EP0267203A1

EP0267203A1 - Injection nozzle for internal combustion engines

Info

Publication number: EP0267203A1
Application number: EP19870902308
Authority: EP
Inventors: Gottfried Haider
Original assignee: Voestalpine Metal Forming GmbH
Current assignee: Voestalpine Metal Forming GmbH
Priority date: 1986-04-25
Filing date: 1987-04-23
Publication date: 1988-05-18
Also published as: WO1987006650A1

Abstract

Un injecteur pour moteurs à combustion interne, en particulier des moteurs diesel, est pourvu d'un pointeau de soupape qui est introduit dans un corps (1) d'injecteur, s'ouvre contre la force d'un ressort et se présente sous la forme d'une canule (9), ainsi que d'un piston de commande (14) guidé à l'intérieur de la canule (9), cette dernière coopérant avec au moins une ouverture d'injection (6), et le piston de commande (14) libérant les ouvertures d'injection supplémentaires (7) en cas de dépassement d'une pression prédéterminée. La canule (9) comporte des passages traversants radiaux (12) qui, lorsque ladite canule (9) repose sur son siège, débouchent dans l'espace de travail (13) du piston de commande (14). L'espace de travail (13) du piston de commande (14) peut être alimenté en carburant sous pression et l'alimentation en carburant de l'espace de travail (13) du piston de commande (14) peut être coupée avant d'atteindre la pression d'injection maximale.An injector for internal combustion engines, in particular diesel engines, is provided with a valve needle which is introduced into an injector body (1), opens against the force of a spring and is present under the form of a cannula (9), as well as a control piston (14) guided inside the cannula (9), the latter cooperating with at least one injection opening (6), and the piston control (14) releasing the additional injection openings (7) in the event of a predetermined pressure being exceeded. The cannula (9) has radial through passages (12) which, when said cannula (9) rests on its seat, open into the working space (13) of the control piston (14). The working space (13) of the control piston (14) can be supplied with pressurized fuel and the supply of fuel to the working space (13) of the control piston (14) can be cut off before reach the maximum injection pressure.

Description

Injection nozzle for internal combustion engines

The invention relates to an injection nozzle for internal combustion engines, in particular diesel engines, with a valve needle designed as a hollow needle and guided in a nozzle body and opening against a spring force, and a control piston guided inside the hollow needle, the hollow needle cooperating with at least one injection opening and the control piston releases additional injection openings when a predetermined pressure is exceeded.

Such a known injection nozzle has a hollow needle which, after lifting off over a predetermined stroke, opens radial bores of a piston guided in the interior of the hollow needle and, after these radial bores are released, enables injection via additional injection openings. The inner piston is supported against the hollow needle by means of a spring, whereby according to another embodiment, after the hollow needle has been lifted off, the inner piston is raised against the force of such a spring and in this way opens up the additional spray openings. With such a configuration, additional spray openings are released as a function of a predetermined path of the hollow needle and, in the event of the internal control piston being raised by the fuel pressure, counter to the force of a spring. The release of additional spray holes for full load is essentially due to the fact that small spray holes must be arranged at low speeds in order to achieve good atomization. Such small spray holes would lead to a correspondingly high injection pressure and correspondingly longer spraying time at full load, so that many suggestions have been made, in particular for high speeds, of opening different spray hole rows one after the other or connecting a second spray hole row. In order to ensure an effective connection of the second stage even at full load and high speed. This may normally only open at approximately half the maximum injection pressure and the level of this injection pressure must be determined by a corresponding spring force. In the known designs, this would lead to spring dimensions which can no longer be accommodated easily in the nozzle body and, moreover, would lead to heavy wear due to strong needle blow.

The invention now aims to provide an embodiment of the type mentioned in the introduction, in which the additional spray holes are only released at a relatively high injection pressure and the additional spray holes with low inertia can be released reproducibly at adjustable times. To achieve this object, the injection nozzle according to the invention essentially consists in that the hollow needle has radial openings which, when the hollow needle is lowered into its seat, open into the working space of the control piston, that the working space of the control piston can be pressurized with fuel and that the fuel is supplied to the working area of the control piston can be switched off before the maximum injection pressure is reached. The fuel is fed into the working space of the control piston in that the hollow needle has radial openings which open into the working space of the control piston when the hollow needle is lowered to its seat. The fact that the working space of the control piston can be pressurized with fuel makes it possible to dispense with the use of springs which negatively influence the inertia and that the supply of fuel to the working space of the control piston can be switched off before the maximum injection pressure is reached an exact definition of the point in time at which the additional spray holes are released by pressing on the control piston. The switching off of the supply of fuel to the working space of the control piston can be selected at any time and it can be achieved in this way that the additional Spray openings are only released at an arbitrarily high injection pressure in order to inject even at full load and high speed in such a way that an operating mode below the smoke limit is ensured.

According to a preferred embodiment of the invention, the procedure is such that the working space of the control piston and the pressure space of the hollow needle can be supplied with fuel under pressure from a common pressure medium source, so that the use of a separate pressure medium source for controlling the control piston can be dispensed with.

In a particularly advantageous manner, the design according to the invention is such that the radial openings in the hollow needle throttle or block the fuel supply to the work space when the hollow needle is raised. In this embodiment, the lifting of the hollow needle enables the fuel supply to the working chamber of the control piston to be shut off. From the beginning of the throttling of the fuel supply to the working space of the control piston or the closing of the fuel supply to this space, the desired pressure difference can build up due to the further increasing fuel pressure, which subsequently opens up the additional spray holes. The setting of the desired differential pressure and thus the time of opening of the second spray openings can also be achieved in that a pressure relief valve is switched on in the fuel supply line to the work area, as corresponds to a further embodiment.

A particularly advantageous regulation of the injection process as a function of engine parameters, such as, for example, the speed, can be carried out by switching on a throttle valve which can be controlled as a function of an engine parameter, in particular the engine speed, in the fuel supply line to the work area. The throttle The valve can be designed in a preferred manner as a control slide, the control slide depending on a motor parameter, in particular the speed, can be acted upon by pressure, preferably the backing pump pressure, and releases a variable flow cross section in the feed line to the work space.

A structurally particularly simple design for supplying the working space of the control piston with fuel under pressure and supplying the nozzle needle space can be achieved in that the fuel supply line to the working space of the control piston opens into an annular recess in the nozzle body which is separate from the fuel supply to the hollow needle.

The closing of the additional spray openings by the control piston can be ensured in a simple manner in that the control piston interacts with a valve closing member, in particular a ball, arranged in the area of the nozzle needle tip. In all the aforementioned _^ cases, the additional injection openings are printed by the Kraftstoff¬ itself, held closed without the help of springs, and by selection of the Absteuerzeitpunktes for supplying or limiting the pressure of the supplied fuel volume in the working space of the control piston can be the beginning of the additional Injection can also be shifted in the direction of high injection pressures. When using balls as the closing element, the production is considerably cheaper since no double fits are required. An adjustable stop can advantageously be provided for the stroke of the control piston, for which purpose a particularly adjustable pressure pin is preferably arranged in the hollow needle at the end facing away from the nozzle needle tip.

Through the use of fuel under pressure or a backing pump pressure that changes depending on the speed If a control slide is used, the activation of the additional spray openings can be controlled as a function of the injection pressure and speed, so that better atomization in the transition area and overall a lower injection pressure with a shorter spraying time at high speed can be achieved.

The invention is explained in more detail below with reference to exemplary embodiments shown in the drawing. 1 shows a longitudinal section through the nozzle body of an injection nozzle according to the invention with a pressure relief valve; FIG. 2 shows an enlarged longitudinal section of the lower part of FIG. 1; 3 shows an enlarged longitudinal section of the pressure limiting valve of FIG. 1; 4 shows a longitudinal section analogous to FIG. 2 of a second embodiment of an injection nozzle according to the invention; 5 shows an enlarged longitudinal section of the nozzle base; 6 shows a longitudinal section of the lower part analogously to FIG. 2 of a further embodiment according to the invention with a throttle valve controlled as a function of the speed; Fig. 7 is a view in the direction of arrow VII of Figure 6 with the section unfolded. Fig.

8 shows the course of the injection pressure versus camshaft speed for a single-stage injection nozzle according to the prior art and for an injection nozzle according to the invention in the embodiment according to FIGS. 1, 2 and 3, and the embodiment according to FIG. 6; Fig.

9 shows the course of the injection duration over camshaft speed for a single-stage injection nozzle according to the prior art and for an injection nozzle according to the invention in the embodiment according to FIGS. 1, 2 and 3.

The nozzle body of an injection nozzle according to the invention is designated by 1 in FIG. Fuel passes through a bore 2 into two separate lines 3 and 4, line 3 leading to the working space of a control piston and fuel via line 4 into an annular recess 5 of nozzle body 1 and from there to injection openings 6 and 7 in Area of the nozzle needle tip is guided. In line 3, a pressure relief valve 8 is switched on, which will be described in more detail later with reference to FIG. 3. With 9 a hollow needle is designated, which is acted upon by the force of a spring 10 in the closed position.

In Fig. 2 the lower part of the nozzle body 1 is shown enlarged, the reference numerals have been retained. As can be clearly seen in FIG. 2, the line 3 also opens into an annular recess 11 in the nozzle body 1. In the region of the recess 11, the hollow needle 9 has radial bores 12 which lead into the working space 13 of a control piston 14, which is located inside the hollow needle 9 is guided and can be formed from a plurality of cylindrical individual pistons with a graduated diameter, as shown in FIG. 2, or in a simple manner without grading the diameter. At the end facing away from the nozzle needle tip, the hollow needle 9 has an in particular adjustable pressure pin 15, which limits the stroke of the control piston 14 via an additional piston 16. As is clear from FIG. 2, the hollow needle 9 interacts with the injection openings 6, while the control piston 14 interacts with the injection openings 7 via a valve closing member 17 designed as a ball. The same pressure prevails in lines 3 and 4 at the beginning of the injection process and the control piston 14 is pressed into the closed position by the fuel entering the working space 13. When a certain injection pressure is exceeded, the hollow needle first lifts up against the force of the spring acting on it and releases the injection openings 6, while the control piston continues to close the injection openings 7. Before the maximum injection pressure is reached, the pressure limiting valve closes the further fuel supply in line 3 to the working space 13 of the control piston 14, while the pressure in line 4 continues to rise, as a result of which a sufficient pressure difference between the working space 13 and that in the area of the nozzle needle tip is formed located control piston surface of the control piston 14 lifts from the game guided ball 17 and this relieved suddenly. Due to its elasticity and the high flow rate, the ball 17 now lifts off its seat and thereby releases the additional spray holes 7. The beginning of the opening of the additional spray holes can thus be precisely controlled by a corresponding design of the pressure limiting valve, whereby by applying pressure to the working space 13 of the control piston 14 with fuel, a spring for acting on the control piston 14 can be dispensed with, as a result of which in addition to smaller dimensions of the hollow needle 9, a gentler needle impact can also be achieved.

In Fig. 3 the pressure relief valve 8 is shown in detail, fuel passes under pressure into the lines 3 and 4. Via a device 18, fuel enters a space 19 and acts on an actuator 20, which by the force of a Spring 21 is acted upon. With increasing pressure, the actuator 20 is displaced in the direction of the arrow 22, whereupon the valve closing member 24 stops the further supply of fuel into the line 3 to the working space of the control piston via a stop 23. The closing pressure of the valve can be varied accordingly by suitable dimensioning of the valve 8.

4 shows a second embodiment of an injection nozzle according to the invention, the reference symbols being retained. In this embodiment, the annular recess 11 forms a control edge with respect to the bores 12 of the hollow needle 9, which means that in this variant a pressure relief valve in the line 3 to the working space 13 of the control piston 14 can be dispensed with. Injection pressure is again present in both lines 3 and 4, and if a certain pressure is exceeded, the hollow needle 9 lifts off its seat and releases the injection openings 6. To Covering a predetermined stroke, the bores 12 grind the recess 11 to the work space, as a result of which no further pressure build-up takes place and after the formation of a pressure difference, the control piston 14 also lifts off its seat and thereby releases the additional injection openings 7. In the illustration shown in FIG. 4, the hollow needle 9 is lifted from its seat and the bores 12 are practically completely overlapped by the recess 11, while the control piston, which in this embodiment is made from one piece and into which Nozzle needle tip is fitted which has not yet opened injection openings 7.

Fig. 5 shows an enlarged view of the nozzle bottom with the raised hollow needle 9, wherein the valve closing member designed as a ball 17 is still pressed by the control piston 14 onto its seat. The use of a ball as a valve closing element brings advantages in terms of production technology, since a double fitting of the valve closing element can be dispensed with.

In the modified embodiment shown in FIG. 6, a control slide 25 is switched into the line 3 to the working space 13 of the control piston 14 and can be acted upon by a control pressure, in particular the backing pump pressure, via a line 26. The control slide has a circumferential groove 27, which is designed as a control edge for the line 3, and a spring 28 is arranged in its interior. By acting on the control spool 25 with the speed-dependent backing pump pressure, it becomes possible to control the connection of the injection openings 7 as a function of the injection pressure and speed. The structure of the injection nozzle corresponds to the embodiment shown in FIG. 2, except for the use of the control slide 25 instead of the pressure limiting valve. In the illustration shown in FIG. 7, the control slide is again designated 25. In addition, cylindrical pins 29 for fitting the nozzle body 1 are also shown. When the control spool is cut out, the circumferential groove 27, which is designed as a control edge in line 3, can be clearly seen. In the embodiment shown in FIGS. 6 and 7, the control slide 25 blows over the line 3 when the backing pump pressure increases, as a result of which no further pressure build-up takes place in the control chamber 13 of the control piston 14 and, after a pressure difference has been formed, the injection openings 7 are released by the control piston 14.

8 shows the course of the injection pressure over the camshaft speed. Curves a and b correspond to a single-stage injection nozzle according to the prior art with a small (a) or large (b) control rod travel. A small control rod travel corresponds to the partial load range and a large control rod travel corresponds to the full load range. The dashed curves c and d are achieved with an injection nozzle according to the invention with a pressure relief valve according to FIGS. 1, 2 and 3, while curve e is obtained in a configuration with a control slide according to FIGS. 6 and 7. S denotes the switching point of the connection of the additional injection openings. It can be clearly seen that in an injection nozzle according to the invention with reduced maximum injection pressures, sufficiency can be found.

It is clear from the injection duration shown in FIG. 9 over the camshaft speed, the curves a - d corresponding to those in FIG. 8, that a shorter injection duration can also be achieved with an injection nozzle according to the invention.

Claims

Claims:

1. Injection nozzle for internal combustion engines, in particular diesel engines, with a valve needle, which is guided in a nozzle body (1) and is designed as a hollow needle (9) and opens against a spring force, and a control piston (14) guided inside the hollow needle, the hollow needle ( 9) cooperates with at least one injection opening and the control piston (14) releases additional injection openings when a predetermined pressure is exceeded, characterized in that the hollow needle (9) has radial openings (12) which, when the hollow needle (9) is lowered on its seat, Open into the working chamber (13) of the control piston (14), that the working chamber (13) of the control piston (14) can be pressurized with fuel and that the supply of fuel to the working chamber (13) of the control piston (14) is reached before it is reached the maximum injection pressure can be switched off.

2. Injection nozzle according to claim 1, characterized in that the working chamber (13) of the control piston (14) and the pressure chamber

(5) the hollow needle (9) can be acted upon by fuel under pressure from a common pressure medium source.

3. Injection nozzle according to claim 1 or 2, characterized in that the radial openings (12) of the hollow needle

(9) throttle or close the fuel supply to the working space (13) of the control piston (14) when the hollow needle (9) is raised.

4. Injection nozzle according to claim 1 or 2, characterized gekenn¬ characterized in that a pressure relief valve (8) is switched on in the fuel supply line (3) to the working space (13).

5. Injection nozzle according to claim 1 or 2, characterized gekenn¬ characterized in that in the fuel supply line (3) for Working space (13) a throttle valve which is controllable as a function of an engine parameter, in particular the engine speed, is switched on.

6. Injection nozzle according to claim 5, characterized in that the throttle valve is designed as a control slide (25) that the control slide depending on a motor characteristic, in particular the speed, with pressure, preferably the backing pump pressure, can be acted upon and a variable flow cross section in releases the inlet line (3) to the work space (13).

7. Injection nozzle according to one of claims 1 to 6, characterized in that the fuel supply line (3) to the working space (13) of the control piston (14) in a separate from the fuel supply (4) to the hollow needle (9) ring-shaped recess (11 ) opens into the nozzle body (1).

8. Injection nozzle according to one of claims 1 to 7, characterized in that the control piston (14) with an in

Area of the nozzle needle tip arranged valve closing member (17), in particular a ball, cooperates.

9. Injection nozzle according to one of claims 1 to 8, characterized in that a particularly adjustable pressure pin (15) is arranged in the hollow needle (9) at the end facing away from the nozzle tip.