Abstract:
A brake pedal position circuit includes a brake pedal mechanism having a ferromagnetic portion, which is movably mounted in a motor vehicle. At least one permanent magnet for generating a magnetic field is provided, as well as at least one Hall effect device for generating output data states that are dictated by variations in the magnetic field. A housing for the permanent magnet and the Hall effect device is fixedly secured in the vehicle so as to provide a portion in proximate relation to the brake pedal ferromagnetic portion when the brake pedal is in an “at rest” position. Movement of the brake pedal mechanism in the vehicle changes the magnetic field and causes a resulting change in the Hall effect device data state.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to an electronic switch, and deals more particularly with a brake pedal sensor and electronic switch that operates to accurately detect the presence of a brake pedal in a motorized vehicle without the need for mechanical contacts, and which is capable of performing high current and low signal switching of auxiliary components. 
     BACKGROUND OF THE INVENTION 
     In many diverse fields reliable switches are integral to the operation of the apparatus or device in which they are utilized. These switches are typically overlooked by most causal observers, but one so skilled in the art will recognize that these devices perform operations which are absolutely vital to the applications in which they are employed. Common to each of these many applications is the need to incorporate switches having high reliability and repeatability, qualities which are of no small consequence given the repeated use of these actuators which may number in the millions of cycles during the lifetime of the switches. 
     One such example of an electronic switch is as an incorporated element of an electronic circuit. In such applications where physical, non-electronic communication is utilized as the impetus for altering the data state of the switch, mechanical contacts are employed to detect and transmit such communication. As will be appreciated, the repeated contact between these elements in conjunction with environmental effects and manufacturing concerns results in wear and corruption of the contacting portions of the switch. 
     In particular, many motorized vehicles typically utilize brake pedals for initiating a braking action of the vehicle while simultaneously illuminating the brake lights. In such configurations, the movement of the brake pedal is determined by known mechanical contacts, which suffer from the debilitating effects of wear and corrosion, as discussed previously. As will be appreciated in applications involving motorized vehicles, degradation of these mechanical switching elements can be potentially life threatening, therefore increasing the need for a more reliable and repeatable switching apparatus. 
     In addition to mechanical wear, existing brake pedal configurations present other safety concerns, namely, the actuation of the braking system of a motorized vehicle during those times when the engine of the vehicle is not operating. Many large-scale vehicles, such as construction vehicles, utilize pneumatic or hydraulic braking systems, which must be pressurized during engine operation in order to function. Known brake pedal configurations, therefore, suffer from an inability to adequately respond to a braking command when the engine is not running. 
     It is therefore an object of the present invention to construct an electronic switch, which does not require mechanical contacts to generate a plurality of data states. 
     It is another object of the present invention to utilize a magnetic field of a permanent magnet in the performance of a switching operation. 
     It is another object of the present invention to construct a brake pedal sensor, which is largely impervious to the debilitating effects of structural wear and adverse environmental conditions. 
     It is another object of the present invention to increase the reliability and repeatability of a brake pedal sensor. 
     It is another object of the present invention to integrate a brake pedal sensor in the circuitry of a motorized vehicle to enable the switching of high current auxiliary devices. 
     It is another object of the present invention to integrate a brake pedal sensor in the circuitry of a motorized vehicle so as to enable operation of a pneumatic or hydraulic braking system even during those times that the engine is not running. 
     With the forgoing problems and concerns in mind, the present invention therefore seeks to eliminate the need for mechanical contact between elements of a brake pedal sensor, as well as enabling operation of a pneumatic or hydraulic braking system even when an engine of the motorized vehicle is not running. 
     SUMMARY OF THE INVENTION 
     According to one embodiment of the present invention, a Hall effect transistor and permanent magnet assembly is utilized to detect the position of a ferromagnetic portion of a brake pedal mechanism in a motorized vehicle. When movement of the brake pedal mechanism is so detected, the brake lights of the vehicle are then activated without the need for mechanical contacts between electrical switching elements. The present invention therefore avoids the wear and environmental corruption, which typically affects these mechanical systems. By utilizing a permanent magnetic in fixed relation to the Hall effect transistor, the present invention substantially eliminates spontaneous activation of the braking system of the vehicle due to unintended fluctuations in the magnetic field incident upon the Hall effect transistor. Moreover, the use of MOSFET technology in conjunction with the Hall effect transistor advantageously allows for the switching of high current electrical components. The present invention also provides an additional measure of safety for those vehicles utilizing pressurized hydraulic or pneumatic braking systems by ensuring that these systems become operative even when the engine of the vehicle is off. 
     These and other objectives of the present invention, and preferred embodiments thereof, shall become clear by consideration of the specification, claims and drawings taken as a whole. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of an electronic switch, depicting a brake pedal position circuit for a motorized vehicle, according to one embodiment of the present invention. 
     FIG. 2 is a perspective view of a sensor housing for the brake pedal position circuit depicted in FIG.  1 . 
     FIG. 3 is a schematic view of the brake pedal position sensor housing in operative relationship with a brake pedal of a motorized vehicle. 
     FIG. 4 is a schematic view of the interior of the brake pedal position sensor housing. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As depicted in FIG. 1, a brake pedal position circuit  200  is arranged to detect the movement of a brake pedal in a motorized vehicle and to switch the brake lights and engine control signal of the vehicle either on or off in response to this movement. 
     The brake pedal position circuit  200  of FIG. 1 is formed on an unillustrated circuit board, or the like, and utilizes at least one Hall effect transistor  215  incorporated into an integrated magnetic sensor assembly  210 . The Hall effect transistor  215  essentially functions as a switching device, alternatively outputting a digital ‘high’ or a digital ‘low’ signal in dependence upon a change in magnetic flux experienced by the Hall effect transistor  215 , to be described in more detail below. A power supply circuit  220  is provided to generate a dc-voltage to energize the chip  210  from the vehicle&#39;s power supply  225 . Known resistor-capacitor (RC) configurations are utilized in the power supply circuit  220  to eliminate any electromagnetic interference before presentation of the energizing voltage to the chip  210 . 
     Returning to FIG. 1, an enabling circuit  230  utilizes a pair of MOSFETs  235  as switching elements to be connected in parallel to each other. The MOSFETs  235  are configured to enter a conducting mode in response to a digital ‘low’ signal being applied thereto. When placed in the conducting mode, the MOSFETs  235  will pass an enabling current from the power supply of the vehicle  225  to a load circuit  240 . The load circuit  240  is also provided with an auxiliary load receptacle  250  for electrically enabling trailer lights of the vehicle, or the like. The load receptacle  250  is protected through the use of a poly-switch fuse  255  having a predetermined current rating, preferably on the order of approximately 1 amp. 
     One important aspect of the present invention, therefore, is that the enabling circuit  230  utilizes the MOSFETs  235  as enabling transistors due to their ability to handle high switching currents. This use becomes especially important when the primary load  245  takes the form of the brake lights of the vehicle, typically drawing on the order of approximately 14 amps. 
     In operation, the brake pedal position circuit  200  is mounted within a sensor housing  300  (to be described in more detail later) and includes a permanent magnet  280  or an equivalent, such as an electromagnet, fixedly positioned in close proximity to the Hall effect transistor  215  of the chip  210 . The sensor housing  300  is then positioned adjacent a ferromagnetic portion of the brake pedal mechanism such that movement of the brake pedal will cause a change in the magnetic flux acting on the chip  210 , thereby triggering a change in the data state outputted by the Hall effect transistor integrated therein. The sensor housing  300  is preferably mounted adjacent a movable ferromagnetic brake shaft  302  (FIG. 3) extending from a brake pedal  304  (FIG. 3) into the interior housing of the vehicle, but may be alternatively mounted in close proximity to any ferromagnetic portion of the brake pedal mechanism, including adjacent the ferromagnetic brake pedal  304  itself. 
     In the preferred embodiment of the present invention, a ferromagnetic portion of the brake pedal mechanism will be oriented adjacent the chip  210  in its rest position, during which time the Hall effect transistor  215  will be non-conductive and outputting a digital ‘high’ signal to the MOSFETs  235 . The enabling circuit  230  will therefore be isolated and prevented from energizing the primary load  245 . As utilized hereinafter, the term ‘rest position’ refers to the position of the brake pedal mechanism prior to depression of the brake pedal by an operator of the vehicle during a braking operation. 
     As an operator of the vehicle presses on the brake pedal  304 , the ferromagnetic portion of the brake pedal mechanism is distanced from the chip  210  and the permanent magnet  280 . In response to this movement of the brake pedal  304  and the associated flux in the magnetic field experienced by the chip  210 , the Hall effect transistor  215  will trigger, or change its data state, from outputting a digital ‘high’ to a digital ‘low’ signal to the MOSFETs  235 . The enabling circuit  230  will subsequently become energized, thereby allowing the MOSFETs  235  to conduct and pass the enabling current to the primary and auxiliary loads,  245  and  250  respectively. Return of the brake pedal  304  to its rest position will cause the ferromagnetic portion of the brake pedal mechanism to come to rest adjacent the chip  210 , again causing the Hall effect transistor  215  to enter a non-conductive, ‘high’ output, state and cutting off the enabling current to the primary and auxiliary loads,  245  and  250  respectively. 
     In this manner, the electronic switch depicted in FIG. 1 accomplishes the intermittent actuation of the brake lights of a motorized vehicle without the need for mechanical contacts. Moreover, another inventive aspect of the present invention resides in the utilization of the Hall effect transistor  215  to trigger the MOSFETs  235 , thereby enabling the switching of vehicle loads drawing large currents. 
     As an additional feature of the present invention, the brake pedal position circuit  200  of FIG. 1 also provides an added measure of safety for those vehicles utilizing hydraulic or pneumatic braking systems, such as tractor trailers, construction vehicles or the like, by ensuring that the braking system will engage even when the engine of the vehicle is not operating. An engine control circuit  260  is employed for this purpose and is integrated into the operational circuitry depicted in FIG.  1 . 
     Typically, an engine-driven pump device  280  is utilized to pressurize the brake system of vehicles equipped with either hydraulic or pneumatic brakes. When the engine  282  of a vehicle is not operating, however, the hydraulic or pneumatic brakes are not pressurized by the pump device and therefore the brake system of such a vehicle does not engage when an operator presses upon the brake pedal. As configured in FIG. 1, an engine control switching transistor  265  of the engine control current  260  becomes conductive in opposition to the conditions which cause the MOSFETs  235  to conduct; that is, in response to the ferromagnetic portion of the brake pedal mechanism being oriented adjacent to the chip  210 . When conductive, the engine control switching transistor  265  passes the operational current to an engine control unit  267  of the vehicle, thereby deactivating the pump device  280  of the vehicle. 
     In contrast, when the ferromagnetic portion of the brake pedal mechanism is shifted from its rest position, away from the chip  210 , the Hall effect transistor  215  outputs a digital ‘low’ signal and places the engine control switching transistor  265  into a non-conductive state. The operational current to the engine control unit  267  is then interrupted, signaling to the engine control unit  267  to activate the pump device  280  of the vehicle. In this manner, the pump device  280  becomes active even when the engine  282  of the vehicle is not running. Moreover, as discussed previously, the ‘low’ signal outputted by the Hall effect transistor  215  simultaneously energizes the primary and auxiliary loads of the vehicle,  245  and  250  respectively, thereby causing illumination of the vehicle&#39;s brake lights or the like. 
     It will be readily appreciated that the switching transistor  265  indirectly energizes the pump device by enabling the engine control unit  267  to sense the depression of the brake pedal  304  and subsequently pressurize the brake system accordingly. While a switching transistor  265  has been depicted in FIG. 1, the present invention is not limited in this regard as alternative switching elements may be employed, provided they are capable of selectively completing the conductive path between a power supply terminal  270  and a return terminal  275  of the engine control unit in response to a digital ‘high’ signal, without departing from the broader aspects of the present invention. 
     It should also be appreciated that while the specific architecture for the brake pedal position circuit  200  of FIG. 1 has been described, the present invention is not limited in this regard as alternative circuit elements and configurations may be employed as well, without departing from the broader aspects of the present invention. 
     As shown in FIGS. 2 and 4, the chip  210  and the permanent magnet  280  are removably housed within a sensor housing  300 . A non-magnetic, non-conductive fiber pad  315  may be mounted on the front outer face of the sensor housing  300  for contact with the ferromagnetic portion of the brake pedal mechanism, thereby providing a visual and tactile indication that the sensor housing  300  is positioned the correct distance from the brake pedal mechanism; that is, the fiber pad  315  has a predetermined thickness indicative of the mounting distance between the sensor housing  300  and the ferromagnetic portion of the brake pedal mechanism. As further depicted in FIG. 2, a grouping of contact wires  317  may be bound together to extend from the sensor housing  300  for connection with the electrical system of the vehicle via a coupling  319 . 
     As shown in FIG. 3, a brake pedal mechanism  320  may be comprised of a ferromagnetic shaft  302  and brake pedal  304 , and is adapted for movement adjacent the sensor housing  300  in response to its depression by a driver of a motorized vehicle. Numerals  302 ′ and  304 ′ illustrate the ferromagnetic shaft and brake pedal portions, respectively, when they are displaced from the rest position during operation. In this manner, fluctuations in the magnetic field incident upon the chip  210  due to the movement of either the ferromagnetic shaft  302  or the brake pedal  304  of the brake pedal mechanism  320  are accurately detected by the Hall effect transistor  215 . It will be readily appreciated that the specific thickness of the fiber pad  315  varies in dependence upon the strength of the magnetic field generated by the permanent magnet  280 , the particular ferromagnetic composition of the brake pedal mechanism  320 , and the like. 
     The present invention also contemplates that the sensor housing  300  may be of any size or shape, wherein the preferred arrangement provides that, when employed for detection, the chip  210  is positioned between the permanent magnet  280  and a ferromagnetic portion of the brake pedal mechanism  320 , as schematically illustrated in FIG.  4 . It will be readily appreciated that the sensor housing  300  also preferably secures the constituent elements of the power supply circuit  220 , the enabling circuit  230  and the engine control circuit  260 . Thus, movement of the ferromagnetic portion of the brake pedal mechanism  320  serves to induce a fluctuation in the magnetic field of the permanent magnet  280  to thereby cause the Hall effect transistor  215  to change its outputted data state. 
     Tabs  322  are depicted in FIGS. 2 and 3 and are utilized to fixedly secure the sensor housing  300  to the body of the vehicle. As shown in FIG. 3, the sensor housing  300  may be fixed to the vehicle&#39;s body through the assistance of a bracket  324 , or the like. It will be readily appreciated that the location and number of tabs  322  may be modified without departing from the broader aspects of the present invention. 
     It will also be readily appreciated that the interior of the sensor housing  300  may be sealed against environmental contaminants including dust, water and extreme temperatures ranging between −40° C. to 85° C. Protection of the brake pedal position circuit  200  may also be ensured by encapsulating the circuit board of the brake pedal position circuit  200  with a potting compound, or the like. 
     One important aspect, therefore, of the present invention is the fixed relationship between the Hall effect transistor  210  and the permanent magnet  280  within the sensor housing  300 . By so fixing the relationship between the permanent magnet  280  and the Hall effect transistor  210 , the magnetic field experienced by the Hall effect transistor  210  may be kept substantially constant, thereby reducing the potential for unintended activation of the braking system by the brake pedal position circuit  200 . 
     Another important aspect of the present invention is the heretofore unknown configuration of a brake pedal sensor and electronic switch, which eliminates the need for mechanical contact between switching elements. The resultant switch is therefore more reliable and provides a greater repeatability of operation due to the elimination of physical wear upon constituent switching elements. Moreover, the secondary advantageous effects of employing a brake pedal sensor and electronic switch of the present invention include a reduction in maintenance and repair costs, both in parts and labor, as well as a reduction in warranty costs for manufacturers. 
     With reference to FIGS. 1-4 and the foregoing discussions of the same, the present invention contemplates utilizing a Hall effect transistor to detect the position of a ferromagnetic portion of a brake pedal mechanism in a motorized vehicle. When movement of the brake pedal mechanism is so detected, the brake lights of the vehicle are then activated without the need for mechanical contacts between electrical switching elements. The present invention therefore avoids the wear and environmental corruption, which typically affects these mechanical systems. By utilizing a permanent magnetic in fixed relation to the Hall effect transistor, the present invention substantially eliminates spontaneous activation of the braking system of the vehicle due to unintended fluctuations in the magnetic field incident upon the Hall effect transistor. Moreover, the use of MOSFET technology in conjunction with the Hall effect transistor advantageously allows for the switching of high current electrical components. The present invention also provides an additional measure of safety for those vehicles utilizing pressurized hydraulic or pneumatic braking systems by ensuring that these systems become operative even when the engine of the vehicle is off. 
     While the invention described above includes a Hall effect device, other forms of sensors can be adopted for use in the circuit of the present invention. For example, a capacitance sensor, an optical sensor, or other magnetic field sensors known to those so skilled in the art. 
     While the invention had been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various obvious changes may be made, and equivalents may be substituted for elements thereof, without departing from the essential scope of the present invention. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention includes all embodiments falling within the scope of the appended claims.