JPH03121251A - Injection device for diesel engine - Google Patents

Abstract

PURPOSE: To carry out more precise quantity adjustment to an injection device in which additional fuel is fed into a chamber just before a valve seat in a nozzle needle valve under an excessive pressure before the discharge of an injection valve is initiated by connecting an additional fuel conduit to a return conduit through a controllable closing valve. CONSTITUTION: Fuel fed from a working chamber 3 in an injection pump constituting member 11 reaches a chamber 14 in an injection nozzle 11 by way of a hole 9 of a nozzle holder 10, and is injected from a jet hole when a nozzle needle 13 is pushed up overcoming a spring force. In this arrangement, a transfer pump 16 supplies additional fuel from an additional fuel tank 15 into the camber 14 through a pressure chamber 17, a passage 22 in the nozzle holder 10 and a check valve 23. The passage 22 can be connected thereto with a return conduit 26 through the intermediary of a control valve 24. Further, the control valve 24 is controlled by a control unit 25, and accordingly, when the control valve 24 is closed, kinetic energy of the additional fuel is converted into potential energy so as to produce impulsive pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an injection device for a diesel engine, in which diesel fuel flows from an injection pump through an equal pressure valve and a first conduit to a nozzle needle valve seat of an injection nozzle. a non-return valve which is supplied to the front chamber and in which the additional liquid is opened under overpressure via a second conduit into the chamber in front of the nozzle needle valve seat in the direction towards this chamber before the discharge of the injection pump is started; of the type in which diesel fuel and additional liquid are then injected together under the pressure of an injection pump.

PRIOR ART Such an injection device is known, for example from EP-A 282,819. According to this known configuration, the second
The additional liquid formed by the fuel is conveyed into the chamber upstream of the nozzle via a separate pump, the conveying pawl being defined by a solenoid valve. Although in this known arrangement the additional liquid is supplied to the chamber upstream of the nozzle before the injection pump starts dispensing, the pressure generated in the injection conduit from the injection pump to the nozzle has to be overcome, so that the additional liquid is supplied by the conveying pump to the chamber upstream of the nozzle. The soaking pressure must be relatively high. Such pumps with high pressure conveyance pose risks of cavitation and erosion, and this type of arrangement is relatively expensive. The type of metering of additional liquid by means of a solenoid valve connected in the supply conduit from the pump to the chamber upstream of the nozzle becomes relatively imprecise and delayed. This is because the path from the solenoid valve to the chamber in front of the nozzle needle valve seat is critical. Therefore, even if one ignores the fact that the conveying pump is quite expensive, it is not possible to accurately determine the R value for each injection cycle.

Problems to be Solved by the Invention The object of the invention is to enable accurate metering with simple means.

Means for solving the problem According to the invention, the second conduit is a supply conduit (hammer pipe) for impulsively supplying the additional liquid.
r pipe) or connected to such a supply conduit, which supply conduit is connected to a pressure source for the additional liquid via a non-return valve which is opened in the direction towards the supply conduit and a nozzle. A check valve, which opens in the direction towards the chamber in front of the needle valve seat, communicates with a controllable closing valve, which in the open position connects the supply conduit to the return part and which is closed. The solution is to generate a pressure impulse by converting the kinetic energy of the additional liquid flowing past into potential energy.

Effects of the Invention Due to the configuration of the invention, the conveying pump only has to convey the additional liquid up to the check valve and therefore has to overcome the closing force of the check valve and the pressure occurring in the injection conduit from the injection pump to the nozzle. disappears. The pressure required for the conveying pump is therefore relatively low. As long as the controllable dynamic closing valve is open, the additional liquid is returned to the tank with high flow energy. If the controllable closing valve closes abruptly, high pressure shocks occur in the supply line between the controllable closing valve and the check valve that opens in the direction toward the supply line. This pressure impulse opens the check valve which opens in the direction towards the chamber in front of the nozzle needle valve seat, and the additional liquid is conveyed into the chamber in front of the nozzle needle valve seat. The action of the supply conduit is thus utilized to convert kinetic energy into potential or static energy when it is abruptly closed. In this case, the pressure in the first line, kept constant by the equal pressure valve, is overcome and a portion of the diesel fuel conveyed via the first line is pushed back in the direction of the injection pump, so that the additional liquid is added to the diesel fuel in the chamber before the nozzle. Diesel fuel and additional liquid are then injected together during the subsequent discharge stroke. Closing of the controllable closing valve causes a pressure impulse in the supply line between the controllable closing valve and the non-return valve opening in the direction towards the supply line, so that the pressure impulse causes the nozzle needle valve seat to The point in time at which the non-return valve, which opens in the direction towards the chamber in front of the chamber, is opened and the additional liquid flows into this chamber is precisely defined. According to the invention, the amount of additional liquid supplied is determined by the closing period of the controllable closing valve, so that the conditioning of the additional liquid can be carried out very precisely. In particular, this allows the conveying pump for the additional liquid to work with extremely low pressures, so that risks of cavitation and erosion in the conveying pump are largely avoided.

According to an advantageous embodiment of the invention, the supply conduit opens into a channel of the nozzle holder, the end of which facing the nozzle opening in the direction towards the chamber upstream of the nozzle needle valve seat. It is closed by a stop valve and the other end of the passageway is closable by a controllable shut-off valve. The pressure impulses that occur in the supply line when the controllable closing valve is closed therefore act directly in this channel. In this case, the opening of the supply conduit into the channel is preferably arranged closer to the controllable closing valve than to the check valve, so that the effect of the closing of the controllable closing valve is improved. is improved.

Advantageously according to the invention, the supply conduit is connected via a check valve, which is opened in the direction towards the supply conduit, to a pressure chamber to which a conveying pump for conveying the additional liquid is connected,
This pressure chamber is connected to a return line via a pressure holding valve. This has the advantage that the pressure for supplying the additional liquid into the supply conduit and thus the kinetic energy of the additional liquid remains constant in the closing valve open state, which reduces the pressure that would occur if the controllable closing valve were closed. The shock has a constant height.

According to the invention, the controllable closing valve is preferably constructed as a solenoid valve which is controlled by an electrical control unit. In this case, the controllable closing valve is preferably controlled as a function of the operating characteristics of the diesel engine, in particular the load and/or rotational speed. Since the pressure impulse occurs in the supply conduit suddenly and without delay, in this way the supply amount of additional liquid can be varied within a short period of time as required from injection cycle to injection cycle.

The additional liquid may be a selective fuel, such as an alcohol fuel, which changes or improves the ignition conditions of the diesel fuel. Moreover, the additional liquid may be water, whereby the nitrogen oxide emissions of the engine are reduced.In the drawings, the injection pump component is designated by l;
In this case, the reference numeral 2 designates the pump piston and the reference numeral 3 designates the working chamber of the pump piston. Diesel fuel is sucked in from the tank 4 via a conveying pump 5 and a filter 6 and is fed into the working chamber 3 in the usual manner. The working chamber 3 is connected to the nozzle holder 1 via an equal pressure valve 7 and a conduit 8.
It is connected to hole 9 in 0. Furthermore, reference numeral 11 designates the injection nozzle and reference numeral 12 designates the valve seat of the nozzle needle 13. From the hole 9 the diesel fuel reaches the chamber 14 in front of the nozzle needle valve seat 12.

The additional liquid is transferred from the additional liquid tank 15 to the transfer pump 1.
6 and transported into the pressure chamber 17.

A return conduit 18 to the tank 15 is connected to this pressure chamber 17, and a pressure retaining valve 19 is connected in this return conduit. The pressure within the pressure chamber 17 is kept constant by this pressure-holding valve.

The supply conduit 20 is connected to the pressure chamber 17 via a check valve 21 which is opened in the direction towards the supply conduit, and this supply conduit communicates with a passage 22 in the nozzle holder 10. It is connected to a chamber 14 in front of the nozzle needle valve seat 12 via a check valve 23 that opens in the direction toward the nozzle needle valve seat 12. A controllable shutoff valve 24 is arranged at the end of the channel 22 facing away from the injection nozzle l, in which case the supply conduit 20 is connected between the check valve 23 and the controllable shutoff valve 24. It is connected to 22.

The controllable closing valve 24 is a solenoid valve controlled by an electrical control unit 25.

If the controllable closing valve 24 is opened, additional liquid is returned from the supply conduit 20 via the return conduit 26 into the tank 15 with high kinetic energy. If the controllable closing valve 24 is abruptly closed, the kinetic energy of the additional liquid flowing through the supply conduit 20 and the return conduit 26 is converted impulsively into potential or static energy. In this case supply conduit 20 and passage 2
2, a pressure impulse occurs which is very large, taking into account the high kinetic energy of the additional liquid flowing past, and opens the check valve 23, so that the additional liquid flows into the chamber 14 in front of the nozzle needle valve seat. reach The opening 27 of the supply conduit 20 into the channel 22 is arranged close to the controllable closing valve 24, so that the closing of the controllable closing valve has a direct effect.

The control unit 25 controls the closing of the controllable closing valve 24 as well as the opening of the closing valve. The closing time of the controllable closing valve 24 is thus determined by the control unit 25 and thereby the amount of additional liquid supplied to the chamber 14 is regulated. A pressure impulse or pressure increase occurs in the passage 22 and the supply conduit 20 between the check valve 21 and the controllable closing valve 24 . This is because the check valve 21 prevents a return flow to the pressure chamber 17.

[Brief explanation of drawings]

The drawings schematically illustrate embodiments of the invention. DESCRIPTION OF SYMBOLS 1... Injection pump component, 2... Pump piston, 3... Work chamber, diesel fuel tank, 5...
Transfer pump, 6...filter, 7...equal pressure valve, 8.
...Diesel fuel conduit, 9...hole, IO...nozzle holder, 11...nozzle, 12...valve seat, 13
... Nozzle needle, 14 ... Chamber, 15 ... Additional liquid tank, 16 ... Transfer pump, 17 ... Pressure saw chamber, 18.26 ... Return conduit, 19 ... Pressure holding valve, 20
... Supply conduit, 21.23 ... Check valve, 22 ... Passage, 24 ... Closing valve, 25 ... Control unit, 27
···Aperture

Claims (1)

[Claims] 1. An injection device for a diesel engine, wherein diesel fuel is supplied from an injection pump to a chamber in front of a nozzle needle valve seat of an injection nozzle via an equal pressure valve and a first conduit, and , the additional liquid is supplied in a predetermined quantity via a second conduit under overpressure to a chamber in front of the nozzle needle valve seat through a non-return valve which is opened in the direction towards this chamber before the discharge of the injection pump begins. in which the diesel fuel and additional liquid are then injected together under the pressure of an injection pump, the second conduit is a supply conduit (
20) or connected to such a supply conduit (20) and which is opened in the direction towards the supply conduit (20) by means of a check valve (21) for the additional liquid. between a check valve (23) connected to the source (16) and opened in the direction towards the chamber (14) in front of the nozzle needle valve seat (12) and a controllable closing valve (24); in communication with the supply conduit (20
) is connected to the return part (26) and is adapted to generate a pressure impulse by converting the kinetic energy of the additional liquid flowing past into potential energy when it is closed. Injection device for. 2. The supply conduit (20) is connected to the passage (
22), and the end of this passage facing the nozzle (11) is connected to the chamber (12) in front of the nozzle needle valve seat (12).
14), which is closed by a check valve (23) that opens in the direction toward the passageway, and the other end of the passage is a controllable closing valve (
24. The injection device according to claim 1, wherein the injection device is closable by 24). 3. Opening (2) of supply conduit (20) into passageway (22)
7) is controllable, whereas the check valve (24) is controllable by the check valve (24).
3) The injection device according to claim 2, wherein the injection device is arranged closer than to 3). 4. The supply conduit (20) is connected to a pressure chamber (17) to which a transfer pump (16) for conveying additional liquid is connected via a check valve (21) that is opened in the direction toward the supply conduit. 4. The injection device according to claim 1, wherein the pressure chamber is connected to the return line (18) via a pressure-holding valve (19). 5. A closing valve (24) that can control the amount of additional liquid supplied.
) Claims 1 to 3 defined by the closure period of
The injection device according to any one of the preceding items. 6. The controllable closing valve (24) is connected to the control unit (25)
6. The injection device according to claim 1, wherein the injection device is configured as a solenoid valve controlled by a solenoid valve. 7. Injection device according to claim 1, wherein the controllable closing valve (24) is controlled in dependence on operating characteristics of the diesel engine.