JP2016176411A - Ignition device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition device for an internal combustion engine that enables elongation of a service life of a spark plug.SOLUTION: An ignition device 10 for an internal combustion engine includes: a plurality of spark plugs 1 mounted to one combustion chamber of the internal combustion engine; voltage application means 2 for applying voltage to the spark plugs 1; gap determination means 3; and plug selection means 4. The gap determination means 3 determines the size of a discharge gap G between a ground electrode 11 and a center electrode 12 of each of the plurality of spark plugs 1. The plug selection means 4 selects the spark plug 1 to which voltage is applied by the voltage application means 2 on the basis of a determination result obtained by the gap determination means 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ignition device for an internal combustion engine having a plurality of spark plugs.

  An internal combustion engine such as a vehicle is provided with an ignition device that ignites an air-fuel mixture in a combustion chamber by generating a spark discharge in a discharge gap between a ground electrode and a center electrode of a spark plug. Here, the electrode is gradually consumed due to repeated spark discharge, but this consumption affects the life of the spark plug. Therefore, various techniques for suppressing electrode consumption have been proposed.

  Patent Document 1 aims to extend the life of an ignition device in which a plurality of spark plugs having different discharge gaps are arranged in one cylinder by switching spark plugs that are ignited according to the engine speed. Is disclosed.

Japanese Patent No. 4667258

  However, in the ignition device described above, since the electrode of the spark plug on the side where the discharge gap is increased is consumed preferentially, there is room for improvement in extending the life. That is, when the discharge gap is increased, the voltage required between the electrodes is increased, and accordingly, the electrode of the spark plug having the larger discharge gap is likely to be consumed relatively quickly. When at least one of the plurality of spark plugs is worn out, it is a fact that all of the plurality of spark plugs are replaced. Therefore, the uneven consumption of electrodes between the plurality of spark plugs may hinder the extension of the life. Become.

  The present invention has been made in view of such a background, and an object of the present invention is to provide an ignition device for an internal combustion engine capable of extending the life of a spark plug.

One aspect of the present invention is a plurality of spark plugs attached to one combustion chamber in an internal combustion engine;
Voltage applying means for applying a voltage to the spark plug;
Gap determining means for determining the size of the discharge gap between the ground electrode and the center electrode in the plurality of spark plugs;
An ignition device for an internal combustion engine, comprising: a plug selection unit that selects the spark plug to which a voltage is applied by the voltage application unit, based on a determination result of the gap determination unit.

  The ignition device for an internal combustion engine includes a plug selection unit that selects a spark plug to which a voltage is applied by the voltage application unit based on a determination result of the gap determination unit. Therefore, it is possible to prevent uneven consumption of the electrode between the plurality of spark plugs. As a result, the life of the spark plug can be extended.

  As described above, according to the present invention, it is possible to provide an ignition device for an internal combustion engine that can extend the life of a spark plug.

1 is a circuit diagram of an ignition device for an internal combustion engine in Embodiment 1. FIG. FIG. 3 is an operation flowchart of the ignition device for the internal combustion engine in the first embodiment. The side view of the front-end | tip part of the spark plug in Example 1. FIG. FIG. 6 is an operation flowchart of the ignition device for the internal combustion engine in the second embodiment. 4 is a circuit diagram of an ignition device for an internal combustion engine in Embodiment 3. FIG.

Example 1
An embodiment of an ignition device for an internal combustion engine will be described with reference to FIGS.
As shown in FIG. 1, an ignition device 10 for an internal combustion engine includes a plurality of spark plugs 1 attached to one combustion chamber in the internal combustion engine, a voltage application means 2 for applying a voltage to the spark plug 1, and a gap determination means. 3 and plug selection means 4. The gap determination means 3 determines the size of the discharge gap G between the ground electrode 11 and the center electrode 12 in the plurality of spark plugs 1. The plug selection unit 4 selects the spark plug 1 to which the voltage is applied by the voltage application unit 2 based on the determination result of the gap determination unit 3.

The ignition device 10 is used as an ignition means for an air-fuel mixture in an internal combustion engine such as a vehicle engine.
In this example, two spark plugs 1a and 1b are attached to one combustion chamber in the internal combustion engine. The two spark plugs 1a and 1b have the same structure. As shown in FIG. 3, the spark plug 1 includes a center electrode 12 and a ground electrode 11 that are opposed to each other with a discharge gap G provided therebetween. The spark plug 1 also includes an insulator 13 that holds the center electrode 12 inside, and a housing 14 that holds the insulator 13 inside. The two spark plugs 1a and 1b have the same discharge gap G in at least the state before use.

  The ignition device 10 operates the internal combustion engine by discharging at least one of the two spark plugs 1a and 1b and igniting the fuel (air mixture) in the combustion chamber at a predetermined timing. When the spark plug 1 is repeatedly discharged, the center electrode 12 and the ground electrode 11 are gradually consumed. As a result, the life of the spark plug 1 will be exhausted if the discharge gap G is expanded until the discharge gap G is gradually increased and appropriate discharge becomes difficult.

  When two spark plugs 1a and 1b are arranged in one combustion chamber and the two spark plugs 1a and 1b are alternately discharged, simply considering, compared to the case of using one spark plug. Thus, the service life will be doubled. However, even if the two spark plugs 1a and 1b are used alternately, the combustion conditions and the like in each cycle may be different, so the two spark plugs 1a and 1b are not always consumed in the same manner. If the consumption amounts of the two spark plugs 1a and 1b are different from each other, the exhaust gas concentration and the engine output in each cycle may be different, which may cause the emission regulations to not be cleared or cause vibration. In order to overcome these problems, in this example, two spark plugs 1a, 1b can be used as a method for extending the replacement time of the spark plug 1 even if the use environments of the two spark plugs 1a, 1b are different. We propose a method to make the electrode wear rate of the same.

  The ignition device 10 shown in FIG. 1 selects the spark plug 1 to be discharged in each cycle so that the size of the discharge gap G in the two spark plugs 1a and 1b is not biased. As the method, the gap determination means 3 determines the size of the discharge gap G in the two spark plugs 1a and 1b, and the plug selection means 4 selects the spark plug 1 to be discharged based on the determination result.

  In this example, the plug selection means 4 preferentially applies the voltage from the voltage application means 2 to the spark plug 1 that is determined to have the smallest discharge gap G based on the determination result of the gap determination means 3. It is configured to be able to. This prevents the discharge gap G from being biased between the two spark plugs 1a and 1b.

  The voltage application means 2 includes an ignition coil 20 having a primary coil 21 and a secondary coil 22 that are magnetically coupled to each other. The gap determining means 3 is configured to determine the magnitude of the discharge gap G based on the magnitude of the primary voltage applied to the primary coil 21 of the ignition coil 20.

  As shown in FIG. 1, the voltage applying means 2 includes two ignition coils 20a and 20b connected to the spark plugs 1a and 1b, respectively, and two primary coils 21a and 21b connected to the ignition coils 20a and 20b, respectively. Two igniters 23a and 23b. Further, the secondary coil 22a of the ignition coil 20a is connected to the spark plug 1a, and the secondary coil 22b of the ignition coil 20b is connected to the spark plug 1b.

  The primary coil 21 of each ignition coil 20 is repeatedly applied and interrupted with the primary voltage obtained by boosting the voltage of the battery (DC power supply) by the booster circuit 24 as the igniter 23 is turned on / off. Then, when energization of the primary voltage to the primary coil 21 is interrupted, the secondary voltage is induced in the secondary coil 22, and a discharge voltage is applied between the center electrode 12 and the ground electrode 11.

  The igniter 23 is configured by a switching element such as an insulated gate bipolar transistor (IGBT), for example. The IGBT gate of each igniter 23 is connected to the engine control device 5. The igniter 23 switches between conduction and interruption of current between the collector and the emitter based on an ignition control signal input to the gate from the engine control device 5.

  The gap determination means 3 estimates the size of the discharge gap G of one spark plug 1a based on the primary voltage (Va) applied to one primary coil 21a, and the primary applied to the other primary coil 21b. Based on the voltage (Vb), the size of the discharge gap G of the other spark plug 1b is estimated. In order to measure the primary voltages (Va, Vb), a voltage detector 31 is connected between the primary coil 21 and the igniter 23. Information on the primary voltages (Va, Vb) detected by each voltage detector 31 is compared in the comparator 32, and the information is sent to the engine control device 5. The engine control device 5 determines that the discharge gap G of the spark plug 1 connected to the ignition coil 20 having the larger primary voltage is large, and increases the spark plug 1 connected to the ignition coil 20 having the smaller primary voltage to the spark plug 1. The igniter 23 to be operated is selected using the plug selection means 4 in order to apply and discharge the voltage.

  Here, the estimation of the size of the discharge gap G by the gap determination means 3 utilizes Paschen's law. That is, the gap determination means 3 is such that the secondary voltage at which spark discharge occurs between parallel electrodes in the spark plug 1 is such that the gas pressure p in the combustion chamber in which the spark plug 1 is disposed and the discharge gap G of the spark plug 1 are large. This is expressed as a function of the product of d.

  If this method is used, it can be determined that the spark plug 1 having the larger secondary voltage has a larger discharge gap G. Further, the difference in the discharge gap G between the two spark plugs 1a and 1b can be obtained from the difference in secondary voltage between the two ignition coils 20a and 20b. Further, since the primary voltage and the secondary voltage are in a proportional relationship, the difference in the discharge gap G can also be obtained from the value of the primary voltage.

  Since the secondary voltage is as high as several tens of kV, and measurement is difficult, it is easier to detect the primary voltage having a low voltage by the voltage detector 31. In this way, which primary voltage (Va, Vb) of the two ignition coils 20a, 20b is greater and the difference | Va-Vb | The determination means 3 calculates. Based on this calculation result, the plug selection means 4 selects which of the two ignition coils 20a and 20b is to be operated and which spark plug 1 is to be discharged, and the voltage application means 2 applies a voltage to the spark plug 1. Apply.

As described above, since the gap determination means 3 estimates the size of the discharge gap G based on Paschen's law, the gas pressure p in the combustion chamber at the ignition timing is stable when the combustion state is stable. The difference between the discharge gaps G of the two spark plugs 1a and 1b can be estimated with high accuracy from the primary voltage on condition that the constant is at least in two cycles. For example, as a gap determination condition, the air-fuel ratio (A / F) is determined to be close to the theoretical air-fuel ratio, and the engine speed, intake air amount, and ignition timing in each cycle are constant. It is ideal to determine the size of the discharge gap G. Whether the air-fuel ratio is close to the stoichiometric air-fuel ratio can be detected by, for example, an air-fuel ratio sensor or an O ₂ sensor.

Next, an example of how to select the spark plug 1 to be ignited will be described along the flow of FIG.
First, the air-fuel ratio (A / F) of the air-fuel mixture supplied to the combustion chamber is measured by an air-fuel ratio sensor or the like, and it is determined whether or not the obtained air-fuel ratio is close to the theoretical air-fuel ratio (step S1). For example, when the air-fuel ratio (A / F) is in the range of 14 to 15, it is determined that the air-fuel ratio is close to the theoretical air-fuel ratio.

  When it is determined that the air-fuel ratio is not close to the theoretical air-fuel ratio, it is difficult to estimate the appropriate size of the discharge gap G, so that the determination by the gap determining means 3 is not performed. Therefore, in this case, the plug selection means 4 selects the spark plug 1 to be ignited in the same pattern as before (step S2). That is, when one of the spark plugs 1a has been operated so far, the spark plug 1a is continuously operated. Or when the control which switches the spark plugs 1a and 1b to be ignited every several cycles is performed so far, the same control is performed. And it waits for the determination by the gap determination means 3 until it will be in the state close | similar to a theoretical air fuel ratio.

  On the other hand, if it is determined in step S1 that the air-fuel ratio is close to the stoichiometric air-fuel ratio, the gap determination means 3 determines whether or not the difference between the two primary voltages | Va−Vb | S3). If the difference between the two primary voltages | Va−Vb | is equal to or less than a specified value, the two spark plugs 1a and 1b are alternately used while alternately switching the spark plugs 1a and 1b to be ignited every several cycles (step S4). That is, in this case, since the sizes (consumption amounts) of the discharge gaps G of the two spark plugs 1a and 1b are determined to be substantially equal, the two spark plugs 1a and 1b are used equally.

  When it is determined that the difference between the two primary voltages | Va−Vb | exceeds the specified value, the plug selection means 4 selects the spark plug 1 to be ignited as follows. That is, when Va> Vb, the spark plug 1b is selected, and when Va <Vb, the spark plug 1a is selected (steps S5, S6, S7). That is, since the discharge gap G of the spark plug 1 having the smaller primary voltage of the connected ignition coil 20 is estimated to be small (consumed amount is small), the spark plug 1 is used.

  In this way, the ignition device 10 of the present example appropriately selects the spark plug 1 to be ignited. The above determination (determination by the gap determination means 3) is performed at appropriate timing, for example, every predetermined cycle, every predetermined time, or the like.

Next, the function and effect of this example will be described.
The internal combustion engine ignition device 10 includes a plug selection unit 4 that selects a spark plug 1 to which a voltage is applied by the voltage application unit 2 based on a determination result of the gap determination unit 3. Therefore, it is possible to prevent an uneven consumption of the electrode between the two spark plugs 1. As a result, the life of the spark plug 1 can be extended.

  Further, the plug selection unit 4 can preferentially apply the voltage from the voltage application unit 2 to the spark plug 1 that is determined to have the smallest discharge gap G based on the determination result of the gap determination unit 3. It is configured to be able to. Therefore, it is easy to prevent the uneven consumption of the electrode between the two spark plugs 1.

  The gap determination means 3 is configured to determine the size of the discharge gap G based on the size of the primary voltage applied to the primary coil 21 of the ignition coil 20. Thereby, the magnitude | size of the discharge gap G can be determined easily.

  As described above, according to this example, it is possible to provide an ignition device for an internal combustion engine that can extend the life of the spark plug.

(Example 2)
This example is an example in which step S2 in the control flow (FIG. 2) shown in the first embodiment is changed in the ignition control of the spark plugs 1a and 1b as shown in FIG. That is, when it is determined that the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber is not close to the stoichiometric air-fuel ratio, control is performed to simultaneously ignite the two spark plugs 1a and 1b in each cycle (step S2a). And it waits for the determination by the gap determination means 3 until it will be in the state close | similar to a theoretical air fuel ratio.

  Others are the same as in the first embodiment. Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in the first embodiment denote the same components as in the first embodiment unless otherwise specified.

In this example, when the air-fuel ratio of the air-fuel mixture is not close to the stoichiometric air-fuel ratio, that is, when the air-fuel mixture is difficult to ignite, by controlling to ignite the plurality of spark plugs 1a and 1b simultaneously, Ignition can be improved.
In addition, the same effects as those of the first embodiment are obtained.

(Example 3)
In this example, as shown in FIG. 5, the gap determination means 3 takes each spark plug into consideration by comprehensively considering the operation region (rotation speed and load), cumulative operation time, cumulative cycle, cumulative travel distance, etc. of the internal combustion engine. It is the example comprised so that the magnitude | size of the discharge gap G of 1a, 1b might be estimated.

  The consumption amount of the electrode of the spark plug 1a is affected by the operation region, the accumulated operation time, the accumulated cycle, and the accumulated travel distance of the internal combustion engine when the spark plug 1a is operated. The consumption amount of the electrode of the spark plug 1b is affected by the operation region, the accumulated operation time, the accumulated cycle, and the accumulated travel distance of the internal combustion engine when the spark plug 1b is operated. Therefore, in this example, the gap determination means 3 comprehensively considers these pieces of information to determine the size of the discharge gap G of each spark plug 1a, 1b. That is, for example, the amount of electrode consumption is estimated and the size of the discharge gap G is determined according to how much cumulative operating time, cumulative cycle, cumulative travel distance, etc., in which operating region the operation using the spark plug 1a is. presume.

  The gap determination means 3 of this example obtains information such as the operation region, the accumulated operation time, the accumulated cycle, and the accumulated travel distance of the internal combustion engine based on signals from various sensors and the like disposed in each part of the vehicle. When the gap determination means 3 is operated using the one spark plug 1a, the information such as the operation region, the accumulated operation time, the accumulated cycle, the accumulated travel distance, etc. of the internal combustion engine and the other spark plug 1b is operated. The internal combustion engine operating area, cumulative operating time, cumulative cycle, and cumulative travel distance information can be obtained.

  And the gap determination means 3 determines the magnitude | size of the discharge gap G of each spark plug 1a, 1b from the obtained information. The plug selection unit 4 preferentially applies the voltage from the voltage application unit 2 to the spark plug 1 determined that the size of the discharge gap G is smaller (the electrode consumption is smaller) according to the determination result of the gap determination unit 3. It is comprised so that application of can be performed.

Others are the same as in the first embodiment. Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in the first embodiment denote the same components as in the first embodiment unless otherwise specified.
Also in this example, it has the same effect as Example 1.

  In the present embodiment, the information used by the gap determination means 3 does not necessarily have to be all of the operation area, the accumulated operation time, the accumulated cycle, and the accumulated mileage. For example, the gap determination unit 3 may use only information on the operation region and the accumulated operation time. Further, the discharge gap G can be determined by combining information other than the operation region, the accumulated operation time, the accumulated cycle, and the accumulated travel distance.

DESCRIPTION OF SYMBOLS 1, 1a, 1b Spark plug 10 Ignition device 11 Ground electrode 12 Center electrode 2 Voltage application means 3 Gap determination means 4 Plug selection means G Discharge gap

Claims (3)

A plurality of spark plugs (1, 1a, 1b) attached to one combustion chamber in an internal combustion engine;
Voltage application means (2) for applying a voltage to the spark plug (1, 1a, 1b);
Gap determining means (3) for determining the size of the discharge gap (G) between the ground electrode (11) and the center electrode (12) in the plurality of spark plugs (1, 1a, 1b);
Plug selection means (4) for selecting the spark plug (1, 1a, 1b) to which the voltage is applied by the voltage application means (2) based on the determination result of the gap determination means (3). An ignition device (10) for an internal combustion engine.   The plug selection means (4) gives priority to the spark plug (1, 1a, 1b) determined to have the smallest discharge gap (G) based on the determination result of the gap determination means (3). The internal combustion engine ignition device (10) according to claim 1, wherein the voltage application means (2) can be applied with a voltage.   The voltage application means (2) includes an ignition coil (20, 20a, 20b) having a primary coil (21, 21a, 21b) and a secondary coil (22, 22a, 22b) magnetically coupled to each other, The gap determining means (3) determines the magnitude of the discharge gap (G) based on the magnitude of the primary voltage applied to the primary coils (21, 21a, 21b) of the ignition coil (20, 20a, 20b). The ignition device (10) for an internal combustion engine according to claim 1 or 2, wherein the ignition device (10) is configured to determine the safety.

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