Patent Publication Number: US-9404287-B2

Title: System and method for determining appliance door status

Description:
FIELD OF THE INVENTION 
     The present disclosure relates generally to determining the status of an appliance door, and more particularly to an improved system and method of determining the status of an appliance door using an output signal provided from a door switch coupled in series with a latch motor feedback. 
     BACKGROUND OF THE INVENTION 
     An appliance can include a door lock mechanism to prevent access to a chamber of the appliance. For instance, an oven can include a door lock mechanism such that the door lock mechanism can be actuated into a locked position to prevent access to a cooking chamber. As another example, a washing machine can include a door lock mechanism such that the door lock mechanism can be actuated into a locked position to prevent access to a washing chamber. 
     Conventionally, a door lock mechanism can include a door lock latch and a latch motor coupled to the latch to actuate the latch into a locked position. The door lock latch engages a door of the appliance to achieve a locked state. Typical, door lock control systems only consider the status of the latch motor when determining whether the door lock latch has been successfully actuated into the locked position. By omitting consideration of the state of the appliance door, this system can cause a deficiency in the locking method because the door of the appliance can be open during actuation of the latch motor, resulting in the door lock latch reaching a locked position without engaging with the appliance door. 
     Thus, a need exists for an improved lock control system for an appliance that considers the state of the appliance door. A system and method can be implemented without having to increase the number of inputs and/or hardware in the control system would be particularly useful. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention. 
     One exemplary aspect of the present disclosure is directed to a control system for an appliance. The appliance includes an appliance door. The control system includes a door lock latch movable between a locked position and an unlocked position. The door lock latch is configured to prevent opening of the appliance door when in the locked position. The control system further includes a latch motor configured to drive the door lock latch between the locked position and the unlocked position, a motor feedback providing a signal indicative of the state of the latch motor, and a door switch coupled in series with the motor feedback. The control system further includes a controller configured to receive an output signal from the door switch coupled in series with the motor feedback and to determine a state of the appliance door based at least in part on the output signal from the door switch. 
     Another exemplary aspect of the present disclosure is directed to a method for determining the state of an appliance door. The method includes receiving, at a controller, an output signal of a door switch associated with the appliance door. The door switch is coupled in series with a latch motor feedback. The latch motor feedback provides a signal indicative of a state of a latch motor capable of actuating a door latch between a lock position and an unlock position. The door latch is configured to prevent opening of the appliance door when in a lock position. The method further includes identifying a latch command provided by the controller to the latch motor; and determining a state of the appliance door based at least in part on the output signal of the door switch and the latch command. 
     Yet another exemplary aspect of the present disclosure is directed to an appliance. The appliance includes an appliance door and a door lock latch movable between a locked position and an unlocked position. The door lock latch is configured to prevent opening of the appliance door when in the locked position. The appliance further includes a latch motor configured to drive the door lock latch between the locked position and the unlocked position. The appliance further includes a motor feedback providing a signal indicative of the state of the latch motor and a door switch coupled in series with the motor feedback. The appliance includes a controller configured to receive an output signal from the door switch coupled in series with the motor feedback. The controller is capable of determining a state of the appliance door based on the output signal from the door switch. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  depicts a simplified diagram of an exemplary appliance door locking system according to an exemplary embodiment of the present disclosure; 
         FIG. 2  depicts a schematic diagram of a control system for an appliance according to another exemplary embodiment of the present disclosure; 
         FIG. 3  depicts a schematic diagram of a control system for an appliance according to another exemplary embodiment of the present disclosure; 
         FIG. 4  depicts an exemplary microswitch arrangement for providing a latch motor feedback according to an exemplary embodiment of the present disclosure; and 
         FIG. 5  depicts a flow chart of a method according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     Generally, the present disclosure relates to a system and method of determining the status of an appliance door. The appliance door can include a locking system that has a door lock latch movable between a locked position and an unlocked position. The door lock latch can be configured to prevent opening of the appliance door when in the locked position. The locking system can further include a latch motor configured to drive the door lock latch between the locked position and the unlocked position. A controller can control the latch motor by sending one or more latch commands to the latch motor via a control input to the latch motor. For instance, the controller can provide a lock command to drive the latch motor to the locked position and an unlock command to drive the latch motor to an unlocked position. A motor feedback can provide a signal indicative of the state of the latch motor. 
     According to particular aspects of the present disclosure, a door switch is coupled in series with the motor feedback. The controller can receive an output signal from the door switch and determine a state of the appliance door based on the output signal. Because the door switch is coupled in series with the motor feedback, a change in the output of the door switch can be indicative of either a change in the state of the appliance door (e.g. opening of the appliance door) or a change in state of latch motor. The controller can determine the source of the change in the output signal based on the latch command provided to the latch motor. For instance, the door can be determined to be in an open state if the output signal provided from the door switch changes and the latch command provided to the motor has not changed. 
     Once the status of the door is determined, the appliance can be controlled based on the status of the appliance door. For example, the controller can shut down one or more operations when it is determined that the appliance door is in an open state. As another example, the controller can provide an error signal or alert based on the status of the door. 
     A control system configured in this manner can provide several advantages. For instance, the control system can independently determine the status of multiple doors of an appliance even if the door lock latch motors of the multiple doors are driven by common control signals. In addition, because the control system is configured by wiring a door switch in series with a control input provided to a door lock latch motor, the complexity and costs of the control system can be reduced. For instance, no further inputs to the controller or major hardware modifications are needed to determine the status of the appliance door. 
       FIG. 1  illustrates an exemplary appliance door locking system  115  for an appliance  100  according to an exemplary embodiment of the present disclosure. The appliance  100  can be an oven, microwave, dishwasher, refrigerator, washing machine, dryer, or other suitable appliance. The locking system  115  depicted in  FIG. 1  is provided for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that a wide variety of appliance door locking systems can be used in accordance with aspects of the present disclosure. 
     As shown in  FIG. 1 , the appliance  100  includes an appliance door  110  movable between an open state and a closed state. The appliance door  110  can be moved to the open state, for instance, to gain access to an interior chamber of the appliance  100 . The appliance  100  further includes a locking system  115  having a door lock latch  120  configured to engage the appliance door  110 . The door lock latch  120  is movable between a locked position and an unlocked position. When the door lock latch  120  is in the locked position and is engaging the appliance door  110 , the door lock latch  120  prevents opening of the appliance door  110 . When the door lock latch  120  is in the unlocked position, the appliance door  110  can be freely opened and closed. 
     The door lock latch  120  can be actuated between the locked position and the unlocked position by a latch motor  130 . As will be discussed in more detail below, the latch motor  130  can receive latch commands from a controller to drive the door lock latch  120  to either the locked position or the unlocked position. The latch motor  130  can be any suitable motor for driving the door lock latch  120 , such as a stepper motor. A sensor  132 , such as a motor switch or other device, can be used to provide a motor feedback signal indicative of the drive state of the latch motor  130  to a suitable device, such as a controller. 
     The appliance  100  can further include a door switch  140 . The door switch  140  is configured to open or close based on the position of the appliance door  100 . For instance, when the appliance door  110  is in a closed state, the appliance door  110  can engage a plunger  142  which causes the door switch  140  to close. When the appliance door  110  is in an open state, the appliance door  110  does not engage the plunger  142 . In this case, the door switch  140  is open. According to aspects of the present disclosure, the door switch  140  is coupled in series with a motor feedback to provide an output signal indicative of the state of the appliance door  110 . 
       FIG. 2  depicts a schematic of a control system  200  for an appliance according to an exemplary embodiment of the present disclosure. While  FIG. 2  will be discussed with reference to a control system  200  for an appliance having a single appliance door for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, should understand that the subject matter of the present disclosure is equally applicable to an appliance with multiple appliance doors. 
     The control system  200  includes a controller  210  used to control various aspect of the appliance, such as a subsystem  160  of the appliance and an alert system  170  of the appliance. The controller  210  can also provide one or more latch commands, such as lock commands and unlock commands, to the locking system  115  to control locking of the appliance door. 
     The controller  210  can be positioned in any location in the appliance. When the controller  210  is a single controller it can be the only controller in the appliance such that controller  210  controls all operations of the appliance. Alternatively, when the appliance includes a plurality of controllers, controller  210  can be a sub-controller coupled to the overall appliance controller or it could be the overall appliance controller. If controller  210  is a sub-controller, it can be located with the overall appliance controller or be separate from the overall appliance controller. 
     By way of example, any/all of the “controllers” discussed in this disclosure, may include a memory and one or more processing devices such as microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of an appliance. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor. Alternatively, the controller might also be constructed without using a microprocessor, using a combination of discrete analog and/or digital logic circuitry (such as amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform the oven control functionality instead of relying upon software. 
     Referring still to  FIG. 2 , the controller  210  can provide latch commands, such as unlock commands or lock commands, to the latch motor  130  via a control input  112 . For example, when the controller  210  sends a lock command to the latch motor  130 , the latch motor  130  drives the door lock latch  120  to a locked state. When the controller  210  sends an unlock command to the latch motor  130 , the latch motor  130  drives the door lock latch  120  to an unlocked state. 
     The control system  200  can include a sensor, such as a motor switch  132 , that provides a motor feedback signal via motor feedback  137  indicative of the drive state of the latch motor  130 . In one example, when the latch motor  130  has been driven to a locked state, the motor switch  132  closes and provides a signal indicative of the latch motor  130  being driven to a locked state. In another example, when the latch motor  130  has been driven to an unlocked state, the motor switch  132  opens and provides a signal indicative of the latch motor being driven to an unlocked state. 
     The door switch  140  is coupled in series with the motor feedback  137 . The door switch  140  provides an output signal to the controller  210  via input  145 . As discussed above, the door switch  140  can be open or closed depending on the position of the appliance door. For instance, if the appliance door is in a closed state, the door switch  140  can be closed. When the appliance door is in an open state, the door switch  140  can be opened. The controller  210  can determine the state of the appliance door based at least in part on the output signal received from the door switch  140 . 
     For instance, the controller  210  can detect a change in the output signal from the door switch  140  from a first signal state to a second signal state. This change in the output signal can be caused by one of two occurrences. In one case, the appliance door could have changed state (e.g. opened or closed) causing a corresponding change in the output of the door switch  140 . Alternatively, because the door switch  140  is coupled in series with the motor feedback  137 , the change in state of the output signal can also have been caused by a change in state of the latch motor  130 . In particular, a change in state of the latch motor  130  can cause a change in state in the motor switch  132 , leading to a change in state in the output signal provided by the door switch  140 . 
     To identify whether the change in state of the output signal is caused by the appliance door or by the latch motor  130 , the controller  210  can analyze the latch commands provided to the latch motor  130 . In particular, if the latch command provided by the controller  210  has not changed when the output signal from the door switch  140  changes signal state, the controller  210  can determine that the status of the appliance door has changed (e.g. the controller  210  can determine that the appliance door has opened). If the latch command provided by the controller  210  has changed, it can be determined that the change in the output signal results from a change in latch motor  130  position and not from a change in the appliance door state. 
     In this manner, the controller  210  can determine the state of the appliance door without any additional inputs for the door switch  140 . In particular, because the door switch  140  is coupled in series with the motor feedback  137 , the controller can receive the output signal from the door switch  140  through an input terminal normally reserved for the motor feedback  137 . The controller  210  can identify the source of a change in the output signal from the door switch  140  based on the latch commands provided by the controller  210  to the latch motor  130 . 
     Once the state of the appliance door has been determined, the controller  210  can control the appliance based on the state of the appliance door. For instance, the controller  210  can shut down a subsystem  160  of an appliance (e.g. heating elements of an oven, wash cycle of a dish washer, wash cycle of a washing machine, etc.) in response to determining that the appliance door is in an open state. In addition, the controller  210  can control alert system  170  to provide a suitable alert or other notification that the appliance door is in an open state. 
       FIG. 3  depicts a control system  300  for an appliance according to another exemplary embodiment of the present disclosure. The control system  300  will be discussed with reference to an appliance having two appliance doors for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, should understand that the control system  300  can be used with more or fewer appliance doors without deviating from the scope of the present disclosure. 
     As shown in  FIG. 3 , the control system  300  includes a controller  310  configured to control a first locking system  215  and a second locking system  315 . Similar to the controller  210  of  FIG. 2 , the controller  310  can be positioned in any location in the appliance. In addition, when controller  310  is a single controller it can be the only controller in the appliance such that controller  310  controls all operations of the appliance. Alternatively, when the appliance includes a plurality of controllers, controller  310  can be a sub-controller coupled to the overall appliance controller or it could be the overall appliance controller. If controller  310  is a sub-controller, it can be located with the overall appliance controller or be separate from the overall appliance controller. 
     As shown in  FIG. 3 , the controller  310  can control a first locking system  215 . The first locking system  215  includes a first latch motor  230  configured to actuate a first door lock latch associated with a first appliance door. The controller  310  can provide a control input that provides latch commands to control the latch motor  230 . The control input includes a lock input  212  configured to provide a lock command to the latch motor  230  and an unlock input  214  configured to provide an unlock command to the latch motor  230 . 
     The control system  300  includes a motor sensor  232  providing an output signal based on the state of the latch motor  230  to a motor feedback  237 . The motor feedback  237  is coupled in series with a door switch  240  associated with the first appliance door. The door switch  240  can provide an output signal to the controller  310  through a suitable input  245 . The controller  310  can determine the state of the first appliance door based on the output signal received from the door switch  240 . 
     According to a particular embodiment of the present disclosure, the motor sensor can include a first motor switch  234  and a second motor switch  236 . The outputs of the first motor switch  234  and the second motor switch  236  are combined to provide a signal to the motor feedback  237 . When the latch motor is in a locked position, the first motor switch  234  closes and the second motor switch  236  opens such that a lock signal is provided to the motor feedback  237 . When the latch motor is in an unlock position, the second motor switch closes  236  and the first motor switch  234  opens such that an unlock signal is provided to the motor feedback  237 . 
       FIG. 4  depicts an exemplary motor sensor  232  implementing a first motor switch  234  and a second motor switch  236  according to an exemplary embodiment of the present disclosure.  FIG. 4  depicts one exemplary motor sensor that can be used to provide a signal indicative of latch motor state. Those of ordinary skill in the art, using the disclosures provided herein, will understand that other suitable motor sensors can be used without deviating from the scope of the present disclosure. 
     As illustrated, motor sensor  232  can include specially shaped cams  260  and  262  coupled to a shaft  264  of the latch motor  230 . When the latch motor  230  is driven to a locked state, the cam  260  engages the first motor switch  234  causing the first motor switch  234  to close. At the same time, cam  262  disengages second motor switch  236  causes the second motor switch  236  to open. When the latch motor  230  is driven to an unlocked state, the cam  260  disengages the first motor switch  234  causing the first motor switch to open. At the same time, cam  262  engages the second motor switch  236  causing the second motor switch to close. 
     Referring back to  FIG. 3 , the controller  310  can determine the state of the first appliance door based on the output signal provided by the door switch  240 . For instance, if the output signal provided by the door switch  240  is in a signal state indicative of a closed door switch  240  and a closed first motor switch  234 , the controller  310  can determine that the first appliance door is in a closed and locked state. If the output signal provided by the door switch  240  is in a signal state indicative of a closed door switch  240  and a closed second motor switch  236 , the controller  310  can determine that the first appliance door is in a closed and unlocked state. 
     The output signal provided by the door switch  240  can also be in a signal state indicative of an open circuit. An output signal provided by the door switch  240  that is in a signal state indicative of an open circuit can be caused by an either opening of the first appliance door or by the latch motor  130  being in a transition position between an unlocked state or a locked state. In particular, opening of the first appliance door will lead to opening of the door switch  240  causing an output signal indicative of an open circuit. In addition, as the latch motor  130  translates between locked and unlocked positions, both motor switches  234  and  236  can be in an open state, causing an output signal to be indicative of an open circuit. 
     To identify whether the output signal indicative of an open circuit results from the opening of an appliance door or from the transitioning of the latch motor  230 , the controller  310  can analyze the latch commands provided to the latch motor  230 . In particular, if the latch commands provided by the controller  310  to the latch motor  230  have not changed when the output signal from the door switch  240  changes to a signal indicative of an open circuit, the controller  210  can determine that the status of the appliance door has changed (e.g. the controller  310  can determine that the appliance door has opened). If the latch commands provided by the controller  310  have changed, it can be determined that the change in the output signal results from a change in latch motor  230  position and not from a change in the appliance door state. 
     In addition, the controller  310  can determine whether an output signal indicative of an open circuit results from opening of the appliance door based on a lapse of a time interval after the change in the output signal from the door switch  240  to a signal indicative of an open circuit. For instance, if the controller  310  detects a change in the output signal from the door switch  240  to a signal indicative of an open circuit, the controller  310  can initiate a timer. The timer can be set for a time interval. The time interval can be equal to or greater than the time it takes for the latch motor  230  to transition between locked and unlocked positions. If the output signal remains in a signal state indicative of an open circuit after the lapse of the time interval, the controller  310  can determine that the output signal from the door switch  240  is indicative of the first appliance door being in an open state. 
     As shown in  FIG. 3 , the controller  310  can also control a second locking system  315  associated with a second appliance door. Similar to the first locking system, the second locking system  315  can include a second latch motor  330  configured to actuate a second door lock latch associated with a second appliance door. The controller  310  can provide a control input that provides latch commands to control the latch motor  330 . The control input can be a common control input for the first latch motor  230  and the second latch motor  330  and can include the lock input  312  configured to provide a lock command to the second latch motor  330  and an unlock input  314  configured to provide an unlock command to the second latch motor  330 . The first latch motor  230  and the second latch motor  330  can be controlled independently or simultaneously. 
     The control system  300  includes a motor sensor  332  providing an output signal based on the state of the second latch motor  330  to a motor feedback  337 . The motor feedback  337  is coupled in series with a door switch  340  associated with the second appliance door. The door switch  340  can provide an output signal to the controller  310  through a suitable input  345 . The controller  310  can determine the state of the second appliance door based on the output signal received from the door switch  340  according to any of the techniques discussed herein. 
       FIG. 5  depicts a flow diagram of one exemplary method ( 400 ) for determining the state of an appliance door according to an exemplary embodiment of the present disclosure. At ( 402 ), the method includes receiving an output signal from a door switch coupled in series with a latch motor feedback. The latch motor feedback provides a signal indicative of a state of a latch motor used to actuate a door lock latch between a locked position and an unlocked position. 
     At ( 404 ), the method detects a change in the output signal from the door switch from a first signal state to a second signal state. The first signal state can be indicative of a closed appliance door. The second signal state can be indicative of an open circuit. Because the door switch is coupled in series with the latch motor feedback, the second signal state can be indicative of either a change in the state of the appliance door (e.g. opening of the appliance door) or a change in the state of the latch motor. 
     To determine the source of the change in the output signal, the method at ( 406 ) determines whether there has been a change in the latch command(s) provided to the latch motor. If not, it can be determined that the state of the appliance door has changed ( 408 ). If the latch commands have changed, the method can include waiting for the lapse a time interval ( 410 ) to ensure that the latch motor has had time to fully transition to a new state (e.g. a locked state or an unlocked state). The method can then determine if the output signal is still in the second state ( 412 ). If so, it can be determined that the appliance door has changed state ( 408 ). If not, the change in the output signal must have resulted from a change in the state of the latch motor and it can be determined that the appliance door has not changed state ( 414 ). Once the state of the door has been determined, the method can include controlling the appliance based on the state of the appliance door ( 416 ). 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.