Patent Grant
7765818
This invention pertains generally to refrigeration units and more particularly to a chiller/refrigerator/freezer unit for an aircraft galley and a diagnostic method therefore.
For operators of passenger vehicles, it is of utmost importance to minimize maintenance costs and downtime. To this end, passenger vehicle components and subsystems are modularized to facilitate replacement. In aircraft, to enable operators to quickly and easily remove and replace faulty, broken or otherwise malfunctioning parts, many components are installed during assembly as line replaceable units (LRUs). Typically, LRUs are removed and replaced by the operator's maintenance staff (and often at the LRU manufacturer's cost, for example, if the LRU is under warranty) at the first indication of irregular operation regardless of whether the LRU has truly malfunctioned. Often, a normally-operating LRU is replaced unnecessarily because the LRU simply has an appearance or isolated instance of irregular operation, for example due to user error in operating the LRU.
One such aircraft LRU that has been replaced unnecessarily is the combination chiller/refrigerator/freezer unit (hereinafter referred to as a refrigeration unit) that is installed in the aircraft's galley. Conventional refrigeration units are user-settable for a temperature set-point. In some instances, however, aircraft staff (e.g., inexperienced flight attendants) may mis-set the temperature set-point relative to the type of items being stored in the refrigeration unit, thereby causing item spoilage. In yet other instances, aircraft staff may close the door to the refrigeration unit but fail to notice that the door was not properly closed and, therefore, the refrigeration unit may operate inefficiently and not properly cool the items being stored inside. In view of the foregoing, a refrigeration unit including a diagnostic means for discriminating between user error and unit malfunction would be an important improvement in the art.
In one aspect, a refrigeration unit is provided. The refrigeration unit includes: a housing including an insulated cavity configured to store food and beverages; a vapor cycle system disposed in the housing, the vapor cycle system operative to cool the food and beverages in the insulated cavity; a plurality of sensors disposed in the housing, the plurality of sensors in communication with the vapor cycle system and outputting data relative to the vapor cycle system; and a controller disposed in the housing, the controller, according to the data from the plurality of sensors, determining an occurrence of an event and outputting control signals to the vapor cycle system. Furthermore, the controller logs the data from the plurality of sensors to a data structure in a first logging mode, for example, at a first rate, and, upon occurrence of the event, logs the data to the data structure in a second logging mode, for example, instantaneously at the event occurrence or at a second rate. In one embodiment, the refrigeration unit may be a refrigeration line replaceable unit (LRU) configured for an aircraft galley.
In another aspect, a diagnostic method is provided for a refrigeration unit including a plurality of sensors and a controller. The method includes the steps of: receiving data from the plurality of sensors; determining an occurrence of an event relative to the data received from the plurality of sensors; if an event has not occurred, the controller operating in a first logging mode and storing the data to a data structure at a first rate; and if an event has occurred, the controller operating in a second logging mode and storing the data to the data structure instantaneously or at a rate different from the normal rate. The step of determining an occurrence of an event may further comprise steps of: detecting a warning event; detecting a fault event; and detecting an informational event.
Referring now to the Figures, a refrigeration unit and a diagnostic method therefore are provided. As shown in
The insulated cavity 130 is configured to store passenger food and beverages. For example, the insulated cavity 130 may have a volume of about 1.0 cubic feet such that the insulated cavity 130 can accommodate 12 standard wine bottles—9 standing upright on the floor of the insulated cavity and 3 lying on a shelf 132 shown in
As further shown in
Referring now to
In operation, refrigerant gas (e.g., HFC-134a) enters the compressor unit 210 as a low temperature, low-pressure vapor where it is compressed to a high pressure and temperature such that it will condense at ambient temperatures. From the compressor unit 210, the refrigerant travels to the condenser unit 220 where heat is rejected (i.e., the ambient air is cooled) and the refrigerant is condensed to a high-pressure liquid. A hot gas bypass valve 260 (e.g., a solenoid-controlled valve) couples a refrigerant outlet of the compressor unit 210 to an inlet of the evaporator unit 230. From the condenser unit 220, the now-liquid refrigerant travels through the filter/drier unit 270 where moisture and solid contaminants are removed from the refrigerant. Next, the refrigerant travels through a solenoid valve 280, which meters refrigerant flow to the proper rate and pressure. Refrigerant exiting the solenoid valve 280 enters the expansion valve 250 and is dropped to a saturation temperature corresponding to the user-selected air temperature set-point. The expansion valve 250 may be, for example, a block-type expansion valve with an internal sensing bulb. From the expansion valve 250, the refrigerant enters the evaporator unit 230 as a mixture of liquid and vapor. The liquid in the refrigerant mixture absorbs the heat from the warmer air returning from the inner cavity 130 via return 136 and becomes completely vaporized as it exits the evaporator heat exchanger. Heat absorbed in the evaporator unit 230 is rejected to ambient cabin air via an exhaust (e.g., configured on a rear side of the housing 110) by the motor-driven fan of the condenser unit 220. The motor-driven fan of the condenser unit 220 also creates a negative pressure on the inlet side of the condenser unit 220 thus drawing in ambient air through the air inlet 140. The airflow created by this fan carries the heat out the exhaust and into an outlet duct that may be provided in the galley.
The temperature of airflow through the refrigeration system 200 is monitored in various locations by a first plurality of sensors. Furthermore, the pressure and temperature of the refrigerant through the refrigeration system 200 is monitored in various locations by a second plurality of sensors. As shown in
Turning now to
The controller 500 includes a plurality of modules that are in communication with the processor 502. As shown, the plurality of modules includes a power input module 510, a memory module 520, a digital input module 530, an analog input module 540, an output module 550, a first communication module 560, a second communication module 570, a network communication module 580 and a power supply input supervisor module 590. The power input module 510 provides DC power, power protection and EMI filtering to the controller 500. 28V DC power input 511, signal ground input 512, and DC return input 513 interface with the power input module 510. The memory module 520 provides data storage for the controller 500. As shown, the memory module 520 is a 512K SRAM, but may be other types and sizes of memory. Additionally, although the memory module 520 is illustrated as being separate from the processor 502, the memory module 520 may alternatively be integral with (i.e., on-board) the processor 502.
The digital input module 530 receives and aggregates a plurality of digital input signals. As shown, the digital input module 530 interfaces with a door sensor input 531 (indicates that the door 120,
As further shown in
Although the present exemplary refrigeration unit 100 is a stand-alone unit requiring only a power connection, the controller 500 may also include a network communication module 580 so that the processor 502 may communicate with other vehicle subsystems, LRUs and the like via a communication bus or network. The controller 500 may be integral with the refrigeration unit 100 (e.g., disposed within the housing 110), however, the controller 500 may alternatively be configured outside the housing 110 distal the refrigeration unit 100 and in communication therewith via a wired or wireless link. As shown, the network communication module 580 is configured to interface the processor 502 with a bus or network using CAN protocol, but alternatively the network communication module 580 may be configured to interface the processor 502 with a bus or network using LIN, J1850, TCP/IP or other communication protocols known in the art. Power supply supervisor module 590 is in communication with the processor 502 and provides one or more of voltage, current and power monitoring for the refrigeration unit 100.
Operation of the Refrigeration Unit
During operation of the refrigeration unit 100, a user determines the temperature of the insulated cavity 130 by selecting one of seven predetermined operating modes shown in Table 1. During a “rapid pulldown mode” for fast chilling of beverages such as soft drinks and wine, it is desired to move the air through the insulated cavity 130 rapidly and also to distribute the cold air equally around each container. As can be appreciated, the present refrigeration unit 100 under control of controller 500 is operative to improve airflow distribution for temperature equalization purposes by means of reversing the rotational direction of one or more motors (e.g., the motor of evaporator unit 230). This ensures, for example, that the top of the containers will see the same temperature as the bottom of the containers during the cooling process. This reversible fan motor direction mixes the air within the insulated cavity 130 allowing for more uniform distribution of cold air.
Furthermore, in the present refrigeration unit 100, by reversing the rotational direction of one or more of the fan motors, airflow from the fan allows the warm air to enter the evaporator unit 230 for duration of time, thereby enabling a defrost cycle without the need of a standard (i.e., heating) defrost cycle. Additionally, if a standard (i.e., heating) defrost cycle is needed, reversing the fan motor of evaporator unit 230 will result in a shorter duration defrost time with less power consumption.
The controller 500 attempts to maintain the temperature within the insulated cavity 130 within about +/−2° C. of the selected temperature set point by independently controlling variable motor speeds of the evaporator unit 230, condenser unit 220 and compressor unit 210. If the controller 500 is unable to control the refrigeration system 200 to maintain the temperature within the insulated cavity 130 within about +/−2° C. of the selected temperature set point, the controller 500 may activate or otherwise provide a warning or alert. For example, the controller 500 may activate the one or more indicators 156 (
Compressor Unit Control
The controller 500 monitors return air temperature using return air temperature sensor 310 and adjusts the motor speed of the compressor unit 210 using a PID equation. The motor of the compressor unit 210 is controlled by controller 500 so that it has a minimum speed of 40%. If the return air temperature sensor 310 has malfunctioned, then data from the supply air temperature sensor 320 may be used by the controller 500 to adjust the air temperature to correspond with selected temperature set-point. In the following tables, 100% compressor speed may be, for example, 3500 RPM.
The PID temperature control equation may be overridden if the discharge pressure measured by discharge pressure sensor 370 (
Evaporator Unit Control
The speed of the motor of the evaporator unit 230 may be controlled by controller 500 according to Table 3. In this table, 100% evaporator speed may be, for example, 8500 RPM. The motor of evaporator unit 230 may have a minimum 5 seconds between starts.
Condenser Unit Control
The speed of the motor of condenser unit 220 may be controlled by the controller 500 according to Table 4. In this table, 100% condenser speed may be, for example, 8500 RPM. The motor of condenser unit 220 may remain on for 2 minutes after the motor of compressor unit 210 has stopped.
History Data Logging
The controller 500 writes sensor data and other inputs to a history log data structure for retrieval and use in diagnosing faults, malfunction, human error, etc. relative to the operation of the refrigeration unit 100. An example history log data structure may include a header that is written by the controller 500 at each initialization/power-on of the refrigeration unit 100. As shown in Table 5, the header may provide general identification of hardware and software versions, lifetime status of the refrigeration unit 100, etc.
As shown in Table 6, each data entry includes data from the plurality of sensors of the refrigeration system 200. Thus, each data entry that is written by the controller 500 to the history log data structure includes information indicative of instantaneous operation of the refrigeration unit 100 to help discriminate between real problems (e.g., faults, hardware failure, etc.) or user-error induced problems.
The controller 500 is operative to dynamically vary its data logging between at least two logging modes. That is, the interval or rate at which the controller 500 writes data entries to the history log data structure may change to suitably capture operating data and parameters of the refrigeration unit 100 for the purposes of, for example, debugging and diagnosing irregular operation. For example, data entries may be written by the controller 500 to the data structure: 1) in a normal data-logging mode every 3 minutes during normal operation; 2) in a standby data-logging mode every 15 minutes while not performing cooling operations (including after shutdown); 3) in a warning data-logging mode every 1 minute while a warning event is detected; 4) in an informational data-logging mode for logging an informational event substantially simultaneously with its occurrence; and 5) in a fault data-logging mode for logging a fault event substantially simultaneously with its occurrence. Furthermore, the controller 500, in some embodiments, may implement a rollover algorithm in which the oldest data entries are overwritten by new data entries using a “circular” list of entries.
Determination of occurrences of the events (i.e., warning events, fault events and informational events) is performed by the controller 500 relative to the plurality of received inputs (i.e., sensor data inputs and user inputs). Example warning events are defined in Table 7, example informational events are defined in Table 8 and example fault events are defined in Table 9. Warning events are generally occurrences of sensed temperatures and pressures being substantially different from predetermined (normal or expected) temperatures and pressures. Informational events generally occur relative to user-actuated state changes (e.g., mode change, temperature set-point change, door opening, etc.) of the refrigeration unit 100. Fault events may be one-time, recurring or pervasive instances of miscommunication with sensors and other components of the refrigeration system 200. Fault events occur as a function of the controller 500 monitoring system sensors and detecting when those sensors indicate a problem of some variety. The algorithms of determining fault events are designed to eliminate false alarms and erroneous non-operation by a series of confirmation checks over time, and intelligent actions (e.g., restarting) initiated by the controller 500.
Referring now to
After selecting a logging mode according to the event occurrence that was determined by the controller, the controller begins to log data entries with an appropriate (event-based) data-logging rate/interval in block 640. Next, the controller in block 660 determines if the event has ended or persists. If the event is persisting, the controller continues to log data entries in block 640 in its currently-set data-logging mode with the event-based rate/interval. However, if the controller determines that the event has ended, the controller again returns to its first data-logging mode and logs the data entries to the history log data structure at the first interval/rate. In this exemplary method, it should be appreciated that additional historical data is collected during events to thereby facilitate diagnostics and debugging of the refrigeration unit.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. It should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the invention.
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