JP6427427B2 - Igniter - Google Patents

Description

  The present invention relates to an igniter that repeats a combustion cycle in which a mixture in a combustion chamber of an internal combustion engine is ignited.

  An internal combustion engine such as a vehicle is provided with an igniter that repeats a combustion cycle of igniting a mixture in a combustion chamber. The igniter ignites the mixture in the combustion chamber by generating a spark discharge between the center electrode and the ground electrode of the spark plug. That is, spark discharge is repeatedly generated in the discharge gap between the center electrode and the ground electrode. Since the electrode is gradually consumed by repeated discharges and the consumption rate affects the life of the spark plug, various techniques for suppressing the electrode consumption have been proposed.

  Patent Document 1 proposes an ignition device configured to suppress consumption of electrodes by switching between positive discharge in which the central electrode is a positive electrode and negative discharge in which the central electrode is a negative electrode. That is, the invention of Patent Document 1 focuses on the property that the positive discharge can relatively lower the discharge voltage, but the electrode is easily consumed. Then, in each combustion cycle, after the discharge is started between the center electrode and the ground electrode by the positive discharge, the discharge is switched to the negative discharge to maintain the discharge, thereby suppressing the consumption of the electrode.

JP, 2013-64358, A

  However, in the invention of Patent Document 1, although the discharge is switched to the negative discharge in the middle of the discharge, the positive discharge is generated at the first stage in each combustion cycle. That is, it is difficult to sufficiently suppress the consumption of the electrode because positive discharge is generated in each combustion cycle.

  In addition, in the case of generating a negative discharge when the pressure in the combustion chamber is high, such as in a high supercharge region, discharge in the discharge gap is less likely to occur, and creeping discharge along the surface of the insulator tends to occur. As a result, there is a concern that a misfired combustion cycle will continue, which can be a factor that hinders normal operation of the internal combustion engine.

  Moreover, in the ignition device of Patent Document 1, in order to switch from positive discharge to negative discharge in one combustion cycle, a large discharge current is required when switching to negative discharge. Therefore, there is a problem that the design of the ignition coil, the power supply and the like is restricted, and the degree of freedom in design is lowered.

  The present invention has been made in view of the above background, and it is an object of the present invention to provide an igniter having a high degree of freedom in design that can improve the durability of the spark plug while securing normal operation of the internal combustion engine. It is a thing.

One embodiment of the present invention is an igniter that repeats a combustion cycle in which a mixture in a combustion chamber of an internal combustion engine is ignited,
An ignition plug comprising a center electrode and a ground electrode disposed opposite to each other with a discharge gap therebetween, and an insulator for holding the center electrode inside;
Voltage applying means for applying a voltage between the center electrode and the ground electrode;
Detecting means for detecting whether the discharge generated in the spark plug is a creeping discharge along the surface of the insulator;
The voltage application means may apply a voltage between the center electrode and the ground electrode by switching between a positive discharge voltage in which the central electrode is positive and a negative discharge voltage in which the central electrode is negative. Configured to be able to
While the detection means does not detect the creeping discharge, the voltage application means applies the negative discharge voltage between the center electrode and the ground electrode;
When the detection means detects the creeping discharge, the voltage application means is configured to apply the positive discharge voltage between the center electrode and the ground electrode in a predetermined combustion cycle thereafter. It is in the igniter featured.

  In the above-mentioned igniter, while the detection means does not detect the creeping discharge, the voltage application means applies a negative discharge voltage between the center electrode and the ground electrode. Thereby, spark discharge can be generated in the discharge gap while suppressing consumption of the center electrode and the ground electrode. Note that spark discharge generated in the discharge gap by applying a negative discharge voltage is referred to as “negative discharge”, and spark discharge generated in the discharge gap by applying a positive discharge voltage is referred to as “positive discharge”.

  Then, when the detection means detects the creeping discharge, the voltage application means applies a positive discharge voltage between the center electrode and the ground electrode in a predetermined combustion cycle thereafter. This can prevent the abnormal spark discharge from being repeated in the repeated combustion cycle. That is, when the creeping discharge is detected, in the subsequent predetermined combustion cycle, a positive discharge voltage which hardly causes creeping discharge is applied between the center electrode and the ground electrode. Thus, normal spark discharge in the discharge gap can be immediately recovered, and normal operation of the internal combustion engine can be ensured.

  In addition, switching between the negative discharge voltage and the positive discharge voltage is performed not during the discharge in each combustion cycle but during the combustion cycle, so it is not necessary to supply a particularly large current for switching. Therefore, the design freedom of the igniter can be improved.

  As described above, according to the present invention, it is possible to provide an igniter having a high degree of freedom in design that can improve the durability of the spark plug while ensuring the normal operation of the internal combustion engine.

FIG. 1 is a circuit diagram of an ignition device in a first embodiment. FIG. 2 is a side view of the tip of the spark plug in the first embodiment. FIG. 7 is a diagram showing a voltage waveform of normal discharge in the first embodiment. FIG. 7 is a diagram showing a voltage waveform at the time of creeping discharge in the first embodiment. FIG. 2 is an operation flow diagram of the ignition device in the first embodiment. FIG. 7 is a circuit diagram of an ignition device in a second embodiment.

(Embodiment 1)
An embodiment of the ignition device will be described using FIGS. 1 to 5.
The igniter 1 repeats a combustion cycle in which a mixture in a combustion chamber of an internal combustion engine is ignited.
And, as shown in FIG. 1, the igniter 1 has an ignition plug 2, a voltage application means 3 and a detection means 4.

As shown in FIG. 2, the spark plug 2 is provided with a center electrode 21 and a ground electrode 22 disposed facing each other with a discharge gap therebetween, and an insulator 23 for holding the center electrode 21 inside.
As shown in FIG. 1, the voltage application means 3 is configured to apply a voltage between the center electrode 21 and the ground electrode 22.
The detection means 4 detects whether or not the discharge generated in the spark plug 2 is a creeping discharge along the surface of the insulator 23.

The voltage application means 3 applies a voltage between the center electrode 21 and the ground electrode 22 by switching between a plus discharge voltage in which the center electrode 21 becomes positive and a minus discharge voltage in which the center electrode 21 becomes negative. It is configured to be able to.
While the detection means 4 does not detect the creeping discharge, the voltage application means 3 applies a negative discharge voltage between the center electrode 21 and the ground electrode 22.
When the detection means 4 detects a creeping discharge, the voltage application means 3 applies a positive discharge voltage between the center electrode 21 and the ground electrode 22 in a predetermined combustion cycle thereafter.

The ignition device 1 is used as an ignition means for an air-fuel mixture in an internal combustion engine such as a vehicle engine.
The spark plug 2 is disposed such that its tip projects into the combustion chamber of the internal combustion engine. As shown in FIG. 2, in the spark plug 2, the insulator 23 is held inside the housing 24 screwed to the internal combustion engine, and the center electrode 21 is held inside the insulator 23. The ground electrode 22 has one end joined to the front end of the housing 24 and the other end connected to the center electrode 21 so as to face the center electrode 21 in the axial direction, and the center electrode 21 side of the ground base 220 And a ground protrusion 221 joined to the surface of the substrate. The ground base 220 is made of, for example, a nickel alloy, and the ground projection 221 is made of, for example, a noble metal such as a platinum alloy.

  The central electrode 21 has a central base material 210 held by the insulator 23 and a central projection 211 joined to the tip of the central base material 210. The central base material 210 is made of, for example, a nickel alloy, and the central protrusion 211 is made of, for example, an iridium alloy, a platinum alloy or the like.

As described above, the ignition device 1 has the voltage application means 3 for applying a voltage to the spark plug 2 and the detection means 4 for detecting whether the discharge generated in the spark plug 2 is a creeping discharge.
As shown in FIG. 1, the voltage application means 3 includes an ignition coil 5, a first igniter 61 and a second igniter 62, and an engine control device 12. The ignition coil 5 has two primary coils 511 and 512 and one secondary coil 52.

  Each primary coil 511, 512 is connected to the battery 11, and can conduct current from the battery 11. The primary coils 511, 512 are magnetically coupled to the secondary coil 52 and are mutually inductive with the secondary coil 52. In addition, the two primary coils 511 and 512 are disposed such that the winding directions are opposite to each other. Therefore, the direction of the magnetic field formed by conduction to one of the primary coils 511 and 512 is opposite to the direction of the magnetic field formed by conduction to the other.

  The secondary coil 52 is connected to the spark plug 2 and applies a discharge voltage between the center electrode 21 and the ground electrode 22 by the voltage induced by the secondary coil 52.

  In the above configuration, one primary coil 511 is a primary coil for positive discharge. The positive coil for positive discharge applies a positive discharge voltage from the secondary coil 52 between the center electrode 21 and the ground electrode 22 of the spark plug 2 by interrupting the current flow from the battery 11 every combustion cycle. Voltage is induced in the secondary coil 52, as shown in FIG. The other primary coil 512 is a primary coil for negative discharge. The primary coil 512 for negative discharge is such that a negative discharge voltage is applied from the secondary coil 52 between the center electrode 21 and the ground electrode 22 of the spark plug 2 by interrupting the conduction from the battery 11. A voltage is induced to the next coil 52. The energization and the interruption thereof are performed by switching of the first igniter 61 and the second igniter 62.

  The first igniter 61 and the second igniter 62 are constituted by switching elements such as, for example, insulated gate bipolar transistors (IGBTs). The gate of the IGBT of each igniter 61, 62 is connected to the engine control unit 12. The igniters 61 and 62 switch conduction and interruption of current between the collector and the emitter based on an ignition control signal input from the engine control unit 12 to the gate. The first igniter 61 is connected to the primary coil 511 for positive discharge, and switches the on state and the off state of energization of the primary coil 511 from the battery 11 based on the ignition control signal. Further, the second igniter 62 is connected to the primary coil 512 for negative discharge, and switches on and off states of energization from the battery 11 to the primary coil 512 based on the ignition control signal.

  The engine control unit 12 is a control unit mainly composed of, for example, a microcomputer, and has a flash memory as a storage area and a RAM as a work area of arithmetic processing. The engine control device 12 is connected to an internal combustion engine and various sensors provided in a vehicle equipped with the internal combustion engine. From these sensors, for example, the rotational speed of the output shaft, the temperature of the cooling water, and the intake to the combustion chamber The detection result of the amount of intake air etc. is obtained. The engine control device 12 controls the operation of the internal combustion engine based on the acquired detection result, a control program constructed in advance, a control map defined in advance, and the like. Part of the calculation and control by the engine control device 12 is the detection of the creeping discharge by the detection unit 4 and the control of the voltage application to the spark plug 2 by the voltage application unit 3. The engine control device 12 outputs an ignition control signal for controlling energization of the primary coils 511 and 512 of the ignition coil 5 to the respective igniters 61 and 62.

  The detection means 4 also has a voltmeter 41 for measuring the voltage applied to the spark plug 2. The voltage signal measured by the voltmeter 41 is sent to the engine control unit 12. Thereby, in the engine control device 12, it is detected based on the voltage signal whether or not the discharge generated in the spark plug 2 is a creeping discharge. Therefore, in the present embodiment, the detection means 4 is constituted by the voltmeter 41 and the engine control device 12.

Within each combustion cycle, detection means 4 detects a voltage higher than a predetermined voltage value a plurality of times between center electrode 21 and ground electrode 22 within a predetermined time period from the time when the ignition signal is sent to spark plug 2. When generated, it is configured to determine that the discharge is a creeping discharge. Specifically, for example, when a discharge voltage of 25 kV or more is measured by the voltmeter 41 twice or more in 100 microseconds from the time when the ignition signal is sent, it is determined that the creeping discharge has occurred.
For example, the voltage waveform shown in FIG. 3 is a waveform measured during normal discharge, and the voltage waveform shown in FIG. 4 is a waveform measured when creeping discharge occurs.
In the present embodiment, the time when the ignition signal is sent to the spark plug 2 is the same as the time when the ignition signal is sent from the engine control device 12 to the second igniter 62.

The ignition device 1 provided with the voltage application means 3 and the detection means 4 as described above operates along the flow shown in FIG.
That is, first, the voltage application means 3 applies a negative discharge voltage to the spark plug 2 for each combustion cycle. As a result, spark discharge (minus discharge) is generated in the discharge gap of the spark plug 2 to ignite the mixture, thereby operating the internal combustion engine. Then, the discharge voltage in each combustion cycle is measured one by one (step S1).

  Then, based on the discharge voltage measured for each combustion cycle, it is detected by the detection means 4 whether or not the discharge is a creeping discharge (step S2). If it is determined that the discharge is not creeping discharge, a negative discharge voltage is applied to the ignition coil 2 also in the next combustion cycle (step S1). On the other hand, when it is determined that the discharge is creeping discharge, in the next combustion cycle, a positive discharge voltage is applied to the ignition coil 2 to generate positive discharge (step S3).

Then, positive discharge is repeated a predetermined number of times (n times) of the number of combustion cycles (step S4). Then, after repeating the combustion cycle of positive discharge a predetermined number of times (n times), the combustion cycle is performed again by negative discharge (step S1).
In this manner, the ignition device 1 normally repeats the combustion cycle with negative discharge while monitoring the presence or absence of creeping discharge with the detection means 4, and when creeping discharge is detected, the subsequent predetermined combustion cycle is performed. Perform with positive discharge.

Next, the operation and effect of the present embodiment will be described.
In the igniter 1, while the detection means 4 does not detect creeping discharge, the voltage application means 3 applies a negative discharge voltage between the center electrode 21 and the ground electrode 22. Thereby, spark discharge can be generated in the discharge gap while suppressing consumption of the center electrode 21 and the ground electrode 22.

  Then, when the detection means 4 detects a creeping discharge, the voltage application means 3 applies a positive discharge voltage between the center electrode 21 and the ground electrode 22 in a predetermined combustion cycle thereafter. This can prevent the abnormal spark discharge from being repeated in the repeated combustion cycle. That is, when the creeping discharge is detected, in the subsequent predetermined combustion cycle, a positive discharge voltage which hardly causes the creeping discharge is applied between the center electrode 21 and the ground electrode 22. Thus, normal spark discharge in the discharge gap can be immediately recovered, and normal operation of the internal combustion engine can be ensured.

  Further, switching between the negative discharge voltage and the positive discharge voltage is performed not during the discharge in each combustion cycle but during the combustion cycle, so it is not necessary to supply a particularly large current for switching. Therefore, the design freedom of the ignition device 1 can be improved.

  Further, in each combustion cycle, the detection means 4 has a voltage higher than a predetermined voltage value between the center electrode 21 and the ground electrode 22 within a predetermined time from the time when the ignition signal is sent to the spark plug 2. When generated a plurality of times, it is configured to determine that the discharge is a creeping discharge. Thereby, it can be detected easily and correctly whether it is creeping discharge or not.

  As described above, according to the present embodiment, it is possible to provide an igniter having a high degree of freedom in design that can improve the durability of the spark plug while ensuring the normal operation of the internal combustion engine.

Second Embodiment
In the present embodiment, as shown in FIG. 6, the circuit configuration of the voltage application means 3 is modified from that of the first embodiment.
That is, in the present embodiment, as the ignition coil 5 constituting the voltage application means 3, one formed of one primary coil 51 and one secondary coil 52 is used. The high potential side terminal 521 and the low potential side terminal 522 of the secondary coil 52 are configured to be connected to the spark plug 2 via the switches 31 and 32, respectively. The switch 31 is configured to be able to switch the connection destination of the high potential side terminal 521 between the spark plug 2 and the ground (ground). Further, the switch 32 is configured to be able to switch the connection destination of the low potential side terminal 522 between the spark plug 2 and the ground (ground). Note that the high potential side terminal 521 is a terminal that becomes the high potential side when a voltage is induced in the secondary coil 52 along with the interruption of the energization to the primary coil 51, and the low potential side terminal 522 is on the opposite side. It is a terminal.

  Therefore, when applying a negative discharge voltage to the spark plug 2, the high potential side terminal 521 is connected to the ground, and the low potential side terminal 522 is connected to the spark plug 2 (state of FIG. 6). In this state, by switching the igniter 6 from energization to interruption, a negative discharge voltage is induced in the secondary coil 52 and applied to the spark plug 2.

  On the other hand, when applying a positive discharge voltage to the spark plug 2, the low potential side terminal 522 is connected to the ground, and the high potential side terminal 521 is connected to the spark plug 2. In this state, a positive discharge voltage is induced in the secondary coil 52 and switched to the spark plug 2 by switching the igniter 6 from energization to interruption.

Thus, the negative discharge voltage and the positive discharge voltage can be appropriately selected and applied to the spark plug 2. The selective use of the negative discharge and the positive discharge is performed based on the detection result of the detection means 4 as in the first embodiment.
Others are the same as in the first embodiment. The same reference numerals as those in the first embodiment denote the same constituent elements and the like, and reference is made to the preceding description.

In the present embodiment, the configuration of the transformer 5 can be simplified and the number of igniters can be reduced.
In addition, it has the same operation effect as Embodiment 1.

  As mentioned above, although embodiment of this invention was described, respectively, this invention is not limited to said each embodiment, It is possible to apply to various embodiment in the range which does not deviate from the summary. For example, when the detection means detects a creeping discharge, it does not necessarily switch from the next combustion cycle to the positive discharge voltage of the combustion cycle, for example, it may switch from the next combustion cycle to the next combustion cycle . In addition, the circuit configuration of the voltage application means may be different from that shown in the above embodiment.

DESCRIPTION OF SYMBOLS 1 Ignition device 2 Spark plug 21 Center electrode 22 Ground electrode 23 Insulator 3 Voltage application means 4 Detection means

Claims (2)

An igniter (1) for repeating a combustion cycle of igniting a mixture in a combustion chamber of an internal combustion engine, comprising:
A spark plug (2) comprising: a center electrode (21) and a ground electrode (22) disposed facing each other with a discharge gap therebetween; and an insulator (23) for holding the center electrode (21) inside )When,
Voltage applying means (3) for applying a voltage between the center electrode (21) and the ground electrode (22);
And detecting means (4) for detecting whether the discharge generated in the spark plug (2) is a creeping discharge along the surface of the insulator (23),
The voltage application means (3) switches between the positive electrode in which the central electrode (21) is positive and the negative electrode in which the central electrode (21) is negative to switch between the central electrode (21) and the positive electrode. It is configured to be able to apply a voltage between it and the ground electrode (22),
While the detection means (4) does not detect the creeping discharge, the voltage application means (3) applies the negative discharge voltage between the center electrode (21) and the ground electrode (22). ,
When the detection means (4) detects the creeping discharge, the voltage application means (3) generates the positive discharge voltage and the central electrode (21) and the ground electrode (22) in a predetermined combustion cycle thereafter. An igniter (1), characterized in that it is adapted to be applied between.   In each combustion cycle, the detection means (4) detects a voltage higher than a predetermined voltage value with the center electrode (21) within a predetermined time from the time when the ignition signal is sent to the spark plug (2). The igniter (1) according to claim 1, characterized in that the discharge is determined to be a creeping discharge when generated a plurality of times between the ground electrode (22) and the ground electrode (22).

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