JP2019210827A - Controller for internal combustion engine - Google Patents

Abstract

To provide a controller for an internal combustion engine capable of more reducing costs than conventional arts without needing a combustion pressure sensor.SOLUTION: A control device for an internal combustion engine comprises: an ignition control unit 83 that controls energization of an ignition coil 300 that gives electric energy to an ignition plug 200 that discharges in a cylinder of an internal combustion engine to ignite the fuel; a discharge amount detector 360 that detects the voltage between the electrodes of the ignition plug 200; and an in-cylinder pressure calculation unit 90 that calculates the pressure in the cylinder based on the voltage between electrodes detected by the discharge amount detector 360.SELECTED DRAWING: Figure 4

Description

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

  In recent years, control systems for internal combustion engines have been developed in order to improve vehicle fuel efficiency, including technology that operates with an air-fuel mixture that is thinner than the stoichiometric air-fuel ratio, and technology that incorporates part of the exhaust gas after combustion and reintakes the air. ing.

  In this type of control device for an internal combustion engine, the amount of fuel and air in the combustion chamber deviates from the theoretical value, so that ignition failure of the fuel by the spark plug tends to occur. When poor ignition of fuel occurs, it is necessary to accurately detect this, and to reignite the spark plug to ensure ignition of the fuel.

  2. Description of the Related Art Conventionally, a method is known in which a combustion pressure sensor for detecting pressure (combustion pressure) in a combustion chamber is provided in an internal combustion engine, and this is used to detect poor ignition of fuel. For example, in Patent Document 1, as the amount of recirculated exhaust gas supplied into the combustion chamber increases, the amount of soot generated gradually increases and reaches a peak, and the amount of recirculated exhaust gas supplied into the combustion chamber. Is increased, the temperature of the fuel in the combustion chamber and the gas surrounding it is lower than the generation temperature of soot, and soot is hardly generated, and the combustion pressure sensor is recirculated. It is placed only in the combustion chamber of the cylinder with the largest amount of exhaust gas, and the amount of recirculated exhaust gas supplied to the combustion chamber is larger than the amount of recirculated exhaust gas at which the amount of soot generation peaks, and soot is almost generated A technique is disclosed in which the air-fuel ratios of all the cylinders are controlled in accordance with the output value of the combustion pressure sensor when non-combustion is performed.

JP 2000-130224 A

  In the conventional technology such as the internal combustion engine described in Patent Document 1, it is necessary to provide a combustion pressure sensor in order to detect the combustion pressure, and there is room for improvement in terms of cost reduction.

  Therefore, the present invention has been made paying attention to the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that does not require a combustion pressure sensor and can reduce the cost as compared with the prior art.

  An internal combustion engine control apparatus according to the present invention includes an ignition control unit that controls energization of an ignition coil that supplies electric energy to an ignition plug that discharges in a cylinder of the internal combustion engine and ignites fuel, and an electrode of the ignition plug A discharge amount detection unit that detects a voltage between them, and an in-cylinder pressure calculation unit that calculates a pressure in the cylinder based on the voltage between the electrodes detected by the discharge amount detection unit.

  According to the present invention, it is possible to provide a control device for an internal combustion engine that does not require a combustion pressure sensor and is capable of reducing the cost as compared with the prior art.

It is a figure explaining the principal part structure of the internal combustion engine concerning embodiment and the control apparatus of an internal combustion engine. It is the elements on larger scale explaining an ignition plug. It is a functional block diagram explaining the functional structure of a control apparatus. It is a figure explaining the electric circuit containing an ignition coil. It is an example of the timing chart explaining the switching timing of a switch, and the voltage change of a secondary side coil. It is a figure explaining an example of the cylinder pressure detection method concerning an embodiment. It is an example of the flowchart explaining the control method of the ignition plug by the ignition control part concerning embodiment.

  Hereinafter, a control device for an internal combustion engine according to an embodiment of the present invention will be described.

Hereinafter, the control apparatus 1 which is one aspect | mode of the control apparatus for internal combustion engines concerning embodiment is demonstrated. In this embodiment, a case where the control device 1 controls the discharge (ignition) of the spark plug 200 provided in each cylinder 150 of the four-cylinder internal combustion engine 100 will be described as an example.
Hereinafter, in the embodiment, a part or all of the configuration of the internal combustion engine 100 and a part or all of the configuration of the control device 1 are referred to as the control device 1 of the internal combustion engine 100.

[Internal combustion engine]
FIG. 1 is a diagram for explaining a main configuration of an internal combustion engine 100 and an internal combustion engine ignition device.
FIG. 2 is a partially enlarged view for explaining the electrodes 210 and 220 of the spark plug 200.

  In the internal combustion engine 100, air sucked from the outside flows through the air cleaner 110, the intake pipe 111, and the intake manifold 112, and flows into each cylinder 150 when the intake valve 151 is opened. The amount of air flowing into each cylinder 150 is adjusted by the throttle valve 113, and the amount of air adjusted by the throttle valve 113 is measured by the flow sensor 114.

  The throttle valve 113 is provided with a throttle opening sensor 113a for detecting the throttle opening. The opening information of the throttle valve 113 detected by the throttle opening sensor 113a is output to a control device (Electronic Control Unit: ECU) 1.

  As the throttle valve 113, an electronic throttle valve driven by an electric motor is used. However, any other system may be used as long as the air flow rate can be adjusted appropriately.

  The temperature of the gas flowing into each cylinder 150 is detected by the intake air temperature sensor 115.

  A crank angle sensor 121 is provided on the radially outer side of the ring gear 120 attached to the crankshaft 123. The crank angle sensor 121 detects the rotation angle of the crankshaft 123. In the embodiment, the crank angle sensor 121 detects the rotation angle of the crankshaft 123 every 10 ° and every combustion cycle, for example.

  A water temperature sensor 122 is provided in a water jacket (not shown) of the cylinder head. This water temperature sensor 122 detects the temperature of the cooling water of the internal combustion engine 100.

  The vehicle is also provided with an accelerator position sensor (APS) 126 that detects the displacement (depression amount) of the accelerator pedal 125. The accelerator position sensor 126 detects the driver's required torque. The driver's required torque detected by the accelerator position sensor 126 is output to the control device 1 described later. The control device 1 controls the throttle valve 113 based on this required torque.

  The fuel stored in the fuel tank 130 is sucked and pressurized by the fuel pump 131, flows through the fuel pipe 133 provided with the pressure regulator 132, and is guided to the fuel injection valve (injector) 134. The fuel output from the fuel pump 131 is adjusted to a predetermined pressure by the pressure regulator 132 and is injected into each cylinder 150 from a fuel injection valve (injector) 134. As a result of the pressure adjustment by the pressure regulator 132, excess fuel is returned to the fuel tank 130 via a return pipe (not shown).

  Each cylinder 150 is provided with an exhaust valve 152 and an exhaust manifold 160 that discharges the burned gas (exhaust gas) to the outside of the cylinder 150. A three-way catalyst 161 is provided on the exhaust side of the exhaust manifold 160. When the exhaust valve 152 is opened, exhaust gas is discharged from the cylinder 150 to the exhaust manifold 160. The exhaust gas is purified by the three-way catalyst 161 through the exhaust manifold 160 and then discharged to the atmosphere.

  An upstream air-fuel ratio sensor 162 is provided on the upstream side of the three-way catalyst 161. The upstream air-fuel ratio sensor 162 continuously detects the air-fuel ratio of the exhaust gas discharged from each cylinder 150.

  A downstream air-fuel ratio sensor 163 is provided downstream of the three-way catalyst 161. This downstream air-fuel ratio sensor 163 outputs a switch-like detection signal in the vicinity of the theoretical air-fuel ratio. In the embodiment, the downstream air-fuel ratio sensor 163 is, for example, an O2 sensor.

  A spark plug 200 is provided above each cylinder 150. Due to the discharge (ignition) of the spark plug 200, a spark is ignited in the air-fuel mixture in the cylinder 150, an explosion occurs in the cylinder 150, and the piston 170 is pushed down. When the piston 170 is pushed down, the crankshaft 123 rotates.

  An ignition coil 300 that generates electrical energy (voltage) supplied to the spark plug 200 is connected to the spark plug 200. That is, one ignition coil 300 is provided for each of the plurality of cylinders 150 (four in the embodiment) of the internal combustion engine 100. Due to the voltage generated in the ignition coil 300, a discharge occurs between the center electrode 210 and the outer electrode 220 of the spark plug 200 (see FIG. 2).

  As shown in FIG. 2, in the spark plug 200, the center electrode 210 is supported in an insulated state by an insulator 230. A predetermined voltage (in the embodiment, for example, 20,000 V to 40,000 V) is applied to the center electrode 210.

  The outer electrode 220 is grounded. When a predetermined voltage is applied to the center electrode 210, discharge (ignition) occurs between the center electrode 210 and the outer electrode 220.

  In the spark plug 200, the voltage at which discharge (ignition) occurs due to dielectric breakdown of the gas component varies depending on the state of gas (gas) existing between the center electrode 210 and the outer electrode 220 and the in-cylinder pressure. . The voltage at which this discharge occurs is called the dielectric breakdown voltage.

  The discharge control (ignition control) of the spark plug 200 is performed by an ignition control unit 83 of the control device 1 described later.

  Returning to FIG. 1, output signals from various sensors such as the throttle opening sensor 113 a, the flow sensor 114, the crank angle sensor 121, the accelerator position sensor 126, and the water temperature sensor 122 described above are output to the control device 1. The control device 1 detects the operating state of the internal combustion engine 100 based on output signals from these various sensors, and controls the amount of air sent into the cylinder 150, the fuel injection amount, the ignition timing of the spark plug 200, and the like. .

  In a conventional conventional internal combustion engine, a combustion pressure sensor configured using a piezoelectric or gauge pressure sensor is provided in the cylinder in order to detect the pressure (combustion pressure) in the cylinder. . However, such a combustion pressure sensor is not provided in the internal combustion engine 100 to be controlled by the control device 1. Therefore, in the control device 1 according to the embodiment, the spark plug 200 is in a discharge state even after combustion of the air-fuel mixture by generating a discharge a plurality of times between the center electrode 210 and the outer electrode 220 of the spark plug 200. Like that. At this time, the voltage (interelectrode voltage) between the center electrode 210 and the outer electrode 220 is detected, and the pressure in the cylinder 150 is detected by a method described later based on the detection result. As a result, a control device for an internal combustion engine that can detect the pressure in the cylinder 150 without requiring a combustion pressure sensor is realized.

[Hardware configuration of control device]
Next, the overall hardware configuration of the control device 1 will be described.

  As shown in FIG. 1, the control device 1 includes an analog input unit 10, a digital input unit 20, an A / D (Analog / Digital) conversion unit 30, a RAM (Random Access Memory) 40, an MPU (Micro-). It includes a processing unit (ROM) 50, a read only memory (ROM) 60, an input / output (I / O) port 70, and an output circuit 80.

  The analog input unit 10 includes analog output signals from various sensors such as a throttle opening sensor 113a, a flow sensor 114, an accelerator position sensor 126, an upstream air-fuel ratio sensor 162, a downstream air-fuel ratio sensor 163, a water temperature sensor 122, and the like. The voltage between the electrodes of the spark plug 200 is input.

  An A / D conversion unit 30 is connected to the analog input unit 10. The analog output signals from various sensors input to the analog input unit 10 and the voltage between the electrodes of the spark plug 200 are converted into digital signals by the A / D conversion unit 30 after signal processing such as noise removal is performed. It is stored in the RAM 40.

  A digital output signal from the crank angle sensor 121 is input to the digital input unit 20.

  An I / O port 70 is connected to the digital input unit 20, and a digital output signal input to the digital input unit 20 is stored in the RAM 40 via the I / O port 70.

  Each output signal stored in the RAM 40 is processed by the MPU 50.

  The MPU 50 executes a control program (not shown) stored in the ROM 60, and calculates the output signal stored in the RAM 40 according to the control program. The MPU 50 calculates a control value that defines the operation amount of each actuator (for example, the throttle valve 113, the pressure regulator 132, the spark plug 200, etc.) that drives the internal combustion engine 100 according to the control program, and temporarily stores it in the RAM 40. .

  A control value that defines the operation amount of the actuator stored in the RAM 40 is output to the output circuit 80 via the I / O port 70.

  The output circuit 80 is provided with a function of an ignition control unit 83 (see FIG. 3) that controls a voltage applied to the spark plug 200.

[Function block of control device]
Next, the functional configuration of the control device 1 will be described.

  FIG. 3 is a functional block diagram illustrating a functional configuration of the control device 1. Each function of the control device 1 is realized by the output circuit 80, for example, when the MPU 50 executes a control program stored in the ROM 60.

  As shown in FIG. 3, the output circuit 80 of the control device 1 includes an overall control unit 81, a fuel injection control unit 82, and an ignition control unit 83.

  The overall control unit 81 is connected to the accelerator position sensor 126 and the in-cylinder pressure calculation unit 90 that calculates the pressure in each cylinder 150 of the internal combustion engine 100, and the required torque (acceleration signal S1) from the accelerator position sensor 126 is connected. ) And in-cylinder pressure information S2 from the in-cylinder pressure calculation unit 90. The in-cylinder pressure calculation unit 90 inputs the voltage between the electrodes of the spark plug 200 detected by the discharge amount detection unit 360 (see FIG. 4) connected to the spark plug 200, and each cylinder 150 is based on the voltage between the electrodes. It has a function to calculate the internal pressure. The in-cylinder pressure calculation unit 90 is similar to the overall control unit 81, the fuel injection control unit 82, the ignition control unit 83, and the like. The MPU 50 executes a control program stored in the ROM 60, so that the output circuit 80 in the control device 1 is executed. It is realized with.

  The overall control unit 81 performs overall operations of the fuel injection control unit 82 and the ignition control unit 83 based on the required torque (acceleration signal S1) from the accelerator position sensor 126 and the in-cylinder pressure information S2 from the in-cylinder pressure calculation unit 90. Control.

  The fuel injection control unit 82 includes a cylinder discrimination unit 84 that discriminates each cylinder 150 of the internal combustion engine 100, an angle information generation unit 85 that measures the crank angle of the crankshaft 123, and a rotation speed information generation unit that measures the engine speed. 86, the cylinder discrimination information S3 from the cylinder discrimination unit 84, the crank angle information S4 from the angle information generation unit 85, and the engine rotation speed information S5 from the rotation speed information generation unit 86. Accept.

  Further, the fuel injection control unit 82 measures the intake air amount measurement unit 87 that measures the intake air amount of the air taken into the cylinder 150, the load information generation unit 88 that measures the engine load, and the temperature of the engine coolant. The intake air amount information S6 from the intake air amount measurement unit 87, the engine load information S7 from the load information generation unit 88, and the cooling water temperature information S8 from the water temperature measurement unit 89 are connected to the water temperature measurement unit 89. , Is accepted.

  The fuel injection control unit 82 calculates the injection amount and injection time (fuel injection valve control information S9) of the fuel injected from the fuel injection valve 134 based on each received information, and calculates the calculated fuel injection amount and injection. The fuel injection valve 134 is controlled based on the time.

  In addition to the overall control unit 81, the ignition control unit 83 includes a cylinder determination unit 84, an angle information generation unit 85, a rotation speed information generation unit 86, a load information generation unit 88, a water temperature measurement unit 89, and an in-cylinder pressure calculation. It is connected to the unit 90 and receives each information from these.

  Based on the received information, the ignition control unit 83 energizes the primary side coil (not shown) of the ignition coil 300, the energization start time, and the primary side coil. The time (ignition time) for interrupting the current is calculated.

  The ignition control unit 83 outputs an ignition signal SA to the primary side coil 310 of the ignition coil 300 based on the calculated energization angle, energization start time, and ignition time, thereby performing discharge control ( Ignition control). The ignition coil 300 may be configured by combining a plurality of coils.

  Note that at least the function of the ignition control unit 83 performing the ignition control of the spark plug 200 using the ignition signal SA corresponds to the control device for an internal combustion engine of the present invention.

[Electric circuit of ignition coil]
Next, the electric circuit 400 including the ignition coil 300 will be described.

  FIG. 4 is a diagram illustrating an electric circuit 400 including the ignition coil 300. In the electric circuit 400, the ignition coil 300 includes a primary side coil 310 wound with a predetermined number of turns and a secondary side coil 320 wound with more turns than the primary side coil 310. Is done.

  One end of the primary coil 310 is connected to the DC power supply 330. Thus, a predetermined voltage (for example, 12 V in the embodiment) is applied to the primary coil 310. A charge amount detection unit 350 is provided in the connection path between the DC power supply 330 and the primary coil 310. The charge amount detection unit 350 detects the voltage and current applied to the primary side coil 310 and transmits them to the ignition control unit 83.

  The other end of the primary coil 310 is connected to the igniter 340 and is grounded via the igniter 340. For the igniter 340, a transistor, a field effect transistor (FET), or the like is used.

  The base (B) terminal of the igniter 340 is connected to the ignition control unit 83 via the gate resistance Rg and the switch SW. The ignition signal SA output from the ignition control unit 83 is input to the base (B) terminal of the igniter 340 via the gate resistance Rg or the switch SW. When the ignition signal SA input to the base (B) terminal of the igniter 340 is turned ON, the collector (C) terminal and emitter (E) terminal of the igniter 340 are energized, and the collector (C) terminal and emitter (E) Current flows between the terminals. As a result, an ignition signal SA is output from the ignition control unit 83 to the primary coil 310 of the ignition coil 300 via the igniter 340, the ignition coil 300 is energized, and electric power (electric energy) is accumulated in the primary coil 310. Is done.

  When the output of the ignition signal SA from the ignition control unit 83 changes from ON to OFF and the current flowing through the primary coil 310 is interrupted, a high voltage corresponding to the coil turns ratio with respect to the primary coil 310 Is generated in the secondary coil 320. When the high voltage generated in the secondary coil 320 is applied to the spark plug 200 (center electrode 210), a potential difference is generated between the center electrode 210 of the spark plug 200 and the outer electrode 220. When the potential difference generated between the center electrode 210 and the outer electrode 220 becomes equal to or higher than the dielectric breakdown voltage Vm of the gas (air-fuel mixture in the cylinder 150), the gas component is dielectrically broken, and the center electrode 210 and the outer electrode 220 During this time, discharge occurs and ignition (ignition) of the fuel (air mixture) is performed.

  The ignition control unit 83 outputs the ignition signal SA as described above to the igniter 340, thereby controlling the supply of electric energy from the ignition coil 300 to the spark plug 200, and discharging the spark plug 200 to ignite the fuel. To be done.

  The ignition control unit 83 outputs an ignition signal SA for detecting the pressure in the cylinder 150 even after the fuel is ignited. However, since it is not necessary to ignite the fuel when detecting the pressure in the cylinder 150, the voltage generated in the secondary coil 320 is lowered compared with the time of ignition, and the consumption of the spark plug 200 is suppressed. It is preferable. Therefore, the ignition signal SA output from the ignition control unit 83 after ignition of the fuel has a shorter period (pulse width) from ON to OFF than the ignition signal SA output at the time of ignition described above.

  Hereinafter, the ignition signal SA output from the ignition control unit 83 at the time of ignition is referred to as “ignition ignition signal”, and the electric energy supplied from the ignition coil 300 to the ignition plug 200 at this time is referred to as “ignition electric energy”. say. That is, the ignition electrical energy is electrical energy for igniting the fuel by the discharge of the spark plug 200, and the ignition ignition signal is supplied from the ignition coil 300 to the spark plug 200. It is a signal to make it. On the other hand, the ignition signal SA output from the ignition control unit 83 when the pressure in the cylinder 150 is detected is referred to as a “detection ignition signal”, and the electrical energy supplied from the ignition coil 300 to the ignition plug 200 at this time is referred to as “detection ignition signal”. Say “electric energy”. That is, the electric energy for detection is electric energy for generating a voltage according to the pressure in the cylinder 150 between the electrodes of the spark plug 200, and the electric signal for detection is the electric energy for detection. This is a signal for supplying the spark plug 200 from 300.

  The ignition controller 83 controls the switching state of the switch SW by outputting a switching signal W to the switch SW. The switch SW switches the connection state of the gate resistance Rg between the ignition control unit 83 and the igniter 340 in accordance with the switching signal W from the ignition control unit 83. When the switching signal W is ON, the switch SW is switched to the conduction side, and both ends of the gate resistance Rg are short-circuited. At this time, the ignition signal SA output from the ignition control unit 83 is input to the igniter 340 without passing through the gate resistance Rg. On the other hand, when the switching signal W is OFF, the switch SW is switched to the cutoff side. At this time, the ignition signal SA output from the ignition control unit 83 is input to the igniter 340 via the gate resistance Rg. For example, a field effect transistor (FET) is used as the switch SW.

  FIG. 5 is an example of a timing chart for explaining the switching timing of the switch SW according to the ignition signal SA and the voltage change of the secondary coil 320. In FIG. 5, the uppermost row shows ON / OFF of the ignition signal SA output from the ignition control unit 83. The second row from the top indicates ON / OFF of the switching signal W. According to ON / OFF of the switching signal W, the switch SW is switched to the ON side (connection side) or the OFF side (blocking side). The third stage from the top shows the current waveform flowing in the primary coil 310 of the ignition coil 300, and the bottom stage shows the voltage waveform generated in the secondary coil 320 of the ignition coil 300.

  As shown in the uppermost stage of FIG. 5, the ignition control unit 83 outputs an ignition ignition signal having a large pulse width as the ignition signal SA, and thereafter outputs a detection ignition signal having a small pulse width. Further, as shown in the second stage from the top in FIG. 5, the switching signal W is turned off in a period including the timing when the ignition ignition signal is turned off, and the switching signal W is turned on in other periods. Thus, when the ignition coil 300 supplies ignition electric energy to the ignition plug 200, the ignition ignition signal output from the ignition control unit 83 is input to the igniter 340 via the gate resistance Rg, and the ignition coil 300 is ignited. When supplying electric energy for detection to the plug 200, the switch SW is switched so that the detection ignition signal output from the ignition control unit 83 is input to the igniter 340 without passing through the gate resistance Rg.

  By the switching control of the switch SW as described above, as shown in the third stage from the top in FIG. 5, the current flowing through the primary side coil 310 of the ignition coil 300 slowly decreases in accordance with the ignition ignition signal. As a result, as shown in the lowermost stage of FIG. 5, the discharge of the spark plug 200 can be maintained for a long period of time by smoothing the fall of the voltage waveform generated in the secondary coil 320 when the fuel is ignited. . On the other hand, the current flowing through the primary coil 310 of the ignition coil 300 is quickly reduced in response to the detection ignition signal. Thereby, when detecting the pressure in the cylinder 150, the discharge of the spark plug 200 can be completed in a short time.

  Returning to FIG. 4, a discharge amount detection unit 360 is provided in the connection path between the secondary coil 320 and the spark plug 200. The discharge amount detection unit 360 detects the voltage (discharge voltage) and current between the electrodes of the spark plug 200 during discharge.

  Electrical circuit 400 further includes a peak hold unit 370 connected to discharge amount detection unit 360. The interelectrode voltage (discharge voltage) of the spark plug 200 detected by the discharge amount detection unit 360 is input to the peak hold unit 370. The peak hold unit 370 performs a peak hold operation that maintains the peak value of the interelectrode voltage detected by the discharge amount detection unit 360 for a predetermined time so that the A / D conversion unit 30 (see FIG. 1) can acquire it as a digital signal. . For example, the peak hold unit 370 maintains the peak value of the interelectrode voltage detected by the discharge amount detection unit 360 until the next detection ignition signal is output. The voltage between the electrodes of the spark plug 200 output from the peak hold unit 370 is taken into the control device 1 as a digital signal by the A / D conversion unit 30 and output to the in-cylinder pressure calculation unit 90.

  The in-cylinder pressure calculation unit 90 acquires the inter-electrode voltage maintained by the peak hold unit 370, and uses this to calculate the pressure in the cylinder 150. Then, the calculation result is output to the ignition control unit 83 as in-cylinder pressure information S2.

  The ignition control unit 83 controls energization of the ignition coil 300 using the ignition signal SA by the operation of the electric circuit 400 as described above. Thereby, the electric energy given from the ignition coil 300 to the spark plug 200 is controlled, and ignition control for realizing ignition of the fuel and pressure detection in the cylinder 150 is performed.

[Outline of cylinder pressure detection]
Next, an outline of pressure detection in the cylinder 150 according to the embodiment will be described.

  FIG. 6 is a diagram for explaining an example of the in-cylinder pressure detection method according to the embodiment of the present invention. 6A shows an example of a temporal change in the pressure in the cylinder 150 (in-cylinder pressure), and FIG. 6B shows an example of a timing chart of each signal waveform in the control device 1 and the electric circuit 400. Show.

  In FIG. 6A, reference numeral 601 indicates the in-cylinder pressure change at the time of ignition. When the fuel is normally ignited by the ignition for ignition, the in-cylinder pressure increases due to the combustion pressure, and then decreases. On the other hand, reference numeral 602 indicates the in-cylinder pressure change at the time of misfire. At the time of misfire in which the fuel is not normally ignited by ignition for ignition, the in-cylinder pressure gradually increases and decreases with the top dead center (TDC) as a peak.

  In FIG. 6B, reference numeral 603 indicates the ignition signal SA. In the ignition signal SA, after an ignition ignition signal having a long pulse width is output, a detection ignition signal having a short pulse width is output at a constant cycle. Reference numeral 604 indicates the primary side voltage of the ignition coil 300, that is, the voltage of the primary side coil 310, which changes according to the output of the ignition signal SA. Reference numeral 605 indicates an integrated value of the electric power supplied to the ignition coil 300, and continues to increase every time the ignition signal SA is output until a predetermined upper limit value (for example, 140 mJ) is reached.

  Reference numeral 606 denotes a switching signal W output from the ignition control unit 83 to the switch SW. As described with reference to FIG. 5, the switching signal W is turned off in a period including the timing when the ignition ignition signal is turned off, and is turned on in other periods. Reference numeral 607 indicates a voltage that can be output from the ignition coil 300. When the ignition ignition signal is output, the voltage changes greatly in order to discharge the plug 200 at a high voltage for a long time. When the detection ignition signal is output, the plug 200 is output at a low voltage. In order to discharge for a short time, the change is small.

  Reference numeral 608 indicates the secondary side voltage of the ignition coil 300, that is, the voltage of the secondary side coil 320, and changes in a pulse form in synchronization with the output possible voltage of the ignition coil 300 indicated by reference numeral 607. The height of each pulse at this time is determined by the dielectric breakdown voltage Vm, which changes according to the pressure in the cylinder 150 (in-cylinder pressure). Reference numeral 609 denotes a peak hold voltage output from the peak hold unit 370, that is, a peak value of the interelectrode voltage of the spark plug 200. The peak hold voltage is reset in synchronization with the output of the ignition signal SA, and then changes in accordance with the height of each pulse of the secondary voltage.

Reference numeral 610 indicates an in-cylinder pressure, that is, an estimated value of the pressure in the cylinder 150. The estimated value of the in-cylinder pressure changes according to the peak hold voltage except during reset. Specifically, for example, the estimated value of the in-cylinder pressure is obtained from the voltage between the electrodes of the spark plug 200 indicated by the peak hold voltage by the following equation (1). Equation (1) is an equation representing the relationship between the in-cylinder pressure during discharge and the voltage between electrodes according to Paschen's law. In Formula (1), Vs represents the interelectrode voltage during discharge, p represents the in-cylinder pressure, d represents the interelectrode distance, and A, B, and C represent constants, respectively.
Vs = Bpd / {ln (Apd) + C} (1)

[Control method of spark plug]
Next, an example of a method for controlling the spark plug 200 by the ignition control unit 83 will be described. FIG. 7 is an example of a flowchart for explaining a control method of the spark plug 200 by the ignition control unit 83 according to the embodiment.

  As shown in FIG. 7, in step S <b> 101, the ignition control unit 83 charges the engine speed indicated by the engine speed information S <b> 5 from the speed information generation unit 86 and the charging of the ignition coil 300 detected by the charge amount detection unit 350. Based on the voltage, the target charge amount of the ignition coil 300 is set. For example, by referring to the map information stored in the ROM 60 in the control device 1, it is possible to set the target charge amount according to the engine speed and the charge voltage.

  In step S102, the ignition control unit 83 outputs an ignition ignition signal. At this time, the ignition control unit 83 sets the pulse width of the ignition signal SA based on the target charge amount set in step S101, and outputs the ignition signal SA corresponding to the pulse width to the igniter 340 as an ignition signal for ignition. When the ignition ignition signal is turned off, the switch SW is switched so that the ignition signal is input to the igniter 340 via the gate resistance Rg by turning off the switching signal W as described above. Thereby, electric energy for ignition is supplied from the ignition coil 300 to the spark plug 200, and the energization of the ignition coil 300 is controlled so that a discharge is generated between the electrodes of the spark plug 200 and the fuel is ignited.

  In step S103, the ignition control unit 83 determines whether or not a detection ignition signal can be output. At this time, the ignition control unit 83 determines the output timing of the ignition signal for the next combustion stroke based on, for example, the engine speed indicated by the engine speed information S5 from the speed information generating unit 86, and the output timing thereof. And the output cycle of the detection ignition signal are compared. As a result, if the output cycle of the detection ignition signal is shorter, it is determined that the detection ignition signal can be output (step S103: YES), and the process proceeds to step S104. On the other hand, if the output cycle of the detection ignition signal is longer, since the output of the ignition ignition signal for the next combustion stroke is approaching, it is determined that the detection ignition signal cannot be output (step S103: NO). Then, the processing flow of FIG. In this case, the processing flow of FIG. 7 is executed again for the next combustion stroke, and the ignition signal for ignition is output.

  By performing the processing of step S103 described above, the ignition control unit 83 causes the cylinder 150 per one ignition of fuel performed by the in-cylinder pressure calculation unit 90 in step S106 described later according to the rotational speed of the internal combustion engine 100. The number of calculations of the pressure can be changed.

  In step S104, the ignition control unit 83 outputs a detection ignition signal. At this time, the ignition control unit 83 sets the pulse width of the ignition signal SA with a predetermined length shorter than the ignition ignition signal, and outputs the ignition signal SA corresponding to the pulse width to the igniter 340 as a detection ignition signal. . Note that the pulse width of the detection ignition signal is assumed to be the distance between the electrodes so that the voltage applied between the electrodes of the spark plug 200 by the corresponding detection electric energy is at least the dielectric breakdown voltage Vm. It is preset according to the range of the in-cylinder pressure. Furthermore, the pulse width of the detection ignition signal may be changed based on the amount of air sent into the cylinder 150, the fuel injection amount, or the like. When the detection ignition signal is output, the switch SW is switched so that the detection ignition signal is input to the igniter 340 without passing through the gate resistance Rg by turning on the switching signal W as described above. Thereby, electric energy for detection is supplied from the ignition coil 300 to the ignition plug 200, and energization of the ignition coil 300 is controlled so that a discharge is generated between the electrodes of the ignition plug 200 with a discharge voltage corresponding to the in-cylinder pressure.

  In step S105, the in-cylinder pressure calculation unit 90 calculates the inter-electrode voltage detected by the discharge amount detection unit 360 when the spark plug 200 is discharged according to the detection ignition signal output from the ignition control unit 83 in step S104. A corresponding peak hold voltage is acquired from the peak hold unit 370.

  In step S106, the in-cylinder pressure calculation unit 90 calculates the in-cylinder pressure that is the pressure in the cylinder 150 based on the peak hold voltage acquired in step S105. At this time, the in-cylinder pressure calculation unit 90 applies the inter-electrode voltage Vs at the time of discharge acquired as the peak hold voltage and the preset inter-electrode distance d to the above equation (1), The in-cylinder pressure p can be calculated. The relationship between the in-cylinder pressure p and the interelectrode voltage Vs corresponding to the equation (1) may be stored in advance in the ROM 60 as map information, and the in-cylinder pressure p may be calculated by referring to this map information. If the in-cylinder pressure can be calculated in step S106, the in-cylinder pressure calculation unit 90 outputs the calculation result to the ignition control unit 83 as in-cylinder pressure information S2.

  In step S107, the in-cylinder pressure calculation unit 90 determines whether or not the fuel is ignited by the ignition signal output in step S102 based on the in-cylinder pressure calculated by the in-cylinder pressure calculation unit 90 in step S106. Here, as shown in FIG. 6A, there is a significant difference between the in-cylinder pressure at the time of ignition and the in-cylinder pressure at the time of misfire depending on the presence or absence of the combustion pressure. Therefore, for example, the in-cylinder pressure calculation unit 90 can compare the in-cylinder pressure with a predetermined threshold value, and can determine ignition if the in-cylinder pressure is equal to or higher than the threshold value and misfire if the in-cylinder pressure is less than the threshold value. Note that the threshold used for this determination may be changed according to the elapsed time since the ignition signal was output. In addition to this, as long as the success or failure of ignition can be appropriately determined based on the in-cylinder pressure, the determination in step S107 can be performed using any method.

  If it is determined in step S107 that the ignition has succeeded (step S107: YES), the process returns to step S103 and continues to output the detection ignition signal as much as possible. On the other hand, if it is determined in step S107 that ignition has failed (misfire) (step S107: YES), the process proceeds to step S108.

  In step S108, the ignition control unit 83 determines whether or not the ignition ignition signal can be re-output. At this time, the ignition control unit 83 determines the output timing of the ignition signal for the next combustion stroke based on, for example, the engine speed indicated by the engine speed information S5 from the speed information generating unit 86, and at step S101. The required charging time of the ignition coil 300 is calculated on the basis of the target charge amount set in step 1. Then, the time until the output timing of the ignition signal for the next combustion stroke is compared with the charging time of the ignition coil 300. As a result, if the charging time of the ignition coil 300 is shorter, it is determined that the ignition ignition signal can be re-output (step S108: YES), and the process returns to step S102 to re-output the ignition ignition signal (step S102). . On the other hand, if the charging time of the ignition coil 300 is longer, it is determined that the ignition ignition signal cannot be output again (step S108: NO), and the processing flow of FIG. In this case, as in the case where a negative determination is made in step S103 described above, the processing flow of FIG. 7 is executed again for the next combustion stroke, and an ignition signal for ignition is output.

  By performing the processing of steps S107 and S108 described above, the ignition control unit 83 determines whether or not the fuel has been ignited based on the pressure in the cylinder 150 calculated by the in-cylinder pressure calculation unit 90, and the ignition to the fuel is performed. When it is determined that the ignition has failed, the ignition signal for ignition can be re-output within a possible range.

  According to the embodiment described above, the following operational effects are obtained.

(1) The control device 1 for the internal combustion engine controls the energization of the ignition coil 300 that supplies electric energy to the spark plug 200 that discharges in the cylinder 150 of the internal combustion engine 100 and ignites the fuel. A discharge amount detection unit 360 that detects the voltage between the electrodes of the spark plug 200, and an in-cylinder pressure calculation unit 90 that calculates the pressure in the cylinder 150 based on the voltage between the electrodes detected by the discharge amount detection unit 360. Is provided. Since it did in this way, the control apparatus for internal combustion engines which does not require a combustion pressure sensor and can reduce cost more than before can be provided.

(2) The control device 1 includes a peak hold unit 370 that maintains the voltage between the electrodes detected by the discharge amount detection unit 360 for a predetermined time. The in-cylinder pressure calculation unit 90 acquires the voltage between the electrodes maintained by the peak hold unit 370 (step S105), and calculates the pressure in the cylinder 150 (step S106). Since it did in this way, even when the voltage between the electrodes detected by the discharge amount detection part 360 is not stabilized, the pressure in the cylinder 150 can be calculated accurately.

(3) The ignition control unit 83 generates an ignition ignition signal for supplying ignition electric energy for igniting the fuel by the discharge of the ignition plug 200 from the ignition coil 300 to the ignition plug 200, and the pressure in the cylinder 150. A detection ignition signal for supplying a detection electric energy for generating a corresponding voltage between the electrodes of the ignition plug 200 to the ignition coil 300 or the ignition plug 200 is output (steps S102 and S104). The in-cylinder pressure calculation unit 90 calculates the pressure in the cylinder 150 based on the voltage between the electrodes detected by the discharge amount detection unit 360 when the ignition control unit 83 outputs a detection ignition signal (steps S105 and S106). ). Since it did in this way, it becomes possible to calculate the pressure in the cylinder 150 after combustion.

(4) The ignition coil 300 is connected to an igniter 340 that receives the ignition ignition signal and the detection ignition signal output from the ignition control unit 83 and energizes the ignition coil 300. Between the ignition control unit 83 and the igniter 340, a gate resistance Rg and a switch SW for switching a connection state of the gate resistance Rg are provided. As described with reference to FIG. 5, when the ignition coil 300 supplies ignition electric energy to the spark plug 200, the ignition control unit 83 inputs the ignition ignition signal to the igniter 340 via the gate resistance Rg. Switches the switch SW so that the detection ignition signal is input to the igniter 340 without passing through the gate resistor Rg when the electric energy for detection is supplied to the spark plug 200. Thus, the discharge of the spark plug 200 can be maintained for a long time when the fuel is ignited, and the discharge of the spark plug 200 can be completed in a short time when the pressure in the cylinder 150 is detected. Therefore, it is possible to set optimum discharge times for ignition and for detecting in-cylinder pressure.

(5) The ignition control unit 83 determines the success or failure of ignition of the fuel based on the pressure in the cylinder 150 calculated by the in-cylinder pressure calculation unit 90 (step S107), and determines that the ignition of the fuel has failed (Step S107: NO) The ignition signal for ignition is output again (Step S108: YES, Step S102). Since it did in this way, ignitability can be improved.

(6) The in-cylinder pressure calculation unit 90 changes the number of times of calculation of the pressure in the cylinder 150 per one ignition of fuel according to the rotational speed of the internal combustion engine 100 (step S103). Since it did in this way, even if the rotation speed of the internal combustion engine 100 changes, the pressure in the cylinder 150 can be calculated | required by the optimal frequency | count of calculation for every rotation speed.

  In the embodiment described above, each functional configuration of the control device 1 described with reference to FIG. 3 may be realized by software executed by the MPU 50 as described above, or an FPGA (Field-Programmable Gate Array). ) Or the like. These may be used in combination.

  The embodiment and various modifications described above are merely examples, and the present invention is not limited to these contents as long as the features of the invention are not impaired. Moreover, although various embodiment and the modification were demonstrated above, this invention is not limited to these content. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

  1: control device, 10: analog input unit, 20: digital input unit, 30: A / D conversion unit, 40: RAM, 50: MPU, 60: ROM, 70: I / O port, 80: output circuit, 81 : Overall control unit, 82: Fuel injection control unit, 83: Ignition control unit, 84: Cylinder discrimination unit, 85: Angle information generation unit, 86: Revolution information generation unit, 87: Intake amount measurement unit, 88: Load information Generator: 89: Water temperature measurement unit, 90: In-cylinder pressure calculation unit, 100: Internal combustion engine, 110: Air cleaner, 111: Intake pipe, 112: Intake manifold, 113: Throttle valve, 113a: Throttle opening sensor, 114: Flow rate Sensor: 115: Intake air temperature sensor, 120: Ring gear, 121: Crank angle sensor, 122: Water temperature sensor, 123: Crankshaft, 125: Accelerator pedal, 126: Access Position sensor, 130: fuel tank, 131: fuel pump, 132: pressure regulator, 133: fuel piping, 134: fuel injection valve, 150: cylinder, 151: intake valve, 152: exhaust valve, 160: exhaust manifold, 161: Three-way catalyst, 162: upstream air-fuel ratio sensor, 163: downstream air-fuel ratio sensor, 170: piston, 200: spark plug, 210: center electrode, 220: outer electrode, 230: insulator, 300: ignition coil, 310 : Primary side coil, 320: secondary side coil, 330: DC power supply, 340: igniter, 350: charge amount detection unit, 360: discharge amount detection unit, 370: peak hold unit, 400: electric circuit

Claims (6)

An ignition control unit that controls energization of an ignition coil that gives electric energy to a spark plug that discharges in a cylinder of an internal combustion engine and ignites fuel;
A discharge amount detector for detecting a voltage between the electrodes of the spark plug;
A control apparatus for an internal combustion engine, comprising: an in-cylinder pressure calculation unit that calculates a pressure in the cylinder based on a voltage between the electrodes detected by the discharge amount detection unit. The control device for an internal combustion engine according to claim 1,
A peak hold unit for maintaining the voltage between the electrodes detected by the discharge amount detection unit for a predetermined time;
The in-cylinder pressure calculation unit is a control device for an internal combustion engine that acquires a voltage between the electrodes maintained by the peak hold unit and calculates a pressure in the cylinder. The control device for an internal combustion engine according to claim 1,
The ignition control unit is responsive to an ignition ignition signal for supplying an ignition electrical energy for igniting the fuel by discharge of the ignition plug from the ignition coil to a pressure in the cylinder. A detection ignition signal for supplying detection electric energy for generating a voltage between the electrodes of the ignition plug from the ignition coil to the ignition plug; and
The in-cylinder pressure calculation unit is for an internal combustion engine that calculates a pressure in the cylinder based on a voltage between the electrodes detected by the discharge amount detection unit when the ignition control unit outputs the detection ignition signal. Control device. The control device for an internal combustion engine according to claim 3,
The ignition coil is connected to an igniter that receives the ignition ignition signal and the detection ignition signal output from the ignition control unit and energizes the ignition coil;
Between the ignition control unit and the igniter, a gate resistor and a switch for switching a connection state of the gate resistor are provided,
The ignition control unit inputs the ignition ignition signal to the igniter via the gate resistor when the ignition coil supplies the ignition plug with the ignition electric energy, and the ignition coil is applied to the ignition plug. A control device for an internal combustion engine that switches the switch so that the detection ignition signal is input to the igniter without passing through the gate resistance when supplying electric energy for detection. The control device for an internal combustion engine according to claim 3,
The ignition control unit determines success or failure of ignition of the fuel based on the pressure in the cylinder calculated by the in-cylinder pressure calculation unit, and determines that the ignition of the fuel has failed, the ignition ignition A control device for an internal combustion engine that re-outputs a signal. The control device for an internal combustion engine according to claim 1,
The in-cylinder pressure calculation unit is an internal combustion engine control device that changes the number of times of calculation of the pressure in the cylinder per one ignition of the fuel in accordance with the rotational speed of the internal combustion engine.

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