Patent Publication Number: US-2007103103-A1

Title: Bi-directional motor voltage conversion circuit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      Not Applicable  
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      Not Applicable  
     REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX  
      Not Applicable  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates in general to a motor supply circuit, and more specifically, to a bipolar voltage conversion motor supply circuit.  
      2. Description of the Related Art  
      Bi-directional small motors are commonly used for vehicle applications devices that require bidirectional movement such as a power seating system. These motors operate in a forward rotational direction and a reverse rotational direction. To operate the motor in a first rotational direction, a bipolar input voltage is provided to the input terminals of the motor to drive the motor in the first rotational direction (e.g., clockwise). To operate the motor in the reverse direction, the polarity of supply voltage is switched so that an opposite bipolar voltage input is provided to the input terminals for driving the motor in a second rotational direction (e.g., counterclockwise).  
      With respect to seat motors, and in particular for applications having seat memory, a seat controller maintains a current rotational position of the motor via a rotational position sensor so that when a stored memory seat button is actuated, the seat controller can control the polarity of the power supplied to the motor for directionally driving the motor to the position correlating to the seat position stored in memory.  
      The rotational position sensor is used to sense the rotational position of a gear member within the motor. The gear member is coupled to the gear output shaft at a first end of the shaft and is coupled to the accessory device gear output shaft at a second end. By knowing the direction and degree of rotational movement that the gear member of the motor has rotated, the seat controller can correlate the rotational position of the gear member to the positional movement of the seat (e.g., forward/backward motion). Other movements such as recline, tilt, and up/down may be correlated in a similar manner.  
      The rotational position sensor is typically powered by a unipolar voltage. The rotational position sensor receives the unipolar voltage (typically 5 volts) via a circuit separate than the circuit used to energize the electromagnetic armature. Since the motor requires that the polarity be switched for driving the motor between a forward or reverse direction, polarity on a respective circuit will vary. For this reason, a circuit providing power to energize the electromagnetic armature is used separately from the circuit used to power the rotational position sensor. As a result, additional cost and packaging space is required for the additional circuits required to energize the rotational position sensor and electromagnetic armature within the motor.  
     BRIEF SUMMARY OF THE INVENTION  
      The present invention has the advantage of powering both the position encoder and the electromagnetic armature utilizing the same voltage supply circuit input to the motor.  
      In one aspect of the present invention, a DC motor circuit is provided for an automobile accessory that includes biplolar input lines for driving an accessory motor. A bridge rectifier coupled to the bipolar input lines generates a unipolar output. A transient voltage suppressor is connected in parallel with the bridge rectifier. A voltage regulator is coupled to the unipolar output for generating a regulated DC voltage. A position encoder is powered by the regulated DC voltage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side view of a prior art illustration of an electric motor.  
       FIG. 2  is an elevation view of the prior art illustration of the electric motor of  FIG. 1   
       FIG. 3  is a schematic of a first connector for the prior art electric motor as shown in  FIG. 1 .  
       FIG. 4  is a schematic of a second connector for the prior art electric motor as shown in  FIG. 1 .  
       FIG. 5  is a side view of an electric motor according to a preferred embodiment of the present invention.  
       FIG. 6  is an elevation view of the electric motor according to the preferred embodiment of the present invention.  
       FIG. 7  is a schematic of an electrical power supply circuit according to the preferred embodiment of the present invention.  
       FIG. 8  is a perspective view of the connector of the electric motor according to the preferred embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring now to the drawings, there is illustrated in  FIG. 1  and  FIG. 2 a  side view and an elevation view, respectively, of a prior art electromagnetic motor  10 , such as a seat motor. The motor  10  includes a motor housing  12  enclosing a plurality of subcomponents such as an electromagnetic armature  14  and a gear member  16 . The motor housing  12  typically includes a plurality of subcomponent housings such as an armature housing  17  enclosing the electromagnetic armature  14 , and a gear housing  18  enclosing the gear member  16  and an intermediate worm gear (not shown). The electromagnetic armature  14  includes a shaft  22  with a worm gear that is axially aligned and coupled to the intermediate worm gear. The intermediate worm gear includes helical threads that operably engage the gear member  16  thereby providing a drive means for operating an accessory device (not shown) such as a power seat or the like. The intermediate worm gear increases the gear reduction between the electromagnetic armature  14  and the gear member  16 . Furthermore, the angle of the helical thread of the intermediate worm gear to the teeth of the gear member  16  prevents the motor from being manually back-driven. A gear output shaft  20  is integrally formed to the gear member  16  at one end of the shaft and is coupled to the accessory device at the other end of the shaft (i.e., external to the motor  10 ) for driving the accessory device. The prior art motor housing  12  further includes a first connector  24  and a second connector  26 .  
       FIG. 3  is a schematic of the first connector  24  (as shown in  FIG. 1 ) for powering the motor  10 . The first connector  24  includes a first terminal contact  28  and a second terminal contact  30 . The first connector  24  receives an input voltage via the first terminal  28  and second terminal  30  and supplies the input voltage to the electrical subcomponents of the motor  10  for driving the motor (e.g., to commutator brushes for commutating the armature in a permanent magnet DC motor or to a stator field in a brushless switch reluctance motor). Typical input voltage supplied to the motor is +/−12 to 14 volts. For a motor that requires switchable input voltage for driving the motor in a forward and reverse direction (e.g., seat motor or window lift motor), the input voltage is switched, typically using an H-bridge, prior to supplying the voltage to the first and second terminal contacts  28  and  30 . For example, a positive voltage on terminal contact  28  and a negative voltage (ground in the case of DC voltage input) on terminal contact  30  will drive the motor  10  in a forward direction, whereas switching the polarity of the voltage to provide a positive voltage on terminal contact  30  and a negative voltage on terminal contact  28  will drive the motor  10  in a reverse direction. The switchable input voltage is controlled by a controller and an H-bridge circuit (not shown).  
       FIG. 4  illustrates a schematic of the second connector  26  (as shown in  FIG. 1 ) for powering a position encoder  32  such as a non-contact position sensor. The second connector  26  is a three terminal connector. The second connector  26  includes a first terminal contact  34 , a second terminal contact  35 , and a third terminal contact  36 . The connector  26  receives an input voltage for powering the position encoder  32  via the first terminal contact  34  and the third terminal contact  36 . Unlike the switchable bipolar input voltage supplied to terminal contacts  28  and  30  for powering the motor  10 , the input voltage provided to the position encoder  32  is a unipolar voltage, such as +5 V. As a result, a first set of electrical conduits and a second set electrical conduits are used to provide respective input voltages to the motor  10  to energize the armature  14  of the motor  10  and power the position encoder  32 , respectively. The second terminal contact  35  of the second connector  26  is electrically connected to the position encoder  32  for outputting a sensed position signal from the position encoder  32  for identifying the rotational position of the gear member  16  within the motor  10 .  
       FIGS. 5 and 6  illustrate a side view and an elevation view, respectively, of a motor according to a preferred embodiment of the present invention. Using the same element numbers as described in  FIG. 1  for like references, the motor is shown generally at  40 . The motor  40  includes the motor housing  12  having an armature housing  17  and gear housing  18 . The gear housing  18  includes the second connector  26  having the three terminal contacts  34 ,  35 , and  36 . Connector  26  provides input voltage for energizing both the electromagnetic armature  14  and a position encoder  32  (shown in  FIG. 7 ) and for outputting sensed position signal from the position encoder  32 .  
       FIG. 7  is an electrical schematic for supplying input voltage for powering the motor and the position encoder according to a preferred embodiment of the present invention. An H-bridge circuit  41  is electrically connected to an external power source  42 , such as a vehicle battery (not shown). The connector  26  is connected to the H-bridge circuit  41  through the first terminal contact  34  and the third terminal contact  36 . Bipolar input lines  44  are electrically connected from the connector  26  to electrical subcomponents within the motor  40 . The bipolar input lines  44  are junctioned for providing a parallel voltage to a conversion circuit  45  and the electromagnetic armature  14 . The conversion circuit  45  includes a bridge rectifier  46  coupled to the bipolar input lines  44 . The conversion circuit  45  further includes a transient voltage suppressor  48  connected in parallel with the bridge rectifier  46 . A first capacitor  50  is connected in parallel with the transient voltage suppressor  48 . Also within the conversion circuit  45  is a voltage regulator  52  coupled to the output of the bridge rectifier  46 , the transient voltage suppressor  48 , and the capacitor  50 , respectively. A second capacitor  54  is coupled to the output of a voltage regulator  52  and is electrically connected in parallel to the position encoder  32 .  
      In operation, the input voltage  42  supplied by the external power source is input to the H-bridge circuit  41 . H-Bridge circuits are commonly known in the art and are typically constructed using relays and switches, bipolar transistors, MOSFET transistors, power MOSFET&#39;s, FET transistors, or microchips that draw low current. The H-bridge circuit can be used for driving a motor forward or backward. This is typically accomplished by switching the voltage between positive to negative (or ground) on the motor leads for reversing the direction of a motor. The voltage is thereafter switched again to drive the motor in the forward direction when required.  
      The switched output voltage generated by the H-bridge circuit  41  is provided to the connector  26  typically mounted on the motor housing  12  (i.e., gear cover  20 ). The connector  34 , as discussed earlier, includes the first and third contact terminals  34  and  36  for receiving the switched bi-polar voltage from the H-bridge circuit  41  and providing it to the bipolar input lines  44  within the motor  40 . Junction nodes  43   a  and  43   b  divides the bipolar input lines  44  for energizing the electromagnetic armature  14  and for providing the bipolar voltage to the conversion circuit  45 . The bipolar input voltage is provided to the electrical subcomponents for energizing the electromagnetic armature  14 . The various types of motors and electrical subcomponents used to energize the armature are commonly known. The type of motor used will determine which electrical subcomponents are supplied with the bipolar voltage for energizing the electromagnetic armature. The various types of motors include, but are not limited to, a DC brush motor that includes a permanent magnet motor, separately excited DC motor, a series-wound DC motor, brushless motors, AC motors, or switch reluctance motors.  
      The switchable bipolar voltage provided to the conversion circuit  45  is received by the bridge rectifier  46 . The bridge rectifier  46 , commonly known as a full-wave rectifier, provides a same polarity output voltage and current for any respective input voltage. That is, whether a positive or negative input voltage is applied across the bipolar input lines  44 , the bridge rectifier  46  rectifies the input voltage so that a same polarity voltage is output from the bridge rectifier  46  each time current flows therethrough regardless of the plurality of the bipolar input voltage.  
      The transient voltage suppressor  48  is connected in parallel to the output of the bridge rectifier  46 . The transient voltage suppressor  48  is a clamping device that suppresses sudden voltage increases (i.e., such as voltage spikes) generated by the motor  40 . Typically, large transient spikes are generated when dynamic braking occurs within the motor  40 . Dynamic braking of a motor involves connecting both fields of a motor to a same polarity input/output (i.e., both fields tied to ground, or both to positive). Connecting both sides of the field to the same polarity causes the motor to stop instantaneously as opposed to coasting to a stop. The energy leaving both sides of the field electromagnetically locks the armature in place since there is a same electromagnetic force exerted on each respective field of the motor. When this occurs, back emf generated within the motor  40  can typically range upwards of 100 Volts. Large transient spikes can damage the electrical circuitry of the motor  40  , more specifically, the position encoder  32 . The transient voltage suppressor  46  suppresses voltage increases above a predetermined voltage (e.g. clamping voltage above 23 Volts), and as a result, limits the voltage spikes to safe operating levels while directing damaging currents away from the position encoder  32 .  
      The first capacitor  50  is connected in parallel with the bridge rectifier  46  and the transient voltage suppressor  48  for reducing electrical noise during low operating voltage operations and for reducing voltage spikes that occur below that which the transient voltage suppressor  48  is rated for. Furthermore, the energy stored and output by the capacitor  50  may lessen any variation of the output of the bridge rectifier  46  caused from any voltage drops in the output voltage or current output from the rectifier bridge  46 .  
      The voltage regulator  52  receives the unipolar output voltage of the bridge rectifier  46  for regulating the DC voltage that is provided to the position encoder  32 . The voltage regulator  52  receives the unipolar output voltage from the bridge rectifier  46 , which may potentially vary, and converts it to a constant regulated voltage. Preferably, the unipolar output voltage from the bridge rectifier  46  is stepped down and regulated to 5 volts for powering the position encoder  32 . Alternatively, voltages other than 5 volts may be used (e.g., 5-15 volts) depending on the operating input voltages of the position encoder utilized. The regulated voltage is provided to the position encoder  32  via circuits  60  and  62 .  
      An energy storage device  54 , such as a second capacitor, may be connected in parallel to the position encoder  32  for storing the regulated voltage output from the voltage regulator  52 . The energy storage device  54  may be used to store and supply voltage to the position encoder  32  when voltage variances occur in the voltage output from the voltage regulator  52 .  
      The position encoder  32  is preferably a non-contact sensor, such as a hall-effect sensor or potentiometer. The position encoder  32  monitors the rotational position of the gear member  16  within the gear housing  18 . A position signal is generated identifying the rotational position of the gear member  14  within the gear housing  18  and is then output via circuit  61  to the connector  26 . Based on the type position encoder  32  used, the position signal may be a relative position signal based on the alignment of sensed device to the magnetic field as it rotates in and out of a magnetic field or may be an absolute position where the absolute position of the sensed device on the rotating gear member  14  is known at all times. The position signal is then output from the connector  26  via terminal contact  35  to a controller (not shown) for correlating the rotational position of the gear member  14  to a position of an attaching accessory device being driven by the motor  40 .  
      The output of the position encoder  32  is an open collector transistor requiring pull-up resister  63  (e.g., 1.8 kohms) to provide an output position signal between 0 and 5 volts. For example, if the position encoder  32  is a Hall-effect sensor (digital), then the output position signal will be either 0 or 5 volts. If the position encoder  32  is a potentiometer, then the output position signal can vary between 0 and 5 volts Alternatively, a 5 volt power source with the pull-up resistor may be connected to the circuit (external to the motor  40 ) extending from contact terminal  35  to the controller in place of pull-up resistor  63  connected between circuit  60  and  61 .  
       FIG. 8  illustrates a perspective view of the connector  26  according to a preferred embodiment of the present invention. The connector  26  includes an outer plastic shell  66  that is either secured to the gear cover  20  or secured to the yoke housing  17 . The connector  26  may include a key  68  so that a mating connector (not shown) is orientated correctly for interlocking both connectors. In the preferred embodiment, the connector  26  is integrated as part of the gear cover  20  (shown in  FIG. 3 ). The connector  26  includes the first, second, and third contact terminals  34 ,  35 , and  36 , respectively. The bipolar input voltage is received through connector  26  and is directed to energize the electromagnetic armature  14  and to the conversion circuit  45  for powering the position encoder  32  (shown in  FIG. 7 ). The position signal identifying the rotational position of the gear member  16  is output through connector  26  to a controller. As a result, additional circuits that required additional wiring and contact terminals to separately supply input voltage for energizing the electromagnetic armature  14  and the position encoder  32  are eliminated with the implementation of the conversion circuit  45  within the motor housing  12 . Preferably, the conversion circuit  45  is integrated within the gear cover  20 . However, the conversion circuit  45  may be packaged in locations other than the motor housing  12  that are feasible for packaging.  
      In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. For example, the present invention may be used within an AC motor with minor modifications without departing from the scope of the invention. It must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.