Patent Description:
In transportation applications, TRUs can be built onto trailers and are configured to condition the interiors of those trailers. This allows the trailers to transport perishable goods, such as produce and medical supplies, over long distances. In the absence of the TRUs, the interiors of the trailers can get hot especially on hot days and that could negatively affect the cargo being transported. With TRUs in place, the perishable goods can be maintained at the proper temperatures in the interiors regardless of ambient conditions outside.

The TRUs remove or provide heat to the interior air based on setpoints. Power for the TRUs to do so can come from energy storage devices, such as batteries or fossil fuel driven engine or an electric generator connected to vehicle engine. In the latter case, reducing fuel consumption without otherwise affecting the ability of the TRUs to condition trailer interiors is becoming increasingly important. <CIT> discloses a control system for a compressor of an air conditioner of a vehicle. <CIT> discloses a further TRU including a condenser fan control.

According to a first aspect of the invention, a method of operating a condenser of a transport refrigeration unit (TRU) of a vehicle according to claim <NUM> is provided. The method includes determining whether an engine parameter value of the vehicle exceeds a predefined level, computing an air flow due to motion of the vehicle from the engine parameter value if the engine parameter value exceeds the predefined level, obtaining a nominal air flow due to motion of the vehicle for which the condenser is rated, determining whether the air flow due to motion of the vehicle is equal to or greater than the nominal value and switching a condenser fan off if the air flow due to motion of the vehicle is equal to or greater than the nominal value.

Optionally, the method further includes initially obtaining vehicle information from which at least the air flow due to motion of the vehicle and the nominal value are partially derived.

Optionally, the method further includes confirming that an ignition of the vehicle is on, obtaining the engine parameter value from a generator tachometer if the ignition is on and determining that the engine parameter value is within a range of unit run speeds.

Optionally, the determining of whether the engine parameter value exceeds the predefined level is executed if the engine parameter value is within the range of unit run speeds.

Optionally, the computing of the air flow due to motion of the vehicle includes computing a speed of the vehicle from the engine parameter value, determining whether the speed of the vehicle is changing and computing the air flow due to motion of the vehicle if the speed of the vehicle is changing.

Optionally, the computing of the speed of the vehicle is based on the engine parameter value , a gearbox gear ratio, a final drive ratio and a tire size marking.

Optionally, the air flow due to vehicle motion is partially derived from a duct cross-sectional area of the vehicle.

According to a second aspect of the invention, a transport refrigeration unit (TRU) of a vehicle according to claim <NUM> configured to perform the method according to the first aspect of the invention is provided. The TRU includes a condenser fan and a controller configured to switch off the condenser fan in an event a value of an air flow due to motion of the vehicle exceeds the nominal value for which the condenser fan is rated.

In accordance with additional or alternative embodiments, preconditions of the controller switching off the condenser fan are that an ignition of the vehicle is turned on and that an engine speed of the vehicle exceeds a predefined value.

The subject matter, which is regarded as the invention, is defined in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:.

For TRU operations, fuel prices play a major role in increasing or decreasing operating expenses of TRU customers. This operating expense can be reduced by reducing electrical loads on TRUs, which, in turn, reduce fuel consumption by the TRUs. One of the electrical loads that can be considered for reduction is that of the condenser fan. The condenser fan of a TRU is typically mounted over a condenser coil for heat extraction and is a power consuming component due to the need to drive the condenser fan to rotate. Switching the condenser fan off in certain instances can thus reduce power consumption and an overall level of fuel consumption.

As will be described below, electrical loading on an LCV TRU generator can be reduced by the condenser fan being switched off when the vehicle is in motion and the speed of vehicle is equal or greater than a predefined speed. When the vehicle is moving, an interaction between outside air and the vehicle results in the formation of airflows as the vehicle passes through the air around it. When the vehicle is moving at equal or greater than the predefined speed, this airflow provides for sufficient cubic feet per minute (CFM) of air for the TRU's operation. Thus, during this time, even if the condenser fan is switched off, TRU operation will not be affected. A determination of the vehicle speed can be accomplished by tachometers built into LCV TRUs or the generator(power source to TRUs) coupled to vehicle engine. These tachometers provide a reading of engine rpm to a control unit. Using this engine rpm as an input, an approximate vehicle speed can be computed. From this, a CFM experienced by a condenser can also be computed so that the condenser fan can be switch off. In some cases, a decision to switch off the condenser fan can only be made when it is determined that the vehicle is moving (i.e., in a road mode) and the engine speed is above the predefined value. In this way, switching off the condenser fan while the vehicle is in an idling condition, a standby mode or a slow moving condition can be avoided.

With reference to <FIG>, a tractor trailer system <NUM> is provided. The tractor trailer system <NUM> includes a tractor <NUM> including an operator's compartment or cab <NUM> and an engine, which acts as the drive system of the tractor trailer system <NUM>. A trailer <NUM> is coupled to the tractor <NUM>. The trailer <NUM> is a refrigerated trailer <NUM> and includes a top wall <NUM>, a directly opposed bottom wall <NUM>, opposed side walls <NUM> and a front wall <NUM>, with the front wall <NUM> being closest to the tractor <NUM>. The trailer <NUM> further includes a door or doors (not shown) at a rear wall <NUM>, opposite the front wall <NUM>. The walls of the trailer <NUM> define a cargo compartment. The trailer <NUM> is configured to maintain a cargo <NUM> located inside the cargo compartment at a selected temperature through the use of a TRU <NUM> located on the trailer <NUM>. The TRU <NUM>, as shown in <FIG>, can be located at or attached to the front wall <NUM>.

Although described herein that the TRU <NUM> may be attached to a tractor trailer, it should be appreciated that the TRU <NUM> described herein may be suitable for any refrigerated cargo system (e.g., tractor trailer, container, unit load device, etc.).

With reference to <FIG>, the TRU <NUM> is shown in more detail. The TRU <NUM> includes a housing <NUM><NUM> with intakes <NUM><NUM>. The TRU <NUM> further includes a compressor <NUM>, a condenser <NUM> with a condenser fan <NUM>, an expansion valve <NUM>, an evaporator <NUM> and an evaporator fan <NUM>. The compressor <NUM> is operably connected to a compressor motor <NUM><NUM>, which is receptive of power and uses that power to drive the compressor <NUM>. The evaporator fan <NUM> is operably connected to an evaporator fan motor <NUM><NUM>, which is receptive of power and uses that power to drive the evaporator fan <NUM>. The condenser fan <NUM> is operably connected to a condenser fan motor <NUM><NUM>, which is receptive of power and uses that power to drive the condenser fan <NUM>. Airflow is circulated into and through the cargo compartment of the trailer <NUM> by means of the TRU <NUM>. A return airflow <NUM> flows into the TRU <NUM> from the cargo compartment of the trailer <NUM> through a refrigeration unit inlet <NUM> and across the evaporator <NUM> via the evaporator fan <NUM>, thus cooling the return airflow <NUM>. The cooled return airflow <NUM>, now referred to as supply airflow <NUM>, is supplied into the cargo compartment of the trailer <NUM> through a refrigeration unit outlet <NUM>, which in some embodiments is located near the top wall <NUM> of the trailer <NUM>. The supply airflow <NUM> cools the cargo <NUM> in the cargo compartment of the trailer <NUM>. Also included in the cargo compartment can be a refrigerant leak sensor <NUM> for detecting a leak of a particular type of refrigerant or substance. It is to be understood that the refrigerant leak sensor <NUM> can be located in different locations in the system and is not limited by the example shown in <FIG>. For example, the refrigerant leak sensor <NUM> can be located in the evaporator section of the TRU <NUM>, a different portion of the cargo compartment of the trailer <NUM> or another location in the system. Upon detection by the refrigerant leak sensor <NUM>, a signal can be transmitted to controller <NUM>.

The controller <NUM> controls various aspects of the TRU <NUM> and the TRU power system. The controller <NUM> can control the compressor <NUM>, the condenser <NUM>, the expansion valve <NUM>, the evaporator <NUM> and the evaporator fan <NUM> in addition to other equipment or sensors. The controller <NUM> can also control operations of the compressor motor <NUM><NUM>, the evaporator fan <NUM> and the evaporator fan motor <NUM><NUM> as well as the condenser fan <NUM> and the condenser fan motor <NUM><NUM>. The controller <NUM> can be connected to the equipment over a wired or wireless connection (connections not shown). In some cases, the controller <NUM> can be configured to perform a low charge diagnostics calculation which is used to perform various calculations of the refrigeration system of the TRU <NUM> to determine a state of operation. In other embodiments, the low charge diagnostics calculation can be performed in a cloud network (not shown in <FIG>).

With continued reference to <FIG> and <FIG> and with additional reference to <FIG>, the TRU <NUM> as described above includes the condenser fan <NUM>, the condenser fan motor <NUM><NUM> and the controller <NUM>. As will be described below in greater detail, the controller <NUM> is configured to switch off the condenser fan <NUM> directly and/or by controlling the condenser fan motor <NUM><NUM> in an event a value of an air flow due to motion of the vehicle (i.e., an LCV or the tractor <NUM> of <FIG>) exceeds a nominal value for which the condenser fan <NUM> is rated. By switching off the condenser fan <NUM> in this manner, fuel consumption can be reduced. At the same time, since the value of the air flow due to the motion of the vehicle (i.e., an LCV or the tractor <NUM> of <FIG>) exceeds the nominal value for which the condenser fan <NUM> is rated, an amount of air flow that can be directed over the condenser <NUM> via the intakes <NUM><NUM> from the free airstream at an exterior is sufficient to make up for the lack of air flow which would otherwise be generated by the condenser fan <NUM>. In accordance with embodiments, as a way to prevent an undesirable switching off of the condenser fan <NUM>, preconditions of the controller <NUM> switching off the condenser fan <NUM> are that an ignition of the vehicle is turned on and that an engine speed of the vehicle exceeds a predefined value.

As shown in <FIG>, a method of operating a component of a TRU of a vehicle, which is a condenser <NUM> of the TRU <NUM> of <FIG> and <FIG>, is provided. The method includes determining whether an engine parameter value of the vehicle exceeds a predefined level (block <NUM>), computing a vehicle parameter value from the engine parameter value if the engine parameter value exceeds the predefined level (block <NUM>), obtaining a nominal value of the vehicle parameter value for which the component is rated (block <NUM>), determining whether the vehicle parameter value is equal to or greater than the nominal value (block <NUM>) and switching the component OFF if the vehicle parameter value is equal to or greater than the nominal value (block <NUM>). The switching of the component OFF if the vehicle parameter value is equal to or greater than the nominal value of the operation of block <NUM> can include commanding the condenser fan motor <NUM><NUM> of the condenser fan <NUM> to switch OFF.

The following description will relate to the case of the component of the TRU being the condenser <NUM> of the TRU <NUM> of <FIG> and <FIG>.

In accordance with additional embodiments, the method of <FIG> can further include initially obtaining vehicle information from which at least the vehicle parameter value and the nominal value are partially derived (block <NUM>). In addition, the method can include confirming that an ignition of the vehicle is ON (block <NUM>), obtaining the engine parameter value from a generator tachometer if the ignition is on (block <NUM>) and determining that the engine parameter value is within a predefined range (block <NUM>), where the predefined range can be a range of unit run or operation speeds. The determining of whether the engine parameter value exceeds the predefined level of the operation of block <NUM> is executed if the engine parameter value is determined to be within the predefined range in the operation of block <NUM>. In this way, the controller <NUM> is effectively prevented from undesirably switching OFF the condenser fan <NUM> unless certain preconditions (i.e., that an ignition of the vehicle is turned ON and that an engine speed of the vehicle exceeds a predefined value) are met. This in turn prevents a loss of cooling of the condenser <NUM> during normal operations of the TRU <NUM>.

With continued reference to <FIG> and with additional reference to <FIG> and in accordance with further embodiments, the engine parameter value can include a revolutions per minute (RPM) of the engine. In these or other cases, the computing of the air flow due to motion of the vehicle of block <NUM> can include computing a speed of the vehicle from the engine parameter value (block <NUM>), determining whether the speed of the vehicle is changing (block <NUM>) and computing the air flow due to motion of the vehicle if the speed of the vehicle is changing (block <NUM>). Here, the computing of the speed of the vehicle of the operation of block <NUM> is based on the engine parameter value, a gearbox gear ratio, a final drive ratio and a tire size marking as expressed in the following equation: <MAT> where Ne is the engine speed, ix is the gearbox gear ratio, i<NUM> is the final drive ratio and rw is the wheel radius. These data points can be obtained in the obtaining of the vehicle information in the operation of block <NUM>. In addition, the air flow due to vehicle motion can be partially derived from a duct cross-sectional area of the vehicle (i.e., Air Flow in CFM (Q) = Flow Velocity in Feet Per Minute (V) x Duct Cross Sectional Area (A) as illustrated in <FIG> where the Duct Cross Sectional Area (A) is Width X Height). The final value found for the air flow in these, or other cases can - also take account for losses due to duct inlet filters and internal components of the TRU <NUM>, the condenser <NUM> and/or the condenser fan <NUM>.

Technical effects and benefits of the present invention are that it can be implemented as a software change at little to no cost and a reduction in fuel consumption.

Claim 1:
A method of operating a condenser of a transport refrigeration unit (TRU) of a vehicle, the method comprising:
determining (<NUM>) whether an engine parameter value of the vehicle exceeds a predefined level;
computing (<NUM>) an air flow due to motion of the vehicle from the engine parameter value if the engine parameter value exceeds the predefined level;
obtaining (<NUM>) a nominal air flow due to motion of the vehicle for which the condenser is rated;
determining (<NUM>) whether the air flow due to motion of the vehicle is equal to or greater than the nominal value; and
switching (<NUM>) a condenser fan off if the air flow due to motion of the vehicle is equal to or greater than the nominal value.