JP5081117B2 - Control device for turbocharged engine - Google Patents

Description

  According to the present invention, when the shutter means is provided in the intake pipe and the engine is stopped when the idle stop condition is satisfied, the intake pipe is closed by the shutter means so as to hold the pressurized air in the intake pipe. The present invention relates to a control device for a supercharged engine.

  Conventionally, for the purpose of improving fuel economy and reducing CO2 emissions, the engine is automatically activated when the accelerator pedal is in an open state, such as waiting for a signal, and when the vehicle is stopped with the brake pedal depressed. There is known so-called idle stop control for temporarily stopping. In this type of idle stop control, the engine is automatically restarted when a start preparation operation is performed to start the vehicle at the driver's intention, such as releasing the pedaling force on the brake pedal during the idle stop control. Start and prepare for departure.

  In the restart from the idle stop, when the driver's intention to start the vehicle is detected, the quickness to start immediately is required. However, in a general starting method in which the engine is restarted after cranking by a starter motor, fresh air is sucked into the cylinders in the intake stroke during cranking through the intake valve. There is a problem that pumping loss occurs due to the intake resistance when passing through the intake valve, and it takes a considerable amount of time to complete the start, and the load on the starter motor increases accordingly, and the durability decreases. .

  As a countermeasure, for example, in an engine equipped with electric supercharging means as disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-263026), even when the engine is stopped, the electric supercharging means Therefore, the intake air supplied to each cylinder can be pressurized by operating the electric supercharging means during idle stop.

As a result, when cranking during restart from idle stop, pressurized fresh air can be supplied to the cylinders in the intake stroke, so intake resistance is low, pumping loss is reduced, and cranking is reduced. The time from the start of ranking to the completion of starting (cranking time) is shortened, and not only good restartability can be obtained, but also the burden on the starter motor can be reduced.
JP 2007-263026 A

  However, constantly driving the electric supercharging means during idle stop causes a problem that the power consumption of the battery is increased and fuel consumption is deteriorated.

  On the other hand, if the electric supercharging means is driven almost simultaneously with the start of cranking, the cranking time can be shortened to some extent due to the increase of the supercharging pressure, but the pressure of fresh air supplied to each cylinder increases. Since there is a time lag, it is necessary to take measures such as increasing the capacity of the electric supercharging means in order to obtain quick restartability.

  In view of the above circumstances, the present invention eliminates the need to drive the electric supercharging means at the time of idling stop and constantly supercharge, and can shorten the cranking time at the time of restart and obtain good restartability. An object of the present invention is to provide a control device for an engine with a supercharger that can reduce the power consumption of the battery and can improve fuel consumption.

In order to achieve the above object, a supercharger-equipped engine control apparatus according to the present invention includes an electric supercharger interposed in an intake pipe, and an intake pipe that leads from the electric supercharger to an intake valve. When a shutter means that can open and close the intake pipe and a preset idle stop condition are satisfied, the engine is stopped, the supercharging operation of the electric supercharging means is stopped, and the intake passage is opened by the shutter means. and control means for closed, the shutter means being provided in the throttle valve upstream of the intake pipe leading to the intake valve from the electric supercharger means.

  According to the present invention, when the idle stop condition is satisfied and the engine is stopped, the electric supercharging means is stopped and the air passage is closed by the shutter means. The air pressurized by the electric supercharging means immediately before the idle stop can be held. As a result, it is not necessary to always maintain the supercharging pressure by driving the electric supercharging means, the power consumption of the battery during the idling stop can be reduced, and the fuel consumption can be improved.

  Moreover, in the restart after the idle stop, since the pressurized air is supplied into the cylinder, the charging efficiency is improved, the pumping loss is reduced, and the cranking time at the restart is shortened, which is good. Restartability can be obtained. Further, the shortening of the cranking time reduces the burden on the starter motor and improves the durability. Further, the power consumption of the battery is further reduced, and the fuel efficiency can be relatively improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an overall configuration diagram of a supercharged engine.

  Reference numeral 1 in the figure is an engine, and in the present embodiment, a horizontally opposed engine is illustrated. Cylinder heads 2 are provided in the left and right banks of the engine 1, and intake ports 3 and exhaust ports 5 are formed in the cylinder heads 2 corresponding to the cylinders formed in the banks. The intake port 3 of each cylinder head 2 is gathered in the air chamber 6 via the intake manifold 4 on the upstream side. Further, a throttle passage 7 is connected to the upstream side of the air chamber 6, and an air cleaner 10 is attached to the upstream side of the throttle passage 7 via an intake pipe 9.

  Further, the downstream side of the exhaust port 5 of each cylinder head 2 is gathered via the exhaust manifold 11 and communicated with the exhaust pipe 12. A catalyst 13 is interposed in the middle of the exhaust pipe 12, and a muffler 14 is communicated downstream of the exhaust pipe 12.

  On the other hand, a throttle valve 8 is provided in the throttle passage 7, and an intercooler 15 is interposed in the intake pipe 9 immediately upstream of the throttle passage 7. The throttle valve 8 employed in this embodiment is a component of an electronically controlled throttle device that is opened and closed by a throttle actuator 8a. The throttle valve 8 is mechanically linked to an accelerator pedal. It may be.

  Further, an electric supercharger 21 is disposed between the intercooler 15 of the intake pipe 9 and the air cleaner 10. The electric supercharger 21 has a casing 22 interposed in the intake pipe 9 and an electric compressor 23 as electric supercharging means. Further, the electric compressor 23 has a compressor impeller 23a facing the casing 22, and an electric motor 23b for rotating the compressor impeller 23a.

  The electric supercharger 21 rotates the electric compressor 23 to pressurize the intake air. Since the electric compressor 23 does not use exhaust energy as a drive source, it can be supercharged even when the engine is stopped, as well as low rotation after starting, and the intake pipe pressure downstream of the compressor impeller 23a can be maintained at a positive pressure. it can.

  Further, an electric shutter 25 as shutter means is disposed between the compressor impeller 23 a of the intake pipe 9 and the intercooler 15. The electric shutter 25 includes an intake shutter valve 25a such as a butterfly valve that is disposed in the intake pipe 9 and opens and closes the intake pipe 9, and a shutter actuator 25b that opens and closes the intake shutter valve 25a. Yes. The shutter actuator 25b includes a stepping motor, a rotary solenoid, and the like, and fully opens or closes the intake pipe 9.

  When the intake shutter valve 25a is fully closed, the periphery of the intake shutter valve 25a is in close contact with the inner wall of the intake pipe 9 and sealed. When the intake shutter valve 25a is fully opened, the intake shutter valve 25a is rotated in the direction along the flow of intake air (the horizontal direction in FIG. 1). FIG. 1 shows the intake shutter valve 25a in a fully closed state.

  Further, an injector 31 is provided on the upstream side of the intake port 3 of each cylinder of the intake manifold 4, and a spark plug 32 is attached to a portion corresponding to each cylinder of the cylinder head 2 so that its ignition part faces the cylinder. It has been.

  An air intake pipe pressure sensor 33 for detecting the air intake pipe pressure as an absolute pressure is exposed to the air chamber 6. Further, a crank rotor 34 is mounted on the crank shaft 1 b of the engine 1, and an engine speed sensor 35 is provided on the outer periphery of the crank rotor 34. Protrusions (or slits) are formed on the outer periphery of the crank rotor 34 at predetermined intervals, and the engine speed sensor 35 determines in advance the interval time when the passage of each protrusion (or slit) of the crank rotor 34 is detected. The engine speed Ne is detected on the basis of the set crank angle.

  In addition, a thermoelectric conversion element 36 is disposed upstream of the catalyst 13 in the exhaust pipe 12 and downstream of the collecting portion of the exhaust manifold 11. The thermoelectric conversion element 36 is composed of a plurality of Peltier elements, and is wound around the exhaust pipe 12. The thermoelectric conversion element 36 collects heat from the exhaust pipe 12 heated by the exhaust heat and generates electric power to generate electric power.

  Each intake port 3 formed in the cylinder head 2 is provided with an intake valve 37, and each exhaust port 5 is provided with an exhaust valve 38. Further, the cylinder head 2 is provided with an intake cam shaft 39 and an exhaust cam shaft 40 for opening and closing the intake valve 37 and the exhaust valve 38 at a predetermined timing. The crankshaft 1b (see FIG. 1) is rotated through a half rotation synchronously with one rotation of the crankshaft 1b (not shown).

  By the way, the intake valve 37 and the exhaust valve 38 have a valve overlap period in which both valves open from the latter half of the exhaust stroke to the first half of the intake stroke. Since it is closed, if the engine 1 is stopped during that period, the internal pressure does not leak to the exhaust pipe 12 side. Therefore, when the engine 1 is stopped at the crank angle at which at least one of the intake valve 37 and the exhaust valve 38 of all the cylinders is closed and the intake shutter valve 25a is fully closed at the time of idling stop, each cylinder is closed. The internal pressure can be maintained in the pipe length from the intake valve 37 or the exhaust valve 38 to the intake shutter valve 25a.

  As a result, even if the electric compressor 23 of the electric supercharger 21 is stopped at the time of idling stop, the internal pressure does not rapidly decrease and can be held for a long time, so that the electric compressor 23 can be stopped. By stopping the electric compressor 23, not only can noise be reduced during idle stop, but also the power consumption of the battery 43 can be reduced and the fuel efficiency can be relatively improved.

  The opening / closing control of the intake shutter valve 25a at the time of idling stop, the supercharging pressure control of the electric supercharger 21, the charging control of the thermoelectric conversion element 36, etc. are performed by an electronic control unit (ECU) 41 as control means shown in FIG. Done. The ECU 41 is mainly composed of a microcomputer, and has a well-known CPU, ROM, RAM, and the like, and performs calculations necessary for various controls according to programs stored in the ROM.

  An ignition switch 51, an engine speed sensor 35, and an intake pipe pressure sensor 33 are connected to the input side of the ECU 41. Further, a current sensor 43a provided in the battery 43 is connected. In the ECU 41, the charge / discharge current of the battery 43 detected by the current sensor 43a is integrated to calculate the remaining battery charge SOC (State of Charge).

  Then, based on the remaining battery SOC, it is checked whether or not the electric power generated by the thermoelectric conversion element 36 can be charged in the battery 43. If the battery 43 can be charged, it is charged via the charging unit 43b provided in the battery 43. Let On the other hand, when the battery 43 is in a fully charged state and cannot be charged, the power consumed by the thermoelectric conversion element 36 is consumed by the power consuming unit 44. The power consuming unit 44 uses existing equipment mounted on the vehicle, such as a cooling fan attached to the radiator. A vehicle equipped with a large-capacity capacitor may store the electric power generated by the thermoelectric conversion element 36 in this large-capacity capacitor instead of the power consumption unit 44.

  On the other hand, an electric motor 23b provided in the electric compressor 23, a shutter actuator 25b provided in the electric shutter 25, and a starter motor 46 are connected to the output side of the ECU 41 via a drive circuit 45. In addition, a discharge changeover switch 47 is connected to supply power generated by the thermoelectric conversion element 36 to either the battery 43 or the power consumption unit 44.

  Next, the opening / closing control of the intake shutter valve 25a, the supercharging pressure control of the electric supercharger 21, and the charging control of the thermoelectric conversion element 36 performed at the time of idling stop executed by the ECU 41 are performed according to the flowcharts shown in FIGS. explain.

  When the ignition switch 51 is turned on and the ECU 41 is activated and the system is initialized, first, an idle stop control routine shown in FIG. 3 is executed for each set calculation cycle. In step S1, it is checked whether the restart condition after the idle stop is satisfied.

  The restart condition is determined by whether or not the driver has performed a start preparation operation. As a start preparation operation performed by the driver, for example, when the vehicle is stopped (vehicle speed is 0 [Km / h]), when the depression force on the brake pedal is released and the depression of the accelerator pedal is detected, the restart condition is established Is determined. Accordingly, the restart condition is not satisfied because the brake pedal is depressed at the start. Similarly, the restart condition is not satisfied even during traveling because the vehicle speed is not 0 [Km / h].

  If it is determined that the restart condition is not satisfied, the process proceeds to step S2, and if it is determined that the restart condition is satisfied, the process branches to step S3.

  In step S2, it is checked whether an idle stop condition is satisfied. As the idle stop condition, the driver completely stops the vehicle by waiting for a signal or the like, and determines the state of waiting for re-start. As an idle stop condition, for example, the stop state (the vehicle speed is 0 [Km / h]) continues for a set time (for example, 3 [sec}), the brake pedal is depressed, and the battery 43 is When the voltage is equal to or higher than a predetermined voltage (for example, 10 [V]), it is determined that the idle stop condition is satisfied. And when it determines with idle stop conditions being satisfied, it progresses to step S4. If it is determined that the idle stop condition is not satisfied, that is, if both the restart condition and the idle stop condition are not satisfied, the process proceeds to step S5, the normal engine control is executed, and the process proceeds to step S10.

  In normal engine control, the shutter actuator 25b of the electric shutter 25 is driven to fully open the intake shutter valve 25a, and the target boost pressure by the electric compressor 23 of the electric supercharger 21 is set to the engine operating state (for example, engine rotation). The intake pipe pressure is controlled based on the difference between the intake pipe pressure detected by the intake pipe pressure sensor 33 and the target boost pressure. The electric compressor 23 is controlled so as to obtain a supply pressure.

  On the other hand, when it is determined in step S2 that the idle stop condition is satisfied and the process proceeds to step S4, the engine stop process is executed and the process proceeds to step S6. The engine stop process executed in step S4 is performed according to the engine stop process subroutine shown in FIG.

  In this routine, first, in step S21, the fuel injection amount immediately before stop is calculated. The engine speed during the idling operation is substantially constant, and it can be predicted from an experiment or the like at which crank angle the engine 1 is stopped by the combustion of the fuel injected just before the fuel cut. Therefore, by adjusting the fuel injection amount immediately before the stop, the engine 1 can be operated in a crank angle region in which at least one of the intake valves 37 or the exhaust valves 38 of all the cylinders is fully closed, that is, all the cylinders are in the valve overlap period. It is possible to stop in the crank angle region where it does not become. In the present embodiment, the fuel injection amount immediately before stop is set to a fixed value obtained in advance through experiments or the like, but when the influence of friction is caused by the engine temperature, the fuel injection amount immediately before stop is set to the cooling water temperature at that time, Correction may be made based on the oil temperature of the engine, the oil temperature of the automatic transmission, or the like.

  Thereafter, the process proceeds to step S22, the fuel injection amount immediately before stop is output, a fuel cut signal is issued in step S23, and the process proceeds to step S6 in FIG. The fuel injection amount immediately before stop output from the engine stop processing means is read by a fuel injection control program (not shown), and is output at a predetermined timing to the injector 31 of the fuel injection target cylinder to be reached this time. The injector 31 is injected toward the intake valve 37 while the intake valve 37 of the fuel injection target cylinder is closed. When the intake valve 37 is opened in the intake stroke, the air-fuel mixture is injected into the cylinder. Supplied as

  When the process proceeds to step S6 in FIG. 3, the electric compressor 23 is turned off to stop the supercharging operation by the electric supercharger 21, and then the process proceeds to step S7, where the shutter actuator 25b of the electric shutter 25 is driven and the intake shutter. The valve 25a is fully closed to close the intake pipe 9. Then, as shown in FIG. 1, the electric supercharger 21 is connected to the pipe line from the downstream side of the intake shutter valve 25a of the intake pipe 9 to the upstream side of the intake valve 27 or the exhaust valve 28 of each closed cylinder. Air pressurized by the compressor impeller 23a is enclosed.

  On the other hand, when it is determined in step S1 that the restart condition is satisfied and the process proceeds to step S3, the shutter actuator 25b of the electric shutter 25 is driven to fully open the intake shutter valve 25a, and the process proceeds to step S8 to perform the engine restart process. Execute and proceed to step S9. The engine restart process executed in step S8 is processed according to the engine restart process subroutine shown in FIG. In this routine, first, the starter motor 46 is driven in step S31 to crank the engine 1, and the process proceeds to step S32. The engine rotation speed Ne is the engine rotation speed that rotates spontaneously. It is checked whether or not Ns (for example, 450 to 600 [rpm]) has been reached, and cranking by the starter motor 46 is continued until the engine speed Ne reaches the start determination speed Ns.

  When the engine speed Ne reaches the start determination speed Ne (Ne ≧ Ns), the process proceeds to step S33, the drive of the starter motor 46 is turned off, and the process proceeds to step S9 in FIG.

  When the process proceeds to step S9 in FIG. 3, the electric compressor 23 is turned on, and the process proceeds to step S10. The electric compressor 23 at this time is rotated at a preset initial rotational speed, and after the engine 1 is started, the electric compressor 23 is controlled based on the engine operating state in step S5 described above.

  As described above, during idle stop, the intake shutter valve 25a is fully closed, and at least one of the intake valve 27 and the exhaust valve 28 of each cylinder is closed. Air pressurized by the electric supercharger 21 before idling stop is enclosed in a section between the valve and the intake shutter valve 25a. Therefore, when the engine is restarted, when the intake shutter valve 25a is opened and the engine 1 is started, the pressurized air enclosed in the section is supplied to each cylinder, so that the charging efficiency is improved. The pumping loss when cranking the engine 1 is reduced, and the engine 1 can be relatively started up in a short time. As a result, even when the idle stop is repeatedly performed, not only the load applied to the starter motor at the time of restart is reduced, but also a good restartability can be obtained. Further, since the energization time for the starter motor 46 at the time of restart is shortened, the power consumption of the battery 43 is reduced correspondingly, and the fuel consumption can be further improved.

  Thereafter, when the process proceeds from step S5 or step S9 to step S10, whether or not the electric power generated by the thermoelectric conversion element 36 can be stored in the battery 43 is checked based on the remaining amount SOC of the battery 43. The process branches to step S12 when it is determined that the battery 43 is fully charged and cannot be charged.

  By the way, when the engine 1 is operated and exhaust gas is discharged, the exhaust pipe 12 is heated by the thermal energy of the exhaust gas. The heat of the exhaust pipe 12 is received by the thermoelectric conversion element 36 to generate electricity and generate electric power.

  In step S11, the discharge changeover switch 47 is connected to the charging unit 43b provided in the battery 43, and the electric power generated in the thermoelectric conversion element 36 is charged via the charging unit 43b. Exit. On the other hand, if it progresses to step S12, the discharge changeover switch 47 will be connected to the electric power consumption unit 44 side, such as a cooling fan, the electric power which generate | occur | produced in the thermoelectric conversion element 36 will be consumed, and a routine will be exited.

  Thus, in this embodiment, at the time of idling stop, the intake shutter valve 25a interposed in the intake pipe 9 is closed, and at least one of the intake valve 27 and the exhaust valve 28 of each cylinder is closed. Since the engine is stopped, the air pressurized by the electric supercharger 21 is held between the intake shutter valve 25a and the closed valve (at least one of the intake valve 27 and the exhaust valve 28). ing. Therefore, when the intake shutter valve 25a is fully opened at the time of restart and the engine 1 is cranked, the pressurized air is supplied to each cylinder to improve the charging efficiency, and the pumping loss is reduced correspondingly. As a result, shortening of the cranking time can be realized, not only good restartability can be obtained, but also a sense of security can be given to the driver.

  In addition, since the cranking time at the time of restart is shortened, the load applied to the starter motor 46 is reduced and the durability is improved even if the idling stop is repeatedly performed. Furthermore, since the energization time for the starter motor 46 is shortened due to the shortening of the cranking time, the power consumption is reduced and the fuel consumption can be improved.

  Further, in the present embodiment, since the air supplied to each cylinder is pre-pressurized when the engine is restarted, it is not necessary to increase the supercharging pressure suddenly by the electric supercharger 21. However, the capacity of the electric supercharger 21 can be relatively reduced, and the weight can be reduced by reducing the capacity. In addition, since the intake air is supercharged from the initial stage of restart, good running performance can be obtained. Therefore, for example, even when traveling at a high altitude where the atmospheric pressure is low, the time lag at the time of starting from restart can be shortened, and good traveling performance can be obtained.

  The present invention is not limited to the above-described embodiment. For example, the intake shutter valve 25a is disposed immediately downstream of the compressor impeller 23a, so that the air pressurized in the maximum pipe length section at the time of idle stop is provided. Can be held. Further, if the throttle passage 7 can be fully closed by the throttle valve 8, the throttle valve 8 can also function as the shutter means of the present invention.

Overall configuration of turbocharged engine Configuration diagram of engine control system Flowchart showing an idle stop control routine Flow chart showing engine stop processing subroutine Flow chart showing engine restart processing subroutine

Explanation of symbols

1 ... Engine,
9 ... Intake pipe,
21 ... Electric supercharger,
23 ... Electric compressor,
25. Electric shutter,
25a ... Intake shutter valve,
25b ... shutter actuator,
31 ... Injector,
33 ... Intake pipe pressure sensor,
35. Engine speed sensor,
36 ... thermoelectric conversion element,
37 ... Intake valve,
38 ... exhaust valve,
41 ... Electronic control unit,
43 ... Battery,
46 ... Starter motor

Claims (3)

Electric supercharging means interposed in the intake pipe;
Shutter means that is interposed in the intake pipe leading from the electric supercharging means to the intake valve and that can freely open and close the intake pipe;
A control unit that stops the engine and stops the supercharging operation of the electric supercharging unit and closes the intake passage by the shutter unit when a preset idle stop condition is satisfied ;
The supercharger-equipped engine control device , wherein the shutter means is provided upstream of the throttle valve of the intake pipe that communicates with the intake valve from the electric supercharging means . When the idling stop condition is satisfied and the engine is stopped, the control means closes the fuel injection amount immediately before the fuel cut, at least one of the intake valve and the exhaust valve provided in each cylinder of the engine. 2. The supercharger-equipped engine control device according to claim 1, wherein the control device is set to a value that stops at a crank angle to be valved. 2. The control unit according to claim 1, wherein when a preset restart condition is satisfied, the engine is restarted, the shutter unit is fully opened, and the electric supercharging unit is supercharged. Or the control apparatus of the engine with a supercharger of 2 description.

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