Subject of Invention

[001] A subject of the present invention is a control device of an electronically controlled petrol internal combustion engine adapted for either petrol operation or optional gas operation, e.g. propane-butane mixture, earth gas, methane and the like.

Technical Problem

[002] A technical problem solved by the present invention is how to configure such control device of an electronically controlled petrol internal combustion engine that would allow - after a petrol engine has been transformed to be operated by optional gas - filling of cylinders with an equivalent quantity of gas equalling in energy to petrol as to any conditions of engine operation and driver's requirements, wherein said transformation should not entail changes in fundamental settings of engine operations, especially those defined in electronically controlled engines by digital mapping. Moreover, such device should not disturb or distort the operation of the original control unit and should also have favourable price and technical performance for adaptation of a small series of an individual vehicle type, even with a single vehicle of a type. It goes without saying that such device of the invention should not pose a problem to the use of petrol as fuel, wherein a switch-over from petrol to gas and vice versa should be user friendly as known with existing devices to be used with gas as fuel. The device of the invention should meet all safety requirements, regulations and standards. Prior Art

[003] Due to different energetic value of petrol and liquefied gas, the quantity of gas should be determined in the adaptation of the liquefied gas motor upon each filling of the cylinder with gas mixture in order to get as close as possible to the energetic value of petrol. In order to fill up the right quantity of gas upon each filling of the cylinder corresponding in its caloric value to a different quantity of petrol, the properties of selected gas as fuel should be taken into consideration. Attention should moreover be paid to the property of gas installation, especially the speed of opening and closing of injectors for a controlled supply of gas to a suction tube of the engine, pressure regulator and gas flow in gas vaporiser that converts liquefied gas kept in a gas bottle to gas in gaseous state with pre-set pressure.

[004] Known devices of this type are configured in a way that they entirely replace the original control device by taking the properties of gas into consideration. A problem of said devices lies in that they should be adapted in the sense of digital mapping and as to factory defined sensors for each type of vehicle separately, which is time consuming and expensive. Such device is therefore not market competitive for small series of an individual vehicle type.

[005] Further, yet another type of said control devices is known that assume values on various sensors on the engine from the original device. A new digital card in the supplemental control device takes these values into consideration and generates control parameters, as the beginning and time of opening of nozzles for gas injection into suction collectors, and the moment of ignition. Such configuration of a control device may be cheaper than the above mentioned, yet there still remains a problem of adaptation of such device for a small number of vehicles of the same type due to price issues. A disadvantage of such device lies in that the data contained therein generated by the original control device are processed as to its digital mapping and as a result control commands are created. This process needs one cycle in its microprocessor. As a result, a system error persists and is reflected in quick changes in the regime of engine operation, i.e. in accelerating or in ride uphill. The yield of the engine decreases in these situations.

[006] Adaptations of gas vehicles are supposed to be performed on purchased vehicles as second installation and should be performed by authorised car services. Each service workshop would therefore be expected to quickly adapt vehicles of numerous brands that are on the market for a market acceptable price and in a way that would be simple in logistics and technical aspect.

Solution to the Technical Problem

[007] The described technical problem is solved by the device of the invention, the essential characteristic lies in that it comprises an original control unit with digital mapping without any interventions therein and a new supplementary control unit that converts the control signal of the original control unit for the time the injector for gas supply is opened, namely by changing it by a correction constant depending on the properties of selected injectors for supplying gas to the suction channel. Correction constant determines that the energetic value of gas quantity in each supply to the suction channel equals the energetic value of the petrol quantity in equivalent supply as determined by the original control unit. This procedure is implemented within each control step of the original control unit that determines a control signal for the petrol injector and the original control unit does not detect any change or even disturbance or error in the use of gas as fuel. This is valid for each suction tact.

[008] Correction constant is determined on the basis of properties of selected gas injectors. Gas injectors must have a significantly larger flow than petrol injectors, since the volume of the energetic equivalent of gas with respect to the volume of petrol with the same energetic value is considerably higher. Due to larger construction of a gas injector and due to higher pressure appearing on the closing element within the injector, the time of opening from the closed state to entirely open state is considerably longer than the time of opening of a corresponding petrol injector. The speed of closing of the gas injector inconsiderably differs from the speed of closing of a petrol injector, since gas pressure on the closing element within the injector co-operates in closing. It can be understood that a gas injector with electronically controlled petrol engines is closed instantaneously. It can further be adopted that the petrol injector opens and closes instantaneously. Since a gas injector opens more slowly than a petrol injector, this fact should be taken into consideration when configuring a control signal for a gas injector. The remaining control parameters formed by a control unit, peripheral units (sensors and the like) and the belonging fittings remain original. Since no intervention is made into the digital card of the original control device, no knowledge thereof is needed when upgrading the device to be used with gas as fuel or when defining injectors for an individual vehicle or engine. This is of importance especially with vehicles that are rarely present in a certain region. As the tact of microprocessors is significantly higher than that of petrol internal combustion engines - which depends on the number of engine revolutions - the microprocessor of the original control device and that of the supplemental control device allow for a correction of the signal for the time of openness of injectors for gas always within the same microprocessor step. Each signal for the time of openness of gas injectors that is unambiguously defined based on the digital card and the sensor data is thus correctly corrected by a correction constant in compliance with all current data from the sensors and adequate point on the digital control card. This is possible due to the fact that the correction constant is predetermined for each type of injectors separately. To be able to set the energetic value of each injection of gas corresponding to the energetic value of each injection of petrol by the requirements of unchanged original control device, the gas pressure in the injector should be set manually. Gas is set on the vaporiser, which is a known solution. [009] The invention will now be described in more detail by way of an embodiment and the enclosed drawing, showing in

Fig. 1 schematic wiring diagram of the device of the invention adapted to petrol internal combustion engine;

Fig. 2 comparative time diagram of operation of a petrol and gas injector.

[0010] A control device 1 of an electronically controlled petrol internal combustion engine 2 adapted for alternate petrol and optional gas operation, e.g. a propane-butane mixture, earth gas or other gas, configured in a way that it comprises an unchanged original control unit 3 of the engine 2 in that no change is made in the original sensors 4 connected thereto, and a supplemental control unit 5 controlling gas injectors 6 based on the data from said original control unit 3, so that in each suction tact of said engine 2 filling of each cylinder is ensured with such quantity of gas that its energetic value equals the energetic value of the petrol quantity determined by the original control device 3 for the same suction tact.

[0011] The original control unit 3 is also foreseen as a constituent part of said control device 1 to provide for the same ignition control by transmitting high-voltage current to sparkling plugs 7 in the same moment as to main shafts, as foreseen by its original digital mapping.

[0012] The original control unit 3 as a constituent part of said control device 1 generates a signal for the beginning and duration of opening of injectors 6 for injecting gas into a suction collector 8 of said engine 2. This signal is determined on the basis of digital mapping within said device 3 and of data transmitted by sensors 4 on said engine 2 or on assemblies attached thereto. Said signal is led along conductor 9 to said supplemental control unit 5. Within the same microprocessor step of the original control device 3 the supplemental control unit 5 extends the time of opening of injectors 6 for the supply of gas to cylinders of said engine 1 by a correction time constant, wherein the time of start of opening of said injectors 6 remains the same as determined by the original control unit 2.

[0013] Correction constant is determined on the basis of adopted starting point, so that a petrol injector 6a opens and closes instantaneously, which is reflected in the diagram (Fig. 2). The openness of said injector 6a is shown as a rectangular field A, whereas a field B of said gas injector 6 is shaped like a trapeze due to a more slowly opening. The surfaces of fields A and B represent the quantity of petrol / gas of one injection. Since the time of opening of injectors 6 varies with respect to each state of the engine as defined by various sensors 4 and driver's requirements (steady driving, acceleration, driving uphill, driving downhill, etc.) and since the speed of opening of said gas injector 6 is constant, the correction constant must add to a signal for a various time period until full openness of said injector 6 always the same value for the tie of opening of said injectors 6. The correction for the time of closing of said gas injector 6 can be neglected as to the time of closing of said petrol injector 6a, since it practically has no influence on the control of said engine 2. Based on the above, it becomes evident that also a correction factor could be created for the time of closing of said injector 6, should it prove necessary.

[0014] Due to the fact that various types of petrol and gas that are used for fuel have various specific energetic value, the volume of the selected fuel must not change the energetic value of the quantity of fuel for one suction tact of the same cylinder and should remain the same as defined by the original contorl device 3. As the time of closing of said gas injector 6 is determined for said petrol injector 6a the energetic equivalent of a gas quantity should be set by setting gas pressure within the injector. This may be achieved by using a pressure regulator 9 on a gas vaporiser 10, which is known from prior art and is available on the market in several variants.

[0015] Said supplemental control unit 5 of the invention considerably contributes to the dropping of price of installation of entire device for liquefied gas drive (pressure vessel for liquefied gas, tube installations, valves, gas vaporises, etc.).

[0016] The switch over from the use of gas to petrol as fuel or vice versa is foreseen in a simple way by an electric switch, which may also be carried out during a ride. The switch-over for the alternate use of gas or petrol is performed by a switch 11 that conducts the signal for the control of said petrol injector 6a - when petrol is used as fuel - directly to each injector, wherein when gas is used as fuel, said switch 11 re-directs this signal to said supplemental control unit 5, which transforms the signal as described above and then controls said gas injectors 6. Said vaporiser 10 of liquefied gas, pressure vessel and other elements for the entire device are not described in detail and shown in figures, since they are taken from prior art and correspond to standards and safety requirements and it is assumed that they are known to a person skilled in the art.

[0017] When petrol is used as fuel, only said original control unit 2 with all auxiliary assemblies is used, as factory set. Said supplementary control unit 5 and the belonging gas injectors 6 are switched off. A switch-over from petrol to gas or vice versa may be carried out also during a ride without causing any disturbing or harmful effects on the engine or ride. This characteristic is known with known devices of this type as well.