GB2165398A - Electronic module for ignition systems of motor vehicles - Google Patents

Abstract

An electronic module structure (4) is made up by a metallic body (5, 7), working as thermic radiator, which is fixed to the ignition distributor body (1) of a motor vehicle by means of a heat insulating support (6). Thus the module temperature is not affected by the distributor temperature and, owing to the effect of the radiator body (5, 7), it is kept within values compatible with the temperature of its components. <IMAGE>

Description

SPECIFICATION Electronic modulefor ignition systems of motor vehicles The present invention relates to an electronic module structure and its relevant assembly in the ignition distributor for internal combustion engines, particularly for motor-vehicles.

As it is well-known, the electric motor-vehicle ignition plants are supplied with an electronic module thatformsthe ignition bobbin control device and, for getting this object, it is electrically connected, on one side,tothedistributor propulsor and, on the other side, to the vehicle battery.

One of the problems related to the electronic module design is to avoid its extreme heating that is harmful for its electronic components.

To keep the heating within acceptable limits, the well-known devices are manufactured using a metallic plate that is assembled in contact with a metallic support suitablefordissipating the heat generated by the module. Then the electric connection between the module and the distributor is carried out by a cable.

Yetthissolution requires a proper cooling support and a connection cable whose presence involves obviously some problems concerning its cost and overall dimensions.

With the aim of eliminating the proper support and the cable, itwas proposed that the module were attached directlyto the distributor. In this way the metallic plate of the module is directly in touch with the distributor body that, further, can be used as heat dissipating support.

But, during the practical running,the distributor body is heated by the thermic motor on which it is assembled and therefore the direct contact between the metallic module plate and the distributor body produces the heat passage from the distributor to the module, whose temperature depends not only on the heating of its electronic components, but also on the distributor heating.

In practice the module is substantially kept at the distributortemperature; now, if this condition does not produce drawbacks during the vehicle ride, as the natural ventilation assures a sufficient cooling of the distributor and then ofthe module, it is no more acceptable when the vehicle stops and the motor is still running, particularly after a ride in speedway or in slope, asthe distributortemperaturecan achieve, when the ventilation lacks and owing to the "heat shock", very high peaks that are not compatible with the electronic module components.

SUMMARYOF THE INVENTION The primary object of the present invention is to provide an electronic ignition module structure and its assembly on the ignition distributorwhich has none of the ahove-mentioned drawbacks whatever the vehicle ride and thermic engine running conditions are.

Particularly the object the invention is to keep the moduletemperature and its gradients independent of the distributor ones, keeping the temperature within values compatible with its electronic components.

The above mentioned object ofthe present invention is achieved by an electronic module structure made-up bya metallic body working asthermic radiator, suitable for dissipating the heat generated by the electrode module components towards the outside and fixing this structure to the ignition distributor body by means of an intermediate heat insulating means, so that it is eliminated the direct heat transmission of the thermic engine through the distributor body.

According to a simple preferred embodimentofthe invention, the radiator body shows the shape of an open box, whose inside is partially occupied by the electronic module components and itis partially available for the electric connections. Preferably the thermic insulation means is made-up by a support haveaframeshapethatformsa closing surface of the internal side of the radiator body for getting the module protection.

Further advantages and characteristics ofthe mod ule structure and assembly will be better explained in the following description and annexed drawings that refer to a preferred (but not limitative) embodiment of the invention.

BRIEFSUMMARYOFTHEDRAWINGS The drawings show: - Fig. lisa lateral schematic view of an ignition distributor represented in partial cutaway view in the a & a ofthe electronic module.

- Fig. 2is aplan view ofthe distributorshown in Fig. 1, with cutaway representation ofthe electronic module area.

- Fig. 3 is a plan view of the external module side.

- Fig. 4 is a view the modular system shown in Fig.

3, illustrating the terminals zone.

- Fig. 5 is a plan view of the internal module side.

-Fig. 6 is a cutaway view along the line VI-VI ofthe module shown in Fig. 5.

- Fig. 7 shows by means of the diagram T (centigrade degrees) - minutes (min.), the temperature variation ofthe distributor body, of the electronic module body and ofthe environmental temperature, that occur during a vehicle ride condition.

-Fig. 8 shows the diagram indicated in Fig. 7 considering anothervehicle ride condition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ignition distributor is supposed to be assembled on a thermic engine of a vehicle and is shown schematically in the Fig. 1 and 2, in which: 1 shows the cylindrical body, normally made of aluminium, 2 indicates the distributor cap and 3 is the propulsor, which can be of any well-known type, e.g. ofthe magnetic type (magnetic propulsor), mechanical type (contact breaker) or using the Hall effect.

4 shows the electronic module including, according to the invention, a metallic box or body 5 made of heat dissipating material, e.g. aluminium, that is connected to the body 1 of the distributor by means of a heat insulating means 6.

The body 5 shows the shape of an open boxwith at least an external surface supplied with cooling fins 7.

The inside ofthe box 5 is partially-see8-occupied bythe electronic module components and is partially -see 9-at disposal forthe electric connections 10.

The electronic module components are buried into a mechanical protection resin andformtogetherwith it a mass 11 placed in the box space 8.

The module terminals 12 are connected, on one side, to the propulsor3 by the connections 13 and, on the other side, to the electronic vehicle plant by means ofthe connections 14" and, in particular, to the ignition bobbin andthefeeding battery (not shown).

The electronic module function is well-known: it processes the phase signal transmitted bythe propulsor3 and disconnects the current stream in the bobbinattheignition momentTomakeeasierthe access to the space 8, the body 5 shows, on the bottom, a lateral opening 1 Gthat will be closed byan insulating means wall 6, as described afterwards.

The box body 5 togetherwith the wall 11 is assembled turning the open side towardsthe body 1, using a plate 6 thatsets-up the heat insulating means interposed between the said body 1 and the module 4.

In such a way the distributor heat cannot be transmitted to the module by conduction and thereforethetemperature of this last one is practically independentofthedistributortemperature in all running conditions ofthe thermic engine and of the motor-vehicle ride.

Naturally, forbeing ableto satisfythis condition, it is necessary to select suitably the thickness and the material ofthe insulating plate 6, e.g. thermosetting polyesther.

Asthemodule4is no more influenced bythe distributor heating, itstemperature will depend only on the heating of its electronic components.

To keep this heating within allowable limits, the radiator body 5 is supplied, as above said, with cooling fins 7 whose dispersing surface is obviously calcu latedto guaranteethiscondition.

Furtherthe plate 6 has the object of establishing a protecting surfaceforthe electronic module part and fu rther fo r closing the spaces 8 and 9.

Considering a simple embodiment, the plate 6, as the Fig. 1 and 2 show, has the shape of a frame whose edge, on one side, is in touch with the distributor body 1 and, on the opposite side, is in touch with the internal edgeoftheradiatorbody5.

The frame allows to have at disposal a space 15 (see Fig. 1 ) between the body 1 and the module 4that, besides making easierthe introduction and connection operations ofthe cables 13 and 14, carries out an air space between distributor and module, which is suitable for limiting the heat transmission between these parts.

Furthermore, to make easier the access to the space 9 during the above mentioned operations, the radiator body 5 shows a lateral opening 16, or a bottom opening which, afterthe module assemblyto the distributor, is closed by a protruding wall 17, that is a part ofthe plate orframe 6. In such a waythe inside of the box Sand particularly the space 9 are protected against water splashes, foreign bodies, etc..

The Figures from 3to 6 showthe module 4 as a sole unit, i.e. seperated from the distributor. The above ) mentioned figures use the same reference symbols forthe corresponding parts. The module 4 structure assembly on tha distributor body by means ofthe insulating frame 6 can be made in whateverwellknown way, e.g. by screws, rivets orthe like.

The Figures 1 and 2 show an assembly oftheframe 6 to the distributor body by means ofthe screws 17, and ofthe module body to the frame 6 by means of the screws 18.

Some practical tests were carried out to verify the heat transmission ofthe electronic module manufactured and assembled according to the invention.

The distributor with relevant module was assembled, during thetests, in a thermic engine for motor-vehicle in ride atthe environmental tempera ture of 300C.

The results of these tests are shown in the diagrams ofthe Figures 7 and 8 in which the curves A-A', B-B' and C-C' show respectively the temperature variation ofthe distributor body 1, ofthe module body 5 and of the distributorsurroundings, e.g. the space underthe engine bonnet, versus time.

TEST NO. 1 It is shown in the Figure 7.

It relates to the temperature surveys made on a motor-vehicle in ride on speedway at the maximum speed and afterits stop 28 minutesfrom the start.

It can be immediately noticed thatthe curve B, showing thetemperatures of the body 5 of the module 4, both during the ride and afterthe stop ofthevehicle, is always underthe curve A.

Ashorttime before the stop, the body 1 temperature (see curve A) does not exceed 90 C and this is due to the natural ventilation produced by the vehicle movement.

But, after a ride of 28 minutes, atthevehicle stop moment, the curve A undergoes a quick increase due to the "heat shock" that occurs in the distributor body owing to the ventilation lack and the heat transmitted bythethermic motor.

During this phase, thetemperature of the body 1 reaches and exceeds 1 20 C.

Thetricks suggested by the invention, thatforesee, on one side, the thermic insulation ofthe module 4 from the distributor body by means oftheframe 6 and, on the other side, an efficient module heat dissipation by means ofthe finned body 5, the curve B, as the diagram shows, is kept underthe curve A of 25-30 C, both during the continuous vehicle ride and afterthe vehicle stop.

Furtherthethermicgradienttaken on the module during the start phase ofthe "heat shock" (slope gradient of the curve B in comparison with the curve A) is notably lower than the gradientthatwould be got when the module is directly assembled on the distributor.

These two effects of lower temperature and lower thermic gradientallowto get a notable advantage in the exercize reliability of the electronic module components.

Furtherthe diag ram shows the curve C that represent, as above said, the temperature variation in the space which holds the distributor.

The course ofthis curve justifiesthe one ofthe curve B,that depends strictly on the environmental air temperature.

TEST NO. 2 It is shown in Fig. 8.

It refers to the temperature surveys made on a motorvehicle during a mountain ride with maximum load and after its stop. Also in this case it is tested a curve B', always underthe curve A', even if the temperature values are higherthanthe ones of the curves A and B ofthe diagram shown in Fig. 7, owing totheheaviervehicle ride conditions and the reduced ventilation ofthe engine space caused bythe low speed. This produces a lowertemperature increase afterthe stop as regards the curves A' and C' and the consequent quicker adaptation of the curve B' to the curve C'.

Claims (6)

1. Electronic module structure and its assembly in the ignition distributorfor internal combustion engines, particularlyfor motor vehicles, characterized in thatthe structure is made up by a metallic body (5), working as thermic radiator, which is fixed to the distributor body (1 ) through an intermediate insulat ing means (6); this radiator being ableto dissipate the heat generated bythe electronic module components (11) towardsthe outside.

2. Electronic module structure according to Claim 1, characterized in that at least a radiator (5) body surface shows some cooling fins (7) on the external side.

3. Electronic module structure according to Claims 1 1 and 2, characterized in that the radiator body shows the shape of an open box whose inside (8) is partially occupied by the electronic module (11) components and is partially availableforthe electric connections (10).

4. Electronic module structure according to Claim 3, characterized in that the box shows a lateral opening (16)forthe access to the space (9) of electric connections (1 0).

5. Electronic module structure according to Claims 1 1 and 3, characterized in thatthe intermediate heat insulating means is made-up by a plate (6), which determines a protection surface of the inner side of the boxbody holding the module(11).

6. Electronic module structure according to Claims 4 4and 5, characterized in thatthe plate has a frame shape (6), showing a protruding wall (17)forthe closing ofthe lateral opening (16) ofthe box body and that realizes an airspace (15) between the distributor body (1 ) andthe module (11).