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(11) | EP 1 256 714 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Starter system for an internal combustion engine through compressed air |
| (57) Concerns a starter system for an internal combustion engine, through compressed air,
to be used on vehicles. In particular, said system comprises a tank (1) of compressed
air, as well as a reversible group (2) which, besides being a starter, functions as
a compressor means for accumulating compressed air in the aforementioned tank (1). |
[0001] The present finding regards a system suitable for allowing the ignition of an internal combustion engine through compressed air.
[0002] It is known that petrol and diesel internal combustion engines are not capable of starting up without auxiliary devices once their movement members are shut down.
[0003] Therefore, a suitable device is necessary which makes them rotate at a sufficient speed, so that the carburation or the injection takes place in a sufficiently regular manner to allow the ignition of the engines themselves.
[0004] Regarding which, on small engines, for example of the marine type, for lawnmowers and the like, etc., manual lever or pull-cord operated devices are used.
[0005] Vice-versa vehicle propellants foresee the use of suitable electrical motors, fed from a battery, which force the engine into rotation through a pinion which engages on a toothed crown present on the engine flywheel. In fact the battery is always of the so-called lead-acid type. This battery, besides starting up the engine, is also used to feed the on-board services, in particular when the engine is shut down (emergency light, courtesy light, horn and the like).
[0006] Moreover, in many vehicles it is not possible, even with the engine started, to make determined apparatuses, typically of the electronic type, operate, in the case in which the storage battery is not present or at least is not operative.
[0007] The life-cycle of a normal lead-acid battery for starting up automobile engines is about 3-4 years.
[0008] Moreover, this duration has diminished since new productive technologies of expansion of the thin grids and of charging of the battery in container.
[0009] Therefore, such a storage battery has to be replaced about 4-5 times during the average life of a vehicle, with a substantial cost for the driver.
[0010] Moreover, such a storage battery fundamentally consists of materials which are toxic-poisonous (lead), as well corrosive (sulphuric acid), which determine a very high environmental cost.
[0011] Indeed, lead, due to its well known dangerous nature, is now eliminated from almost all products on the market under the form of tetraethyl lead and/or red lead (petrol, varnishes, etc.) and its use has undergone a substantial reduction as a heavy metal in other products (hunting bullets, fishing weights, wheel balancing lead, seals, etc.); indeed, it can be said that its consumption has practically concentrated almost exclusively upon the production of batteries.
[0012] In order to avoid that storage batteries with lead be abandoned once they have run out, with the consequent serious harm to the environment, organisations have been created in many countries throughout the world (COBAT in Italy) which have to take care of the collection and recycling of spent batteries with lead, making citizens which use them pay a tax, which is paid at the very act of buying the battery.
[0013] Another disadvantage of the lead-acid battery consists of its substantial weight, which goes against the requirements of vehicle designers, who try in all possible ways to lighten the overall mass of the vehicles themselves, to reduce the specific fuel consumption and therefore atmospheric pollution. Moreover, such batteries are never completely watertight (both with free acid technology, and with this technology combined with valve regulation); there is therefore the possibility that, particularly in the case of overturning of the vehicle, the corrosive sulphuric acid can spill out from the battery, causing corrosion by contact and environmental pollution.
[0014] Moreover, during the charging of batteries there is always a gas emission (typically hydrogen and oxygen), which transport significant amounts of sulphuric acid.
[0015] Another disadvantage of the lead-acid battery consists of the possibility of exploding in the case of internal constructive defects.
[0016] Indeed, precisely due to the fact that such a battery, during the charging step, emits a mixture of hydrogen and oxygen, which is highly explosive, a spark is sufficient, caused, for example, by a contact of a bad soldering of the inner electrodes, to cause an explosion.
[0017] The purpose of the present invention is that of foreseeing a compressed air starter system for vehicles with internal combustion engines, which is also capable of operating without a battery, which allows the drawbacks described above to be avoided.
[0018] This is obtained, according to the finding, by foreseeing on the vehicle the presence of a tank of compressed air, as well as a reversible group which, besides starting up the engine, is capable of functioning as compressor means capable of accumulating compressed air in the tank itself during the operation of the vehicle.
[0019] The finding, in its dependent claims, regards the particular configuration of the aforementioned reversible group, as well as some particular provisions suitable for making the system according to the finding more useful and efficient.
[0020] These and other characteristics of the finding shall now be described in detail, with reference to a particular embodiment thereof, given as a non-limiting example, with the help of the attached tables of drawings, where:
[0021] In fig.1 (Tav. 1) a principal schematic view of the starter system according to the finding is illustrated.
[0022] In figures 2 and 3 (Tav. II) a schematic view of the reversible group which functions as a compressor and as an engine/starter, respectively, used in the system according to the finding is illustrated.
[0023] In fig. 1 it can be seen that the system according to the finding foresees the presence of a tank 1 of compressed air, as well as an element 2 capable of functioning both as a starter element with air, and as a compression element for refilling the tank 2.
[0024] In fact, in the starting step of the engine such an element behaves precisely like a starter means, using the compressed air of the tank through the valve 3 controlled by the ignition key 4.
[0025] Such an element 2, with a starter function, locks through a pinion 4 to the sprocket 5 of the flywheel of the engine; the pinion 4 is moved by an air piston 6 controlled by a pneumatic valve 7; when the engine is started up the valves 3 and 7 deactivate and the pinion 4 unlocks from the sprocket 5 and the element 2, which functions as a starter, is intended to shut down.
[0026] In this situation of the engine in motion and the valves 3 and 7 at rest, the pinion 4 locks to a rotation reducer/inverter 8, which is connected to the drive shaft through a clutch 9 and begins functioning as a compressor inverting the motion to pump the compressed air into the tank.
[0027] The presence of a pressure limiting valve 10 is foreseen which avoids the formation of an overpressure in the tank, as well as energy wastage by the compressor.
[0028] The function of supplying the on-board services is carried out by a small specialised battery of the watertight type, for example of the Nickel-Metal-Hydrate type or of the Lithium Ions type (this type of battery is already used for some time in the field of mobile phones, as well as for supplying camcorders and the like).
[0030] This specialised battery which is made independent from the engine starter system allows the entire electrical unit of the vehicle to be redesigned at a substantially greater voltage than the usual 12 Volts (for example 24 or 48 Volts).
[0031] This not only allows a saving in volume and weight of the battery, but also a substantial saving in copper in the pipes, in the alternator, in the wiring, etc.
[0032] In particular, the Lithium Ions battery is small in size, light, watertight and much more environmentally friendly, since it contains absolutely no toxic-poisonous materials.
[0033] Its cost is finally reduced in a drastic manner, up to a price of about 2000 Italian Lire per cell in highly automated large-scale production (this production being a productive process similar to the production of electronic capacitors).
[0034] Going back to our unit it can be seen that, by turning the ignition key, the valve 3 is opened which connects the compressed air tank to the starter/compressor element 2, which in fact replaces the electric starter.
[0035] When the vehicle is in motion the element 2 pumps air into the tank through the aforementioned valve itself, actually refilling the air tank, until it reaches a maximum pressure level, in correspondence with which the pressure limiting valve 10 closes, preventing the further filling of the tank and thus reducing the stress of the air/compressor engine which rotates idle, without taking energy away from the internal combustion engine.
[0036] The size of the tank and the operation of the valve must guarantee an amount of air such as to be able to operate, with the vehicle shut down, more than one ignition, without discharging completely.
[0037] To guarantee to the air starter system a high specific energy and more ignitions, in particular in industrial vehicles, where a bottle tank could create encumbrance problems, the tank can be realised with a particular shape, so as to also satisfy a second function, for example linked to the passive safety of the vehicle.
[0038] For example, in a racing car or off-road car the tank can have the shape of a tubular frame of the roll-bar type.
[0039] Vive-versa in a road car the tank can have the shape of a front or rear bumper, according to the type of traction of the vehicle.
[0040] Through the present finding it is possible to innovate and improve all of three different functions of the automobile:
1) it is possible to eliminate the lead battery through the specialisation and separation of the starter function, which is carried out by the air/compressor starter means fed by the compressed air tank, from that for feeding the on-board services, which is carried out by a battery of the stationary low-power type with a higher voltage, buffered by a small alternator;
2) replacement of the electric starter with an air/compressor means which carries out the two functions described previously;
3) presence of a compressed air tank which, besides accumulating compressed air to guarantee more air ignitions, guarantees compressed air to turbocharge the internal combustion engine; moreover, in the case of a special configuration of the tank itself, it is capable of carrying out the passive safety functions quoted previously.
[0041] The advantages which derive from this are the following:
1) it is possible to eliminate the lead-acid battery, which allows all of the drawbacks well described previously to be avoided. To these are added the problems deriving from the lack of voltage at the on-board electronics during the change of battery, as well as from the instability of the voltage level during ignition with a battery.
2) The on-board electric unit is optimised thanks to the presence of a small watertight
battery of the stationary type, for example using Lithium Ions, susceptible to having
a higher voltage and a lower power, with the consequent substantial savings in copper.
In such a way, the problem of the instability of the voltage during battery ignition,
is avoided, a problem which is increasing in modern vehicles which are ever more equipped
with electric servomechanisms and electronic circuits, which require a much stabler
voltage.
As already quoted previously, in this way the problem of the lack of voltage during
the changing of the starter battery is solved.
3) Reduction of the weight of the vehicle with the consequent reduction in the specific consumption and in atmospheric pollution, with the same performance.
4) Increase in the reliability of the ignition at all temperatures and in the most
demanding situations. In fact, the air starter system is not just simpler, comprising
less moving parts and being less subject to the negative influences due to the change
in exterior atmospheric conditions (variation of temperature, humidity, etc.), but
extraordinary intervention in the case of complete draining of the energy reserve
is also less demanding.
Indeed, currently, when the battery is completely dead, it is necessary to replace
it or, possibly, recharge it; vice-versa in the case in which there is no air reserve
in the tank one only has to connect up to a compressor which is present in all petrol
stations.
5) Increase in the specific power of the engine, with all of the advantages of a lower
weight/power ratio.
In short, the air/compressor engine device is capable of carrying out the following
functions simultaneously:
a) when the engine is shut off it functions as a compressed air starter actuated by the compressed air coming from the tank through the inlet valve;
b) when the engine is in motion it functions as a compressor, which pumps compressed air into the tank through the outlet valve.
[0042] Vice-versa the tank of compressed air is capable of carrying out the following functions:
a) supplying compressed air to the air/compressor engine device during ignition;
b) supplying compressed air for turbocharging the internal combustion engine;
c) having a shape such as not to create encumbrance in the engine bay and to contribute, simultaneously, to increasing the passive safety of the passengers through the replacement of one of the bumpers or else as a roll-bar;
d) the tank is also possibly capable of supplying compressed air to other possible on-board equipment (pneumatic horns, etc...)
[0043] As far as specifically concerns element 2, capable of functioning as a compressor (fig. 2), when it turns in one direction, and as an air engine/starter (fig. 3), when it turns in the opposite direction, in a preferential embodiment it is based upon the operating principle of the rotational volumetric compressor which is self-lubricated thanks to the presence of graphite blades.
[0044] It comprises a stator 13, inside of which an eccentric rotor 14 is arranged. The rotor has three or more blades 15 which protrude radially and adhere to the stator biased by opposite radial springs 16.
[0045] On the stator two pipes 17 and 18 are formed which function, alternatively, as an air intake and output pipe, respectively.
[0046] When the device functions as a starter (fig. 3) the air enters from the pipe 18, making the blades 15 move, which adhere to the stator 13 biased by the radial springs, thus making the rotor rotate; the air is intended to decompress and then come out from the pipe 17.
[0047] Vice-versa when the device 2 functions as a compressor (fig. 2) the air is taken in by the pipe 17 and then is trapped and compressed, with the blades 15 which adhere to the stator 13 biased not just by the radial springs 16, but also by centrifugal force.
[0049] In fact, the difference of such a device with respect to normal bladed rotational volumetric compressors consists precisely of its reversibility, that is of its possibility of functioning, by inverting the motion, both as a compressor, and as an engine. This is obtained by ensuring that the blades adhere to the stator also when it is halted, using the radial springs themselves.