Abstract: An apparatus for driving a fan as part of a refrigerator is disclosed. The refrigerator has a compartment, a compressor, an evaporator and a condenser. A temperature sensor is positioned in association with the compartment and outputs a sensed temperature signal as a function of the temperature in the compartment. The apparatus includes a reference circuit which provides a desired temperature signal representative of a desired temperature. A comparator compares the desired temperature signal and the sensed temperature signal and generates a cool signal when the compartment temperature is above the desired temperature. A timer times out an elapsed period of time commencing when the cool signal is generated. A motor includes a rotatable assembly in driving relation to the fan. A control circuit controls operation of the motor as a function of the sensed temperature signal and the elapsed period. Related apparatus and methods are also disclosed.

Abstract: Low refrigerant charge in a refrigeration system is detected by monitoring the compressor discharge pressure and temperature. This monitoring is accomplished with a combined pressure/temperature sensor located at or near the compressor outlet. The sensor output signals are fed to a controller which produces a low charge signal whenever a combination of high discharge temperature and a low discharge pressure is detected. The controller can optionally receive input of additional operating characteristics of the refrigeration system to provide a more accurate low charge signal. The controller is connected to an indicator and/or the compressor so that the low charge signal activates the indicator and/or deactivates the compressor.

Abstract: In a tunnel control system for traction vehicles, the normal deration function is suppressed to delay deration in a tunnel. The traction vehicle is provided with a controller having a normal operation mode and a tunnel operation mode. A tunnel indicator connected to the controller provides an indication of when the vehicle is approaching a tunnel and causes the controller to switch into the tunnel operation mode. In this mode, the controller increases cooling to reduce the temperature of the vehicle's prime mover and the control electronics prior to entering the tunnel. As the traction vehicle enters the tunnel, the controller monitors the engine oil temperature and the ambient air temperature. If the ambient air temperature exceeds a predetermined value, then the cooling of the control electronics is discontinued. If the oil temperature exceeds a threshold (which is about 10.degree. C. higher than the normal deration threshold), then power to the prime mover is derated.

Abstract: Energy efficient independent temperature control is achieved in refrigerators by minimizing system run time. A freezer thermostat activates the refrigeration system when the freezer compartment requires cooling and a fresh food thermostat which controls a damper between the two compartments. The two thermostats are operatively connected so that the freezer thermostat is prevented from switching off whenever the fresh food thermostat calls for cooling in the fresh food compartment. Thus, only the freezer thermostat is able to activate the refrigeration system, while either of the thermostats can inactivate the system.

Abstract: Energy efficient independent temperature control is achieved in refrigerators by minimizing evaporator fan on time. A circuit including a first switch responsive to a freezer thermostat and a second switch responsive to a fresh food thermostat controls operation of the refrigeration system and the evaporator fan. The first and second switches are connected so that the refrigeration system and the evaporator fan can be activated only when the freezer thermostat demands cooling. A fan interlock having one or more relays prevents the first switch from inactivating the evaporator fan if the fresh food thermostat demands cooling. Thus, the evaporator fan only runs while the refrigeration system is operating or has immediately shut off.

Abstract: A system including a control circuit and a sensing circuit controls an expansion valve in a refrigeration system using pulse width modulation. The control circuit includes a ramp generator, a pulse width modulator, and a power switch. In response to input from the sensing circuit, the control circuit produces a control signal which cyclically opens and closes the valve. The average flow rate through the valve is varied in accordance with a condition of the refrigeration system which is detected by the sensing circuit.

Abstract: Pulse width modulation is used to control the flow rate through a solenoid expansion valve in a refrigeration system. A first temperature sensor is disposed on the suction line, and a second temperature sensor is disposed in a compartment to be cooled. A controller is included for controlling the duty cycle of the pulse width modulated solenoid valve. The controller receives inputs from the two temperature sensors as a basis for controlling the duty cycle. The first temperature sensor can be located either inside or outside of the compartment. Preferred exterior locations include: immediately outside of the compartment, at the inlet of the compressor, at the inlet of the heat exchanger between the suction line and the liquid line, and at the outlet of the heat exchanger.

Abstract: Pulse width modulation is used to control the flow rate through a solenoid expansion valve in a refrigeration system. A first temperature sensor is located near the evaporator inlet, and a second temperature sensor is disposed in a compartment to be cooled. A controller is included for controlling the duty cycle of the pulse width modulated solenoid valve. The controller receives inputs from the two temperature sensors and controls the valve duty cycle based on the difference of the two temperatures. The second temperature sensor is preferably located on the back wall of the compartment and can be adjacent to the compartment air inlet, adjacent to the compartment air outlet, or between the air inlet and air outlet.

Abstract: Pulse width modulation is used to control the flow rate through a solenoid expansion valve in a refrigeration system. A device for sensing suction line temperature is provided, and a controller is included for controlling the duty cycle of the pulse width modulated solenoid valve. The controller receives input from the suction line temperature sensing device as a basis for controlling the duty cycle. The suction line temperature sensing device may be a temperature sensor disposed on the suction line at the midpoint of the heat exchanger between the suction line and the liquid line. Alternatively, the suction line temperature sensing device may include a first temperature sensor disposed on the liquid line at one end of the heat exchanger and a second temperature sensor disposed on the liquid line at another end of the heat exchanger.

Abstract: A system for conditioning air in a space by heating or cooling the air to change its temperature. A thermostat located within the space generates a two state temperature signal having a cyclic parameter which corresponds to the temperature of the air in the space as it rises and falls. A compressor supplies refrigerant to a heat exchanger by means of which changes are made in the temperature of the air. A variable speed motor drives the compressor in response to a motor control signal. A controller responds to the temperature signal and senses the cyclic parameter of the temperature signal. The controller generates the motor control signal as a function of the sensed cyclic parameter whereby the motor control signal is provided to the motor to control the torque or speed of the motor.

Abstract: Low refrigerant charge in a refrigeration system is detected by monitoring the oscillation of the thermal expansion valve. This monitoring is accomplished with a sensor which senses the oscillation of the expansion valve and produces a signal indicative of the valve oscillation. The sensor signal is fed to a monitoring controller which produces a low charge signal whenever the amplitude of valve oscillation falls below a predetermined level, thus indicating low charge conditions. The sensor is preferably a temperature sensor situated at either the outlet or the inlet of the evaporator. The system further comprises a validity evaluation controller for determining when valve oscillation is a valid indication of low charge. The validity evaluation controller analyzes a number of system operating characteristics which affect valve oscillation.

Abstract: Low charge detection for a refrigeration system is accomplished using a differential pressure sensor which detects superheat at the evaporator exit. The differential pressure sensor includes a casing having a reference chamber containing a reference charge of refrigerant. A pressure responsive snap member is disposed in the casing so as to have one side exposed to the reference chamber and another side exposed to the exit pressure of the evaporator. The snap member is normally biased into a first position but snaps to a second position when the pressure differential across it exceeds a predetermined level. When a low charge condition exits, the evaporator exit will exhibit superheat. Heat conduction through the casing raises the temperature, and thus the pressure in the reference chamber. Thus the pressure differential which causes the snap member to snap to the second position is created.

Abstract: Low refrigerant charge is detected in a refrigeration system under thermal expansion valve control with a valve stem stroke measurement switch. The switch includes a first contact mounted on the valve stem of the thermal expansion valve and a second contact mounted on the valve casing. The two contacts are aligned in the direction of valve stem motion and are relatively positioned so as to be normally closed but to open when the valve stem reaches its full stroke position. At least one of the contacts is mounted to its respective structure by a flexible member to accommodate the motion of the valve stem. The switch is connected to the compressor clutch to deactivate the compressor when opened. A timer can be provided to delay deactivation of the compressor in instances where the valve stem is just momentarily at full stroke.

Abstract: A refrigerator apparatus is provided having a cabinet with a freezer compartment and a fresh food compartment. The compartments define two passageways allowing air circulation therebetween. A refrigerator system is included having a compressor, a condenser, an expansion valve, an evaporator situated in the freezer compartment. The refrigerator system elements are connected in series in a closed loop, in a refrigerant flow relationship. A first fan is situated in the freezer compartment for providing air flow over the evaporator. A second fan is situated in one of the two passageways for providing air circulation between the two compartments. A first thermostatic controller situated in the freezer compartment for maintaining a desired temperature in the freezer compartment by causing the compressor and the first fan to operate.

Abstract: A refrigerator apparatus is provided having a cabinet with a freezer compartment and a fresh food compartment. The compartments define two passageways allowing air circulation therebetween. A refrigerator system is included having a compressor, a condenser, an expansion valve, an evaporator situated in the freezer compartment. The refrigerator system elements are connected in series in a closed loop, in a refrigerant flow relationship. A first fan is situated in the freezer compartment for providing air flow over the evaporator. A second fan is situated in one of the two passageways for providing air circulation between the two compartments. A first thermostatic controlller situated in the freezer compartment for maintaining a desired temperature in the freezer compartment by causing the compressor and the first fan to operate.

Abstract: A refrigerator apparatus is provided having a cabinet with a freezer compartment and a fresh food compartment. The compartments define two passageways allowing air circulation therebetween. A refrigerator system is included having a compressor, a condenser, an expansion valve, an evaporator situated in the freezer compartment. The refrigerator system elements are connected in series in a closed loop, in a refrigerant flow relationship. A first fan is situated in the freezer compartment for providing air flow over the evaporator. A second fan is situated in one of the two passageways for providing air circulation between the two compartments. A first thermostatic controller situated in the freezer compartment for maintaining a desired temperature in the freezer compartment by causing the compressor and the first fan to operate.

Abstract: A refrigerator apparatus is provided having a cabinet with a freezer compartment and a fresh food compartment. A refrigeration system is included having a first expansion valve, a first evaporator situated in the freezer compartment, a first and second compressor, a condenser, a second expansion valve, and a second evaporator situated in the fresh food compartment all connected together in that order and in series in a refrigerant flow relationship. First and second fans are provided in the freezer and fresh food compartments, respectively. A servovalve is connected between the first evaporator and the first compressor for reducing refrigerant flow through the first evaporator when activated. A first thermostatic controller situated in the freezer compartment causes operation of the compressors and fans when a selected temperature in the freezer is exceeded. A second thermostatic controller situated in the fresh food compartment causes operation of the servovalve when a predetermined value is reached.

Abstract: A refrigerator apparatus is provided having a cabinet with a freezer compartment and a fresh food compartment. The compartments define two passageways allowing air circulation therebetween. A refrigerator system is included having a compressor, a condenser, an expansion valve, an evaporator situated in the freezer compartment. The refrigerator system elements are connected in series in a closed loop, in a refrigerant flow relationship. A first fan is situated in the freezer compartment for providing air flow over the evaporator. A second fan is situated in one of the two passageways for providing air circulation between the two compartments. A first thermostatic controller situated in the freezer compartment by causing the compressor and the first fan to operate.

Abstract: An improved side panel adapted for use in a kitchen range is provided which has improved thermal and structural properties. The improved construction of the side panel provides a channel member attached to an inner surface of the panel and extending from a lower rear portion of the panel and range to an upper front corner of the panel and range. The channel member provides an air passageway which concentrates a buoyancy driven convective flow of air from the lower part of the range onto the upper front corner of the panel, where a localized area of high temperatures is commonly found. A crossmember attached to the inner surface of the panel is also provided, which extends from the lower front portion of the panel to the channel member and from the channel member to the upper rear portion of the panel, the crossmember abutting the sides of the channel member, the channel member and the crossmember providing structural reinforcement to the side panel permitting use of a thinner gauge steel for the side panel.

Abstract: A control system for an electrically driven variable capacity automotive air conditioning system affords the passenger maximum comfort control without overloading an electrically commutated motor compressor drive. Driver selected comfort settings are sequentially overridden to avoid overloading the motor. As motor overload conditions are alleviated the control system gradually returns to the initial driver selected comfort settings.