Abstract:
An ignition switch sensor having a plurality of contacts arranged on a sensor to make intermittent contact with a movable contact and generate a first plurality of outputs corresponding to the position of the movable contact relative to the plurality of contacts. A power mode module receives the first plurality of outputs and compares the outputs to data stored within the memory of the module and provides a second plurality outputs according to the value of the first plurality of outputs. A theft resistor may be integrated into the ignition switch sensor circuitry to facilitate protection from tampering and unauthorized starting of the vehicle&#39;s engine.

Description:
The present invention is related to a method and apparatus for providing an ignition switch status. 
     BACKGROUND OF THE INVENTION 
     Numerous devices have been conceived and/or employed in order to provide a means for facilitating the starting sequence of an automobile. In addition, and unfortunately, there has been a growing need for anti-theft devices to be incorporated into the automobile&#39;s control system. 
     However, and as technological advances have made the operational systems of automobiles more complex, there is also a growing need for simplistic alternatives which allow for enhanced performance while at the same time providing less expensive alternatives. 
     In addition, and as technological improvements are incorporated into electronic devices and more and more devices become reliant upon a single component, the failure of a single component may cause a cascading effect which will disable an entire system. Therefore, redundant pathways are employed to operate systems unaffected by a component failure. However, such redundancies become cost prohibitive. 
     Accordingly, there is a need for an ignition switch sensing device that provides detailed information corresponding to the relative position of a key as it is being relocated within an ignition cylinder. Moreover, there is also a need for device that provides such information with and economical means for providing design redundancies. 
     In addition, there is also a need for the incorporation of an anti-theft mechanism that can be efficiently incorporated into the sensing device. 
     SUMMARY OF THE INVENTION 
     In an exemplary embodiment a power mode module receives a plurality of inputs from a combination of circuits and utilizes a state table in order to determine the position of an ignition switch. 
     In another embodiment, the power mode module also determines what power mode a vehicle is in. 
     In an alternative embodiment, an ignition switch sensor is equipped with an anti-theft resistor that is broken when an unauthorized removal of the ignition switch takes place, and accordingly, the automobile&#39;s engine is prohibited from starting. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
     FIG. 1 is a schematic view of an ignition sensor constructed in accordance with a the present invention; 
     FIG. 2 is a schematic view of an alternative embodiment of the present invention; 
     FIG. 3 is a schematic view of another alternative embodiment of the present invention; 
     FIG. 4 is a schematic view of another alternative embodiment of the present invention; 
     FIGS. 5,  5 A,  5 B,  6 ,  6 A, and  6 B are state tables indicating the power mode and ignition key position; 
     FIG. 7 is a top plan view of an ignition switch contact pattern; 
     FIG. 8 is a top plan view of an alternative ignition switch contact pattern; 
     FIG. 9 is a perspective view of an alternative contact switch pattern; and 
     FIG. 10 is a cross-sectional to along the lines  10 — 10  of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, an illustration of a discrete logic ignition switch sensor  10  and its connection with a power mode module  12  is illustrated. Ignition switch sensor  10  as illustrated in FIG. 1, is configured for a column mounted ignition switch. Discrete logic ignition switch sensor  10  includes a switch contact pattern  14 . Switch contact pattern  14  has a plurality of contacts  16  that are positioned to provide an ignition switch status according to the position of a moving contact  18 . Moving contact  18  and switch contact pattern  14  are configured so that contact  18  will make intermittent contact with contact  16  as the position of contact  18  is altered according to the movement of an ignition switch (not shown). 
     Contacts  16  have a built-in tolerance indicating when contact  18  must make contact for the circuit to be complete. 
     Ignition switch sensor  10  provides three outputs indicated as A, B and C that correspond to the ignition switch position and/or status. Of course, it is contemplated that sensor  10  can be configured to have a lesser or greater amount of outputs. As indicated in FIG. 1, output A provides an off/run/crank status of the ignition switch. Output B relates to an accessory position and output C relates to a run/crank position. 
     Output A, B and C are received as inputs into power mode module  12 . In an exemplary embodiment power mode module  12  is a vehicle mounted electronic body module. 
     In addition, outputs B and C are also received as inputs into a run/crank relay  20  and an engine control module  22  respectively. 
     Accordingly, the positioning of moving contact  18  relative to plurality of contacts  16  completes a circuit wherein information can be relayed to control module  12  and other components of a system into which ignition switch sensor  10  has been installed. 
     The power mode module (PMM) will be responsible for determining and broadcasting the system power mode by processing ignition switch signal states, monitoring the states of timers, and processing other discrete inputs. 
     Ignition system  10  is also equipped with a wakeup delay. When the PMM or any other module sends the bus a wake-up message, the PMM will not send the power mode message until the wake-up delay has expired. If the PMM wakes up the bus, this delay begins when the bus wake-up message is queued. If the PMM is awakened by the bus, this delay begins when the PMM detects the transition from bus-asleep to bus-awake. 
     Three signals (A, B and C) from the ignition sensor (off/run/crank, accessory and run/crank), battery voltage, door status and the engine run flag (ERF) status will be monitored by the PMM in order to determine the present power mode. All signals will be debounced before any demand can determine the actual system power mode. 
     All ignition switch signals (off/run/crank, accessory, and run/crank) will be processed by the PMM for determination of the system power mode and will be directly routed from the ignition switch to the PMM. All ignition switch signals will be consecutively sampled in a specific state for the duration of the ignition signal debounce time before all signals are deemed valid (debounced) by the PMM. Since all of the ignition switch contacts have the same bounce characteristics, all discrete ignition signal inputs to the PMM will be debounced with the same filter times. 
     In an exemplary embodiment, the PMM shall read all ignition signal inputs only when the battery voltage is between 6 volts and 26.5 volts. This will prevent invalid input readings during low voltages encountered during vehicle cranking. Of course, the PMM can be configured to read ignition signal inputs for other battery voltages. 
     In the FIG. 1 embodiment, output A (off/run/crank) ignition switch signal states are based on a ratiometric comparison to the battery voltage measured by the power mode master. 
     Switch contact portion  14  has degrees of rotation which correspond to the rotation of an ignition switch within the ignition cylinder. 
     Referring now to FIG. 2, an alternative of the present invention is illustrated. Here ignition switch sensor  10  is configured to have an anti-theft resistor  24 . A mechanism (not shown) is configured to disconnect and destroy anti-theft resistor  24  if the ignition switch or ignition key cylinder is improperly removed from its location. 
     Accordingly, there is an integration of the anti-theft resistor into the switch mechanization. Therefore, when the theft resistor broken, there is no reading of the theft resistor value and there will be no authorization to start vehicle. 
     For example, if a theft of the vehicle is attempted and the ignition cylinder is removed from the steering column and/or dashboard the anti-theft resistor is broken. For example, if the cylinder is removed through a push or pull process or attempt to remove the cylinder without having a valid ignition key, there is a mechanism that breaks the theft resistor. 
     Since the anti-theft resistor is integrated directly into the switch, this allows for a significant cost savings when compared to prior systems having a separate sensor wherein an antitheft signal is generated. 
     In addition, an additional output D is provided by power mode module  12 . Output D corresponds to a voltage reference for switch state determination. 
     Referring now to FIG. 3, another alternative embodiment is illustrated. Here an ignition switch sensor  10  for an instrument panel mounted ignition switch is illustrated. The component parts of the FIG. 3 embodiment are similar to those illustrated in FIG. 1 however the degrees of rotation are different. Generally, there are lesser degrees of rotation required for an instrument panel mounted ignition switch due to ergonomic reasons. 
     Referring now to FIG. 4, another alternative embodiment is illustrated. Here an ignition switch sensor  10  including an anti-theft resistor  24  is illustrated. The component parts of the FIG. 4 embodiment are similar to those in FIG. 2 however the degrees of rotation are different as discussed immediately above with respect to FIG.  3 . 
     Referring now to FIGS. 5 and 6, the state tables for the output of ignition switch sensor  10  are illustrated. The state tables are included into the memory of power mode module  12 . Of course, other implementations of the logical determination are possible. 
     Accordingly, three or more circuit inputs are being received by the power mode module that looks at a combination of those circuits to determine what position the key is in. 
     One benefit of the instant application is that there is a combination of circuits as opposed to a single circuit determining the key position. The combination of circuits allows for design redundancy wherein if one of the circuits fails the power mode module is still able to determine the key position by looking at the state table. 
     The control module has one or more analog and discrete inputs where it is reading three or four different signals and based upon the voltage levels it sees at these inputs and it determines what the ignition key position is and based upon that determination it will switch in one more relays to power mode the rest of the vehicle. The PMM conducts a ratiometric read on the inputs. 
     The control module also has the potential for sending out a serial data message to indicate what power mode the vehicle is in as well. 
     In addition, the accessory output of sensor  14  is also inputted into a power control module or engine control module  22 . The run/crank output of sensor  14  is also input into a run/crank relay  24 . The engine control module and the run/crank relay allow the engine and/or automobile accessories to be operated in the event of a failure within power mode module  12 . 
     The engine run flag (ERF) indicates that the engine is running in the form of serial data from the powertrain control module to indicate whether it&#39;s running or not. 
     Accordingly, there is high reliability and less complexity than other ignition switch implementations. The entire unit costs less than prior systems because it has fewer contacts and fewer circuits. 
     The entire package is located within the ignition cylinder housing; the key-in switch, theft resistor and ignition circuits are integrated to reduce the number of circuits and package size. This also affects costs and reliability. 
     Accordingly, there is increased reliability due to the fact that there are fewer contacts and circuits, fewer moving parts, and software and hardware redundancies. In addition, use of an ignition switch logic state table reduces the sensor&#39;s sensitivity to contact positioning/tolerances. 
     Referring now to FIG. 7, a possible configuration of contacts  16  and movable contact  18  is illustrated. Here movable contact  18  as a plurality of contact portions  30  which make intermittent contact with contacts  16  as contact  18  is rotated in the direction indicated by arrow  32 . Movable contact  18  can be integral to the sensor or be a component part of an ignition cylinder of an automobile. 
     Referring now to FIG. 8, an alternative embodiment of the FIG. 7 embodiment is illustrated. Here the configuration of movable contact  18  is altered to provide a plurality of contact arms  30  each having a substantially similar size and length to correspond to a plurality of contacts  16  arranged in a circular configuration around movable contact  18 . 
     Referring now to FIGS. 9 and 10, yet another alternative to the FIG. 7 embodiment is illustrated. Here the ignition switch includes an inner cylinder  32 . Inner cylinder  32  is configured, dimensioned and positioned for rotation within an outer cylinder  34 . 
     Inner cylinder  32  has a contact arm  36  secured to the outer surface of inner cylinder  32 . Contact arm  36  is fixedly secured to inner cylinder  32  at one end and movable contact  18  at the other. In addition, contact arm is provided to have a bias generally in the direction of arrow  38 . 
     Switch circuit pattern  14  is positioned along the inner surface of outer cylinder  34 . Accordingly, and as inner cylinder  32  is rotated in the direction of arrow  40 , movable contact  18  will make contact with contact  16 , however, and as illustrated by the dashed lines in FIG. 4, as movable contact reaches the break portion of contacts  16  there is no longer any contact between movable contact  18  and contact  16 , and accordingly, this information is provided to control module  12 . 
     As yet another alternative, movable contact  18  can be replaced or supplemented by a Hall effect sensor or potentiometric sensor. 
     While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.