JPH0579444A - Non-contact ignition device - Google Patents

Abstract

(57) [Summary] [Object] The present invention efficiently dissipates heat generated from an ignition device when the ignition device is built into an ignition coil that becomes hot, and prevents malfunction of a power switching element. [Structure] A radiation fin is provided at a location intended to radiate heat from a power switching element in an ignition coil with a built-in ignition device. The area of the radiation fin on the surface of the ignition coil should be such that the power consumption is 1 W and the temperature difference from the air is 20 ° C. or less. [Effect] Since the minimum required amount of heat can be dissipated from the heat dissipating fins, the power switching element does not malfunction, and stable operation can always be obtained.

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, and more particularly to a heat dissipation structure of a power switching element integrally molded with an ignition coil and specific numerical values of a minimum required heat dissipation amount.

[0002]

2. Description of the Related Art In a conventional device, the heat dissipation structure of a power switching element molded in an ignition coil is insufficiently considered, and the structure does not satisfy the practical maximum temperature of the power switching element. or,
It also did not define the required minimum heat dissipation.

A power switching module has been integrally molded in the empty space of the ignition coil. The maximum temperature of the power switching element (MAX junction temperature) is 150 ℃, and the ambient temperature is 100 ℃.
In the case of, the heat radiation temperature needs to be 50 ° C. or higher.

[0004]

The above prior art does not consider the heat dissipation structure of the power switching element integrally molded with the ignition coil, and the MAX junction temperature of the power switching element is 150.
It is expected to exceed ℃. Seeing from its heat dissipation structure,
Since the heat radiation depends only on heat transfer into the air, a heat radiation area (fin) that sufficiently radiates the generated heat is provided in the mold part of the ignition coil, and the power switching element M
This is to prevent the temperature from exceeding the AX junction temperature, thereby prolonging the service life and obtaining high reliability.

The above-mentioned prior art has the drawback that the junction temperature of the power switching element and the ambient temperature difference are not defined as concrete numerical values and do not give design guidelines. In order to guarantee the junction temperature of MAX 150 ° C this time, if the temperature difference from the mold surface of the ignition coil to the air is kept within 20 ° C per 1W of ignition coil power consumption, it will be satisfied. Given specific design guidelines.

[0006]

In order to achieve the above object, the outer wall (plastic member) of the portion of the ignition coil that molds the power switching element is made fin-shaped. At this time, molding is performed with the iron base on which the power switching element and the HIC board are mounted on the fin side of the plastic member. The power switching element is soldered by stacking a stress relaxation plate, an insulating plate, etc. up to the base of the iron plate, and the heat flow is transmitted to the molding epoxy resin through the laminated member, the iron base, and the plastic type member. It is transmitted to the radiation fin,
Heat is dissipated into the air.

The area of the radiation fin is 45 mm × 45 mm for the power consumption of the ignition coil of 1 W.
To secure the area of. With this, 1W into the air
When the amount of heat generated is released, the temperature difference from the junction of the power switching element to the surface of the plastic member is within 25 ° C. Therefore, it becomes an ignition coil with one power switching element having a thermal resistance of 25 ° C./W from the outer wall of the plastic member.

If the heat radiation amount of 1 W can be sufficiently radiated from the fins, the thermal resistance from the outer wall of the plastic member to the power switching element will be about 25 ° C./W CAE.
This is based on simulation analysis.

The outer wall of the ignition coil (the portion where the power switching element is molded) has a laminated area of 30 mm × 30 mm, and the heat generation amount of 1 W cannot be dissipated into the air. However, 150 during normal operation
It exceeds ℃.

[0010]

The amount of heat radiated from the surface of the ignition coil can be calculated by the following equation in consideration of heat transfer into the air by natural convection.

Q = hAΔT (W) (Equation 1) h: Heat transfer coefficient A: Heat sink area ΔT: Temperature difference Therefore, if the heat transfer coefficient and temperature difference are the same, the area A of the heat sink is increased. The amount of heat radiation can be increased.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The ignition coil 1 has a primary winding 9 and a secondary winding 10. One of the primary windings 9 is a power source from a battery and the other is a power switching element 2 for driving an ignition coil (of a Darlington transistor type). MO
S-FET type). Further, the secondary voltage generated in the secondary winding 10 of the ignition coil 1 is guided to the spark plug 11. The ignition device (referred to as an igniter) shown in FIG. 3 has a power switching element 2 and a hybrid (HyIC) IC as shown in FIG.
The current limiting circuit is mounted on the power switching device 2 and the HyIC 7 in the present invention.
Is mounted on the metal base 6, ultrasonically bonded with the AL wire 4, and then covered with the Si gel 5. The ignition device, commonly called an igniter, is installed in the ignition coil 1 in a positional relationship as shown in FIG. 2, and an epoxy resin is enclosed together with the ignition coil 1 and integrally molded. At that time, since the external terminals of the ignition coil are electrically connected to the ignition device, a single wire is molded after connecting with an Ni wire or a lead frame for the purpose of heat dissipation and longer life.

The outer wall of the ignition coil is generally made of a plastic material, but the metal base 6 side of the ignition device is made to be the plastic material side, and the plastic material is used for heat dissipation. Radiating fin shape. At that time, the shape of the radiating fin secures an area such that the temperature of the ambient air and the ignition device is within 20 ° C. per 1 W of power consumption of the ignition coil 1. Since the heat quantity Q = hAΔT (W), Q =
1 (W), h = 25 W / m ² K (natural convection), temperature rise 2
Substituting 0 ° C = ΔT, the heat sink area A = 0.002 m
² and thus 45 × 45 mm. Since the above formula is a conclusion about the heat generation amount 1 (W), A must be increased as the heat generation amount increases.

On the other hand, the temperature difference from the junction portion of the power switching element 2 of the ignition device to the outer wall of the ignition coil 1 is such that even if the heat radiation fin and the lower surface of the metal base 6 are very close to each other, the epoxy is provided therebetween. Since resin is present, the power consumption of the ignition coil 1 is about 24 ° C. when the power consumption is 1 W. This is the value analyzed by CAE simulation. Therefore, in consideration of the engine room maximum temperature of 100 ° C., in order to keep the junction maximum temperature of the power switching element 2 within 150 ° C., the temperature rise must be 50 ° C. or less. When the amount of heat generation is 1 W, first, the temperature difference from the junction of the power switching element 2 to the outer wall of the ignition coil 1 is 24 ° C., and the temperature of the radiation fins provided on the outer wall of the ignition coil 1 is the ambient temperature. When the temperature difference up to the air of 20 ° C is added, it becomes 44 ° C, and the maximum temperature of the power switching element 2 is 150 ° C.
It is possible to supply a stable spark to the engine without satisfying the condition that the temperature is within the range of 0 ° C., so that the ignition coil 1 does not malfunction.

[0015]

According to the present invention, the heat generated by the power switching element is efficiently dissipated from the ignition coil, and the heat dissipating area and the minimum required heat dissipating amount are defined by specific numerical values. Is.

Also, since the junction temperature of the power switching element is 150 ° C. or less during the normal operation, the power switching element does not malfunction, and thus the ignition coil does not malfunction.

[Brief description of drawings]

FIG. 1 is an overall view of one body molded on an ignition coil.

FIG. 2 is a side view of FIG.

FIG. 3 is an enlarged view of an igniter incorporating (installing) a power switching element.

FIG. 4 is a circuit diagram using a Darlington type power switching element.

[Explanation of symbols]

1 ... Ignition coil, 2 ... Power switching element, 3 ... Radiating fin, 4 ... AL wire, 5 ... Si gel,
6 ... Housing base, 7 ... HyIC substrate, 8 ... Ignition igniter, 9 ... Ignition coil primary winding, 10 ...
Ignition coil secondary winding, 11 ... Spark plug.

Claims (3)

[Claims] 1. An ignition coil having primary and secondary windings arranged in a mold case, wherein a power switching element is soldered to a high thermal conductor such as metal so that heat is conducted into the mold case of the plastic member. It is attached with a structure, and the part of this mold case that touches the outside air is made into a fin shape,
Non-contact ignition characterized by having an ignition coil drive power switching element with a structure in which the amount of heat generated by the power switching element is conducted inside the molded case and is radiated outside the molded case by heat transfer by at least natural convection. apparatus. 2. The contactless ignition device according to claim 1, wherein the fin shape and area for radiating heat from the mold case surrounding the power switching element suppresses the temperature rise within 20 ° C. for 1 W of ignition coil power consumption. Non-contact ignition device. 3. The contactless igniter according to claim 1, wherein the surface area of the fin shape for keeping the temperature rise within 20 ° C. is required to be 45 mm × 45 mm or more in consideration of heat transfer in natural convection. Contact ignition device.