Abstract:
Positioning of sensitive electronics near the engine block is accomplished through the use of a heat shield providing for removal or diversion of transmitted heat from the block to the electronics through the use of a self-contained or externally circulated coolant fluid. Unlike conventional coolant channels in an engine block, the heat shield is not intended to cool the engine block and thus may be more compact insofar as it deals with lesser heat flux.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Provisional Appln. No. 60/130,860, filed Apr. 22/1999. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     FIELD OF THE INVENTION 
     The present invention relates to electrical systems for automobiles and the like and, in particular, to a protective heat shield for protecting temperature sensitive electronic components from engine heat. 
     BACKGROUND OF THE INVENTION 
     Present day automobiles and other vehicles make use of sophisticated electronics for engine control and monitoring. Typically one or more microprocessor-based electronic control units collect engine data from sensors located in different points on the engine and about the engine compartment. The control unit executes a stored control program to produce control signals for actuators such as fuel injectors, throttle plate spark coils and the like. 
     The complex circuitry of the control units is temperature sensitive and thus may be mounted in a cooler portion of the engine compartment, typically against or within the firewall to provide the desired reliability of the electronics. A lengthy and complex wiring harness is necessary to communicate between the control unit and its associated sensors and actuators. 
     This wiring harness could be significantly shortened and simplified if the control modules could be moved to the engine. While in some cases it is possible to obtain high temperature components that may withstand engine temperatures, these parts can be unduly expensive, and high temperature versions of some components, such as electrolytic capacitors, are not readily available. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a fluid cooled heat shield that permits proximate mounting of heat sensitive control electronics on or near the engine. The shield may be relatively compact because it is not intended to cool the engine but only to block a limited path of heat flow to the sensitive electronic components. By placing temperature sensitive control components in the “heat shadow” of the shield near the engine, wiring harnesses are reduced in length and simplified. 
     Specifically, the invention provides a system for protecting temperature sensitive vehicle electronics from engine heat by using a heat shield positioned, at least in part, between the control electronics and a high temperature engine component, wherein the heat shield includes a chamber holding a coolant fluid and providing a path of fluid circulation within the chamber for the removal of heat therefrom. 
     It is thus one object of the invention to provide a compact thermal barrier permitting sensitive electronics to be positioned close to the engine. 
     The chamber may include an inlet and outlet port and the coolant fluid may be an engine fluid, for example, transmission fluid, radiator fluid, ambient air or engine intake air, pumped through the chamber between the inlet port and the outlet port. 
     Another object of one embodiment of the invention is to provide a heat shielding system that may make use of cooling systems normally associated with the automotive engine. 
     In an alternative embodiment, the chamber may be sealed and include a radiating end having at least one fin and the fluid may be selected from those having vaporization temperatures below the temperature of the high temperature engine components so as together, with the chamber, to form a heat pipe. 
     Thus it is another object of the invention to provide self-contained heat shielding. 
     The heat shield may include a heat sink communicating between the control electronics and the chamber for transferring heat from the control electronics to the cooling fluid. 
     Thus it is another object of the invention to make additional use of the heat shield as a sink for heat generated by the electronics itself. 
     The foregoing and other objects and advantages of the invention will appear from the following description. In this description, reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration, a preferred embodiment of the invention. Such embodiment and its particular objects and advantages do not define the scope of the invention, however, and reference must be made therefore to the claims for interpreting the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective, fragmentary view of an example engine showing its intake ports and valve cover, the upper surface of which supports heat sensitive electronic components; 
     FIG. 2 is a cross-sectional view along line  2 — 2  of FIG. 1 showing a heat pipe incorporated into the valve cover for providing a heat shield between the heat sensitive electronic components and high temperature engine components; 
     FIG. 3 is an exploded, perspective view of a second example engine having an intake manifold cover incorporating a chamber having inlet and outlet ports for circulation of cooling fluid and for thermally shielding electronics positioned on top of the manifold cover from heat from the engine; 
     FIG. 4 is a cross-sectional view in outline of an example transmission showing a chamber similar to that of FIG. 3 positioned within the transmission sump for receiving cooling fluid to cool electronics contained in that chamber; and 
     FIG. 5 is a cutaway perspective view of the chamber of FIG. 4 showing the chamber double wall for circulating cooling fluid around a center pocket holding the temperature sensitive electronics. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1, an engine  10  may include a block  12  holding therein cylinders and pistons (not shown) according to conventional engine design. 
     The upper surface of the block  12  may be covered by a valve cover  14  having tabs  16  extending outwardly over the intake ports  17  of the block  12  near the top of each cylinder. The tabs  16  include an aperture  22  through which inducted air may be drawn through the intake port  17  after passing through an intake valve of conventional design. In this regard, the tabs  16  fit beneath flanges  18  of intake manifold pipes  20  (only one shown) through which air is inducted according to well-understood techniques. 
     The tabs  16  support for each cylinder a spark coil  24  and injector  26  such as may communicate with the cylinder within the block  12  to provide control of fuel and ignition by conventional techniques. The injector  26  and spark coil  24  receive electrical signals through conductors  28  forming part of a flexible printed circuit substrate  30  attached to an upper surface  32  of the valve cover  14  and the top of the tabs  16 . 
     The printed circuit substrate  30  may be any suitable material as is understood in the art. Further, the invention is not limited to use with a flexible printed circuit substrate  30  and similar wiring may be provided in any number of ways including use of free-standing harnesses or wiring attached directly to the valve cover  14  mechanically or by adhesive or in molded to the valve cover  14  or the like. 
     The tabs  16  provide a continuous structure connecting the valve cover  14  and the injectors  26  and spark coils  24  allowing unbroken support of the printed circuit substrate  30  or permitting conductors to be attached directly to upper surface  32  of the valve cover  14  and the tabs  16 . In the alternative, short harnesses can be used to convey these electrical signals. 
     In the first depicted embodiment, the conductors  28  travel along the tabs  16  to the continuation of the flexible printed circuit substrate  30  on upper surface  32  of the valve cover where conductors  28  communicate with temperature sensitive electronic components  34 . The temperature sensitive electronic components  34  provide engine control through signals communicated over conductors  28  to the spark coil  24  and injector  26  and possibly to or from other engine components located on or off of the flexible printed circuit substrate  30 . Location of the temperature sensitive electronic components  34  in close proximity with the spark coils  24  and injectors  26  simplifies their interconnection. 
     Referring now to FIG. 2, the valve cover  14 , per the prior art, covers the upper valve stems, valve springs and rocker arms. In the present invention, however, the valve cover  14  also provides, beneath its upper surface  32 , a heat shield  36  positioned between the adjacent engine block  12  and the temperature sensitive electronic components  34  in the path of heat  39  passing from the block  12  toward the flexible printed circuit substrate  30 . 
     The heat shield  36 , in a first embodiment, includes a closed cavity  38  holding a volatile liquid with a vaporization point beneath the typical operating temperature of the block  12  such as a water antifreeze combination or a fluorinated hydrocarbon coolant. The cavity  38  has an upward cant toward a finned portion  40  having fin lamina  44  providing increased surface area in contact with the ambient air outside of the valve cover. Metal foams or fin metal inserts can be placed at the upper end of the cavity  38  to further improve heat transmission. The outer surface of the finned portion  40  may be treated with a high emissivity coating to further transmit heat in radiated form away from temperature sensitive electronic components  34 . 
     The upward canting of the cavity  38  provides convective heat transfer from a portion of the heat shield  36  beneath the flexible printed circuit substrate  30  toward the finned portion  40  so that heat may be redirected along path  46  away from the temperature sensitive electronic components  34 . The heat shield  36  thus allows close mounting of the temperature sensitive electronic components  34  to the valve cover  14  without the need for high temperature components or risk of damage to components from engine heat. 
     Some additional cooling of the valve cover  14  is provided by passage of air through manifold pipe  20 . This air cools the manifold pipe  20  and tab  16  of valve cover  14  made integral therewith. By providing suitable conductive material in valve cover  14 , improved heat shielding may be provided. 
     Because the purpose of the heat shield  36  is not to cool the engine block  12  but simply to prevent heat from passing to the temperature sensitive electronics  34 , insulating material  41  may be placed between the heat shield  36  and the engine block  12  to enhance the shielding effect and reduce the size of the cavity  38  and finned portion  40 . 
     By allowing temperature sensitive electronic components  34  to be located near the engine, wiring or conductors to the devices of injector  26  and coil  24  may be made shorter and free runs of wiring harness such as increase engine compartment clutter may be eliminated. 
     Referring now to FIG. 3, a heat shield  36 ′ need not employ a self-contained cooling medium but may make use of one of the coolant streams found in a conventional automobile. 
     In a first embodiment, the engine block  12 ′ may be capped by an intake manifold assembly  50  incorporating standard intake manifold pipes (not shown) carrying inducted air to each cylinder. Positioned above these pipes is a chamber  52 . The chamber  52  is isolated from the intake air but receives low temperature coolant  54  through an inlet pipe  56 . The coolant passes through chamber  52  to absorb heat passing upward from the block  12 ′ and then exits at outlet pipe  58  at an opposite wall of the chamber  52  as heated coolant  60 . Barriers (not shown) may be inserted in the cavity to disrupt flow and cause better distribution of the coolant fluid within the cavity  38 ′. The coolant may be most conveniently radiator fluid but could also be circulated engine oil or transmission oil received from an engine oil cooler or transmission oil cooler or the like, or a dedicated coolant stream including ambient air and intake manifold air. 
     A central air intake  62  connects to the intake manifold pipes passing through the chamber  52  but isolated therefrom. The central air intake  62  provides additional cooling of the chamber  52  through its contained stream of cooled air. Likewise the pipes of the intake manifold block and absorb heat from the engine passing upward to the chamber  52 . 
     On top of chamber  52  opposite the block  12 ′, a flexible circuit substrate  64  may be placed holding temperature sensitive electronic components  34  and having sideward straps  66  communicating with connectors  68  which may connect to fuel injectors  70  and ignition coils  72  positioned on either side of the intake manifold assembly  50 . The side straps  66  may lie within channels  74  in the intake manifold assembly  50 ′ and be covered by a conforming cover  76  which also covers the main body of the flexible circuit substrate  64 . Conforming cover  76  may include thermal insulation. In this way by enclosing the circuit substrate  64 , the temperature of the ambient air does not define the lowest temperature that can be obtained. 
     Alternatively as described above, the temperature sensitive electronic components  34  may be applied directly to the top of the intake manifold assembly  50  by plating its surface with the necessary interconnect wiring or by in-molded or adhesively or mechanically attaching conductors to the intake manifold or by other methods known in the art. In all cases, the cooling is sufficient that conventionally rated electronic components can be used instead of high cost premium, high temperature components and substrates. 
     It is possible in yet another embodiment to place the circuit substrate  64  directly in the chamber  52  when protected by a suitable conformal coating. 
     Although the principal purpose of the chamber  52  is as a heat shield from the higher temperature of the engine block  12 ′, heat sinks  78  may extend downward into the chamber  52  and have an upper surface that may abut a lower surface of flexible circuit substrate  64  beneath heat generating components  80  on the circuit substrate  64 . In this way, heat generated by the components in the enclosed space between conforming cover  76  and the intake manifold assembly  50  may be drawn off by the same cooling fluid that blocks heat transmission from the block  12 ′. 
     Referring now to FIG. 4, the present invention may be used with electronics mounted near other engine components, for example, a transmission  82 . In this case, temperature sensitive circuit components  88  can be held in a transmission sump  84  held beneath a cover  86  at the bottom of the transmission  82 . The temperature sensitive circuit components  88  are protected from heat by heat shielding chamber  90 , which receives cooling fluid  92  through an inlet pipe  94 , which may then be exhausted through an outlet pipe  96  as heated coolant fluid  98 . 
     Referring also to FIG. 5, the temperature sensitive circuit components  88  are shielded from the coolant fluid by a double wall enclosure  100  providing for a central pocket  102  positioned beneath a sealable cover  104  isolated from coolant flow in the outer chamber  90 . Here the coolant fluid may be transmission fluid or the like. Sealable access ports  105  may allow for conductors to be communicated into the temperature sensitive circuit components  88  through an external connector  106 . Sufficient coolant flow through the outer chamber  90  may absorb heat passing through the cover  104  or cool the cover  104  by conduction or the cover  104  may be given a separate heat shield with coolant. The outer surfaces of the enclosure  100  may be thermally insulated (along with the cover  104 ). Further, the cover  104  may be reduced in area to reduce heat transmission therethrough for example by being positioned in a sidewall (as depicted) under the connector  106 . 
     Although it is convenient to use the naturally occurring engine fluid for the coolant process in these latter examples, it will be understood that a specially circulated coolant may also be used having an independent radiator positioned elsewhere in the engine compartment. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.