Abstract:
A circuit and method for correcting signal timing. The circuit and method generate a first signal with a first phase that is out of phase with a periodic object, generate a voltage signal that corresponds to the frequency of the first signal and generate a second signal based on the first signal and the voltage signal, the second signal having a second phase that is substantially in phase with the periodic object.

Description:
PRIOR APPLICATION 
   Applicant claims priority benefits under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 60/693,177 filed Jun. 23, 2005. 

   FIELD OF THE INVENTION 
   This invention relates to ignition timing devices, more particularly to ignition timing devices with timing correction. 
   BACKGROUND OF THE INVENTION 
   Hall Effect sensors are used in many automobile applications. One application is to use a Hall Effect sensor to measure the timing in ignition systems. Other applications use Hall Effect sensors to detect the position of the crankshaft and camshaft and to monitor engine RPM. The signal generated by these sensors are used to ensure that proper engine timing is maintained. 
   In electronic ignition systems, Hall Effect sensors are used to ensure that spark plugs ignite a compressed air-fuel mixture within the engine at an optimum position. To do so at least one ferrous target is mounted or integrated into a rotating engine component, such as the crank shaft. As the target approaches the Hall Effect sensor, containing a magnet, the sensor detects the flux field changes and produces an electric signal. The electric signal in turn is processed and used to trigger an ignition box. The electric signal can be a signal that is either 12 volts or ground and depends on the relative position of the target to the sensor. As the ferrous target approaches a sensor the field flux increases through the sensor. At a critical field flux density the sensor switches from 5 volts, the peak, to ground, the low. The minimum distance position represents the moment when the engine is at peak power, such as optimum compression in a combustion chamber. The passing of the target past the sensor creates a pulse with a width. The pulse has a leading edge that transitions from 5 volts to ground and a trailing edge that transitions from ground to 5 volts. The pulse is modified to a 12 volt high and the ignition box triggers the spark plugs as it detects a 0 to 12 volt edge rise in the pulse. The intention is for the spark plugs to ignite when the engine can produce peak power. 
     FIG. 1  depicts a Hall Effect Pickup incorporated into an engine component  100 . Engine component  100  comprises a rotating shaft  111 , which is coupled to oscillating piston elements (not shown) in the engine. Coupled to shaft  111  is reluctor  112 . Reluctor  112  comprises 8 ferrous blades  113 . The position of the blades  113  on Reluctor  112  corresponds to the compression positions of the piston elements. Engine component  100  also comprises a bell distributor housing  114  that partially encompasses shaft  111 . A Hall Effect sensor  115  is coupled to the inner wall of housing  114 . As the shaft  111  rotates, the blades  113  of reluctor  112  also rotate. As a first blade  113  approaches sensor  115  the sensor  115  detects the increasing flux field strength. The field strength will be at its maximum when the spacing between sensor  115  and blade  113  is at a minimum. At a critical flux field strength, the sensor  115  will trigger and switch from 5 volts to ground. The rotation of blades  113  past sensor  115  decreases the field strength about sensor  115 . The field increases once again as a second blade approaches the sensor  115 . The rotation of blades  113  means that sensor  115  is producing a signal with a period that will correspond to the time between each blade reaching a minimum separation from the sensor  115 . Thus, the frequency of the resulting Hall Effect signal reflects the revolutions per minute of the reluctor  112 , and consequently the engine. At low RPMs, the frequency of the Hall Effect signal will be low, and consequently long periods. At high RPMs, the frequency of the Hall Effect signal will be high, and consequently short periods. 
   In order to have engine peak power the trigger of the Hall Effect signal should occur at the same moment in time as a blade being at a minimum separation from the sensor. However, there is an inherent delay between the position of a blade and the trigger of the Hall Effect signal in time. As a result, the leading edge of a pulse will be off by a time t 1  from the moment when the blade  113  is first in detection proximity to the sensor  115  and off by a time t 3  from the moment when the blade  113  moves away from the detection proximity of sensor  115 . The time t 1  should correspond or be equal to time t 3 . As a result, the triggering edge of the pulse is displaced to a moment that does not correspond to the minimum spacing of the blade  113  to the sensor  115  or the optimum power position of the engine. The time span between the leading edge of the pulse and the moment that the blade moves away from the detection proximity is considered time t 2 . Thus, the phase of the Hall Effect signal will not accurately represent the position of the blade in time. This can be due to the delay in the Hall Effect sensor detecting the position of a rotating blade and the time it takes for the Hall Effect sensor to process a signal. By the time that the triggering edge of the Hall Effect signal reaches a spark plug the engine is no longer in a position of peak power, such as optimum piston compression. This results in a loss of engine efficiency. When an engine operates at low revolutions per minute the period of a Hall Effect signal is relatively long. As a result, the relationship between degree of displacement from peak power and ignition, i.e. the degree in which the signal and piston are out of phase may only be slight. However, when an engine is operating at high revolutions per minute the period of a Hall Effect signal is much shorter. This means that the degree to which peak power and the signal are out of phase is much more pronounced and significant. As a result, there is a greater loss of efficiency at higher RPMs. 
   What is needed is a method and device that achieves maximum precision of engine timing. It would be beneficial if such a method could correct the timing of a Hall Effect sensor. It would also be beneficial if the method could be achieved by a circuit that is coupled to the Hall Effect sensor. 
   SUMMARY OF THE INVENTION 
   This objective is achieved by a method that includes the steps of generating a first signal with a first phase that is out of phase with a periodic object; generating a voltage signal that corresponds to the frequency of the first signal; and generating a second signal based on the first signal and the voltage signal, the second signal having a second phase that is substantially in phase with the periodic object. 
   Another aspect of the method is to supply the first signal and the voltage signal to a timing circuit and to supply the first signal to a frequency to voltage converter. 
   A further aspect of the method is for the frequency to voltage converter to generate the voltage signal in linear relation to the frequency of the first signal and for the timing circuit to generate the second signal based on the voltage signal and the first signal. 
   The objective is also achieved by a circuit comprising a first signal circuit that generates a first signal with a first phase that is out of phase with a periodic object; a voltage signal circuit that produces a voltage signal that corresponds to the frequency of the first signal; and a timing circuit that receives the first signal and the voltage signal and produces a second signal with a second phase that is substantially in phase with the periodic object. 
   The first signal circuit can include a sensor such as a Hall Effect sensor that is positioned to detect the motion of the periodic object and generates a Hall Effect signal. The voltage signal circuit can include a frequency to voltage converter that produces a voltage level that is linearly related to the frequency of the first signal. 
   The circuit can be incorporated in a system that includes a periodic object such as a rotating shaft or at least one oscillating piston. The second signal can be supplied to an ignition box through a buffer circuit at the moment when an engine is in a state of optimum power. 
   Other objects of the invention and its particular features and advantages will become more apparent from consideration of the following drawings and accompanying detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a depiction of a Hall Effect sensor incorporated into an engine system. 
       FIG. 2  is a flow diagram of the processing of a signal from a Hall Effect sensor with correction of the signal. 
       FIG. 3  is a depiction of a circuit that corrects a signal from a Hall Effect Sensor. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2  is a depiction of an arrangement  200  of elements and steps for correcting the signal timing produced by a sensor. A voltage regulator circuit  210  generates a regulated voltage from a battery supply to circuits  220 ,  230 ,  250 , and  270 . Hall Effect circuit  220  produces a Hall Effect signal that is supplied to a voltage signal circuit  250 . The voltage signal circuit  250  converts the Hall Effect signal to a constant voltage signal level that depends upon the frequency of the Hall Effect signal. If the frequency were to change, the voltage level produced would be altered accordingly. This voltage signal level and the Hall Effect signal are supplied to a timing circuit  230 . The timing circuit  230  applies the voltage signal from circuit  250  to the Hall Effect signal. This alters the period or phase of the Hall Effect signal such that a corrected signal is produced by timing circuit  230 . The corrected signal is supplied to buffer circuit  270  which inverts the corrected signal and transfers the corrected signal to an ignition box  290 . 
     FIG. 3  depicts a circuit  300  that incorporates the elements and sequence of steps identified in  FIG. 2 . A list of parts for circuit  300  are as follows: 
   
     
       
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
               311 
               D4 (1N4002) 
             
             
                 
               312 
               R2 (10 OHM ¼ WATT) 
             
             
                 
               313 
               CI (33 UFD @ 35 WVDC) 
             
             
                 
               314 
               C2 (.01 UFD) 
             
             
                 
               315 
               U1 (78L05A) (VOLTAGE REGULTAOR) 
             
             
                 
               321 
               C3 (1 UFD) 
             
             
                 
               322 
               U5 (ATS672LSB-LN) (HALL EFFECT SENSOR) 
             
             
                 
               323 
               C13 (.01 UFD) 
             
             
                 
               324 
               R1 (560 OHM) 
             
             
                 
               331 
               R5(IK OHM) 
             
             
                 
               332 
               R13 (1K OHM) 
             
             
                 
               333 
               R4 (100K OHM) 
             
             
                 
               334 
               C4 (.47 UFD) 
             
             
                 
               335A 
               U5 (COMPARITOR-LMV33I) 
             
             
                 
               335B 
               U5 (COMPARITOR-LMV33I) 
             
             
                 
               336 
               C5 (.022 UFD) 
             
             
                 
               337 
               R8 (22K OHM) 
             
             
                 
               338 
               R7 (1.5K OHM) 
             
             
                 
               339 
               R6 (10K OHM) 
             
             
                 
               340 
               R3 (10K OHM) 
             
             
                 
               341 
               R22 (6.8K OHM) 
             
             
                 
               342 
               DI (1N4448 DIODE) 
             
             
                 
               343 
               R9 (10K OHM) 
             
             
                 
               344 
               D3 (1N4448 DIODE) 
             
             
                 
               345A 
               U3 (14001, CMOS OR GATE) 
             
             
                 
               345B 
               U3 (14001, CMOS OR GATE) 
             
             
                 
               351 
               C1 (1 UFD) 
             
             
                 
               352 
               R5 (10K OHM) 
             
             
                 
               353 
               R11 (470 OHM) 
             
             
                 
               354 
               C9 (22 UFD) 
             
             
                 
               355 
               U2 (LM2917) 
             
             
                 
               356 
               C8 (.01 UFD) 
             
             
                 
               357 
               C7 (1 UFD) 
             
             
                 
               358 
               R21 (36K OHM) 
             
             
                 
               359 
               R14 (1K OHM) 
             
             
                 
               360 
               R18 (10K OHM) 
             
             
                 
               361 
               R17 (100K OHM) 
             
             
                 
               362 
               R16 (33K OHM) 
             
             
                 
               363 
               U4 (OPAMP OPA364A) 
             
             
                 
               371 
               D2 (1N4448 DIODE) 
             
             
                 
               372 
               C6 (150 PF) 
             
             
                 
               373 
               R10 (10 MEG OHM) 
             
             
                 
               374A 
               U3 (14001, CMOS OR GATE) 
             
             
                 
               374B 
               U3 (14001, CMOS OR GATE) 
             
             
                 
               375 
               C10 (.01 UFD) 
             
             
                 
               376 
               R12 (100K OHM) 
             
             
                 
               377 
               R20 (5.6K OHM) 
             
             
                 
               378 
               R19 (560 OHM) 
             
             
                 
               379 
               Q1 (NSB7002A FET) 
             
             
                 
               380 
               C13 (.01 UFD) 
             
             
                 
               381 
               Q2 (NSB7002A FET) 
             
             
                 
                 
             
           
        
       
     
   
   The circuit  300  incorporates a voltage regulator circuit  310 , a Hall Effect circuit  320 , a timing circuit  330 , a voltage signal circuit  350 , and a buffer circuit  370 . The dashed lines in  FIG. 3  indicate the different regions of circuit  300  that correspond to circuits  310 ,  320 ,  330 ,  350  and  370 . The voltage regulator circuit  310  regulates the voltage from a battery  311  to 5 volts. This ensures that any voltage fluctuation from battery  311  does not effect the correction of the signal from Hall Effect sensor  322 . The voltage regulator circuit  310  supplies a voltage to circuits  320 ,  330 ,  350 , and  370 . 
   Hall Effect circuit  320  comprises a Hall Effect sensor  322 , such as an Allegro ATS672LSB-LN Hall effect sensor. The Hall Effect sensor  322  produces a signal that represents the rotation of reluctor  112  and the relative position of blades  113  to sensor  322 . The signal comprises a low, or trough, that represents the blade in close proximity to the sensor  322  and a high, or peak, that represents the blade at a position away from the sensor  322 . Due to the delay in detection and processing by sensor  322  the leading edge of a pulse will be off by a time t 1  from the moment when the blade  113  is first in detection proximity to the sensor  115  and off by a time t 3  from the moment when the blade  113  moves away from the detection proximity of sensor  115 . The time t 1  should be equal to time t 3 . The time span between the leading edge of the pulse and the moment that the blade moves away from the detection proximity is considered time t 2 . The signal generated from Hall Effect circuit  320  is fed into timing circuit  330  and voltage signal circuit  350 . 
   Voltage signal circuit  350  comprises a frequency to voltage converter  355 . Converter  355  converts the signal from Hall Effect circuit  320  to a single converted voltage. The level of this converted voltage depends on the frequency of the voltage signal. Converter  355  incorporates a linear relationship in this conversion. As a result, a higher frequency Hall Effect signal results in a higher converted voltage produced by converter  355 . A low frequency Hall Effect signal results in a low converted voltage produced by converter  355 . The voltage from converter  355  is then supplied to timing circuit  330 . 
   Timing circuit  330  comprises a comparator circuit and a logic circuit. The comparator circuit comprises a first  335 A and second  335   b  comparators. The logic circuit comprises a first  345 A and second  345 B logic gates. The signals from the Hall Effect circuit  320  and the voltage signal circuit  350  are fed into the first  335 A and second  335 B comparators. The comparators  335 A and  335 B apply the voltage signal generated by circuit  350  to the Hall Effect signal generated by Hall Effect circuit  320 . The comparators  335 A and  335 B output a partially corrected signal that has undergone a phase period shift. The degree of the phase/period shift depends upon the frequency of the Hall Effect signal and the voltage supplied by the voltage signal circuit  350 . This partially corrected signal is fed into logic gates  345 A and  345 B. The logic gates  345 A and  345 B further shift the phase/period of the partially corrected signal to generate a corrected signal. The phase/period shift of the corrected signal is characterized by a pulse width that is increased. The corrected signal can also be characterized by a pulse with a leading edge that is aligned in time with the location of the position of blade  113 , i.e. the position of the optimum power state of the engine such as the compression position of a piston. 
   The corrected signal from timing circuit  330  is fed into buffer circuit  370 . Buffer circuit  370  comprises logic gates  74 A and  74 B. Buffer circuit  370  inverts the pulse of the corrected signal from a low, or trough, to a high, or peak. As a result, a leading edge of the pulse is formed from ground to 5 volts and a trailing edge of the pulse is formed from 5 volts to ground. Buffer circuit  370  intern supplies the inverted corrected signal to an ignition box to trigger the spark plugs. Thus, the leading edge of the corrected pulse, which is aligned with the optimum power state of the engine, will trigger the ignition box. The result of this processing of the Hall Effect signal into a corrected signal and intern to invert that signal, is to produce a signal that is in phase with the phase of the optimum power state of the engine, such as the phase of the pistons. 
   The operation of circuit  300  will now be discussed by way of example. Hall Effect Sensor  322  is mounted in a position so as to detect the relative position of blades mounted on a rotating shaft. The position of these blades correspond to the optimum power state of an engine, such as the compression position of oscillating piston elements. A first blade approaches Hall Effect sensor  322 , comes within a minimum distance of Hall Effect sensor  322 , and moves beyond Hall Effect sensor  322 , generating a Hall Effect signal. The Hall Effect signal has a first low or trough that corresponds with the minimum distance between the first blade and the sensor  322 . The first low is out of phase with the position of the first blade by a time amount t. The signal also has a high or peak that corresponds to the moment when the sensor  322  moves away from the triggering position of the sensor  322 . The resulting signal is a pulse with a leading edge and a trailing edge. As the second blade approaches the sensor  322 , this forms a second low. The Hall Effect signal is fed into a voltage signal circuit  350 . The voltage signal circuit creates a voltage signal at a single (or constant) voltage level that linearly corresponds to the frequency of the Hall Effect signal. The Hall Effect signal and the voltage signal are fed into timing circuit  330 . The timing circuit  330  uses the voltage signal to delay the Hall Effect signal, or shift the phase/period of the Hall Effect signal. Thus, the degree of phase/period shift of the Hall Effect signal is in proportion to the frequency of the Hall Effect signal. The timing circuit  330  outputs a corrected signal that has undergone a phase/period shift. As a result, the corrected signal has a phase that is either in phase or out of phase by a time less than t with the position of the blades on the rotating shaft. Thus, the corrected signal is substantially in phase with the rotation of the blades and consequently the optimum power state of the engine. The timing circuit feeds this corrected signal to a buffer circuit  370 . Buffer circuit  370  inverts the corrected signal such that the leading edge of the inverted signal will trigger the ignition box when the engine is in an optimum power state. Buffer circuit  370  applies the corrected signal to the ignition box. Due to circuit  300  the signal applied to the ignition box is now in phase with the optimum power state of the engine. This improves the efficiency of the engine at higher RPM levels. 
   It should be noted that, while various functions and methods have been described and presented in a sequence of steps, the sequence has been provided merely as an illustration of one advantageous embodiment, and that it is not necessary to perform these functions in the specific order illustrated. It is further contemplated that any of these steps may be moved and/or combined relative to any of the other steps. In addition, it is still further contemplated that it may be advantageous, depending upon the application, to utilize all or any portion of the functions described herein. 
   Further, although the invention has been described with reference to a particular arrangement of parts, features and the like, these are not intended to exhaust all possible arrangements or features, and indeed many other modifications and variations will be ascertainable to those of skill in the art.