JP2014185544A - Control device of spark ignition type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect failure generated in a system producing an electric field in a combustion chamber.SOLUTION: In an internal combustion engine of an embodiment in which plasma is produced in a combustion chamber by interaction of an electric field radiated into the combustion chamber through an antenna facing the combustion chamber of a cylinder, and a spark discharge generated between a central electrode of an ignition plug and a ground electrode to ignite an air-fuel mixture, a magnitude of reflection wave measured in radiating the electric field from the antenna in fuel cut, and a magnitude of reflection wave measured in radiating the electric field from the antenna before execution of fuel cut or after termination of the fuel cut are compared. When the former is larger than the latter by a prescribed value or more, it is determined that a system is not failed, otherwise it is determined that a certain failure is generated in the system.

Description

  The present invention relates to a control device for controlling a spark ignition internal combustion engine.

  In an ignition device mounted on a spark ignition type internal combustion engine, a high voltage generated in the ignition coil when the igniter is extinguished is applied to the center electrode of the ignition plug, so that the center electrode of the ignition plug and the ground electrode are A spark discharge is caused between and ignited.

  Recently, in order to ensure that the air-fuel mixture in the combustion chamber of the cylinder is ignited and a stable flame can be obtained, an electric field generation circuit, in other words, a microwave or high-frequency oscillator output from the magnetron is output. An ignition method for radiating a high frequency to the combustion chamber has been attempted (see, for example, Patent Document 1 or 2 below). According to this ignition method, a microwave or high-frequency electric field is formed in the gap between the center electrode and the ground electrode, and the plasma generated in this electric field grows to form a large flame nucleus that starts the flame propagation combustion. Can be generated.

  If microwaves or high-frequency waves radiated into the combustion chamber leak out of the internal combustion engine, electric and electronic devices inside and outside the engine room are brought into contact, and there is a concern that the operation of these devices may be adversely affected. Therefore, it is necessary to detect leakage of microwaves or high-frequency electric fields first, but installing a new device for detecting leakage of electric fields has the disadvantage of increasing costs and even a narrow engine room. The problem of the space of where to place the device is also annoying.

  In addition, it is necessary to consider in advance the possibility of disconnection or short-circuiting on the line connecting the magnetron or high-frequency oscillator and the antenna.

JP 2011-159477 A JP 2011-0664162 A

  The present invention is intended to detect when a failure occurs in a system that emits an electric field in a combustion chamber in an internal combustion engine that emits an electric field in the combustion chamber along with spark discharge. It is aimed.

  In the present invention, the electric field radiated into the combustion chamber via the antenna facing the combustion chamber of the cylinder interacts with the spark discharge generated between the center electrode and the ground electrode of the spark plug to generate plasma in the combustion chamber. The spark ignition type internal combustion engine that generates and ignites the air-fuel mixture is controlled, and the fuel cut is performed to temporarily stop the fuel injection when the fuel cut condition is satisfied. By comparing the magnitude of the reflected wave measured when radiated with the magnitude of the reflected wave measured when the electric field is radiated from the antenna before the fuel cut is performed or after the fuel cut is completed, A control device for a spark ignition internal combustion engine is characterized in that it is determined whether or not a failure has occurred in a system that generates an electric field.

  In particular, the magnitude of the reflected wave measured as a result of radiating an electric field in the period before the fuel cut is actually started after the fuel cut condition is established, and the reflected wave measured as a result of radiating the electric field after the fuel cut is started By comparing with the size of the cylinder, it is possible to make the comparison with the temperature in the combustion chamber of the cylinder and other conditions being substantially the same, thereby reducing the possibility of oversight of a failure or erroneous determination.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to detect the failure which generate | occur | produced in the system which radiates | emits an electric field in a combustion chamber in the internal combustion engine which ignites by radiating | emitting an electric field in a combustion chamber with a spark discharge.

The figure which shows the structure of the internal combustion engine in one Embodiment of this invention, an electric field generator, and its control apparatus. The figure which shows the example of the antenna which radiates | emits electromagnetic waves in the combustion chamber of the cylinder of the internal combustion engine in the embodiment. The flowchart which shows the example of the procedure of the process which the control apparatus of the embodiment implements.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. This internal combustion engine is a spark ignition type four-stroke gasoline engine and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode.

  The internal combustion engine of the present embodiment is accompanied by an electromagnetic wave radiation portion that generates an electric field in the combustion chamber for the purpose of generating plasma in the combustion chamber of the cylinder 1 at the time of ignition. The electromagnetic wave radiating unit in the present embodiment applies a microwave electric field in the combustion chamber, and is generated by the magnetron 14 that generates a microwave by using an in-vehicle battery as a power source, a control circuit 15 that controls the magnetron 14, and the magnetron 14. The transmission circuit 16 for transmitting the microwave and the antenna 17 connected to the transmission circuit 16 are used as elements.

  The control circuit 15 receives a control signal l output from an ECU (Electronic Control Unit) 0 which is a control device of the present embodiment, and determines the power of the microwave oscillated by the magnetron 14 and the oscillation timing based on the control signal l. Control.

  The transmission circuit 16 mainly includes a waveguide, a coaxial cable, or the like that can propagate microwaves. The transmission circuit 16 is accompanied by an isolator 18 and a power meter 19. The isolator 18 is a protective device for stably operating the magnetron 14 by absorbing a reflected wave from the antenna 17, and is interposed between the magnetron 14 and the antenna 17.

  The isolator 18 includes a circulator and a dummy load. In the circulator, the incident power oscillated from the magnetron 14 and the reflected power returned from the antenna 17 are caused by the action of ferrite and a magnetic field provided in a T-shaped portion (or branching portion) such as a waveguide or a coaxial cable. To separate. Then, the incident power is transmitted to the antenna 17 with almost no loss, while the reflected power is introduced to the dummy load side. The dummy load is, for example, a water-cooled type that absorbs reflected power with water or the like and discharges it as heat. The dummy load is connected to the end of a waveguide, a coaxial cable or the like, and efficiently absorbs excess microwave energy.

  The power meter 19 separately detects incident power propagating from the magnetron 14 toward the antenna 17 and reflected power returned from the antenna 17. The power meter 19 is inserted in the middle of a waveguide or a coaxial cable. The power meter 19 is a known one configured using a directional coupler, a coaxial non-reflection terminator, a crystal mount which is a microwave diode, an ammeter, a coaxial cable, and the like. In this embodiment, both incident power and reflected power can be read simultaneously by connecting a crystal mount, coaxial non-reflection terminator and ammeter to each of the traveling wave detection port and reflected wave detection port of the bidirectional coupler. The power meter 19 of a various aspect is employ | adopted.

  A part of the antenna 17 is exposed in the combustion chamber of the cylinder 1, and radiates microwaves oscillated from the magnetron 14 and propagating through the transmission circuit 16 into the combustion chamber of the cylinder 1. For example, as shown in FIG. 2, the antenna 17 is a monopole antenna disposed near the ignition plug 13 on the ceiling of the combustion chamber. The tip portion is exposed to the combustion chamber and the other portions are covered with an insulator. It is. The tip surface of the antenna 17 is substantially flush with the inner surface of the combustion chamber. However, the shape and arrangement position of the antenna 17 are not uniquely limited.

  The high-frequency voltage oscillated by the magnetron 14 that is an electric field generator is normally applied to the antenna 17 almost simultaneously with the start of spark discharge, immediately before the start of spark discharge, or immediately after the start of spark discharge. Thereby, a microwave electric field is formed in the space around the spark plug 12 in the combustion chamber. Then, plasma is generated through the interaction between the microwave electric field and the spark discharge, and this plasma generates a large radical plasma flame nucleus that starts the flame propagation combustion.

  The number of times the above-mentioned self-running, the flow of electrons due to spark discharge, and the ions and radicals generated by the spark discharge are vibrated and meandered by the influence of the electric field, resulting in a longer path length and collision with surrounding water and nitrogen molecules. This is due to a drastic increase in. Water molecules and nitrogen molecules that have been struck by ions and radicals become OH radicals and N radicals, and the surrounding gas that has been struck by ions and radicals is also ionized, that is, a plasma state. In addition, the region of ignition of the air-fuel mixture increases and the flame kernel also increases. As a result, the two-dimensional ignition by only the spark discharge is amplified to the three-dimensional ignition, and the combustion rapidly propagates into the combustion chamber and expands at a high combustion speed.

  An intake passage 3 for supplying intake air to the cylinder 1 of the internal combustion engine takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for exhausting the exhaust from the cylinder 1 guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  The ECU 0 that controls operation of the internal combustion engine is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. The accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (so-called required load), the intake air temperature and the intake pressure in the intake passage 3 (particularly, the surge tank 33). The intake air temperature / intake pressure signal d output from the temperature / pressure sensor to be detected, the coolant temperature signal e output from the water temperature sensor to detect the coolant temperature of the engine, and a plurality of cam angles of the intake camshaft or exhaust camshaft The cam angle signal f output from the cam angle sensor, the intensity of the incident wave emitted from the magnetron 14 and the antenna 17 Incident wave signal g and the reflected wave signal h etc. are output from the power meter 19 for detecting the intensity of the reflected wave coming I is entered.

  From the output interface, an ignition signal i for the igniter of the spark plug 12, a fuel injection signal j for the injector 11, an opening operation signal k for the throttle valve 32, and a microwave for the control circuit 15 of the magnetron 14. The generation command signal l and the like are output.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed and intake air amount, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, and an electric field are generated in the combustion chamber. Various operating parameters such as whether or not and the strength of the electric field are determined. The ECU 0 applies various control signals i, j, k, and l corresponding to the operation parameters via the output interface.

  The ECU 0 of the present embodiment performs fuel cut that stops fuel injection from the injector 11 and stops spark ignition by the spark plug 12 when a predetermined fuel cut condition is satisfied. The ECU 0 determines that the fuel cut condition is satisfied, at least when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed.

  Incidentally, even if the fuel cut condition is satisfied, the fuel injection is not immediately stopped. If the fuel supply is cut off suddenly when the engine torque is relatively large, a torque shock that causes the engine speed and the vehicle speed to drop stepwise occurs, causing the passengers including the driver to feel the shock. In order to reduce the torque shock, the fuel injection is stopped only after the elapse of the delay time after the fuel cut condition is satisfied. During this delay time, the ignition timing is retarded and the engine torque is actively reduced.

  When a predetermined fuel cut end condition is satisfied after the start of the fuel cut, the fuel cut is ended, and fuel injection and spark ignition are resumed. The ECU 0 determines that the fuel cut end condition is satisfied, for example, when the accelerator pedal depression amount exceeds the threshold value or the engine speed has decreased to the fuel cut return speed.

  Further, the ECU 0 executes an idle stop that stops the idle rotation of the internal combustion engine when a predetermined idle stop condition is satisfied. The ECU 0 is established by satisfying all the conditions that the vehicle speed is not more than a predetermined value (for example, a value of 10 km / h to 13 km / h), the brake pedal is depressed, and the cooling water temperature and the battery voltage are sufficiently high. It is determined that the idle stop condition is satisfied.

  After the start of the fuel cut, if the idle stop condition is satisfied without the fuel cut end condition being satisfied, the fuel cut to the idle stop can be performed without interposing the restart of fuel injection between the fuel cut and the idle stop. It will be consistent and continuous.

  The ECU 0 restarts the internal combustion engine when a predetermined idle stop end condition is satisfied after the idle stop condition is satisfied. The ECU 0 is one in which the driver takes his foot off the brake pedal, the brake pedal is depressed more strongly, the accelerator pedal is depressed, a predetermined time (for example, 3 minutes) has elapsed in the idle stop state, etc. In any case, it is determined that the idle stop termination condition is satisfied.

  The ECU 0 inputs a control signal o to an electric motor (starter motor or motor generator) when starting the internal combustion engine (a cold start or a return from an idling stop), and the crankshaft is driven by the electric motor. Perform cranking to rotate. Cranking ends when the internal combustion engine starts from the first explosion to a continuous explosion and the engine speed, that is, the rotation speed of the crankshaft, exceeds a judgment value determined according to the coolant temperature, etc. (assuming that the explosion has been completed) To do.

  Thus, the ECU 0 of this embodiment determines whether or not a failure has occurred in the system that generates an electric field in the combustion chamber of the cylinder 1 when the fuel cut condition is satisfied. As types of failure, leakage of microwaves radiated from the antenna 17 into the combustion chamber of the cylinder 1 to the outside of the internal combustion engine (cylinder 1, intake passage 3 or exhaust passage 4), or a line 16 connecting the magnetron 14 and the antenna 17 Disconnection or short circuit, or abnormalities of devices such as the isolator 18 and the power meter 19 existing on the line 16.

  FIG. 3 shows a procedure example of processing executed by the ECU 0 in determining whether there is a system failure. The ECU 0 radiates a microwave from the antenna 17 at a time before starting the fuel cut (step S3) for actually stopping the fuel injection and ignition after the fuel cut condition is established (step S1). The intensity of the reflected wave (particularly, the ratio of the reflected power returned from the antenna 17 to the incident power propagating from the magnetron 14 toward the antenna 17) is measured via the power meter 19 (step 2).

  The reflected wave is measured in step S2 under the condition that the air-fuel mixture is burned in the combustion chamber of the cylinder 1 and ions or plasma are generated. The microwave radiation at this time may be intended to ignite the mixture (interaction between spark ignition and microwave electric field), or may be independent from the ignition to the mixture ( The ignition may be performed only by spark ignition, and the microwave radiation may be measured only for the reflected wave), but the timing at which both the intake valve and the exhaust valve of the cylinder 1 are closed, that is, compression top dead center. It is desirable to execute within the range of the expansion stroke from the vicinity.

  In addition, the ECU 0 radiates a microwave from the antenna 17 during the fuel cut, and measures the intensity of the reflected wave via the power meter 19 (step 4). The measurement of the reflected wave in step S4 is performed under the situation where there is little or no ions or plasma in the combustion chamber of the cylinder 1. The microwave radiation at this time is also preferably executed at the timing when both the intake valve and the exhaust valve of the cylinder 1 are closed, that is, within the range of the expansion stroke from the vicinity of the compression top dead center.

  Further, the ECU 0 radiates the microwave from the antenna 17 and measures the intensity of the reflected wave via the power meter 19 even after the fuel cut is finished and the fuel injection and ignition are restarted (step S5). Step 6). Step S5 may be accompanied by the fact that the fuel cut end condition is satisfied during the fuel cut, or may be after the internal combustion engine that has been idle stopped. In any case, step S6 is exactly the same as step S2.

  Then, the ECU 0 compares the magnitude of the reflected wave measured in step S2, the magnitude of the reflected wave measured in step S4, and the magnitude of the reflected wave measured in step S6.

  The microwaves radiated from the antenna 17 in step S2 and step S6 are absorbed by ions or plasma existing in the combustion chamber, and the electric power is consumed. Therefore, the microwave should be partially reflected. In contrast, the microwave radiated from the antenna 17 in step S4 consumes little or no power due to the absence of ions or plasma in the combustion chamber. Therefore, the microwave should be almost totally reflected.

  Therefore, comparing the reflected wave measured in step S4 with the reflected wave measured in step S2 and / or S6, the former is larger than the latter by a predetermined amount (or the ratio of the former to the latter is larger than the predetermined value). If so (step S7), it can be determined that the microwave output from the magnetron 14 is normally propagated through the transmission circuit 16 and radiated into the combustion chamber of the cylinder 1, that is, there is no failure in the system (step S8). ).

  Otherwise, it is considered that some sort of failure has occurred in the system. In particular, the reflected wave measured in step S2, the reflected wave measured in step S4, and the reflected wave measured in step S6 are all greater than a predetermined high threshold (step S9), that is, whether combustion has occurred in the combustion chamber. However, if the reflected wave is large, reflection occurs along the route from the magnetron 14 to the antenna 17 (this reflection is caused by disconnection or short circuit of the transmission circuit 16 or the isolator 18 existing on the transmission circuit 16). It can be determined that the microwave is not sufficiently radiated into the combustion chamber of the cylinder 1 (step S10).

  Alternatively, all of the reflected wave measured in step S2, the reflected wave measured in step S4, and the reflected wave measured in step S6 are smaller than a predetermined low threshold value (step S11), that is, whether there is combustion in the combustion chamber. However, if the reflected wave is small, it can be determined that the microwave electric field radiated from the antenna 17 is leaking outside the internal combustion engine (step S12).

  The ECU 0 that has detected that there is a failure in the system for forming the microwave electric field in the combustion chamber determines the failure type (reflection on the way path (step S10), leakage (step S12) according to the determination result. Information (diagnosis code) for identifying the failure) is stored and retained in the memory (step S13) to assist in the investigation of the cause and the search for the repair location in the subsequent inspection and repair work.

  In addition, the ECU 0 notifies the driver that the failure exists in the system in a manner to appeal to the driver's audiovisual sense (step S15). In step S15, for example, a warning light (engine check lamp) installed in the cockpit of the vehicle is turned on, displayed on a display, or a warning sound is output from a buzzer or a speaker.

  Further, in the subsequent operation, ignition for radiating a microwave electric field into the combustion chamber of the cylinder 1 is prohibited (step S14). That is, in the subsequent operation, the microwave is not radiated from the antenna 17, and the air-fuel mixture filled in the cylinder 1 is ignited only by spark discharge by the spark plug 12, and the air-fuel mixture is combusted.

  In the present embodiment, the electric field radiated into the combustion chamber via the antenna 17 facing the combustion chamber of the cylinder 1 and the spark discharge generated between the center electrode and the ground electrode of the spark plug 12 interact to burn. Controls a spark ignition type internal combustion engine that generates plasma in the room and ignites the air-fuel mixture, and performs fuel cut to temporarily stop fuel injection when the fuel cut condition is established. The magnitude of the reflected wave measured when the electric field is radiated from the antenna 17 in step S4), and the electric field is radiated from the antenna 17 before the fuel cut is performed (step S2) or after the fuel cut is completed (step S6). By comparing the magnitude of the reflected wave measured at the time of failure, it is possible to determine whether or not the system that generates the electric field in the combustion chamber has failed. To constitute a control apparatus 0 for a spark ignited internal combustion engine according to symptoms.

  According to the present embodiment, it is possible to detect the occurrence of a system failure at low cost without mounting a dedicated device for detecting disconnection of the transmission circuit 16 or leakage of the microwave electric field to the outside of the internal combustion engine. Is possible.

  In addition, after the fuel cut condition is established, the magnitude of the reflected wave measured as a result of radiating the electric field at the time immediately before actually starting the fuel cut (step S2) is determined during the fuel cut immediately thereafter (step S4). Since the presence or absence of a system failure is determined by comparing with the magnitude of the reflected wave measured as a result of radiating the electric field to the cylinder, the temperature in the combustion chamber of the cylinder 1, the intake air temperature, the intake air humidity, the atmospheric pressure, the fuel Both reflected waves can be compared with substantially the same temperature and other conditions. Therefore, the possibility of missing a failure or misjudging that it is a failure even though there is no failure is reduced. Further, when the fuel cut condition is satisfied, the accelerator opening is small in the first place, and the fuel injection amount and thus the engine output is small. Therefore, even if the electromagnetic wave is radiated from the antenna 17 before the start of the fuel cut, the engine output is large. It does not fluctuate. Electromagnetic radiation and reflected wave measurement need only be performed for a short period of time immediately before the start of fuel cut execution and during subsequent fuel cuts, so that failure determination can be completed quickly and power consumption can be reduced.

  The present invention is not limited to the embodiment described in detail above. For example, as a condition in which the branch determination in step S7 is true (determines that there is no failure), the reflected wave measured in step S4 is larger than a predetermined high threshold and / or in steps S2 and / or S6. It may be added that the measured reflected wave is smaller than a predetermined low threshold.

  An electric field generator that generates an electric field for the purpose of generating plasma in the combustion chamber of the cylinder 1 of the internal combustion engine is not limited to the magnetron 14. As the electric field generator, an AC voltage generation circuit that outputs a high-frequency AC voltage and applies it to the antenna, a pulsating voltage generation circuit that outputs a high-frequency pulsating voltage and applies it to the antenna, or the like may be employed.

  When a pulsating voltage generation circuit is employed as the electric field generation device, the pulsating voltage generation circuit may be any circuit that generates a DC voltage whose voltage periodically changes, and its waveform may be arbitrary. The pulsating voltage includes a pulse voltage that varies from a reference voltage (which may be 0V) to a constant voltage in a constant cycle, a voltage obtained by half-wave rectifying an AC voltage, a voltage obtained by adding a DC bias to the AC voltage, and the like. The high frequency voltage oscillated by the electric field generator preferably has a frequency of about 200 kHz to 3000 kHz and an amplitude of about 3 kVp-p to 10 kVp-p.

  Although the internal combustion engine in the above embodiment is mounted with the antenna 17 for electrolytic radiation separately from the spark plug 12, the microwave or high frequency output from the electric field generator is applied to the center electrode of the spark plug 12. Then, an electric field may be emitted from the center electrode into the combustion chamber of the cylinder 1, that is, the center electrode of the spark plug 12 may be used as an antenna.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be used for controlling an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 14 ... Magnetron 17 ... Antenna 19 ... Power meter

Claims (2)

The electric field radiated into the combustion chamber via the antenna facing the combustion chamber of the cylinder interacts with the spark discharge generated between the center electrode and the ground electrode of the spark plug to generate plasma in the combustion chamber and mix Controls a spark ignition internal combustion engine that ignites.
With the fuel cut condition established, we will implement a fuel cut that temporarily stops fuel injection,
The magnitude of the reflected wave that is measured when an electric field is radiated from the antenna during a fuel cut, and the magnitude of the reflected wave that is measured when the electric field is radiated from the antenna before or after the completion of the fuel cut A control apparatus for a spark ignition type internal combustion engine, characterized by determining whether or not a failure has occurred in a system that generates an electric field in a combustion chamber by comparing the two. After the fuel cut condition is established, the magnitude of the reflected wave measured as a result of radiating the electric field before the actual fuel cut is started, and the magnitude of the reflected wave measured as a result of radiating the electric field after the fuel cut is started 2. The control device for a spark ignition type internal combustion engine according to claim 1, wherein

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