JP6525839B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device that controls the operation of an internal combustion engine mounted on a vehicle or the like.

  During the compression stroke or expansion stroke of a cylinder of an internal combustion engine, a "compression leak" may occur in which gas leaks from the combustion chamber of the cylinder to the intake port or exhaust port. This compression leak typically occurs when foreign matter (deposit) is caught between the valve body of the intake or exhaust valve and the valve seat.

  If compression leakage is repeated over multiple cycles, and fuel injection is continued as normal during that time, the emission may deteriorate, or the spark plug may wear as a result of unburned fuel accumulating in the intake port, or It induces a backfire in which a flame flows backward from the combustion chamber to the intake port.

  In the following patent document, the amount of heat generated in the cylinder is calculated based on the in-cylinder pressure (pressure in the combustion chamber) detected via the in-cylinder pressure sensor, and the calorific value and the air-fuel ratio detected via the air-fuel ratio sensor A system is disclosed that determines the presence or absence of compression leakage in the cylinder based on the fuel ratio. However, adopting such a system requires an expensive in-cylinder pressure sensor to be installed in each cylinder, resulting in an increase in cost.

JP 2012-149562 A

  An object of the present invention is to simply detect the leakage of gas from the combustion chamber of a cylinder and to control or avoid the problem due to the leakage.

  In order to solve the above-mentioned problems, in the present invention, when the length of time of generation of the ion current signal flowing through the electrode of the spark plug due to the combustion of the fuel in the combustion chamber of the cylinder is within the predetermined range. The internal combustion engine temporarily suspends the execution of fuel injection and ignition in the cylinder, and thereafter provides a period in which only ignition is performed without fuel injection in the cylinder, and then resumes the execution of fuel injection and ignition in the cylinder. I configured the control unit.

  According to the present invention, it is possible to simply detect the leakage of gas from the combustion chamber of the cylinder and to control or avoid the problem due to the leakage.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows schematic structure of the internal combustion engine for vehicles in one Embodiment of this invention. The circuit diagram of the spark-ignition apparatus in the embodiment. The figure which shows each transition of the combustion pressure in the cylinder of an internal combustion engine, and an ionic current. The flowchart which shows the content of the control which the control apparatus of the embodiment performs.

  One embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a vehicle internal combustion engine in the present embodiment. The internal combustion engine in the present embodiment is a spark-ignition four-stroke 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 toward the cylinder 1 is provided. Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1.

  FIG. 2 shows an electric circuit for spark ignition. The spark plug 12 receives the application of the induction voltage generated in the ignition coil 14 to cause a spark discharge between the center electrode and the ground electrode. The ignition coil 14 is integrated with the igniter 13 having the semiconductor switching element 131 integrally with the coil case.

  When the igniter 13 receives an ignition signal i from an ECU (Electronic Control Unit) 0, which is a control device for an internal combustion engine, the semiconductor switch 131 of the igniter 13 is first ignited, and current flows on the primary side of the ignition coil 14. The semiconductor switch 131 is extinguished at the timing of spark ignition, and this current is cut off. 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. The induced voltage on the secondary side reaches 10 kV to 30 kV. This high induction voltage is applied to the center electrode of the spark plug 12 and sparks between the center electrode and the ground electrode.

  The primary coil of the ignition coil 14 is connected to the on-vehicle power supply battery 17 through the semiconductor switch 131. When the semiconductor switch 131 is ignited and a DC voltage supplied from the battery 17 is applied to the primary coil to start energization, the primary current flowing through the circuit on the primary side (low voltage system) including the primary coil increases.

  The igniter 13 has a current limiting function to suppress an excessive primary current. This current limiting function is similar to that of ready-made igniters in widespread use today. Specifically, the control circuit 132 constantly measures the primary current in the form of the voltage across the resistor 133 via the detection resistor 133. Then, while the magnitude of the primary current (the voltage across the resistor 133) is less than or equal to a specified value, the semiconductor switch 131 is fired, and when the specified value is exceeded, the semiconductor switch 131 is extinguished.

  The ECU 0 according to the present embodiment can detect the ion current generated in the combustion chamber of the cylinder 1 at the time of fuel combustion, and determine the combustion state and the presence or absence of compression leakage with reference to the ion current.

  As shown in FIG. 2, in the present embodiment, a circuit for detecting an ion current is added to the electric circuit for spark ignition. The detection circuit includes a bias power supply unit 15 for effectively detecting an ion current, and an amplification unit 16 for amplifying and outputting a detection voltage according to the amount of ion current. The bias power supply unit 15 includes a capacitor 151 for storing a bias voltage, a Zener diode 152 for raising the voltage of the capacitor 151 to a predetermined voltage, diodes 153 and 154 for blocking current, and a load for outputting a voltage according to the ion current. And a resistor 155. The amplification unit 16 includes a voltage amplifier 161 represented by an operational amplifier.

  During an arc discharge between the center electrode of the spark plug 12 and the ground electrode, the capacitor 151 is charged, and thereafter, the bias voltage charged in the capacitor 151 causes an ion current to flow in the load resistor 155. The voltage between both ends of the resistor 155 generated by the flow of the ion current is amplified by the amplification unit 16 and received by the ECU 0 as an ion current signal h.

  FIG. 3 illustrates the transition of the ion current and the combustion pressure (in-cylinder pressure) in the cylinder 1 in normal combustion. In FIG. 3, the ion current is drawn by a broken line, and the combustion pressure is drawn by a solid line. Ion current can not be detected during discharge for ignition. The ion current in the case of normal combustion decreases again before compression top dead center due to a chemical reaction after the end of spark ignition, and then increases again by thermal dissociation. Further, the ion current is also maximized almost simultaneously when the combustion pressure reaches a peak.

  An intake passage 3 for supplying intake air takes in air from the outside and leads 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 discharging the exhaust leads 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 a three-way catalyst 41 for exhaust purification are disposed on the exhaust passage 4.

  The exhaust gas recirculation (Exhaust Gas Recirculation) device 2 realizes a so-called high pressure loop EGR, and is an external EGR that communicates the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3. A passage 21, an EGR cooler 22 provided on the EGR passage 21, and an EGR valve 23 for opening and closing the EGR passage 21 and controlling the flow rate of the EGR gas flowing through the EGR passage 21 are elements. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined place downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, in particular, to the surge tank 33.

  A generator (alternator or ISG (Integrated Starter Generator)) 18 serving as a power supply source for energizing the ignition coil 14 and opening / closing driving of the valves 23, 32 and an electric system mounted on a vehicle is a crankshaft of an internal combustion engine. The power is received from the engine torque supply, and the generated power is charged to the on-vehicle battery 17.

  The ECU 0 of the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface and the like.

  The input interface of the ECU 0 includes a vehicle speed signal a output from a vehicle speed sensor that detects an actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects a rotation angle of a crankshaft and an engine rotational speed, and an accelerator pedal. Accelerator opening signal c output from a sensor that detects the stepping amount of the engine or the opening degree of the throttle valve 32 as the accelerator opening (in other words, the required engine load), the water temperature detecting the cooling water temperature indicative of the temperature of the internal combustion engine The cooling water temperature signal d output from the sensor, the battery current / voltage signal e output from the current / voltage sensor that detects the current and / or the voltage of the on-vehicle battery 17, the inside of the intake passage 3 (particularly, the surge tank 33) Intake temperature / intake pressure signal f output from a temperature / pressure sensor that detects intake temperature and intake pressure, intake cam The cam angle signal g output from the cam angle sensor at a plurality of cam angles of the shaft, the current signal h output from the circuit for detecting the ion current generated with the combustion of the air-fuel mixture in the combustion chamber of the cylinder 1, etc. It is input.

  From the output interface of the ECU 0, an ignition signal i to the igniter 13, a fuel injection signal j to the injector 11, an opening operation signal k to the throttle valve 32, an opening operation signal l to the EGR valve 23, etc. Output

  The processor of the ECU 0 interprets and executes a program stored in advance in the memory, calculates operating parameters, and controls the operation of the internal combustion engine. The ECU 0 obtains various information a, b, c, d, e, f, g, h necessary for the operation control of the internal combustion engine through the input interface, obtains the engine speed, and fills the cylinder 1 Estimate the inspiratory volume. The required fuel injection amount, fuel injection timing (including the number of fuel injections per one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR), based on the engine speed and intake amount etc. Determines various operation parameters such as The ECU 0 applies various control signals i, j, k, l corresponding to the operation parameters via the output interface.

  Further, the ECU 0 inputs the control signal o to the electric motor (starter motor or ISG) at the time of starting of the internal combustion engine (may be cold start or may be recovery from idling stop), and the electric motor Perform cranking to rotate the crankshaft. Cranking ends when the internal combustion engine reaches from the first explosion to continuous explosion and the engine speed, that is, the rotational speed of the crankshaft, exceeds a judgment value determined according to the cooling water temperature etc. Do.

  In the ECU 0 of this embodiment, referring to the ion current signal h flowing through the electrode of the spark plug 12, whether compression leakage in which gas leaks from the combustion chamber of the cylinder 1 occurs during the compression stroke or expansion stroke of the cylinder 1 If it is determined that a compression leak has occurred, failsafe control is performed to suppress or avoid the adverse effect.

FIG. 4 shows an exemplary procedure of processing executed by the ECU 0. The ECU 0 generates, for each cylinder 1, the generation time of the ion current signal h appearing after ignition to the air-fuel mixture, that is, the period T during which the magnitude of the ion current signal h exceeds a predetermined threshold, as shown in FIG. Measure the length. Then, based on the length of the generation time T, it is determined whether or not a compression leak has occurred in the compression stroke or expansion stroke closest to the cylinder 1 (step S1). In particular,
(I) If the length of the generation time T of the ion current signal h is equal to or greater than the first determination value, it is determined that the air-fuel mixture has burned normally in the cylinder 1.
(II) If the length of the generation time T of the ion current signal h is less than the first determination value but is not less than the second determination value smaller than the first determination value, the cylinder 1 It is judged that the combustion state of the mixture has deteriorated.
(III) The length of the generation time T of the ion current signal h is less than the second determination value, but smaller than the second determination value (naturally smaller than the first determination value) If it is equal to or greater than the determination value, it is determined that a compression leak has occurred in the cylinder 1.
(IV) If the length of the generation time T of the ion current signal h is less than the third determination value, it is determined that the cylinder 1 has misfired.
The first determination value, the second determination value, and the third determination value are respectively loaded into the operating range of the internal combustion engine at that time [engine speed, engine load (or intake pressure in surge tank 33, cylinder 1 Is preferably set in accordance with the target air-fuel ratio (or fuel injection amount) of the air-fuel mixture at that time. In the memory of the ECU 0, map data defining the relationship between the operating region of the internal combustion engine and / or the air-fuel ratio (fuel injection amount) and each of the above determination values is stored in advance. In step S1, the ECU 0 searches the map using the parameter representing the current operating range of the internal combustion engine and / or the current air fuel ratio (fuel injection amount) as a key, and obtains the determination values to be set. , Used to determine the presence or absence of compression leakage.

  Then, when it is determined that a compression leak has occurred, a period is provided for temporarily stopping the fuel injection from the injector 11 and the spark ignition by the spark plug 12 in the cylinder 1 in which the compression leak has occurred (step S2). . Even during this fuel injection and ignition suspension period, the opening and closing of the intake and exhaust valves associated with the cylinder 1 continue. This waits for the foreign matter (deposit) causing the compression leakage, which is caught between the valve body of the intake valve or the exhaust valve and the valve seat, to be crushed or detached. The length of the fuel injection and ignition suspension period is, for example, about 10 cycles (a series of intake-compression-expansion-exhaust is one cycle).

  After a period for stopping the execution of fuel injection and ignition in the cylinder 1 in which the compression leak has occurred, the ECU 0 resumes only the spark ignition by the spark plug 12 while stopping the fuel injection in the cylinder 1 (step S3) ). As a result, the gas containing the unburned fuel component leaked from the combustion chamber of the cylinder 1 to the intake port (and re-sucked into the cylinder 1) is burned. The length of the period in which only the ignition is performed without the fuel injection is, for example, several cycles.

  After that, the ECU 0 restarts the fuel injection in the cylinder 1, and the fuel is ignited and burned by spark ignition (step S4). It is preferable to adjust the fuel injection amount so that the air-fuel ratio of the air-fuel mixture becomes leaner than the stoichiometric air-fuel ratio at the time immediately after the restart of the fuel injection. The purpose of controlling the air-fuel ratio to be lean is to supply oxygen necessary for oxidizing the unburned fuel component (HC, CO, etc. derived from it) contained in the gas of the compression leakage in the catalyst 41.

  Thus, the ECU 0 measures the length of the generation time T of the ion current signal h appearing after ignition in the cylinder 1 and, based on the length of the generation time T, the closest compression stroke or expansion stroke of the cylinder 1 At step S5, it is determined whether or not compression leakage has occurred at step S5. The content of the determination process of step S5 is basically the same as that of step S1, but the first, second, and third determination values used for the determination are not necessarily the same as those in step S1. In particular, when the air-fuel ratio is controlled to be lean, it is preferable to determine the presence or absence of compression leakage using a determination value corresponding to the air-fuel ratio.

  As a result of the determination in step S5, if it is determined that no compression leakage has occurred in the cylinder 1, the operation is returned to normal operation control in which the air-fuel ratio is controlled to the theoretical air-fuel ratio or in principle. Conversely, if compression leakage occurs again in the cylinder 1, failsafe control of steps S2 to S5 is performed again. It is needless to say that the same failsafe control is executed for the cylinder 1 in which the compression leak has occurred even when the compression leak has occurred in the other cylinder 1.

  In the present embodiment, the length of the generation time T of the ion current signal h flowing through the electrode of the spark plug 12 due to the combustion of the fuel in the combustion chamber of the cylinder 1 is within a predetermined range (from the second judgment value to the third Temporarily stop the execution of fuel injection and ignition in the cylinder 1, and then provide a period in which only ignition is performed without fuel injection in the cylinder 1, and The control device 0 of the internal combustion engine which restarts execution of fuel injection and ignition in the cylinder 1 concerned concerned was constituted.

  According to this embodiment, leakage of gas from the combustion chamber of the cylinder 1 can be easily detected without mounting an expensive in-cylinder pressure sensor in each cylinder 1. And it becomes possible to control thru | or avoid the problem by the leak through fail safe control. That is, it is possible to suppress the deterioration of the emission and to prevent the ignition plug from being covered as a result of the accumulation of the unburned fuel in the intake port, and the ignition to the mixture is stabilized and the startability of the internal combustion engine is also improved. . It also leads to the prevention of backfire in which the flame flows backward from the combustion chamber to the intake port.

  The present invention is not limited to the embodiments detailed above. The specific configuration of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 11 ... Injector 12 ... Ignition plug 3 ... Intake passage 4 ... Exhaust passage 41 ... Catalyst h ... Ion current signal i ... Ignition signal j ... Fuel injection signal

Claims (1)

If the length of time of generation of the ion current signal flowing through the electrode of the spark plug due to the combustion of fuel in the combustion chamber of the cylinder falls within a predetermined range,
Temporarily suspend the execution of fuel injection and ignition in the cylinder,
Thereafter, a period is provided in which only ignition is performed without fuel injection in the cylinder,
Thereafter, the control unit for an internal combustion engine that resumes the execution of fuel injection and ignition in the cylinder.

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