stop time can be shortened.

  As described above, when the rotational load of the internal combustion engine 1 is increased or decreased after the intake air amount is changed, the alternator, the power steering pump, the air conditioner compressor, the water pump, the fuel pump, and the transmission oil pump. It is preferable to interrupt at least one of the above. By connecting or disconnecting these auxiliary devices, the rotational load of the internal combustion engine 1 can be increased or decreased.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed. For example, as an example of changing the intake air amount when the internal combustion engine is stopped, the throttle is used. However, the intake air amount may be changed by an intake valve or other means.

  As an example of estimating the state of the internal combustion engine, an example of the rotational load that combines the rotational load calculated from the moment of inertia and the loads of auxiliary devices such as a pump and a compressor is shown. The state of the internal combustion engine may be estimated by detecting the outside air temperature or the like. Moreover, you may use the rotation load which added the said rotation load.

  As an application example of the present invention, the above-described stop control device for an internal combustion engine can be installed in a diesel engine, and can also be applied to a use of a gaseous fuel engine using LPG or the like as fuel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a main part of an internal combustion engine applied to an internal combustion engine stop control device according to an embodiment of the present invention. The block diagram which shows the control unit of the stop control apparatus shown in FIG. The flowchart which shows the outline | summary of the stop and start method of the internal combustion engine shown to FIG. The flowchart which shows the process of the combustion end control in the stop control shown in FIG. The flowchart which shows the process of rotational load estimation in the stop control shown in FIG. FIG. 4 is another flowchart showing a rotational load estimation process in the stop control shown in FIG. 3. The flowchart which shows the process of the air quantity control in the stop control shown in FIG. The time chart which shows the rotation speed of the internal combustion engine at the time of normal rotation load in the stop process of an internal combustion engine, a crank angle, and a throttle opening. The time chart which shows the rotation speed of the internal combustion engine at the time of the rotation load increase in the stop process of an internal combustion engine, a crank angle, and a throttle opening. The time chart which shows the rotation speed of the internal combustion engine at the time of rotation load reduction in the stop process of an internal combustion engine, a crank angle, and a throttle opening. 7 is a conversion map of rotational load estimation with respect to the rotational speed descent speed shown in FIGS. The conversion map of the amount of intake air with respect to rotation load, and the conversion map of the operation amount of the air amount change means with respect to the amount of intake air. The conversion map of the air amount change time with respect to a rotational load, and the conversion map of the operation time of the air amount change means with respect to the air amount change time

Explanation of symbols

  1: internal combustion engine, 2: cylinder, 3: piston, 4: fuel injection valve, 5: combustion chamber, 6: spark plug, 9: intake valve (intake valve), 10: exhaust valve (exhaust valve), 13: throttle (Air amount change means), 14: crankshaft, 19: control unit, 31: start control means, 32: stop control means, 33: fuel end control means, 34: rotational load estimation means, 35: air quantity change means

Claims (12)

A stop control method for an internal combustion engine, comprising: a reciprocating piston; and an air amount changing means for changing an intake air amount into a combustion chamber, wherein the stop position of the piston is controlled by changing the intake air amount,
Said air amount changing means, after the stop operation the internal combustion engine, wherein the estimating the rotational load of the internal combustion engine while reducing to a predetermined amount set the intake air amount in advance, and then a predetermined number of revolutions speed of the internal combustion engine When the engine reaches the value, the intake air amount is changed to increase to a predetermined amount set based on the estimated rotational load . Said air amount changing means based on said rotational load of the estimated said internal combustion engine further stop control method for an internal combustion engine according to claim 1, characterized in that said changing the timing for changing the intake air amount . The rotational load may stop control method for an internal combustion engine according to claim 1 or 2, characterized in that it is estimated from the rotational speed lowering speed of the internal combustion engine. The air amount changing means determines the intake air amount based on the estimated rotation load of the internal combustion engine, the elapsed time from the start of a stop operation, the rotational speed of the internal combustion engine, or the moving rotational angle of the internal combustion engine. The stop control method for an internal combustion engine according to any one of claims 1 to 3 , wherein the time for changing is changed. The air amount changing means increases the increase amount of the intake air amount when the estimated rotational load is large, and decreases the increase amount of the intake air amount when the estimated rotational load is small. The stop control method for an internal combustion engine according to any one of claims 1 to 4 . As a step after the step of changing the intake air amount, the engine stop control method according to any one of claims 1 to 5, characterized in that to reduce the rotational load of the internal combustion engine. The internal combustion engine stop according to any one of claims 1 to 6 , wherein the rotational load of the internal combustion engine is increased immediately before the internal combustion engine is stopped as a subsequent step of the step of changing the intake air amount. Control method. The increase or decrease of the rotational load, the alternator, power steering pump, air conditioning compressor, water pump, fuel pump, according to claim 6 or 7, wherein the connecting and disconnecting at least one of the oil pump for the transmission A stop control method for an internal combustion engine according to claim 1. A stop control device for an internal combustion engine, comprising: a reciprocating piston; and an air amount changing means for changing an intake air amount into the combustion chamber, wherein the stop position of the piston is controlled by changing the intake air amount,
The control device further includes state estimation means for estimating a rotational load of the internal combustion engine,
Said air amount changing means, after the stop operation the internal combustion engine, reduced to a predetermined amount set in advance the intake air amount, and then when the rotational speed of the internal combustion engine reaches a predetermined rotational speed, the intake air amount A stop control device for an internal combustion engine, wherein the stop control device is changed so as to increase to a predetermined amount set based on the rotational load estimated by the state estimating means . The air amount changing means further changes a timing for changing the intake air amount based on the estimated rotational load due to the inertia moment of the internal combustion engine and the rotational load connected to the internal combustion engine. The stop control device for an internal combustion engine according to claim 9 . The air amount changing means is at least one of a throttle provided in an intake pipe of the internal combustion engine or an intake valve or an exhaust valve provided in a combustion chamber of the internal combustion engine. The stop control device for an internal combustion engine according to 9 or 10 . The stop of the internal combustion engine according to any one of claims 9 to 11 , wherein the air amount changing means changes the intake air amount into the combustion chamber and changes the timing of changing the intake air amount. Control device.

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