Load management auxiliary power system

RELATED APPLICATIONS

This application is a continuation-in-part of applicant's co-pending U.S. application Ser. No. 10/060,091 filed Jan. 29, 2002, the contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

This invention is related to auxiliary power systems, in particular, to an auxiliary power system having a load shedding voltage regulator which prioritizes air conditioning by reducing electrical power generation to minimize auxiliary engine size requirements, thus reducing space and weight requirements for the auxiliary power system.

BACKGROUND OF THE INVENTION

Total fossil fuel waste, and the associated economic waste, within the trucking industry is staggering. It is estimated that six out of every fourteen hours of truck operation are spent idling. Federal and State laws alike limit the number of hours that each truck driver can legally drive a truck in a twenty-four hour period. During the remainder of the time the driver must rest for the next available driving period. Rest periods are often spent in rest areas, truck stops or along the side of an interstate. Trucks or tractors are often supplied with a “sleeper” for the driver to spend his or her rest time. Often the sleeper includes modern amenities such as a television, VCR, DVD, satellite dish, refrigerator, air conditioner, coffee maker, even a microwave oven. While such items may run on direct current provided by an engine mounted alternator, or even alternating current by use of an inverter, the truck engine must remain running to prevent the discharge of the batteries used for starting of the diesel engine. During idle a typical diesel truck engine will burn about one gallon of diesel fuel per hour. In addition to the cost of the diesel fuel, normal maintenance costs to the truck engine and its associated systems are increased.

In order to reduce fuel and maintenance costs, trucks often utilize an auxiliary generator to provide electrical power for systems within the truck when the truck's engine is not running. The Applicant is a well known assembler of diesel engine/generators packages and has been awarded patents for various arrangements. U.S. Pat. Nos. 5,765,805, 6,047,942, 6,119,638, 6,677,684, 6,756,693 and 6,812,582 granted to the Applicant disclose combination engine/generator sets that are lightweight and of novel space saving configurations, the contents of which are incorporated herein by reference.

The prior art also discloses numerous systems by which air conditioning and heating can be provided to the interior of a truck while the main engine is not running. For example, U.S. Pat. No. 4,756,359 discloses an auxiliary power system that includes an auxiliary engine, electrical alternator, water pump, air conditioning compressor and heat exchanger. The heat exchanger is used to receive hot exhaust gases from the auxiliary engine for purposes of heating coolant routed through the truck's engine.

U.S. Pat. No. 4,762,170 discloses an auxiliary power system for trucks or other heavy duty vehicles. The system includes an auxiliary engine sized to simultaneously power an air conditioner compressor and a generator. The cooling system of the auxiliary engine is connected to the cooling system of the truck's engine to keep the truck engine warm in cold weather.

U.S. Pat. No. 5,528,901 discloses an auxiliary power system which includes an auxiliary engine sized to power an air compressor, a water pump, an A/C compressor and an oil pump. The system replaces the original bank of batteries supplied with the truck and replaces the OEM electric starter with a pneumatic starter.

Problems generally associated with the use of these prior art devices relate to size, weight, and placement of the systems. The size of an auxiliary generator is critical for vehicular use. If the overall dimensions are too large, there will be insufficient areas on a truck for which to place the system. Other problems result from complexity of installation and the costs associated therewith. Still other problems result from sharing coolant systems. Small engines rarely generate enough heat to maintain temperature within a large cooling system such as those supplied with a large truck. As a result of the constant cold cylinder temperature the small engine runs inefficiently. Some systems increase the size of the auxiliary engine or place false loads on the auxiliary engines to increase heat transferred to the large engine's cooling system to maintain higher overall temperatures. However, the false loads and oversized engines decrease the overall efficiency of these systems. Other problems and expense are incurred with the use of water-to-water or water-to-oil heat exchangers. The heat exchangers are expensive, difficult to install, and require each body of fluid to be equipped with an independent pump for fluid circulation.

It is also known to vary the output of a generator for specific applications. For example, U.S. Pat. No. 4,099,067 discloses a control for diesel-electric motor-generator sets. The device allows temporary overloads to be accommodated without engine lugging by reducing line voltage if an attempt is made to draw more than a preset maximum normal wattage. The line voltage reduction is accomplished by increasing the impedance of the voltage regulator input circuit when a signal generally proportional to line voltage and load current exceeds a preset reference signal to which it is compared.

U.S. Pat. No. 5,512,813 discloses an A/C generator output controlling apparatus. The control device determines the field current to be supplied to a field coil on the basis of a voltage deviation between a battery charging voltage and a battery target voltage.

U.S. Pat. No. 5,739,677 discloses a vehicle power generating system. The system includes a controller which varies the supply of leading phase current supplied to the power generator. The system is particularly suited for low RPM, high power generation.

U.S. Pat. No. 5,726,559 discloses a synchronous electric power generating apparatus and magnetization control method. Advance-phase currents are supplied to stator windings via semiconductor switching devices by controlling the semiconductor switching devices during power generation. The device and method are particularly suited to control rotor temperature and reduce magnetic flux in an alternating current power generator.

U.S. Pat. No. 5,726,557 discloses a vehicular power system. The device includes a rotating alternating current machine having polyphase armature coils and a full wave rectifier for rectifying the generated voltage by a plurality of SiC-MOSFETs, to give a rectified output to the battery unit. The device also includes a control device for selectively turning on the plurality of SiC-MOSFETs to raise the generated voltage by short-circuiting and open-circuiting the armature coils on the basis of the phases of voltage generated by the rotating alternating current machine.

These prior art devices are generally geared to maximizing the output of a power generating device without overloading or overcharging the electrical system of the vehicle. The engines utilized to drive these devices are generally of sufficient size to drive the generator at full capacity for extended periods. None of the prior art devices disclose or teach a system which is constructed to utilize a minimally sized engine to prioritize and drive alternative loads.

Thus, what is needed is an auxiliary power system that is lightweight, consumes a small space, and may be used to alternatively provide heating, electrical power or air conditioning to the interior of a truck. The auxiliary power system should be capable of shedding low priority demands for maximizing power supplied by the auxiliary engine.

SUMMARY OF THE INVENTION

The instant invention system includes a small diesel engine coupled to an air conditioner compressor, a generator or alternator and a combination control relay/regulator for maximizing the loads placed on the auxiliary engine. The truck operator is provided with controls for selective operation of the auxiliary power system's various features which may be operated while the truck's main engine is running or stopped.

In the preferred embodiment the auxiliary engine is sized so that it is not capable of simultaneous operation of all the auxiliary systems to their maximum capacity. In a most preferred embodiment the auxiliary engine is rated from about three HP to about eight HP. Such engines are currently available from manufacturers such as KUBOTA, and may have a horizontally or about vertically disposed cylinder.

One embodiment of the auxiliary power system includes a heating system. The heating system includes a water pump which may be electric or mechanically driven by the auxiliary engine. Operator controls permit the water pump to circulate water through the auxiliary engine to a sleeper heat exchanger, radiator or both. The heat exchanger may be remotely mounted within the interior of the truck to provide heat within the truck interior, and may further include an electric fan for forcing air across the heat exchanger to provide additional heat. The fan may be operated via the driver's controls to regulate the amount of air passed across the heat exchanger to provide warmth to the truck's interior. While the air conditioning compressor is turned off, via the driver's controls, the full capacity of the alternator or generator is available for the higher amp draws typical of cold weather where diesel engines are harder to start and more electrical accessories are in use.

During hot weather operation the driver may utilize the controls to start the auxiliary engine. The auxiliary engine may then be utilized to operate an air conditioner compressor and related air conditioner system components, wherein the truck interior is kept cool. During this mode the auxiliary engine is also utilized to operate the alternator or generator to replenish power drawn from the truck batteries. In order for the auxiliary engine to provide power for both accessories, a control relay/regulator is utilized to switch the input field of the alternator, thereby reducing alternator output to maximize the power output of the auxiliary engine. Should the truck accessories draw more electrical power than the alternator or generator supply during such a peak demand, the truck batteries operate as a reserve power source. When the air conditioning compressor cycles off, the control relay/regulator causes the alternator or generator to increase electrical output to replenish the truck batteries and supply electrical power to other accessories. In this manner the power output provided by the auxiliary engine may be more fully utilized than in prior art power systems.

Thus, an objective of the instant invention is to teach an auxiliary power system for trucks that utilizes a minimally sized engine to selectively operate air conditioning, heating and power generating systems.

Another objective of the instant invention is to teach a minimally sized auxiliary power system for trucks capable of selectively providing air conditioning, heating, and electrical power to the interior area of the truck.

Still another objective of the instant invention is to teach an auxiliary power system having a control relay/regulator constructed and arranged to maximize utilization of the power supplied by the auxiliary engine.

Yet another objective of the instant invention is to teach an auxiliary power system which includes a control relay/regulator constructed and arranged to maximize utilization of power supplied by an auxiliary engine by controlled reduction of electrical power production for simultaneous air conditioner compressor operation.

Still yet another objective of the instant invention is to teach an auxiliary power system which utilizes existing truck batteries as a power exchanger for peak accessory loads.

Another objective of the invention is to teach an auxiliary power system for trucks that captures heat from the engine coolant for warming of the truck interior.

Yet another objective of the invention is to teach the use of an auxiliary power system that is inexpensive, small in size and lightweight.

Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of the instant invention auxiliary power system;

FIG. 2 is a diagrammatic representation of the instant invention auxiliary power system used in conjunction with an under bunk heating and air conditioning system; and

FIG. 3 is a diagrammatic representation of the instant invention auxiliary power system in a heat providing mode.

DETAILED DESCRIPTION

Now referring to FIG. 1, a diagrammatic representation of one embodiment of the instant invention auxiliary power system 100 is illustrated. The auxiliary power system generally includes an auxiliary engine 10 for selectively providing power to an electrical generation system 102, an air conditioning system 104, and a heating system 106. In the preferred embodiment the auxiliary engine is sized so that it is not capable of simultaneous operation of the air conditioning system and the electrical generation system to their respective full capacities. The auxiliary power system includes a unique control relay/regulator combination 24, 28 for reducing electrical power produced by the electrical generation system 102 during simultaneous operation of the air conditioning system 104. This construction and arrangement permits the size and weight of the auxiliary power system to be substantially smaller than the power systems of the prior art. The arrangement also permits the auxiliary power system to utilize a small single cylinder diesel engine which requires less frequent oil change intervals than those required by the larger engines of the prior art.

Referring to FIGS. 1-3, the auxiliary engine 10 is coupled to a refrigerant compressor, e.g. air conditioner compressor 12 and an alternator 22. The air conditioner compressor is generally an automotive style compressor which includes a magnetic clutch, well known in the art, suitable for compressing any of the various refrigerants, also well known in the art. In one embodiment the compressor 12 is constructed and arranged to cooperate with the accumulator (not shown), expansion valve (not shown), evaporator 16, condenser 14 and air conditioner controls 18 supplied with a truck.

In the preferred embodiment, a high output automotive style alternator 22 is suitably coupled to the auxiliary engine 10 for rotation thereof. The alternator 22 may be based on 12 volts, 24 volts or other voltage dependant upon the trucks electrical system. In an alternative embodiment, a generator may be utilized in place of the alternator 22 to provide electrical current to various air conditioner support components and other accessories as well as batteries. The power produced by the alternator is available for operating accessories such as an alternating current inverter 20 connected to standard receptacles 30, allowing the operation of household appliances such as razors, coffee makers, microwave ovens, alarm clocks, VCR's and so forth. Further 12 volt components and accessories such as parking lights, interior lights, television, CB radio, sound system, refrigerator, and like devices, not shown, are all commonly used and require power for operation. Should the power requirements be exceeded, due to peak draw devices such as a microwave oven or coffee maker, the existing truck batteries 38 will produce the necessary power by operating as a power sink.

In a most preferred embodiment, a single cylinder Kubota EL 300 AR engine capable of producing about four HP is coupled to a 12,000 BTU air conditioner compressor and a high output alternator 22 of about 120 amps on a 12 volt system. The size of the Kabota engine and the horizontal orientation of the cylinder allow the instant invention auxiliary power system 100 to be packaged into a small and lightweight add on device for the trucking industry. In an alternative embodiment, a Kubota EA 300 NB engine capable of producing about seven HP may be coupled to, or rotate an air conditioner compressor at a higher rate, so as to produce about 16,000 BTUs of air conditioning as well as simultaneously operate the high output alternator at reduced output. It is also contemplated that other engines having vertically oriented cylinders and/or a larger power output could also be utilized without departing from the scope of the invention.

Load management control is provided by the control relay/voltage regulator combination 24, 28. The preferred embodiment utilizes an externally mounted microprocessor controlled voltage regulator 28. The voltage regulator 28 is equipped with a reduced power setting, which is typically utilized to control alternator temperature in a marine environment. Such regulators are available from BALMAR Corp. of Arlington Va., model no. MC-612. The instant invention connects a relay 24 between the positive and negative terminals of the temperature circuit provided with the regulator 28. When the relay switch 24 is activated, the regulator 28 reduces the field current at the alternator 22. Within the instant invention the control relay 24 is activated during operation of the air conditioning compressor 12. Activation of the relay reduces the output of the alternator by approximately 50% to reduce the load on the auxiliary engine 10, thereby allowing a small engine to operate both systems simultaneously. As the air conditioner clutch disengages, control relay 24 also opens to allow higher electrical production by the alternator 22.

It should also be noted that other regulators or regulation methods, well known in the art, that are suitable for controlled reduction of alternator or generator electrical production in response to air conditioner compressor engagement may alternatively be utilized without departing from the scope of the instant invention.

Referring to FIG. 2, an alternative embodiment of the auxiliary power system is illustrated. In this embodiment the air conditioner compressor cooperates with an under bunk combination air conditioner and heater unit 32. In this embodiment the accumulator, expansion valve, evaporator, condenser and air conditioner controls are contained within the under bunk unit. Under bunk heat and air conditioner units for trucks are well known in the art.

Referring to FIG. 3, operation of heat system 106 is illustrated. During operation of the heat system, water used to cool the auxiliary engine 10 is circulated through a remotely mounted water to air heat exchanger 52 by opening of a water valve 54. The engine coolant is fluidly coupled 42 to the heat exchanger located in the evaporator/heater assembly 16 with an outlet 44 coupled to the radiator assembly 14 which is then circulated back to the engine 10 by the water pump 40. The evaporator/heater fan 17 may be turned on and used to draw air through or across the heat exchanger for increased warming of the truck interior. The electric radiator/condenser fan 26 cycles as required by the temperature switch 27 to reduce auxiliary engine temperatures. It should be noted that by operating the auxiliary engine at its' optimum RPM's and operating the alternator at approximately 80% of full electrical load draw, the engine is operated at its most fuel efficient level and provides a fast and reliable heat source for the sleeper area of the truck. The additional amperage draw may be used to power the parking lights, television, CB radio, refrigerator, AC inverter, interior lights and so forth necessary in cold weather operation. It has been found that a block heater provides a unique false load to the engine causing the engine to operate at peak efficiency. The block heater causing the engine temperature to reach its operating condition quickly while the additional load placed on the engine results quicker temperature increase. Further, the use of a water cooled alternator provides a means to recover heat for delivery to the cab.

Referring to FIGS. 1-3, general operation of the auxiliary power system will be described. Upon start up of the auxiliary engine 10, the oil pressure within the auxiliary engine is checked via oil pressure switch 20. If sufficient oil pressure is detected voltage is supplied to the auxiliary water pump 40 and relay 34. The auxiliary electrical system becomes active and current from the battery is allowed to flow through line 46 of regulator 28, and the alternator 22 begins to deliver electrical power to the battery 38. For operation of the auxiliary air conditioning system 102, relay 34 is closed to allow electrical current to flow to the air conditioning control 18. The air conditioner controls are manipulated by the operator, e.g. driver, to control the auxiliary heating system 106 and the auxiliary air conditioning. Should the operator desire air conditioning the air conditioning controls 18 are manipulated to cause the compressor 12 to engage the auxiliary engine 10. Simultaneously, the control relay 24 closes to cause the voltage regulator 28 to reduce the output of the alternator 22. The air conditioner control also selectively operates the evaporator/heater fan 17 and the condenser fan 26 as needed. A compressor clutch (not shown) remains engaged as long as the air conditioner pressure switch 48 is closed, causing the compressor to cycle on and off as required to achieve the air conditioning control setting.

Should the operator desire to operate the auxiliary heat system, the air conditioner controls are manipulated to open the water valve 54 and start the water pump 40. Water is then forced to flow through the heat exchanger 52 and optionally through the radiator 14 before returning to the auxiliary engine 10. For increased heat, the fan 17 may be operated to increase air flow over the heat exchanger. In this mode the control relay 24 generally remains open, allowing the alternator to produce electricity to its full potential.

For purposes of simplification this application has been directed to trucks although it would be obvious to one of ordinary skill in the art to recognize that the teachings of this patent and the associated claims may be directed to buses, boats, ambulances and so forth. Further, alternator changes to address higher voltage systems may be substituted throughout this specification and considered an obvious variation within the scope of the patent. It is to be understood that while I have illustrated and described certain forms of my invention, it is not to be limited to the specific forms or arrangement of parts herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.