Hvac blower motor with speed sensor

Abstract

An HVAC system includes a heating/cooling element; an electric motor; a speed sensor; and a control device. The heating/cooling element includes a heating element, a cooling element, and heat exchangers. The motor has a rotatable shaft coupled with a blower wheel. The speed sensor senses a rotational speed of the motor shaft and the blower wheel and includes a magnet coupled with the motor shaft for rotation therewith; and a coil assembly mounted concentrically over the magnet and operable to generate an alternating signal when the magnet rotates relative to the coil. The alternating signal has an electrical characteristic that is generally proportional to the rotational speed of the shaft. The control device determines a rotational speed of the motor shaft and disables operation of the heating/cooling element when the alternating signal indicates that the rotational speed of the shaft drops below a minimum threshold speed.

Having thus described the preferred embodiment of the invention, what is claimed as new and desired to be protected by Letters Patent includes the following: 
     
         1 . A blower motor assembly for an HVAC system, the blower motor assembly comprising:
 an electric motor having a rotatable shaft for coupling with an air-moving device;   a speed sensor for sensing a rotational speed of the shaft and thus the air-moving device, the speed sensor comprising:
 a magnet coupled with the shaft of the motor for rotation therewith; and 
 a coil assembly mounted concentrically over the magnet and operable to generate an alternating signal when the magnet rotates relative to the coil, the alternating signal having an electrical characteristic that is generally proportional to the rotational speed of the shaft so that the alternating signal may be used to monitor a minimum speed of the shaft. 
   
     
     
         2 . The blower motor assembly as set forth in  claim 1 , wherein the electrical characteristic is voltage or frequency. 
     
     
         3 . The blower motor assembly as set forth in  claim 1 , wherein the coil assembly provides the alternating signal to a control board of an HVAC system. 
     
     
         4 . The blower motor assembly as set forth in  claim 1 , wherein the magnet has a central hole, the shaft has a hole in one end thereof that is axially aligned with the hole in the magnet, and the speed sensor further includes a fastener that extends through the hole in the magnet and into the hole in the shaft to couple the magnet to the shaft. 
     
     
         5 . The blower motor assembly as set forth in  claim 1 , wherein the speed sensor further comprises a bearing insert that is mounted partially around a bearing of the shaft and supports the coil assembly on one end of the motor. 
     
     
         6 . The blower motor assembly as set forth in  claim 1 , wherein the minimum speed is between 400-800 RPM. 
     
     
         7 . The blower motor assembly as set forth in  claim 1 , wherein the magnet and coil assembly are sized and configured so that the alternating signal has a peak magnitude of approximately 1-3 volts when the shaft is rotating at the minimum speed.