POWER MANAGEMENT SYSTEM FOR A TRANSPORT REFRIGERATION UNIT

Abstract

A vehicle (100) for transporting goods includes a transport refrigeration unit (150); an engine (110); and a power management system (200; 300; 400). The power management system (200; 300; 400) includes a battery unit (240; 340; 440) electrically connected to the transport refrigeration unit (150); and a generator (230; 330; 430) mechanically connected to the engine (110), the generator (230; 330; 430) being configured to be mechanically driven by the engine (110) and to supply electrical power to the battery unit (240; 340; 440). The power management system (200; 300; 400) is configured to supply electrical power to the transport refrigeration unit (150) from the battery unit (240; 340; 440) responsive to a power demand of the transport refrigeration unit (150).

Claims

1. A vehicle (100) for transporting goods, the vehicle (100) comprising: a transport refrigeration unit (150); an engine (110); and a power management system (200; 300; 400) comprising: a battery unit (240; 340; 440) electrically connected to the transport refrigeration unit (150); and a generator (230; 330; 430) mechanically connected to the engine (110), the generator (230; 330; 430) being configured to be mechanically driven by the engine (110) and to supply electrical power to the battery unit (240; 340; 440); wherein the power management system (200; 300; 400) is configured to supply electrical power to the transport refrigeration unit (150) from the battery unit (240; 340; 440) responsive to a power demand of the transport refrigeration unit (150).

2. A vehicle (100) as claimed in claim 1, wherein the engine (110) comprises a power take-off (220; 320; 420), and wherein the engine (110) is configured to mechanically drive the generator (230; 330; 430) via the power take-off (220; 320;

420.

3. A vehicle (100) as claimed in claim 1, wherein the generator (330) is coupled to the engine (110) via a variable gearing arrangement (322).

4. A vehicle (100) as claimed in claim 1, wherein the generator (430) is coupled to the engine (110) via a clutch (424), and wherein the power management system (400) is configured to selectively engage and/or disengage the clutch (424), such that the generator (430) selectively couples to and/or decouples from the engine (110).

5. A vehicle (100) as claimed in claim 4, wherein the power management system (400) comprises a controller (441) configured to monitor a speed of the vehicle (100); wherein the controller (441) is configured to determine that the vehicle (100) is in a first state and engage the clutch (424) when the vehicle (100) is in the first state, wherein the speed of the vehicle (100) is increasing in the first state; and wherein the controller (441) is configured to determine that the vehicle (100) is in a second state and disengage the clutch (424) when the vehicle (100) is in the second state, wherein the speed of the vehicle (100) is substantially constant in the second state.

6. A vehicle (100) as claimed in claim 5, wherein the controller (441) is configured to monitor a brake pedal position of the vehicle (100); and wherein the controller (441) is configured to determine that the vehicle (100) is in a third state and disengage the clutch (424) when the vehicle (100) is in the third state, wherein the brake pedal is engaged in the third state.

7. A vehicle (100) as claimed in claim 5, wherein the controller (441) is configured to monitor a power level of the battery unit (440); wherein the controller (441) is configured to determine that the vehicle (100) is in a fourth state and disengage the clutch (424) when the vehicle (100) is in the fourth state, wherein the power level of the battery unit (440) is below a first threshold in the fourth state; and/or wherein the controller (441) is configured to determine that the vehicle (100) is in a fifth state and engage the clutch (424) when the vehicle (100) is in the fifth state, wherein the power level of the battery unit (440) is above a second threshold in the fifth state.

8. A vehicle (100) as claimed in claim 1, wherein the battery unit (240; 340; 440) is rechargeable; and wherein the battery unit (240; 340; 440) is configured to recharge when the electrical power supplied from the generator (230; 330; 430) to the battery unit (240; 340; 440) exceeds the power demand of the transport refrigeration unit (150).

9. A vehicle (100) as claimed in claim 1, wherein the battery unit (240; 340; 440) comprises: an AC/DC inverter (242; 342; 442) configured to receive electrical power from the generator (230; 330; 430); a DC/AC inverter (243; 343; 443) configured to supply electrical power to the transport refrigeration unit (150); and a power storage device (245; 345; 445) configured to receive electrical power from the AC/DC inverter (242; 342; 442), and supply electrical power to the DC/AC inverter (243; 343; 443).

10. A vehicle (100) as claimed in claim 9, wherein the battery unit (240; 340; 440) comprises a DC/DC converter (244; 344; 444) connected to each of the power storage device (245; 345; 445), the AC/DC inverter (242; 342; 442) and the DC/AC inverter (243; 343; 443).

11. A vehicle (100) as claimed in claim 1, wherein the vehicle (100) is a rigid truck.

12. A method of powering a transport refrigeration unit (150), the method comprising: mechanically driving a generator (230; 330; 430) using an engine (110), wherein the generator (230; 330; 430) is mechanically connected to the engine (110); supplying electrical power generated by the generator (230; 330; 430) to a battery unit (240; 340; 440); and supplying electrical power to the transport refrigeration unit (150) using the battery unit (240; 340; 440), responsive to a power demand of the transport refrigeration unit (150).

13. A method as claimed in claim 12, wherein the generator (430) is coupled to the engine (110) via a clutch (424), the method further comprising: monitoring a power level of the battery unit (440); and controlling the clutch (424) based on the power level of the battery unit (440).

14. A method as claimed in claim 12, the method further comprising: recharging the battery unit (240; 340; 440) when a generation rate of the generator (230; 330; 430) exceeds the power demand of the transport refrigeration unit (150).

15. A method as claimed in claim 12, wherein the battery unit (240; 340; 440) comprises an AC/DC inverter (242; 342; 442), a DC/AC inverter (243; 343; 443) and a power storage device (245; 345; 445), the method further comprising: receiving electrical power from the generator (230; 330; 430) using the AC/DC inverter (242; 342; 442); supplying electrical power from the AC/DC inverter (242; 342; 442) to the power storage device (245; 345; 445); receiving electrical power from the power storage device (245; 345; 445) using the DC/AC inverter (243; 343; 443); and supplying electrical power to the transport refrigeration unit (150) using the DC/AC inverter (243; 343; 443).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0099] Certain preferred embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:

[0100] FIG. 1 shows a schematic diagram of a vehicle;

[0101] FIG. 2 shows a schematic diagram of a first power management system;

[0102] FIG. 3 shows a schematic diagram of a second power management system; and

[0103] FIG. 4 shows a schematic diagram of a third power management system.

DETAILED DESCRIPTION OF THE INVENTION

[0104] FIG. 1 shows a schematic representation of a vehicle 100, which in the present illustration is a rigid truck comprising a cabin 105 and a storage area 115. An engine 110 of the vehicle 100 is located under and/or towards the cabin 105, the engine 110 providing a motive force to the vehicle 100 such that it is capable of transport. The vehicle 100 also comprises a transport refrigeration unit (TRU) 150 located in communication with the storage area 115. The TRU 150 is configured to regulate the environment within the storage area 115, e.g. by controlling a temperature and a humidity within the storage area 115. The TRU 150 requires a stable power source such that the storage area 115 may be reliably regulated.

[0105] According to a first embodiment of the present invention, FIG. 2 shows a power management system 200 which is provided as the power source for the TRU 150. The power management system 200 comprises a generator 230 and a battery unit 240. The generator 230 is mechanically connected to the engine 110 via mechanical driving means. In the present embodiment, the mechanical driving means comprises a power take-off 220 connected to the engine 110, the power take-off 220 also coupled directly to the generator 230. The generator 230 is in electrical communication with the battery unit 240, which in turn is in electrical communication with the TRU 150.

[0106] The battery unit 240 comprises a controller 241, an AC/DC inverter 242, a DC/DC converter 244, a DC/AC inverter 243 and a battery 245. The AC/DC inverter 242 is connected to the generator 230.

[0107] The generator 230 is configured to generate electrical power when driven by the engine 110. The power take-off 220 transfers rotational energy from the engine 110 to the generator 230, which in turn is used to generate electrical power via the generator 230. The generator 230 is thus mechanically connected to and mechanically driven by the engine 110, and supplies generated electrical power to the battery unit 240. The speed of the engine 110 is variable during operation of the vehicle 100. As the generator 230 is directly coupled to the power take-off, the speed at which the generator 230 is driven at varies proportionally to the speed of the engine 110. The rate of electrical power generated by the generator 230 hence varies with the speed of the engine 110.

[0108] The AC/DC inverter 242 is in electrical communication with the generator 230, and hence receives electrical power generated by the generator 230. The AC/DC inverter 242 converts AC electrical power generated by the generator 230 to DC electrical power. The AC/DC inverter 242 is connected to the DC/DC converter 244, which receives DC electrical power from the AC/DC inverter 242 and steps up or down the voltage of the DC electrical power received. The DC/DC converter 244 then supplies DC electrical power to the DC/AC inverter 243, which converts DC electrical power into AC electrical power, to be supplied to the TRU 150. AC electrical power is supplied to the TRU 150 at 400V, with a frequency of 50 Hz in the present embodiment. However, in various embodiments the voltage and frequency of the AC electrical power supplied can vary.

[0109] The DC/DC converter 244 is also connected in parallel with a battery 245. Whilst in the present embodiment a battery 245 is provided in the battery unit 240, in various embodiments a capacitor, a cell or the like could be used in place of, or in combination with, the battery 245.

[0110] The battery unit 240 also supplies electrical power to the TRU 150 from the battery 245. The battery 245 supplies electrical power to the DC/DC converter 244, which will step up/down the voltage as required. The DC/DC converter 244 supplies converted DC electrical power to the DC/AC inverter 243, which inverts the DC electrical power into AC electrical power, to be supplied to the TRU 150.

[0111] There are hence three mechanisms by which the battery unit 240 is capable of supplying electrical power to the TRU 150: the battery unit 240 can supply electrical power generated by the generator 230 to the TRU 150; the battery unit 240 can supply electrical power from the battery 245 to the TRU 150; or the battery unit 240 can supply electrical power from both the generator 230 and the battery 245 to the TRU 150.

[0112] The battery unit 245 is therefore able to supply electrical power to the TRU 150 responsive to a power demand of the TRU 150. For example, if the generator 230 generates enough electrical power to meet the power demand of the TRU 150, then the TRU 150 may draw electrical power from the battery unit 240 supplied by the generator 230, without drawing electrical power from the battery 245. If the generator 230 does not generate enough electrical power to meet the power demand of the TRU 150, then the TRU 150 may draw electrical power from battery 245 and the generator 230. If the generator 230 is generating no electrical power, then the TRU 150 may draw electrical power solely from the battery 245 to meet the power demand of the TRU 150.

[0113] In this respect, the battery unit 240 of the present embodiment can be considered to ‘smooth’ out the electrical power supplied to the TRU 150 by the generator 230. As the generator 230 is not required to be a steady, or sustained, source of electrical power for the TRU 150, the generator 230 does not need to be driven by a mechanism which drives the generator 230 at a sustained speed. As such, the generator 230 is able to be mechanically coupled to and mechanically driven by a power take-off 220 of the engine 110, whilst the TRU 150 is still adequately powered during operation.

[0114] Providing a power management system 200 in accordance with the present embodiment enables a TRU 150 to be reliably powered when mechanical driving means are used to drive the generator 230. Mechanical driving means which do not sustain the speed at which the generator 230 is driven are generally less expensive than mechanisms which do sustain the speed at which the generator 230 is driven and thus the power management system 200, in combination with e.g. the power take-off, may be generally less expensive than systems currently available.

[0115] The mechanical driving means shown in FIG. 1 is a power take-off 220 of the engine 110 directly connected to the generator 230. In various embodiments, other mechanical driving means can be used. For example, an engine drive belt can also be used to drive the generator 230 via the engine 110.

[0116] FIG. 3 shows a schematic representation of a second power management system 200, according to an alternative embodiment of the present invention. The architecture of the power management system 300 is the same as that of the embodiment shown in FIG. 2, except that the mechanical driving means comprises a gearing arrangement 322 located between the power take-off 320 and the generator 330. The gearing arrangement 322 is coupled to the power take-off 320 of the engine 110, and is also coupled to the generator 330.

[0117] In the present embodiment, the gearing arrangement 322 has a 1:2 gear ratio. The gearing arrangement 322 therefore doubles the speed at which the generator 330 is driven at, relative to the speed of the engine 110.

[0118] The generator 330 requires driving at a speed greater than a minimum speed threshold to ensure that electrical power is generated. The lowest speed that the generator 330 will be driven at by the engine 110, when in use, is the idle speed of the engine 110. The gearing arrangement 322 of the present embodiment is therefore configured to drive the generator 330 above its minimum speed threshold when the engine 110 is idling. Whilst the exemplary embodiment uses a 1:2 gear ratio, other gear ratios may be used, based on the specific operational speed range of the engine 110 and of the generator 330.

[0119] In some embodiments, the gearing arrangement 322 may have a controllable gear ratio, where the gear ratio is controlled based on a rotational speed of the engine 310, for example by the controller 341. This may be advantageous where the operational range of the engine 110 is greater than that of the generator 330.

[0120] FIG. 4 shows a schematic representation of a vehicle 100 comprising an engine, a TRU 150 and a third power management system 400, according to a further alternative embodiment of the present invention. The architecture of the power management system 400 is the same as that of the embodiments shown in FIG. 1 and FIG. 2, except that the mechanical driving means comprises a clutch 424 in combination with the power take-off 420. The generator 430 is coupled to the power take-off 420 via the clutch 424.

[0121] The controller 441 of the power management system 400 is in communication with the clutch 424. Via the controller 441, the power management system 400 operates the clutch 424 such that the clutch 424 is either engaged or disengaged. When the clutch 424 is engaged, the generator 430 decouples from the power take-off 420, and when the clutch 424 is not engaged, the generator 430 is coupled to the power take-off 420. By using the clutch 424, the generator 430 can therefore be selectively coupled to or decoupled from the engine 110.

[0122] Whilst in the embodiment shown in FIG. 4 the mechanical driving means comprises only a power take-off 420 and a clutch 424, in various embodiments the mechanical driving means may also comprise a gearing arrangement, such as that shown in FIG. 3. The gearing arrangement and the clutch 424 can be provided between the power take-off 420 of the engine and the generator 430, in any order.

[0123] In each of the embodiments shown in FIG. 1, FIG. 2 and FIG. 3, the battery 245, 345, 445 is rechargeable. The battery 245, 345, 445 can be recharged at least using the electrical power generated by the generator 230, 330, 430. For example, when the generation rate of the generator 230, 330, 430 exceeds the power demand of the TRU 150, any surplus electrical power can be used to recharge the battery 245, 345, 445. When the battery 245, 345, 445 is fully charged, any surplus electrical power can be dissipated within the power management system 200, 300, 400 and/or the TRU 150. Accordingly a power level of the battery 245, 345, 445 can be maintained, such that the battery 245, 345, 445 can reliably supply electrical power to the TRU 150 when the power demand of the TRU 150 exceeds the generation rate of the generator 230, 330, 430. Optionally, the battery 245, 345, 445 can also be recharged using a mains connection, e.g. using electrical power from an electric grid when the vehicle 100 is stationary.

[0124] Driving the generator 230, 330, 430 using the engine 110 increases the work done by the engine 110. As a result, a rate of fuel consumption of the engine 110 will increase when the engine 110 is driving the generator 230, 330, 430. However, as the power management system 200, 300, 400 comprises the battery 245, 345, 445, it is not necessary for the generator 230, 330, 430 to be always driven by the engine 110 when the TRU 150 is operating. Instead, the generator 230, 330, 430 can be decoupled from the engine 110, and the battery 245, 345, 445 can be used to solely power the TRU 150 in certain conditions.

[0125] Turning again to the embodiment shown in FIG. 4, the controller 441 is configured to determine a state of the vehicle 100, and the controller 441 is configured to operate the clutch 424 depending on the determined state of the vehicle 100. Thus if the vehicle 100 is in a state in which one or more conditions are met, the controller 441 will operate the clutch 424 such that the generator 430 decouples from/couples to the engine 110. Accordingly the fuel efficiency of the vehicle 100 may be improved, compared to a vehicle where the generator is always driven by the engine 110.

[0126] To determine the state of the vehicle 100, the controller 441 is configured to receive one or more operating parameters from the vehicle 100 relating to the operation of the vehicle 100. These include a speed of the vehicle 100, and if a brake pedal is engaged/depressed by a driver of the vehicle 100.

[0127] When the speed of the vehicle 100 is increasing (i.e. the vehicle is accelerating), the rate of work performed by the engine 110 naturally increases as it is required to provide a greater motive force to the vehicle 100. Accordingly, the rate of fuel consumption of the engine 110 also increases. If the engine 110 is used to drive the generator 430 during acceleration of the vehicle 100, the rate of fuel consumption of the vehicle 100 further increases.

[0128] The controller 441 is configured to engage the clutch 424 when the vehicle 100 is determined to be in a first state in which the vehicle 100 is accelerating, and where the generation of electrical power using the generator 430 is not necessary at that time. Accordingly, when the vehicle 100 is determined to be in the first state, the work required by the engine 110 can be reduced compared to if the engine 110 were to simultaneously drive the generator 430 and drive the vehicle 100 such that it was accelerating. The fuel efficiency of the engine 110 may improve as a result.

[0129] The controller 441 is configured to disengage the clutch 424 when the vehicle 100 is determined to be in a second state in which the speed of the vehicle 100 is substantially constant, and where the battery 445 is not fully charged. When the speed of the vehicle 100 is constant, the total work done required by the engine 110 is not as great as when the vehicle 100 is accelerating, and therefore coupling the generator 430 to the engine 110 at this time is not of increased detriment to the fuel efficiency of the engine 110.

[0130] Additionally, when the vehicle 100 is braking, the rate of work performed by the engine 110 naturally decreases as it is not necessarily required to provide a motive force to the vehicle 100. It is therefore desirable to drive the generator 430 using the engine 110 when the vehicle 100 is braking, as the total work required by the engine 110 is reduced at this stage. In other words, when the vehicle 100 is braking the increase to the rate of fuel consumption as a result of driving the generator 430 may be minimal.

[0131] The controller 441 is therefore configured to disengage the clutch 424 when the vehicle 100 is determined to be in a third state in which the vehicle 100 is braking, and where the battery 445 is not fully charged.

[0132] Ideally when the vehicle 100 is accelerating the generator 430 will be ideally coupled from the engine 110, and when the vehicle 100 is braking the generator 430 will be coupled to the engine 110. However, there are also a number of other conditions which in various embodiments may be considered by the controller 441 of the power management system 400, such that the battery 445 is always sufficiently charged to ensure that the TRU 150 can be adequately powered.

[0133] In the present embodiment, the controller 441 is therefore configured to monitor a power level of the battery 445. If the power level of the battery 445 is low, or is below a first threshold (i.e. 40% capacity in the present embodiment), powering the TRU 150 and/or recharging the battery 445 using electrical power generated by the generator 430 should be prioritised. Similarly, if the power level of the battery 445 is high, or is above a second threshold (i.e. 90% capacity in the present embodiment), then decoupling the generator 430 from the engine 110 to preserve fuel, and powering the TRU 150 using only the battery 445, should be prioritised.

[0134] The controller 441 is configured to disengage the clutch 424 when the vehicle 100 is determined to be in a fourth state in which the power level of the battery 445 is below the first threshold. Thus when the battery 445 is not sufficiently charged, or is at low power, the generator 430 can be coupled to the engine 110 and the battery 445 can be recharged/the power level of the battery 445 can be conserved by supplying power to the battery unit 445 via the generator 430.

[0135] The controller 441 is configured to engage the clutch 424 when the vehicle 100 is determined to be in a fifth state in which the power level of the battery 445 is above the second threshold. Thus when the battery 445 is sufficiently charged, the generator 430 can be decoupled from the engine and the fuel efficiency of the vehicle 100 may be improved.

[0136] The controller 441 is also configured to monitor a fuel level of the vehicle 100. The controller is configured to engage the clutch 424 when the vehicle 100 is determined to be in a sixth state, wherein the fuel level of the vehicle 100 is below a first fuel threshold (i.e. 20% capacity) in the sixth state and the power level of the battery 445 is not below the first threshold. By engaging the clutch 445 in the sixth state, the generator 430 can decouple from the engine 110 and hence reduce the work done required by the engine 110. The fuel efficiency of the engine 110 can improve as a result, and the remaining fuel of the engine 110 can be conserved. Of course, if the battery 445 is not sufficiently charged, the clutch 445 can remain disengaged such that the TRU 150 is still adequately powered.