Patent Description:
Refrigerated trailers or containers are commonly used to transport perishable goods in a cold chain distribution system. A transport refrigeration system is mounted to the trailer or container in operative association with a cargo space defined within the trailer or container for maintaining a controlled temperature environment within the cargo space.

Conventionally, transport refrigeration systems used in connection with refrigerated trailers or containers include a transport refrigeration unit having a refrigerant compressor, a condenser with one or more associated condenser fans, an expansion device, and an evaporator with one or more associated evaporator fans, which are connected via appropriate refrigerant lines in a closed refrigerant flow circuit. Air or an air/ gas mixture is drawn from the interior volume of the cargo space by means of the evaporator fan(s) associated with the evaporator, passed through the airside of the evaporator in heat exchange relationship with refrigerant whereby the refrigerant absorbs heat from the air, thereby cooling the air. The cooled air is then supplied back to the cargo space.

Existing transport refrigeration systems may include a battery. The battery may be used to provide starting current to an engine that powers a compressor (either mechanically or through a generator). The battery may also store power in engineless transport refrigeration systems. The battery may also power one or more electric devices, such as data loggers, communications devices, temperature probes, etc. Battery powered electric devices may be collectively isolated with a master switch/breaker and also individually protected with individual fuses. This configuration can be cumbersome due to (i) technician time to verify and install the proper fuses and (ii) disconnection of all electronic devices in the event of an overcurrent at the master switch/breaker.

<CIT> discloses a transport refrigeration system wherein a fault detection circuit measures a current supplied to a load, wherein power to a microprocessor is interrupted if the current exceeds a threshold.

Further relevant prior art documents are <CIT>, <CIT> and <CIT>.

The present invention is disclosed in the independent claims <NUM> and <NUM>.

According to the present invention a transport refrigeration system according to claim <NUM> includes a refrigerant compression device, a refrigerant heat rejection heat exchanger, an expansion device, and a refrigerant heat absorption heat exchanger connected in refrigerant flow communication; a battery; a supply line configured to power an electric device; a switch connecting the battery to the supply line; a return line configured to provide a connection to the electric device; a controller configured to open or close the switch in response at least one of battery voltage and current on at least one of the supply line and the return line, wherein the controller is configured to use the switch to disconnect the electric device from the battery to avoid under-voltage and over current conditions; the controller is configured to close the switch, monitor the current on at least one of the supply line and the return line and keep the switch closed if the current is less than a first current threshold; the controller is configured to open the switch after a first delay if the current on at least one of the supply line and the return line is greater than the first current threshold and less than a second current threshold; the controller is configured to open the switch after a second delay if the current on at least one of the supply line and the return line is greater than the second current threshold and less than a third current threshold; and the controller is configured to open the switch immediately if the current on at least one of the supply line and the return line is greater than the third current threshold.

Optionally, the controller is configured to close the switch, send a detection signal on the supply line and open the switch in response to a lack of current on at least one of the supply line and the return line.

Optionally,the controller is configured to monitor the battery voltage and open the switch in response to the battery voltage being less than a first battery threshold.

Optionally, after opening the switch, the controller is configured to monitor the battery voltage and close the switch in response to the battery voltage being greater than a second battery threshold.

Optionally,the second battery threshold is greater than the first battery threshold.

The system may include a second supply line configured to power a second electric device; a second switch connecting the battery to the second supply line; a second return line configured to provide a connection to the second electric device; wherein the current comprises a sum of the current on at least one of the supply line and the return line and a second current on at least one of the second supply line and the second return line.

Optionally, opening the switch comprises opening one of the switch and the second switch in response to the current and the second current.

According to another aspect, a method for providing battery protection in a transport refrigeration system comprising a refrigerant compression device, a refrigerant heat rejection heat exchanger, an expansion device, and a refrigerant heat absorption heat exchanger connected in refrigerant flow communication includes connecting a battery to a switch, the switch configured to connect the battery to a supply line configured to power an electric device; providing a return line to provide a connection to the electric device; opening or closing the switch in response at least one of battery voltage and current on at least one of the supply line and the return line; using the switch to disconnect electric devices from the battery to avoid under-voltage and over-current conditions; closing the switch, monitoring the current on at least one of the supply line and the return line and keeping the switch closed if the current is less than a first current threshold; opening the switch after a first delay if the current on at least one of the supply line and the return line is greater than the first current threshold and less than a second current threshold; opening the switch after a second delay if the current on at least one of the supply line and the return line is greater than the second current threshold and less than a third current threshold; and opening the switch immediately if the current on at least one of the supply line and the return line is greater than the third current threshold.

The method may include closing the switch, sending a detection signal on the supply line and opening the switch in response to a lack of current on at least one of the supply line and the return line.

The method may include monitoring the battery voltage and opening the switch in response to the battery voltage being less than a first battery threshold.

The method may include after opening the switch, monitoring the battery voltage and closing the switch in response to the battery voltage being greater than a second battery threshold.

Technical effects of embodiments of the present disclosure include the ability to automatically control power to supply lines in response to the presence or absence of electric devices in a transport refrigeration system. Technical effects further include the ability to avoid under-voltage and over-current conditions using switches to collectively or individually disconnect electric devices from a battery in a transport refrigeration system.

The present invention is disclosed in the following claims.

Referring to <FIG>, a transport refrigeration system <NUM> includes a refrigeration unit <NUM>, an electric generation device <NUM>, a prime mover <NUM> for driving the electric generation device <NUM>, and a controller <NUM>. The refrigeration unit <NUM> functions, under the control of the controller <NUM>, to establish and regulate a desired product storage temperature within a refrigerated cargo space wherein a perishable product is stored during transport and to maintain the product storage temperature within a specified temperature range. The refrigerated cargo space may be the cargo space of a trailer, a truck, a seaboard shipping container or an intermodal container wherein perishable cargo, such as, for example, produce, meat, poultry, fish, dairy products, cut flowers, and other fresh or frozen perishable products, is stowed for transport.

The transport refrigeration unit <NUM> includes a refrigerant compression device <NUM>, a refrigerant heat rejection heat exchanger <NUM>, an expansion device <NUM>, and a refrigerant heat absorption heat exchanger <NUM> connected in refrigerant flow communication in a closed loop refrigerant circuit and arranged in a conventional refrigeration cycle. The refrigeration unit <NUM> also includes one or more fans <NUM> associated with the refrigerant heat rejection heat exchanger <NUM> and driven by fan motor(s) <NUM> and one or more fans <NUM> associated with the refrigerant heat absorption heat exchanger <NUM> and driven by fan motor(s) <NUM>. The refrigeration unit <NUM> may also include an electric resistance heater <NUM> associated with the refrigerant heat absorption heat exchanger <NUM>. It is to be understood that other components (not shown) may be incorporated into the refrigerant circuit as desired, including for example, but not limited to, a suction modulation valve, a receiver, a filter/dryer, an economizer circuit.

The refrigerant heat rejection heat exchanger <NUM> may, for example, comprise one or more refrigerant conveying coiled tubes or one or more tube banks formed of a plurality of refrigerant conveying tubes extending between respective inlet and outlet manifolds. The fan(s) <NUM> are operative to pass air, typically ambient air, across the tubes of the refrigerant heat rejection heat exchanger <NUM> to cool refrigerant vapor passing through the tubes. The refrigerant heat rejection heat exchanger <NUM> may operate either as a refrigerant condenser, such as if the refrigeration unit <NUM> is operating in a subcritical refrigerant cycle or as a refrigerant gas cooler, such as if the refrigeration unit <NUM> is operating in a transcritical cycle.

The refrigerant heat absorption heat exchanger <NUM> may, for example, also comprise one or more refrigerant conveying coiled tubes or one or more tube banks formed of a plurality of refrigerant conveying tubes extending between respective inlet and outlet manifolds. The fan(s) <NUM> are operative to pass air drawn from the temperature controlled cargo space across the tubes of the refrigerant heat absorption heat exchanger <NUM> to heat and evaporate refrigerant liquid passing through the tubes and cool the air. The air cooled in traversing the refrigerant heat rejection heat exchanger <NUM> is supplied back to the temperature controlled cargo space. It is to be understood that the term "air" when used herein with reference to the atmosphere within the cargo space includes mixtures of air with other gases, such as for example, but not limited to, nitrogen or carbon dioxide, sometimes introduced into a refrigerated cargo space for transport of perishable produce.

The refrigerant compression device <NUM> may comprise a single-stage or multiple-stage compressor such as, for example, a reciprocating compressor or a scroll compressor. The compression device <NUM> has a compression mechanism (not shown) driven by an electric motor <NUM>. In an embodiment, the motor <NUM> may be disposed internally within the compressor with a drive shaft interconnected with a shaft of the compression mechanism, all sealed within a common housing of the compression device <NUM>.

The refrigeration system <NUM> also includes a controller <NUM> configured for controlling operation of the refrigeration system <NUM> including, but not limited to, operation of various components of the refrigerant unit <NUM> to provide and maintain a desired thermal environment within the cargo space of the truck or container, that is within the temperature controlled space in which a perishable product is stowed. The controller <NUM> may be an electronic controller including a microprocessor and an associated memory bank. The controller <NUM> controls operation of various components of the refrigerant unit <NUM>, such as the refrigerant compression device <NUM> and its associated drive motor <NUM>, the fan motors <NUM>, <NUM> and the electric resistance heater <NUM>. The controller <NUM> may also be also to selectively operate the prime mover <NUM>, typically through an electronic engine controller <NUM> operatively associated with the prime mover <NUM>.

The prime mover <NUM>, which comprises an on-board fossil-fuel engine, most commonly a diesel engine, drives the electric generation device <NUM> that generates electrical power. The drive shaft of the engine drives the shaft of the electric generation device <NUM>. In an electrically powered embodiment of the transport refrigeration unit <NUM>, the electric generation device <NUM> may comprise a single on- board, engine driven AC generator configured to generate alternating current (AC) power including at least one AC voltage at one or more frequencies. In an embodiment, the electric generation device <NUM> may, for example, be a permanent magnet AC generator or a synchronous AC generator. In another embodiment, the electric generation device <NUM> may comprise a single on-board, engine driven DC generator configured to generate direct current (DC) power at at least one voltage. As each of the fan motors <NUM>, <NUM> and the compression device drive motor <NUM> may be an AC motor or a DC motor, it is to be understood that various power converters <NUM>, such as AC to DC rectifiers, DC to AC inverters, AC to AC voltage/frequency converters, and DC to DC voltage converters, may be employed in connection with the electric generation device <NUM> as appropriate.

A battery <NUM> may be used to provide starting current to the prime mover <NUM>. The battery <NUM> may also be used to power optional equipment in the form of electric devices (e.g., data loggers, communications devices, temperature probes, etc.). In other embodiments, the prime mover <NUM> and electric generation device <NUM> are eliminated in an engineless configuration. In the engineless embodiments, the battery <NUM> provides power to the refrigeration system <NUM> and is charged by regenerative elements, shore power, etc. It is understood that the battery <NUM> may include multiple battery banks electrically connected.

<FIG> depicts a battery protection system <NUM> in an example embodiment. The battery protection system <NUM> includes a controller <NUM>, which may the implemented by the controller <NUM> of <FIG>. Battery <NUM> is connected to a voltage regulator <NUM> through a fuse F1. Power output from the voltage regulator <NUM> (e.g., <NUM> volts DC) is used to power the controller <NUM>.

The positive terminal of the battery <NUM> is also connected to one or more switches S1-S3 through fuse F1. Although three switches are shown in <FIG>, it is understood that any number switches may be used depending on the system configuration. The controller <NUM> is configured to control the switches S1-S3 to open or close, as disclosed in further detail herein. The switches S1-S3 may be transistors, relays, SCRs, etc. that are controllable by a control signal from the controller <NUM>.

Each of the switches S1-S3 is connected to a supply line L1-L3. The supply lines L1-L3 provide DC power from the battery <NUM> to electric devices E1-E3 that may be used as part of the transport refrigeration system. The electric devices E1-E3 may be referred to as options, such as data loggers, communications devices, temperature probes, etc. Returns lines R1-R3 provide the ground connection for the electric devices E1-E3 to the negative terminal of the battery <NUM>.

A voltage sensor <NUM> detects the battery <NUM> voltage, Vb, and provides the sensed battery voltage to the controller <NUM>. The voltage sensor <NUM> may be positioned at the input terminals of the switches S1-S3. A current sensor C1-C3 is located on each return line R1-R3 to sense current drawn by the electric devices E1-E3. The sensed current from the current sensors C1-C3 is provided to the controller <NUM>. The current sensors C1-C3 may be located on the supply lines S1-S3, or any other location where current drawn by the electric devices E1-E3 can be monitored.

In operation, the battery protection system <NUM> provides multiple protection processes. <FIG> depicts a process for detecting electric devices E1-E3 in an example embodiment and controlling switches S1-S3 in response to whether an electric device E1-E3 is present. Some users of the transport refrigeration system may unplug or remove one or more of electric devices E1-E3. In this situation, there is a risk of a fuse/breaker tripping or of electrical arcing. The process of <FIG> confirms that an electric device E1-E3 is present and controls switches S1-S3 accordingly.

The process begins at <NUM> where the battery protection system is powered on. At <NUM>, a detection signal is generated for each switch S1-S3. The detection signal may be a pulse generated by the controller <NUM>. The detection signal is transmitted to each switch S1-S3, with switches S1-S3 closed. At <NUM>, the controller <NUM> determines if a current is detected by each of the current sensors C1-C3. If a current is present, this indicates that an electric device E1-E3 is installed. For example, if a current is detected at current sensor C1, the controller <NUM> knows that electronic device E1 is installed. The controller <NUM> selectively keeps the switches S1-S3 closed if a respective current is detected, as shown at <NUM>. If a current is not present, this indicates that an electric device E1-E3 is not installed and controller <NUM> selectively opens the switches S1-S3 if a respective current is not detected, as shown at <NUM>.

<FIG> depicts a process for battery voltage protection in an example embodiment. For the battery <NUM> to provide sufficient power to start the prime mover <NUM>, the voltage should be maintained at a predetermined level. The process of <FIG> controls switches S1-S3 in response to battery voltage. The process begins at <NUM> where switches S1-S3 that are connected to an electric device E1-E3 are closed and the electric devices E1-E3 are powered by the battery <NUM>. At <NUM>, the controller <NUM> compares the battery voltage from voltage sensor <NUM> to a first voltage threshold (e.g., <NUM> volts). If the battery voltage is not less than the first voltage threshold, flow returns to <NUM>. If the battery voltage is less than the first voltage threshold, flow proceeds to <NUM> where the controller <NUM> sends a control signal to switches S1-S3 to open. The process may pause for a time delay (e.g., <NUM> minute) before flowing to <NUM> where the controller <NUM> determines if the battery voltage is greater than a second voltage threshold (e.g., <NUM> volts). If the battery voltage is greater than the second voltage threshold, flow proceeds to <NUM> where the switches S1-S3 that are coupled to an electric device E1-E3 may be closed. If the battery voltage is not greater than the second voltage threshold, flow proceeds to <NUM> where the switches S1-S3 remain open until the battery voltage is greater than the second voltage threshold.

<FIG> depicts a method for providing battery protection in an embodiment of the invention. The process of <FIG> controls switches S1-S3 in response to current. The process begins at <NUM> where the switches S1-S3 that are connected to an electric device E1-E3 are closed and the electric devices E1-E3 are powered by the battery <NUM>. At <NUM>, the controller receives sensed current from each of the current sensors C1-C3 and compares the sum of the sensed current from each of the current sensors C1-C3 to a first current threshold (e.g., <NUM> Amps). If the sum of the sensed current from each of the current sensors C1-C3 is less than or equal to the first current threshold, then the system is operating normally and flow returns to <NUM>.

If at <NUM>, the sum of the sensed current from each of the current sensors C1-C3 is not less than or equal to the first current threshold, flow proceeds to <NUM> where the controller <NUM> determines if the sum of the sensed current from each of the current sensors C1-C3 is greater than the first current threshold and less than or equal to a second current threshold (e.g., <NUM> Amps). If so, flow proceeds to <NUM> where the controller <NUM> pauses for a first delay (e.g., <NUM> minutes) and if the sum of the sensed current from each of the current sensors C1-C3 is still greater than the first current threshold and less than or equal to a second current threshold, the controller <NUM> disconnects the electric device(s) E1-E3 that is causing the current overload. The controller <NUM> opens the switch(es) S1-S3 corresponding to the electric device(s) E1-E3 causing the over-current situation.

If at <NUM>, the sum of the sensed current from each of the current sensors C1-C3 is greater than second current threshold, flow proceeds to <NUM> where the controller <NUM> determines if the sum of the sensed current from each of the current sensors C1-C3 is greater than the second current threshold and less than or equal to a third current threshold (e.g., <NUM> Amps). If so, flow proceeds to <NUM> where the controller <NUM> pauses for a second delay (e.g., <NUM> seconds) and if the sum of the sensed current from each of the current sensors C1-C3 is greater than the second current threshold and less than or equal to a third current threshold, the controller <NUM> disconnects the electric device(s) E1-E3 that is causing the current overload. The controller <NUM> opens the switch(es) S1-S3 to the electric device(s) E1-E3 causing the over-current situation.

If at <NUM>, the sum of the sensed current from each of the current sensors C1-C3 is greater than third current threshold, flow proceeds to <NUM> where the controller <NUM> immediately disconnects the electric device(s) E1-E3 that is causing the current overload. The controller <NUM> opens the switch(es) S1-S3 corresponding to the electric device(s) E1-E3 causing the over-current situation.

Embodiments of the disclosure provide for automatic detection of installed electric devices. This eliminates the need for a technician to install a fuse for each the electric devices. If an electric device is not present on a supply line, the corresponding switch is opened to prevent arcing from the supply line to other components. If the case of over-current situations, only the electric device causing the over-current is disconnected, rather than a fuse/breaker disrupting power to all installed electric devices.

Claim 1:
A transport refrigeration system (<NUM>) comprising:
a refrigerant compression device (<NUM>), a refrigerant heat rejection heat exchanger (<NUM>), an expansion device (<NUM>), and a refrigerant heat absorption heat exchanger (<NUM>) connected in a refrigerant flow communication;
a battery (<NUM>);
a supply line (L1, L2, L3) configured to power an electric device (E1, E2, E3);
a switch (S1, S2, S3) connecting the battery to the supply line;
a return line (R1, R2, R3) configured to provide a connection to the electric device;
a controller (<NUM>) configured to open or close the switch in response to at least one of battery voltage and current on at least one of the supply line and the return line; characterised in that
the controller is configured to use the switch to disconnect the electric device from the battery to avoid under-voltage and over-current conditions;
wherein the controller is configured to close the switch (S1, S2, S3), monitor the current on at least one of the supply line (L1, L2, L3) and the return line (R1, R2, R3) and keep the switch closed if the current is less than a first current threshold;
wherein the controller (<NUM>) is configured to open the switch (S1, S2, S3) after a first delay if the current on at least one of the supply line (L1, L2, L3) and the return line (R1, R2, R3) is greater than the first current threshold and less than a second current threshold;
wherein the controller (<NUM>) is configured to open the switch (S1, S2, S3) after a second delay if the current on at least one of the supply line (L1, L2, L3) and the return line (R1, R2, R3) is greater than the second current threshold and less than a third current threshold; and
wherein the controller (<NUM>) is configured to open the switch (S1, S2, S3) immediately if the current on at least one of the supply line (L1, L2, L3) and the return line (R1, R2, R3) is greater than the third current threshold.