WO2003064202A1

WO2003064202A1 - Auxiliary power units for automotive vehicles

Info

Publication number: WO2003064202A1
Application number: PCT/AU2003/000095
Authority: WO
Inventors: Graham Harry Fountain; Paul Francis Kasperowicz; Clive Andrew Hawkins
Original assignee: Cmc Power Systems Limited
Priority date: 2002-02-01
Filing date: 2003-01-31
Publication date: 2003-08-07
Also published as: AUPS025402A0

Abstract

An auxiliary engine (1) for an automotive vehicle (25) having a main engine (30), the auxiliary engine (1) being of a type having at least one set of opposed, aligned cylinders and associated pistons which are linked to an output shaft so that the pistons of the set reciprocate together always in the same instantaneous direction without relative movement between the pistons. The auxiliary engine (1) coupled to a generator for providing the substantive electrical power requirements of the vehicle, and wherein the auxiliary engine is mechanically separated from the main engine.

Description

AUXILIARY POWER UNITS FOR AUTOMOTIVE VEHICLES

TECHNICAL FIELD

The present invention relates to the adaptation of an auxiliary engine completely detached mechanically from the main (prime) engine, for an automotive vehicle and more particularly to an auxiliary engine that forms part of an auxiliary power unit, also comprising a generator and associated electronic control system, for generation of all or part of the electrical energy required for the vehicle.

BACKGROUND

The average electrical load in automobiles is expected to increase by nearly 50% over the period from 1996 to 2005 to an estimated 3 to 7kW. The sum of the power requirements of all electrical equipment when switched on at the same time is expected to increase from 8,750W to more than 13,400W over the same period. The total length of the electrical cables in a modern automobile is about 3km and has a weight of more than 40kg. The generation of electrical power currently adds more than 1.51/100km on average to the overall fuel consumption of a passenger car.

Current automotive electrical systems are nominally 12 Volts, but in practice the voltage level is nearer to 14 Volts and it is this latter voltage that will be referred to in subsequent discussion herein.

There is a proposed increase in voltage level from the current 14 Volts to 42 Volts. This would lead to an increased efficiency of the generator and would allow either the use of thinner wiring or the reduction of electrical transmission losses in the wiring. New technologies such as electrically actuated valves, electric brakes etc. represent high electrical loads, which are difficult to satisfy with a 14 Volt system but become feasible with a 42 Volt system. The proposed changeover from a 14 to 42 Volt system may require a dual system for a while, because not all electrical components will immediately be available for 42 Volt operation.

Conventional electrical power generation systems for on-board generation of electrical power use a generator driven by the engine of the vehicle via a belt drive. However, there are significant limits as to the ability of these conventional generator systems to meet the expected increasing electrical power requirements. An increase of electrical output is difficult to achieve and the efficiency is problematic because of the continuously changing generator speed. For a stop/start operation of the engine while the vehicle is stationary, the battery capacity has to be high and the durability of conventional starter motors for such an application is not sufficient.

Recently introduced flywheel starter/generator systems are optimal in regards to frequent engine stop/starts and the noise level during engine starts is low. However, the overall efficiency is a problem because the generator cannot be designed to give good efficiency at all speeds between 600 and 6,000 rpm. In addition, part of the space gained by the elimination of belt driven auxiliary components, is used up by the flywheel generator.

A number of auxiliary engine arrangements for use in vehicles are known. German Patent Application No. 2917140 in the name Luk Lamellen and Kupplungsbau GmbH, describes a motor vehicle having an auxiliary engine mechanically connected to the main engine via a clutch mechanism. The main engine is operated when it has to output power but is stopped at other times to save fuel. The auxiliary engine is used to power secondary systems such as steering and brakes when the main engine is stopped, and both engines are used at some stage to drive the wheels of the vehicle. A flywheel arrangement is used to restart the main engine.

German Patent Application No. 4204261 in the name of Bayern Motoren Werke AG describes a vehicle having an electric motor as its main power unit and an auxiliary engine is coupled thereto via a clutch mechanism. The auxiliary engine is switched off during city driving and the electric motor is used to drive the vehicle.

WO 93/07016 in the name of Mannesmann AG describes a vehicle in which electric generators are connected to direct drive the vehicle. A series of engines in parallel, or a multicylinder engine divided into a number of smaller engines is used. Each engine is associated with its own generator. All the engines are operated independently but are used to share functions including vehicle drive.

WO 00/29241 in the name of Robert Bosch GmbH describes a vehicle having a main engine and an auxiliary engine interconnected via a clutch mechanism. In this arrangement, the auxiliary engine drives a shaft that drives the air conditioning unit and a generator. This requires the auxiliary engine to run at a speed suitable for the air conditioning unit and requires the auxiliary engine to be in close proximity to both the main engine and the air conditioning unit.

A number of disadvantages exist with all these abovementioned prior art arrangements. Firstly, where the main engine and auxiliary engine are connected via a clutch mechanism or other mechanical device there are complex size, packaging and weight considerations, as well as the physical requirement that the auxiliary engine be adjacent and in a specific relationship to the prime engine. This is a considerable drawback and can result in severe restrictions in vehicle design. Secondly, where the auxiliary engine has a dual function of vehicle drive and powering of secondary systems, it is difficult to optimise the output of the auxiliary engine to suit the power needs.

The present invention seeks to overcome the abovementioned disadvantages by providing an auxiliary engine that is mechanically separated from the main engine, is adapted to drive a generator for providing the substantive power requirements of the vehicle and as a result of its mechanical separation from the main engine may be located in any suitable location within the vehicle, including locations remote from the main engine bay.

We have determined that a solution to the problem of increasing power requirements can be achieved by the incorporation into the vehicle of an independently driven auxiliary engine or auxiliary power unit (APU) to generate all of the electrical power required for operation of the vehicle. Although APUs consisting of an internal combustion engine driving a generator are available for a wide range of power generating applications, we have determined that very specific criteria need to be met to enable successful incorporation into an automotive vehicle. Basically, it is necessary that the engine of the APU have a good mechanical efficiency, low vibration, low engine exhaust emissions, and a low noise register. Another criterion is the "package" size or envelope of the APU and we have determined that the package volume or envelope should not exceed approximately 50 litres for a typical car, although a greater envelope may be acceptable for larger vehicles such as buses where space considerations may not be as critical.

Over the past hundred years or so, many different types and configuration of internal combustion engine have been proposed. However, the inability of most currently available engines to meet the criteria identified above would lead to the general conclusion that an APU is not a particularly viable approach to increased power generation and that the use of an engine driven generator still remains the only viable option. There is also an inherent prejudice against the use of an APU as the use of an additional engine just for power generation in an automotive vehicle would seem to represent an expensive option and as such can be excluded from consideration.

The applicants have determined that an APU with an engine configuration of specific type, all of the criteria specified above can be met including package size and dimensions. Further, the applicants have determined that the overall effects of such an APU incorporated into the vehicle provides benefits in terms of the operation of the overall vehicle to such an extent that the APU is able to provide a very competitive means of effecting power generation and provides advantages which other systems are unable to offer.

SUMMARY OF INVENTION

According to a first aspect the present invention consists in an auxiliary engine for an automotive vehicle having a main engine, said auxiliary engine being of a type having at least one set of opposed, aligned cylinders and associated pistons which are linked to an output shaft so that the pistons of the set reciprocate together always in the same instantaneous direction without relative movement between the pistons, said auxiliary engine coupled to a generator for providing the substantive electrical power requirements of the vehicle, and wherein said auxiliary engine is mechanically separated from said main engine.

Preferably said auxiliary engine is mechanically separated from components of said vehicle operably receiving electrical power from said generator.

Preferably said auxiliary engine is adapted to run at a predetermined constant speed.

Preferably said generator is a permanent magnet generator.

Preferably said generator can also act as a starter motor for said main engine.

In one embodiment a power management system rectifies and controls the generator output to 42V DC.

In another embodiment a power management system rectifies and controls the generator output and is able to run at least two voltage systems. Preferably said at least two voltage systems are nominally 14V and 42V.

Advantageously, the auxiliary engine is in accordance with one or both of EP patents 0516727 and 0599915.

In a preferred embodiment of the invention, the opposed cylinders are horizontally directed and the rotor of the generator is coupled directly to the output shaft of the engine. It is to be understood that the engine defined above is not a conventional horizontally opposed two- cylinder engine in which the phase relationship between the two pistons is such that there is relative movement between the two pistons within the engine cycle. Instead, in the engine defined above the two pistons are essentially rigidly coupled to form a single reciprocating mass.

When the APU is used in a typical passenger car, the engine will have only a single set of opposed cylinders, in other words a two-cylinder engine. This will enable adequate power generation within an acceptable package volume. However, for larger vehicles, such as buses, having greater electrical power requirements, an engine with two sets of opposed cylinders (a four-cylinder engine) may be required; although this will lead to a larger package volume, the available space within a vehicle of that type will tolerate this. It is also possible that for larger vehicles, more than one set of the two-cylinder engine each with individual generators can be used and located in separate locations on the vehicle.

The engine may be spark ignited gasoline, kerosene, LPG, CNG or compression ignition diesel powered.

According to a second aspect the present invention consists in an automotive vehicle having a main engine and an auxiliary engine, said auxiliary engine being of a type having at least one set of opposed, aligned cylinders and associated pistons which are linked to an output shaft so that the pistons of the set reciprocate together always in the same instantaneous direction without relative movement between the pistons, said auxiliary engine coupled to a generator for providing the substantive electrical power requirements of the vehicle, and wherein said auxiliary engine is mechanically separated from said main engine.

Advantageously, one or more of the following systems of the main engine and auxiliary engine of the APU can be shared: fuel supply, cooling, lubrication, combustion air supply, and exhaust. BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which: -

Figure 1 is a perspective view showing an auxiliary engine in accordance with the preferred embodiment of the invention;

Figure 2 is a cut-away view showing schematically certain of the principal components of the engine;

Figures 3 and 4 show schematically the principal working components of the engine with the cylinders and crank case omitted.

Figure 5 a and 5b show schematic plan and elevation views of the package envelope of the auxiliary and generator shown in Figure 1.

Figure 6 is a schematic view of a vehicle fitted with the auxiliary engine of Figure 1.

MODEOFCARRYING OUTTHEINVENTION

In the preferred embodiment of the invention, an auxiliary power unit (APU) comprises a two- cylinder engine, in accordance with a design of the present applicants to which the applicants refer as a CMC Sytec engine and is either a gasoline, kerosene, LPG, CNG or diesel fuelled engine. This engine is in accordance with one or more of the following patents and the full disclosure of which is hereby incorporated by reference: EP 0516727 and EP 0599915.

A two-cylinder auxiliary engine of the design specified above with a capacity of around 500cc is expected to be the optimal size for most automotive applications envisaged. A separate APU having a Sytec engine as specified above, a generator and an associated electronic control (or power management) system overcomes many of the disadvantages of other systems as will be discussed in detail subsequently. It is able to generate electrical power very efficiently and provides significant advantages in comparison to other systems. The proposed Sytec APU system does not necessitate any significant design changes to the vehicle and therefore its incorporation into vehicles provides an efficient cost effective and flexible option at least for the short to medium term even if fuel cell technology is able to be developed sufficiently to provide a satisfactory cost effective solution for auxiliary power generation in the future. The mechanically separated auxiliary engine also allows for greater flexibility in the design of new vehicles, whereby allowing smaller main engine bay volumes and the opportunity to design the integration of the auxiliary engine /generator in the most efficient manner into the vehicle. Figures 1-6 show the preferred layout of a two-cylinder auxiliary engine 1 and associated generator 8 driven thereby, that along with power management system 31 form an APU. The two cylinder casings engine 1 are designated 2,4 and extend from a main casing 6 that mounts the crankshaft that forms the output shaft, and the camshaft. Generator 8 is mounted to one end of the main casing 6, with the rotor of generator 8 being directly coupled to the output shaft. Preferably generator 8 is a permanent magnet generator although other forms of generator should also be suitable. The generator 8 will also act as a starter motor for the engine 1 of the APU.

The basic construction of the engine 1 is shown schematically in Figures 2 to 4 that show the opposed pistons 10 rigidly interconnected via a rigid yolk structure 12 by which the pistons 10 are also coupled to the single crank pin 14a of the crankshaft 14. The camshaft for operating the valves of each cylinder is shown at 16. Substantive balancing of the engine 1 is effected by a counterbalancing shaft assembly shown at 18 which rotates in opposition to the rotation of the crankshaft 14, the counterbalancing shaft assembly 18, crankshaft 14 and camshaft 16 being coupled via a chain or belt drive system 20. The yolk structure 12 and the associated lubrication system are described in detail in the aforesaid EP patents, as are other aspects of the engine 1. For the present application, the lubrication system may operate with a dry sump.

Figure 6 depicts a schematic of a passenger vehicle 25 having a main engine 30 for driving the wheels thereof. Vehicle 25 is also fitted with an auxiliary engine 1, as described earlier, "mechanically separated" and remotely located from main engine 30. The term "mechanically separated" as used herein means that there is no mechanical linkage device such as a clutch mechanism or other rotary coupling device connecting auxiliary engine 1 to main engine 30. Auxiliary engine 1 is coupled to generator 8 that delivers its output to power management system 31. The various electrical systems designated 32, such as air-conditioning compressors, water- pumps, valve trains, brakes etc are supplied with electrical power from power management system 31. In an embodiment where the vehicle is running at least two voltage systems, say 14V and 42V, the power management system 31 is adapted to rectify and control the output voltages delivered to the electrical systems 32.

A detailed discussion concerning the benefits of the proposed Sytec APU system, comprising auxiliary engine 1, generator 8 and power management system 31 of the abovementioned embodiment, in comparison with more conventional power generation systems will now be described in detail in relation to a number of different factors.

Changeover from 14 to 42 Volt system

Some automotive components currently available for 14V will take some time to be converted from 42V. Also, technical reasons may suggest not changing specific components to the higher voltage. If both voltages are available, the most cost-effective solution can be chosen for each system. For a generator driven by a separate auxiliary combustion engine, the cost penalty for providing electrical power at both voltage levels for a transition time, or even infinitely, is not large. Significant amounts of energy have only to be available to start the small auxiliary engine 1, but this is considerably less than the energy needed to start the prime (main) engine and can be achieved with 14V as well as 42V, and accordingly other priorities may dictate the use of a 14V or a 42V battery. Besides enabling starting of the auxiliary engine, the battery storage may also be required to avoid frequent start/stop operation of the auxiliary engine, when only a low level of electrical power is required. The components that have to be operated during the switch off times of the generator, for example parking lights, have to be designed for the available battery voltage level.

Efficiency

In conventional main-engine-driven generator systems, all systems mechanically coupled to the engine have to be continuously accelerated and decelerated in accordance with the driver's driving requirements. Energy stored in the rotation of auxiliary components is lost once the component's rotational speed is reduced again. These acceleration losses are small only in the rare situation of cruising with constant speed with nearly constant engine speed.

Even if only slow changes of the rotational speed of the engine, and therefore of the connected auxiliary systems, take place, the generator has to generate power over a very wide speed range. In a 6-cylinder engine the crankshaft speed spans the range from 600 rpm up to 6,000 rpm and more. In a conventional system with a 1.0 to 2.5 transmission ratio the generator has to run between 1,500 and 15,000 rpm, and flywheel generators run directly at engine speed. A vehicle engine runs at idle 5 to 1% of the total operating time. Main-engine-driven generators are designed to supply enough electrical power during extended idling periods to satisfy high power consumers such as window heaters, lighting and fans. Therefore the generator has to be optimised for low speeds, thereby reducing the efficiency achievable at high generator speed. Current design generators achieve an average of 50% efficiency with a maximum of only 55% at low engine/generator speed, reducing to below 30% at high speed.

With a suitable electrical power supply, many functions of a vehicle can be achieved electrically, while currently they need components to be installed close to the engine as they are reliant on a mechanical driving connection to the engine. Electrical air-conditioning compressors, water- pumps, valve-trains and electrically controlled vehicle brakes are already in production or at prototype stage. Generators driven at optimum speed for the output required can achieve more than 80% efficiency. A separate APU is independent from the driver's requirements, controlled only by electrical power demand and the battery power storage level. When the generator runs, it runs exactly at the speed for which it has been designed and at which it converts mechanical to electrical power most efficiently. The APU combustion engine itself too can always be run at exactly the operating conditions under which it converts fuel energy into mechanical energy most efficiently. It is not controlled by the priority of the vehicle's driving requirements.

For an output of, say, 1,850W required on a typical rainy winter's day with heating fan, A C, lights, windscreen wipers, rear window heater operating and power needed for the control of engine and transmission, the mechanical generator input is 3.7kW with an average generator efficiency of 50%. A modern 3.0 litre 6-cylinder main engine needs about 1.51/h fuel at idle and an average of 850 g/kWh of fuel under these low part-load conditions. This represents a total fuel consumption of 4.25 litres of petrol per hour. For a typical 4-cylinder 2.0 litre engine the fuel consumption is about 1.0 to 1.21/h at idle and 600 g/kWh or 3.0 litre per hour at 2,000 rpm and a load of 1.1 bar.

With an independent APU in accordance with the present, the generator speed is optimised and 80% efficiency can be achieved. For a mechanical output of the 2.3kW required for the same condition and the specific fuel consumption close to the auxiliary engine's optimum operating conditions of about 300 g kWh, the consumption is only 0.94 litres of fuel, at least 0.8 or 1.3 1/h respectively less than with the main engine generator, a considerable advantage for the environment and the driver over time. Additional consumption and emissions reductions are achieved because auxiliary equipment does not have to be accelerated and decelerated needlessly together with the main drive engine.

Stop/start operation of the main engine in an APU-equipped vehicle is better than that when conventional generator systems are applied because during starting and idling the main engine has to overcome only its own internal losses, not the power requirements and losses of any connected auxiliary systems. The idle fuel consumption can also be reduced considerably.

Weight and weight distribution

An auxiliary engine, even though it is only small, represents a weight penalty. However, nearly half of the weight of the auxiliary engine 1, estimated to be in the 30 to 35 kg range, can be offset by the use of a smaller battery as this only needs to be sufficient to start the small auxiliary engine and also to power low demand equipment such as parking lights. The replacement of belts, pulleys and brackets necessary for a mechanical operation by the main engine by electric motors will be weight neutral, and the possible use of light rare earth magnet motors even has the potential of a weight saving. As important as the weight is the potential to improve the weight distribution in the car. This has a direct influence on the driveability and therefore safety of the vehicle. While conventional systems have to be located close to the already heavy concentration of mass of the engine and transmission assembly, there is much greater flexibility in the positioning of the present APU, and it may be located in any suitable location within the vehicle, including locations remote from the prime engine. The difficult task of tuning a car's suspension for neutral or near-neutral steering characteristics is made easier.

Battery capacity

With the main engine of a vehicle switched off, conventional generator or flywheel starter/generator systems do not allow electrical operation of equipment with high power requirements like air-conditioning, defrosting and defogging of windows, high or fog beams or continued operation of an electric water-pump and heater fan to maintain cabin heating until the cooling system has cooled down. Even the use of low power equipment is limited, because a sufficient amount of energy has always to be retained to be able to restart the car engine when required. The battery capacity, and therefore the battery's weight and size, has to be made as large as possible. Extended periods of idling in, for example, traffic jams may cause problems for the charge condition of the battery even when the engine is running.

With a separate engine driven APU these problems do not exist. The energy balance of the vehicle does not depend on the main engine at all. As the APU is able to supply the short-term high power required for the starting of the main engine, the main engine can be switched off during longer stops while air-conditioning, heating, fans and water-pumps continue to work by being powered by the APU. The cooling circuit of the small auxiliary engine is able to provide ongoing heat to maintain the cabin temperature for longer. If only little electrical power is required, the APU engine can be switched off until the battery has to be recharged. Because of the small size and the mechanical efficiency of the APU engine the energy needed to restart it through its generator is small. Therefore only a rather small storage battery is required to maintain the operation of parking lights and other essential functions for a certain time. Once this small battery is discharged to a certain limit, the generator, operating as starter, can automatically restart the APU, provide the operating systems with power and recharge the battery. The battery capacity has to be optimised to prevent too frequent starts and stops. This not energy efficient and could cause increased emissions. Pauses between engine running periods should not be too long, because this would cool the engine down too far, causing more emissions during the next start.

Packaging

The current market pressure to increase the space available in the cabin without increasing the outer dimensions of the vehicle has put increased constraint on car designers to enable the packaging of systems into the vehicle. The engine with all necessary attachments requires so much room that it is difficult to design an acceptable bonnet shape around it. Engine compartments in cars are today loaded with components to a degree that the required flow of fresh air is not always ensured.

A separate APU eliminates the need to mount some current belt-driven equipment around the engine, and much of this equipment can be moved to other areas that are not currently occupied such as spaces under seats, in front of or behind wheels, above the rear wheels, below the boot. Engine-mounted components, especially the generator, water and power-steering pumps, the air- conditioning compressor and the drive belts and pulleys, increase the overall size of the drive engine. This causes problems for vehicle designers, crash safety engineers and engineers responsible for the thermal balance in the engine compartment.

A Sytec engine having an inherently low profile and shorter in length than equivalent conventional reciprocating engines has the advantages of being able to be more conveniently packaged in remote locations either inside or outside the engine bay.

Because all of the main engine's power is available to accelerate the car, its capacity can be reduced while maintaining the same driving performance. This reduces the outer dimensions of the main engine even further and offsets the added weight of the auxiliary power unit.

While there is the additional space and weight for the APU to be considered, its location could be in many different locations in the vehicle. A 500cm³ two-cylinder Sytec engine is perfectly balanced, is very compact and can be positioned remotely from the main engine or incorporated along side the main engine in the engine compartment. Combined with the generator the dimensions are not larger than shown in the layout of Figures 5a and 5b that represents a box volume of only about 50 litres. The space requirement for the battery of a well-equipped car is about 25 litres. This engine can easily supply the 5kW currently required, at a nominal engine speed of 1,800 rpm. Should the power requirements grow as anticipated, the engine speed can be raised to cover any additional higher output level.

Cost implications

The production manufacturing cost for a the overall combustion-engine-driven APU of the type comprising auxiliary engine 1, generator 8 and power management system 31 of the abovementioned embodiment will be in line with other alternatives when consideration is given to the optimised main engine and the subsequent replacement of many of the existing systems, such water-pumps and other bet driven equipment. The generator 8 of an APU is similar in cost to that required for a flywheel generator and cheaper than a belt driven generator with pulleys, brackets and the belt. The use of perfectly balanced engines based on CMC's Sytec system reduces the requirements for dampening material and complicated and expensive engine mounts. This latter issue enables the Sytec auxiliary engine 1 to be more efficiently mounted with less supporting structure around the main vehicle chassis. Dependent on the installation conditions some of the components of the auxiliary engine and the main drive engine can be combined to achieve weight, space and cost reductions or functional objectives. The air for the small auxiliary engine of the APU can be supplied through the main air filter, the exhaust gases may be led through parts of the main exhaust system, although a separate catalytic converter may be required for the small auxiliary engine. The main fuel tank can supply both engines with fuel and even the oil reservoir for the auxiliary engine's dry sump system could be the main engine oil sump. The cooling systems of the auxiliary and main engines could be combined to allow preheating the main engine and heating of the passenger cabin by the heated coolant of the auxiliary engine. Even the electronic control of the APU system can be combined with the main ECU. This allows sharing of sensors and will further reduce costs. Electrically driven pumps and compressors are currently still more expensive to manufacture than mechanically driven auxiliary systems, with increased production volume these cost differences will be reduced. Table 1 shows a list of the main components influenced by the application of a conventional belt driven generator, a flywheel starter/generator, or the separate APU.

Initially the separate APU system is expected to carry a cost penalty, but this is partly offset by the additional functions it offers, which cannot be achieved with the alternative solutions. The cost penalty will reduce with growing market penetration.

Table 1: Main components influenced by the type of power generating system

Emissions

Although the engine driven APU creates its own exhaust emissions, the overall emissions of the vehicle will be reduced. This follows the reduced fuel consumption because of reduced losses in the main engine and because auxiliaries like the power steering and air conditioning only use energy when they are required to run. No mechanical transmission losses occur. The electrical transmission losses with a 42 Volt system will also be reduced. The APU engine may require its own catalytic converter, to ensure it heats up and becomes operational quickly. However this is dependent on the specific vehicle installation and emissions legislation. For noise reduction and further omissions conversion the exhaust pipe should be integrated into the main exhaust system upstream of its main catalyst. The exhaust gas of the APU engine then preheats it, with the potential to reduce harmful main engine emissions after start-up. The availability of sufficient electrical energy also allows the application of electrical catalytic converter heating, which reduces the time the catalyst needs to achieve a high conversion efficiency. Idle emissions of the main engine are also reduced when it does not have to operate any auxiliary equipment.

Noise, vibration and harshness (NVFD

Belt noise contributes considerably to the overall engine noise. Elimination of the auxiliary drive belts of the main engine is expected to offset the noise emitted by the additional auxiliary drive electric motors. The engine noise and vibration levels of the APU can be kept very low with the application of a perfectly balanced Sytec engine with harmonic piston motion. If a conventional engine were utilised as power source for the APU, it would require additional noise and vibration reduction measures. If the exhaust system of the APU engine is combined with the main system, sufficiently low exhaust noise levels should be achievable. Some attention is required for the intake and the combustion noise, however as the auxiliary engine 1 of the abovementioned embodiment is designed to run at a single optimum speed, noise and vibration levels can be minimised.

Additional functions only possible with the separate APU

Because of the independence of the APU from the operation of the main engine there is the opportunity to include additional functions, which cannot be achieved with conventional systems.

- Emergency engine start

A small engine of the capacity required for an APU can easily be started manually, if suitable starting equipment is provided. The superior mechanical efficiency of the Sytec engine reduces the energy required on starting.

This eliminates the possibility to be stranded with a flat battery, requiring outside help as if the starter battery for some reason has not enough energy left to start the APU, the start can be done manually as an emergency measure. The APU then in turn provides enough power to start the main engine. The problematic situation of the need for outside help when the battery is flat in a vehicle with automatic transmission, which cannot be push started, cannot occur because power for the main engine start can always be generated.

- Extended operation of additional equipment in the stationary car

TV's, DVD's computers, refrigerators and other types of electrical loads can be operated for extended periods without problems. The APU switches on and recharges the battery before it runs flat. This is especially important for sports utility vehicles (SUVs), "people movers" or campervans, and also for normal passenger cars. Special purpose vehicles with heating or cooling requirements do not need additional equipment to enable extended periods of stationary operation.

- Air-conditioning and heating in the stationary car

If the cooling system of both engines is combined, the heat energy produced by the small APU engine can be utilised to heat the vehicle cabin without the main engine running. The electrical power can drive the air-conditioning compressor in the stationary car for extended periods.

- Preheating orprecooling the car before the main engine is started

Controlled by a timer or even by mobile phone it is possible to start the heating or cooling system to control the cabin temperature to a comfortable level. In winter, a wear and emissions reducing side benefit is the heating up of the cooling circuit of the main engine. This not only reduces possible starting problems at very low temperatures, it also improves safety by providing clear windows and a smooth after-start operation of the main engine.

In conclusion, the use of a separate APU facilitates the difficult transition from 14V to 42V electrical systems in passenger vehicles, and enables the provision of additional vehicle functions, which are not currently available. High levels of electrical power requirements currently need the main engine to operate to provide sufficient energy; this applies not only with a conventional belt driven generator, which already has reached its limits and cannot be extended much further for higher output, but also with a flywheel starter/generator system, if the battery capacity is not increased considerably. Varying generator speeds reduce the achievable conversion efficiency.

The separate APU, achieves the best fuel efficiency, lowest emissions and greatest freedom for additional functions. It can also be seen as an intermediate step for a hybrid system, where all but the basic propulsion function of the vehicle is done independently from the main engine. The provision of a durable and quiet main engine starting system would allow stop/start operation of the main engine, resulting in additional fuel consumption and emission reductions.

The embodiments have been described by way of example only and modifications are possible within the scope of the invention.

The term "comprising" (and its grammatical variations) as used herein is used in the inclusive sense of "having" or "including" and not in the exclusive sense of "consisting only of.

Claims

1. An auxiliary engine for an automotive vehicle having a main engine, said auxiliary engine being of a type having at least one set of opposed, aligned cylinders and associated pistons which are linked to an output shaft so that the pistons of the set reciprocate together always in the same instantaneous direction without relative movement between the pistons, said auxiliary engine coupled to a generator for providing the substantive electrical power requirements of the vehicle, and wherein said auxiliary engine is mechanically separated from said main engine.

2. An auxiliary engine as claimed in claim 1, wherein said auxiliary engine is mechanically separated from components of said vehicle operably receiving electrical power from said generator.

3. An auxiliary engine as claimed in claim 1, wherein said auxiliary engine is adapted to run at as a predetermined constant speed.

4. An auxiliary engine as claimed in claim 1, wherein the generator is a permanent magnet generator.

5. An auxiliary engine as claimed in claim 1, wherein said generator can also act as a starter motor for said main engine.

6. An auxiliary engine as claimed in claim 1, wherein a power management system rectifies and controls said generator output to 42V DC

7. An auxiliary engine as claimed in claim 1, wherein a power management system rectifies and controls said generator output and is able to run at least two voltage systems.

8. An auxiliary engine as claimed in claim 7, wherein said at least two voltage systems are nominally 14V and 42V.

9. An automotive vehicle having a main engine and an auxiliary engine, said auxiliary engine being of a type having at least one set of opposed, aligned cylinders and associated pistons which are linked to an output shaft so that the pistons of the set reciprocate together always in the same instantaneous direction without relative movement between the pistons, said auxiliary engine coupled to a generator for providing the substantive electrical power requirements of the vehicle, and wherein said auxiliary engine is mechanically separated from said main engine.