Abstract:
An actuator and integral position sensor has increased reliability with a fail-safe mode. The actuator and sensor assembly includes a rotary actuator that has a driving shaft. A sensor rotor has the driving shaft mounted in a bore. A contactor is mounted to an outer edge of the rotor. The contactor is engaged with a resistor film as the rotor rotates. A driven shaft is mounted to the rotor in another bore. The rotor couples the driving shaft and the driven shaft together.

Description:
BACKGROUND 
   The present invention relates to actuators in general and in particular to a rotary actuator with an integral position sensor. 
   Prior actuators combined with position sensors have sensed the position of the actuator and not the device that is to be moved by the actuator. Unfortunately, in the case where there is a failure in the mechanical link between the actuator and the driven device, the position of the driven device is unknown. The position sensor coupled to the actuator will continue to report the position of the actuator even when the driven device is in a different location. Such a situation is undesirable and can be dangerous in certain applications. 
   An unmet need exists for an actuator with an integral position sensor that has increased reliability and is fail safe. 
   SUMMARY OF THE INVENTION 
   It is a feature of the present invention to provide an actuator with an integral position sensor. 
   It is a feature of the present invention to provide an actuator with an integral position sensor that has increased reliability and that has a fail safe mode. 
   It is a feature of the present invention to provide an actuator and sensor assembly that includes a rotary actuator that has a driving shaft extending therefrom. A rotor has a first bore, a first flange, a second bore, a second flange and a groove. The first bore is coaxial with the second bore. The driving shaft is mounted in the first bore and is engaged with the first flange such that rotation of the driving shaft rotates the rotor. A contactor is mounted to an outer edge of the rotor. The contactor is engaged with the resistor film as the rotor rotates. The contactor and resistor film form a variable resistor. A driven shaft is mounted in the second bore and is engaged with the second flange. The rotor couples the driving shaft and the driven shaft together. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an actuator and sensor assembly. 
       FIG. 2  is an exploded view of the actuator and sensor assembly of  FIG. 1 . 
       FIG. 3  is an enlarged view of the sensor portion of  FIG. 2 . 
       FIG. 4  is a cross-sectional view of the actuator and sensor assembly of  FIG. 1 . 
       FIG. 5  is a perspective view of the inside of the sensor housing and resistor film. 
     It is noted that the drawings of the invention are not to scale. In the drawings, like numbering represents like elements among the drawings. 
   

   DETAILED DESCRIPTION 
   Referring to  FIGS. 1–5 , an embodiment of an actuator and sensor assembly  20  is shown. Actuator and sensor assembly  20  has an actuator  40  and a sensor  100 . A bracket  22  is located between actuator  40  and sensor  100 . Bracket  22  has a manifold mounting hole  23 , a sensor mounting hole  24 , a shaft hole  25 , an actuator mounting hole  26 , a slot  27 , a side  28 , a side  29 , a notch  30  and a tab  31 . Actuator  40  is mounted on side  29 . Sensor  100  is mounted on side  28 . Bracket  22  is mounted to an intake manifold  200  of an internal combustion engine. Screws  204  are fastened through manifold mounting holes  23  to hold assembly  200  to intake manifold  200 . 
   Actuator 
   Actuator  40  is a electromechanical stepper motor that has a high ratio of torque per mass and torque per power draw. Actuator  40  also has a magnetic circuit that allows a significant holding torque while using a limited amount of electric power. 
   Actuator  40  has a housing  42 . Housing  42  has a cavity  43 , pins  44  that extend from one end of housing  42  and a connector flange  45 . Actuator terminals  46  are mounted in cavity  43 . One end of terminals  46  are located in connector flange  45  and the other ends are located in cavity  43 . Sensor terminals  47  are mounted in cavity  43 . One end of terminals  47  are located in connector flange  45  and the other ends extend through slot  27  to sensor  100 . A wire harness (not shown) would mate with connector flange  45  to provide power and control signals to actuator  40 . 
   Actuator  40  has soft-magnetic parts that make up the magnetic circuits of the motor, namely: a stator  67  and a rotor  48 . Stator  67  has a hole  68 . Rotor  48  has a hole  49  and a respective multi-pole magnet  51  that is attached to rotor  48 . Magnet  51  has a hole  52  and alternating north and south regions. Poles  62  are mounted to bobbin  64 . 
   A bobbin  64  includes four coils of conventional wire windings  65 . By regulating either the direction of current passing through the wire or by changing the direction of the winding of the coils, each column can become a north or south electromagnet. 
   A driving shaft or actuator shaft  54  has ends  55  and  56 . End  56  is coupled to rotor  48  via a flat portion  57  extending into bore  107 . Shaft  54  extends through magnet  51 , stator  67  and hole  25 . A bearing  59  and bushing  69  support shaft  54 . Bearing  59  is retained by a bearing support  60 . 
   Sensor 
   Sensor  100  is mounted on side  28  of bracket  22 . Sensor  100  has a housing  140  that is mounted to bracket  22 . Housing  140  has a cavity  141 , a hole  142 , screw holes  143 , slot  144  and posts  145 . Screws  150  fasten housing  140  to bracket  22 . O-ring  132  forms a seal between bracket  22  and housing  140 . 
   Rotor  106  is mounted inside housing  140 . Rotor  106  has a bore  107 ,  108 , groove  109 , flange  110  and post  111 . Shaft end  56  is mounted in bore  107  with flat  57  engaged with a corresponding area in the bore. Shaft  54  thereby can rotate rotor  106 . Primary spring  102  is mounted in groove  109 . Primary spring  102  has an end  103  and an end  104 . End  103  is held by notch  30  and end  104  is held in groove  109 . Spring  102  biases rotor  106  to a fail safe position. 
   A metal bifurcated contactor  116  is mounted to post  111 . Contactor  116  has ends  117  and  118 . Contactor  116  is heat staked to post  111 . Contactor  116  can be made out of a precious metal alloy such as Paliney  16 . Flange  110  extends through hole  142  of cover  140 . Seal  120  is mounted around and seals flange  110 . 
   A polyimide film or element  124  is mounted in slot  144  between posts  145 . Film  124  has a pair of resistor tracks  125 , a pair of conductors  126  and a pair of contact pads  127  and  128 . Clips  134  are pressed over contact pads  127 ,  128  and sensor terminals  47 . The clips make an electrical connection between the contact pads and the sensor terminals. The end  117  of contactor  116  is in contact with one of the resistors  125 . The other end  118  is in contact with the other resistor  125 . 
   In operation, as rotor  54  rotates, ends  117  and  118  wipe or slide along resistor tracks creating a potentiometer. A voltage is applied between contact pads  127  and  128 , as contactor  116  slides, the voltage drop changes across the resistors and at contact pads  127  and  128 . Terminals  47  would be connected to external signal conditioning circuitry. As is well known in the art, the angular position of the actuator can be determined from the voltage level. The external signal conditioning circuitry may be added internally to the sensor, if desired. 
   Actuator and Sensor Mounting 
   Referring to  FIG. 4 , actuator and sensor assembly  20  is shown mounted to an intake manifold  200  of an internal combustion engine. Manifold  200  has a cavity  200 . Screws  204  are used to attached manifold  200  to bracket  22 . A driven shaft or manifold valve shaft  206  has ends  207 ,  208  and a notch  209 . End  207  is retained and held in bore  108 . End  207  can be held by a metal flat portion  210  in bore  108  engaging notch  209 . Manifold value shaft  206  would be attached to a valve or valves (not shown) in runners of an intake manifold. The purpose of the valves is to increase mixing and atomization of the fuel/air mixture. A secondary spring  152  is mounted around flange  110  between housing  140  and intake manifold  200 . Secondary spring  152  is attached to rotor  106 . Spring  152  biases rotor  106  to a fail safe position. 
   In the event of a failure of shaft  54  or  206 , springs  102  and  152  will bias rotor  106  such that contactor  116  is disengaged from resistors  125  resulting in an open circuit with zero voltage. This mode is shown in  FIG. 4  where the contactor does not touch film  124 . An engine controller can be programmed to read the zero voltage output from the sensor and respond by controlling the engine in an appropriate manner. 
   Discussion 
   One of ordinary skill in the art of designing and using actuators and sensors will realize many advantages from using the present invention. The use of two shafts, one connected to each side of the sensor, provides for a fail-safe sensor that always reads the true position of the valve shaft. 
   An additional advantage of the present invention is in case of a failure of either shaft, the rotor will rotate such that the contactors are disengaged from the resistors resulting in an open circuit with zero voltage. An engine controller can be programmed to read the zero voltage output from the sensor and respond by controlling the engine in an appropriate manner. 
   Another advantage of the present invention is that the sensor is well sealed from environmental contamination. 
   Another advantage of the present invention is that the sensor is not only connected to the actuator but is connected to the object whose position is desired to be sensed. 
   While the invention has been taught with specific reference to these embodiments, someone skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and the scope of the invention. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.