JP2000345951A - Ignition device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve ignitability to a mixture and to prevent a misfire caused by the fouling of a plug by switching-driving a switching element continuously a plurality of times to generate spark discharge to a spark plug continuously a plurality of times at the combustion timing of one combusiton cycle of an internal combustion engine. SOLUTION: At the time of operating an engine, a control signal generated by an ECU so as to generate spark discharge to a spark plug 13 continuously a plurality of times is impressed to a transistor 17 which is a switching element, to switch-drive it. With the 'on' operation of the transistor 17, a primary current flows to a primary coil of an ignition coil, and the primary current is cut off by the succeeding 'off' operation. High voltage is thereby generated to a secondary coil of the ignition coil to generate spark discharge at the spark plug 13. Such operations are repeated a plurality of times, and multiple discharge is generated by recarrying the primary current before the natural termination of spark discharge. A mixture is thereby ignited positively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for an internal combustion engine in which a high voltage for ignition is applied to a spark plug to cause spark discharge of the spark plug.

[0002]

2. Description of the Related Art In an internal combustion engine, a fuel injection valve (injector) is configured to directly inject fuel into a cylinder.
A rich mixture is formed in the vicinity of a plug gap formed by a center electrode and a ground electrode of a spark plug (hereinafter, also simply referred to as a "plug") attached to the internal combustion engine, and a lean mixture is formed in a layered manner around the mixture. 2. Description of the Related Art There is known a direct injection type internal combustion engine which performs a so-called stratified combustion in which an air-fuel mixture is burned. The direct-injection type internal combustion engine has advantages such as good fuel economy and little harmful substances in exhaust gas, because the mixture can be ignited even when the overall average air-fuel ratio is extremely small.

[0003] However, in the direct injection type internal combustion engine, since a rich mixture is induced near the plug gap, plug contamination such as smoldering tends to occur, whereby the insulation resistance between the center electrode and the ground electrode tends to decrease. There are drawbacks. The reason why the insulation resistance is likely to decrease is that in a direct injection type internal combustion engine, as described above, a rich mixture is induced near the plug gap, but as the mixture becomes richer, the fuel (liquid fuel) is sufficiently vaporized. The fuel droplets tend to be difficult to atomize, and the fuel droplets tend to adhere to the insulator surface near the plug gap, and the adhered droplets easily become carbon without complete combustion and adhere to the insulator surface. Can be In addition, in a direct injection type internal combustion engine, the intake air flow (swirl flow or tumble flow) which is indispensable for forming a stratified mixture during operation at low rotation and low load such as idling is weak. Furthermore, fuel vaporization and atomization become insufficient.

[0004] When the deposition of carbon is repeated, the deposited carbon moves and aligns to form a bridge due to the electric field generated during the spark discharge, and a leak current is generated on the surface of the insulator. Depending on the structure of the plug, this leakage current may cause spark discharge between the grounded electrode and the place where insulation has been reduced due to the carbon attached to the insulator surface, which may cause so-called deep jump. In the direct injection type internal combustion engine, since a rich mixture is induced near the plug gap, there is a high possibility of misfiring because only a lean mixture exists at the place where the back jump occurs. In addition, when the generation of the leak current is remarkable, the voltage (high voltage for ignition) required for the plug is abnormally reduced, causing a misfire.

[0005]

Therefore, as an ignition device resistant to such plug fouling, the electric charge accumulated in the capacitor is discharged to the primary winding of the ignition coil at once, and the high voltage for ignition is applied to the secondary winding. Is known. In the capacitive discharge ignition device, since the voltage applied to the primary winding of the ignition coil is usually as high as several hundred volts, the winding ratio of the primary winding to the secondary winding is small, and the coil winding ratio depends on the number of windings of the coil. Since the inductance can be set small, the output impedance decreases and the ignition high voltage (secondary voltage) rises quickly. As a result, before the carbon moves and aligns to form a bridge due to the electric field applied at the time of the spark discharge, that is, before the conductive path through which the leak current flows is formed,
Since the ignition high voltage applied to the plug rises, it is possible to suppress the generation of a leak current. In addition, the time during which the electric field is generated during spark discharge is short, the voltage drop of the high voltage for ignition due to the effect of insulation deterioration due to plug fouling is reduced, and the possibility of misfiring due to plug fouling is low.

However, in the capacitive discharge type ignition device, since the inductance of the coil is set small as described above, the spark duration during spark discharge is several tens μsec.
0 μSec., Short-time operation at low load and low rotation such as idling, the spark energy required to ignite the air-fuel mixture is insufficient, and the flame nucleus formed by spark discharge tends to be small. There is a problem that there is a high possibility of doing this.

On the other hand, a magnetic flux is induced by energizing the primary winding of the ignition coil, and a sharp change of the magnetic flux is caused by interrupting the energizing current to generate a high ignition voltage in the secondary winding. Induction discharge ignition devices are also known. This is an ignition device characterized by having excellent ignitability due to a long duration of one spark, and is a method most frequently used as an ignition device for an internal combustion engine. However, the induction discharge igniter is more
The inductance of the coil used is set large, and the rise of the ignition high voltage (secondary voltage) is slow. Therefore, under conditions where the electric field generated during spark discharge is relatively long and the plug is liable to be contaminated such as in a direct injection type internal combustion engine, the electric field generated during spark discharge before the high voltage for ignition applied to the plug rises. Therefore, there is a drawback that carbon easily moves and aligns to form a bridge, and misfiring easily occurs due to plug fouling.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in an ignition device for an internal combustion engine, achieves good ignitability when igniting an air-fuel mixture, and also provides ignition for an internal combustion engine that is resistant to plug fouling. It is intended to provide a device.

[0009]

According to a first aspect of the present invention, there is provided an ignition coil in which one end of a secondary winding is connected to a spark plug, and a primary winding of the ignition coil. A switching element for energizing and interrupting a primary current flowing through the ignition plug, and a high voltage for ignition is generated in a secondary winding of the ignition coil by energizing and interrupting the primary current, thereby spark discharge of the ignition plug. An ignition control means for performing switching driving of the switching element, wherein the ignition control means controls the switching element at a combustion timing of one combustion cycle of the internal combustion engine. By performing switching driving continuously plural times, the spark plug discharges sparks continuously plural times.

That is, in the ignition device for an internal combustion engine according to the present invention (claim 1), first, the ignition control means turns on the switching element to cause a primary current to flow through the primary winding of the ignition coil, and the ignition timing Then, the switching element is turned off to interrupt the primary current, and the ignition high voltage generated in the secondary winding is applied to the ignition plug to generate a spark discharge. After a lapse of a predetermined time, the ignition control means forcibly interrupts the spark discharge by turning on the switching element again and re-energizing the primary current, and further turns off the switching element after the lapse of the predetermined time. In this state, the primary current is cut off again and spark discharge is caused again. As described above, the ignition control means continuously generates the spark discharge a plurality of times by performing the switching drive of the switching element continuously a plurality of times.

At this time, the ignition control means forcibly terminates the spark discharge by turning on the switching element and re-energizing the primary current before the spark discharge ends spontaneously. The magnetic flux induced by the immediately preceding spark discharge remains to some extent in the ignition coil during energization. Therefore, the time for supplying the primary current to induce magnetic flux before the second and subsequent spark discharges is shorter than the time for supplying the primary current supplied for the first spark discharge. Therefore, by forcibly interrupting the spark discharge, it is possible to realize a multiple discharge in which the spark plug is continuously discharged a plurality of times at the combustion timing of one combustion cycle of the internal combustion engine.

At this time, the spark coil has a spark duration of 1 to 3 when one spark discharge is naturally terminated.
mSec. is used, and for one spark discharge, the duration of spark from generation of spark discharge to interruption is set so that flame nuclei are sufficiently generated, that is, ignition of the air-fuel mixture is ensured. , Specifically,
1mSec. Or more is recommended. In order to generate a spark discharge by applying a sufficiently high ignition high voltage to the ignition plug, the ignition high voltage is preferably set to 50 kV or more.

[0013] In this way, the ignition of the air-fuel mixture is performed by the first spark discharge even during the operation at low load and low rotation such as idling. Even if the ignition of the air-fuel mixture is not performed normally, it becomes possible to ignite the air-fuel mixture by the second and subsequent spark discharges. In other words, in the present invention, since the duration of one spark is made relatively long and multiple discharges are performed,
Even when carbon is attached to the insulator surface of the plug, the carbon can be burned off during one fuel cycle, thereby preventing plug fouling and igniting the air-fuel mixture.

Therefore, according to the ignition device for an internal combustion engine of claim 1 of the present invention, good ignitability to the air-fuel mixture can be realized, and carbon attached to the plug is burned off. Plug contamination can be prevented. In addition, the present invention is applied to a capacitive discharge type ignition device,
Burn off carbon attached to the plug by multiple discharges,
However, in order to satisfactorily ignite the air-fuel mixture, it is necessary to generate 20 or more spark discharges at a cycle of 100 μSec. Or less during the combustion timing of one combustion cycle of the internal combustion engine. In order to realize this, a large-capacity power supply for discharging capacity, a high-speed and large-capacity switching element (for example, IGB)
Since expensive equipment such as T) is required, it is difficult to realize the cost. On the other hand, when the present invention is applied to the induction discharge type ignition device, since the duration of one spark is long, a conventionally used device can be used. By applying it, it is possible to realize it at low cost.

The ignitability of an internal combustion engine varies depending on the operating conditions. Particularly, in an operation at a low temperature or an operation at a low load and a low speed such as idling, the ignitability of the air-fuel mixture is inferior. Therefore, the ignition control means may control the primary current such that the ignition high voltage becomes higher as the operating condition with the poorer ignitability becomes, as in the ignition device for an internal combustion engine according to the second aspect. .

That is, in order to more reliably ignite the air-fuel mixture under the above-described operating conditions with poor ignitability, the ignition control means controls the primary current to be large, thereby increasing the ignition current. What is necessary is just to perform a spark discharge at a higher voltage. Therefore, according to the ignition device for an internal combustion engine of the present invention (claim 2), even under an operating condition having poor ignitability, the high voltage for ignition is increased to generate spark discharge, so that the mixture to the air-fuel mixture is reduced. It can improve the ignitability,
Misfires can be reduced.

Further, the ignition control means may switch the ignition control means so that the number of continuous spark discharges increases as the operating condition with poor ignition performance as described above increases, as in the ignition device for an internal combustion engine according to claim 3. The number of switching operations of the element may be controlled. That is, as a method of improving the ignitability of the air-fuel mixture, there is a method of increasing the spark duration, in addition to the method of increasing the high voltage for ignition as in claim 2, and increasing the number of times of spark discharge. Thus, the same effect as increasing the spark duration can be obtained. In particular, in a low-speed operation state, the time required for one combustion cycle becomes longer, and therefore, it is effective means to increase the number of continuous spark discharges to more reliably ignite the air-fuel mixture. . On the other hand, in the high rotation operation state, the ignitability is good, so the number of continuous spark discharges may be small, and in some cases, the number of spark discharges may be one.
It may be times.

Further, as in the ignition device for an internal combustion engine according to the fourth aspect, the switching drive interval of the switching element is set so that the interval of the spark discharge becomes shorter as the ignitability becomes lower as described above. You may make it change. That is, the time during which spark discharge is not performed between spark discharges that are continuously performed a plurality of times is shortened.

That is, for example, if the interval between the spark discharges is shortened without changing the number of continuous spark discharges, the spark duration per time can be extended, that is, the spark duration as a whole can be extended. It is possible to do. In addition, for example, if the spark duration per cycle is not changed and the interval between spark discharges is shortened, the number of continuous spark discharges per combustion cycle can be increased, that is, the spark duration can be increased. It becomes possible.

Therefore, according to the ignition device for an internal combustion engine according to the third and fourth aspects of the present invention, it is possible to extend the spark duration, and as described above, by increasing the spark duration, It becomes possible to make sure the ignition of the ki. Next, the ignition device for an internal combustion engine according to the first to fourth aspects of the present invention may be provided with an ignition plug having a spark cleaning action as the ignition plug as in the fifth aspect of the invention. .

Here, the spark plug having a spark cleaning effect is a plug that is designed such that, when carbon adheres to the surface of the insulator, the spark flies along the surface of the insulator to burn off the carbon and discharge the spark. A spark plug with a designed gap. As an example of the structure of the spark plug having the spark cleaning action, a spark discharge is always carried out along the tip end face of the insulator so as to face the tip side face of the center electrode protruding from the tip end face of the insulator. A so-called semi-creeping spark plug in which a plurality or annular ground electrodes are provided as described above. In addition, when carbon adheres to the surface of the insulator so as to face the side surface of the front end of the center electrode protruding from the end surface of the front end of the insulator, a spark discharge is generated along the side surface of the front end of the insulator to prevent insulation. If the body surface is clean, a plurality of ground electrodes were provided so as to cause a spark discharge in the air gap between the tip end surface of the center electrode and
A so-called intermittent discharge type spark plug is used. Further, there is a plug other than the plug gap formed by the center electrode and the ground electrode, in which spark discharge is generated when carbon adheres to the insulator surface to form a spark auxiliary gap for burning off carbon.

Therefore, if an ignition plug having a spark cleaning action is provided as an ignition plug of an ignition device for an internal combustion engine that performs multiple discharges as in the above invention, carbon can be discharged by spark discharge even if plug fouling occurs. The burning action
It can be demonstrated even more.

On the other hand, in the ignition device for an internal combustion engine according to the above-mentioned invention, if the last spark discharge of a plurality of continuous spark discharges is maintained in a cut-off state, the primary current continues to flow after the spark discharge is cut off. Therefore, the amount of heat generated by the switching element increases, which may adversely affect the durability of the switching element. If the primary current is cut off in order to avoid the heat generation of the switching element, there is a possibility that unnecessary spark discharge may be generated, and wasteful energy is consumed. Also, when the spark discharge is naturally terminated without forcibly shutting off the last spark discharge, useless energy is consumed.

To solve such a problem, as in the ignition device for an internal combustion engine according to the sixth aspect, the ignition control means performs the last spark discharge among the spark discharges performed continuously plural times. After the start, the spark discharge interrupting means for forcibly terminating the spark discharge by re-energizing the primary winding and the spark discharge interrupting means restart the energization to the primary winding of the ignition coil, And a current adjusting means for gently reducing the energizing current.

That is, of the spark discharges performed a plurality of times,
In order to forcibly interrupt the last spark discharge, when the spark discharge interrupting means restarts energization to the primary winding of the ignition coil,
By gently reducing the energizing current at the time of the re-energization, it is possible to prevent a high voltage from being generated in the secondary winding of the ignition coil when the energization is stopped.

With this configuration, it is possible to reduce the amount of current flowing through the switching element used for re-energizing the primary winding of the ignition coil, thereby suppressing the amount of heat generated. The durability can be improved.

As is clear from the above description,
The ignition device for an internal combustion engine according to claims 1 to 6 of the present invention is configured to directly inject fuel into an internal combustion engine in which plug fouling is likely to occur, that is, as in claim 7. By applying to a direct injection type internal combustion engine, more effects can be exhibited.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is an electric circuit diagram illustrating a configuration of an ignition device for an internal combustion engine according to a first embodiment. In the first embodiment, a single-cylinder internal combustion engine will be described.
The present invention can be applied to an internal combustion engine having a plurality of cylinders, and the basic configuration of the ignition device for each cylinder is the same.

As shown in FIG. 1, an ignition device 1 for an internal combustion engine according to a first embodiment includes an electric energy for discharge (for example, a voltage 1).
2V), a spark plug 13 provided in a cylinder of the internal combustion engine, and a primary winding L1.
An ignition coil 15 composed of a secondary winding L2, an npn transistor 17 connected in series with the primary winding L1,
An electronic control unit (hereinafter referred to as an ECU) that outputs a first command signal Sa for switchingly driving the transistor 17 so as to cause the spark plug 13 to generate spark discharge continuously multiple times.
19).

Of these, the transistor 17 is a switching element composed of a semiconductor element for switching between energization and non-energization of the primary winding L1 of the ignition coil 15. The ignition device 1 for an internal combustion engine according to the first embodiment is an induction motor. It is a distributor-less full-transistor type ignition device as an example of a discharge type ignition device. The ECU 19 corresponds to an ignition control unit described in the claims.

Here, one end of the primary winding L1 is connected to the positive electrode of the power supply device 11, and the other end is connected to the collector of the transistor 17. One end of the secondary winding L2 is connected to the primary winding L1 connected to the positive electrode of the power supply device 11.
, And the other end is connected to a center electrode 13 a of the ignition plug 13. The ground electrode 13b of the ignition plug 13 is grounded to the same potential as the negative electrode of the power supply device 11, and the base of the transistor 17 is connected to the ECU 19
, And the emitter of the transistor 17 is grounded.

Therefore, when the first command signal Sa output from the ECU 19 goes high (generally the power supply voltage Vc), the transistor 17 is turned on, and the primary winding of the ignition coil 15 is turned on from the positive electrode side of the power supply device 11. An energization path of the primary winding L1 is formed through the line L1 to the negative electrode side of the power supply device 11, and a current (primary current) i1 flows through the primary winding L1.
Flow.

When the first command signal Sa goes low (generally at ground potential) while the primary current i1 is flowing through the primary winding L1, the transistor 17 is turned off, and the primary winding L1 is turned off. Of the primary current i1 is stopped. Then, a high voltage for ignition is generated in the secondary winding L2 of the ignition coil 15 and is applied to the ignition plug 13, so that a spark discharge is generated between the electrodes 13a and 13b of the ignition plug 13.

The ignition coil 15 is connected to the center electrode 13a of the ignition plug 13 on the side of the center electrode 13a by turning on and off the primary winding L1. A high voltage is generated, and a current (secondary current) i2 flowing through the secondary winding L2 due to the spark discharge passes through the secondary winding L2 from the center electrode 13a of the ignition plug 13 to the primary winding. It flows to the winding L1 side. Also, the secondary winding L2 and the primary winding L
A rectifying element D composed of a diode or the like is provided at a connection portion with the first element 1 to allow a current to flow from the secondary winding L2 to the primary winding L1 and to prevent a current from flowing in the reverse direction. The operation of the rectifying element D prevents the current from flowing to the secondary winding L2 when the transistor 17 is turned on (at the start of energization to the primary winding L1).

Subsequently, in a state where the spark discharge continues,
When the first command signal Sa goes high, the transistor 17 is turned on and the primary current i1 to the primary winding L1 is turned on.
Is re-energized, so that the ignition high voltage generated in the secondary winding L2 is not induced, and the ignition plug 13
Is forcibly shut off. Then, when the first command signal Sa goes to a low level, spark discharge occurs again in the ignition plug 13.

In this embodiment, the spark discharge is forcibly terminated by turning on the transistor 17 and re-energizing the primary current before the spark discharge ends spontaneously. In the primary winding L1 of the coil 15, a certain amount of magnetic flux induced by the immediately preceding spark discharge remains. Therefore, the time for supplying the primary current to induce magnetic flux before the second and subsequent spark discharges is shorter than the time for supplying the primary current before the first spark discharge. Therefore, by forcibly interrupting the spark discharge, multiple discharges in which the spark plug 13 is continuously discharged a plurality of times during one combustion cycle of the internal combustion engine can be realized.

As described above, the ECU 19 switches the transistor 17 repeatedly to be turned on and off by repeatedly changing the level of the first command signal Sa, whereby the primary current i1 of the ignition coil 15 is reduced. The energization / interruption is repeated, and spark discharge can be continuously performed a plurality of times.

FIG. 2 shows the first command signal Sa, the primary current i1 flowing through the primary winding L1 and the center electrode 13a of the ignition plug 13 in the internal combustion engine ignition device of the first embodiment shown in FIG. 5 is a time chart illustrating each state of a potential Vp. FIG. 2 shows an example in which the spark discharge is performed three times continuously at the combustion timing of one combustion cycle of the internal combustion engine.

Such a spark discharge is executed by an ignition control process executed by the ECU 19. The ignition control process will be described with reference to a flowchart shown in FIG. The ECU 19 is for comprehensively controlling the spark discharge timing, the fuel injection amount, the idling speed, and the like of the internal combustion engine. For the purpose of ignition control described below, the intake air of the internal combustion engine is separately provided. An operating state detection process is performed to detect the operating state of each part of the engine, such as the amount (intake pipe pressure), rotation speed, throttle opening, cooling water temperature, intake air temperature, and the like.

In the ignition control process shown in FIG. 3, for example, one combustion in which the internal combustion engine performs intake, compression, combustion, and exhaust is performed based on a signal from a crank angle sensor that detects the rotation angle (crank angle) of the internal combustion engine. It is executed once per cycle. When the ignition control process is started, first, S
At 110 (S represents a step), the operating state of the engine detected by the operating state detection process executed separately is read, and at S120, based on the read operating state,
Calculate spark discharge conditions. The spark discharge conditions calculated here include the initial spark discharge occurrence timing ts, the maximum primary current value Im, the number N of continuous spark discharges, the spark duration Tt of each spark discharge, and the spark discharge interval Tb. Is calculated according to the operating state.

The initial spark discharge occurrence time ts is determined by, for example, obtaining a control reference value using a map or a calculation formula using the intake air amount and the rotation speed of the internal combustion engine as parameters, and using the control reference value as a cooling water temperature, an intake air temperature and the like. It is calculated in such a procedure as to make correction based on this. In addition, the maximum primary current value Im is determined based on, for example, the rotational speed of the internal combustion engine and the throttle opening indicating the engine load, under operating conditions in which the spark energy required to burn the air-fuel mixture is large (low load and low load of the internal combustion engine). It is calculated using a preset map or a formula so that it is large when the engine is rotating, etc., and is small under operating conditions where the spark energy may be small (eg, when the internal combustion engine is rotating at high load and high speed). Here, since the magnitude of the collector current of the transistor 17 is proportional to the base current, it is possible for the ECU 19 to change the maximum primary current value Im by controlling the current value of the first command signal Sa. .

The number N of continuous spark discharges, the spark duration Tt of each spark discharge, and the spark discharge interval Tb are based on, for example, the air-fuel mixture burning based on the rotational speed of the internal combustion engine and the throttle opening indicating the engine load. Under operating conditions where the required spark energy is large (such as when the internal combustion engine is at a low load and low speed), the number N of continuous spark discharges is large, the spark duration Tt of each spark discharge is long, and the spark discharge interval Tb is short. like,
Further, under operating conditions where the spark energy may be small (such as when the internal combustion engine is rotating at a high load and high speed), the number N of continuous spark discharges is small, the spark duration Tt of each spark discharge is short, and the spark discharge interval Tb is long. Is calculated using a preset map or calculation formula.

In this embodiment, since the last spark discharge is naturally terminated, the spark duration Tt is calculated for each spark discharge except the last spark discharge, and the spark duration of each spark discharge is calculated. Tt calculates the same value in all cases. However, a different spark duration Tt may be calculated for each spark discharge according to the operating state of the internal combustion engine.

Next, in S130, a counter i for counting the number of continuous spark discharges is set to 1 in order to initialize the counter i, and in S140, the first spark discharge occurrence time ts (ts) calculated in S120 is calculated. Time t shown in FIG.
With respect to 2), the energization start timing of the primary winding L1 earlier by the preset energization time of the primary winding L1 is determined, and when the energization start timing is reached (time t1 shown in FIG. 2), the first The command signal Sa is changed from low to high.

When the first command signal Sa is switched from low to high in the process of S140, the transistor 17 is turned on, so that the primary current i1 flows through the primary winding L1 of the ignition coil 15. The energization time of the primary winding L1 until the first spark discharge occurrence time ts is determined by energizing the primary winding L1 to ignite the maximum spark energy required to burn the mixture under all operating conditions of the internal combustion engine. This is the time required to accumulate in the coil 15 and is set in advance.

At S150, based on the detection signal from the crank angle sensor, at the time of the first spark discharge (when the counter i = 1), is the first spark discharge occurrence time ts calculated at S120 reached? It is judged whether or not, and when a negative judgment is made, the same steps are repeatedly executed,
It waits until the first spark discharge occurrence time ts is reached. S15
At 0, when it is determined that the first spark discharge occurrence time ts has been reached (time t2 shown in FIG. 2), the process proceeds to S160.

In step S150, the timing of the second or subsequent spark discharge (when the counter i ≧ 2) is also determined. However, in the second or subsequent spark discharge, the calculation is performed in step S120 after the previous spark discharge is interrupted. The time at which the generated spark discharge interval Tb has elapsed is defined as the spark discharge occurrence time, and it is determined whether or not the spark discharge occurrence time has been reached. If a negative determination is made, the same step is repeatedly executed to thereby perform the spark discharge. Wait until the time of occurrence. If it is determined in S150 that the spark discharge occurrence time has been reached, the process proceeds to S160.

Next, in S160, the first command signal Sa is inverted from high to low level. As a result, the transistor 17 is turned off, the primary current i1 is cut off, a high voltage for ignition is generated in the secondary winding L2 of the ignition coil 15, and a spark discharge is generated in the ignition plug 13.

Then, in S170, the spark discharge is
Whether or not the number of continuous spark discharges N calculated in S120 has been performed is determined based on whether or not the counter i has reached the number of continuous spark discharges N. If an affirmative determination is made, the ignition control process is terminated, If a negative determination is made, the process proceeds to S180, where the counter i is incremented (i =
i + 1). For example, if the value of the counter i before shifting to S180 is 1 (i = 1), the counter i is set to 2 (i = 2) in S180.

In subsequent S190, after it is determined in S150 that the spark discharge has occurred, it is determined whether the spark duration Tt obtained in S120 has elapsed. If a negative determination is made, the same steps are repeated. By executing, it waits for the spark duration time Tt to elapse. Then, in S190,
If it is determined that the spark duration time Tt has elapsed (time t3 shown in FIG. 2), the flow shifts to S200, where the first command signal Sa is sent.
From low to high, which turns on transistor 17 and re-energizes primary current i1,
The high voltage for ignition is not induced in the secondary winding L2 of the ignition coil 15, and the spark discharge of the ignition plug 13 is forcibly cut off.

Following the processing in S200, the processing shifts to S150 again, and in S150, as described above, 2
It is determined whether or not the spark discharge time of the second time (counter i = 2) has been reached (the spark discharge interval Tb has elapsed). When the spark discharge occurrence time of the second time (time t4 shown in FIG. 2) is reached, S160 is performed. And a second spark discharge is generated.

By repeating the processes from S150 to S200 in this manner, spark discharge is continuously generated a plurality of times. Then, as described above, when the spark discharge is performed by the number of continuous spark discharges N calculated in S120,
An affirmative determination is made in the determination processing of S170, and the present ignition control processing ends.

In this embodiment, at time t5 shown in FIG.
, The second spark discharge is forcibly cut off, and at time t6, the third spark discharge is generated, and the ignition control process is terminated. Also, the third spark discharge
Naturally ends at time t7.

As described above, in the ignition device 1 for an internal combustion engine of the first embodiment, the ECU 19 controls the output of the first command signal Sa by performing the above-described ignition control processing, and controls the transistor 17 to operate. By performing the switching drive continuously a plurality of times, a multiple discharge in which the spark discharge is continuously performed a plurality of times can be realized. This multiple discharge makes it possible to burn off carbon attached to the plug.

Here, in the ignition device for an internal combustion engine of the first embodiment, an ignition plug having a spark cleaning action is used as the ignition plug, and carbon attached to the insulator surface of the plug is burned off by spark discharge. The effect can be further exhibited. Here, the spark plug that has a spark cleaning action is designed with a plug gap designed so that when carbon adheres to the insulator surface, the sparks fly along the insulator surface, burning off the carbon and spark discharge. Refers to a spark plug that has been used. As an example of the structure of the spark plug having the spark cleaning action, a spark discharge is always carried out along the tip end face of the insulator so as to face the tip side face of the center electrode protruding from the tip end face of the insulator. A so-called semi-creeping spark plug in which a plurality or annular ground electrodes are provided as described above. In addition, when carbon adheres to the surface of the insulator so as to face the side surface of the front end of the center electrode protruding from the end surface of the front end of the insulator, a spark discharge is generated along the side surface of the front end of the insulator to prevent insulation. When the body surface is clean, there is a so-called intermittent discharge type ignition plug in which a plurality of ground electrodes are provided so as to cause a spark discharge in an air gap between the center electrode and the end face of the tip. Further, there is a plug other than the plug gap formed by the center electrode and the ground electrode, in which spark discharge is generated when carbon adheres to the insulator surface to form a spark auxiliary gap for burning off carbon.

Further, the ignition coil 15 of the first embodiment
When the spark discharges are terminated naturally,
In the first spark discharge, the spark duration from the generation of the spark discharge to the interruption thereof is set to 1 mSec in order to ensure that the ignition of the air-fuel mixture is performed. More than that. Further, even in a state where carbon adheres to the spark plug 13 and spark discharge is likely to occur, spark ignition can be generated between the plug gaps, and a sufficiently high ignition high voltage, specifically, It is set so as to generate a spark discharge by applying a high voltage for ignition of 50 kV or more to the ignition plug 13.

For this reason, the ignition of the air-fuel mixture is ensured in the first spark discharge. However, if the ignition of the air-fuel mixture is not performed normally due to the contamination of the plug, 2 Since the mixture can be ignited by the spark discharge after the first time, misfire can be reduced, and good operation of the internal combustion engine can be realized.

On the other hand, the multiple discharge also causes the electrode of the spark plug to be consumed more quickly. However, in the first embodiment, the number N of continuous spark discharges is calculated according to the operating state of the internal combustion engine. In an operation state in which ignition performance is excellent, such as an operation at a high rotation, the number of continuous operations is calculated to be small, and unnecessary electrode consumption can be suppressed.

In addition to the number N of continuous spark discharges, the spark duration Tt and the spark discharge interval Tb of each spark discharge are also calculated according to the operating state of the internal combustion engine. The total spark duration to be performed can be determined.However, since the overall spark duration is calculated to be shorter as the driving state with excellent ignitability, such as high-speed operation, is calculated, While realizing good ignition, it is possible to suppress the consumption of unnecessary spark energy,
Further, unnecessary electrode consumption of the ignition plug can be suppressed.

Therefore, according to the ignition device for an internal combustion engine of the first embodiment, the carbon adhering to the insulator surface of the plug can be burned off, thereby preventing the plug from being contaminated. By calculating the condition,
It is possible to realize good ignition of the air-fuel mixture and to suppress wasteful consumption of spark energy and wasteful consumption of electrodes of the spark plug.

Although the first embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.
Various embodiments can be adopted. Further, in the ignition device for the internal combustion engine of the first embodiment, the last spark discharge of the spark discharges performed continuously a plurality of times is naturally terminated at the combustion timing of one combustion cycle. In order to suppress wasteful consumption, it is possible to forcibly cut off the last spark discharge by flowing the primary current i1 again. However, this increases the energization time of the transistor 17 and increases the amount of heat generated by the transistor 17, which adversely affects the life of the transistor 17. In order to avoid this heat generation, the transistor 17
Is turned off to cut off the primary current i1, spark discharge may occur again, and wasteful spark energy is consumed.

Then, as a second embodiment of the present invention, the last spark discharge is forcibly cut off by re-energizing the primary current i1, and the re-energized primary current i1 is gradually reduced. A possible ignition device for an internal combustion engine will be described. FIG. 4 is an electric circuit diagram showing the configuration of the internal combustion engine ignition device of the second embodiment. In the following description, the same components as those in the first embodiment will be described with the same reference numerals (reference numerals).

As shown in FIG. 4, the ignition device 1 for an internal combustion engine according to the second embodiment has a discharge electric energy (for example, a voltage of 1).
2V), a spark plug 13 provided in a cylinder of the internal combustion engine, and a primary winding L1.
An ignition coil 15 composed of a secondary winding L2, an npn transistor 17 connected in series with the primary winding L1,
A spark discharge shutoff circuit 31 for forcibly interrupting spark discharge;
For the transistor 17 and the spark discharge cutoff circuit 31,
An electronic control unit (hereinafter, referred to as an ECU) 19 that outputs the first command signal Sa and the second command signal Sb.

That is, the ignition device for an internal combustion engine according to the second embodiment is a full transistor type ignition device in which a spark discharge cutoff circuit 31 is added to the ignition device for an internal combustion engine according to the first embodiment. The spark discharge cutoff circuit 31 has an emitter connected to ground, a base connected to the ECU 19, a collector connected to the primary winding L1 via the capacitor 37, and an np grounded via the diode 33.
It is composed of an n-type transistor 35. The diode 33 has an anode grounded and a cathode connected to the collector of the transistor 35.

Therefore, the second output from the ECU 19
When the command signal Sb is at a low level, the transistor 35 in the spark discharge cutoff circuit 31 is turned off, and the spark discharge cutoff circuit 31 does not flow the primary current i1 to the primary winding L1. When the second command signal Sb is at a high level, the transistor 3 in the spark discharge cutoff circuit 31
5 is turned on to form an energization path of the primary winding L1 from the positive side of the power supply 11 to the negative side of the power supply 11 through the primary winding L1 of the ignition coil 15.
A primary current i1 is passed through 1. Then, as the electric charge is accumulated in the capacitor 37 present in the energization path, the primary current i
1 gradually decreases, and the primary winding L1
When a predetermined amount of electric charge is accumulated with a constant time constant determined by the inductance of the capacitor 37 and the capacitance of the capacitor 37, the current stops flowing through the capacitor 37, so that the primary current i1 is cut off. However, if the capacitor 37 is charged with the electrode connected to the primary winding L1 being positive, the second
Even if the command signal Sb is at a high level, the primary current i1 does not flow, so it is necessary to discharge the electric charge accumulated in the capacitor 37 in advance.
By setting a to a high level, that is, turning on the transistor 17, the electric charge accumulated in the capacitor 37 can be discharged.

Therefore, when the second command signal Sb changes from the low level to the high level in a state where the capacitor 37 of the spark discharge interrupting circuit 31 is discharged, the transistor 35 is turned on, and the primary current flows through the primary winding L1. i
1 and the electric charge is accumulated in the capacitor 37 with the passage of time, and the primary current i1 is gradually decreased, and finally, the primary current i1 is cut off. The reason why the primary current i1 can be gently reduced in this way is because the capacitor 37 is provided in the spark discharge cutoff circuit 31, and in the second embodiment, the capacitor 37 is defined in claims. Corresponds to the current adjusting means.

FIG. 5 shows the first command signal Sa, the primary current i1 flowing through the primary winding L1 of the ignition coil 15 and the second current in the ignition device for an internal combustion engine of the second embodiment shown in FIG.
5 is a time chart illustrating states of a command signal Sb and a potential Vp of a center electrode 13a of a spark plug 13; FIG. 5 shows an example in which the spark discharge is continuously performed three times at one combustion timing of the internal combustion engine.

Such spark discharge is performed by an ignition control process executed by the ECU 19, and the ignition control process will be described with reference to a flowchart shown in FIG. The ECU 19 is for comprehensively controlling the spark discharge timing, the fuel injection amount, the idling speed, and the like of the internal combustion engine. Like the ECU 19 of the first embodiment, the ECU 19 separately performs an operation state detection process. Is going.

The ignition control process shown in FIG. 6 is, for example, based on a signal from a crank angle sensor for detecting the rotation angle (crank angle) of the internal combustion engine, similarly to the ignition control process of the first embodiment. The engine is executed once per combustion cycle in which intake, compression, combustion, and exhaust are performed.

Then, from S110 to S20 in FIG.
The processes up to 0 are the same as those in the flowchart of the first embodiment shown in FIG. 3, and in the second embodiment, a plurality of continuous spark discharges are performed. Times t11 to t1 in FIG.
6 correspond to times t1 to t6 in FIG. 2, respectively, and the processing performed by the ECU 19 of the second embodiment during that time is the same as the processing performed by the ECU 19 of the first embodiment.

However, in the first embodiment and the second embodiment,
The processing after the last spark discharge is different, specifically, the processing after a positive determination in S170,
In the first embodiment, the ignition control process is terminated. In the second embodiment, after the spark discharge is forcibly terminated, a process of gradually reducing the primary current i1 is performed. Therefore, in the processing performed in the second embodiment, the description of the ignition control processing from the time when the last spark discharge is generated and the processing shifts to S170 will be described below.

In FIG. 6, at S170, the counter i
Is determined to have reached the number N of consecutive spark discharges, and if an affirmative determination is made, the process proceeds to S310. In S310, the spark discharge occurrence timing of the Nth spark discharge is affirmatively determined in S150, and the last is determined. After the spark discharge is generated, it is determined whether or not the spark duration Tt obtained in S120 has elapsed. If a negative determination is made, the same step is repeatedly executed, whereby the spark duration Tt elapses. Wait for And S
If it is determined at 310 that the spark duration time Tt has elapsed (time t17 shown in FIG. 5), the flow shifts to S320 to invert the first command signal Sa from low to high level.

As a result, when the first command signal Sa goes high, the transistor 17 is turned on, and the primary winding L1 is energized again, thereby suppressing the generation of an induced voltage in the secondary winding L2 and causing ignition. When the spark discharge at the plug 13 is forcibly cut off and the capacitor 37 is charged with the electrode connected to the primary winding L1 as a positive electrode,
The capacitor 37 is discharged.

Subsequently, in S330, after it is determined in S310 that the spark duration Tt has elapsed, the ECU 1
It is determined whether or not the high-level continuation time of the first command signal Sa set to 9 has elapsed. If a negative determination is made, the same step is repeatedly executed to wait. Then, in S330, when it is determined that the high level duration time of the first command signal Sa has elapsed (at time t1 shown in FIG. 6).
8) The process proceeds to S340. In the second embodiment, the high-level duration of the first command signal Sa is a fixed value that is set in advance regardless of the operating state of the engine, but is set to an appropriate value according to the operating state. You may.

Then, by the processing of S340, the first command signal Sa is switched from high to low level,
The second command signal Sb is switched from low to high.
Then, the transistor 17 is turned off, and the current flowing from the primary winding L1 to the collector of the transistor 17 is cut off. However, since the transistor 35 is turned on, a current flows from the primary winding L1 to the transistor 35 via the capacitor 37, so that the primary current i
1 flows continuously. Thereafter, the primary current i1 gradually decreases as the electric charge is accumulated in the capacitor 37 with the lapse of time, and when the capacitor 37 is charged with a predetermined amount of electric charge, the primary current i1 is cut off.

Then, in S350, after it is determined in S330 that the high-level duration of the first command signal Sa has elapsed, the high-level duration of the second command signal Sb preset in the ECU 19 has elapsed. It is determined whether or not the process has been performed. If a negative determination is made, the process repeats the same steps to wait. Then, in S350, when it is determined that the high level duration time of the second command signal Sb has elapsed (time t19 shown in FIG. 6), the process proceeds to S360.
In the second embodiment, the high-level duration of the second command signal Sb is a fixed value that is set in advance regardless of the operation state of the internal combustion engine, but is set to an appropriate value according to the operation state. It may be.

Then, when the second command signal Sb is switched from high to low in the process of S360, the transistor 35 is turned off, and this process ends. Here, the high-level continuation time of the second command signal Sb is set to be substantially the same as the time until the capacitor 37 is charged, and the primary current i1 is sufficiently small or cut off. By this processing, the primary current i1 is not suddenly cut off, and no spark discharge is generated in the ignition plug 13.

Here, the transistor 17 and the spark discharge cutoff circuit 31 supply a primary current for cutting off the last spark discharge, and correspond to the spark discharge cutoff means described in the claims. As described above, in the internal combustion engine ignition device 1 according to the second embodiment, the transistor 17 is switched a plurality of times in succession by the command of the ECU 19, so that the spark plug 13 generates the spark discharge continuously a plurality of times. Let me. Then, when the spark duration Tt has elapsed since the last spark discharge occurred, the ECU 1
9. The primary current i is again applied to the primary winding L1 of the ignition coil 15 by the transistor 17 and the spark discharge cutoff circuit 31.
1, the spark discharge is forcibly cut off, and thereafter, the primary current i1 is gradually reduced, and finally the primary current i1 is cut off.

Therefore, according to the ignition device for an internal combustion engine of the second embodiment, it is possible to continuously generate spark discharge a plurality of times, and to calculate the spark discharge condition according to the operating state of the internal combustion engine. Therefore, the same effects as those of the internal combustion engine ignition device of the first embodiment can be exhibited.

Further, in the second embodiment, wasteful spark energy consumption can be suppressed by forcibly interrupting the last spark discharge, so that electrode consumption of the spark plug can be suppressed. Also, the consumption of unnecessary spark energy is suppressed by gradually reducing the re-energized primary current so as not to generate useless spark discharge.

Furthermore, by gradually reducing and interrupting the re-energized primary current, the energizing time of the transistor after forcibly interrupting the spark discharge can be shortened, suppressing the heat generation of the transistor and reducing the load. It becomes possible.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram illustrating a configuration of an internal combustion engine ignition device according to a first embodiment.

FIG. 2 is a time chart showing the state of each part of the internal combustion engine ignition device of the first embodiment.

FIG. 3 is a flowchart illustrating a process executed by an electronic control unit (ECU) of the first embodiment.

FIG. 4 is an electric circuit diagram illustrating a configuration of an internal combustion engine ignition device according to a second embodiment.

FIG. 5 is a time chart showing the state of each part of the ignition device for an internal combustion engine of the second embodiment.

FIG. 6 is a flowchart illustrating a process executed by an electronic control unit (ECU) according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ignition device for internal combustion engines, 11 ... Power supply device, 13 ... Spark plug, 13a ... Center electrode, 13b ... Ground electrode, 15 ...
Ignition coil, 17 transistor, 19 electronic control unit (ECU), 31 spark discharge cutoff circuit, 33 diode, 35 transistor, 37 capacitor, D rectifier, L1 primary winding, L2 secondary Winding.

Continued on the front page (72) Inventor Shigeru Miyata 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi F-term in Japan Special Ceramics Co., Ltd. 3G019 AA09 BB08 BB10 CA00 CA01 CA02 EA17

Claims (7)

[Claims] An ignition coil having one end of a secondary winding connected to an ignition plug; a switching element for energizing and interrupting a primary current flowing through the primary winding of the ignition coil; energizing the primary current; An ignition control means for performing switching driving of the switching element in order to generate a high voltage for ignition in a secondary winding of the ignition coil by shutting off and to cause spark discharge of the ignition plug. An ignition device for an engine, wherein the ignition control means continuously performs the switching drive of the switching element a plurality of times at a combustion timing of one combustion cycle of the internal combustion engine, so that the ignition plug is continuously performed a plurality of times. Spark discharge, for an internal combustion engine. 2. The ignition control means according to an operation state of the internal combustion engine, wherein the primary voltage for ignition increases such that the higher the ignition high voltage is, the lower the ignitability of the ignition plug due to spark discharge becomes. The ignition device for an internal combustion engine according to claim 1, wherein the current is controlled. 3. The ignition control means according to an operation state of the internal combustion engine, such that the number of times of the continuous spark discharge increases as the ignition plug becomes less ignitable due to the spark discharge. The ignition device for an internal combustion engine according to claim 1 or 2, wherein the number of times of switching driving of the switching element is controlled. 4. The switching control device according to claim 1, wherein the ignition control means controls the switching so that an interval between the spark discharges becomes shorter as the ignition plug becomes less ignitable by the spark discharge depending on an operation state of the internal combustion engine. The ignition device for an internal combustion engine according to any one of claims 1 to 3, wherein a switching drive interval of the element is changed. 5. The spark plug according to claim 1, wherein said spark plug has a spark cleaning action.
The ignition device for an internal combustion engine according to claim 4. 6. The method according to claim 1, wherein the ignition control means generates a last spark discharge among spark discharges performed continuously a plurality of times,
Spark discharge interrupting means for forcibly terminating the spark discharge by re-energizing the primary winding; and The ignition device for an internal combustion engine according to any one of claims 1 to 5, further comprising: current adjusting means for gradually reducing the current. 7. The internal combustion engine according to claim 1, wherein the internal combustion engine is a direct injection internal combustion engine configured to directly inject fuel into a cylinder. Ignition device.