JPH02140910A - Capacitor discharge type ignition coil - Google Patents

Abstract

PURPOSE:To achieve compactness without reducing spark energy by installing a section bobbin where are secondary coil is wound around the outer periphery of an open magnetic circuit type magnetic core and by placing bobbins where a primary coil is wound around this outer periphery at certain intervals. CONSTITUTION:Since a bobbin 4 where a primary coil 6 is wound is placed at the outer periphery of a section bobbin 3 where a secondary coil 5 is wound. Combination between an open magnetic circuit type magnetic core 2 and a primary coil 6 is weakened and the primary inductance becomes smaller. On the other hand, combination between the open magnetic circuit type magnetic core 2 and the secondary coil 5 is strengthened and secondary inductance is increased since the open magnetic circuit type magnetic core 2 is formed by Mn-Zn material with small proper resistance, thus increasing continuation time of spark current when an ignition coil is driven. Also since energy conversion efficiency is enhanced, spark energy is increased and the diameter of the open magnetic circuit magnetic core 2 can be made smaller, thus miniaturizing the entire size.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an ignition device that ignites gaseous fuel or liquid fuel using spark energy, and is particularly suitable for use in capacitive discharge type ignition devices for residential equipment. The present invention relates to the structure of a capacitive discharge type ignition coil.

(Prior art) A capacitive discharge type ignition device converts electrostatic energy stored in a capacitor into electromagnetic energy in an ignition coil.
It's about getting a spark. In particular, this capacity discharge type ignition device does not need to store magnetic energy in the coil itself, so it is possible to reduce the overall number of turns compared to the conventional current interrupt type, and the ignition coil can be made smaller. It is possible to aim for

As shown in FIG. 3, this ignition coil includes a bobbin 4 with a primary coil 6 wound around the outer periphery of an open magnetic path magnetic core 2, and a secondary coil 5 wound around the outer periphery of the bobbin 4. A capacitive discharge type ignition coil having a section bobbin 3 is generally used.

Furthermore, as electronic capacitive discharge type ignition devices with built-in ICs have recently become widespread, there is a desire for higher efficiency, lower cost, and smaller size of the capacitive discharge type ignition coil 1. Incidentally, for this miniaturization, it is essential to reduce the inductance of the capacitive discharge type ignition coil 1. That is, in general, when the inductance of the primary coil of the ignition coil is Ll and the capacitance of the energy storage capacitor is C0, the oscillation frequency (fo) of the current flowing through the primary coil is expressed as follows.

Note that this vibration frequency changes depending on the magnetic flux that affects the output voltage and determines Ll. Also, this magnetic flux is usually
When the output voltage is constant, it is inversely proportional to the vibration frequency, so increasing the vibration frequency of the LC circuit by reducing L: and C1 in the above equation (1) is an effective way to downsize the capacitive discharge type ignition coil. This becomes an important element.

However, since the capacitance C8 is limited by the energy conversion efficiency of the ignition coil, it is necessary to reduce only Ll of the primary coil in order to keep the output voltage constant without reducing it.

(Problem to be Solved by the Invention) However, the capacitive discharge type ignition coil 1 is provided with the primary coil 6 on the outer periphery of the open magnetic path type magnetic core 2, and the coupling between the primary coil and the magnetic core 2 is strong. Therefore, it was not possible to reduce Ll. Therefore, there is a limit to the miniaturization of the capacitive discharge type ignition coil 1, a limit to the miniaturization of the capacitive discharge type ignition device equipped with this capacitive discharge type ignition coil, and a limit to the reduction in weight. Ta.

(Means for Solving the Problems) The present invention has been made in view of the above problems, and an object of the present invention is to provide a capacitive discharge type ignition coil that can be downsized without reducing spark energy.

The present invention is an ignition coil installed in a capacitive discharge type ignition device, in which an open magnetic path type magnetic core is formed from a magnetic core material made of Mn-Zn ferrite having a low specific resistance. A section bobbin with a secondary coil wound around the outer periphery is provided, and a bobbin with a primary coil wound concentrically with respect to the secondary coil is provided around the outer periphery of the section bobbin, with a gap for obtaining leakage reactance. The invention is characterized in that the gap between the section bobbins and the outer periphery of the bobbin are integrally molded with an insulating resin material.

(Function) The capacitive discharge type ignition coil having the above configuration is attached to a capacitive discharge type ignition device when used. This capacitive discharge type ignition coil has a bobbin wound with a primary coil arranged around the outer periphery of a section bobbin wound with a secondary coil, so that the connection between the open magnetic path type magnetic core and the primary coil is prevented. It is weakened and the primary inductance becomes small. On the other hand, since the coupling between the open magnetic circuit core and the secondary coil is strengthened, and the open magnetic circuit core is made of Mn-Zn material with low resistivity, the secondary inductance increases and the capacitance increases. When driving a discharge type ignition coil, the duration of the spark current increases.

However, since the primary inductance is small,
The current flowing through the switching element of the capacitive discharge type ignition device in this spark flash fault increases. However, since a gap is provided between the primary coil and the secondary coil to provide leakage reactance, this leakage reactance suppresses the increase in the current and prevents the spark energy from decreasing.

This will be explained in more detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a capacitive discharge type ignition coil. This capacitive discharge type ignition coil 1 has an open magnetic path type magnetic core 2 with
A section bobbin 3 is provided, a bobbin 4 is fitted on the outer periphery of the section bobbin at a predetermined interval, and the entire body is molded with resin, and is configured to be attached to a capacitive discharge type ignition device (not shown). ing.

The open magnetic path type magnetic core 2 is made of Mn-Z with a diameter of 4 to 5 mm.
It is formed of an n-based magnetic core material and can be used in a high frequency range suitable for a capacitive discharge type ignition coil.

That is, since this capacitive discharge type ignition device generally increases the voltage supplied to the primary side of the ignition coil attached to the ignition device, the number of turns of both the primary coil and the secondary coil is reduced. Therefore, the inductance is small, and the rise of the secondary voltage is several tens of minutes lower than in other systems, making it extremely fast. Therefore, even if the leakage resistance increases due to contamination of the spark plug, the change in the secondary discharge voltage can be reduced.

Comparing a closed magnetic path type magnetic core and an open magnetic path type magnetic core suitable for this capacitive discharge type ignition device, firstly, the closed magnetic path type magnetic core has a very large magnetic flux linkage due to its structure, so it has a large inductance. Become.

Therefore, it is suitable for a current interrupt type ignition coil. but,
Since the magnetic flux density is high, it is not suitable for the above-mentioned capacitive discharge type ignition device, and furthermore, the structure is complicated, so an increase in size is inevitable, and the cost is high.

On the other hand, open magnetic circuit cores have a simple structure, can be used in high frequency ranges depending on the materials used, are smaller,
Since it also leads to cost reduction, it is advantageous for adoption in a capacitive discharge type ignition device.

Next, we investigated core materials suitable for this open magnetic path type core. A specific magnetic material is Mn, which has high magnetic permeability, high magnetic flux density, and low loss in the frequency range below IMHz.
- Zn-based and Ni with high resistance 0 and low loss above IMHz
-There is a Zn type.

For example, there are two types of magnetic cores of this type: (manufactured by TDK) and H,S (manufactured by TDK). Table 1 below shows a comparison of each characteristic.

By the way, since the vibration frequency band in the above-mentioned capacitive discharge type ignition device is usually 20 to 200kl (z),
It was found that L, was not applicable, and H and S were within the preferred range. By using this ferrite magnetic core,
We were able to achieve high efficiency. Furthermore, since H3S has a large saturation magnetic flux density, when the number of turns is the same as that of a conventional product of the same shape, the tolerance for input current is higher than that of a conventional product. It has also been found that this has the advantage of allowing a large amount of magnetic energy to be stored depending on how the magnetic path is selected, leading to the miniaturization of the capacitive discharge type ignition coil.

The section bobbin 3 has a plurality of grooves 3a (five in this embodiment) formed on its outer periphery, and a secondary coil 5 is wound around each groove.

Then, it is fitted onto the outer periphery of the open magnetic path type magnetic core 2, and the magnetic core and the secondary coil 5 are brought close to each other. The bobbin 4 is ring-shaped and has an inner diameter slightly larger than the outer circumference of the section bobbin 3, and the primary coil 6 is wound several times around the recess 4a on the outer circumference. The insulating resin material is fitted around the outer periphery of the section bobbin 3 and positioned at the center in the axial direction, with a gap G between the secondary coil 5 and the primary coil 6 where a predetermined leakage inductance occurs. 7 is filled.

As the insulating resin material 7, an epoxy-based highly insulating synthetic resin is used, and the gap G between the section bobbin 3 and the bobbin 4 and the entire outer periphery of both bobbins 3 and 4 are integrally molded. As a result, the external shape can be made compact, and the open magnetic path type magnetic core 2 has a low specific resistance H3.
Even if S is used, it has a voltage resistance of about 20 kv/mm, so the problem of dielectric breakdown can be avoided.

Next, the relationship between the gap, leakage inductance, and output energy will be explained with reference to the graph of FIG. 4 showing an experimental example.

The characteristics of this graph indicate the change in leakage inductance corresponding to the gap G between the coils 5 and 6, which changes when the winding radius of the primary coil 6 is varied.

In this experimental example, a secondary coil 5 with an outer diameter of 13.5 mm is wound around the outer periphery of an open magnetic path type magnetic core 2 with a diameter of 6, and a primary coil 6 is further wound around the outer periphery of this secondary coil. A capacitive discharge type ignition coil 1 is used. Then, a power supply voltage of 100V was applied to the drive circuit of the capacitive discharge type ignition device shown in Figure 2.
The leakage reactance 13 was determined by measuring the primary inductance and primary leakage inductance when the voltage was applied. The output energy was also measured, and the measured value was compared with the output energy of a conventional capacitive discharge type ignition coil shown in FIG. As can be understood from the characteristics in the same figure, when the gap G is adjusted to about 2.2 mm so that the size of the primary leakage inductance is approximately 1/2 of the primary inductance, the optimal output energy is obtained. Obtained. Further, according to this experimental example, it was revealed that the output energy increased by about 30% for an input of 100V charged to the capacitor.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a drive circuit diagram of a capacitive discharge type ignition device equipped with a capacitive discharge type ignition coil.

In this drive circuit, a power supply voltage is applied between terminals a and b. A diode 8 for preventing backflow of charged charges is interposed between the terminal side and the connection point d. Further, between the connection points de, a switching element such as a cyrisk 9 to which a drive signal is input from the terminal C and a diode 10 that bypasses the oscillating reverse current are connected in parallel. Furthermore, a capacitor 11 that stores charge to be converted into electromagnetic energy is connected to the connection point e side, and a secondary coil 5 of the capacitive discharge type ignition coil 1 is connected to this capacitor and the connection point d.
is connected.

12 is a spark plug connected to the secondary coil. To explain the operation of the above drive circuit, first, terminal ab
A power supply voltage is applied to the capacitor 11 to charge the capacitor 11 via the capacitive discharge type ignition coil 1.

Next, when a switching signal is manually applied from the terminal C1 to the gate of the thyristor 9, the thyristor is turned on and discharged via the charge of the capacitor 11 and the capacitive discharge type ignition coil l. At this time, if the discharge current is large, the open magnetic path type magnetic core 2 may be saturated, the voltage waveform induced in the secondary coil 5 may be distorted, and energy transmission loss may occur.

However, this capacity discharge type ignition coil 1 has a primary coil 6.
Since the primary coil is arranged at the outermost periphery, the leakage reactor of the primary coil becomes one regardless of the current value, so that magnetic saturation can be suppressed.

Then, due to the LC of this drive circuit, oscillations continue several times, and a current in the opposite direction bypasses the diode IO.

On the other hand, the magnetic energy manually applied to the capacitive discharge type ignition coil 1 is taken out from the primary coil 6, transmitted to the secondary coil 5, and used by generating a spark from the gap of the ignition plug 12.

At this time, as described above, since the open magnetic path type magnetic core 2 and the secondary coil 5 are well coupled and the transmission loss is small, a large current easily flows through the open magnetic path type magnetic core 2. However, in the capacitive discharge type ignition coil 1, the inductance of the secondary coil 5 is increased, so this increase in current is prevented and the spark duration becomes longer. Furthermore, since the number of vibrations of the LC also increases, it is possible to increase the output energy.

Therefore, in the capacitive discharge type ignition device configured as described above, since the open magnetic path type magnetic core 2 of the capacitive discharge type ignition coil 1 and the secondary coil 5 are closely coupled, the open magnetic path type magnetic core 2 can efficiently extract the magnetic energy accumulated in
Energy conversion efficiency is improved. In addition, the secondary coil 5 is easy to wind and has a small winding radius, so the overall length can be shortened, reducing copper loss and temperature rise, further improving energy conversion efficiency. Since the distributed capacitance of the secondary coil 5 is also reduced and stabilized, distortion is less likely to occur in the output waveform. Therefore, it is advantageous for the capacitive discharge type ignition coil 1 in which the rise of the secondary voltage is sharp.

On the other hand, since the coupling between the open magnetic path magnetic core 2 and the primary coil 6 becomes loose, the internal resistance of the primary coil increases, but this reduces the time constant and reduces the rise of the secondary voltage. This becomes faster, which is advantageous for the discharge characteristics of the capacitive discharge type ignition coil 1. Further, since the primary coil 6 is located outside the secondary coil 5, it is easy to change the turns ratio according to the input voltage, and the bobbin 4 can be standardized, improving manufacturing efficiency. In this capacitive discharge type ignition coil 1, when the winding radius of the coil is kept constant, the primary inductance can be reduced as the diameter of the open magnetic path type magnetic core 2 becomes smaller, so that the vibration frequency is increased.

Furthermore, the diameter of the open magnetic path type magnetic core 2 is reduced, and the primary coil 6 with a small number of turns is arranged around the outer periphery of the secondary coil 5, which has a short overall winding length, so the overall size is reduced and the weight is reduced. significantly reduced.

Therefore, a capacitive discharge type ignition device equipped with this capacitive discharge type ignition coil 1 can be suitably used as an ignition device for residential equipment such as a water heater, a fan heater, a gas instantaneous water heater, and a gas range. In particular, when used in gas ranges, etc., conventionally, to prevent consumption of batteries used as power sources,
The number of ignitions of the spark plug has been reduced, but according to the present invention, the spark energy is large and the duration is longer, so there is almost no need to take into account problems during ignition. In addition, in recent capacitive discharge type ignition devices, the circuits are becoming electronic and there is a tendency to incorporate small capacity and ultra-compact power sources such as lithium batteries, so it is desired that the capacitive discharge type ignition coil 1 be made smaller. Ta. The capacitive discharge type ignition coil of the present invention can meet these demands, and can make the capacitive discharge type ignition device small and compact.

(Effects of the Invention) As described above in detail, the capacitive discharge type ignition coil of the present invention includes a secondary coil provided on the outer periphery of an open magnetic path type magnetic core, and a predetermined leakage on the outer periphery of the secondary coil. Since the primary coil is arranged with a gap to obtain reactance, the coupling between the open magnetic circuit core and the primary coil is weakened and the primary inductance becomes small, while the secondary inductance increases and The oscillation frequency of the secondary current is increased, and the sustainability of the spark current is greatly improved.

In addition, since the open magnetic path type magnetic core is made of Mn-Zn-based magnetic core material, the accumulated magnetic energy can be extracted efficiently, and the energy conversion efficiency is increased, resulting in an increase in spark energy. . In addition, the diameter of the open magnetic path type magnetic core can be reduced, the secondary coil can be shortened, and the number of turns of the primary coil can be reduced.
Since it is arranged around the outer periphery of the secondary coil, the entire capacitive discharge type ignition coil can be made smaller. Therefore, a capacitive discharge type ignition device equipped with this capacitive discharge type ignition coil has effects such as improved ignition performance and can be formed into a lightweight and compact structure.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, FIG. 1 is a longitudinal sectional view of a capacitive discharge type ignition coil, FIG. 2 is a drive circuit diagram of a capacitive discharge type ignition device, and FIG. 3 is a conventional one. FIG. 4, a vertical cross-sectional view of a capacitive discharge type ignition coil, is a graph showing the relationship between the gap and inductance of the coil according to the present invention.

Claims (1)

[Claims] (1) An ignition coil installed in a capacitive discharge type ignition device, in which an open magnetic path type magnetic core is formed from a magnetic core material made of Mn-Zn ferrite with low specific resistance, and the outer periphery of this open magnetic path type magnetic core is A section bobbin with a secondary coil wound thereon is provided, and a bobbin with a primary coil wound concentrically around the secondary coil is provided around the outer periphery of the section bobbin, with a gap for obtaining leakage reactance. A capacitive discharge type ignition coil, characterized in that the gap and outer periphery between the section bobbin and the bobbin are integrally molded with an insulating resin material.