JP2008291784A - Stop control device and stop control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stop control device and a stop control system for an internal combustion engine for further smoothly stopping rotation of the internal combustion engine. <P>SOLUTION: In addition to adjustment of a degree of combustion by combustion system accessories (for example, a throttle valve and a fuel injection valve) in S14, S20 when the presence of the stop instruction (YES in S10) is determined, a stop control in which at least any one of adjustment of an exhaust load by exhaust system accessories (for example, a supercharger) and adjustment of an output shaft load by drive system accessories (for example, an alternator, a fuel pressure feed pump, and a refrigerant compressor) is performed. Therefore, a lowering rate of a revolution speed is reduced in a bandwidth immediately before stop including a point where the revolution speed of the crankshaft becomes zero, compared with a second bandwidth immediately before stop before that. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a stop control device and a stop control system for an internal combustion engine that perform stop control of rotation of the internal combustion engine.

As this type of control device, for example, as seen in Patent Document 1 below, after the ignition switch is turned off, the flow of an exhaust gas recirculation passage (EGR passage) that connects the exhaust system and the intake system of the diesel engine is communicated. Some have also been proposed that increase the road area and increase the recirculation displacement (EGR amount). As a result, the amount of exhaust gas recirculated to the combustion chamber of the diesel engine increases, so that combustion in the combustion chamber is suppressed, and as a result, stoppage of the diesel engine is promoted. Moreover, the stop of the diesel engine is promoted by cutting the fuel injection.
JP 59-43952 A

  By the way, when the rotation of the diesel engine is suddenly stopped, it has been found by the inventor that a phenomenon in which the rotational fluctuation of the output shaft becomes remarkable can occur. This is considered due to the fact that, depending on the rotation angle of the output shaft when the rotation speed of the output shaft of the diesel engine is substantially zero, the force for rotating the output shaft in the reverse direction becomes large. Specifically, when the piston tries to stop near the compression end position (compression top dead center position), the compressed gas in the combustion chamber tries to push the piston back, thereby rotating the output shaft in the reverse direction. It is thought that the power to try to make it arise.

  On the other hand, it is conceivable to gradually decrease the rotational speed when stopping the diesel engine by gradually increasing the EGR amount or gradually performing the fuel injection cut. According to this, when the piston tries to stop near the compression end position, it takes a long time for the compressed gas in the combustion chamber to leak from the sliding gap such as the piston ring. Therefore, the leakage amount of the compressed gas increases, the force that the compressed gas tries to push back the piston can be reduced, and the rotation fluctuation at the stop can be suppressed.

  However, the inventor has also found that the rotational fluctuation of the output shaft becomes significant in a predetermined rotational speed band lower than the idle rotational speed band. This phenomenon is considered to occur in a rotation speed band corresponding to a resonance frequency band of a flywheel connected to the output shaft in order to suppress the rotational fluctuation of the diesel engine. That is, the rotational speed band corresponding to the resonance frequency band of the flywheel is normally designed to be within the rotational speed band lower than the idle rotational speed band while avoiding the rotational speed band during operation of the diesel engine. For this reason, if the decrease speed of the rotational speed when the diesel engine is stopped is small, the time for staying in the rotational speed band becomes long, and the rotational fluctuation of the output shaft becomes large.

  Even in a diesel engine not provided with the flywheel, there may be a resonance frequency band due to other members connected to the output shaft. There arises a problem that the rotation fluctuation of the output shaft due to the increase in length becomes large. Further, a similar problem can occur in a gasoline engine when the engine is stopped.

  The present invention has been made to solve the above problems, and an object thereof is to provide a stop control device and a stop control system for an internal combustion engine that can more smoothly stop the rotation of the internal combustion engine. .

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  According to the first aspect of the present invention, there are provided stop determination means for determining whether or not there is a stop command for the internal combustion engine, and a combustion system auxiliary device for adjusting the degree of combustion by controlling the state of the air-fuel mixture supplied to the combustion chamber of the internal combustion engine. Auxiliary control means for controlling the drive of at least one of the exhaust system auxiliary machine that controls the exhaust state of the internal combustion engine and the drive system auxiliary machine driven by the output shaft, The auxiliary equipment control means adjusts the degree of combustion by controlling the combustion system auxiliary equipment when the stop judgment means judges that the stop command is present, and the exhaust system auxiliary equipment Stop control for adjusting at least one of adjustment of the exhaust load by controlling the drive of the engine and adjustment of the output shaft load by controlling the drive of the drive system auxiliary machine, and rotation of the output shaft of the internal combustion engine Speed There in a given first immediately before stop band including a point where the zero, and wherein the reducing the rate of decrease in the rotational speed of the output shaft compared to the previous second before stopping band.

  According to this, in the zone immediately before the first stop, the rotational speed reduction speed (positive when the rotational speed change speed is negative) is reduced as compared with the previous zone immediately before the second stop. The internal combustion engine is stopped in a state in which the decrease rate of the engine is moderated. Therefore, the rotation fluctuation of the output shaft that occurs when the engine is suddenly stopped can be reduced, and the rotation of the internal combustion engine can be stopped smoothly.

  In addition, since the speed of decrease in the zone immediately before the second stop is larger than that in the zone immediately before the first stop, the resonance frequency band in which the fluctuation of the rotational speed of the internal combustion engine is particularly remarkable exists in the zone immediately before the second stop. Even if it exists, the resonant frequency band can be passed quickly. Therefore, the time spent in the resonance frequency band can be shortened, and consequently the rotation fluctuation of the output shaft can be reduced.

  Further, according to the present invention, in addition to adjusting the degree of combustion by the combustion system auxiliary machine, the stop control is performed by adjusting at least one of the adjustment of the exhaust load by the exhaust system auxiliary machine and the adjustment of the output shaft load by the drive system auxiliary machine. Execute. For this reason, the number of adjusting means is increased as compared with the case where stop control is executed only by adjusting the degree of combustion. Therefore, it is possible to easily realize the above-described stop control in which the rotational speed reduction speed is small in the band immediately before the first stop and large in the band immediately before the second stop.

  According to a second aspect of the present invention, in addition to suppressing the degree of combustion in the zone immediately before the second stop, the auxiliary machine control means determines the degree of load of at least one of the exhaust load and the output shaft load. The stop control is executed so as to be larger than the degree immediately before the stop control is executed.

  Therefore, in the zone immediately before the second stop, the rate of decrease can be increased compared to the case where the rate of decrease in the rotational speed is increased only by suppressing the degree of combustion. Therefore, when a resonance frequency band exists in the band immediately before the second stop, the time spent in the resonance frequency band can be shortened, and the rotational fluctuation of the output shaft that occurs in the resonance frequency band can be reduced.

  According to a third aspect of the present invention, the exhaust system auxiliary machine includes a turbine disposed in the exhaust passage and rotated by exhaust pressure, and a compressor disposed in the intake passage and rotated integrally with the turbine to pressurize the intake air. The auxiliary machine control means controls the flow rate of the exhaust gas flowing into the turbine from the combustion chamber of the internal combustion engine when executing the stop control. The degree of the exhaust load is controlled.

  According to this, the flow rate of the exhaust gas flowing into the turbine can be applied as a control parameter when executing the stop control. That is, by increasing the turbine inflow exhaust flow rate and increasing the degree of exhaust load, the stoppage of the internal combustion engine can be promoted to increase the rotational speed decrease rate. Further, by decreasing the turbine inflow exhaust flow rate to reduce the degree of exhaust load, it is possible to suppress the stop of the internal combustion engine and lower the rotational speed decrease rate.

  According to a fourth aspect of the present invention, the drive system auxiliary machine includes at least a generator that generates electric power by the rotational force of the output shaft, and the auxiliary machine control means performs the stop control when the stop control is performed. The degree of the output shaft load is controlled by controlling the amount of power generated by the generator.

  According to this, the power generation amount can be applied as a control parameter when executing stop control. That is, by increasing the amount of power generation and increasing the degree of output shaft load, the stoppage of the internal combustion engine can be promoted to increase the rotational speed reduction speed. In addition, by reducing the amount of power generation and reducing the degree of output shaft load, it is possible to suppress the stop of the internal combustion engine and lower the rotational speed reduction speed.

  According to a fifth aspect of the present invention, the drive system auxiliary machine includes at least a fuel pressure feed pump that discharges the fuel at a high pressure, and the auxiliary machine control means performs the stop control when the fuel control pump performs the stop control. The degree of the output shaft load is controlled by controlling the fuel discharge flow rate by the pressure pump.

  According to this, the fuel discharge flow rate can be applied as a control parameter when executing the stop control. That is, by increasing the fuel discharge flow rate and increasing the degree of the output shaft load, it is possible to promote the stoppage of the internal combustion engine and increase the rotational speed decrease rate. In addition, by decreasing the fuel discharge flow rate and reducing the degree of output shaft load, it is possible to suppress the stop of the internal combustion engine and lower the rotational speed decrease rate.

  According to a sixth aspect of the present invention, the drive system auxiliary machine includes at least a refrigerant compressor that compresses and discharges the refrigerant flowing through the refrigerant passage of the air conditioner, and the auxiliary machine control means includes the stop In executing the control, the degree of the output shaft load is controlled by controlling the refrigerant discharge flow rate by the refrigerant compressor.

  According to this, the refrigerant discharge flow rate can be applied as a control parameter when executing stop control. That is, by increasing the refrigerant discharge flow rate and increasing the degree of the output shaft load, it is possible to promote the stop of the internal combustion engine and increase the rotational speed decrease rate. Further, by decreasing the refrigerant discharge flow rate and reducing the degree of the output shaft load, it is possible to suppress the stop of the internal combustion engine and lower the rotational speed decrease rate.

  According to a seventh aspect of the present invention, the combustion system auxiliary machine includes at least a fuel injection valve that supplies fuel to the internal combustion engine, and the auxiliary machine control means performs the stop control when the stop control is performed. The combustion degree is controlled by controlling the fuel injection amount by the fuel injection valve.

  According to this, the fuel injection amount can be applied as a control parameter when executing the stop control. That is, the rate of decrease in the rotational speed can be controlled by controlling the degree of combustion by controlling the degree to which the fuel injection amount is reduced or the timing for cutting.

  According to an eighth aspect of the present invention, the combustion system auxiliary machine includes at least a throttle valve for adjusting an intake flow rate supplied to a combustion chamber of the internal combustion engine, and the auxiliary machine control means includes the stop control. Is performed, the degree of combustion is controlled by controlling the intake flow rate by the throttle valve.

  According to this, the intake air flow rate can be applied as a control parameter when executing the stop control. That is, the rate of decrease in the rotational speed can be controlled by controlling the degree of combustion by controlling the degree to reduce the intake flow rate or the timing to cut.

  The invention according to claim 9 is a target value for the rotational speed of the output shaft after the rotational speed calculating means for calculating the actual rotational speed of the output shaft and the stop determining means determines that the stop command is present. Target value setting means for setting the value, and after the auxiliary machine control means determines that the stop command is present, the actual rotation speed calculated by the rotation speed calculation means becomes the target value. The feedback control is performed as described above. Therefore, it is possible to accurately perform the above-described stop control in which the decrease rate of the rotation speed is increased in the band immediately before the second stop and decreased in the band immediately before the first stop.

  Here, of the above-described stop control in which the decrease speed is increased in the band immediately before the second stop and decreased in the band immediately before the first stop, the control in the band immediately before the first stop is the rotation fluctuation that occurs when the stop is suddenly stopped. In order to reduce it, it is required to control with particularly high accuracy. Therefore, it is desirable to perform the feedback control at least in the band immediately before the first stop as in the invention described in claim 10.

  In the invention described in claim 11, a flywheel for reducing rotational fluctuation of the output shaft is attached to the output shaft, and the band immediately before the second stop corresponds to a resonance frequency band of the flywheel. A rotation speed band is included.

  The invention according to claim 12 is characterized in that the internal combustion engine is a compression ignition type internal combustion engine (diesel engine). In the case of a diesel engine, the compression ratio in the combustion chamber is higher than that in a spark ignition type internal combustion engine (gasoline engine). Therefore, when the operation with such a high compression ratio is stopped, the problem of rotational fluctuation of the output shaft becomes remarkable. appear. Therefore, according to the present invention for a diesel engine, the various effects described above can be suitably achieved.

  According to a thirteenth aspect of the present invention, the internal combustion engine stop control device, the combustion system auxiliary device, and at least one of the exhaust system auxiliary device and the drive system auxiliary device are provided. 1 is a stop control system for an internal combustion engine. According to this stop control system, the above-described various effects can be similarly exhibited.

  Hereinafter, an embodiment in which a stop control device for an internal combustion engine according to the present invention is applied to a stop control device for a common rail vehicle-mounted diesel engine will be described with reference to the drawings.

  FIG. 1 shows the overall configuration of the engine system according to the present embodiment.

  As shown in the figure, an intake passage 12 of a multi-cylinder (here, 4 cylinders) diesel engine 10 is provided with an electronically controlled throttle valve 14 formed of a butterfly valve body. The throttle valve 14 is of a normally open type. An opening sensor 16 that detects the opening of the throttle valve 14 is provided in the vicinity of the throttle valve 14.

  The intake passage 12 communicates with a combustion chamber 24 defined by the cylinder block 20 and the piston 22 by opening the intake valve 18. A tip of a fuel injection valve 28 to which high pressure fuel is supplied from a common rail 26 protrudes from the combustion chamber 24. As a result, fuel can be supplied to the combustion chamber 24 by injection.

  When the fuel is injected into the combustion chamber 24, the fuel self-ignites due to the compression of the combustion chamber 24, and energy is generated. This energy is taken out as rotational energy of the output shaft (crankshaft 30) of the diesel engine 10 via the piston 22. Connected to the crankshaft 30 is a flywheel 32 for suppressing rotational fluctuations of the crankshaft 30. The flywheel 32 may be a dual mass flywheel, for example. Further, a crank angle sensor 34 that detects the rotation angle of the crankshaft 30 is provided in the vicinity of the crankshaft 30. Further, cooling water flows through the cylinder block 20 in order to suppress the temperature rise of the diesel engine 10 due to the combustion of the fuel. The cylinder block 20 is provided with a water temperature sensor 36 for detecting the temperature of the cooling water.

  After the fuel is injected into the combustion chamber 24 through the fuel injection valve 28 and combustion occurs, the gas used for the combustion is discharged into the exhaust passage 40 as exhaust gas by the opening operation of the exhaust valve 38.

  The intake valve 18 and the exhaust valve 38 are both driven to open and close by the rotational force of the crankshaft 30. That is, as the crankshaft 30 rotates, the intake cam 42 and the exhaust cam 44 rotate, whereby the intake valve 18 and the exhaust valve 38 are driven to open and close. In the present embodiment, since the diesel engine 10 is assumed to be a four-stroke engine, the rotation cycle of the intake cam 42 and the exhaust cam 44 is twice the rotation cycle of the crankshaft 30.

  The exhaust passage 40 and the intake passage 12 are provided with an exhaust recirculation passage (EGR passage 50) for returning the exhaust gas in the exhaust passage 40 to the intake passage 12. Further, the EGR passage 50 is provided with an EGR valve 52 for adjusting the flow passage area.

  The electronic control unit (ECU 70) determines the fuel injection valve 28 and the like based on the detection values of the various sensors that detect the operating state of the diesel engine 10, the detection value of the accelerator sensor 58 that detects the operation amount of the accelerator pedal, and the like. The rotation of the diesel engine 10 is controlled by operating various actuators. The electric power of the battery 80 is supplied to the ECU 70 via the ignition switch 72, the main relay 74, and the power supply line L1.

  Here, the main relay 74 short-circuits the battery 80 and the power supply line L1 when the ignition switch 72 is turned on or a drive signal is input from the signal line L2. For this reason, when the ignition switch 72 is turned on, the battery 80 and the power supply line L1 are brought into conduction by the main relay 74, so that the electric power of the battery 80 is supplied to the ECU 70.

  On the other hand, when the electric power is supplied from the battery 80, the ECU 70 monitors the on / off state of the ignition switch 72 via the signal line L3. When the ignition switch 72 is turned off, a drive signal is output to the main relay 74 via the signal line L2 in order to continue power supply to the ECU 70 until completion of post-processing performed before the ECU 70 is stopped. . Thus, even after the ignition switch 72 is turned off, the electric power of the battery 80 is supplied to the ECU 70 via the main relay 74 and the power supply line L1 until the post-processing is completed in the ECU 70.

  Next, various auxiliary machines mounted on the diesel engine 10 will be described. Examples of the auxiliary machine (drive system auxiliary machine) driven by the crankshaft 30 include a generator (alternator 61), a fuel pump 62, and a refrigerant compressor 63.

  The alternator 61 includes a stator (not shown) having a stator coil 61a, a rotor (not shown) that is rotated by the driving force of the crankshaft 30, and a rotor coil 61b that excites the rotor. When an excitation current is passed through the rotor coil 61b to excite the rotor, an induced electromotive force is generated in the stator coil 61a as the rotor rotates, and the generated power is supplied to the battery 80 and charged.

  The ECU 70 controls the amount of power generated by the alternator 61 by controlling the exciting current that flows through the rotor coil 61b in accordance with the voltage B of the induced electromotive force generated in the stator coil 61a. During normal operation of the diesel engine 10, the excitation current flowing through the rotor coil 61b is turned off when the value of the voltage B exceeds a preset adjustment voltage, and the excitation current is turned on when it does not exceed the preset adjustment voltage. . The supply voltage B to the battery 80 is controlled to be an adjustment voltage by repeating this on / off.

  The fuel pump 62 is driven by the driving force of the crankshaft 30 to repeatedly suck and discharge fuel. As a result, high-pressure fuel corresponding to the injection pressure of the fuel injection valve 28 is continuously pumped to the common rail 26.

  Further, the fuel pumping pump 62 is provided with an electromagnetically driven suction metering valve 62a (SCV) at its fuel suction portion, and the low pressure fuel pumped up from the fuel tank 62c by the feed pump 62b is sucked in by the metering valve. The air is sucked into a fuel chamber (not shown) of the pump 62 through 62a. When the intake metering valve 62a is opened, the low pressure fuel is sucked into the fuel chamber from the feed pump 62b, and the sucked low pressure fuel is increased in pressure and discharged to the common rail 26. On the other hand, when the intake metering valve 62a is closed, the low pressure fuel is not supplied to the fuel chamber, and as a result, the supply of the high pressure fuel to the common rail 26 is stopped.

  The detected value of the fuel pressure (rail pressure) in the common rail 26 by the common rail pressure sensor 26a is input to the ECU 70. Then, during normal operation of the diesel engine 10, the ECU 70 calculates a target value of the common rail pressure (injection pressure) based on the engine speed and the fuel injection amount at that time, so that the actual rail pressure becomes the target rail pressure. In addition, the amount of high pressure fuel discharged by the fuel pump 62 is feedback controlled. Specifically, the target discharge amount by the fuel pump 62 is determined based on the deviation between the actual rail pressure and the target rail pressure, and the opening of the intake metering valve 62a is controlled accordingly, whereby the high pressure fuel is controlled. Control the discharge flow rate.

  The refrigerant compressor 63 is a component of an air conditioner that air-conditions the interior of the vehicle, compresses and discharges the refrigerant that is driven by the driving force of the crankshaft 30 and flows through the refrigerant passage. The refrigerant compressor 63 is connected to the crankshaft 30 via an electromagnetic clutch 63a. The ECU 70 controls the refrigerant discharge flow rate by the refrigerant compressor 63 by controlling the intermittent operation of the electromagnetic clutch 63a. Incidentally, an air conditioning ECU (not shown) determines a target value of the temperature of air that has passed through the evaporator (target post-evaporation temperature) based on the indoor set temperature, the outside air temperature, the amount of solar radiation, and the like set by the occupant. During the normal operation of the diesel engine 10, the intermittent operation of the electromagnetic clutch 63a is controlled according to the target post-evaporation temperature.

  Next, the supercharger 64 which is one of the auxiliary machines mounted on the diesel engine 10 will be described with reference to FIG.

  The supercharger 64 pressurizes intake air using an exhaust pressure as a drive source, and includes a turbine 64a, a compressor 64b, and a rotating shaft 64c. The turbine 64 a is disposed in the exhaust passage 40 and rotates due to the exhaust pressure in the exhaust passage 40. The compressor 64b is disposed in the intake passage 12, and is connected to the turbine 64a by a rotating shaft 64c. When the turbine 64a rotates, the compressor 64b rotates together with the rotating shaft 64c, and the intake air in the intake passage 12 is pressurized by the compressor 64b to perform supercharging.

  Further, in the exhaust passage 40, the upstream portion and the downstream portion of the turbine 64a communicate with each other by a bypass passage 40a, and a waste gate valve 40b is provided in the bypass passage 40a. The ECU 70 controls the operation of the waste gate valve 40b, and prevents the excessive supercharging pressure from being generated by opening the waste gate valve 40b during normal operation of the diesel engine 10.

  Incidentally, the ECU 70 calculates an EGR rate that is a ratio between the EGR amount and the fresh air based on the accelerator opening and the engine rotation speed, and calculates the target throttle opening based on the EGR rate. In addition, during normal operation of the diesel engine 10, the ECU 70 calculates a target overpressure from the target torque. Then, the opening degree of the wastegate valve 40b is feedback-controlled so that the actual excessive pressure detected by the excessive pressure sensor 12a matches the target excessive pressure.

  By the way, when the ignition switch 72 is turned off, the ECU 70 determines that a stop command for the diesel engine 10 has been issued, and performs stop control for stopping the diesel engine 10.

  Next, the stop control processing procedure of the diesel engine 10 according to the present embodiment will be described with reference to FIG. This stop process is repeatedly executed by the ECU 70, for example, at a predetermined cycle.

  In this series of processing, first, in step S10, it is determined whether or not the ignition switch 72 is turned off. This process determines whether or not a stop command for the diesel engine 10 has been issued. When it is determined that the ignition switch 72 has been turned off, the routine proceeds to step S11, where it is determined whether or not the rotational speed of the diesel engine 10 is substantially zero.

  If it is determined that the rotational speed is substantially zero (S11: YES), the stop control is not necessary, and thus the series of processes shown in FIG. When it is determined that the rotation speed is not substantially zero (S11: NO), the process proceeds to step S12.

  In step S12, it is determined whether or not the rotational speed of the diesel engine 10 based on the value detected by the crank angle sensor 34 is equal to or lower than a specified rotational speed α (for example, 300 rpm). In (S12: NO), stop control of the diesel engine 10 is performed by open control in step S14.

  Next, details of the processing in step S14 will be described below.

  First, the fuel injection valve 28 as a combustion system auxiliary device is controlled to be closed to perform fuel injection cut to stop fuel injection, and the throttle valve 14 as a combustion system auxiliary device is fully closed to suppress intake air. . According to these controls, the degree of combustion is suppressed to the maximum, and the decrease speed of the rotation speed of the crankshaft 30 is increased.

  In step S14, the drive torque (output shaft load) applied to the crankshaft 30 is maximized by maximizing the drive of the alternator 61, the fuel pressure pump 62, and the refrigerant compressor 63 as drive system auxiliary machines. The reduction speed of the rotational speed of the shaft 30 is increased.

  Specifically, with respect to the alternator 61, the amount of power generation is maximized by maximizing the excitation current flowing through the rotor coil 61b. According to this, the drive torque of the rotor of the alternator 61 is maximized, and the reduction speed of the rotation speed of the crankshaft 30 is increased.

  Further, the target rail pressure is set to the maximum (for example, 180 MPa) for the fuel pressure pump 62. According to this, the supply flow rate of the high-pressure fuel to the common rail 26 is maximized, and the drive torque of the fuel pump 62 is maximized, so that the rotational speed of the crankshaft 30 is decreased. In this case, the fuel injection valve 28 is operated (empty driving operation) so as to return the surplus fuel to the fuel tank 62c while stopping the fuel injection.

  Further, the target post-evaporation temperature is set to the minimum for the refrigerant compressor 63. According to this, since the refrigerant discharge flow rate of the refrigerant compressor 63 is maximized and the drive torque of the refrigerant compressor 63 is maximized, the rotational speed of the crankshaft 30 can be decreased.

  Further, in step S14, by reducing the amount of exhaust that bypasses the supercharger 64 as an exhaust system auxiliary machine, the piping resistance until the exhaust flows through the exhaust passage 40 and is discharged to the outside increases. . Then, when the piston 22 pushes out and discharges the combustion gas in the combustion chamber 24, its discharge resistance (exhaust load) increases. Therefore, the decrease speed of the rotation speed of the crankshaft 30 can be increased.

  Specifically, the wastegate valve 40b is controlled to be fully closed by setting the target over-absorption pressure to the maximum. Then, the flow rate of the exhaust gas discharged from the combustion chamber 24 and flowing into the turbine 64a is maximized, and the exhaust load is maximized. Therefore, the decrease speed of the rotation speed of the crankshaft 30 can be increased.

  Next, details of the processing in steps S16, S18, and S20 will be described below.

  If it is determined in step S12 that the rotation speed of the crankshaft 30 is equal to or less than the specified rotation speed α (S12: YES), stop control of the diesel engine 10 is performed by feedback control in steps S16, S18, and S20.

  That is, first, in step S16, a target decrease speed ΔNEt corresponding to each rotation speed based on the detection value of the crank angle sensor 34 is calculated. Specifically, the target decrease rate ΔNEt is defined by the amount of decrease in rotational speed per unit time. Specific examples of the unit time include a predetermined cycle in which the process shown in FIG. 3 is executed and a preset interrupt cycle.

  Further, it is desirable that the rotation speed be a rotation speed that averages rotation fluctuations accompanying a change in stroke.

  In the subsequent step S18, an actual decrease rate ΔNE is calculated. Here, a reduction speed is calculated for an average rotational speed obtained by averaging rotational fluctuations associated with stroke changes. For example, the decrease speed is calculated by calculating an average rotational speed in an angle region that is an integral multiple of an angle corresponding to one combustion cycle (“720 ° C. A” for a 4-stroke engine) divided by the number of cylinders. It can be calculated as a difference in rotational speed between areas to be performed.

  In the subsequent step S20, the throttle opening θ and the injection amount are set based on the target decrease speed ΔNEt and the actual decrease speed ΔNE. The map shown in FIG. 4 is used for this setting. This map determines the injection amount and the throttle opening θt from the difference between the actual decrease speed ΔNE and the target decrease speed ΔNEt and the rotational speed.

  The target decrease speed ΔNEt defined in the map is set to a larger value as the rotational speed is larger, and is set to a smaller value as the rotational speed is smaller. Here, not only the difference of the actual decrease speed ΔNE to the target decrease speed ΔNEt but also the rotation speed is used as the throttle opening θt and the injection amount when the rotation speed is different even if the difference is the same. Because different values can be different. For example, when the rotational speed becomes low to some extent, it is not appropriate to increase the injection amount, and it is desirable to control the decrease speed of the rotational speed only by the throttle valve 14.

  In the subsequent step S22, the output shaft load by the alternator 61, the fuel pump 62 and the refrigerant compressor 63 as the drive system auxiliary machine is minimized, and the exhaust load by the supercharger 64 as the exhaust system auxiliary machine is minimized. .

  Specifically, in step S22, with respect to the alternator 61, the exciting current to the rotor coil 61b is stopped to reduce the power generation amount to zero. Regarding the fuel pump 62, the target rail pressure is set to a minimum value (for example, 25 MPa) at which fuel can be injected from the fuel injection valve 28. For the refrigerant compressor 63, the electromagnetic clutch 63a is controlled to be disconnected. Further, the supercharger 64 is controlled so that the wastegate valve 40b is fully opened.

  That is, the feedback control in steps S16, S18, and S20 does not depend on the adjustment of the output shaft load and the exhaust load, and the rotation speed is adjusted by adjusting the degree of combustion by the fuel injection valve 28 and the throttle valve 14 as combustion system auxiliary machines. The rate of decline is adjusted.

  Since the throttle valve 14 is of a normally open type, when energization is stopped by ending this series of processing, the throttle valve 14 is fully opened. For this reason, it is desirable to set the rotation speed to be surely stopped by continuing energization for a predetermined time after it is first determined that the rotation speed has become substantially zero in step S11.

  FIG. 5 illustrates an example of the stop control. 5A shows the state of the ignition switch 72, FIG. 5B shows the vibration of the crankshaft 30, and FIG. 5C shows the rotational speed of the crankshaft 30. FIG. 5 (d) shows the opening of the wastegate valve 40b, FIG. 5 (e) shows the rail pressure, FIG. 5 (f) shows the fuel discharge flow rate by the fuel pump 62, and FIG. g) shows the power generation amount by the alternator 61, FIG. 5 (h) shows the refrigerant discharge flow rate by the refrigerant compressor 63, FIG. 5 (i) shows the fuel injection amount by the fuel injection valve 28, and FIG. ) Indicates the throttle opening.

  As shown in the figure, according to the present embodiment, when the diesel engine 10 is in a normal operation and the rotational speed of the crankshaft 30 is an idle rotational speed (700 rpm), the ignition switch 72 is turned off by the driver. Then, the wastegate valve 40b is fully closed. Therefore, the exhaust load is maximized. Further, when the ignition switch 72 is turned off, the rail pressure is set to the maximum value (180 MPa), the discharge flow rate of the fuel pump 62 is maximized, the power generation amount by the alternator 61 is maximized, and the refrigerant by the refrigerant compressor 63 is The discharge flow rate is maximum. Therefore, the output shaft load is maximized. When the ignition switch 72 is turned off, the fuel injection amount becomes zero by the fully closed operation of the fuel injection valve 28, and the throttle valve 14 is fully closed. Therefore, the degree of combustion is minimized.

  As described above, along with the maximum exhaust load, the maximum output shaft load, and the minimum degree of combustion, the rotational speed (700 rpm) of the crankshaft 30 when the ignition switch 72 is turned off is the resonance frequency band of the flywheel 32. It decreases at the maximum reduction rate until it passes (NE1 to NE2) (until it reaches 300 rpm). Of the rotation speed bands, the band from the rotation speed at the time of the off operation to the lower limit value NE1 of the resonance frequency band is referred to as a second stop immediately preceding band A2.

  Thereafter, when the rotational speed of the crankshaft 30 passes through the resonance frequency band, the wastegate valve 40b is fully opened, and the exhaust load is minimized. Further, when passing through the resonance frequency band, the rail pressure is set to the minimum value at which fuel can be injected from the fuel injection valve 28, so that the discharge flow rate of the fuel pump 62 becomes zero, and the generator 61 generates power. The amount becomes zero, and the refrigerant discharge flow rate by the refrigerant compressor 63 becomes zero. Therefore, the output shaft load is minimized.

  Further, when the resonance frequency band is passed, the fuel is injected again by the fuel injection valve 28, and then the fuel injection amount gradually decreases to zero. Further, when passing through the resonance frequency band, the throttle valve 14 is opened again, and thereafter, the opening degree is gradually reduced to zero. In the example shown in FIG. 5 (i), the fuel injection amount is set to zero before the rotation speed becomes zero, but the injection may be continued until the rotation speed becomes zero. In the example shown in FIG. 5 (j), the throttle valve 14 is opened until the rotational speed becomes zero, but may be fully closed before the rotational speed becomes zero.

  As described above, with the minimum exhaust load and the minimum output shaft load, the rotational speed of the crankshaft 30 decreases after passing through the resonance frequency band of the flywheel 32. Of the rotation speed bands, a band that is smaller than the second stop immediately preceding band A2 and includes a point at which the rotation speed is zero is referred to as a first stop immediately preceding band A1.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) Among the rotational speeds at the time of stop control, in the first zone immediately before stop A1 including the point that becomes zero, the speed of decrease in the rotational speed is reduced compared to the second zone immediately before stop A2 before that. 2) The diesel engine 10 is stopped in a state in which the speed of decrease in the rotational speed is made slower than when the speed is stopped at the speed of decrease in the zone A2 immediately before the stop. Therefore, the rotational fluctuation of the crankshaft 30 that occurs when the engine is suddenly stopped can be reduced, and the rotation of the diesel engine 10 can be smoothly stopped.

  (2) In the second stop immediately preceding band A2 including the resonance frequency bands NE1 to NE2, the decrease speed is larger than that in the first stop immediately preceding band A1, so that the fluctuation in the rotational speed of the diesel engine 10 is particularly remarkable. The bands NE1 and NE2 can be passed quickly. Therefore, the time spent in the resonance frequency band NE1 to NE2 can be shortened, and consequently the rotational fluctuation of the crankshaft 30 can be reduced.

  In particular, in the zone A2 immediately before the second stop, the output shaft load by the alternator 61, the fuel pump 62 and the refrigerant compressor 63 as the drive system auxiliary machine is maximized, and the exhaust by the supercharger 64 as the exhaust system auxiliary machine. The load is maximized. Therefore, it is possible to increase the rate of decrease compared to the case where the rate of decrease of the rotational speed is increased only by suppressing the degree of combustion. Therefore, the time spent in the resonance frequency bands NE1 to NE2 existing in the band A2 immediately before the second stop can be shortened, and the rotational fluctuation of the crankshaft 30 occurring in the resonance frequency bands NE1 to NE2 can be reduced.

  (3) Here, of the stop control in which the decrease rate of the rotation speed is increased in the second stop immediately preceding band A2 and decreased in the first stop immediately preceding band A1, the control in the first stop immediately preceding band A1 is abruptly performed. In order to reduce the rotational fluctuation that occurs when the motor is stopped, it is required to perform control with particularly high accuracy. In view of this point, according to the embodiment, in the first stop zone A1, the ECU 70 sets a target value for the rotational speed of the crankshaft 30 so that the calculated actual rotational speed becomes the target value. Perform feedback control. Therefore, the rate of decrease in the zone A1 immediately before the first stop can be controlled with high accuracy, and the reduction in rotational fluctuation that occurs during a sudden stop can be accurately suppressed.

  (4) Regarding the stop control in the zone A1 immediately before the first stop, the throttle opening and the injection amount are set based on the difference between the target decrease speed ΔNEt and the actual decrease speed ΔNE and the rotational speed. Thereby, rotation stop control can be performed more appropriately.

  (5) After the ignition switch 72 is turned off, the stop control of the diesel engine 10 is performed by the open control in the second stop immediately preceding zone A2 in which the rotation speed is higher than the specified rotation speed α. Therefore, the diesel engine 10 can be quickly stopped with a simple setting in the second zone A2 immediately before the stop, which does not need to be controlled with high accuracy compared to the zone A1 immediately before the first stop.

  (6) The rate of decrease in the zone A1 immediately before the first stop is controlled by the degree of combustion by the fuel injection valve 28 and the throttle valve 14. Thereby, when the request | requirement which applies a positive torque to the crankshaft 30 arises, it can respond appropriately to this.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and the characteristic structures of the above embodiments may be arbitrarily combined. For example, you may implement as follows.

  When executing the stop control, it is preferable to prohibit the throttle valve 14 from being fully closed when the temperature of the diesel engine 10 is equal to or lower than the specified temperature β. According to this, it is possible to reliably avoid the occurrence of an abnormality in which the throttle valve 14 is stuck in the fully closed state during the stop control.

  In the above embodiment, when the fuel pump 62 is operated during stop control, the fuel injection valve 28 is idled. However, a return pipe is provided in the common rail 26, and surplus fuel is supplied to the fuel tank 62c by the return pipe. You may make it return. In this case, a pressure regulator may be provided in the return pipe so that excess fuel is returned through the return pipe when the rail pressure of the common rail 26 exceeds a predetermined value. Incidentally, the pressure regulator may be a mechanical type that mechanically determines the predetermined value, or may be an electric type that can electrically set the predetermined value.

  In the above embodiment, the rotational speed reduction speed in the zone A1 immediately before the first stop is controlled only by the degree of combustion by the fuel injection valve 28 and the throttle valve 14, but by the drive system auxiliary devices 61, 62, 63 The decrease rate may be controlled by at least one of the output shaft load, the exhaust load by the exhaust system auxiliary machine 64, and the degree of combustion.

  In the above embodiment, open control is applied to the control of the decrease rate in the band A2 immediately before the second stop, but feedback control may be applied. In addition, open control may be applied instead of feedback control for the control of the decrease rate in the band A1 immediately before the first stop.

  -In the said embodiment, although the exhaust load by the supercharger 64 is adjusted with the opening degree of the wastegate valve 40b, when the supercharger 64 of the type whose discharge capacity of the turbine 64a is variable is employ | adopted. The exhaust load may be adjusted by controlling the discharge capacity. Specifically, the discharge capacity may be increased to increase the exhaust load, and the discharge capacity may be decreased to decrease the exhaust load. Incidentally, as the supercharger 64 having a variable discharge capacity, a type in which the discharge capacity is adjusted by adjusting the suction port area of the turbine 64a, a type in which the discharge capacity is adjusted by adjusting the vane angle of the turbine 64a, etc. Is mentioned.

  As an exhaust system auxiliary machine that can adjust the exhaust load, in addition to the supercharger 64 described above, an exhaust valve that adjusts the opening degree of the exhaust passage 40 can be cited. If the opening of the exhaust valve is reduced, an exhaust load can be obtained by the action of the exhaust brake.

  As a drive system auxiliary machine capable of adjusting the output shaft load, in addition to the alternator 61, the fuel pressure pump 62 and the refrigerant compressor 63 described above, a water pump for circulating engine cooling water and a lubricating oil for circulating lubricating oil Examples thereof include an oil pump for generating hydraulic pressure as a hydraulic pressure generating means for operating a pump and a hydraulic actuator.

  In the above embodiment, during the stop control, the degree of combustion is reduced by reducing the opening of the throttle valve 14, but if the opening of the throttle valve 14 is reduced, the pumping loss increases. The intake resistance (intake load) when the piston 22 descends increases. Therefore, the decrease speed of the rotation speed of the crankshaft 30 can be increased. As a means for increasing the intake load, in addition to the throttle valve 14, for example, a valve timing variable device that makes the relative rotational phase difference of the intake cam 42 with respect to the crankshaft 30 variable, etc. There is a valve characteristic variable device that makes the variable. Also by this, the flow rate of the gas flowing into the combustion chamber 24 can be adjusted, and consequently the negative torque applied to the crankshaft 30 can be adjusted.

  Further, when the intake valve 18 and the exhaust valve 38 are not driven by the intake cam 42 or the exhaust cam 44, such as electromagnetically driven valves, the open / close state is freely determined regardless of the rotation angle of the crankshaft 30. can do. Therefore, the intake load and the exhaust load may be adjusted by operating the intake valve 18 and the exhaust valve 38, and thereby stop control may be performed.

  In the above embodiment, the stop control is performed by dividing the rotation speed band after the ignition switch 72 is turned off into two bands, the first band A1 immediately before the first stop and the second band A2 immediately before the second stop. You may make it control. For example, the stop control is performed by dividing the band A2 immediately before the second stop into the resonance frequency bands NE1 to NE2 and the band before the resonance frequency band NE1 to NE2, and in the band before the resonance frequency band NE1 to NE2, the rate of decrease is lower than the resonance frequency band NE1 to NE2. You may control to make it small.

  As a method for setting the target decrease rate ΔNEt, for example, the same value may be set up to the lower end speed NE1 of the resonance frequency band (NE1 to NE2), and thereafter, the target decrease rate ΔNEt may be reduced. Note that the target decrease rate ΔNEt may be changed stepwise or continuously.

  The stop command for the diesel engine 10 is not limited to the one in which the ignition switch 72 is turned off. For example, if the vehicle has a so-called idle stop function that automatically stops the diesel engine 10 temporarily when the vehicle is stopped, the temporary automatic stop request may be determined to be a stop command.

  The internal combustion engine is not limited to a compression ignition type internal combustion engine such as the diesel engine 10, but may be a spark ignition type internal combustion engine such as a gasoline engine.

The figure which shows the whole structure of the engine system concerning this embodiment. The figure which shows the structure of the supercharger concerning the embodiment. The flowchart which shows the process sequence of stop control of the diesel engine concerning the embodiment. The figure which shows the setting method of the injection quantity and throttle opening for stop control concerning the embodiment. The time chart which illustrates the aspect of the stop control concerning the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Diesel engine (internal combustion engine), 14 ... Throttle valve (combustion system auxiliary machine), 28 ... Fuel injection valve (combustion system auxiliary machine), 30 ... Crankshaft (output shaft), 61 ... Alternator (drive system auxiliary machine) , 62 ... Fuel pump (drive system auxiliary machine), 63 ... Refrigerant compressor (drive system auxiliary machine), 64 ... Supercharger (exhaust system auxiliary machine), 70 ... ECU (stop determination means, auxiliary machine control means) A1... Band immediately before the first stop, A2... Band immediately before the second stop.

Claims (13)

Stop determination means for determining the presence or absence of a stop command for the internal combustion engine;
Controlling the drive of a combustion system auxiliary device that controls the state of the air-fuel mixture supplied to the combustion chamber of the internal combustion engine to adjust the degree of combustion, and the exhaust system auxiliary device that controls the exhaust state of the internal combustion engine; and Accessory control means for controlling the drive of at least one of the drive system auxiliary machines driven by the output shaft;
With
The auxiliary machine control means includes
When the stop determination means determines that the stop command is present, in addition to adjusting the degree of combustion by controlling the combustion system auxiliary machine, the exhaust load by controlling the drive of the exhaust system auxiliary machine is controlled. Executing stop control for adjusting at least one of adjustment and adjustment of the output shaft load by controlling the drive of the drive system auxiliary machine,
Reducing a reduction speed of the rotation speed of the output shaft in a predetermined zone immediately before the first stop including a point at which the rotation speed of the output shaft of the internal combustion engine becomes zero as compared with a zone immediately before the second stop before that. An internal combustion engine stop control device.   In addition to suppressing the degree of combustion in the zone immediately before the second stop, the auxiliary machine control means determines the degree of load of at least one of the exhaust load and the output shaft load immediately before executing the stop control. The stop control device for an internal combustion engine according to claim 1, wherein the stop control is executed so as to be larger than the degree. The exhaust system auxiliary machine includes a turbine that is disposed in an exhaust passage and rotates by exhaust pressure, and a turbocharger that is disposed in an intake passage and rotates integrally with the turbine to pressurize intake air. Is included at least,
The auxiliary machine control means controls the degree of the exhaust load by controlling a flow rate of exhaust gas flowing into the turbine from a combustion chamber of the internal combustion engine when executing the stop control. 3. A stop control device for an internal combustion engine according to 1 or 2. The drive system auxiliary machine includes at least a generator that generates electric power by the rotational force of the output shaft,
The said auxiliary machine control means controls the degree of the said output shaft load by controlling the electric power generation amount by the said generator, in performing the said stop control. The internal combustion engine stop control apparatus. The drive system auxiliary machine includes at least a fuel pump that discharges the fuel at a high pressure,
The auxiliary machine control means controls the degree of the output shaft load by controlling a fuel discharge flow rate by the fuel pump in performing the stop control. The stop control device for an internal combustion engine according to claim 1. The drive system auxiliary machine includes at least a refrigerant compressor that compresses and discharges the refrigerant flowing through the refrigerant passage of the air conditioner,
The said auxiliary machine control means controls the degree of the said output shaft load by controlling the refrigerant | coolant discharge flow rate by the said refrigerant compressor in performing the said stop control. The stop control device for an internal combustion engine according to claim 1. The combustion system auxiliary machine includes at least a fuel injection valve for supplying fuel to the internal combustion engine,
The said auxiliary machine control means controls the said combustion degree by controlling the fuel injection amount by the said fuel injection valve, in performing the said stop control. An internal combustion engine stop control device. The combustion system auxiliary machine includes at least a throttle valve for adjusting an intake flow rate supplied to a combustion chamber of the internal combustion engine,
The internal combustion engine according to any one of claims 1 to 7, wherein the auxiliary machine control means controls the degree of combustion by controlling an intake flow rate by the throttle valve when executing the stop control. Stop control device. A rotational speed calculating means for calculating an actual rotational speed of the output shaft;
Target value setting means for setting a target value for the rotation speed of the output shaft after the stop determination means determines that the stop command is present;
With
The auxiliary machine control means performs feedback control so that the actual rotation speed calculated by the rotation speed calculation means becomes the target value after it is determined that the stop command is present. Item 9. The stop control device for an internal combustion engine according to any one of Items 1 to 8.   10. The stop control device for an internal combustion engine according to claim 9, wherein the auxiliary machine control means performs the feedback control at least in the zone immediately before the first stop. A flywheel that reduces rotational fluctuation of the output shaft is attached to the output shaft,
The stop control device for an internal combustion engine according to any one of claims 1 to 10, wherein the zone immediately before the second stop includes a rotation speed band corresponding to a resonance frequency band of the flywheel.   The stop control device for an internal combustion engine according to any one of claims 1 to 11, wherein the internal combustion engine is a compression ignition internal combustion engine. A stop control device for an internal combustion engine according to any one of claims 1 to 12,
The combustion system auxiliary machine;
At least one of the exhaust system auxiliary machine and the drive system auxiliary machine;
A stop control system for an internal combustion engine, comprising:

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