JP2013136974A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To predict a risk of causing abnormal combustion such as super-knocking.SOLUTION: An electromagnetic wave is radiated in a combustion chamber of a cylinder 1 before ignition timing in the cylinder 1, the strength of a reflected wave of the electromagnetic wave is detected, and whether or not to be a state of having a risk of the abnormal combustion is determined based on the detection. When a foreign matter such as lubricating oil, a carbon particle and residual gas causing the abnormal combustion exists in the combustion chamber, a magnitude of reflected electric power returned toward a power meter 19 from an antenna is changed by comparing with a normal case that the foreign matter does not exist. The risk of causing the abnormal combustion is predicted by using this phenomenon.

Description

  The present invention relates to a control device for an internal combustion engine.

  The occurrence of knocking in a cylinder of a spark ignition type internal combustion engine is detected via a knock sensor, and the ignition timing is retarded until knocking does not occur (in other words, the ignition timing is advanced until just before the limit at which knocking occurs). Knock control systems are known (see, for example, the following patent document).

  Recently, research and development has been progressing toward further improving the compression ratio of the cylinders of an internal combustion engine with the aim of further improving fuel efficiency. An internal combustion engine with an improved compression ratio, combined with an exhaust turbocharger, etc., increases the pressure of the intake air that fills the cylinder, resulting in preignition that auto-ignites the mixture before ignition in the combustion chamber of the cylinder. There is an increased risk of knocking much stronger than normal knocking after ignition.

  In particular, if foreign matter such as lubricant oil, carbon particles, or residual gas that has been sprinkled and scattered by the piston ring is present in the combustion chamber, the fuel will be generated when self-ignition occurs near the compression top dead center at the end of the compression stroke. And the foreign matter may burn together, causing an intense explosion called super knocking and damaging parts of the internal combustion engine (connecting rod, cylinder head, etc.).

  However, with a conventional knock control system, it is impossible to predict the possibility of abnormal combustion such as super knocking.

JP 2011-159477 A JP 2011-0664162 A

  An object of the present invention is to predict the possibility of causing abnormal combustion such as super knocking.

  In the present invention, an electromagnetic wave radiating part that radiates an electromagnetic wave before the ignition timing in the cylinder is detected in the combustion chamber of the cylinder, and the intensity of the reflected wave of the electromagnetic wave radiated into the combustion chamber by the electromagnetic wave radiating part is detected. And a control unit that determines whether or not abnormal combustion is likely to occur in the cylinder.

  When the control unit determines that there is a possibility that abnormal combustion may occur in the cylinder, correction control is performed to retard the ignition timing in the cylinder more than in the case where it is determined that this is not the case. Preferably it is done.

  According to the present invention, it is possible to predict the possibility of causing abnormal combustion such as super knocking.

The figure which shows the structure of the internal combustion engine and its control apparatus in one Embodiment of this invention. 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.

  An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the outline | summary of the spark ignition internal combustion engine for vehicles in this embodiment is shown. This internal combustion engine is of a direct injection type, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1), an injector 10 that injects fuel into each cylinder 1, An intake passage 3 for supplying intake air to the cylinder 1, an exhaust passage 4 for discharging exhaust from each cylinder 1, an exhaust turbocharger 5 for supercharging intake air flowing through the intake passage 3, and an exhaust passage And an external EGR device 2 that recirculates EGR gas from 4 toward the intake passage 3.

  A spark plug 13 is attached to the ceiling of the combustion chamber of the cylinder 1. The spark plug 13 receives spark voltage generated by the ignition coil 12 and causes spark discharge between the center electrode and the ground electrode. The ignition coil 12 is integrally incorporated in a coil case together with an igniter 11 that is a semiconductor switching element.

  When the igniter 11 receives an ignition signal i from an ECU (Electronic Control Unit) 0 serving as a control unit of the internal combustion engine, the igniter 11 is first ignited and a current flows to the primary side of the ignition coil 12, and immediately after the ignition timing. The igniter 11 is extinguished to interrupt this current. Then, a self-induction action occurs, and a high voltage is generated on the primary side. Since the primary side and the secondary side share the magnetic circuit and the magnetic flux, a higher induced voltage is generated on the secondary side. This high induction voltage is applied to the center electrode of the spark plug 13, and spark discharge occurs between the center electrode and the ground electrode.

  In addition, an electromagnetic wave radiating portion that radiates electromagnetic waves is attached to the combustion chamber of the cylinder 1. The electromagnetic wave radiating unit in the present embodiment applies a microwave electric field in the combustion chamber, and generates a magnetron 14 that generates a microwave by using a vehicle-mounted battery as a power source, a control circuit 15 that controls the magnetron, and a microtron generated by the magnetron. A transmission circuit 16 for transmitting a wave and an antenna 17 connected to the transmission circuit 16 are used as elements.

  The control circuit 15 receives a control signal j output from the ECU 0, and controls the microwave power oscillated by the magnetron 14 and the oscillation timing based on the control signal j.

  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. A power meter 19 having a different aspect is employed.

  The antenna 17 radiates microwaves oscillated from the magnetron 14 and propagating through the transmission circuit 16 into the combustion chamber of the cylinder 1. The antenna 17 is, for example, a monopole antenna disposed in the vicinity of the ignition plug 13 on the ceiling of the combustion chamber. The tip of the antenna 17 is exposed to the combustion chamber, and the other portion is covered with an insulator. 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 intake passage 3 takes in air from the outside and guides it to the intake port of the cylinder 1. On the intake passage 3, an air cleaner 31, a compressor 51 of the supercharger 5, an intercooler 32, an electronic throttle valve 33, a surge tank 34, and an intake manifold 35 are arranged in this order from the upstream side.

  The exhaust passage 4 guides exhaust generated as a result of burning fuel in the cylinder 1 from the exhaust port of the cylinder 1 to the outside. An exhaust manifold 42, a drive turbine 52 for the supercharger 5, and a three-way catalyst 41 are disposed on the exhaust passage 4. In addition, an exhaust bypass passage 43 that bypasses the turbine 52 and a waste gate valve 44 that is a bypass valve that opens and closes the inlet of the bypass passage 43 are provided. The waste gate valve 44 is an electric waste gate valve that can be opened and closed by inputting a control signal l to the actuator, and a DC servo motor is used as the actuator.

  The exhaust turbocharger 5 is configured such that the drive turbine 52 and the compressor 51 are connected and linked in a coaxial manner. Then, the driving turbine 52 is rotationally driven by using the energy of the exhaust gas, and the compressor 51 is pumped by using the rotational force, whereby the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

  The external EGR device 2 realizes a so-called high-pressure loop EGR. The inlet of the external EGR passage is connected to a predetermined location upstream of the turbine 52 in the exhaust passage 4. The outlet of the external EGR passage is connected to a predetermined location downstream of the throttle valve 33 in the intake passage 3, specifically to a surge tank 34. An EGR cooler 21 and an EGR valve 22 are also provided on the external EGR passage.

  The ECU 0 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 for detecting the vehicle speed, an engine rotation signal b output from an engine rotation sensor for detecting the rotation angle and engine speed of the crankshaft, an accelerator pedal depression amount or a throttle. An accelerator opening signal c output from an accelerator opening sensor that detects the opening of the valve 33 as an accelerator opening (so-called required load), an intake air temperature and an intake pressure in the intake passage 3 (especially, the surge tank 34). An intake air temperature / intake pressure signal d output from a temperature / pressure sensor to be detected, a cooling water temperature signal e output from a water temperature sensor to detect a cooling water temperature of the internal combustion engine, and a cam angle sensor at a plurality of cam angles of the intake camshaft The cam signal f output from the magnet, the intensity of the incident wave emitted from the magnetron 14, and the reflection returned from the antenna 17 Intensity incident wave signal g and the reflected wave signal h etc. are output from the power meter 19 for detecting the is input. The engine rotation sensor generates a pulse signal b every 10 ° CA (crank angle). The cam angle sensor generates a pulse signal g at an angle obtained by dividing 720 ° CA by the number of cylinders, or every 240 ° CA for a three-cylinder engine.

  From the output interface, an ignition signal i for the igniter 11, a microwave generation command signal j for the control circuit 15 of the magnetron 14, an opening operation signal k for the throttle valve 33, and an opening operation signal k for the waste gate valve 44. Degree operation signal l, an opening degree operation signal m to the EGR valve 22, a fuel injection signal n to the injector 10, and the like.

  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, the required fuel injection amount, fuel injection timing (including the number of fuel injections for one combustion), fuel injection pressure, ignition timing, and a microwave electric field are generated in the combustion chamber. Various operating parameters such as whether or not to perform the operation, the generation timing thereof, the EGR amount (or EGR rate), and the opening degree of the EGR valve 22 are determined. As the operation parameter determination method itself, a known method can be adopted, and the description thereof will be omitted. The ECU 0 applies various control signals i, j, k, l, m, and n corresponding to the operation parameters via the output interface.

  The ECU 0 in this embodiment radiates electromagnetic waves into the combustion chamber of the cylinder 1 before the ignition timing in the compression stroke in the cylinder 1 and detects the intensity of the reflected wave via the power meter 19. Then, based on the intensity of the reflected wave, it is determined whether or not there is a possibility that abnormal combustion such as pre-ignition or super knocking may be caused in the cylinder 1.

  If foreign matter such as lubricant oil, carbon particles, residual gas, etc., scattered by the piston ring is scattered in the combustion chamber of the cylinder 1, this foreign matter burns with the fuel and is compared with normal knocking. It may fall into an abnormal combustion state with a far greater impact. When such foreign matter is present in the combustion chamber and the electromagnetic wave is radiated into the combustion chamber, the magnitude of the reflected power returned from the antenna 17 toward the power meter 19 is normal. It changes compared to the case.

  The ECU 0 determines that the intensity of the reflected wave detected via the power meter 19 deviates from a predetermined range expected as a normal intensity obtained experimentally (by adaptation) in advance or exceeds a predetermined threshold value. If it is larger / smaller, it is determined that there is a possibility of causing abnormal combustion.

  When it is determined that there is a possibility that abnormal combustion may occur, the ECU 0 implements measures for avoiding abnormal combustion in the cylinder 1. Specific examples are listed below.

(A) Correction for significantly retarding the current ignition timing in the cylinder 1 as compared with the normal time;
If ignition is performed at a normal timing in a situation where there is a possibility of abnormal combustion, strong knocking may occur in the cylinder 1. Therefore, the ignition timing is retarded to ignite and burn, thereby avoiding strong knocking. At that time, it is also preferable that after ignition, an electromagnetic wave is radiated into the cylinder 1 to improve the combustion speed so that unburned fuel is not left. It is conceivable that the cylinder 1 is not ignited this time and the air-fuel mixture containing unburned fuel (and foreign matter) is discharged in the exhaust stroke (however, a separate measure is required to prevent the emission from deteriorating). .

(B) The current fuel injection in the cylinder 1 is stopped, or the fuel injection amount (or the number of injections) is corrected to be reduced as compared with the normal time;
When it is in the operating region in which fuel is injected into the cylinder 1 during the compression stroke, when it is detected that abnormal combustion occurs, the fuel injection is immediately interrupted or the amount of fuel to be injected is reduced. By doing so, preignition, super knock, etc. are avoided. Even if the fuel injection amount is reduced and the air-fuel ratio of the air-fuel mixture is made lean, the combustion speed can be improved by radiating electromagnetic waves into the cylinder 1, and avoiding excessive reduction in the engine output torque. It is done.

(C) The electromagnetic wave emission for promoting the current combustion in the cylinder 1 is stopped, or the electromagnetic wave emission intensity is reduced compared with the normal time, the emission time is reduced compared with the normal time, or the electromagnetic wave Make corrections to change the radiation time from that of normal times;
The electromagnetic wave radiating unit of the present embodiment is a cylinder 1 for the purpose of steadily igniting the air-fuel mixture in the cylinder 1 to obtain a stable flame, or for enhancing the flame existing in the cylinder 1 (increasing the combustion speed). It can be used for generating plasma by forming an electric field inside. In the former, electromagnetic waves are radiated immediately before ignition, simultaneously with ignition, or immediately after ignition, and a large flame nucleus is formed in the vicinity of the electrode of the spark plug 13 to start flame propagation combustion. In the latter, electromagnetic waves are emitted at a desired time after ignition, and plasma is generated (particularly in the vicinity of the inner peripheral surface of the cylinder 1 where the combustion temperature is lowered) to enhance flame propagation. In the latter case, even if the combustion becomes unstable due to the weakening of the flame in the middle of the expansion stroke, the combustion can be promoted again in the same expansion stroke. Incidentally, the energy of electromagnetic waves radiated before ignition for determining whether or not abnormal combustion is likely to occur is smaller than the energy of electromagnetic waves radiated after ignition for promoting combustion. In any case, the situation where abnormal combustion is likely to occur is a situation where intense combustion is likely to occur, and it can be said that there is little need to promote combustion. Therefore, when it is detected that abnormal combustion occurs, the emission of electromagnetic waves is stopped, the radiated power of electromagnetic waves is lowered, the emission period is shortened, or the emission timing is delayed.

  Any one of the above (A), (B), and (C) may be carried out alone or in combination.

  According to the present embodiment, an electromagnetic wave radiation unit (magnetron 14, control circuit 15, transmission circuit 16, antenna 17) that radiates electromagnetic waves into the combustion chamber of the cylinder 1 before the ignition timing in the cylinder 1 and the electromagnetic wave radiation. And a control unit 0 for detecting the intensity of the reflected wave of the electromagnetic wave radiated into the combustion chamber by the unit and determining whether or not there is a possibility of abnormal combustion in the cylinder 1 based on the intensity. Therefore, it is possible to predict the possibility of abnormal combustion such as pre-ignition, super knocking, etc., and control for preventing such abnormal combustion is performed to control the internal combustion engine. It is possible to avoid damage in various places.

  In the system that radiates electromagnetic waves into the combustion chamber of the cylinder 1 to promote the combustion of fuel in the cylinder 1, when the fear of abnormal combustion is detected, the radiation intensity of the electromagnetic waves is reduced or radiated. By implementing correction control that shortens the time, energy consumed by electromagnetic radiation is saved, and fuel efficiency is improved.

  In addition, when the control unit 0 determines that there is a possibility that abnormal combustion may occur in the cylinder 1, the ignition timing in the cylinder 1 is delayed more than when it is determined that it is not. As an angler, damage to the internal combustion engine can be more reliably prevented. Further, it is more effective to correct the fuel injection amount in the cylinder 1 by reducing the fuel injection amount.

  The present invention is not limited to the embodiment described in detail above. The electromagnetic wave radiation unit that generates an electric field in the combustion chamber (which may be used for the purpose of generating plasma in the combustion chamber) is not limited to the microwave generator. In other words, instead of radiating microwaves from the antenna into the combustion chamber, high frequencies may be radiated.

  As an electric field generator other than the microwave generator, an AC voltage generator circuit that applies a high-frequency AC voltage, a pulsating voltage generator circuit that applies a high-frequency pulsating voltage, or the like can be employed. When the pulsating voltage generation circuit is employed, any circuit may be used as long as it 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 1000 kHz and an amplitude of about 3 kVp-p to 10 kVp-p.

  An antenna that radiates microwaves or electromagnetic waves into the combustion chamber of the cylinder and an antenna that receives reflected waves of the electromagnetic waves radiated into the combustion chamber may be separated. In this case, the control unit determines whether or not there is a possibility of abnormal combustion in the cylinder based on the intensity of the electromagnetic wave received by the latter 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 applied to a spark ignition internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 14, 15, 16, 17 ... Electromagnetic radiation part

Claims (2)

An electromagnetic wave radiation part that radiates an electromagnetic wave before the ignition timing in the cylinder in the combustion chamber of the cylinder;
A control unit that detects the intensity of the reflected wave of the electromagnetic wave radiated into the combustion chamber by the electromagnetic wave radiating unit and determines whether or not abnormal combustion may occur in the cylinder based on the intensity; A control apparatus for an internal combustion engine. The control unit according to claim 1, wherein when the control unit determines that there is a possibility that abnormal combustion may occur in the cylinder, the ignition timing in the cylinder is delayed more than when it is determined that the control unit does not. Control device for internal combustion engine.

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