JP2011117334A - Combustion control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustion control device of an internal combustion engine, which can cope with a request of reduction in fuel consumption of an automobile. <P>SOLUTION: The device includes a control unit for controlling a current supplying operation of a primary coil of an ignition coil, and a control map MP1 for defining a target value of a coil current supplying time period of the primary coil, depending on an operating condition of the internal combustion engine. The control unit ECU includes a determination means (ST13 to ST14) for determining the adequacy of a combustion state of air-fuel mixture during each ignition cycle, a combustion control means (ST18 and ST19) for executing a combustion operation of the subsequent ignition cycle so that a suitable combustion state can be achieved corresponding to the combustion state determined by the determination means, and a current supply control means (ST15, ST17 and ST11) for executing a current supply operation by specifying a target value TG in the subsequent ignition cycle, while referring to the control map MP1 based on the operating state, and for setting the coil current supplying time period so as to be below the target value when the determination means determined to be a non-suitable combustion state. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a combustion control device that optimally controls the coil energization time of an ignition coil to enhance the effect of reducing the fuel consumption of an automobile.

  In recent years, demands for reducing fuel consumption of automobiles are increasing. However, in the conventional automobile engine, the coil energization time of the ignition coil for igniting and discharging the spark plug is simply determined based on the engine speed and the battery voltage. And if the coil energization time is too short, the secondary output of the ignition coil will be insufficient and the combustion will deteriorate, so it is a reality to set the coil energization time long enough, specifically, the heat generation limit of the coil The maximum energization time specified from Therefore, the power consumption during this extra coil energization time is against the demand for fuel consumption reduction.

  Here, in order to appropriately respond to the demand for reduction in fuel consumption, it is extremely important to set the coil energization time optimally without deteriorating the combustion state during EGR control and lean burn control in addition to during normal operation. It is.

JP 2006-08397A JP 2008-121582 A

  However, an invention that meets such a demand is not known. In addition, although the combustion control method at the time of engine starting (patent document 1) and the combustion control method at the time of lean burn operation (patent document 2) are known, the coil energization time is not optimized.

  For example, in the invention of Patent Document 1, when starting the engine, the rotation time is calculated every time the crankshaft rotates by a predetermined angle, and the ignition start timing is determined while predicting the rotation time of the next predetermined angle section. It does not optimize the coil energization time.

  Also, in the invention of Patent Document 2, during lean burn operation, the torque fluctuation is suppressed by the ignition energy control in the normal time when the torque fluctuation is equal to or less than a predetermined value, but when the torque fluctuation exceeds the predetermined value, the ignition energy is maximized. The torque fluctuation is suppressed by air-fuel ratio control with the value fixed, and the coil energization time is not optimally controlled. As long as the air-fuel ratio control is adopted, the fuel injection amount increases at the time of deterioration of combustion, so that improvement in fuel consumption cannot be expected.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a combustion control device that can reliably respond to a request for reduction in fuel consumption of an automobile.

  In order to achieve the above object, in the present invention, an ignition coil in which a primary coil and a secondary coil are electromagnetically coupled, a control unit for controlling energization operation of the primary coil, and generated in the secondary coil when the energization of the primary coil is cut off. An ignition plug that ignites and discharges the air-fuel mixture based on the induced voltage, and a control map that defines a target value for the coil energization time of the primary coil for each operating state of the internal combustion engine, In the ignition unit, in each ignition cycle, determination means for determining the suitability of the combustion state of the air-fuel mixture, and the next time in order to realize a good combustion state corresponding to the combustion state determined by the determination means Combustion control means for executing the combustion operation of the ignition cycle, and the combustion state determined by the determination means by specifying the target value in the next ignition cycle with reference to the control map based on the operating state Non The good time, and is configured with a, energizing control means for performing the power supply operation by setting the coil energization time to below the target value.

  The target value at the time of steady operation is the upper limit value of the coil energization time specified for each operation state based on the heat generation limit of the ignition coil, and the coil energization time that can be discharged by the spark plug, specified for each operation state. It is preferable to be set between the lower limit value and the lower limit value. On the other hand, it is preferable that the target value during the transient operation is set to an upper limit value of the coil energization time defined for each operation state based on the heat generation limit of the ignition coil.

  Further, the target value in the steady operation is based on the upper limit value of the coil energization time specified for each operation state based on the heat generation limit of the ignition coil, and the optimum value of the coil energization time at which the fuel consumption rate becomes the minimum value. It is preferable to set between the two.

  The control map defined for each operation state of the internal combustion engine should preferably be provided with a control map for cold start, separately from the control map for steady operation. The suitability of the combustion state is preferably determined on the basis of a pressure signal indicating fluctuations in pressure in the combustion chamber, a fluctuation amount in the rotational speed of the internal combustion engine, or an ion signal indicating generation of ions in the combustion chamber.

  Here, the ion detection circuit ION that detects the ion signal includes a first capacitor C1 and a first Zener diode ZD1, and the first Zener is based on a high voltage of the secondary coil when the spark plug is discharged. A bias circuit that charges the first capacitor C1 in response to a breakdown voltage of the diode ZD1, and a current detection circuit that detects a discharge current of the first capacitor C1; A series circuit of an auxiliary capacitor C2 and an auxiliary diode D4 is connected in parallel to both ends of the battery, and when the spark plug is discharged, the auxiliary capacitor C2 is charged, and the first capacitor C1 passes through the auxiliary diode. It is preferable that the ion detection circuit is configured so as to be charged.

  According to the present invention described above, since the coil energization time is controlled together with the combustion control operation, the effect of improving the fuel consumption can be greatly enhanced.

It is drawing explaining the control parameter of this invention. 1 schematically illustrates the structure of a combustion control device. It is a flowchart explaining the operation | movement content of a combustion control apparatus. It is drawing explaining the operation | movement content of an ion detection circuit. It is another drawing explaining the operation | movement content of an ion detection circuit. It is another drawing explaining the operation | movement content of an ion detection circuit. It is another drawing explaining the operation | movement content of an ion detection circuit.

  Hereinafter, the present invention will be described in detail based on an embodiment relating to a four-cycle engine.

  In the present embodiment, the following control parameters (1) to (5) are first specified for the completed engine while performing normal combustion control. The normal combustion control includes not only air-fuel ratio control but also various combustion controls such as EGR (Exhaust Gas Recirculation) control and lean combustion control.

[(1) Lower limit value of coil energization time TM]
In a state where the engine speed Ni and the battery voltage Bj are defined (Ni, Bj), the operating load is variously changed, and in each operating state, the lower limit value TM (min) of the coil energization time TM that the spark plug can discharge is set. Identify.

  Here, the coil energization time TM means the elapsed time from the start of energization of the primary coil of the ignition coil to the end of energization, and the induced voltage generated in the secondary coil at the end of energization (that is, when the ignition coil is shut off). Based on this, the spark plug is ignited and discharged. Since the primary current increases almost linearly during energization of the primary coil, the induced voltage of the secondary coil when the ignition coil is shut off is defined corresponding to the coil energization time TM.

  The operation load for specifying the lower limit value of the coil energization time is specified by, for example, the intake air amount Pk, and the intake air amount Pk is the output value of the in-cylinder pressure sensor for detecting the pressure of the combustion chamber or the intake pressure sensor. It is determined based on. Generally, when the load is low, the induced voltage (required voltage) of the secondary coil required to discharge the spark plug is low, but when the load is high, the required voltage corresponds to the increase in the compression pressure and the increase in the cylinder flow velocity. Becomes higher. Since this required voltage greatly depends on the state of the spark plug, it can be used but corresponds to the engine speed Ni, the battery voltage Bj, and the intake air amount Pk using the worst spark plug. Then, the lower limit value TM (min) of the coil energization time is specified in the three-dimensional map.

[(2) Upper limit of coil energization time TM]
Further, the upper limit value TM (max) of the coil energization time is specified based on the heat generation limit of the ignition coil to be used. In this specific process, in the steady operation state (Ni, Bj) in which the engine speed Ni and the battery voltage Bj are defined, the coil energization time TM is increased so that the ignition coil is within the heat generation limit (for example, in a 120 ° C. atmosphere, The upper limit value TM (max) of the coil energization time to reach the coil temperature of 160 ° C. is specified.

  FIG. 1A illustrates a state where the coil temperature increases as the coil energization time is longer, and the energization limit is defined from the heat generation limit. Further, as shown in FIG. 1B, when the engine speed Ni increases, the energization limit tends to decrease at any battery voltage Bj.

[(3) Optimum value of coil energization time TM]
In addition, when the engine speed Ni and the battery voltage Bj are defined (Ni, Bj), the coil energization time TM is set within the range of the upper limit value TM (max) and the lower limit value TM (min) of the coil energization time. The optimum value TM (bst) of the coil energization time at which the fuel consumption rate becomes the minimum value is specified for each operating state. The fuel consumption rate is determined by, for example, fuel consumption rate = fuel consumption / output torque (see FIG. 1C).

  Here, the operating state is specified in consideration of not only the engine speed Ni, the battery voltage Bj, and the intake air amount Pk but also the combustion control amount such as air-fuel ratio control and EGR control.

[(4) Control target value of coil energization time TM]
In general, it is considered that the control target value TG of the coil energization time TM in feedback control is preferably set to the optimum value TM (bst) detected in (3) above. However, for example, during a transient operation that requires rapid acceleration, even if the coil energization time is changed to the upper limit in response to a sudden increase in engine load, the energization time changes drastically and rapidly from the optimum value to the upper limit. I can't let you. This is the energization end timing, which is the ignition timing, and is determined from other operating parameters. At the timing determined to be the rapid acceleration operation, the energization start timing for ensuring the coil energization time has elapsed. It is because there are things that are doing.

  Therefore, in this embodiment, the control target value TG of the coil energization time is increased by a predetermined amount β experimentally determined between the upper limit value TM (max) and the optimum value TM (bst) of the coil energization time. Set to TM (bst) + β. In addition, although the effect of fuel consumption improvement is reduced by the difference β between the target value TG and the optimum value TM (bst), the conventional apparatus that is constantly operating at the upper limit value TM (max) of the coil energization time is used. Compared to this, a significant improvement in fuel consumption is realized.

[(5) Optimum value of coil energization time TM at start-up]
When the coil temperature is not rising and the outside air temperature does not exceed a predetermined value, the coil energization time TM specified in the steady operation state exceeds the upper limit value TM (max). Energizing time can be extended.

  Therefore, the coil energization time at which the fuel consumption rate becomes the minimum value within the range exceeding the lower limit value TM (min) of the coil energization time without being limited by the upper limit value TM (max) of the coil energization time defined in (2). The optimum value TM ′ (bst) is specified. The optimum value TM ′ (best) is set as the control target value TG ′ at the start.

  Then, the timing for ending the start-up control is experimentally determined together with the conditions for executing the start-up control (cooling water temperature and outside air temperature). Here, the end timing of the start-time control is determined based on the power supply voltage, the rotation speed, the outside air temperature, the elapsed time from the start, and the like.

  The method for specifying the control parameters used in the present embodiment has been described above. Next, a combustion control apparatus that executes a control operation based on these control parameters will be described. As shown in FIG. 2, this combustion control device is mainly configured by an ignition control device CTL provided with an ion detection circuit ION, and an ECU that is an electronic control unit (Electronic Control Unit). As shown in FIG. 2, the ECU grasps the engine speed, battery voltage, cooling water temperature, outside air temperature, etc. in real time by receiving output signals from various sensors in addition to the ion signal from the ion detection circuit ION. It is configured to

  The ECU executes various combustion controls such as air-fuel ratio control, EGR (Exhaust Gas Recirculation) control, and lean combustion control based on outputs from the ion detection circuit and various sensors, and controls the coil energization time. With reference to the maps MP0 and MP1, the ignition pulse SG is output by appropriately controlling the coil energization time TM in accordance with the operation state at that time.

  Note that the H level section of the ignition pulse SG shown in FIG. 2 is the coil energization time TM, and in the control of the coil energization time TM, the control map MP0 is used at the time of cold start, and the control map MP1 is used at the subsequent steady operation. Is done. In each of the control maps MP0 and MP1, control target values TG and TG ′, an energization upper limit value TM (max), and an energization lower limit value TM (min) are defined for each operation state. As described above, the operating state is specified in consideration of not only the engine speed Ni, the battery voltage Bj, and the intake air amount Pk but also the combustion control amount such as air-fuel ratio control and EGR control.

  Next, the control operation of the ECU will be described based on the time chart shown in FIG. When the engine is started, the EUC first determines whether or not to perform start-up control (ST1). This startup control improves the unstable combustion state at startup (usually 2 to 3 minutes) by increasing the coil energization time to the coil heat generation limit at low temperatures. Therefore, in this embodiment, at the time of cold start when the engine is cold, the startup control is always executed unless the outside air temperature is exceptionally high.

  And if the determination of step ST1 is Yes, it will be determined next based on the output signal from various sensors whether start control is complete | finished (ST2). It should be noted that the conditions for finishing the start control are defined in advance so that they can be uniquely determined based on the power supply voltage, the engine speed, the outside air temperature, the elapsed time from the start, and the like.

  Therefore, when the condition for ending the start control is satisfied, the process proceeds to step ST10. However, when the condition for ending the start control is not satisfied, it is defined as an initial value or defined after the previous ignition operation. The coil energization time TM is grasped (ST3).

  Here, the end of the ignition pulse SG is uniquely defined as the ignition timing of the spark plug, but the start of the ignition pulse SG is determined by adding the end of the ignition pulse and the coil energization time TM. Then, the ignition pulse SG is shifted to the H level at the determined initial timing, and after the coil energization time TM has elapsed (ignition timing), the ignition pulse SG is returned to the L level (ST3).

  When the ignition pulse SG changes to the L level, the spark plug performs ignition discharge and the air-fuel mixture burns. Thereafter, the suitability of the combustion state is determined based on the ion signal (ST4 to ST5). Specifically, based on the waveform of the ion signal Vout, it is determined whether the combustion is normal combustion, slow combustion, or misfire.

  For example, in a predetermined determination section after ignition discharge, (a) the time integral value of the ion signal, (b) the peak value of the ion signal, or (c) the elapsed time when the ion signal exceeds the predetermined level, etc. The combustion state is determined by evaluation. In addition, (a) the time integral value is large, (b) the peak value of the ion signal is high, and (c) the elapsed time that the ion signal exceeds the predetermined level is long, it indicates that the combustion is normal. It becomes a judgment element. In addition, it is preferable to comprehensively evaluate not only the determination element in the ignition cycle but also the determination element in a plurality of ignition cycles adjacent thereto.

  If the combustion state is not good as a result of the combustion determination as described above, the coil in the next ignition cycle is appropriately subtracted and corrected (TG′−Δ) for the control target value TG ′ for cold start. The energization time is determined (ST6). When the result of the subtraction correction (TG′−Δ) is lower than the energization lower limit value TM (min), the energization lower limit value TM (min) is used.

  In any case, the control target value TG 'is stored in the corresponding part of the control map MP0, and the corresponding part to be referred to is specified based on output signals from various sensors. In this embodiment, the control target value TG 'is defined as the optimum value TM' (bst) of the coil energization time in the operating state.

  Thus, after the process of step ST6 is completed, next, the combustion control parameter of the next ignition cycle is determined so that the combustion state becomes good (ST7). This combustion parameter includes the air-fuel ratio, and the combustion is controlled in the direction of increasing the injected fuel. Therefore, in the next ignition cycle, although the improvement of the combustion state can be expected, the fuel consumption tends to deteriorate. Therefore, in this embodiment, the coil energization time TM is changed from the optimum value TM ′ (bst) to the shortening direction (ST6) in response to the expectation that the combustion state can be improved by increasing the fuel (ST6). To improve fuel efficiency.

  The control when the combustion state is not good has been described above. However, when it is determined in step ST5 that the combustion state is good, the corresponding part of the control map MP0 based on the output signals from various sensors. , The control target value TG ′ in the current operating state is specified, and the next coil energization time is set so as to approach this control target value TG ′ (ST8). In the next ignition cycle, the combustion control parameter corresponding to the operating state is selected without particularly changing the combustion control parameter such as the air-fuel ratio (ST9).

  In this way, if the control operation at the time of starting is being executed, the condition for ending the starting control is eventually satisfied, and thereafter, the processing of steps ST10 to ST18 is repeated.

  Specifically, it is first determined whether or not this timing is during a transient operation. Here, the transient operation time means a transition operation time to the operation state that changes greatly from the previous operation state, and typically corresponds to a sudden acceleration time.

  If it is during such a transition operation, the upper limit value TM (max) of the current state is selected from the coil current map MP1 for the steady state operation and set to the next coil current time TM (ST12). ). When the start timing defined by the ignition timing and the coil energization time is reached, the ignition pulse SG is transitioned to the H level, and after the coil energization time TM has elapsed, the ignition pulse SG is returned to the L level (ST12).

  On the other hand, if it is not during the transient operation, it is defined as an initial value, or the coil energization time TM defined after the previous ignition operation is grasped (ST11), and is defined by the ignition timing and the coil energization time TM. The ignition pulse SG is shifted to the H level at the start timing, and after the coil energization time TM has elapsed, the ignition pulse SG is returned to the L level (ST13).

  The subsequent processing is substantially the same as the processing of steps ST4 to ST9 at the time of starting, and the suitability of the combustion state is determined based on the ion signal (ST13 to ST14). If the combustion state is not good, control is performed. The coil energization time in the next ignition cycle is determined by appropriately subtracting and correcting the target value TG (TG−Δ) (ST15).

  Here, the control target value TG is stored in a corresponding portion of the control map MP1 for steady operation, and the corresponding portion is specified based on output signals from various sensors. As described above, the control target value TG at the time of steady control is defined as a value (+ β) that is appropriately larger than the optimum value TM (bst) of the coil energization time in the operating state. In addition, the optimum value TM (best) is approached.

  However, since the combustion deteriorates at this timing, the combustion control parameter for the next ignition cycle is determined so that the combustion state becomes good in the next ignition cycle (ST18). This combustion parameter includes the air-fuel ratio, and the combustion control in the direction of increasing the injected fuel is the same as the control at the time of starting. Further, the same applies to the improvement of fuel consumption by changing the coil energization time TM in a shortening direction in response to the tendency of deterioration of fuel consumption in the next ignition cycle.

  On the other hand, if it is determined in step ST14 that the combustion state is good, the control target value in the operation state at that time is referred to by referring to the corresponding part of the control map MP1 based on the output signals from the various sensors. TG is specified, and the next coil energization time is set so as to approach this control target value TG (ST15). In the next ignition cycle, the combustion control parameter corresponding to the operating state is selected without particularly changing the combustion control parameter such as the air-fuel ratio (ST16). These points are the same as the control at the start, except that the control target values are different.

  The control method by the ECU shown in FIG. 1 has been described above. Next, the ignition device CTL shown in FIG. 2 will be described just in case. As shown in FIG. 2, the ignition control device CTL includes an ignition coil 1 in which a primary coil L1 and a secondary coil L2 are electromagnetically coupled, a switching element 2 that controls ON / OFF of a current in the primary coil L1, a capacitor C1, and a Zener. A bias circuit 3 centered on the diode ZD1, a spark plug PG connected in series to the bias circuit 3 and the secondary coil L2, and a current detection circuit 4 using an OP amplifier AMP are mainly configured. The bias circuit 3, the secondary coil L2, the spark plug PG, and the current detection circuit 4 constitute an ion detection circuit CTL.

  Specifically, the switching element 2 is configured by an IGBT (Insulated Gate Bipolar Transistor). An ignition pulse SG is supplied to the gate terminal G of the IGBT, the collector terminal C is connected to the battery power supply VB via the primary coil L1, and the emitter terminal E is connected to the ground. The cathode terminal C and anode terminal A of the Zener diode ZD are connected to the collector terminal C and emitter terminal E of the IGBT.

  The primary coil L1 and the secondary coil L2 constituting the ignition coil 1 are wound in the secondary coil L2 when the coil winding is wound in the opposite phase and the switching element 2 is turned OFF to interrupt the current of the primary coil L1. The high voltage in the direction shown in the drawing is generated. As a result, the spark plug PG achieves positive discharge that ignites and discharges toward the ground.

  The bias circuit 3 includes a parallel circuit of a Zener diode ZD1 and a capacitor C1, a diode D1 connected between the parallel circuit and the ground, and a diode D2 connected between the parallel circuit and the low voltage terminal of the secondary coil L2. And a resistor R1 connected between the low voltage terminal of the secondary coil L2 and the diode D1.

  As illustrated, the anode terminal of the diode D1 is connected to the ground, and the cathode terminals of the diode D1 and the Zener diode ZD1 are connected to each other. The anode terminals of the diode D2 and the Zener diode ZD1 are connected to each other, and the cathode terminal of the diode D2 is connected to the low voltage side terminal of the secondary coil L2.

  In the bias circuit 3, the Zener diode ZD1 is an element that determines a bias voltage value charged in the capacitor C1, and as its breakdown voltage Vz1, for example, about 250 to 350 V is selected. In this embodiment, Vz1 = 270V. Therefore, the capacitor C1 functions as a bias power supply of about 270 V when detecting the ionic current. Capacitor C1 is selected to have a capacitance value of about 0.005 to 0.035 μF so as to function appropriately as a bias power source in consideration of its cost, installation space, and the like, and is set to 0.015 μF in the embodiment. Yes.

  Next, the current detection circuit 4 includes an OP amplifier AMP, a parallel circuit of an input resistor R2 and a capacitor C2, a detection resistor R3, and a Zener diode ZD2. Here, the capacitor C2 functions as a bypass capacitor that suppresses the combined impedance with respect to the high frequency component. In addition, the breakdown voltage of the Zener diode ZD2 is set to about 7.5 V in order to perform a protection function such as an OP amplifier AMP.

  The OP amplifier AMP operates with a single power source, and a non-inverting input terminal is connected to the ground. Then, an ion current detection signal Vout is output from the output terminal of the OP amplifier AMP.

  As illustrated, the cathode terminal of the Zener diode ZD2 is connected to the inverting input terminal of the OP amplifier AMP, and the anode terminal is connected to the ground. One side of the parallel circuit of the input resistor R2 and the capacitor C2 is connected to the inverting input terminal of the OP amplifier AMP, and the other side is connected to the capacitor C1, and the anode terminals of the Zener diode ZD1 and the diode D2.

  Further, the detection resistor R3 is connected between the inverting input terminal and the output terminal of the OP amplifier AMP, and the detection current i flows through the path of the detection resistor R3 → the input resistor R2. Therefore, a positive detection signal Vout of R3 * i is output from the output terminal of the OP amplifier AMP.

  The ion current detection device having the above configuration operates under the control of the ignition pulse SG supplied to the switching element 2. As shown in FIG. 2, the ignition pulse SG rises to the H level at timing t0 and falls to the L level at timing t1. Then, a current flows through the primary coil L1 only during the H level period of the ignition pulse SG, and magnetic energy is accumulated in the ignition coil 1 during that time. Thereafter, when the current of the primary coil L1 is cut off at the timing t1, a high-level induced voltage is generated in the secondary coil L2, and the spark plug PG is ignited and discharged.

FIG. 4A illustrates a current path during the ignition discharge. That is, at the timing t1, an induced voltage is generated in the secondary coil L2, and the first path (a) of the diode D1 → the Zener diode ZD1 → the diode D2 and the second path (b) of the diode D1 → the capacitor C1 → the diode D2. ), The diode D1 → the third path (c) of the resistor R1, and the detection resistor R3 or the Zener diode ZD2 → the parallel circuit of the resistor R2 and the capacitor C2 → the fourth path (d) of the diode D2 An ignition discharge current of the plug PG flows. In the following description, the currents in the paths (a) to (c) are I _{1 to} I ₄ .

  An equivalent circuit at the time of this discharging operation is as shown in FIG. 4 (b). If all of the forward voltage drops of the diode D2, the diode D1, and the Zener diode ZD2 are ignored, the capacitor C1, the resistor R1, and the resistor R2 However, the circuit configuration is connected in parallel to the Zener diode ZD1.

  Here, in order to effectively use the energy accumulated in the ignition coil 1 while the primary coil L1 is energized and to allow a sufficient charging current to flow through the capacitor C1, a resistor R1 or resistor that forms a bypass path for the charging current It is desirable to set the resistance value of R2 high. On the other hand, when the ion current is detected, the ion current flows through the path shown in FIG. 6, and therefore, if the resistance values of the resistors R1 and R2 are set too high, the level of the ion current decreases and the knock signal cannot be identified. Therefore, it is necessary to optimally set the resistance values of the resistors R1 and R2.

Here, if the charge of the capacitor C1 is Q, the current in the second path is a constant value I ₂ for convenience, and the ignition discharge time by the ignition discharge current I (= I ₁ + I ₂ + I ₃ + I ₄ ) is T, I ₂ = Q / T = C1 × Vz1 / T The relational expression is established. Vz1 is a breakdown voltage of the Zener diode ZD1, and is 270 V in this embodiment.

In addition, R0 = Vz / () between the parallel combined resistance R0 of the third path and the fourth path, the ignition discharge current I of the spark plug PG, the breakdown voltage Vz of the Zener diode ZD1, and the ignition discharge time T. I−C1 × Vz / T−I ₁ ) is established. Here, the current I ₁ of the first path is defined by the characteristics of the Zener diode ZD1, and the ignition discharge current I and the discharge time T are defined by other design parameters. The resistor R0 is 35 KΩ to 100 KΩ.

Then, considering the operation at the time of discharging the residual charge of the spark plug PG (see FIG. 5) and the operation at the time of ON transition of the switching element (see FIG. 7), it is preferable that the voltage across the resistor R1 is low. Therefore, in consideration of this point, in this embodiment, R1 = 62 KΩ and R2 = 200 KΩ. Parallel combined resistance R0 of the R1 in the case and R2 is about 47kohm, the charging current _{I 2} of the capacitor C1 at the time of ignition discharge is not to be so bypassed, the capacitor C1 is charged quickly to 270V level. Further, the series combined resistance R1 + R2 at the time of detecting the ionic current is 262 KΩ, and the detection performance of the ionic current and the knock signal is not adversely affected.

  Further, since the bypass capacitor C2 is connected to the resistor R2, the impedance with respect to the high frequency signal is suppressed. The capacitance value of the capacitor C2 is set to 100 pF in relation to the frequency of the resistance value of the resistor R2 (200 KΩ) and the ion signal.

  Hereinafter, the operation after ignition discharge will be described for confirmation based on FIGS. When the ignition discharge operation by the path shown in FIG. 4A is completed, the operation shown in FIG. 5 is started thereafter. That is, as shown in FIG. 5, a current flows through a path such as the spark plug PG → secondary coil L2 → resistor R1 → capacitor C1 → resistor R2 → zener diode ZD2 → ground, and the voltage across the spark plug PG suddenly increases. descend. At this time, the bias voltage of the capacitor C1 tends to increase due to the residual charge discharging operation.

  In this way, the voltage across the spark plug PG quickly drops and residual energy is discharged, but when the voltage across the spark plug PG drops to a predetermined level, an ionic current then flows through the path shown in FIG. . That is, as shown in FIG. 6, the ion current i flows through the path of the input resistor R2, the capacitor C1, the resistor R1, the secondary coil L2, and the spark plug PG, and the detection is almost proportional to the ion current i from the OP amplifier AMP. The voltage Vout = i * R3 is obtained.

  Thus, in this embodiment, although positive discharge is realized, the ionic current can be detected quickly. Further, no waveform sagging occurs, and no corona discharge is affected. These effects have been experimentally verified.

  Finally, the operation at the timing t0 is confirmed based on FIG. When the switching element 2 is turned on, a current flows through the path shown in FIG. That is, a current flows through the path of the secondary coil L2, the resistance R1, the capacitor C1, and the resistance R2, based on the induced voltage generated in the secondary coil L2. In this embodiment, the parallel combined resistance R0 of the resistance R1 and the resistance R2 is set to the resistance value of the resistance R1 << resistance R2 in the range of 35 KΩ to 100 KΩ, and accordingly, the low voltage side of the resistance R1. The terminal potential increases. However, since a current flows through the bypass path of the resistor R2 → the Zener diode ZD2 separately from the current path of the resistor R2 → the resistor R3, a large voltage is not applied to the diode D1, and the OP amplifier is also protected.

  As mentioned above, although the Example of this invention was described in detail, specific circuit structure does not limit this invention at all. For example, as in the embodiment, C2 may be parallel to the resistor R2, and a bypass capacitor may be connected in parallel to the resistor R1.

  Further, it is not always necessary to grasp the combustion state based on the ion signal. For example, the combustion state may be grasped based on the pressure signal indicating the pressure fluctuation in the combustion chamber, the amount of fluctuation in the rotational speed of the internal combustion engine, or the like. . In this case, it is simple to provide an in-cylinder pressure sensor, calculate the indicated mean effective pressure from the transition of the pressure signal, and determine the combustion state based on the calculated value. Further, a rotational speed sensor may be provided, and the combustion state may be determined based on whether or not the output signal fluctuates beyond a threshold value.

MP1 control map ECU control unit TG target values ST13 to ST14 determination means ST18, ST19 combustion control means ST15, ST17, ST11 energization control means

Claims (7)

An ignition coil in which a primary coil and a secondary coil are electromagnetically coupled, a control unit that controls energization operation of the primary coil, and an air-fuel mixture that is ignited and discharged based on an induced voltage generated in the secondary coil when the primary coil is de-energized. And a control map that defines the target value of the coil energization time of the primary coil for each operating state of the internal combustion engine,
In the control unit,
In each ignition cycle, determination means for determining the suitability of the combustion state of the mixture,
Corresponding to the combustion state determined by the determination means, combustion control means for executing the combustion operation of the next ignition cycle so as to realize a good combustion state;
The control map is referred to based on the operating state, the target value in the next ignition cycle is specified, and the coil energization time is set to be lower than the target value when the combustion state determined by the determination means is not good. Energization control means for executing the energization operation;
A combustion control device for an internal combustion engine, characterized by comprising: The target value during steady operation is
Based on the heat generation limit of the ignition coil, the upper limit value of the coil energization time defined for each operating state,
The combustion control device according to claim 1, which is set between a lower limit value of a coil energization time during which the spark plug can be discharged, which is defined for each operation state. The target value during transient operation is
The combustion control device according to claim 1 or 2, wherein the combustion control device is set to an upper limit value of a coil energization time defined for each operation state based on a heat generation limit of the ignition coil. The target value during steady operation is
Based on the heat generation limit of the ignition coil, the upper limit value of the coil energization time defined for each operating state,
The combustion control device according to claim 2 or 3, wherein the combustion control device is set between an optimum value of the coil energization time at which the fuel consumption rate becomes a minimum value.   The combustion control device according to any one of claims 1 to 4, wherein a control map for starting the cold machine is provided separately from the control map for steady operation.   The suitability of the combustion state is determined based on a pressure signal indicating fluctuations in pressure in the combustion chamber, a fluctuation amount in the rotational speed of the internal combustion engine, or an ion signal indicating generation of ions in the combustion chambers. The combustion control apparatus described in 1. The ion detection circuit ION for detecting the ion signal is:
The first capacitor C1 and the first Zener diode ZD1 have a first capacitor C1 corresponding to a breakdown voltage of the first Zener diode ZD1 based on a high voltage of the secondary coil when the spark plug is discharged. A bias circuit to be charged, and a current detection circuit for detecting a discharge current of the first capacitor C1,
A series circuit of an auxiliary capacitor C2 and an auxiliary diode D4 is connected in parallel to both ends of the first capacitor C1, and when the ignition plug is discharged, the auxiliary capacitor C2 is charged, and the first capacitor C1 is The combustion control device according to claim 6, wherein the ion detection circuit is configured to be charged via an auxiliary diode.

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