JPH05164029A - Low-tension distribution overlapped discharge type ignition device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a device which certainly works is extremely simple and rationally inexpensive by directly connecting booster circuit output to all of series current circuits so as to apply booster voltage of a booster circuit simultaneously to all of the series current circuits consisting of ignition coil secondary windings and ignition plugs. CONSTITUTION:Booster voltage of a booster circuit consisting of a step-up transformer 11, a switching element 12 to chop a booster transformer primary electric current, a rectifier diode 13 to rectify and smoothen booster transformer secondary high pressure output and an oscillation circuit 10 to control on-off of a smoothing capacitor 14 and the switching element 12 is kept to be a voltage value lower than a discharge starting voltage value to cause dielectric breakdown to ignition plugs 1a-1d in an air intake process. Thereafter, booster circuit output is directly connected to all series circuits so that the booster voltage of the booster circuit is simultaneously applied to all of the series circuits respectively consisting of secondary windings of ignition coils 2a-2d and the ignition plugs 1a-1d.

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 having a plurality of cylinders, and more particularly to an ignition coil dedicated to each ignition plug for each cylinder or each pair of ignition plugs. In order to continue the discharge,
The present invention relates to an improvement in a low voltage distribution overlap discharge type ignition device that adds the output of a separately provided booster circuit to an ignition coil secondary voltage.

[0002]

2. Description of the Related Art A classic ignition device for a vehicle-mounted multi-cylinder internal combustion engine is
High voltage generated on the secondary side of one ignition coil is applied only to the ignition plug of the cylinder at the ignition timing, so it is a high-voltage distribution system that distributes electricity by the distributor, but increasing ignition energy improves combustion efficiency,
As a result, it leads to lower fuel consumption. Therefore, in such a high-voltage power distribution type ignition device, an ignition device having a stack discharge system has been proposed.

An example of such a conventional ignition device is shown in FIG. 2. This will be described below. After the ignition operation in one cylinder is completed, the next ignition operation in another cylinder occurs. Before starting, the control circuit 4 turns on the switching element 5, so that the DC output current from the battery 6 mounted on the vehicle passes through the key switch 7, which is naturally turned on during engine operation, and the ignition coil 2 Is poured into the primary winding and energy is accumulated. At a timing when ignition is required in any of the cylinders in accordance with the engine rotation angle signal 3 obtained from an appropriate sensor (not shown), the control circuit 4 turns off the switching element 5 to rapidly increase the primary current of the ignition coil 2. Shut off to generate a high voltage on the secondary side. At the same time, the distributor 9, which also has rotor contacts (not shown) that rotate in synchronism with the rotation of the engine, uses a total of four spark plugs that require ignition, such as the four-cylinder vehicle shown. One of the two spark plugs 1a to 1d is selected, and the above-mentioned high voltage on the secondary side of the ignition coil is applied to the spark plug 1a to 1d to generate a discharge spark in the spark plug. In other words, the high voltage generated on the secondary side of the ignition coil is sufficient to cause a dielectric breakdown of the ignition plug K in the cylinder near the end of the compression process.
Selected as a voltage value of v order.

On the other hand, the oscillating circuit 10 for switching the switching element 12 on and off at a predetermined cycle, the switching element 12
Step-up transformer 1 whose primary current is choppered by
1. A step-up transformer composed of a rectifier diode 13 for rectifying a step-up transformer secondary step-up current generated by the chopper ring of the primary current and a smoothing capacitor 14 for smoothing the step-up current have also started to operate, and after the start of discharge in the ignition plug, The boosted voltage is additively superimposed on the high voltage on the secondary side of the ignition coil to function to continue the discharge. The output voltage of the booster circuit (DC-DC converter) at this time is usually 2
Selected to ~ 3Kv.

However, in the case of a general current interruption type ignition device which does not adopt the overlapping discharge method, the discharge energy obtained in each spark plug is about 30 mJ.
On the other hand, if the above-mentioned overlapping discharge method is adopted,
In principle, discharge energy on the order of several times that amount should be easily obtained, and if this is the case, it will greatly contribute to improving combustion efficiency and reducing fuel consumption.

[0006]

However, in the case of the high-voltage power distribution system, a long high-voltage wiring cord is required between the secondary winding of the ignition coil 2 and the distributor 9 as shown in FIG. 2 in the first place. However, this can be equivalently replaced by the resistance line 80, and similarly, the long high-voltage wiring cords from the distributor 9 to the respective spark plugs 1a-1d can also be replaced by the resistance lines 8a-8d, respectively. Will be things. And such an equivalent resistance value 8
0,8a-8d are actually quite large, and as a result,
The loss of ignition energy at each high voltage cord is 60
It rises to about 70%. Therefore, even if only 30 mJ of discharge energy is obtained as described above, an ignition coil with an output of about 90 mJ is actually used, and the combined use of the overlapping discharge method can increase the spark plug discharge energy to, for example, 100 mJ. When trying to raise the voltage, a booster circuit having an output of 200 mJ had to be used in order to make up for 70 mJ to be added. in this way,
The high-voltage power distribution system is extremely inefficient, has to be a large-scale circuit device, has a high probability of generating electromagnetic noise, and may cause various electronic devices mounted on the vehicle to malfunction.

On the other hand, there is a system called a low-voltage power distribution system in the related art. In this system, each ignition plug is provided with one ignition coil for exclusive use, and power is distributed on the primary side of the ignition coil. I am trying. According to this method, since the ignition coil can be arranged directly on the head of the ignition plug, the high-voltage wiring cord is unnecessary, the efficiency is remarkably increased, and the occurrence probability of electromagnetic radiation noise can be greatly reduced. Also, since the power is distributed on the primary side of the ignition coil, it is easy to control electronically, and since mechanical moving parts such as the conventional distributor are not required, the failure probability is greatly reduced and the maintenance is easy. .. Such an advantage is more than compensated for the disadvantage that the ignition coil is required only for the number of cylinders. In fact, in recent years, this method is becoming mainstream. Not only one for each spark plug, but for a pair of spark plugs that are in the exhaust process when any one of them is in the compression process, the secondary winding of one spark plug is used. There is also a low-voltage distribution system that uses a so-called simultaneous ignition coil in which both ends of the wire are distributed and connected.

However, so far, no reasonable one has been provided on the market as an ignition device in which the overlap discharge method is further added to the low-voltage distribution type ignition device.
In one proposal, one booster circuit is provided for each ignition coil, but this is too unreasonable and is not realistic considering productivity, space factor, cost, and the like. According to another proposal, the output of a single booster circuit is selectively distributed to one of the ignition coils by a semiconductor switching element, but there is a problem in that a high voltage semiconductor switching element is required. Not practical. First, as a general technical common sense, it is doubtful that the output voltage of the booster circuit should be about 2 to 3 Kv even when the lap discharge method is incorporated into the low voltage distribution method, as in the case of using the high voltage distribution method together. Few had it. Therefore, at such a voltage value of the order, the boost plug output voltage alone causes the spark plug to start erroneous discharge, so that the boost plug output is not applied to the spark plug of the cylinder in the intake stroke in particular. The idea of using the switching element as described above appeared, but since there was no switching element satisfying this in the market, there was no low-voltage distribution stack discharge ignition device that was finally completed as a product. It can also be said.

The present invention has been made under such circumstances, and is an ignition device that employs a low-voltage power distribution system, and has a reliable operation, but is extremely simple. , It aims to provide the market with reasonable and inexpensive products.

[0010]

In order to achieve the above object, the present invention provides a booster circuit (DC-) which is provided separately from an ignition coil system as a low voltage distribution overlap discharge type ignition device for an internal combustion engine.
Although there is one DC converter), the boosted voltage of the booster circuit is limited to a voltage value lower than the discharge start voltage value that causes dielectric breakdown of the spark plug in the intake stroke. Then, the booster circuit output is directly applied to all the series circuits so that the booster voltage of the booster circuit is simultaneously applied to all the series circuits including the secondary windings of the ignition coils and the spark plugs. Connecting.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an embodiment of the present invention.
In the illustrated case, the low-voltage distribution type ignition device for a four-cylinder vehicle is illustrated as being modified according to the present invention. Therefore, there are four ignition plugs in total, and four ignition coils dedicated to each. Hereinafter, when the respective spark plugs and the ignition coils are specifically shown, reference numerals 1a, 1b, 1c, 1d with suffixes; 2a, 2b, 2c, 2
Although "d" is used, suffixes a, b, c, d are omitted in the case where any one can represent the other, and they are simply referred to as spark plug 1 or ignition coil 2, for example. This also applies to the constituent elements represented by other suffixed symbols.

This embodiment has the same components as those of an ordinary low-voltage distribution type ignition device, and these components do not need to be modified. That is, based on the engine rotation angle signal 3 obtained from a suitable known existing sensor means (not shown), the control circuit 4 has a total of four ignition coil primary current interruption switching elements 5 ,. Medium, by turning off the switching element 5 that is serially connected to the primary circuit of the ignition coil 1 for the cylinder that has reached the present ignition timing,
Due to the mutual induction principle, a high voltage output is generated on the secondary side of the ignition coil. The switching element 5 is npn in the illustrated case.
Although it is shown by the transistor 5, any so-called power switching element may be used, and there are also usage examples of a power MOSFET, a thyristor and the like.

However, the secondary voltage of the ignition coil generated only by the mutual induction principle due to the current interruption is
Sufficiently large to cause dielectric breakdown in the spark plug 1 to generate an initial discharge spark (usually on the order of several Kv)
However, in the case of discharge based only on this current interruption principle, the duration of the discharge was typically about 2 mS at most. On the other hand, according to the following additional circuit configuration and operation according to the present invention, large discharge energy can be obtained for a long time.

First, in terms of the circuit structure, the step-up transformer 1
1. A boosting circuit including a switching element 12 for choppering the primary current of the boosting transformer, a rectifying diode 13 for smoothing and smoothing the secondary high voltage output of the boosting transformer, a smoothing capacitor 14, and an oscillating circuit 10 for controlling ON / OFF of the switching element 12 ( DC-DC converter) is provided separately, but only one. Then, the boosted voltage of this booster circuit (obtained across the capacitor 14)
However, these four ignition coil secondary side series circuits are connected to the output of the booster circuit so that they can be applied to each of the four series circuits, each consisting of each ignition coil 2 and each ignition plug 1. Each of them is connected, and when viewed from both ends of the output of the booster circuit, the four ignition coil secondary side series circuits are connected in parallel and directly to each other.

Due to such a circuit configuration, the primary current of the ignition coil 2 at the ignition timing is cut off by the control circuit 4, and dielectric breakdown occurs at the secondary side of the ignition coil 2 at the ignition plug 1. A voltage equal to or higher than the discharge start voltage is generated, and after the spark plug 1 starts discharging, the oscillation drive circuit 10 starts to operate by a signal from the control circuit 4 preferably at a slightly delayed timing for a predetermined time. Then, since the primary side of the step-up transformer 11 receives the chopper ring by the switching element 12, a high-voltage output appears on the secondary side of the transformer, which is rectified by the rectifying diode 13 to generate an additional overlap discharge current.

As a result, the combined discharge current of the spark plug 1 can maintain a high energy level for a long time sufficient for ignition of the fuel, greatly improving the ignitability of the fuel and eventually improving the fuel consumption. Come in handy. The discharge duration can easily be 5 mS or more, and the continuous discharge current value can be 40 mA or more. However, of course, the determination of the discharge duration is a matter left to the optimum design to be made for each vehicle.

However, according to the configuration of the present invention, the booster circuit output and each ignition coil secondary side series circuit are directly connected without a switching element interposed therebetween. Therefore, the output of the booster circuit is simultaneously applied to all the spark plugs.
However, for example, the ignition coil 2a generates a secondary high voltage according to the current interruption principle, and the corresponding ignition plug 1
When a is starting to discharge, another spark plug 1b
~ 1d is not discharged and its equivalent impedance is extremely high. Therefore, even with the illustrated circuit configuration in which the booster circuit output is applied to all the spark plugs at the same time, the spark plug 1 that has actually started discharging
Only at a, there is a possibility that the overlapping discharge current from the booster circuit can be supplied. Nevertheless, in the past, such circuit configurations were either completely out of consideration or rejected.
One of the reasons is that it is premised that the output voltage of the booster circuit is set to 2 to 3 Kv when used in combination with the above-described high-voltage distribution system.

That is, if the output voltage of the booster circuit is set to such a high voltage order, dielectric breakdown occurs in each spark plug and discharge is started regardless of addition of the secondary voltage of the ignition coil. Therefore, if such erroneous ignition occurs especially in the cylinder in the intake stroke, it causes a serious problem in engine operation.

The inventor of the present invention has arrived at the present invention from the point of doubt about such conventional common general knowledge. That is, in the cylinder in each process, when the insulation of the spark plug was broken and the discharge start voltage at which the discharge was started was obtained, during the processes of compression, explosion, exhaust, and intake in the four-cycle engine, the cylinder The discharge start voltage was the lowest in the intake process in which the negative pressure environment was about 1.3 Kv. Therefore, if the booster circuit is designed with the conventional voltage order, it is clear that there is a high risk of misfiring in the cylinder during the intake stroke.However, conversely, the discharge start at the spark plug during the intake stroke is started. Voltage value less than voltage, eg 1
If it is designed to keep the upper limit of the booster circuit output voltage to about Kv, a simple circuit configuration is adopted in which the booster circuit output is simultaneously applied to all the spark plugs as shown in FIG. However, the output current from the booster circuit can be overlapped only with the spark plug that has actually started discharging.

Here, in adopting the circuit configuration of FIG. 1 according to the present invention, the case where the output voltage Vo of the booster circuit is set to 1 Kv will be examined from another point of view. Normal,
After the start of discharge, the lowest voltage (discharge sustaining voltage) Va required to continue the discharge is generally about 500 to 600V. Further, as also shown in FIG. 1, a noise prevention resistor R _P of about 5 kΩ is inserted between the ignition coil secondary winding and the ignition plug 1 in the low voltage distribution system, but considering the upper limit of the variation. The maximum value R _Pmax of the lever is set to 6.5 KΩ, and further, the overlap discharge current Io from the booster circuit is designed to obtain a minimum of 40 mA based on past knowledge, and the upper limit Io _{max of} the variation is increased by 10% to 44 mA. (By the way, there is an experimental result that the blow-off phenomenon occurs when it is lowered to about 35 mA or less).
2d is the secondary coil resistance R2, R2 <{(Vo- Va max) / Io max -R Pmax} ≒ 2.
It is required to be 6 KΩ, and in order to guarantee this at 120 ° C., the secondary coil resistance should be set to 1.9 KΩ or less at room temperature from the temperature characteristics of the copper wire. This is a sufficiently feasible number to set the booster circuit output voltage Vo to 1 Kv.

Although one embodiment of the present invention has been described above, the present invention also applies to an ignition device using a so-called simultaneous ignition type coil in which one ignition coil applies discharge energy to two ignition plugs at the same time. Clearly applicable. Also, as for the booster circuit, the one shown in the figure only shows a circuit configuration example belonging to the simplest category,
Any DC-DC as needed, not in a limiting sense
A converter configuration may be adopted.

[0022]

According to the present invention, a low voltage distribution type,
Further, it is possible to provide an igniter having both the overlapping discharge system and the market with a simple configuration in a feasible manner. Then, as in the conventional high voltage power distribution repeated discharge method, in order to obtain ignition energy of about 100 mJ in the spark plug, it is not necessary to use an extremely large booster circuit as in the conventional example, and in principle, A small booster circuit that can supply about 70 mJ, which is increased by the principle of repeated discharge, is sufficient. Furthermore, since the booster circuit does not need to intervene a switching element by a simple wiring operation and only needs to be connected to the secondary side of each ignition coil, the assembling work is simplified and the cost is reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a low voltage distribution overlapped discharge ignition device of the present invention.

FIG. 2 is a schematic configuration diagram of an example of a conventional high voltage power distribution overlap discharge type ignition device.

[Explanation of symbols]

1 spark plug, 2 ignition coil, 4 control circuit, 5 primary current cutoff transistor, 11 step-up transformer, 12 step-up transformer switching element for primary current chopper ring, 13 rectifier diode, 14 smoothing capacitor.

Claims (1)

[Claims] 1. An ignition coil for a multi-cylinder internal combustion engine, wherein a dedicated ignition coil is used for each ignition plug for each cylinder, or a dedicated ignition coil is used for each pair of ignition plugs.
After generating spark discharge in the corresponding spark plugs by the secondary voltage of each ignition coil, by adding the boosted voltage of the booster circuit separately provided, the low-voltage power distribution overlap discharge type for internal combustion engine An ignition device, wherein a single booster circuit is used, and the booster voltage of the booster circuit is kept at a voltage value lower than a discharge start voltage value that causes dielectric breakdown in the spark plug in the intake stroke; Boosted voltage of
Connecting the booster circuit output directly to all of the series circuits so that they are simultaneously applied to all the series circuits of the ignition coil secondary windings and the spark plugs;
Low-voltage power distribution stack discharge ignition device for internal combustion engine.