Field of the Invention

The invention relates to a fuel injection system for feeding the fuel into an internal combustion engine comprising a volumetric pump of continuous feeding, one or more overpressure activated injection valves and control valves.

It is known that the characteristics of the fuel injection systems are determined by way of feeding.

Prior Art

In the petrol engines used solutions comprising electromagnetically controlled injection valve fed with constant pressure, for example the volumetric flow rate of the injection is determined by the feed pressure of the fuel, while the actual time and period of the injection is determined by the time, when the control valve opens, and by the period, when the control valve connected in series with the jet nozzle of the carburettor is being opened.

Such kind of solutions can be known from US-PS 4.156.560 as well as from the publication document EPA-O 243 871. The common advantage of the mentioned solutions is in that the features of the injections, i.e. period and actual time of the injection , the penetration depth, drop size, etc. are independent from the speed of rotation of the engine and can be exactly controlled.

Their disadvantage, however is in that due to the constant feed pressure the injection valves can leak, so by this construction in practice only low feed pressure could be realized.

The diesel engines comprising piston pump operating with overpressure activated injection valve, on the contrary to the above, the volumetric flow rate of the injection is determined by the delivery .flow rate of the volumetric pump, while the actual time and period of the injection are determined by the closing time and period of the control element closing the back flow branch of the pump. In the up-to-date solutions, as control element, high speed electromagnetic valve is utilized. Such kind of solutions are described for example in the publication document EPA-O 193 788

as well as in DE-PS 3719831. The common advantage of these solutions is in that they can realize extraordinary high injection pressure as well as short injection time.

Their common disadvantage is in, however due to the intermittent operation of the utilized piston pumping elements, the pump driving is depend on the speed of rotation of the engine and as a consequence, the characteristics of the injection change together with the speed of rotation of the engine. Therefore, at low speed of rotations the injection is unfavourable slow and the quality of carburation is not satisfactory.

In the up-to-date diesel and petrol engines having direct injection, in the whole range of the speed of rotation high injection pressure, short injection time and extraordinary fine carburation are requested. However,these requirements are not fulfilled perfectly by the known solutions.

Summary of the Invention

The aim of the invetion is partly to eliminate the disadvantages of the known fuel injection systems, partly to develop a fuel injection system being able to ensure simultaneously the high injection pressure, the short injection time and injection characteristics being independent from the speed of rotation of the engine as well.

The invention is based on the recognition that if the known overpressure activated injection valve is fed by volumetric pump of continuous feeding e.g. by screw pump instead of piston pump element of intermittent feeding, in this case, the pump driving - consequently the delivery flow rate of the pump - can be independent from the speed of rotation of the internal combustion engine and so, only the operation of the control valve should be synchronized with the operation of the internal combustion engine.

Further considerable recognition is in that if the fuel injection system has always maximal flow rate, in this case instead of piston pump elements having extremely tight fit, the screw pumps with essentially loose fit can be well utilized as well.

An other essential recognition is in that the pump operation for the injection system with constant delivery flow rate is very advantageous, as the pump can be developed for hydrodynamical lubrication, for reflectionsfree operation of the delivery pressure lines to the injection valves, while the jet nozzle of the carburettor can be planned for

forming optimal jet and drop size. The mentioned facts make possible essentially longer lifetime, exact feeding as well as better formation of mixture considering the known solutions.

The main task to be solved by fuel injection system for feeding the fuel into an internal combustion engine comprising a volumetric pump of continuous feeding, one or more overpressure activated injection valves and control valves. In the sense of the invention to the delivery side of the pump direct or indirect one or more overpressure activated injection valves and one or ore control valves are in parallel connected.

In a preferred embodiment the pump is screw pump or gear pump.

In a futher preferred embodiment according to the invention to the delivery side of the pump the overpressure activated injection valves are connected through the fuel distributor.

It is also a preferred embodiment in which it has an electrically controlled control valve of needle valve execution closing the inlet with its endface.

In another preferred embodiment, it has an electrically controlled control valve of sleeve execution closing the inlet with its mantle surface.

It is also a preferred embodiment in which it consists of an electrically controlled sleeve closing valve connected in parallel with the opening valve of the same execution closing the inlet with their mantle surfaces.

Brief Description of the Drawings

The invention is described in detail with the aid of the enclosed drawing presenting the embodiment of the solution according to the invention by way of example, in which:

Fig. 1 is a block diagram of the possible embodiment of the fuel injection system according to the invention;

Fig. 2 illustrates a block diagram of an other possible embodiment of the fuel injection system;

Fig. 3 shows a block diagram of another possible embodiment of the fuel injection system;

Fig. 4 is a structural diagram of a possible embodiment of the pump and control valve of the fuel injection system according to the invention;

Fig. 5 shows the structural diagram of an other possible embodiment of the control valve of the fuel injection system, while;

Fig. 6 is a structural diagram of a possible embodiment of the pump and control valve of the fuel injection system according to Fig. 2.

Description of the Preferred Embodiments

Fig. 1 is a block diagram of the possible embodiment of the fuel injection system according to the invention. To the delivery side lb of the volumetric pump 1 of continuous feeding, an overpressure activated injection valve 2 and the inlet 3a of the control valve 3 being open in the starting position and preferably electrically closable, are connected. The suction side la of the pump 1 and the outlet 3b of the control valve 3 are connected to the fuel tank 4.

In the arrangement according to the Fig. 1 the fuel flow delivered by the pump 1 from the fuel tank 4, flows through the control valve 3 being open in the starting position and flows back to the fuel tank 4. As the circulation can be maintained by means of low pressure, the injection valve 2 remains closed. If the control valve 3 is closed, then due to the volumetric delivery characteristics, on the delivery side lb of the pump 1 the pressure will be quickly increased, as a consequence, the injection valve 2 opens and activates the injection. If the control valve 3 is again open, in this case the pressure on the delivery side lb drops down, the injection valve 2 closes and so the injection will be finished.

Fig. 2 illustrates a block diagram of an other possible embodiment of the fuel injection system. Its mechanism and operation are different from the solution according to Fig. 1 in the fact that the control valve 3 consists of a closing valve 31 being open in the starting position, connected parallel with the opening valve 32 being closed in the starting position.

In this arrangement the injection is activated by closing the closing valve 31, and finished by opening the opening valve 32. The period of the injection is equal to the time interval from closing to opening, but as the closing and opening do not take place by means of the same valve, in this solution, shorter injection times can be realized than the switching time of the valves. For resetting the starting position, first the closing valve 31 should be opened, and then the opening valve 32 should be closed.

Fig. 3 shows a block diagram of another possible embodiment of the fuel injection system. This solution is different from the embodiment according to Fig. 1 in the fact that to the delivery side lb alternately other injection valve 2 is connected by the fuel distributor 5, so one pump 1 can supply with fuel more cylinders of the internal combustion engine. The fuel distributor 5 can be of mechanical operation, e.g. rotary distributor or of electric execution, for example before each injection valve 2 an electromagnetic valve is arranged and connected in series. These embodiments are well known in itself.

Fig. 4 is a structural diagram of a possible embodiment of the pump and control valve of the fuel injection system according to the invention. The pump 1 and the control valve 3 are arranged in common injection housing 6. The pump 1 in the present embodiment is a double screw pump consisting of a driving shaft 7a and a driven shaft 7b. To the delivery side lb of the pump 1 the fuel delivery connection 8 for joining up the injection valve 2 and inlet 3a of the control valve 3 are connected. The control valve 3 in the present formation is an electromagnetically controlled needle valve. The inlet 3a of the control valve 3 is closed by the endface 3c of the control valve 3. The electric coil 9 is arranged around the control valve 3 so that its magnetic field closing through the armature 3d of disc formation formed from magnetizable material, arranged at the end of the control valve 3 and affects with closing direction force to the control valve 3. The suction side la of the pump 1 and the outlet 3b of the control value 3 are connected to the fuel tank 4.

In this solution the pump 1 driven on the shaft 7a through the suction side 1 a sucks continuously fuel, that is forwarded through the control valve 3 being open in starting positon to its outlet 3b. As this flow can be maintained by low pressure, the injection valve 2 connected to the delivery side lb of the pump 1 through the fuel delivery connection 8 remains closed. To activate injection, current is driven through the coil 9, so the control valve 3, i.e. its inlet 3a will be closed. In consequence of continuous

feeding of the pump 1 on the delivery side lb of the pump 1 quick pressure increase comes into being which opens the injection valve 2 and as a result, the injection activates. To finish the injection the current in the coil 9 will be switched off, the control valve 3 opens and, on the delivery side lb of the pump 1 the pressure suddenly drops down, then the control valve 3 closes, and by this means the injection comes to the end.

Fig. 5 shows the structural diagram of an other possible embodiment of the control valve of the fuel injection system. On the two sides of the control valve 3 of sleeve execution electric coils 9a and 9b are arranged so that the magnetic field of the coil 9a closing through the housing of the control valve 3 affects a force to close it, while the magnetic field of the coil 9b affects a force to open it. In this execution, the control valve 3 is open in starting position, then to activate the injection, current impulse is driven into the coil 9a , the mantle surface 3e of the control valve 3 closes the inlet 3a and as a result, the injection starts. In order to finish the injection, current impulse is switched to the coil 9b on the effect of which the control valve 3 opens, the pressure on the delivery side lb of the pump 1 drops down and the fuel gets forward the fuel tank 4 through the outlet 3b.

Fig. 6 is a structural diagram of a possible embodiment of the pump and control valve of the fuel injection system according to Fig. 2. In the present embodiment the pump 1 is a gear pump to its delivery side lb through the fuel delivery connection 8 the injection valve 2, and in parallel with this a magnetisable closing valve 31 of sleeve execution being open in starting position, and also a magnetizable opening valve 32 of sleeve execution being closed in starting position are connected through the common inlet 3. The pump 1, the closing valve 31 and the opening valve 32 are arranged in common injection housing 6. The closing valve 31 and the opening valve 32 by means of their mantle surfaces 31 c and 32c close the inlet 3a. The common outlet 3b of the closing valve 31 and opening valve 32, and the suction side la of the pump 1 are connected to the fuel tank 4. The operation of the closing valve 31 and the opening valve 32 is ensured by the electric coils 9c and 9d, their resetting into the starting position are taken place by means of prestressed springs 10a and 10b supported by their ends.

In this execution, to start the injection current is driven through the coil 9c and the closing valve 31 will be closed while for finishing the injection, current is driven through the coil 9d and the opening valve 32 will be opened. For resetting the

starting position, firstly the current in the coil 9c should be switched off and the spring 10a opens the closing valve 31, then the current in the coil 9d should be switched off, and the spring 10b closes again the opening valve 32.

The advantage of the embodiment according to the invention in comparison to the execution operating with electromagnetically controlled injection valve fed by constant pressure is in that it is suitable for realizing essentially higher injection pressure as well as essentially shorter injection time.

The main advantage of the embodiment according to the invention is in, in comparison to the known high pressure fuel injection system operating with oveφressure activated injection valves and fed by piston pump element, controlled by closing the back flow branch, that the injection flow rate can be independent from the speed of rotation of the engine and as a result, it can be optimal chosen in the whole operation range of the engine.

The fuel injection system has some other advantages. As the pump can be operated always by maximal delivery flow rate, the allowable leaking waste can be approximately 50-times higher than in case of piston pump elements driven by the engine requiring perfect operation on the starting speed of rotation, i.e. on about 1/50 of the nominal value.

The production tolerance of the pump element and its allowable wear can be essentially higher, resulting cheaper production and longer lifetime.

It is also considerable advantage that the pump can be executed for hydrodynamic lubrication condition reducing thereby the abrasive load of the pump element to a great extent. Thanks to the high speed of rotation of the pump, during the injection the necessary high impulse power can also be supplied by means of inertial energy of the pump driving, and so high injection pressure can be produced at favourably low driving power as well. Thanks to the constant delivery flow rate of the pump, the injection valves and the feeding delivery pressure lines in the whole working range can be fitted reflectionsfree. By means of reflectionsfree operation, even in case of long delivery pressure lines as well as of short injection times, proper feeding and timing can be ensured.

In addition to the above, thanks to the constant delivery flow rate, the requested injection features, such as jet form, penetration depth, fineness of carburation, by means of simple injector nozzle can be realized.