JP2009019612A - Spark plug system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark plug system capable of regenerating electrodes, by surely diagnosing sticking or deposition of soot to the electrodes of a spark plug for assisting starting of a diesel engine. <P>SOLUTION: This spark plug system 1 has the spark plug 2 arranged by facing a combustion chamber 11 of the diesel engine 10 for assisting the starting of the diesel engine 10, and has a diagnostic means for diagnosing whether or not the soot sticks and deposits on the electrodes 21 and 22 of the spark plug 2 when idly operating the diesel engine 10, and a regenerating means for regenerating the electrodes 21 and 22 by burning off the stuck-deposited soot by imposing voltage on the electrodes 21 and 22 based on a diagnostic result of its diagnostic means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a spark plug system that diagnoses and regenerates soot adhesion and accumulation on a spark plug that assists in starting a diesel engine.

  In recent years, some technologies that use spark plugs as ion sensors have been put into practical use. According to the spark plug system, the engine can have a direct detection sensor for each cylinder instead of an indirect detection sensor such as a conventional vibration knock sensor. The ion sensor using the spark plug is used for determining misfire and knocking by cylinder in a gasoline engine or the like, and is expected as a sensor that can make the control more reliable.

Here, the mechanism of the ionic current captured after ignition and during combustion will be explained. In the combustion process, ions such as CHO + and H ₃ O + are present in the vicinity of the flame if it is a hydrocarbon fuel due to the chemical reaction of the fuel composition. It has been known. This change in ion concentration is detected as an ion current as ions and electrons move due to the DC voltage applied between the spark plug electrodes.

  Further, Patent Document 1 proposes a combustion state detection device that detects a combustion state in a combustion chamber based on an ion current detected by a glow plug.

  By the way, research on premixed compression ignition combustion that enables simultaneous reduction of low NOx and low smoke in a diesel engine has been actively conducted in recent years. Because the premixed compression ignition engine generates and burns a uniform and lean premixed gas at an early stage, increasing the engine load as a technical problem makes premature ignition difficult and makes it difficult to control the ignition timing. There is a problem that it is limited to a low load region. Therefore, there is a need for an appropriate sensor that can perform combustion diagnosis for each cylinder.

  Therefore, it is conceivable to apply the above-described spark plug system having the ion sensor function to the combustion diagnosis of each cylinder.

JP 11-44285 A

  However, when the spark plug system having the ion sensor function described above is used in a diesel engine, the ionic current to be detected is weak (on the order of μA), so that the soot peculiar to the diesel engine adheres to or accumulates between the electrodes. Then, there is a concern that the sensor function may be impaired.

  Further, in the combustion state detection device of Patent Document 1, when soot (carbon) adheres to the glow plug, the soot is heated and removed. In the spark plug system, the start of the diesel engine is aided by the spark plug. Therefore, the glow plug is omitted, and heat removal of the soot by the glow plug cannot be employed.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a spark plug system that solves the above-mentioned problems and can reliably diagnose the adhesion or accumulation of soot on the electrode of a spark plug that assists the start of a diesel engine to regenerate the electrode. Is to provide.

  In order to achieve the above object, the present invention provides a spark plug system including a spark plug provided facing a combustion chamber of a diesel engine so as to assist the start of the diesel engine. Based on the diagnostic result of the diesel engine during idling operation of the diesel engine and the diagnosis result of the diagnostic means, the electrode is applied to the electrode and burnt off the adhered / deposited soot. And reproducing means for reproducing.

  Preferably, provided with a soot amount detecting means for detecting the amount of soot adhering to and accumulating on the electrode, the diagnostic means has an amount of soot detected by the soot amount detecting means exceeding a predetermined soot amount. Sometimes, it is diagnosed that the electrode needs to be regenerated, and the regenerating means regenerates the electrode.

  Preferably, the regeneration means performs regeneration of the electrode in the latter half of the expansion stroke or the exhaust stroke of the diesel engine.

  Preferably, there is provided an ion current detecting means for detecting an ion current flowing between the electrodes of the spark plug due to fuel combustion during operation of the diesel engine.

  Preferably, an ion current detecting means for detecting an ionic current flowing between the electrodes of the spark plug due to fuel combustion during operation of the diesel engine is provided, the ionic current detecting means forming the soot amount detecting means, The diagnosis means that when the ion current detected by the ion detection means is less than or equal to a predetermined ion current value, the amount of soot adhered to and deposited on the electrode exceeds a predetermined soot amount and the electrode needs to be regenerated. Diagnosis is made, and the regeneration means regenerates the electrode.

  ADVANTAGE OF THE INVENTION According to this invention, the outstanding effect that the adhesion | attachment or accumulation | storage of the soot to the electrode of the spark plug which assists starting of a diesel engine can be diagnosed reliably, and an electrode can be reproduced | regenerated is exhibited.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  The spark plug system of this embodiment is applied to, for example, a multi-cylinder diesel engine mounted on a vehicle.

  First, a schematic structure of a diesel engine (hereinafter referred to as an engine) will be described with reference to FIG.

  As shown in FIG. 4, the engine 10 includes a combustion chamber 11 (only one is shown in FIG. 1) provided in each cylinder, an injector 12 for injecting and supplying fuel to the combustion chamber 11, A spark plug 2 for igniting fuel from the injector 12 at the time of cold start or the like to assist the start of the engine 10, and a control means (hereinafter referred to as a controller) 4 for controlling the injector 12 and the spark plug 2; Is provided.

  The combustion chamber 11 is formed by a cylinder head 13, a cylinder bore 15 formed in the cylinder block, and a piston 16 accommodated in the cylinder bore 15. An intake port 17 and an exhaust port 18 formed in the cylinder head 13 are connected to the combustion chamber 11.

  The injector 12 is provided in the cylinder head 13 with the fuel injection nozzle 121 facing the combustion chamber 11. The injector 12 is connected to the controller 4, and the controller 4 controls the fuel injection amount and the fuel injection timing.

  The spark plug 2 is provided on the cylinder head 13 with electrodes 21 and 22 described later facing the combustion chamber 11. In the engine 10 of the present embodiment, the glow plug is omitted because the spark plug 2 is used as a starting auxiliary device, and the spark plug 2 is disposed at the position of the glow plug in the conventional diesel engine. For example, the spark plug 2 is attached so that the electrodes 21 and 22 are positioned in the vicinity of the fuel spray injected from the fuel injection nozzle 121.

  The spark plug 2 is connected to an electric circuit 3 for supplying voltage (electricity) to the spark plug 2, and the electric circuit 3 is connected to a controller 4. The spark plug 2 is controlled by the controller 4 through the electric circuit 3 in synchronization with an engine rotation signal (engine rotation speed) from the cam sensor 14.

  The spark plug 2, the electric circuit 3, and the controller 4 constitute a spark plug system 1.

  Next, the schematic structure of the spark plug system 1 will be described with reference to FIG.

  As shown in FIGS. 1 and 4, the spark plug system 1 includes the spark plug 2, the electric circuit 3, and the controller 4.

  The electrode of the spark plug 2 includes a center electrode 21 and a ground electrode 22 that perform a spark discharge with a high voltage supplied from the electric circuit 3. The center electrode 21 and the ground electrode 22 are arranged in the combustion chamber 11 with a predetermined interval (gap) therebetween.

  In the present embodiment, during operation of the diesel engine, a voltage (a voltage that does not cause spark discharge) is applied between the center electrode 21 and the ground electrode 22, so that the center electrode 21 and the ground are grounded during fuel ignition / combustion. An ion current flowing through the electrode 22 is detected.

  That is, the electrodes 21 and 22 of the spark plug 2 are used as sensor probes, and the electric circuit 3 detects ions that flow between the electrodes 21 and 22 of the spark plug 2 by the combustion of fuel when the engine 10 is in operation. Provides current detection means.

  In the electric circuit 3, 31 is a primary coil, 32 is a secondary coil, 33 is a switch, D1 is a first Zener diode, D2 is a second Zener diode, C1 is a capacitor, R1 is a first resistor, and R4 is a second coil. Resistance. Primary coil 31 is connected to battery 19 of engine 10.

  When performing the spark discharge, the switch 33 is turned on (energized), the primary current flows from the battery 19 to the primary coil 31, and then the switch 33 is turned off (cut off) so that the secondary coil 32 is secondary. A voltage (high voltage) is generated. The secondary voltage is applied between the center electrode 21 and the ground electrode 22, and spark discharge is performed between the electrodes 21 and 22. At this time, the capacitor C1 is charged.

  When detecting the ion current, the voltage charged in the capacitor C <b> 1 is applied between the center electrode 21 and the ground electrode 22. When the fuel burns in a state where a voltage is applied between the electrodes 21 and 22, an ion current flows between the center electrode 21 and the ground electrode 22 as shown by a white arrow in FIG. A current is detected as an ion signal (ion current value signal) between the first resistor R1 and the second resistor R4. The detected ion signal is input to the controller 4.

  The controller 4 obtains the combustion state (ignition timing, etc.) of the engine 10 based on the ionic current from the electric circuit 3, and controls the engine 10 according to the combustion state. For example, when performing premixed compression ignition combustion, the controller 4 performs ignition control on the fuel injection timing and the fuel injection amount of the injector 12 (see FIG. 4) so that the ignition timing obtained from the ionic current coincides with the target ignition timing. To do.

  Here, in the diesel engine 10, soot tends to be generated, and if the soot adheres to and accumulates on the center electrode 21 or the ground electrode 22 of the spark plug 2, there is a possibility that the ion current cannot be detected accurately.

  Therefore, the spark plug system 1 of the present embodiment includes a diagnostic means for performing a diagnosis of whether or not soot has adhered to and accumulated on the center electrode 21 and / or the ground electrode 22 of the spark plug 2 during idle operation of the engine 10; Regenerating means for regenerating the electrodes 21 and 22 based on the diagnosis result of the diagnosing means. In the present embodiment, the controller 4 serves as a diagnosis unit and a reproduction unit.

  The regeneration of the electrodes 21, 22 is performed by the controller 4 being attached and deposited by applying a high voltage for spark discharge to the center electrode 21 and the ground electrode 22 by the primary coil 31 and the secondary coil 32 of the electric circuit 3. It is done by burning out.

  The controller 4 (diagnosis means, regeneration means) diagnoses that it is necessary to regenerate the electrodes 21 and 22 when the amount of soot detected by the soot amount detection means described later exceeds a predetermined soot amount. , 22 is reproduced.

  More specifically, the electric circuit 3 (ion current detecting means) constitutes soot amount detecting means for detecting the amount of soot adhering to and depositing on the electrodes 21 and 22, and the controller 4 (diagnostic means, regenerating means). When the ionic current detected by the electric circuit 3 is less than or equal to a predetermined ionic current value (hereinafter referred to as a threshold value), the amount of soot adhering to and depositing on the electrodes 21 and 22 exceeds the predetermined soot amount. , 22 is diagnosed and regeneration of the electrodes 21 and 22 is performed.

  The controller 4 (regeneration means) regenerates the electrodes 21 and 22 in the latter half of the expansion stroke or the exhaust stroke of the diesel engine 10.

  Next, the operation of the spark plug system 1 of the present embodiment will be described based on FIGS. 2 and 3.

  A spark plug system 1 of the present embodiment shown in FIGS. 1 and 4 has a start assist function of the diesel engine 10 and an ion sensor function for the purpose of direct combustion diagnosis and control for each cylinder, and further includes a spark plug 2. It has a diagnosis / regeneration function for diagnosing and regenerating (removing and printing out the soot) the soot adhering and depositing between the electrodes 21 and 22 under predetermined conditions (diagnostic conditions).

  In the start assist function, the controller 4 synchronizes with the fuel injection timing of the engine 10 for start assist at the start of the engine 10 (for example, at the time of cold start), and at a predetermined time and predetermined energy. 2 is sparked to ignite the fuel.

  When ignition is completed, the controller 4 switches the electric circuit 3 and uses the spark plug 2 as a probe of the ion sensor to directly detect the combustion state for each cylinder during operation of the engine 10 (ion sensor function). Specifically, the detection of the combustion state is performed by detecting the pressure in the combustion chamber 11 (hereinafter referred to as cylinder internal pressure).

  Based on FIG. 2, the relationship between the ion current detected by the electric circuit 3 and the pressure in the cylinder will be described.

  In FIG. 2, the horizontal axis represents the crank angle (deg. CA), and the vertical axis represents the cylinder internal pressure (MPa) and the ionic current (μA). A line ION indicates an ionic current detected by the electric circuit 3. Line P indicates the cylinder pressure detected by attaching a cylinder pressure sensor to the engine. The dotted line indicates an ignition event.

  As shown in FIG. 2, the cylinder internal pressure P reaches the peak after the compression top dead center, and the ion current ION similarly reaches the peak at substantially the same crank angle. In the vicinity of the peak, the cylinder internal pressure P and the ionic current ION show a similar tendency (waveform).

  From this, the pressure in the cylinder can be detected by the ion current, and the ignition timing and the like can be obtained from the peak of the pressure in the cylinder.

  Here, when detecting the combustion state, soot peculiar to the diesel engine adheres or accumulates on the center electrode 21 and / or the ground electrode 22 of the spark plug 2 and stable ion current cannot be detected. It is necessary to detect and diagnose abnormalities under predetermined conditions.

  In the engine 10 that is operated in a wide operation region (engine rotation speed / engine load), the combustion state that is always determined can be detected during idle operation. Therefore, in the present embodiment, the diagnosis timing (predetermined condition) for performing the soot diagnosis is set when the engine 10 is idling.

  Based on FIG. 3, the diagnosis of wrinkles and the regeneration of the electrodes 21 and 22 will be described in detail.

  The horizontal axis in FIG. 3 represents the crank angle (deg. CA). The uppermost part of FIG. 3 shows the ion current detected by the electric circuit 3 and the ignition event. In the uppermost stage, the line N is a normal ion current waveform, the line A is an abnormal ion current waveform with soot adhering to the electrodes 21 and 22, and the dotted line is a waveform due to an ignition event. The second stage shows a fuel injection signal input from the controller 4 to the injector 12. In the illustrated example, fuel injection is performed in two stages. The third stage and the fourth stage indicate the ignition injection energy input to the spark plug 2, the third stage indicates the normal time, and the fourth stage indicates the time when the soot is attached (regeneration).

  The threshold value T is obtained and set in advance from an ionic current value that is stably obtained under idle operation in a state where no soot is attached to the spark plug 2 by experiments or the like. The threshold value is stored in the controller 4, for example.

  As shown in FIGS. 1 and 4, first, when sending a fuel injection signal to the injector 12 in the compression stroke, the controller 4 turns on the switch 33 of the electric circuit 3 to charge the capacitor C1 of the electric circuit 3. The spark plug 2 is turned off and the ignition charge energy is applied to the spark plug 2 so that no spark discharge occurs.

  Next, the controller 4 determines whether or not the ionic current detected from the electric circuit 3 is below (below) the threshold value T.

  As shown by line A in FIG. 3, when soot adheres to the electrodes 21 and 22, the ionic current detected by the electric circuit 3 is generally lower than the normal line N, and in particular, the compression process. The peak of the ionic current in the second half or the first half of the expansion stroke is below the threshold value T.

  Thus, when the peak of the ion current falls below the threshold value T, the controller 4 burns and regenerates the soot adhering to the electrodes 21 and 22, so that it does not affect the combustion of the engine 10 in the latter half of the expansion stroke. Alternatively, during the exhaust stroke, a high voltage is applied between the electrodes 21 and 22 so that a spark discharge is generated.

  In the illustrated example, the controller 4 inputs more energy in the latter half of the expansion stroke than when the capacitor C1 is charged. Further, the controller 4 repeatedly inputs energy for regeneration over a plurality of cycles until the ion current detected from the electric circuit 3 becomes equal to or less than the threshold value T (regeneration mode).

  Thereafter, when the ion current detected from the electric circuit 3 exceeds (exceeds) the above-described threshold value T, the controller 4 stops the regeneration mode.

  As described above, in the present embodiment, the spark plug system 1 having an ion sensor function for the purpose of assisting the starting of the diesel engine 10 and direct combustion state diagnosis and control for each cylinder is provided between the electrodes 21 and 22 of the spark plug 2. By controlling the diagnosis and regeneration (removal and firing) of soot that adheres to and accumulates on a predetermined condition, variations in ion current detected between the electrodes 21 and 22 are suppressed, and stable direct by cylinder Combustion diagnosis can be performed and reflected in combustion control.

  That is, the spark plug system 1 according to the present embodiment diagnoses and regenerates (removes and burns out the soot) the soot that adheres to and deposits between the electrodes 21 and 22 of the spark plug 2. Is determined during idle operation, and whether or not regeneration is necessary is determined when the amount of soot adhering and depositing exceeds a predetermined amount of soot, and when the ion sensor function is provided, the determination is made based on the ion current of the ion sensor ( Or when the voltage is below a predetermined value.

  Thus, by performing the diagnosis of soot adhesion or deposition on the electrodes 21 and 22 of the spark plug 2 during the idle operation, the diagnosis can be surely performed, and the electrodes 21 and 22 can be appropriately regenerated. .

  In addition, by setting the regeneration period to the latter half of the expansion stroke or the exhaust stroke, regeneration is performed in a state where there is no combustible gas in the combustion chamber, and burned soot is quickly removed from the combustion chamber in the exhaust stroke. As a result, regeneration can be performed without affecting the combustion of the engine 10.

  In addition, this invention is not limited to the above-mentioned embodiment, Various modifications and application examples can be considered.

FIG. 1 is a schematic configuration diagram of a spark plug system according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between ion current and cylinder pressure. FIG. 3 is a view for explaining the operation of the spark plug system of the present embodiment. FIG. 4 is a schematic configuration diagram of the diesel engine of the present embodiment.

Explanation of symbols

1 Spark plug system 2 Spark plug 3 Electrical circuit (ion current detection means)
4 Controller (diagnosis means, regeneration means)
10 Diesel engine 11 Combustion chamber 21 Center electrode 22 Ground electrode

Claims (5)

In a spark plug system comprising a spark plug provided facing a combustion chamber of the diesel engine to assist the start of the diesel engine,
Diagnosis means for determining whether soot has adhered to or accumulated on the spark plug electrode during the idling operation of the diesel engine, and applying the voltage to the electrode based on the diagnosis result of the diagnosis means A spark plug system comprising: a regeneration means for burning off the accumulated soot and regenerating the electrode. Equipped with soot detection means for detecting the amount of soot adhering to and depositing on the electrode,
The diagnostic means diagnoses that the electrode needs to be regenerated when the amount of soot detected by the soot amount detecting means exceeds a predetermined soot amount, and the regeneration means regenerates the electrode. Item 2. A spark plug system according to item 1.   The spark plug system according to claim 1 or 2, wherein the regeneration means performs regeneration of the electrode in the latter half of the expansion stroke or the exhaust stroke of the diesel engine.   The spark plug system according to any one of claims 1 to 3, further comprising an ion current detecting means for detecting an ion current flowing between electrodes of the spark plug due to fuel combustion during operation of the diesel engine. Comprising an ion current detection means for detecting an ion current flowing between the electrodes of the spark plug by the combustion of fuel during operation of the diesel engine, the ion current detection means comprising the soot amount detection means,
When the ion current detected by the ion detection means is less than or equal to a predetermined ion current value, the diagnostic means needs to regenerate the electrode because the amount of soot attached to and deposited on the electrode exceeds a predetermined amount The spark plug system according to claim 2, wherein the regeneration means regenerates the electrode.

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