EP0068434B1 - High pressure injection system with ultrasonic atomization - Google Patents

Description

The invention relates to a high pressure injection system according to the preamble of claim 1.

Such injection systems are used, for. B. for injecting fuel into the combustion chamber of diesel engines, for injecting fuel into directly or indirectly injected gasoline engines, for operating gas turbines or combustion systems with light or heavy oil or for atomizing liquids in paint spraying systems and air humidification systems. In such arrangements, the liquid to be injected should be atomized as finely as possible. Ultrasonic energy can advantageously be used for this. So z. B. the atomization of fuels in carburetor systems in gasoline engines is already known. However, high-pressure injection is required, especially in the diesel engine. Such a high-pressure injection can, for. B. with an injection system according to US-A 4 000 852 according to the German laid-open publications 26 08108 and 23 04 525. In these systems, the fuel supplied by a mechanical pump is fed under high pressure to the injection nozzle, which is set into ultrasound vibrations by a piezoelectric vibration generator. A ball valve inside this arrangement prevents the fuel from dripping if the injector is not vibrated. In order to prevent the penetration of compression gases into the injection nozzle, an external ball valve is used in the known arrangement mentioned above according to DE-A 26 08 108, which is held on the housing by a compression spring. In this arrangement, however, the ball valve and spring are directly exposed to the pressures and temperatures in the combustion chamber, so that damage to these parts can be expected during long-term operation.

From the British patent application 20 41 249 an atomizing device is preferably known for an inhaler. This atomizing device has a tank for a liquid to be atomized, which is composed of two parts which can be displaced relative to one another, which are pressed together against the force of a spring and in this case actuate a pump, not shown, which is integrated in the tank. The liquid conveyed out of the tank is then atomized finely on an emitting surface, this emitting surface being set in vibration by means of an ultrasonic vibration generator. This atomizer is not a high pressure system and cannot be used in this form for a fuel injection system for diesel engines.

High pressure injection systems with ultrasonic atomization would, however, be advantageous over conventional mechanical injection systems if they could be adapted to the high loads during operation. So z. B. ultrasonic vibration generator can be controlled very low inertia, which poses problems in mechanical arrangements. In addition, such vibration generators can be controlled with simple electronic control devices. If the mechanical components of high-pressure injection systems could also be controlled and actuated with low inertia, an injection system with high efficiency could be achieved. For example, B. Diesel engines with already good fuel efficiency can be significantly improved in their performance, since higher speeds than previously could be achieved with such a system. Similar considerations also apply to injection systems in connection with other devices or systems mentioned above.

The invention is based on the object of realizing a high-pressure injection system with ultrasonic atomization which, in conjunction with electronic controls, on the one hand has a minimum of mechanical components, and on the other hand the output signal of the control with the least delay, ie. H. can follow with as little inertia as possible.

This object is achieved by the features specified in the characterizing part of patent claim 1.

According to the invention, the entire injection system is combined in a single structural unit, which is designed in the manner of a positively controlled piston pump with an inlet valve, a spray valve and a working piston. The previously known arrangement of injection valve and injection pump is thus summarized. All mechanical parts of the injection system according to the invention are driven by ultrasonic vibrators, which can be controlled by an electronic control with low inertia. With such an arrangement, high-pressure injection systems with the finest liquid atomization by ultrasound can be produced in a compact design.

According to a preferred embodiment of the invention, the pump chamber is penetrated by a control slide, which takes over the function of the valve body for the inlet valve and the spray valve. This control slide, which is common to both valves, is moved back and forth in its longitudinal direction by a second vibration generator. At its lower end, the control slide forms, together with a spray opening leading from the pump chamber of the arrangement, the spray valve, which can be closed by immersing the control slide in the bore of the spray opening. At the upper end of the pump chamber, the control slide has a taper with an edge in the region of an inlet opening leading from the pump chamber to a liquid supply. The edge of this taper forms with the bore of the inlet opening, the inlet valve, which is closed by immersing the outer diameter of the slide in the bore of the inlet opening. The liquid, e.g. B. a fuel is passed through a supply bore in the housing in the region of the inlet opening and the taper of the control slide into the inlet valve. The dimensions of the control slide valve are such that either the inlet valve is opened and the spray valve is closed during the reciprocating movement, or the spray valve is open and the inlet valve is closed. The control slide can be designed so that it shuts off both valves in its rest position, ie when the vibration generator is not actuated.

According to a preferred embodiment of the invention, the control slide is connected to its vibration generator via an elastic drive rod which is provided with a mass body. The elastic rod forms with the mass body and the mass of the control slide an oscillatory system, which, when tuned to the operating frequency of the ultrasonic vibration generator, multiplies the amplitude of the control slide oscillation relative to the amplitude of the oscillation of the oscillation generator in such a way that sufficient opening cross sections are achieved at the inlet and spray valve can and that the tolerance of the function-determining lengths of the two valves are also kept within reasonable limits.

The free end of the working piston, which is directly connected to the second vibration generator, also dips into the closed pump chamber.

The two ultrasonic vibration generators are screwed and pretensioned to the housing of the arrangement using two hollow screws. The two vibration generators can be known vibrators from power ultrasound technology, only the sound energy being passed on in the opposite direction through the hollow fastening screws.

The axes of the two moving parts, that is the working piston and the control slide, can advantageously be arranged in a V-shape with respect to one another in order to accommodate the space required in the vicinity of the spray valve and the sealing surface of the injection system to the system operated with it, and the resulting reaction force to keep the two transducers as small as possible.

The free end of the spool in the area of the spray valve is equipped with a radiation surface, e.g. B. a spherical cap and a spray cone that define the spray angle. The spray cone and the spherical end of the spool are the only parts that are directly affected by the conditions of the system operated with the injection system. In the case of a diesel engine, only these parts are subjected to the pressure and temperatures as well as the combustion gases in the cylinder head. The pressure and temperature effects can be easily mastered by the positive control of the control spool and the corresponding surface finish of these parts.

The function of the entire arrangement is ensured by an electronic control circuit. This control coordinates the movements of the control spool and the working piston in such a way that the working piston carries out a pressure stroke when the spray valve is open and carries out a suction stroke when the inlet valve is open. The movements of the spool and piston normally take place with a phase shift of 90 °. To control the injection quantity, however, this phase angle can be changed via the controller; for the same purpose it is possible to adjust the oscillation amplitude of the working piston, i. H. to change its stroke.

The advantages that can be achieved with the invention, in particular in the case of a diesel engine, are that the mechanically complex and expensive injection pump with all the drive elements necessary for its operation is eliminated. The connecting lines from the pump to the injection valves in the cylinder head are also eliminated. The mechanics of the pump and the running time of the pressure waves within the liquid to be atomized in the connecting lines have long stood in the way of the development of small, but powerful and therefore necessary fast-running diesel engines in the known prior art. The injection system according to the invention does not have these disadvantages, since the pump and the injection valve are integrated in one structural unit and can be mounted directly on the cylinder head of a diesel engine. Of course, this also applies to other devices and systems mentioned above.

The scarcity of raw materials and the legislation regulating exhaust gases for the purpose of environmental protection require engines with ever higher efficiency and lower pollutant emissions, whereby only engines with injection can meet these conditions. The processing of all parameters required for an optimal injection make an electronic process control necessary, which can carry out a precise calculation of the start of injection, injection duration and injection quantity per unit of time on the basis of a three-dimensional characteristic field. Until now, however, no systems were known which could convert the control output signal into the corresponding mechanical quantities with as little delay as possible. The injection system according to the invention allows all of these control parameters because it is low-inertia and, by changing the working piston stroke and / or the phase relationship between control spool and working piston movement, also permits control of the injection quantity per unit of time without the quality of the atomization of the liquid or the Fuel suffers because it is carried out with ultrasound energy.

Another advantage of the invention is that the electrical energy of the control output is converted directly into pressure energy without the interposition of actuators and pumps, so that the entire system manages with relatively few mechanical components.

• Figur 1 eine schematische Schnittdarstellung eines ersten Ausführungsbeispiels für ein Brennstoff-Einspritzsystem gemäß der Erfindung ;
• Figur 2 eine teilweise geschnittene Ansicht eines zweiten Ausführungsbeispiels für ein Brennstoff-Einspritzsystem gemäß der Erfindung ;
• Figur 3 einen detaillierten Teilschnitt durch das in Figur 2 gezeigte Brennstoff-Einspritzsystem.

Further refinements and advantages of the invention emerge from the subclaims in conjunction with the following description, in which two exemplary embodiments of a high-pressure injection system are explained in more detail with reference to the drawing. In the drawing:

• Figure 1 is a schematic sectional view of a first embodiment for a fuel injection system according to the invention;
• Figure 2 is a partially sectioned view of a second embodiment of a fuel injection system according to the invention;
• Figure 3 shows a detailed partial section through the fuel injection system shown in Figure 2.

The same reference numerals are used in the figures for the same or equivalent components, but a line is added to each of the figures 2 and 3. A pump chamber 12 is accommodated in the interior of a compact housing 1, in which a bore B1 is provided in one side wall. In this bore, a cylindrical working piston 2 is slidably mounted, the free end of which projects into the pump chamber 12 and the other end of which outside the housing with a vibration generator 3 supported thereon, e.g. B. superimposed circular ring piezo transducers, which, when electrically actuated, the working piston in the direction of its longitudinal axis, d. H. move back and forth in Figure 1 in the direction of the double arrow P1.

Two opposite walls of the pump chamber 12 are provided with two further coaxial bores B2 and B3 to form the inlet valve V1 and spray valve V2, in which a control slide 4 is slidably mounted and penetrates the pump chamber 12 perpendicular to the longitudinal axis of the working piston 2. The control slide 4 can be moved back and forth with a further oscillator 5 arranged outside the housing 1 in the two bores B2 and B3 in accordance with the double arrow P2.

The control slide 4 has at its free lower end, which projects into the bore B3, a spherical cap-shaped radiation surface 6. The bore B3 then widens conically to a radiation cone 7 and opens z. B. in the combustion chamber of a diesel engine.

The control slide is guided between the bores B2 and B3 through a slide bearing guide 8 in order to prevent the control slide from swinging sideways and thus to prevent damage to the inlet and spray valves.

In the area of the inlet opening B2, the control slide 4 has a taper 10 with a lower slide edge 10a, as a result of which control slides together with the taper and the bore form the inlet valve V1. A fuel supply line 9 opens into this valve and is guided in a housing bore into the region of the taper 10.

In the rest position of the spool 4, d. H. when the vibrator 5 is not actuated, both valves V1 and V2 are closed by the slide edge 10a sealing the inlet opening B2 of the inlet valve and the lower free end of the control slide sealing off the spray opening B3 of the spray valve V1 from the pump chamber 12.

If the control slide 4 is pushed into its lowest position in the spray opening B3 from this rest position, the inlet valve V1 is opened via a narrow inlet gap 11 between the slide edge 10a and the bore B2, while the shut-off valve remains closed. If the working piston 2 is now pulled to the right in the figure, fuel is sucked into the pump chamber 12 via the fuel feed line 9, the taper 10 and the inlet slot 11. If the spool is then brought into its uppermost position, the inlet valve V1 is closed and the spray valve is opened by opening a narrow spray slot 13 between the lower end of the spool and the bore B3. The working piston 2 now moved to the left displaces the fuel that has just been sucked in, which in this way can only escape through the spray valve V2. Now the control slide is brought back to its lowest position, the fuel upstream of the spherical radiation surface 6 being accelerated and emerging from the radiation cone 7 at high speed and atomized.

This completes a cycle consisting of drawing in and atomizing the fuel and restoring the above initial state so that a new cycle can begin.

The movements of the spool and piston of course take place continuously, z. B. in the form of a sine wave corresponding to the control by an electronic control system, not shown here. As can be seen from the above, the movements of the spool and working piston are shifted by 90 ° in relation to each other.

If the amount of fuel to be injected is to be varied, then either the amplitude of the oscillation of the working piston 2 can be changed: the above-mentioned phase relationship between the movements of the control slide and the working piston can also be changed. A combination of both options is of course possible.

FIGS. 2 and 3 show a constructive design of an injection system according to the invention, which is directly related to a lower sealing surface 23 on the housing 1 'can be placed on the opening for the injection valve of a conventional diesel engine. The attachment by means of screws or stud bolts is not shown.

FIG. 2 shows the overall view of the system with a cut-out section, which illustrates the attachment of a vibrator 3 'and the power transmission through it.

FIG. 3 shows an enlarged section through the arrangement according to FIG. 2.

The longitudinal axis of the working piston 2 'and control slide 4' run in a V-shape, the front free end of the working piston again protruding into the pump chamber 12 ', whereas the control slide 4' projects through the pump chamber 12 '. The pump chamber 12 'is small compared to that in the first embodiment. The working piston 2 'is sealed with a double seal 14 against the wall of the bore B1', between which a leak line 15 leading from the housing 1 'is provided. The working piston 2 'itself is passed through a hollow screw 16 and is only connected to this screw at the screw head. The hollow screw 16 clamps the vibrator 3 'to the housing 1' with an end piece 17 placed thereover. The vibrations of the vibrator are transmitted to the working piston 2 'via the end section 17 and the fastening screw 16.

Similarly, the spool 4 'is held in the housing 1'. The vibrator 5 'is clamped to the end section 18 by means of a hollow fastening screw 19 on the housing. With the screw head of the hollow screw 19, an elastic drive rod 21 is screwed in, which can be locked by means of a lock nut 25. The height of the drive rod can be adjusted with the lock nut 25 and the upper end of the drive rod provided with an adjusting thread 24. At the lower end of the hollow screw 19, the elastic drive rod 21 is connected to a cylindrical mass body 20, at the lower end of which the actual control slide 4 'is fastened. The guide 8 'for the control slide is designed together with the inlet valve V1' and the spray valve V2 'as an independent component, since it must be made of high quality material and machined with high precision. This insert part is inserted into a bore B2 'and clamped with a screw 22 located below the mass body 20. The control slide 4 'penetrates this inserted component and is sealed against this with a further double seal 26. The extended leakage line 15 opens into the space between this double seal 26. The insert part has a cover plate 27 which closes off the injection chamber 12 'at the top. The entire insert part is sealed off from the housing bore B2 'via a plurality of seals 28. Above this plate 27, the fuel supply line 9 'opens into the inlet valve V1' again in the area of the taper 10 'of the control piston.

By moving the control slide back and forth, the inlet valve V1 'with the inlet slot 11' and the spray valve V2 'with the spray slot 13' can be opened or shut off, as described above.

The operation of this injection system corresponds to that described above for the first embodiment. The mass body 20 with the elastic drive rod 21 has the task of forming an oscillatory mechanical system which must have the same natural resonance as the oscillator 5 'itself, so that an increase in amplitude of the control slide movement is generated.

In this injection system, only the radiation surface 6 'of the control slide 4' and the radiation cone 7 'come into contact with the combustion gases and the pressures and temperatures in the combustion chamber of the diesel engine.

Claims (12)

1. A high-pressure injection system for atomizing liquids by means of ultrasonics, in particular a fuel injection system for diesel engines, comprising a liquid feeding means (g) and a spraying valve (V2) whose valve body is electronically controlled by means of an electrically operated ultrasonic oscillator, characterized in that the injection system is designed as a modular unit of the force-controlled reciprocating pump type, comprising a pump housing (1), a pump room (12) contained therein, completely filled with liquid and having an inlet valve (V1) and a spraying valve (V2), and a working plunger (2) protruding into the pump room (12), and in that the valve bodies (10, 10a ; 4) of the inlet valve (V1) and of the spraying valve (V2) and the working plunger (2) are connected with electrically operated ultrasonic oscillators (3, 5) and the latter are operated by electronic control means for taking in liquid through the inlet valve (V1) and for spraying liquid through the spraying valve (V2).

2. The injection system according to claim 1, characterized in that the pump room (12) has an inlet opening (B2) for the injection valve (V1) and a spraying opening (B3) for the spraying valve (V2), which have assigned to them a common distributing slide valve (4) as a valve body for the inlet and spraying valves (V1, V2) which is connected to one oscillator (5) for reciprocally opening and closing the inlet and spraying valves.

3. The injection system according to claim 2, characterized in that the distributing slide valve (4) is directed in a guide means (8) in the pump room (12) between the injection valve (V1) and the spraying valve (V2).

4. The injection valve according to either of claims 2 and 3, characterized in that the distributing slide valve (4) has, in the area of the inlet opening. (B2), a tapered portion (10) with a slide edge (10a) facing the pump room (12) by means of which the inlet opening can be released by releasing an inlet gap (11) for taking liquid into the pump room, or can be blocked off from the pump room.

.5. The injection system according to any of claims 2 to 4, characterized in that the distributing slide valve (4) closes off the inlet valve (V1) and the spraying valve (V2) in its position of rest when the oscillator (5) is not activated.

6. The injection system according to any of claims 2 to 5, characterized in that the free end of the distributing slide valve (4) has a radiating surface (6) in the area of the spraying valve (V2) for superfine atomization of the liquid.

7. The injection system according to any of claims 2 to 6, characterized in that the distributing slide valve (4'), in order to increase the oscillation amplitude thereof, is connected to the oscillator (5') via an elastic driving rod (21) bearing a mass body (20), the mechanical properties of said driving rod being coordinated with the working frequency of the oscillator (5').

8. The injection system according to any of claims 2 to 7, characterized in that the longitudinal axes of the working plunger (2') and the distributing slide valve (4') are arranged in a V shape.

9. The injection system according to any of the above claims, characterized in that the inlet and spraying valves (V1, V2) are controlled in a phase of 180° and the working plunger (2) is controlled in a phase of 90° with respect to the inlet valve (Vi).

10. The injection system according to any of claims 2 to 9, characterized in that the phase of the oscillations of the working plunger (2) and the distributing slide valve (4) common to the inlet and spraying valves (V1, V2) is 90°.

11. The injection system according to either of claims 9 and 10, characterized in that the phase relations of the oscillations of the working plunger (2) and the valve bodies (distributing slide valve 4) for the inlet and spraying valves (V1, V2) may be varied in order to vary the amount of liquid to be injected.

12. The injection system according to any of the above claims, characterized in that the oscillation amplitude, i. e. the stroke of the working plunger (2), may be varied in order to vary the amount of liquid to be injected.

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