Temperature control systems for vehicles

DESCRIPTION

Technical Field

The present invention relates to a temperature control system for a vehicle, and in particular a vehicle such as a van or lorry which has a cab space for the driver and a separate, enclosed, temperature-controlled load space. Such a vehicle may often be referred to as a refrigerated van or lorry. The vehicle may be used for the transport of temperature-sensitive loads, e.g., pharmaceuticals, food etc., which are placed in the load space. The load space is typically accessed through one or more doors which can be at the side or the rear of the vehicle.

Summary of the Invention

The present invention provides a temperature control system for a vehicle (e.g., a refrigerated van or lorry), the vehicle comprising:

an engine (e.g., an internal combustion engine) operated under the control of an engine management system and cooled by a coolant circulated around an engine cooling circuit;

a load space; and

a heating and cooling system for selectively heating and cooling the load space, the heating and cooling system comprising:

an air mover (e.g., a blower or fan) providing a moving air stream; a heating unit with a heater (e.g., a radiator or heat-exchanger) in heat exchange with the coolant circulated around the engine cooling circuit; a cooling unit with a cooler (e.g., an evaporator); and

at least one channel (or duct) for supplying the moving air stream into the load space after it has been heated by the heater or cooled by the cooler;

wherein the temperature control system comprises: a control unit programmed with temperature setpoints including an upper temperature setpoint, a first lower temperature setpoint, and a second lower temperature setpoint that is below the first lower temperature setpoint; and

at least one temperature sensor for positioning in the load space to provide temperature measurements (i.e., a series of measurements taken at a suitable sampling rate) indicative of the temperature within the load space to the control unit;

wherein the control unit compares each measured temperature against the temperature setpoints and:

if a measured temperature is at or above the upper temperature setpoint, the control unit outputs a first command signal to command the heating and cooling system to cool the load space by placing the moving air stream in heat exchange with the cooler of the cooling unit such that the moving air stream is cooled before it is supplied into the load space;

if a measured temperature is at or below the first lower temperature setpoint, the control unit outputs a second command signal to command the heating and cooling system to heat the load space by placing the moving air stream in heat exchange with the heater of the heating unit such that the moving air stream is heated before it is supplied into the load space; and

if a measured temperature is at or below the second lower temperature setpoint, the control unit outputs a third command signal to command the engine management system to increase the idling rotational speed of the engine (e.g., the rotational speed of the engine crankshaft as measured in revolutions per minute (RPM)).

The temperature control system can be installed in a vehicle having a pre-installed heating and cooling system for selectively heating and cooling the load space. To install the temperature control system, each temperature sensor needs to be suitably positioned within the load space and connected to the control unit, and the control unit needs to be connected to the pre-installed heating and cooling system and to the engine management system, in the latter case optionally by means of a suitable cable and connector that interfaces with a corresponding vehicle-mounted connector or socket. In one arrangement, a pair of temperature sensors are connected to the control unit and are positioned at spaced locations within the load space (e.g., one at the front and one at the rear). The control unit will then receive two separate temperature measurements and these can either be compared separately against the temperature setpoints or used to derive average measured temperatures. It will be readily appreciated that in practice any suitable number of temperature sensors can be used. One or more separate temperature sensors can be used to provide measured temperatures which are compared only against the second lower temperature setpoint. More particularly, the control unit can include a first control module for controlling the heating and cooling system which is connected to one or more temperature sensors and which compares the measured temperatures (or average measured temperatures) against the upper temperature setpoint and the first lower temperature setpoint. The control unit can include a second control module for controlling the engine management system which is connected to one or more temperature sensors and which compares the measured temperatures (or average measured temperatures) against the second lower temperature setpoint. The first and second command signals (and the fourth and fifth command signals - see below) are output by the first control module. The third command signal (and the sixth command signal - see below) are output by the second control module. The control unit can comprise one or more logic modules.

The temperature setpoints are typically pre-set or factory-programmed and cannot be altered by the driver of the vehicle. In one arrangement, the upper temperature setpoint is between about 16°C and about 18°C and most preferably about 17°C, the first lower temperature setpoint is between about 15°C and about 17°C and most preferably about 16°C, and the second lower temperature setpoint is between about 7°C and about 9°C and most preferably about 8°C. The upper temperature setpoint and the first lower temperature setpoint are typically selected to define a programmed temperature range for the load space (e.g., a relatively narrow desired temperature range of between about 16°C and about 17°C). In other words, the temperature of the load space should be automatically maintained within this programmed temperature range by the temperature control system. It will be readily understood that the programmed temperature range will typically be selected with reference to the temperature range that is acceptable for the transportation of the temperature-sensitive loads.

The vehicle will typically include a primary heating and cooling system for selectively heating and cooling the vehicle cab for the benefit of the driver and any passengers. The primary heating and cooling system will normally be a conventional vehicle air conditioning system or climate control system. (As used herein, a 'climate control system' refers to a system that automatically adjusts heating and cooling to keep the cab temperature at a user-selected temperature setpoint.) For convenience, the heating and cooling system that is used for heating and cooling the load space will be referred to herein as the secondary heating and cooling system. It will be readily appreciated that the secondary heating and cooling system is controlled by the temperature control system of the present invention to automatically adjust heating and cooling of the load space to keep the load space within the programmed temperature range completely independently from the primary heating and cooling system. The secondary heating and cooling system will typically only be operated when a temperature-sensitive load is being transported by the vehicle and can be non- operational at all other times.

The coolant (e.g., water or a mixture of water and antifreeze (propylene glycol)) is circulated around the engine cooling circuit to cool the engine by absorbing heat from the engine. The engine cooling system can further include a pump for circulating the coolant around the engine cooling circuit and a radiator or heat-exchanger where the absorbed heat is transferred to a cooling air stream. The heated coolant is circulated through the heater of the heating unit where it can transfer at least part of the absorbed heat from the engine to the moving air stream provided by the air mover when it is selectively placed in heat exchange with the heater. The heater does not normally need to be turned on because coolant is circulated through it whenever the engine is being cooled by the engine cooling system. The primary heating and cooling system will normally have its own heater in heat exchange with the coolant for heating air that is supplied into the vehicle cab. The coolant circuit (i.e., as defined by channels in the engine block, coolant-carrying conduits etc.), the pump and the radiator or heat- exchanger for cooling the coolant will normally be common to both the primary and secondary heating and cooling systems.

The cooling unit of the secondary heating and cooling system typically further includes a compressor for circulating refrigerant around a refrigerant circuit, and a condenser. One or more of the components of the refrigerant circuit can be common to both the primary and secondary heating and cooling systems if appropriate. In one arrangement, the primary and secondary heating and cooling systems can have separate evaporators but have a common compressor and condenser. Separate refrigerant circuits for the primary and secondary heating and cooling systems can provide independent control of the temperature within the cab and the load space, respectively.

The heating and cooling system can include a directional flap or baffle to selectively direct the moving air stream into heat exchange with either the heater or the cooler. The directional flap or baffle can be moved (e.g., by a stepper motor) under the command of the control unit. The moving air stream is considered to be in heat exchange with the heater or the cooler if it impinges upon at least part of the heater or the cooler (optionally a part that is optimised for the exchange of heat between the moving air stream and the coolant or refrigerant, respectively) such that the moving air stream is heated or cooled before it is supplied into the load space. It will be readily understood that supplying a heated air stream into the load space will increase the temperature within the load space and that supplying a cooled air stream into the load space will decrease the temperature within the load space. The temperature control system can therefore control the operation of the heating and cooling system to maintain the load space temperature within the programmed temperature range that is acceptable for the products (e.g., pharmaceuticals, food etc.) being transported by the vehicle. The speed of the air mover can be fixed or variable, e.g., so that the speed of the moving air stream can optionally be adjusted by the temperature control system. The first command signal can command the air mover to turn on and move the directional flap or baffle to direct the moving air stream into heat exchange with the cooler. The first command signal can also command the circulation of the refrigerant around the refrigerant circuit, i.e., turn on the compressor of the cooling unit. The second command signal can command the air mover to turn on and move the directional flap or baffle to direct the moving air stream into heat exchange with the heater. If a measured temperature falls to or below the upper temperature setpoint, the control unit can output a fourth command signal to command the heating and cooling system to stop cooling the load space, e.g., by turning off the air mover and/or the compressor of the cooling unit. Similarly, if the measured temperature rises to or above the first lower temperature setpoint, the control unit can output a fifth command signal to command the heating and cooling system to stop heating the load space, e.g., by turning off the air mover. In general terms, if the load space temperature is within the programmed temperature range defined by the upper temperature setpoint and the first lower temperature setpoint, the heating and cooling system should not be operated. If the measured temperature is at or below the second lower temperature setpoint, the idling rotational speed of the engine can be increased by the engine management system to a fixed value (e.g., 1200 RPM) or to a value that can vary depending on the difference between the measured temperature and the second lower temperature setpoint. In other words, the idling rotational speed of the engine can be increased (either linearly or in a stepped manner) if the measured temperature continues to decrease, but typically with the proviso that the idling rotational speed does not exceed a pre-set maximum value. Increasing the idling rotational speed of the engine can increase the amount of heat that is absorbed by the coolant and hence the amount of heat that can be transferred to the moving air stream as a result of the heat exchange with the heater of the heating unit. Increasing the idling rotational speed of the engine is therefore particularly helpful if the load space temperature is very low. The engine cooling circuit can also be commanded to increase the rate at which the coolant is circulated through the coolant circuit, e.g., by increasing the pump speed. In some arrangements, the idling rotational speed of the engine controls the rate at which the coolant is circulated so increasing the idling rotational speed also increases the circulation rate.

If the measured temperature rises to or above the second lower temperature setpoint the control unit can output a sixth command signal to command the engine management system to stop increasing the idling rotational speed of the engine. In other words, the idling rotational speed of the engine will revert back to its normal operating level as determined by the engine management system. The heating and cooling system will normally continue to be controlled to supply a heated air stream into the load space until the measured temperature rises above the first lower temperature setpoint. In another arrangement, the fourth and fifth command signals can be output on the basis of different temperature setpoints (i.e., a second upper temperature setpoint and a third lower temperature setpoint that are slightly higher or lower than the upper temperature setpoint and the first lower temperature setpoint, respectively) to define a hysteresis or deadband between the operations that turn the air mover on and off, move the directional flap or baffle, and turn the compressor on and off. Similarly, the sixth command signal can be output on the basis of a different temperature setpoint (i.e., a fourth lower temperature setpoint that is slightly higher or lower than the second lower temperature setpoint) to define a hysteresis or deadband between the operations that control the idling rotational speed of the engine. Such a hysteresis or deadband can prevent oscillation or repeated activation-deactivation cycles.

The control unit can selectively control other operational parameters of the engine, e.g., by outputting additional command signals to the engine management system. In one arrangement, the control unit can keep the engine running if the driver is absent from the vehicle (and optionally if the vehicle is locked and/or secured) so that the heating and cooling system can continue to be operated. If the engine has already been stopped, the control unit can re-start the engine. The vehicle can optionally include a 'smart charge' function which regulates the output of the alternator for efficient charging of the vehicle battery. In particular, the battery is only charged when required, thereby reducing emissions and improving performance. In one arrangement, the control unit of the present invention can monitor the supply voltage to one or more components of the heating and cooling system that are powered by the vehicle battery. If the supply voltage falls below a first voltage setpoint or threshold, the 'smart charge' function can be temporarily disabled so that the vehicle battery is continually charged by the alternator. The 'smart charge' function can be re-enabled if the supply voltage rises above a second voltage setpoint or threshold. The first and second voltage setpoints can be the same, but are preferably different to provide control hysteresis.

The present invention further provides a vehicle (e.g., a refrigerated van or lorry) comprising:

an engine operated under the control of an engine management system and cooled by a coolant circulated around an engine cooling circuit;

a load space;

a heating and cooling system for selectively heating and cooling the load space, the heating and cooling system comprising:

an air mover providing a moving air stream;

a heating unit with a heater in heat exchange with the coolant circulated around the engine cooling circuit;

a cooling unit with a cooler; and

at least one channel for supplying the moving air stream into the load space after it has been heated by the heater or cooled by the cooler; and a temperature control system comprising:

a control unit programmed with temperature setpoints including an upper temperature setpoint, a first lower temperature setpoint, and a second lower temperature setpoint that is below the first lower temperature setpoint; and a temperature sensor positioned in the load space and providing temperature measurements indicative of the temperature within the load space to the control unit;

wherein the control unit compares each measured temperature against the temperature setpoints and:

if a measured temperature is at or above the upper temperature setpoint, the control unit outputs a first command signal to command the heating and cooling system to cool the load space by placing the moving air stream in heat exchange with the cooler of the cooling unit such that the moving air stream is cooled before it is supplied into the load space;

if a measured temperature is at or below the first lower temperature setpoint, the control unit outputs a second command signal to command the heating and cooling system to heat the load space by placing the moving air stream in heat exchange with the heater of the heating unit such that the moving air stream is heated before it is supplied into the load space; and

if a measured temperature is at or below the second lower temperature setpoint, the control unit outputs a third command signal to command the engine management system to increase the idling rotational speed of the engine.

The air mover, heating unit, and cooling unit can be positioned within a suitable outer enclosure or housing. The outer enclosure can be located within the load space.

The heated or cooled air stream can be supplied into the load space through one or more vents or openings which can be provided on any suitable surface(s) of the load space, e.g., the floor, sidewall(s) etc. The load space can be thermally insulated.

The present invention further provides a method of controlling temperature within a load space of a vehicle (e.g., a refrigerated van or lorry), the vehicle comprising: an engine operated under the control of an engine management system and cooled by a coolant circulated around an engine cooling circuit;

a load space; and

a heating and cooling system for selectively heating and cooling the load space, the heating and cooling system comprising:

an air mover providing a moving air stream;

a heating unit with a heater in heat exchange with the coolant circulated around the engine cooling circuit;

a cooling unit with a cooler; and

at least one channel for supplying the moving air stream into the load space after it has been heated by the heater or cooled by the cooler; wherein the method comprises the steps of:

comparing the temperature within the load space against temperature setpoints including an upper temperature setpoint, a first lower temperature setpoint, and a second lower temperature setpoint that is below the first lower temperature setpoint; if the temperature is at or above the upper temperature setpoint, cooling the load space by placing the moving air stream in heat exchange with the cooler of the cooling unit such that the moving air stream is cooled before it is supplied into the load space;

if the temperature is at or below the first lower temperature setpoint, heating the load space by placing the moving air stream in heat exchange with the heater of the heating unit such that the moving air stream is heated before it is supplied into the load space; and

if the temperature is at or below the second lower temperature setpoint, increasing the idling rotational speed of the engine.

Drawings

Figure 1 is a schematic diagram showing a temperature control system according to the present invention.

With reference to Figure 1, a temperature control system 1 is used to control and regulate the temperature within a load space 2 of a refrigerated van or lorry. The load space 2 is defined in part by a sidewall 2a and a floor 2b and is used to transport temperature-sensitive products (not shown) such that the temperature within the load space must be maintained within an acceptable temperature range (e.g., between 16°C and 20°C).

The refrigerated van or lorry includes an internal combustion engine 4 operated under the control of an engine management system 6. In particular, the engine management system 6 controls the idling rotational speed of the engine as well as other operating parameters.

The engine 4 is cooled by circulating a coolant (e.g., water) around a closed-loop engine cooling circuit 8.

The temperature control system 1 includes an electronic control unit 10.

A heating and cooling system 12 is used to selectively heat and cool the load space 2 under the control of the control unit 10. The heating and cooling system 12 includes a blower 14 providing a moving air stream 16, a directional flap 18, a heating unit 20, a cooling unit 22, and a channel 24 for supplying the moving air stream into the load space 2 through a vent 26. In a practical arrangement, the blower 14, directional flap 18, heating unit 20, and cooling unit 22 are located within an outer enclosure or housing that is positioned within the load space 2.

The heating unit 20 includes a heater 28 through which the coolant is circulated by a pump (not shown). Other component parts of the engine cooling system are not shown in Figure 1. The circulating coolant absorbs heat from the engine and is in heat exchange with the heater 28.

The cooling unit 22 includes an evaporator 30 and a compressor 32 for circulating a refrigerant around a closed-loop refrigerant circuit 34. Other component parts of the refrigerant circuit/cooling unit are not shown in Figure 1. The control unit 10 includes a temperature control module 36 that is connected to a first temperature sensor 38 that provides a series of first temperature measurements indicative of the temperature within the load space 2. In practice, two or more temperature sensors can be connected to the temperature control module 36 each providing a series of first temperature measurements at spaced locations within the load space 2 that can be used to derive a series of first average temperature measurements.

The temperature control module 36 is also connected to the blower 14, a stepper motor (not shown) that moves the directional flap 18, and the compressor 32 of the cooling unit 22.

The control unit 10 includes an engine speed control module 40 that is connected to a second temperature sensor 42 that provides a series of second temperature measurements indicative of the temperature within the load space 2. The engine speed control module 40 is also connected to the engine management system 6 through a suitable cable and connector/interface.

The temperature control module 36 and the engine speed control module 40, together with any other electronic components of the control unit 10, are located within an outer enclosure or housing (not shown) that is positioned at a suitable location within the refrigerated van or lorry, e.g., within the cab or the load space. The outer enclosure or housing is preferably sealed to prevent tampering or unauthorised modifications to the control unit 10, including the programmed temperature setpoints.

The temperature control module 36 is programmed with an upper temperature setpoint (e.g., 17°C) and a first lower temperature setpoint (e.g., 16°C). The temperature control module 36 therefore automatically controls the heating and cooling system 12 to maintain the load space temperature in a relatively narrow programmed temperature range of between 16°C and 17°C, which is inside the broader acceptable temperature range for the temperature-sensitive products. The temperature control module 36 compares each first measured temperature from the first temperature sensor 38 against the upper temperature setpoint and the first lower temperature setpoint. If a measured temperature is at or above the upper temperature setpoint, the temperature control module 36 outputs a first command signal to the heating and cooling system 12. In particular, the first command signal turns on the blower 14 and the compressor 32 and controls the stepper motor (not shown) to move the directional flap 18 to direct the moving air stream provided by the blower into heat exchange with the evaporator 30. The moving air stream impinges upon the evaporator 30 where it is cooled and is then supplied into the load space 2 through the channel 24 to lower the temperature within the load space. If a measured temperature is at or below the first lower temperature setpoint, the temperature control module 36 outputs a second command signal to the heating and cooling system 12. In particular, the second command signal turns on the blower 14 and controls the stepper motor (not shown) to move the directional flap 18 to direct the moving air stream 16 provided by the blower into heat exchange with the heater 28. The moving air stream 16 impinges upon the heater 28 where it is heated and is then supplied into the load space 2 through the channel 24 to raise the temperature within the load space. In Figure 1 the directional flap 18 is shown in a position where it directs the moving air stream 16 into heat exchange with the heater 28, but the directional flap is also shown (in dashed line) in its alternative position where it directs the moving air stream into heat exchange with the evaporator 30.

The engine speed control module 40 is programmed with a second lower temperature setpoint (e.g., 8°C) that is lower than the first lower temperature setpoint. The engine speed control module 40 compares each second measured temperature from the second temperature sensor 42 against the second lower temperature threshold. If a measured temperature is at or below the second lower temperature setpoint, the engine speed control module 40 outputs a third command signal to the engine management system 6. In particular, the third command signal instructs the energy management system 6 to increase the idling rotational speed of the engine (e.g., the rotational speed of the engine crankshaft when uncoupled from the drivetrain and the throttle is not depressed) to 1200 revolutions per minute (RPM). Increasing the idling rotational speed of the engine to 1200 RPM increases the amount of heat that is absorbed by the coolant and hence the amount of heat that is transferred to the moving air stream 16 as a result of the heat exchange with the heater 28. It also increases the rate at which the coolant is circulated around the coolant circuit. Because the temperature within the load space 2 will also still be below the first lower temperature setpoint, the blower 14 will be turned on and the directional flap 18 will be directing the moving air stream 16 into heat exchange with the heater 28. Increasing the amount of heat transferred between the coolant and the moving air stream will increase the temperature of the moving air stream and hence bring the load space temperature to within the programmed temperature range as quickly as possible. The blower 14 will continue to be turned on until the load space temperature is back within the programmed range - see below.

If a first measured temperature falls to or below the upper temperature setpoint, the temperature control module 36 outputs a fourth command signal to the heating and cooling system 12. In particular, the fourth command signal turns off the blower 14 and the compressor 32 to stop the cooling of the load space 2. If a first measured temperature rises to or above the first lower temperature setpoint, the temperature control module 36 outputs a fifth command signal to the heating and control system 12. In particular, the fifth command signal turns off the blower 14 to stop the heating of the load space 2.

If a second measured temperature rises to or above the second lower temperature setpoint, the engine speed control module 40 outputs a sixth command signal to command the engine management system 6 to stop increasing the idling rotational speed of the engine. Put another way, the idling rotational speed of the engine will thereafter be controlled in a conventional manner by the engine management system 6.