JP2008291721A - Ignition device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition device for internal combustion engine capable of preventing failure accompanying a sweating phenomenon in the ignition device for generating spark discharge in a spark discharge gap by discharge current flowing between electrodes of an ignition plug. <P>SOLUTION: The ignition device 1 for internal combustion engine is equipped with a power source device 11, the ignition plug 13 including a center electrode 21 and a grounding electrode 23, an ignition coil 15 including a primary coil 25 and a secondary coil 27 for generating voltage for ignition, an ignition transistor 17 connected in series with the primary coil 25, an electronic control device (ECU) 19, and a short circuit switch 41 capable of short-circuiting both ends of the primary coil 25. Upon spark discharge, voltage between the electrodes is measured, and when the measured absolute value is determined to be not larger than the absolute value of a reference voltage value, the spark discharge holding time is extended. Therefore, even when sweat particles are about to be formed, they are actively consumed and failure such as a bridge can be prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ignition device for an internal combustion engine that generates a spark discharge in a spark discharge gap when a discharge current flows between electrodes of an ignition plug based on an ignition voltage.

  An ignition plug (spark plug) used for ignition of an internal combustion engine is basically determined to have a life when a spark in the spark discharge gap becomes impossible. As a more specific example, the spark plug is consumed due to continued use of the spark plug, the distance of the spark discharge gap increases, and the threshold voltage (required voltage) necessary for discharge gradually increases accordingly. Eventually, when the required voltage becomes higher than the capacity of the voltage applied to the spark plug, it becomes impossible to fly and the air-fuel mixture in the combustion chamber cannot be ignited. Therefore, in order to extend the life of the spark plug, it is important to suppress electrode consumption.

  In recent years, with the spread of cogeneration systems and heat pumps, the demand for spark plugs for gas engines has increased. The conditions for using the spark plug are particularly severe. For example, a cogeneration system is often used as an industrial power or heat source, and there is a demand that it is not desired to replace a spark plug as a precondition for system shutdown. Therefore, the engine is basically operated for 24 hours, and is normally operated non-stop for 1000 to 2000 hours. Further, when an industrial large gas engine is used, it is necessary to increase the filling amount of the air-fuel mixture by supercharging in order to realize high output. When supercharging is performed, the in-cylinder pressure at the ignition timing increases and the required voltage further increases.

  Although spark plugs for gas engines require electrode life that can withstand long-term continuous use under the above-mentioned severe conditions, it is much more difficult to take concrete measures to improve lifespan than gasoline engines . That is, in a gas engine, a gaseous fuel having a boiling point below room temperature at normal pressure, such as liquefied petroleum gas (LPG) or compressed natural gas (CNG), is used. High breakdown voltage. Therefore, in the gas engine spark plug, the discharge voltage rises and the spark discharge gap is set to be quite small. Naturally, the limit gap that causes trouble in normal flying is small, and the electrode consumption allowance (that is, the gap expansion allowance) leading to the life is also limited. In addition, a gas engine using gaseous fuel cannot be expected to have a cooling effect as in the case of a gasoline engine, and the electrode temperature is likely to rise and the wear is likely to proceed. In other words, the spark plug for a gas engine tends to cause electrode consumption and has a small allowable electrode consumption.

  Therefore, it is conceivable to increase the life by increasing the center electrode diameter of the spark plug and increasing the electrode facing area forming the spark discharge gap. However, in the case of a spark plug for a gas engine, since the spark discharge gap is set narrow as described above, if the electrode facing area of the spark discharge gap is set too large, the ignition performance is adversely affected and the performance is reduced. It leads to lowering. Therefore, there is a limit to the method for increasing the life by increasing the center electrode diameter.

On the other hand, platinum (Pt) or the like is placed on the portion of the center electrode and the ground electrode facing each other across the spark discharge gap so that the spark discharge gap does not rapidly expand even when continuously used under severe conditions. It has also been proposed to provide a noble metal tip mainly composed of noble metal (see, for example, Patent Document 1).
JP 2003-257585 A

  However, when a Pt chip is provided as described above, a phenomenon called “sweat” may occur. More specifically, in a Pt chip, atomic diffusion can occur with spark discharge (sputtering atoms). The noble metal atoms once diffused in this way are unlikely to oxidize, and most of them are deposited again on the tip surface of the center electrode and the discharge surface of the ground electrode, and this is repeated to form sweat particles. It will end up. There is a concern that a bridge may be formed in the spark discharge gap due to growth of sweat particles formed by this sweat phenomenon.

  Note that the problem relating to the sweating phenomenon is not necessarily limited to the cogeneration system, and is inherent in, for example, an internal combustion engine ignition device including an ignition plug such as a gas heat pump (GHP) or a small gas engine. It is.

  The present invention has been made in view of the above circumstances, and its purpose is to generate a spark discharge in the spark discharge gap by causing a discharge current to flow between the electrodes of the spark plug based on the ignition voltage. An object of the present invention is to provide an internal combustion engine ignition device capable of preventing problems associated with sweating.

  Hereinafter, each configuration suitable for solving the above-described problems will be described in terms of items. In addition, the effect etc. peculiar to the structure to respond | correspond as needed are added.

Configuration 1. The internal combustion engine ignition device of this configuration is
Ignition voltage generating means for generating an ignition voltage;
While having a pair of electrodes separated by a spark discharge gap, at least one of these electrodes includes an ignition plug mainly composed of Pt, based on the ignition voltage generated by the ignition voltage generating means, In the internal combustion engine ignition device that generates a spark discharge in the spark discharge gap by causing a discharge current to flow between the electrodes,
Detecting means for detecting a discharge voltage state in the spark discharge;
Determination means for determining a sweating state of an electrode mainly composed of the Pt of the spark plug based on comparing the discharge voltage state detected by the detection means with a reference state;
Based on the determination result of the determination means, the apparatus has a perspiration cleaning means that realizes perspiration cleaning of the electrode mainly composed of Pt by increasing the amount of energy input per one spark discharge than before. It is characterized by that.

  Here, “Pt as a main component (electrode)” refers mainly to a portion of the electrode that forms a spark discharge gap, and the electrode itself may have Pt as a main component, A noble metal tip mainly composed of Pt may be bonded to the electrode body.

  According to the configuration 1, a discharge current flows between the electrodes of the spark plug based on the ignition voltage generated by the ignition voltage generating means, so that a spark discharge is generated in the spark discharge gap. Moreover, the discharge voltage state in the spark discharge is detected by the detection means. Further, the determination means determines the sweating state of the electrode whose main component is Pt of the spark plug based on the comparison of the detected discharge voltage state with the reference state. That is, in the process in which sweat particles adhere to the electrode and the growth occurs, the discharge voltage in the spark discharge tends to decrease. In the configuration 1, the decreasing tendency of the discharge voltage, in other words, the transition period of the perspiration grain growth is accurately determined based on the detection of the discharge voltage state and the comparison with the reference state. If the determination means determines that the electrode is sweating and is in a transitional period of sweat particle growth, the perspiration of the spark discharge is increased more than before by the sweat cleaning means. . Thereby, perspiration particles are actively consumed and perspiration cleaning can be realized. Accordingly, it is possible to effectively prevent problems such as a bridge caused by the sweating phenomenon.

  In addition, “increasing the amount of energy input per one spark discharge than before” performed by the sweat cleaning means in the configuration 1 is because the sweat particles formed on the electrode are actively consumed. No matter what the method is (any measure that increases the amount of energy input per spark discharge). Accordingly, examples of the mode include an increase in the duration of the spark discharge, an increase in the discharge current value during the spark discharge, and an increase in the ignition voltage (voltage on the power supply side).

  By the way, as an ignition voltage generation means in recent years, a primary winding and a secondary winding are provided, and one end of the primary winding is connected to the power supply device, and the primary current flowing through the primary winding is cut off. An ignition coil that generates an ignition voltage in the next winding is employed.

  In an internal combustion engine, it is known that the magnitude of input energy required to obtain normal combustion of an air-fuel mixture varies depending on the operating state of the internal combustion engine. In this case, the input energy can be expressed as the magnitude of the discharge current (secondary current) flowing in the spark discharge or the duration of the spark discharge.

  Here, when a relatively large amount of energy is input in spite of being able to operate with less input energy, the energy is excessively supplied. Such an excessive supply of energy not only contributes to the ignitability of the air-fuel mixture, but also causes an excessive increase in the electrode temperature of the spark plug, which accelerates the consumption of the electrode.

  Another problem is that in an internal combustion engine, the turbulent flow velocity of the air-fuel mixture becomes stronger (faster) under operating conditions that result in higher rotations and loads, so that in the second half of the spark discharge, the spark is caused to flow downstream. Eventually, a repetitive phenomenon (multiple discharge) may occur in which the spark discharge blows out and then reappears. Under such a phenomenon, sparks concentrate on the downstream side of the flow velocity and the electrode temperature rises rapidly, so that melting of the electrode of the spark plug is promoted, and in particular, only the electrode on the downstream side of the flow velocity is consumed. Consumption occurs, leading to a wasteful shortening of the life of the spark plug.

  As a technique for solving such a problem, for example, there is one disclosed in Japanese Patent Application Laid-Open No. 2001-304082. In the technique disclosed in the publication, the spark discharge duration time required for burning the air-fuel mixture is calculated based on the operating state of the internal combustion engine, and a command signal corresponding to the time is output. Then, based on the command signal, the short-circuit switching element short-circuits both ends of the primary winding to re-energize the primary current, and the spark discharge is forcibly cut off before the spark discharge is naturally terminated. That is, in the above technique, the spark discharge duration can be controlled by forcibly shutting off the spark discharge, and excessive supply of input energy can be suppressed. Further, by shortening the spark discharge duration at high rotation and high load, it is possible to effectively suppress the occurrence of multiple discharges under a condition where the turbulent flow velocity of the air-fuel mixture is high, such as at high rotation and high load. For these reasons, the consumption of the electrode can be suppressed, and in this respect, the life is extended.

  However, in the above technique, although the consumption of the electrode is suppressed, when sweat particles are generated as described above, the electrode discharge is suppressed by forcibly blocking the spark discharge in the first place. It is difficult to inhibit the growth of sweat particles. Therefore, for example, in an ignition device including a spark plug for a gas engine, the concern about problems such as a bridge cannot be solved.

  Therefore, it is desirable to adopt Configuration 2 described below.

Configuration 2. The internal combustion engine ignition device of this configuration is
It has a primary winding and a secondary winding, and one end of the primary winding is connected to a power supply device, and a primary current flowing through the primary winding is cut off to generate an ignition voltage in the secondary winding. An ignition coil;
Ignition switching means connected in series to the primary winding of the ignition coil and energizing / cutting off the primary current flowing from the power supply device to the primary winding;
The electrode has a pair of electrodes separated by a spark discharge gap, and at least one of these electrodes is mainly composed of platinum (Pt), and one of the electrodes is connected in series to the secondary winding, and the ignition coil An ignition plug capable of generating a spark discharge in the spark discharge gap by causing a discharge current to flow between the electrodes based on the generated ignition voltage;
Short-circuit switching means connected in parallel to the primary winding and capable of short-circuiting both ends of the primary winding based on a predetermined drive signal;
A spark discharge duration calculation setting means for calculating and setting a spark discharge duration required to burn the air-fuel mixture by the spark discharge based on the operating state of the internal combustion engine;
The primary winding is driven by driving the short-circuit switching means by outputting the drive signal to the short-circuit switching means in accordance with the spark discharge duration set by the spark discharge duration calculation setting means. In an ignition device for an internal combustion engine comprising a spark discharge blocking means for forcibly blocking the spark discharge by short-circuiting both ends thereof,
Detecting means for detecting a discharge voltage state in the spark discharge;
Determining means for determining a sweating state of an electrode whose main component is the Pt of the spark plug based on comparing the discharge voltage state detected by the detecting means with a reference state;
The spark discharge duration calculation setting means can extend and set the spark discharge duration based on the determination result of the determination means.

  According to the above configuration 2, the spark discharge interrupting means outputs a drive signal to the short-circuit switching means in accordance with the spark discharge duration set by the spark discharge duration calculation setting means. Thereby, the switching means for short circuit is driven, both ends of the primary winding are short-circuited, and the spark discharge is forcibly cut off. Therefore, excessive supply of input energy can be suppressed, and generation of multiple discharges can be effectively suppressed. Therefore, consumption of the electrode can be suppressed, and the life of the spark plug can be extended.

  Moreover, in this structure 2, the discharge voltage state in spark discharge is detected by the detection means. Further, the determination means determines the sweating state of at least one electrode of the spark plug based on the comparison of the detected discharge voltage state with the reference state. That is, in the process in which sweat particles adhere to the electrode and the growth occurs, the discharge voltage in the spark discharge tends to decrease, and in the configuration 2, the discharge voltage tends to decrease, in other words, the sweat particle growth. The transition period is accurately determined based on detecting the discharge voltage state and comparing it with the reference state. When the determination means determines that the electrode is perspiring and is in a transitional period of sweat particle growth, the spark discharge duration calculated and set by the spark discharge duration calculation setting means is extended. For this reason, perspiration particles are actively consumed, and perspiration cleaning can be realized. Accordingly, it is possible to effectively prevent problems such as a bridge caused by the sweating phenomenon, and it is possible to extend the life of the spark plug in this respect. Particularly, in the ignition device including the ignition plug for the gas engine in the cogeneration system, the above-described configuration 2 is remarkably effective.

  Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is an electric circuit diagram showing a configuration of an internal combustion engine ignition device 1 according to the present embodiment, and this internal combustion engine ignition device 1 is configured to generate a spark discharge between electrodes of a spark plug 13. In addition, the voltage between the electrodes of the spark plug 13 can be detected.

  In this embodiment, the description is made for one cylinder. However, it is needless to say that the present invention can also be applied to an internal combustion engine having a plurality of cylinders. The basic configuration is the same. As shown in FIG. 1, the internal combustion engine ignition device 1 according to the present embodiment includes a power supply device (battery) 11 that outputs a constant voltage (for example, voltage 12 [V]), a center electrode 21, and a ground electrode 23. The ignition plug 13 provided in the cylinder of the internal combustion engine, the primary coil 25 and the secondary coil 27, the ignition coil 15 as ignition voltage generating means for generating an ignition voltage, and the primary coil 25 are connected in series. An ignition transistor 17 composed of a connected npn-type power transistor and an electronic control unit (ECU) 19 that outputs an ignition command signal for driving and controlling the ignition transistor 17 are provided.

  Further, the internal combustion engine ignition device 1 measures a backflow prevention diode 31 having a cathode connected to the secondary winding 27 and an anode connected to the center electrode 21 of the ignition plug 13, and an inter-electrode voltage of the ignition plug 13. And a voltage certifying circuit 37 for certifying the voltage between the electrodes of the spark plug 13 based on the measurement result of the voltage detector 36.

  Among these, the ignition transistor 17 is a switching element made of a semiconductor element that performs a switching operation based on the ignition command signal Sa from the ECU 19 in order to energize / cut off the primary winding 25 of the ignition coil 15. The ignition switching means in this embodiment is configured. The ignition device provided in the internal combustion engine of the present embodiment is a full transistor ignition device.

  The primary winding 25 has one end connected to the positive electrode of the power supply device 11 and the other end connected to the collector of the ignition transistor 17. The secondary winding 27 has one end connected to the cathode of the backflow prevention diode 31. The other end is connected to the positive electrode of the power supply device 11.

  Further, the backflow prevention diode 31 has a cathode connected to the secondary winding 27 and an anode connected to the center electrode 21 of the spark plug 13, so that the center electrode 21 of the spark plug 13 is connected to the secondary winding 27. The energization of the current that flows is allowed, and the energization of the current that is directed from the secondary winding 27 toward the center electrode 21 of the spark plug 13 is prevented.

  Further, in the spark plug 13, a ground electrode 23 that forms a spark discharge gap 24 that generates a spark discharge facing the center electrode 21 is grounded to the ground having the same potential as the negative electrode of the power supply device 11. In addition, although not shown in figure, the noble metal chip | tip which has Pt as a main component is provided in the opposing surface of each electrode 21 and 23. FIG. The ignition transistor 17 has a base connected to the output terminal 191 of the ignition command signal Sa of the ECU 19 and an emitter grounded to the ground having the same potential as the negative electrode of the power supply device 11.

  In the present embodiment, a shorting switch 41 for short-circuiting both ends of the primary winding 25 is provided. The shorting switch 41 is connected in parallel to the primary winding 25 and also connected to the output terminal 192 of the spark discharge duration control signal Sb of the ECU 19. The short-circuit switch 41 functions as a short-circuit switching means, and its internal line is normally open. When a spark discharge duration control signal Sb (for example, a high level signal) is input to the shorting switch 41, the internal line is short-circuited, and the spark discharge duration control signal Sb is not input or a low level signal is input. Is input, the internal line shifts to an open state. In addition, you may comprise so that it may transfer to an open state automatically, when the electric current which flows through an internal line becomes below a predetermined electric current value, for example, can comprise using a thyristor and a triac.

  When the ignition command signal Sa output from the ECU 19 is at a low level (generally a ground potential) on the assumption that the internal line of the short-circuit switch 41 is open, the base current does not flow and the ignition command signal Sa The transistor 17 is turned off (cut-off state), and no current (primary current A1) flows through the primary winding 25 by the ignition transistor 17. When the ignition command signal Sa output from the ECU 19 is at a high level (generally, the supply voltage 5 [V] from the constant voltage power supply), the base current flows and the ignition transistor 17 is turned on (energized state). Thus, a current (primary current A 1) flows through the primary winding 25 by the ignition transistor 17. Note that magnetic flux energy is accumulated in the ignition coil 15 by energizing the primary winding 25.

  For this reason, when the ignition command signal Sa is switched to the low level from the state where the ignition command signal Sa is at the high level and the primary current A1 flows through the primary winding 25, the ignition transistor 17 is turned off and the primary winding is turned on. Energization of the primary current A1 to the line 25 is interrupted (stopped). Then, the magnetic flux density in the ignition coil 15 changes abruptly, and an ignition voltage is generated in the secondary winding 27, which is applied to the ignition plug 13, thereby sparking between the electrodes 21-23 of the ignition plug 13. Discharge occurs.

  The ignition coil 15 generates a negative ignition voltage lower than the ground potential at the center electrode 21 of the spark plug 13 in the secondary winding 27 by cutting off (stopping) energization of the primary winding 25. The spark plug 13 generates a spark discharge between the electrodes 21-23 when this ignition voltage is applied. A secondary current (discharge current) A2 that flows along with the spark discharge flows from the center electrode 21 of the spark plug 13 through the secondary winding 27 to the primary winding 25 side.

  On the other hand, when a spark discharge duration control signal Sb (for example, a high level signal) is input during the spark discharge as described above and the shorting switch 41 short-circuits both ends of the primary winding 25, the residual energy of the ignition coil 15. As a result, a current flows through the primary winding 25 through the short-circuit switch 41. Then, an induced voltage (back electromotive force) having a polarity opposite to the residual induced voltage is generated in the secondary winding 27. As a result, a voltage obtained by subtracting the back electromotive force from the residual induced voltage is generated at both ends of the secondary winding 27, so that the spark discharge at the spark plug 13 is forcibly cut off. In other words, in the present embodiment, the spark discharge duration per one spark discharge, and hence the amount of energy input is controlled by the spark discharge duration control signal Sb.

  Furthermore, as described above, the voltage detector 36 can measure the voltage between the electrodes of the spark plug 13, and the voltage certification circuit 37 recognizes the voltage between the electrodes of the spark plug 13 based on the measurement result. Can be done. As each circuit portion (not shown) provided in the voltage certification circuit 37, a known configuration may be appropriately used, such as a combination of a peak hold circuit and a comparator circuit. A signal related to the interelectrode voltage output from the voltage certification circuit 37 is input to the ECU 19. Then, the ECU 19 determines whether or not the absolute value of the interelectrode voltage (peak value) is larger than the preset absolute value of the reference voltage value based on the input signal. When it is determined that the absolute value of the interelectrode voltage (peak value) is larger than the absolute value of the reference voltage value, it is determined that there is no abnormality in the sweating state of the electrode. This is because the absolute value of the interelectrode voltage decreases if sweating occurs on the electrodes. On the other hand, when it is determined that the absolute value of the interelectrode voltage (peak value) is not larger than the absolute value of the reference voltage value, there is an abnormality with respect to the sweating state of the electrode (the transitional period of the sweating particles). ).

  Next, an ignition control process executed in the ECU 19 of the internal combustion engine ignition device 1 will be described with reference to a flowchart shown in FIG. In addition, a timing chart showing the state of each part (ignition command signal Sa, spark discharge duration control signal Sb, interelectrode voltage of the spark plug 13) in the internal combustion engine ignition device 1 over time when executing the ignition control process. Is shown in FIG.

  The ECU 19 is for comprehensively controlling spark discharge generation (ignition), fuel injection amount, fuel injection timing, idle speed, etc. of the internal combustion engine. In addition to the ignition control processing described below, the ECU 19 Various control processes are executed. In addition to the control process, the operating state for detecting the operating state of each part of the engine, such as the intake air amount (intake pipe pressure), rotation speed (engine rotation speed), throttle opening, cooling water temperature, intake air temperature, etc. Detection processing and the like are executed. Further, this control process is performed once in one combustion cycle in which the internal combustion engine performs intake, compression, combustion, and exhaust based on a signal from a crank angle sensor that detects the rotation angle (crank angle) of the internal combustion engine, for example. Is to be executed.

  When the internal combustion engine is started and the ignition control process is started, the ECU 19 first reads the operation state of the internal combustion engine detected in the operation state detection process separately executed in step S101. Next, in step S102, it is determined whether or not the extension permission flag FEXT is set to “1” in the previous process. Here, the extension permission flag FEXT is set to “1” when the extension of the spark discharge duration Tt is permitted, and is set to “0” otherwise. The initial value at the time is set to “0”. If the determination in step S102 is affirmative, in step S103, the self is instructed to extend the spark discharge duration Tt (calculated and set in step S104), and this is temporarily stored. Then, the process proceeds to the next step S104. If a negative determination is made in step S102, the process proceeds to step S104 without passing through the process of step S103.

  Shifting from step S102 or step S103, in step S104, the spark discharge generation timing ts (so-called ignition timing) and the spark discharge duration Tt are calculated and set based on the operating state read in step S101. In the process of step S104, the spark discharge generation timing ts is determined by using the engine speed calculated using the engine speed of the internal combustion engine, the throttle opening, the intake pipe negative pressure (intake air amount), and the like as parameters. The control reference value is obtained based on a map, a table or a calculation formula to be calculated, and is calculated and set by a method of correcting the control reference value based on the cooling water temperature, the intake air temperature, and the like. Further, the spark discharge duration Tt is set using a map, table, or calculation formula prepared in advance based on the sweating state of the electrodes, that is, the voltage between the electrodes. At this time, if the instruction to extend the spark discharge duration Tt is temporarily stored in the step S103, the spark discharge duration Tt is set longer (extension setting) than when it is not. The Rukoto. By setting the spark discharge duration Tt in this way, the counter electromotive force generation time for generating the counter electromotive force in the secondary winding 27 is set.

  Next, in step S105, based on the spark discharge occurrence timing ts calculated and set in step S104, the primary winding that is earlier than the spark discharge occurrence timing ts by a preset primary winding energization time. 25 is obtained, and at the time when the energization start timing is reached (timing t1, t11, t21 shown in FIG. 2), the ignition command signal Sa is changed from the low level to the high level.

  When the ignition command signal Sa is switched from the low level to the high level by the process of step S105, the ignition transistor 17 is turned on, and the primary current A1 flows through the primary winding 25 of the ignition coil 15. The primary winding energization time until the spark discharge occurrence time ts is such that the energy accumulated in the ignition coil 15 by energizing the primary winding 25 can burn the air-fuel mixture under all operating conditions of the internal combustion engine. It is set in advance so as to be spark energy.

  Further, in the subsequent step S106, based on the crank angle detection signal from the crank angle sensor, it is determined whether or not the spark discharge occurrence time ts set in step S104 has been reached. Is repeated until the spark discharge occurrence time ts is reached. When it is determined in step S106 that the spark discharge occurrence time ts has been reached, the process proceeds to step S107.

  In step S107, the ignition command signal Sa is inverted from the high level to the low level (timing t2, t12, t22 shown in FIG. 2). As a result, the ignition transistor 17 is turned off, the primary current A1 is cut off, the magnetic flux density of the ignition coil 15 is suddenly changed, and an ignition voltage is generated in the secondary winding 27. A spark discharge occurs between the two.

  Here, as is apparent from the timing chart shown in FIG. 2, the absolute value of the voltage between the electrodes of the spark plug 13 becomes remarkably large at the timing t2 when the ignition command signal Sa is inverted from the high level to the low level. I understand. Along with this, the secondary current A2 flows. Then, in the subsequent step S108, the voltage between the electrodes is measured (certified) based on a signal relating to the voltage between the electrodes input from the voltage certification circuit 37 to the ECU 19 for a while from the time point when the positive determination is made in step S106. To do. In step S109, it is determined whether or not the absolute value of the interelectrode voltage (peak value) measured this time is larger than the absolute value of a preset reference voltage value. If it is determined that the absolute value of the interelectrode voltage (peak value) is larger than the absolute value of the reference voltage value, there is no abnormality in the sweating state of the electrode, and it is necessary to extend the spark discharge duration Tt. In step S110, the extension permission flag FEXT is set to “0”, and the process proceeds to step S112.

  On the other hand, if it is determined that the absolute value of the interelectrode voltage (peak value) is not larger than the absolute value of the reference voltage value, there is an abnormality in the sweating state of the electrode (in the growth transition period of sweating particles). ) It is determined that it is necessary to permit extension of the spark discharge duration Tt, the extension permission flag FEXT is set to “1” in step S111, and the process proceeds to step S112.

  In step S112, it is determined whether or not the spark discharge duration Tt set in step S104 has elapsed since the ignition command signal Sa becomes low level. If a negative determination is made, step S112 is repeatedly executed to wait until the spark discharge duration Tt elapses. When it is determined in step S112 that the time from when the ignition command signal Sa has become low level has reached the spark discharge duration Tt (time t3 shown in FIG. 2), the process proceeds to step S113.

  In step S113, the spark discharge duration control signal Sb is output or a process of switching from the low level to the high level is performed (timing t3, t13, t23 in FIG. 2). As a result, a primary current A1 flows through the primary winding 25 of the ignition coil 15, and a back electromotive force having an opposite polarity to the ignition voltage is generated in the secondary winding 27. Thereby, the spark discharge generated in the spark plug 13 is forcibly interrupted.

  Then, after it is determined in step S114 that the predetermined time has elapsed, in step S115, the process of stopping the output of the spark discharge duration control signal Sb or the process of switching from the high level to the low level is performed, and the ECU 19 temporarily performs the subsequent processes. finish.

  In FIG. 2, the time points from timing t1 to timing t4 correspond to the time points from timing t11 to timing t14 and from timing t21 to timing t24, respectively. An example of a chart at normal time is shown from timing t1 to timing t4. From timing t11 to timing t14, the absolute value of the interelectrode voltage (peak value) is smaller than the absolute value of the reference voltage value. An example of a chart in the case where an abnormality occurs in the sweating state of the electrode, that is, in the transitional transition period of the sweating particles is shown. An example of a chart when the extension permission flag FEXT is set to “1” and the spark discharge duration Tt is set to be extended from the timing t21 to the timing t24 is shown.

  In the present embodiment, the voltage detector 36 and the voltage certification circuit 37 correspond to the detection means described in the claims, and the processing executed by the ECU 19 includes determination means, sweat cleaning means, and spark discharge duration calculation. Corresponds to setting means and spark discharge interruption means. In particular, the process of step S109 corresponds to the determination means, the process of step S104 corresponds to the spark discharge duration calculation setting means, and the processes of step S111, step S103, step S104, etc. extend the spark discharge duration, And it corresponds to enlarging the amount of energy input per one spark discharge than before.

  In determining the amount of energy input to the spark plug 13, the amount of input is determined with reference to a map in which the amount of energy required for cleaning perspiration is determined with respect to the discharge voltage obtained in advance by the judging means. A method such as determination can be employed.

  As described above in detail, according to the present embodiment, the interelectrode voltage is measured for a while after the timing at which the ignition command signal Sa is inverted from the high level to the low level. Then, it is determined whether or not the absolute value of the interelectrode voltage (peak value) measured this time is larger than the absolute value of the reference voltage value. If the determination is negative, the extension permission flag FEXT is set to “1”. The spark discharge duration Tt is extended in the next process. That is, in the process in which sweat particles adhere to the electrodes 21 and 23 (Pt precious metal tips) and the growth occurs, the discharge voltage (interelectrode voltage) in the spark discharge tends to decrease. The decreasing tendency of the voltage between the electrodes, in other words, the transition period of the perspiration grain growth is accurately determined, and the spark discharge duration Tt is extended based on the determination. For this reason, even if sweat particles are about to be formed, they are actively consumed. Therefore, it is possible to effectively prevent problems such as a bridge caused by the sweating phenomenon, and to extend the life of the spark plug 13.

  Here, in order to confirm the above-mentioned effect, in the cogeneration system, the internal combustion engine ignition device 1 of the above embodiment was applied, and the relationship of the required voltage (kV) with respect to the operation time was measured. The result is shown in the graph of FIG. In the figure, a graph indicated by a white square corresponds to the prior art, and shows a case where the spark discharge duration time is not controlled (control by the spark discharge duration time control signal Sb is not performed). In general, the spark discharge duration when the special spark discharge duration is not adjusted is about 1.0 ms to 1.5 ms, and in this example, the test is performed as 1.5 ms. A graph indicated by white circles corresponds to the prior art, and shows a case where the spark discharge duration is fixed to “0.2 ms” in order to suppress consumption of the noble metal tip. Further, a graph indicated by a black rhombus corresponds to the present embodiment, and shows a case where extension control of the spark discharge duration Tt is performed when it is determined that the state is sweating. The spark discharge duration is controlled to be 0.2 ms when sweating is not occurring and 1.5 ms when it is determined that sweating is occurring. In the above measurement, a 6-cylinder gas cogeneration engine is used as the internal combustion engine, and an alloy mainly composed of iridium (Ir) is bonded to the ground electrode as a noble metal tip bonded to the center electrode of the spark plug. Alloys mainly composed of platinum (Pt) were used as the noble metal tips to be used, and the initial spark discharge gap (initial gap) was set to 0.3 mm.

  As can be seen from the figure, according to the present embodiment, the degree of increase in the required voltage with respect to the passage of time could be suppressed as compared with the case where the spark discharge duration time was not controlled. Further, when the control was performed so that the spark discharge duration was “0.2 ms”, an increase in the required voltage was not recognized, but an inter-electrode bridge was generated, causing a misfire. On the other hand, in the present embodiment, it was revealed that even if the operation for 3000 hours is continued while the degree of increase in the required voltage is suppressed, the inter-electrode bridge does not occur, and a significantly longer life can be realized.

  In addition, it is not limited to the description content of embodiment mentioned above, For example, you may implement as follows.

  (A) In the above embodiment, the voltage detector 36 for measuring the voltage between the electrodes of the spark plug 13 (in other words, the raw value) is provided. Based on the measurement result of the voltage detector 36, the spark plug 13 The voltage between electrodes is to be certified. On the other hand, as long as the discharge voltage state in the spark discharge can be detected, it may be detected in other forms. For example, as described below, the interelectrode voltage of the spark plug 13 is divided by electrostatic partial pressure. You may measure by pressing.

  For example, in the configuration shown in FIG. 5, a voltage detection circuit 51 is provided instead of the voltage detector 36 of the above embodiment. The voltage detection circuit 51 is connected between a conductor 53 that is capacitively coupled between the anode of the backflow prevention diode 31 and the energization path that connects the center electrode 21 of the spark plug 13, and between the conductor 53 and the ground. And a resistor 55 connected in parallel to the capacitor 54. The conductor 53 is composed of an electrode plate disposed at a predetermined interval with respect to the energization path, and constitutes a capacitive element together with the energization path. Note that, in the electrostatic capacitance element configured by the conductor 53 and the energization path, charges corresponding to the voltage between the electrodes of the spark plug 13 are accumulated.

  The conductor 53 and the capacitor 54 constitute a voltage dividing circuit that divides the voltage between the electrodes of the spark plug 13. The voltage across the capacitor 54 is the voltage between the electrodes of the spark plug 13, the conductor 53 and the capacitor 54. The divided voltage is determined based on the voltage division ratio of 54. That is, the voltage across the capacitor 54 has a voltage value proportional to the voltage between the electrodes of the spark plug 13. A connection point between the conductor 53 and the capacitor 54 is connected to an input terminal of the voltage certification circuit 37, and a divided voltage by the conductor 53 and the capacitor 54 is input to the voltage certification circuit 37.

  With such a configuration, the configuration can be significantly reduced in size.

  (B) In the above embodiment, the absolute value of the measured interelectrode voltage is not larger than the preset absolute value of the reference voltage value, that is, the discharge voltage (interelectrode voltage) in the spark discharge is reduced. When it is determined that there is a tendency, the amount of energy input is increased by extending the spark discharge duration Tt. On the other hand, when it is determined that the sweating grain is in a transitional period, the amount of energy input per spark discharge is larger than before, and the sparking plug is actively introduced. As long as it can be consumed, the sweat cleaning may be realized by other methods such as (b-1), (b-2), and (b-3) described below.

  (B-1) As shown in FIG. 6, in this example, the shorting switch 41 provided in the above embodiment is omitted, and the circuit configuration is relatively simple. In such a configuration, as shown in FIG. 7, the ECU 19 does not have the measured absolute value of the inter-electrode voltage larger than the preset absolute value of the reference voltage value, that is, the discharge voltage (electrode in spark discharge). Is determined to decrease (see timings t42 to 43 in FIG. 7), the ignition command signal Sa is set to the normal state (see timings t31 to t33 in FIG. 7) in the next process. Switch from low level to high level earlier. That is, as apparent from the timings t51 to t53 in FIG. 7, when the ignition command signal Sa is switched from the low level to the high level at the timing t51a, the ignition command signal Sa is switched at a timing t51 earlier than that. Is switched from the low level to the high level. Thereby, the period (pulse width) during which the ignition command signal Sa is at the high level is increased. Therefore, after the timing t52 when the ignition command signal Sa is switched from the high level to the low level, the spark discharge voltage is increased and the secondary current A2 is increased.

  Thus, even if the period (pulse width) during which the ignition command signal Sa is at a high level is increased, an increase in the amount of energy input per one spark discharge can be realized, and sweat particles Actively exhausted.

  (B-2) As shown in FIG. 8, in this example, the short-circuit switch 41 provided in the above embodiment is omitted, and a variable voltage power supply 61 is used instead of the constant voltage power supply device 11. It is used. A voltage switching signal Sc from the ECU 19 is input to the variable voltage power supply 61. In a normal state, a low-level voltage switching signal Sc is input, and the power supply voltage V11 at this time is set to be relatively low.

  In this configuration, as shown in FIG. 9, the ECU 19 does not have the absolute value of the measured interelectrode voltage larger than the absolute value of the preset reference voltage value, that is, the discharge voltage (electrode in spark discharge). Is determined to decrease (see timings t72 to t73 in FIG. 9), the voltage switching signal Sc is switched from the normal low level to the high level in the next processing. The power supply voltage is set to V12 higher than the previous V11. That is, as apparent from the timings t81 to t83 in FIG. 9, the primary current A1 increases relatively slowly from the time when the ignition command signal Sa is normally at the normal level (see the broken line). In the stage before the ignition command signal Sa is switched from the low level to the high level at the timing 81, the primary current A1 is increased more rapidly by increasing the power supply voltage (see the solid line). Thereby, after the timing t82 when the ignition command signal Sa is switched from the high level to the low level, the spark discharge voltage is increased and the secondary current A2 is increased.

  As described above, even when the power supply voltage is increased using the variable voltage power supply 61, an increase in the amount of energy input per one spark discharge can be realized, and the sweat particles are actively consumed.

  (B-3) In the above (b-2 [FIG. 8]), the variable voltage power supply 61 is used. However, the present invention is not limited to this, and the power supply device 11 (which is a constant voltage power supply) and the ignition coil 15 (primary winding). 25), and a booster circuit (not shown) may be loaded and controlled by the ECU 19 or an ignition signal setting circuit described later as (f) (the same applies to (c-2) described later). ).

  (C) Moreover, in the said embodiment, it is supposed that a full transistor system is employ | adopted as an ignition device with which an internal combustion engine is equipped. On the other hand, a CDI (Capacitor Discharge Ignition) method may be adopted as shown in the following methods (c-1) and (c-2).

  (C-1) As shown in FIG. 10, in this example, a thyristor 70 is provided instead of the ignition transistor 17 provided in the above embodiment. The thyristor 70 plays a role of a switch for causing the primary current A1 to flow in response to the ignition command signal Sa1 output from the ECU 19. That is, the anode of the thyristor 70 is connected to the primary winding 25, and the cathode is grounded. An ignition command signal Sa1 from the ECU 19 is output to the gate of the thyristor 70. Further, a backflow prevention diode 32 is provided between the power supply device 11 and the primary winding 25, and one end of the variable capacitor 71 is connected between the cathode of the backflow prevention diode 32 and the primary winding 25. It is connected. The other end of the variable capacitor 71 is grounded. A capacity switching signal Sd from the ECU 19 is input to the variable capacity capacitor 71. In a normal state, a low-level capacitance switching signal Sd is input, and the capacitor capacitance C11 at this time is set to be relatively small.

  In such a configuration, as shown in FIG. 11, the ECU 19 does not have the measured absolute value of the inter-electrode voltage larger than the preset absolute value of the reference voltage value, that is, the discharge voltage (electrode in spark discharge). Is determined to decrease (see timings t112 to t113 in FIG. 11), the capacity switching signal Sd is switched from the low level in the normal state to the high level in the next processing. The capacitor capacity is C12 which is larger than C11 so far. As a result, as apparent from the timing t131 to t132 in FIG. 11, the primary current A1 is increased. Therefore, after the timing t132 when the primary current A1 becomes zero, the spark discharge voltage is increased and the secondary current A2 is increased.

  As described above, even if the capacitor capacity in the CDI method is increased by using the variable capacitor 71, the amount of energy input per one spark discharge can be increased, and the sweat particles are actively consumed. It is done.

  (C-2) Further, in the CDI system, it can be configured as shown in FIG. In this example, a constant-capacitance capacitor 81 is provided instead of the variable-capacitance capacitor 71 provided in (c-1) above. On the other hand, similarly to the above (b-2), a variable voltage power supply 61 is used instead of the constant voltage power supply device 11. A voltage switching signal Sc from the ECU 19 is input to the variable voltage power supply 61. In a normal state, a low-level voltage switching signal Se is input, and the power supply voltage V11 at this time is set to be relatively low.

  In this configuration, as shown in FIG. 13, the ECU 19 does not have the measured absolute value of the interelectrode voltage larger than the preset absolute value of the reference voltage value, that is, the discharge voltage (electrode in spark discharge). Is determined to decrease (see timings t152 to t153 in FIG. 13), the voltage switching signal Se is switched from the normal low level to the high level in the next processing. The power supply voltage is set to V12 that is larger than the previous V11. As a result, as apparent from the timing t161 to t162 in FIG. 13, the primary current A1 is increased. Therefore, after the timing t162 when the primary current A1 becomes zero, the spark discharge voltage is increased and the secondary current A2 is increased.

  As described above, even when the power supply voltage in the CDI method is increased by using the variable voltage power supply 61, the amount of energy input per one spark discharge can be increased, and the sweat particles are actively consumed. .

  (D) In the above embodiment, in step S109, it is determined whether the absolute value of the interelectrode voltage (peak value) measured this time is larger than the absolute value of the preset reference voltage value, and a negative determination is made. If so, the extension permission flag FEXT is set to “1” in step S111. In other words, a configuration is employed in which the spark discharge duration Tt is extended if a negative determination is made in step S109 even once. In contrast, the extension permission flag FEXT is set to “1” only when it is repeatedly determined that the absolute value of the interelectrode voltage is not larger than the absolute value of the reference voltage value a predetermined number of times. It is also good to do. By allowing the extension of the spark discharge duration Tt only when the abnormality is repeatedly determined as described above, the extension of the spark discharge duration Tt in the case where an abnormality is detected only once by some error is performed. There is nothing. For this reason, useless electrode consumption can be suppressed.

  It should be noted that the perspiration cleaning means in the ignition device of the present invention does not necessarily have to be compared with the steady discharge immediately before the execution of perspiration cleaning (increasing the amount of energy input per one spark discharge). Since the growth of sweat does not occur suddenly but grows as sputtering atoms gradually accumulate, it is not always possible to make a highly accurate judgment only by considering several consecutive cycles. For this reason, in order to improve the detection accuracy of sweat generation, that is, to make a highly accurate determination, for example, a determination is made every 10 hours of engine operation, for example, whether the discharge voltage has increased after a predetermined period of time. It may be determined whether or not.

  (E) The internal combustion engine ignition device 1 as in the above embodiment may be used in, for example, a cogeneration system, or may be applied to an apparatus including an ignition plug such as a GHP or a small gas engine. Is also possible.

  (F) In the above embodiment, the spark discharge duration calculation setting means is embodied by the process of the ECU 19, but does not necessarily have to be based on the process of the ECU 19. For example, an “ignition signal setting circuit” is separately provided between the ECU 19 and a switch for turning on and off the main energization (for example, the ignition transistor 17), and the spark discharge duration is calculated and set by the ignition signal setting circuit. However, the switch may be controlled.

1 is an electric circuit diagram showing a configuration of an internal combustion engine ignition device according to an embodiment. It is a timing chart showing the state of each part (ignition command signal, spark discharge duration control signal, voltage between electrodes of a spark plug) in an internal combustion engine ignition device. It is a flowchart which shows the processing content of the ignition control process performed by ECU. It is a figure which shows the effect of this embodiment, Comprising: It is a graph which shows the relationship of the request voltage with progress of operation time, contrasting with a prior art. It is an electric circuit diagram which shows the structure of the ignition device for internal combustion engines in another embodiment. It is an electric circuit diagram which shows the structure of the ignition device for internal combustion engines in another embodiment. It is a timing chart showing the state of each part of the ignition device for internal combustion engines in another embodiment. It is an electric circuit diagram which shows the structure of the ignition device for internal combustion engines in another embodiment. It is a timing chart showing the state of each part of the ignition device for internal combustion engines in another embodiment. It is an electric circuit diagram which shows the structure of the ignition device for internal combustion engines in another embodiment. It is a timing chart showing the state of each part of the ignition device for internal combustion engines in another embodiment. It is an electric circuit diagram which shows the structure of the ignition device for internal combustion engines in another embodiment. It is a timing chart showing the state of each part of the ignition device for internal combustion engines in another embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Ignition device for internal combustion engines, 11 ... Power supply device, 13 ... Spark plug, 15 ... Ignition coil, 17 ... Ignition transistor, 19 ... Electronic control unit (ECU), 25 ... Primary winding, 27 ... Secondary winding 36 ... Voltage detector 37 ... Voltage certification circuit 61 ... Variable voltage power supply 71 ... Variable capacity small sensor A1 ... Primary current A2 ... Secondary current Sa, Sa1 ... Ignition command signal, Sb ... Spark discharge duration Time control signal, Sc, Se... Voltage switching signal, Sd.

Claims (2)

Ignition voltage generating means for generating an ignition voltage;
An ignition voltage having a pair of electrodes separated by a spark discharge gap and at least one of these electrodes having an ignition plug mainly composed of platinum (Pt) and generated by the ignition voltage generating means In the internal combustion engine ignition device that generates a spark discharge in the spark discharge gap by causing a discharge current to flow between the electrodes,
Detecting means for detecting a discharge voltage state in the spark discharge;
Determination means for determining a sweating state of an electrode mainly composed of the Pt of the spark plug based on comparing the discharge voltage state detected by the detection means with a reference state;
Based on the determination result of the determination means, the apparatus has a perspiration cleaning means that realizes perspiration cleaning of the electrode mainly composed of Pt by increasing the amount of energy input per one spark discharge than before. An internal combustion engine ignition device. It has a primary winding and a secondary winding, and one end of the primary winding is connected to a power supply device, and a primary current flowing through the primary winding is cut off to generate an ignition voltage in the secondary winding. An ignition coil;
Ignition switching means connected in series to the primary winding of the ignition coil and energizing / cutting off the primary current flowing from the power supply device to the primary winding;
The electrode has a pair of electrodes separated by a spark discharge gap, and at least one of these electrodes is mainly composed of platinum (Pt), and one electrode is connected in series to the secondary winding, and the ignition coil An ignition plug capable of generating a spark discharge in the spark discharge gap by causing a discharge current to flow between the electrodes based on the generated ignition voltage;
Short-circuit switching means connected in parallel to the primary winding and capable of short-circuiting both ends of the primary winding based on a predetermined drive signal;
Spark discharge duration calculation setting means for calculating and setting a spark discharge duration required to burn the air-fuel mixture by the spark discharge based on the operating state of the internal combustion engine;
The primary winding is driven by driving the short-circuit switching means by outputting the drive signal to the short-circuit switching means in accordance with the spark discharge duration set by the spark discharge duration calculation setting means. In an ignition device for an internal combustion engine comprising a spark discharge blocking means for forcibly blocking the spark discharge by short-circuiting both ends thereof,
Detecting means for detecting a discharge voltage state in the spark discharge;
Determining means for determining a sweating state of an electrode whose main component is Pt of the spark plug based on comparing the discharge voltage state detected by the detecting means with a reference state;
The ignition apparatus for an internal combustion engine, wherein the spark discharge duration calculation setting means can set an extension of the spark discharge duration based on a determination result of the determination means.

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