Patent Application
20070199751
1. Technical Field
The present invention relates generally to louvers used to control engine compartment ventilation for cooling of the compartment on a motor vehicle.
2. Description of the Problem
Elevated engine compartment air temperatures on motor vehicles have been a design issue essentially since the introduction of internal combustion engines to motor vehicles. The problem has not abated, but become worse, in recent years. This stems in part from the increasing use of exhaust gas recirculation and catalytic converters to reduce exhaust emissions. It also results from the addition of vehicle accessories such as air conditioning. Higher underhood air temperature drives component material selection, cooling system capacity and other design considerations, all of which can add to expense and vehicle complexity. Currently, the problem is solved by the addition of cooling system capacity and heavy reliance on active monitoring. Adding cooling capacity requires more space under the hood. Louver systems have also long been used to control air flow through the engine compartment to aid cooling. Increased fan speed has been used to increase air flow through the engine compartment and under the cab. Heat shields have been used to protect temperature sensitive areas.
It would be advantageous to simplify engine compartment cooling by limiting the need for human or control system intervention while, at the same time, taking advantage of monitoring of operation of a passive cooling system.
The invention provides a plurality of fins or louvers that are located strategically through a vehicle body, including the hood, adjacent the vehicle's engine compartment. As the temperatures under the hood locally approach critical temperatures that could damage adjacent systems and sub-systems, the fins open promoting air circulation through the engine compartment adjacent the critical area thereby releasing heated air into the atmosphere. Control of the fins' position is local and relatively passive.
Fin position is controlled through control of magnetic attraction between the fin and the hood or body. Fin and hood are each equipped with magnets with their poles oriented to draw the fin toward the hood. Magnetic closure occurs when a catch made of material with good magnetic susceptibility, but a low Curie point, is cool enough to transmit magnetic flux between the permanent magnets. The magnetic catch is located between permanent magnets affixed to the hood and the fin. As local engine compartment temperature rises and the magnetic catch loses magnetic susceptibility a spring urges the fin to an open position. The spring is preferably internal to the fin or an integral part of the fin. The fin may rotate on a pivot though this is not the preferred arrangement. The fin is inherently limited in travel, or subject to an external travel limiting structure, allowing the magnetic attraction to close the fin once the catch regains magnetic susceptibility. The fin spring may be a bimetallic structure which urges the fin open with increasing force as local temperature climbs and can be designed to retract the fin to a closed position at low temperatures.
Advantageously, little or no active control intervention is required to implement this system. In one embodiment the system appears completely passive to the vehicle's control systems. This does not prevent monitoring of the louvers/fins by the control system, which may be done to trigger active cooling system response to louver movement or to signal faults. Active cooling system components that can be integrated into the system are; fan speeds, logic for activating the fan to exhaust the air and engine controller activity that would provide indications of an upcoming engine event that would generate increased heat. Where louver movement appears abnormal in view of measured engine temperature, an indication may be provided an operator.
Additional effects, features and advantages will be apparent in the written description that follows.
The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:
FIGS. 5A-B illustrate the louver of the present invention.
Referring to the drawings and in particular referring to
FIGS. 5A-B illustrate construction of a preferred embodiment of a fin 502 for a louver system in which the fin flexes into and out of closed and open positions as indicated by double arrow A. Alternatively, fin 502 could be mounted on a pivot. Fin 502 is mounted in a hood or body section 500 as an aerodynamic shell around an engine compartment 410. Fin 502 is affixed to hood 500 along one edge, illustrated as a section 512 which bends under hood 500. The opposite edge 505 of fin 502 is beveled to make sealing contact with a inwardly turned border 504 of hood 500 adjacent vent hole 516. Set in or affixed to inwardly turned border 504 is a permanent magnet 506. Set in beveled edge 505 of fin 502 opposite magnet 506 is a second magnet 508 oriented so that magnets 506 and 508 present opposite poles to one another for attraction. Intermediate to magnets 506 and 508 is a magnetic catch 510, which a made of a material exhibiting high magnetic susceptibility at normal atmospheric temperatures but which has a relatively low Curie point selected so that the magnetic catch 510 loses susceptibility at the desired temperature. The material of the catch 510 is selected or blended to exhibit a Curie point which corresponds to a level at which local cooling of engine compartment 410 is required. With loss of susceptibility magnetic flux is not transmitted through catch 506 with an accompanying loss of attractive force between the two permanent magnets 506, 508.
Fin 502 is flexible and incorporates springs 514 which urge the fin to curl open in the outward direction of arrow A. Springs 514 may be bimetallic so that the force urging the fin 502 open increases with increasing temperature. When temperature catch 510 regains its high susceptibility, the fin 502 is pulled closed by magnetic attraction. Where springs 514 are bimetallic, they may be designed to contribute to this operation.
Referring to
If one or more vents is determined to be open at step 704, the YES branch is followed to step 712 for a look up operation to determine which vent locations have opened. This information is used to determine if operating conditions are such that it would be expected that the vent be open. This may be done from simply looking at engine temperature, or additional factors may be considered.
Steps 714 through 720 are optional. In order, they provide for reading vehicle speed (step 714), reading fuel flow (step 716, possibly as an indication of engine loading or power output as an indicator of soon to increase temperature), reading ambient temperature (718) and determining if particular accessories are running (step 720). Finally engine temperature is read (step 721). The operating variables available may then be used as arguments for a look up table to generate an expected operating temperature in the vicinity of the vent which is open (step 722). For example, there may be different expectations relating to local temperature adjacent an air conditioning compressor depending on any or all of the variables considered, and thus it may be possible to predict temperature in that area. If the vent is opened in area when it is not expected to be it may be an indication that a particular component is running hotter than expected. Such comparisons of expected state with actual state are made at step 724. If the expected state is met processing returns to step 702 along the YES branch. If not, step 726 is executed along the NO branch to alert the operator before program execution loops back to step 702.
The invention provides a louver system for engine compartment cooling requiring little or no control intervention to implement. Where louver movement appears abnormal in view of engine temperature sensors an indication may be provided an operator.
While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.
