JP7363438B2 - Ignition system for internal combustion engines - Google Patents

Description

The present invention relates to an ignition device for an internal combustion engine.

The ignition device disclosed in Patent Document 1 applies high voltage and high frequency to the spark plug immediately before ignition to generate ions around the discharge gap of the spark plug and raise the electrode temperature. This attempts to suppress the required voltage necessary for discharge in the discharge gap.

Patent No. 2524699

However, in the configuration disclosed in Patent Document 1, since a high voltage is applied immediately before the main discharge, there is a fear that premature ignition may occur before the main discharge depending on the operating conditions.

The present invention has been made in view of such problems, and an object thereof is to provide an ignition device for an internal combustion engine that can improve ignition performance while preventing early ignition.

One aspect of the present invention includes a cylindrical insulator (31), and a center electrode (32) held inside the insulator and having a tip protrusion (321) protruding from the tip side of the insulator. , a cylindrical housing (33) that holds the insulator on the inner circumferential side, and a ground electrode (331) that is connected to the housing and forms a discharge gap (G) between it and the tip protrusion. a spark plug (3) having;
The initial stage of the intake stroke of the internal combustion engine (2) equipped with the spark plug, the timing at which the intake valve (21) of the internal combustion engine opens and the timing at which the exhaust valve (22) of the internal combustion engine closes. , the preliminary discharge is performed after the later timing (T0),
The preliminary discharge is configured to be performed between the timing when the intake valve opens and the timing when the exhaust valve closes, whichever is later, until a period corresponding to a crank angle of 40 degrees has elapsed. Ori,
After performing the preliminary discharge, the main discharge is performed to ignite the air-fuel mixture,
The internal combustion engine has an intake port (210) equipped with the intake valve, and the internal combustion engine is a port injection type internal combustion engine in which fuel is injected into the intake port. 1).

The above-mentioned ignition device for an internal combustion engine is configured to perform preliminary discharge at an early stage of the intake stroke. Therefore, it is possible to suppress the risk of early ignition of the air-fuel mixture due to preliminary discharge. Further, the ignition device is configured to perform the preliminary discharge after the later of the timing when the intake valve opens and the timing when the exhaust valve closes. Therefore, by efficiently generating excited gas molecules through the preliminary discharge, the required voltage for the main discharge can be lowered. As a result, ignitability can be improved.

As described above, according to the above aspect, it is possible to provide an ignition device for an internal combustion engine that can improve ignition performance while preventing early ignition.
Note that the numerals in parentheses described in the claims and means for solving the problem indicate correspondence with specific means described in the embodiments described later, and do not limit the technical scope of the present invention. It's not a thing.

1 is a sectional view of a spark plug in Embodiment 1. FIG. 1 is a schematic configuration diagram of an ignition device in Embodiment 1. FIG. 1 is a cross-sectional view of the internal combustion engine before an intake valve opens in Embodiment 1. FIG. 1 is a cross-sectional view of the internal combustion engine after an intake valve is opened in Embodiment 1. FIG. 1 is a cross-sectional view of the internal combustion engine at a stage when a rich air-fuel mixture reaches a discharge gap in Embodiment 1. FIG. 7 is a graph showing the relationship between the timing of starting preliminary discharge and the required voltage reduction effect in Embodiment 1. FIG. 7 is a graph showing the relationship between the timing of preliminary discharge start and the required voltage reduction effect when the opening of the intake valve is delayed in Embodiment 1. FIG. 7 is a graph showing the relationship between the timing of preliminary discharge start and the required voltage reduction effect when the opening of the intake valve is advanced in Embodiment 1. FIG. FIG. 3 is a diagram of the internal combustion engine before the intake valve opens according to a simulation in Embodiment 1; FIG. 3 is a diagram of the internal combustion engine after the intake valve is opened according to a simulation in Embodiment 1; FIG. 3 is a diagram of the internal combustion engine at a stage when a simulated rich air-fuel mixture reaches a discharge gap in Embodiment 1; 7 is a graph showing the secondary current of the ignition coil in Embodiment 2. 7 is a graph showing the relationship between the short circuit frequency of preliminary discharge and the required voltage reduction effect in Embodiment 2. FIG. 3 is a schematic configuration diagram of an ignition device in Embodiment 3. 7 is a diagram showing a relationship between each operating condition and an estimated required voltage value in Embodiment 3. FIG. FIG. 7 is a flowchart of control by a preliminary discharge control section in Embodiment 3.

(Embodiment 1)
An embodiment of an ignition device for an internal combustion engine will be described with reference to FIGS. 1 to 5.
The ignition device 1 of this embodiment has a spark plug 3. As shown in FIG. 1, the spark plug 3 includes a cylindrical insulator 31, a center electrode 32, a cylindrical housing 33, and a ground electrode 331. The center electrode 32 is held inside the insulator 31 and has a tip protrusion 321 protruding from the tip side of the insulator 31 . The housing 33 holds the insulator 31 on the inner peripheral side. The ground electrode 331 is connected to the housing 33 and forms a discharge gap G between the ground electrode 331 and the tip protrusion 321 .

The spark plug 3 is provided in the internal combustion engine 2, as shown in FIG. The ignition device 1 is activated at the initial stage of the intake stroke of the internal combustion engine 2, after the later timing of the timing when the intake valve 21 of the internal combustion engine 2 opens and the timing when the exhaust valve 22 of the internal combustion engine 2 closes. The device is configured to perform a preliminary discharge.
Note that the later timing of the timing at which the intake valve 21 of the internal combustion engine 2 opens and the timing at which the exhaust valve 22 of the internal combustion engine 2 closes is also referred to as timing T0 below.

Further, in this specification, as shown in FIG. 1, in the direction in which the central axis C of the spark plug 3 extends, the side disposed within the main combustion chamber 23 is referred to as the distal end side, and the opposite side is referred to as the proximal end side.

In the spark plug 3 of this embodiment, a ground electrode 331 is connected to the front end side of the housing 33. In this embodiment, the ground electrode 331 is fixed by welding its proximal end to the distal end of the housing 33.

Further, the housing 33 has a mounting screw portion 332 for mounting the spark plug 3 to the cylinder head 25 of the internal combustion engine 2, as shown in FIG. The spark plug 3 is attached to the internal combustion engine 2 by screwing the mounting screw portion 332 of the housing 33 into the female screw hole 251 provided in the cylinder head 25, as shown in FIG.

Next, the internal combustion engine 2 equipped with the spark plug 3 will be explained.
The internal combustion engine 2 of this embodiment includes a cylinder head 25, a cylinder block 26, and a piston 24 that reciprocates within a cylinder 240, as shown in FIG. A main combustion chamber 23 is formed surrounded by the cylinder head 25, cylinder block 26, and piston 24. The cylinder head 25 is formed with an intake port 210 and an exhaust port 220, and is provided with an intake valve 21 and an exhaust valve 22, respectively. A spark plug 3 is attached between an intake port 210 and an exhaust port 220 in the cylinder head 25. The internal combustion engine 2 of this embodiment is a port injection type internal combustion engine 2 in which fuel is injected into an intake port 210.

Further, the tip of the spark plug 3 is exposed to the main combustion chamber 23. That is, the discharge gap G provided at the tip side of the spark plug 3 is exposed to the main combustion chamber 23.

Further, due to the reciprocating movement of the piston 24, the volume of the main combustion chamber 23 changes from time to time. Due to the reciprocating movement of the piston 24, the internal combustion engine 2 sequentially repeats a cycle of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The internal combustion engine 2 of this embodiment is a four-stroke engine.

More specifically, during the intake stroke, the piston 24 moves down and the intake valve 21 opens, so that the air-fuel mixture containing fuel flows into the main combustion chamber 23 from the intake port 210. Then, the intake valve 21 closes, and in the compression stroke, the piston 24 moves up to the top dead center, thereby compressing the intake air-fuel mixture. The compressed air-fuel mixture is ignited by the main discharge from the spark plug 3 and combusted, and the piston 24 is pushed down to the bottom dead center as the combusted air-fuel mixture expands. Next, in the exhaust stroke, the depressed piston 24 rises due to inertia, the exhaust valve 22 opens, and the combusted air-fuel mixture is forced out of the main combustion chamber 23 through the exhaust port 220. Then, the exhaust valve 22 closes, the intake valve 21 opens, and the piston 24 lowers, leading to an intake stroke in which the air-fuel mixture flows into the main combustion chamber 23, and the same stroke is repeated.

Preliminary discharge is performed during the initial period of the intake stroke. Here, the initial stage of the intake stroke refers to a period from the opening of the intake valve 21 to, for example, 90° CA (crank angle) or less. In this embodiment, the preliminary discharge is performed from timing T0 until the initial period of the intake stroke has elapsed. In other words, the timing T0 is also the start timing of the state in which only the intake valve 21 is open.

In the internal combustion engine 2 of this embodiment, immediately before the intake stroke starts and before the intake valve 21 opens, the rich mixture R, which is the mixture containing a large amount of fuel, flows into the intake port 210 as shown in FIG. exist. Then, as shown in FIG. 4, when the intake valve 21 opens, the rich air-fuel mixture R flows into the main combustion chamber 23. Thereafter, after a predetermined period of time has elapsed from timing T0, the rich mixture R reaches the discharge gap G of the spark plug 3, as shown in FIG.

As will be described later in evaluation test 4, the preliminary discharge lasts for a period corresponding to a crank angle of 40° from timing T0, which is the later of the timing when the intake valve 21 opens and the timing when the exhaust valve 22 closes. It is preferable to carry out the procedure until the end of the period. Further, in this embodiment, the preliminary discharge period is 20° CA.

Next, the configurations of the ignition device 1 and the control device 5 for the internal combustion engine 2 will be explained.
The ignition device 1 of this embodiment includes an ignition coil 4, a spark plug 3, and a battery 12, as shown in FIG. Further, the ignition coil 4 includes an igniter 41, a coil portion 42, and a diode 43. Further, the control device 5 of the internal combustion engine 2 that controls the ignition device 1 includes an ignition control device 51 and a valve control section 52. The ignition control device 51 includes a main ignition control section 511 and a preliminary discharge control section 512.

In this embodiment, the igniter 41 includes a drive circuit section 411 and a switching element 412. The drive circuit section 411 controls turning on and off of the switching element 412. As the switching element 412, for example, IGBT (abbreviation for insulated gate bipolar transistor) or MOSFET (abbreviation for MOS field effect transistor) can be used.

Next, control of ignition of the main discharge in the spark plug 3 will be described.
Ignition of the main discharge in the ignition device 1 of this embodiment is controlled by the main ignition control section 511 of the ignition control device 51, as shown in FIG. Based on the ignition signal from the main ignition control section 511, a high voltage is applied to the spark plug 3 by the ignition coil 4 at a predetermined timing. The main ignition control unit 511 can control transmission of an ignition signal based on crank angle information detected by a crank angle sensor (not shown).

Specifically, based on the ignition signal from the main ignition control section 511, the igniter 41 of the ignition coil 4 is switched on and off to control the voltage of the battery 12 to the coil section 42, which consists of a primary coil 421 and a secondary coil 422. The voltage is increased at , and a high voltage is applied to the spark plug 3. This causes a main discharge to occur in the discharge gap G of the spark plug 3. Note that the diode 43 of the ignition coil 4 has a role of restricting the direction of the secondary current from the spark plug 3 to the direction toward the secondary coil 422. The anode side of the diode 43 is connected to the secondary coil 422, and the cathode side is grounded.

Further, the valve control unit 52 of the control device 5 changes the opening/closing timing of the intake valve 21 and the exhaust valve 22 according to the operating conditions of the internal combustion engine 2. In this embodiment, the operating conditions of the internal combustion engine 2 are the rotation speed and load of the internal combustion engine 2.

Next, control of preliminary discharge will be explained.
The preliminary discharge control section 512 of the ignition control device 51 controls the timing of preliminary discharge. The preliminary discharge control section 512 determines the timing for performing preliminary discharge based on the information on the opening/closing timing of the intake valve 21 and the exhaust valve 22 determined by the valve control section 52. That is, the timing for performing preliminary discharge is determined after the timing T0 determined by the valve control unit 52.

Then, an ignition signal is sent to the ignition coil 4 so that a preliminary discharge is generated at the preliminary discharge implementation timing determined by the preliminary discharge control unit 512. This causes preliminary discharge to occur in the discharge gap G of the spark plug 3 at a desired timing.

Further, the execution timing of the preliminary discharge with respect to the timing T0 and the preliminary discharge period are appropriately determined within the range of the initial stage of the intake stroke according to the operating conditions and the like.

Next, the effects of this embodiment will be explained.
The ignition device 1 for an internal combustion engine of this embodiment is configured to perform preliminary discharge at an early stage of the intake stroke. Therefore, it is possible to suppress the risk of early ignition of the air-fuel mixture due to preliminary discharge. Further, the ignition device 1 is configured to perform preliminary discharge after timing T0. Therefore, by efficiently generating excited gas molecules through the preliminary discharge, the required voltage for the main discharge can be lowered. As a result, ignitability can be improved.

Further, by lowering the required voltage for main discharge, it is possible to suppress heat generation in the ignition coil 4 and suppress the amount of electrode wear of the spark plug 3. As a result, the life of the ignition coil 4 and the spark plug 3 can be extended.

Further, the preliminary discharge is configured to be performed from timing T0 until a period corresponding to a crank angle of 40 degrees has elapsed. Therefore, as will be described later in evaluation test 4, preliminary discharge can be performed before the rich mixture R containing a large amount of fuel flows into the discharge gap G. As a result, it is possible to suppress the risk of early ignition of the air-fuel mixture due to preliminary discharge, and to efficiently generate excited gas molecules.

Further, the timing for performing preliminary discharge is determined based on information on the opening/closing timing of the intake valve 21 and the exhaust valve 22. Therefore, regardless of the operating conditions of the internal combustion engine 2, it is easy to reliably reduce the required voltage for main discharge.

Further, in the ignition device 1 of this embodiment, no special device or the like is required to perform preliminary discharge. Therefore, it is possible to reduce the required voltage for main discharge while avoiding an increase in the size and cost of the ignition device 1.

As described above, according to the present embodiment, it is possible to provide the ignition device 1 for an internal combustion engine that can improve ignition performance while preventing early ignition.

(Evaluation test 1)
The following evaluation test 1 was conducted using the ignition device 1 of Embodiment 1. In evaluation test 1, as shown in FIG. 6, the opening timing of the intake valve 21 and the closing timing of the exhaust valve 22 were set to be approximately the same, and the required voltage reduction effect of the main discharge was confirmed at each start timing of the preliminary discharge. The opening timing of the intake valve 21 is 1° CA after the top dead center (TDC) of the exhaust stroke, and the closing timing of the exhaust valve 22 is the TDC of the exhaust stroke. In addition, in FIG. 6, the preliminary discharge start timing is shown at a crank angle before the compression top dead center (that is, BTDC) with TDC of the compression stroke as a reference, and the same applies to FIG. 6 and subsequent figures. That is, the opening timing of the intake valve 21 is BTDC 359° CA, and the valve closing timing of the exhaust valve 22 is BTDC 360° CA. That is, timing T0 is BTDC359°CA.

The test conditions were an engine rotation speed of 1500 rpm and a preliminary discharge period of 20° CA. Further, the required voltage reduction effect at each timing was determined as an average value of n=500. Further, the required voltage reduction effect indicates by what percentage the required voltage can be reduced with respect to the required voltage of the main discharge in the case where the preliminary discharge is not performed.

From this test, it was confirmed that the effect of reducing the voltage required for main discharge was achieved by performing preliminary discharge after timing T0 at the early stage of the intake stroke. In particular, when preliminary discharge was started at BTDC 359° CA immediately after the intake valve 21 was opened and after the exhaust valve 22 was closed, the required voltage reduction effect was the highest. By performing preliminary discharge on the fresh air from the intake port 210, which is not a rich mixture R, excited N ₂ (nitrogen) molecules, which are the main active species that have the effect of reducing the required voltage, were efficiently generated. it is conceivable that. Further, even when the preliminary discharge start timing was BTDC 330° CA, a certain degree of effect was confirmed. On the other hand, even if preliminary discharge was performed at BTDC 390° CA before the initial stage of the intake stroke, that is, at the stage of the exhaust stroke, almost no required voltage reduction effect was observed. Further, even when preliminary discharge was performed from BTDC 320° CA or later, the required voltage reduction effect was almost absent or low. This is thought to be because active species could not be sufficiently generated even if preliminary discharge was performed on the mixture after combustion or the rich mixture R containing a large amount of fuel.

(Evaluation test 2)
Further, the following evaluation test 2 was conducted using the ignition device 1 of Embodiment 1. In evaluation test 2, as shown in FIG. 7, compared to evaluation test 1, the opening of the intake valve 21 was delayed by 20° CA. Specifically, the opening timing of the intake valve 21 is BTDC 339° CA, and the valve closing timing of the exhaust valve 22 is BTDC 360° CA. That is, timing T0 is BTDC339°CA. Other conditions were the same as those in Evaluation Test 1.

In this test as well, the effect of reducing the voltage required for main discharge was confirmed by performing preliminary discharge at the early stage of the intake stroke. In particular, when preliminary discharge was started at BTDC 339° CA immediately after the intake valve 21 was opened and the exhaust valve 22 was closed, the required voltage reduction effect was the highest. In addition, a certain degree of effect was confirmed until the preliminary discharge start timing was 320° CA BTDC. On the other hand, as in Evaluation Test 1, at the stage before the initial stage of the intake stroke, even if preliminary discharge was performed, there was almost no effect of reducing the required voltage. Further, even when preliminary discharge was performed from BTDC 300° CA or later, the required voltage reduction effect was almost absent or low. The same cause as in evaluation test 1 can be considered.

(Evaluation test 3)
Further, the following evaluation test 3 was conducted using the ignition device 1 of the first embodiment. In evaluation test 3, as shown in FIG. 8, compared to evaluation test 1, the opening of the intake valve 21 was advanced by 20° CA. Specifically, the opening timing of the intake valve 21 is BTDC 379° CA, and the valve closing timing of the exhaust valve 22 is BTDC 360° CA. That is, timing T0 is BTDC360°CA. Furthermore, in this test, as shown in FIG. 8, there is an overlap period in which both the intake valve 21 and the exhaust valve 22 are open. Other conditions were the same as those in Evaluation Test 1.

In this test as well, the effect of reducing the voltage required for main discharge was confirmed by performing preliminary discharge at the early stage of the intake stroke. In particular, when the intake valve 21 was open and the preliminary discharge was started at BTDC 360° CA immediately after the exhaust valve 22 was closed, the required voltage reduction effect was the highest. On the other hand, if the preliminary discharge is started from BTDC379°CA immediately after the intake valve 21 is opened, that is, if the preliminary discharge is started from the overlap period when both the intake valve 21 and the exhaust valve 22 are open, , the result was that there was almost no effect of reducing the required voltage. The results obtained when preliminary discharge is performed during the overlap period are that although preliminary discharge is performed on fresh air that is not a rich mixture R from the intake port 210, the generated active species are generated before the main discharge occurs. This is thought to be due to the exhaust being exhausted to the outside through the exhaust port 220. On the other hand, when preliminary discharge was performed before the initial stage of the intake stroke or after BTDC 320° CA, the required voltage reduction effect was almost absent or low. The same cause as in evaluation test 1 can be considered.

(Evaluation test 4)
In the ignition device 1 of Embodiment 1, the following evaluation test 4 was conducted. In evaluation test 4, the opening/closing timing of both valves 21 and 22 and the engine speed were the same as in evaluation test 1. Then, as shown in FIGS. 9 to 11, the flow of the rich mixture R from the intake port 210 was simulated from BTDC 360° CA to BTDC 320° CA immediately before the beginning of the intake stroke. 9 to 11 show the situations of the internal combustion engine 2 corresponding to BTDC 360° CA, BTDC 330° CA, and BTDC 320° CA in FIG. 6 of Evaluation Test 1, respectively.

Immediately after the exhaust valve 22 closes and before the intake valve 21 opens, at BTDC 360° CA, the rich mixture R exists in the intake port 210, as shown in FIG. Then, with the exhaust valve 22 closed, the rich mixture R flows into the main combustion chamber 23 at 330° CA BTDC after the intake valve 21 is opened, as shown in FIG. . As shown in FIG. 11, the rich mixture R reached the discharge gap G of the spark plug 3 at BTDC 320° CA. In other words, the rich mixture R flows into the discharge gap G after 40° CA from the timing T0.

(Embodiment 2)
The ignition device 1 of this embodiment is configured to determine the timing of performing preliminary discharge based on the prediction of the short-circuit frequency of preliminary discharge.

The ignition device 1 of the present embodiment is configured to determine the timing of performing preliminary discharge based on a map obtained in advance of the relationship between the timing of performing preliminary discharge, the operating conditions of internal combustion engine 2, and the short-circuit frequency of preliminary discharge. has been done.

The ignition device 1 of this embodiment is configured to perform preliminary discharge during a period when the frequency of short circuits is predicted to be low based on the above map. By performing preliminary discharge when the frequency of short circuits is low, glow discharge can be stably continued, and active species can thereby be efficiently generated. On the other hand, if preliminary discharge is performed when there is a high frequency of short circuits, arc discharge is likely to occur, electrical energy becomes heat, and it is difficult to efficiently generate active species.

In this embodiment, the map is created by conducting an experiment or the like in advance. Then, data for the map is acquired by detecting a short circuit in the preliminary discharge while changing the operating conditions of the internal combustion engine 2. The preliminary discharge control unit 512 that determines the timing of performing preliminary discharge includes the map. The operating conditions of the internal combustion engine 2 include, for example, the rotation speed and load of the internal combustion engine 2.

A short circuit in the preliminary discharge is detected by measuring the secondary current of the ignition coil 4, as shown in FIG. To determine the short-circuit frequency, a reference value for the secondary current is determined in advance, and the number of times the secondary current falls below the reference value within a predetermined period is measured, as shown by the circle in Figure 12, and the number of times is determined as the short-circuit frequency. calculate. Note that in detecting the short-circuit frequency of preliminary discharge, the measured value of the secondary current may be subjected to high-pass filter (HPF) processing. Furthermore, the short circuit frequency may be detected using the primary voltage instead of the secondary current.

The preliminary discharge control unit 512 stores the short circuit frequency of preliminary discharge as the above-mentioned map for each operating condition of the internal combustion engine 2. That is, the pre-discharge control unit 512 stores, as a map, a period with a low frequency of short circuits during which effective pre-discharge can be carried out for each operating condition. Then, the preliminary discharge control unit 512 receives data on the operating conditions of the internal combustion engine 2, compares it with the map, and controls the preliminary discharge to be performed during a period when the short circuit frequency of the preliminary discharge is predicted to be low. do.
The rest is the same as in the first embodiment.
Note that among the symbols used in the second embodiment and subsequent embodiments, the same symbols as those used in the previously described embodiments represent the same components as those in the previously described embodiments, unless otherwise specified.

The ignition device 1 of the present embodiment is configured to determine the timing of performing preliminary discharge based on a map obtained in advance of the relationship between the timing of performing preliminary discharge, the operating conditions of internal combustion engine 2, and the short-circuit frequency of preliminary discharge. has been done. In other words, the preliminary discharge is configured to be performed during a period when the frequency of short circuits is expected to be low. Therefore, as will be explained in Evaluation Test 5 below, the effect of reducing the voltage required for main discharge can be further improved.
Other than that, it has the same effects as Embodiment 1.

(Evaluation test 5)
The following evaluation test 5 was conducted using the ignition device 1 of Embodiment 2. In evaluation test 5, as shown in FIG. 13, under the same operating conditions as evaluation test 1, the short-circuit frequency of preliminary discharge at the beginning of the intake stroke and the required voltage reduction effect at each preliminary discharge start timing were measured. The short circuit frequency was determined by measuring the number of short circuits in a period of 1° CA. Moreover, the short circuit frequency at each timing was determined as an average value of n=50. Other conditions were the same as those in Evaluation Test 1.

As shown in FIG. 13, when preliminary discharge was started at a timing of 359° CA BTDC, where the frequency of short circuits is relatively low, the required voltage reduction effect was the highest. On the other hand, when preliminary discharge was started at the timing of BTDC 330° CA or BTDC 300° CA, where the short circuit frequency is maximum, the required voltage reduction effect was lower than when it was started at the BTDC 359° CA timing. It is considered that by performing preliminary discharge when the frequency of short circuits is relatively low, glow discharge can be continued stably, and that active species can be generated efficiently.

(Embodiment 3)
As shown in FIG. 14, the ignition device 1 of this embodiment includes a preliminary discharge necessity determining section 53 that determines whether preliminary discharge is necessary.

In this embodiment, the control device 5 of the internal combustion engine 2 includes a preliminary discharge necessity determining section 53, as shown in FIG. As shown in FIG. 15, the preliminary discharge necessity determination unit 53 determines the necessity of preliminary discharge for each operating condition based on a preset reference value of the required voltage for main discharge. When the preliminary discharge necessity determination section 53 determines that preliminary discharge is not necessary, it instructs the preliminary discharge control section 512 not to perform preliminary discharge.

Factors that increase the required voltage for main discharge include, for example, [1] intake pressure, [2] target EGR (exhaust gas recirculation) amount, [3] target main ignition timing, and [4] cylinder There are operating parameters such as internal temperature and [5] actual compression ratio. [1] The larger the intake pressure and [2] the target EGR amount, and the closer [3] the target main ignition timing is to TDC, the higher the required voltage for main discharge becomes. Furthermore, [4] the lower the in-cylinder temperature, and [5] the higher the actual compression ratio, the higher the required voltage for main discharge.

For example, if the contribution of parameters [1] to [5] to the required voltage increase is expressed as A to E, respectively, the estimated required voltage value can be determined from the sum of these parameters, as shown in FIG. Then, if the required voltage estimated value determined from the total contribution of the parameters exceeds the reference value, preliminary discharge is performed.

That is, conditions 1 to 3 in FIG. 15 indicate three different operating conditions. Then, under each operating condition, if the estimated required voltage for main discharge is lower than the reference value (in the case of conditions 1 and 2 in FIG. , instructs not to perform preliminary discharge. On the other hand, if the estimated required voltage for main discharge is greater than or equal to the reference value (condition 3 in FIG. 15), a command is issued to perform preliminary discharge.

Next, the control of the preliminary discharge control section 512 will be explained according to the flowchart of FIG. 16. First, in step S1, the preliminary discharge control section 512 determines whether or not the operating conditions require preliminary discharge, based on a command from the preliminary discharge necessity determination section 53. If the operating conditions do not require preliminary discharge, the process returns to step S1 and it is again determined whether preliminary discharge is necessary. On the other hand, if it is determined that the operating conditions require preliminary discharge, the process proceeds to step S2.

In step S2, the preliminary discharge control unit 512 determines whether or not the valve overlap state is in which both the intake valve 21 and the exhaust valve 22 are open, based on the signal from the valve control unit 52. If the valves are in the valve overlap state, the process proceeds to step S3, where the timing at which the exhaust valve 22 closes is read based on the signal from the valve control section 52, and the process proceeds to step S5. On the other hand, if it is determined in step S2 that the valves are not overlapped, the process proceeds to step S4, where the timing at which the intake valve 21 opens is read based on the signal from the valve control section 52, and the process proceeds to step S5.

In step S5, the preliminary discharge control section 512 determines the preliminary discharge timing, and in step S6, outputs a preliminary discharge output signal to the ignition coil 4.
The rest is the same as in the first embodiment.

The ignition device 1 of this embodiment includes a preliminary discharge necessity determining section 53. Therefore, if it is determined that preliminary discharge is unnecessary, control can be performed so that preliminary discharge is not performed. Therefore, it is possible to suppress the heat generation of the ignition coil 4 and the amount of electrode wear of the spark plug 3. As a result, the life of the ignition coil 4 and the spark plug 3 can be extended.
Other than that, it has the same effects as Embodiment 1.

In the first to third embodiments described above, the internal combustion engine 2 is of the intake port injection type. However , the internal combustion engine may include both a fuel injection valve for intake port injection and a fuel injection valve for direct injection .

Further, in the first to third embodiments described above, an example was shown in which the preliminary discharge period was 20° CA. However, the preliminary discharge period can be changed depending on the operating conditions of the internal combustion engine 2 and the like. The pre-discharge period can be, for example, less than 20° CA. Further, the preliminary discharge period can be made longer than 20° CA.

The present invention is not limited to the above-mentioned embodiments, but can be applied to various embodiments without departing from the gist thereof.

1 Ignition device 2 Internal combustion engine 21 Intake valve 22 Exhaust valve 3 Spark plug 31 Insulator 321 Tip protrusion 32 Center electrode 33 Housing 331 Ground electrode G Discharge gap T0 The later of the intake valve opening timing and the exhaust valve closing timing your timing

Claims (2)

A cylindrical insulator (31), a center electrode (32) held inside the insulator and having a tip protrusion (321) protruding from the tip side of the insulator, A spark plug (3) having a cylindrical housing (33) held on the side, and a ground electrode (331) connected to the housing and forming a discharge gap (G) between the tip protrusion and the spark plug (33). ),
The initial stage of the intake stroke of the internal combustion engine (2) equipped with the spark plug, the timing at which the intake valve (21) of the internal combustion engine opens and the timing at which the exhaust valve (22) of the internal combustion engine closes. , the preliminary discharge is performed after the later timing (T0),
The preliminary discharge is configured to be performed between the timing when the intake valve opens and the timing when the exhaust valve closes, whichever is later, until a period corresponding to a crank angle of 40 degrees has elapsed. Ori,
After performing the preliminary discharge, the main discharge is performed to ignite the air-fuel mixture,
The internal combustion engine has an intake port (210) equipped with the intake valve, and the internal combustion engine is a port injection type internal combustion engine in which fuel is injected into the intake port. 1). The system is configured to determine the implementation timing of the preliminary discharge based on a map obtained in advance of the relationship between the execution timing of the preliminary discharge, the operating conditions of the internal combustion engine, and the short-circuit frequency of the preliminary discharge. Item 1. An ignition device for an internal combustion engine according to item 1 .

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