EP0690222A1 - Injection device to inject fuel in a reciprocating internal combustion engine - Google Patents

Abstract

The fuel injection device has a difference dosing piston (3) coupled to a drive medium which is under a pressure of 2000 bar and more and a control piston (4), displaced between two end positions by an electrically-operated hydraulic drive. The control piston has guide elements (41,42) for the drive medium, via which the fuel is transferred from the fuel pump (8) to the dosing space (33) and from the dosing space to the engine cylinder (52,53). Pref. the guide elements ae provided by channels or bores providing a simultaneous connection with the fuel pump and with the injection jets in a given position. <IMAGE>

Description

The invention relates to an injection device for the fuel injection of a reciprocating piston internal combustion engine according to the preamble of claim 1. With such injection devices, the fuel is injected into the cylinders under high pressure, for example in diesel engines.

The injection process must be carried out in a very specific cycle, ie at the right time and with the right amount. Conventional fuel injection systems with cam control are mechanically complex and also, for example, only partially flexible with regard to the optimization of fuel consumption and emissions. Similar injection systems, such as that according to the preamble of the invention, are known for passenger cars and trucks. However, all these systems are not suitable for operation with heavy oil, they only have a purely time-controlled fuel quantity metering and the high-pressure fuel storage is not protected against leakage.

The object of the invention is to provide an injection device with which the injection process is improved. According to the invention, such an injection device is characterized by the features in the characterizing part of independent claim 1. The dependent claims relate to advantageous developments of the invention.

In the improved injection device according to the invention, the injection of the fuel is controlled and monitored with a control piston and a metering piston.

The control piston is advantageously actuated and switched hydraulically in one direction via an electric hydraulic valve. If a mechanical drive of the control piston is desired for reasons of redundancy, this is also possible.

A corresponding arrangement can also be provided in the other direction, or the actuation in the other direction can be carried out with the pressurized fuel, with a separate control hydraulic system with control oil or with a spring.

The control piston controls both the inlet of the fuel to the metering piston and the outlet of the fuel from the metering piston chamber to the injection nozzle of the cylinder of the engine. The controls, e.g. the grooves and / or bores are arranged such that in both positions of the control piston, both the inflow of fuel to the metering piston and the outflow of fuel to the injection valve of the cylinder are open.

To start the injection, the control piston must be lifted from its seat, so that a direct connection from the high-pressure fuel reservoir to the injection nozzle is created. In the metering piston, which is carried along by the fuel during the injection process, is located in this connection path. Its path, multiplied by its cross-sectional area, represents exactly the injected fuel volume. This path is recorded with an inductive displacement sensor, for example, processed in the electrical control and sent as an injection end signal to the pilot valve. This in turn initiates the return movement of the control piston, so that its seat seals, the connection from the high-pressure fuel reservoir to the injection valve is interrupted, and the injection is thus ended.

A volumetric injection is thus realized with the metering piston. For example, despite partially blocked or washed-out injection nozzles, the injection volume can be kept constant, which would not be possible with a purely time-controlled injection. Together with an ignition pressure measuring device, the injection pressure according to the invention can be used to regulate the ignition pressure to the permissible value so that the cheapest fuel consumption is always achieved.

The dosing piston fulfills another task. If the control fails or the control piston locks, it limits the injection volume to the maximum volume provided during operation. In such a case, the electrical control can determine via distance measurement on the metering piston that the injection has been too large. The next and further injections can be suppressed and displayed.

If such damage occurs, the pressure in the injection line can build up because the control piston does not seal absolutely against the fuel under cooking pressure of up to 2000 bar and more. To prevent this, the line can be relieved with a relief control valve will. This prevents uncontrolled injection. Furthermore, broken injection nozzle heads can also be indirectly determined with the metering piston displacement sensor, because in such a case the metering piston speed during the injection process becomes greater than usual. With this signal, the control electronics can be caused to suppress the fuel injection into a cylinder with a defective injection nozzle and, if necessary, to reduce the total engine load and / or to display the error with a display device.

A lead value must be added to the signal of the metering piston travel meter so that the fuel supply with the control piston can be closed in time, which enables clean regulation and prevents the injection volume required by the speed controller from being exceeded. When the engine is started, this lead value is a stored, approximate value. After the start, this value is continuously adapted to the current conditions by an adaptive control.

It is easily possible to make an injection device with a single metering piston for several control pistons, in which the supply of fuel to the metering piston chamber is to be carried out in series over all control pistons. With such an arrangement, only fuel can flow into the metering piston chamber if all fuel channels to the injection nozzles are blocked. On the other hand, the injection can only take place when all control pistons are open.

The new injection device creates an extraordinarily leak-proof, volumetrically precise injection device.

The injection device works with a metering piston driven by the pressurized fuel, which is designed as a differential piston. The back of the dosing piston is connected to and pressurized with the fuel, which is under high pressure of up to 2000 bar and more. A control piston is e.g. a hydraulic drive, which can be electrically controlled, moves back and forth between two end positions. The control piston has guide elements for the fuel, via which the fuel is fed from the fuel pump to the metering chamber, or from the metering chamber to the cylinder of a reciprocating piston internal combustion engine. The controls, i.e. Grooves and holes are advantageously arranged so that never, i.e. in no position there is a connection to both the high-pressure fuel pump and the injector of the cylinder at the same time.

Embodiments of the invention, i.e. the injector and its function are described and explained below with reference to the schematic figures.

Fig. 1

eine erste Einspritzvorrichtung schematisch und teilweise geschnitten;

Fig. 2

eine zweite Einspritzvorrichtung schematisch und teilweise geschnitten, die sich von derjenigen von Fig. 1 durch die andere Ausführungsform des Steuerkolbens unterscheidet.

Show it:

Fig. 1

a first injector schematically and partially cut;

Fig. 2

a second injector schematically and partially cut, which differs from that of FIG. 1 by the other embodiment of the control piston.

1 and 2 show schematically and partially in a section the injection device 1, which is fed by the high pressure pump 8 and the accumulator 81 with fuel. The input channel 2 for the fuel branches into the channel 21 to the rear of the as Differential piston formed metering piston 3 and in the main channel 22, with which fuel is guided via the groove 41 of the control piston 4 to the inlet channel section 23 in the metering piston chamber 30. When the control valve 61 of the control hydraulics 6, which has an inlet and a return, is actuated with control oil that is under pressure, the end face 43 of the control piston 4 is moved downward. The pilot valve receives its control commands from the control electronics 7, which ensures that the fuel injection process takes place at the right time and with the right amount. For example, signals from an angle sensor 71 on the crankshaft of the engine are sent to the control electronics. The transmitter 72, which works for example inductively, emits signals to the control electronics 7 about the position of the metering piston 3. This makes it possible to determine and change the amount of fuel injected per injection process.

As the control piston moves downward, the connection between the main channel 22 and the input channel section 23 is first interrupted. Thereafter, the output channel 24 is connected to the injection channel 25, which leads to the injection nozzle 51 of the cylinder 53 of the diesel engine, via the groove 42 in the control piston 4. The metering piston 3 is moved by the pressure exerted by the fuel via the channel 21 on the rear side 31 of the metering piston. The fuel is injected into the cylinder space 52 of the engine 5.

If the pilot valve 61 is closed and the return line for the control oil is opened, the control piston 4 is pressed upward by the fuel pressure acting on the end face 44 of the control piston 4 and the spring force. The fuel supply to channel 25 is interrupted and the end of injection is brought about.

At the control piston according to FIG. 1, for example, five sealing points permanently seal against the fuel under high pressure. The most important sealing point, namely the one with the connection to the injection nozzle, is designed as a seat valve 45, so that the line 25 to the injection nozzle is not pressurized between the individual injection processes. The valve seat 45 is very tight in the closed state. Uncontrolled injection can thus be prevented. In the case of the other seals 46, the tight fit of the control piston 4 is utilized and a small leakage flow of the fuel is accepted and returned to the fuel tank via the return channels 27.

Fig. 2 shows a control piston 4 'with only two sealing points 46', where only very small amounts of leakage occur. In this embodiment, three sealing points constantly seal against the fuel which is under high pressure. This version has a higher hydraulic efficiency than variant 1. The injector is also heated less thanks to the lower leakage currents.

If the control piston is blocked in any position, there is a relatively poor seal between channels 22 and 25. In order to avoid an undesired rise in pressure and subsequently undesired injections, the pressure in the channel 25 is reduced by opening the relief valve 80.

In order to obtain a long service life of the control piston 4, it is hardened on its surface. Any suitable hardening process can be used. Control piston and associated bushing can be designed so that they can be easily replaced when they are worn. So this sleeve can be used as a cone in the housing, which is the replacement of this Bush, together with the control piston, as a whole control unit enables and makes simple.

With one control piston, several injection nozzles of one cylinder of a reciprocating piston internal combustion engine can be controlled simultaneously. In particular when using a fast pilot valve 61, the control of the injection process can be adapted to the requirements of the engine at full and part load in the best possible way.

Several control pistons with the associated pilot valves and injection valves can also be arranged to form a metering piston. In this case, the individual injection nozzles of a cylinder can be controlled individually in terms of time.

The encoder 72 for the control electronics advantageously works inductively. However, other measuring systems that work capacitively, optically, magnetically or in any other way are suitable for monitoring and measuring the position of the metering piston. The influence of dead time, i.e. to minimize the delay of the system to the functional accuracy of the injection device, an adaptive injection volume control with an adaptive component can be provided.

The monitoring and control of the actual position and actual speed of the metering piston can be compared at any time with its target position and target speed.

Depending on the deviation, ie the difference between the setpoint and actual value, the electronics can deduce whether too much, too little fuel or the fuel is injected too quickly or too slowly. The size of these deviations can be used, for example, when a predetermined limit value is reached, to trigger an alarm, suppress injection of an affected cylinder and reduce engine performance.

In the examples shown, the control piston is driven in the closing direction with the high-pressure fuel, in one case additionally with a spring. Other types of drives can also be used to drive the control piston, e.g. a separate hydraulic drive also in the closing direction and not only in the opening direction. The control piston in the examples is described and shown as one piece. However, it is easily possible to manufacture the control piston from several pieces, possibly even from different materials or differently treated materials. The individual pieces can then be firmly connected to one another or can only be in constant contact with one another simply on the basis of the pressure and force conditions on the control piston. It is also conceivable to operate the control piston with a mechanical camshaft and hydraulic rod. However, this is only as redundancy for the case where the hydraulic drive is faulty or fails.

Injectors in diesel engines work with a fuel pressure in the range from 400 bar to over 2000 bar and the pressure in the hydraulic control circuit can work, for example, with a pressure in the range from 100 to 400 bar.

The injector as shown can be used for both diesel and heavy oil injection. This allows starting the cold engine with diesel oil and switching to heavy oil as soon as a higher operating temperature necessary for heavy oil is reached.

Claims (13)

Injection device (1) for fuel injection of a reciprocating piston internal combustion engine (5), with a metering piston (3) and a control piston (4) with guide elements (41, 42) for controlling the metering piston (3) and with a feed (2, 22, 23 ) for the fuel under pressure to the metering piston (3), characterized in that
the metering piston (3) is designed as a differential piston, the rear side (30) of which is continuously connected to the fuel supply (8, 81) via channels (21),
the control piston (4) has guide elements (41, 42) for the fuel and can assume two end positions in its bore, the inflow path (2, 22, 23) for the fuel to the front of the metering piston (3) for the first end position Fuel is open and the fuel channel from the front of the metering piston (3) to the injection nozzle (51) of the cylinder (52, 53) of the reciprocating piston internal combustion engine (5) is closed, and
in the second end position the connection of the inflow path (2, 2, 23) for the fuel to the front of the metering piston is closed and the fuel channel (24, 25) from the front of the metering piston (3) to the injection nozzle (51) of the cylinder (52, 53) of the reciprocating piston internal combustion engine (5) is open. Injection device (1) according to Claim 1, in which the guide elements (41, 42) on the control piston and the fuel channels (2, 22, 23; 24, 25) to be switched are arranged such that the fuel channel (2, 22, 23) from the accumulator (81) to the metering piston chamber (30) and the fuel channel (24, 25) from the metering piston chamber (30) to the injection valve (51) is open at the same time. Injection device (1) according to one of claims 1 or 2, with an electrical-hydraulic control (7; 6, 61) for the control piston (4). Injection device (1) according to claim 3, with a device (32, 72) for monitoring the current position of the metering piston (3) and for comparing the actual position and / or the actual speed of the metering piston (3) with a predetermined target Location and / or target speed. Injection device (1) according to one of Claims 1 to 4, which has one or more high-pressure pumps (8) and one or more pressure accumulators (81). Multiple injection device with a plurality of injection devices (1) according to one of Claims 1 to 5, for injecting fuel into a plurality of cylinders (52, 53) of an internal combustion engine (5). Multiple injection device according to claim 6, with a number of control pistons (4) which is greater than the number of metering pistons (3). Multiple injection device according to claim 7, with a single metering piston (3) for the plurality of injection nozzles (51) of a single cylinder (52, 53). Multiple injection device according to one of claims 7 or 8, which leads the fuel supply to the plurality of injection nozzles (51) of a cylinder (52), in succession, in series via guide elements (41, 42) of a plurality or all of the control pistons (4). Injection device according to one of claims 1 to 9, for injecting diesel and heavy oil into the cylinder (52) of a reciprocating piston internal combustion engine (5). Injection device according to one of claims 4 to 10 with an adaptive injection control (7; 32, 72; 6, 61) for the injection speed and / or the injection quantity on the basis of the comparison between corresponding actual and target values. Reciprocating piston internal combustion engine (5) with an injection device (1) according to one of Claims 1 to 11. Control piston (4) for an injection device (1) according to one of claims 1 to 11, or for the injection device (1) of a reciprocating piston internal combustion engine (5) according to claim 12, which has only two or three gap sealing areas (46) and a valve seat area (45) having.

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