EP1131552B1 - Fuel injection valve for internal combustion engines - Google Patents

Abstract

A fuel injection valve for intermittent injection of fuel into the combustion chamber of a diesel or other form of internal combustion engine. The valve achieves a shorter than usual injection valve member, while avoiding valve member oscillation but retaining precise closing by implementing a solenoid controlled piston that controls movement of the valve. The piston in turn is acted upon by fuel system pressure from a high pressure feed line and from a control chamber, alternatively, depending upon the position of an actuating element. The control piston has an annular land that faces the control chamber and the piston is connected to the high pressure feed line through a tight sliding fit in a piston guide bore establishing a leak gap. A relief chamber is formed between the outlet side of the gap and the land. When the injection valve is open, the land reduces fuel flow from the relief chamber into the control chamber. As a result, fuel pressure in the relief chamber rises compared to that in the control chamber.

Description

The invention relates to a fuel injection valve for intermittent fuel injection in the combustion chamber of an internal combustion engine according to the preamble of claim 1. This Injection valve can for example in so-called common rail injection systems Diesel engines are used.

Fuel injection valves of this type are known, for example, from the patents EP 0 262 539, DE 196 50 865, EP 0 603 616 or US 5 685 483 are known. In these known fuel injection valves the opening and closing movement of the injection valve member is controlled by Control of the control room pressure in a control room above a control piston, with the the injection valve member is operatively connected. At the end of its opening movement, the injection valve member stopped by a mechanical stop.

In EP 0 603 616, the injection valve member is multi-part and long. The length of the injector member is depending on the application of the injection system for a certain engine type depending on the engine design. In this known solution, the stop is in a distance from the top of the injector member. This causes a swing the free, upper end of the injection valve member after stopping its opening movement. This vibration causes undesired, imprecise closing movements of the injection valve member at the end of the injection process.

In EP 0 262 539 the injection valve member is also long. The opening movement of the injection valve member is by a stop surface between the upper end of the spool and a bottom of a Koibenführungteiles stopped inside the control room. With this arrangement, the above-mentioned vibration is avoided, but at the beginning of the Closing movement is the detachment of the injection valve member from the stop surface with uncontrollable temporal fluctuations, which in turn is an imprecise close cause.

The present invention aims at both avoiding swinging and detaching of the injection valve member in a precisely controllable manner, with which the injection processes can be realized with great reproducibility and accuracy.

This object is achieved according to the invention by the characterizing part of claim 1 Features solved.

The invention will now be explained in more detail below with reference to the drawings.

Fig. 1

eine erste Ausführungsform eines Brennstofteinspritzventils 1 im Längsschnitt;

Fig. 2

einen vergrösserten, partiellen Längsschnitt durch das Brennstoffeinspritzventil nach Fig. 1 mit der Anordnung zur präzisen Steuerung des Schliessvorganges des Einspritzventilgliedes ;

Fig. 3a, 3b

drei Phasen des zeitlichen Ablaufs der Öffnungsbewegung des Einspritzventilund 3c gliedes des Brennstoffeinspritzventils nach Fig. 1 und 2 in vergrössertem Massstab;

Fig. 4

ein partieller Längsschnitt einer zweiten Ausführungsform eines Brennstoffeinspritzventils 2;

Fig. 5

ein partieller Längsschnitt einer dritten Ausführungsform eines Brennstoffeinspritzventils 3;

Fig. 6

ein partieller Längsschnitt einer alternativen Ausführungsform 3a des Brennstoffeinspritzventils 3 von Fig. 5.

Show it:

Fig. 1

a first embodiment of a fuel injection valve 1 in longitudinal section;

Fig. 2

an enlarged, partial longitudinal section through the fuel injector of Figure 1 with the arrangement for precise control of the closing process of the injection valve member.

3a, 3b

three phases of the timing of the opening movement of the injection valve and 3c member of the fuel injection valve according to Figures 1 and 2 on an enlarged scale;

Fig. 4

a partial longitudinal section of a second embodiment of a fuel injector 2;

Fig. 5

a partial longitudinal section of a third embodiment of a fuel injector 3;

Fig. 6

5 shows a partial longitudinal section of an alternative embodiment 3a of the fuel injection valve 3 from FIG. 5.

1 is a fuel injection valve 1 via a high-pressure fuel connection 10 with a high-pressure delivery device for the fuel and via electrical connections 12 connected to an electronic control. The high pressure conveyor and the electronic Controls are not shown in the drawing.

The housing of the fuel injector 1 is designated 14. At the bottom is that Housing 14 screwed with a retaining part 16 designed as a union nut. The cap nut 16 presses a middle part 18 against a sealing surface 20 in a sealed manner is located between the housing 14 and the middle part 18. At the same time, the union nut 16 a nozzle body 22 on a sealing surface 24 between the middle part 18 and the nozzle body 22 pressed tightly. The nozzle tip 26 protrudes from the union nut 16.

The nozzle tip 26 has a nozzle needle seat 28 and a plurality of injection openings 30 Mistake. In the nozzle body 22 there is an axially adjustable nozzle needle forming an injection valve member 32 closely guided in a needle guide bore 34. The injection ports 30 of the Nozzle tip 26 can be closed by a lower end 36 of the nozzle needle 32.

On the face side, the nozzle needle 32 is in the middle part 18 in a piston guide bore 40 closely sliding, axially adjustable control piston 38 operatively connected. The movement of the Control piston 38 and thus also the nozzle needle 32 is by means of a solenoid valve 6 cooperating control device 8, which is further below with reference to FIG. 2nd are described in more detail.

The fuel is fed through the high-pressure delivery device via the high-pressure fuel connection 10 into a fuel supply bore 42 and from there into a downward bore 44 of the housing 14 promoted. The bore 44 opens into a made in the middle part 18 Bore 46. The bore 46 opens at the lower end into a nozzle body bore 48. In the middle part 18 connects a further, short bore 50 to the control device 8 with the bore 46. The nozzle body bore 48 opens into an annular space 52 in the nozzle body 22. From the annular space 52, the fuel reaches the nozzle needle seat 28 via passages (not shown) or to the injection openings 30.

At the upper end of the housing 14, a retaining screw 54 is screwed, which with the extended portion 56, which extends into a receiving bore 58, the solenoid valve 6 holds in the housing 14. The solenoid valve 6 is guided radially in the receiving bore 58.

2, the magnetic valve 6 has a magnetic body 60 in which a pole disk 62 is permanently installed. In the magnetic body 60 there is the coil 64, which is the electrical Connections 12 is connected to the electronic control, not shown. Also located a magnetic valve spring 66 and a spring tensioning element 68 are located in the magnetic body 60 Choice of the length of the spring tensioning element 68 is an optimal bias of the solenoid valve spring 66 set. The magnet armature 70 is firmly connected to the control valve stem 72, so that these two elements form a control valve 74.

A control body 78 is inserted in a bore 76 of the housing 14 and on the lower one Supported area 80 of the federal government 82. The control body 78 is preferably provided with a press or a narrow sliding seat in the bore 76, so that no significant Leakage can take place. However, other fuel-tight connections could also be used, for example can be realized using suitable sealing rings.

The control piston 38, which is guided in the piston guide bore 40 in the middle part 18 so as to slide closely has a groove 84 and a transverse bore 86 connected to the groove 84. The groove is 84 with the short bore 50, the transverse bore 86 with an axially made in the control piston 38

Bore 88 connected. A needle spring 90, a spring tensioning element, is located in the bore 88 92 and a control sleeve 94 guided in a narrow sliding manner in the control piston 38. Analogous to the solenoid valve spring 66, the spring tensioning element 92 serves to set a specific one Force of the needle spring 90. On the one hand, the needle spring 90 holds the nozzle needle in a known manner 32 in contact with the nozzle needle seat 28 when there is no injection and when there is no pressure Injection system. On the other hand, together with the fuel pressure, it pushes the upper end 96 of the control sleeve 94 continuously on the control body 78.

The control sleeve 94 has a longitudinal bore 98 opening into the bore 88. A first one Control bore 100 connects the longitudinal bore 98 to the control chamber 102. With a connection 104, the control chamber 102 is connected to the second control bore 106. By means of a Flat seat 108 between the control body 78 and control valve 74, the control bore 106 at de-energized solenoid valve 6 closed by the control valve 74 against the high system pressure held. The one emerging from the second control bore 106 when the control valve 74 is raised Fuel is, together with the leak fuel, which from the two guide holes 34 and 40 enters the annular space 110, by means of the bore 112 (FIG. 1) to known ones Returned way at low pressure of the high pressure conveyor.

As shown in FIGS. 1 and 2, the longitudinal axis 114 is the receiving bore 58 of the solenoid valve 6 with respect to the longitudinal axis common to the control piston 38 and the nozzle needle 32 116 disaxed. This is only in the dimensions of the housing 14 and shown Solenoid valve 6 required to have enough wall thickness for the high pressure bore 44 available to deliver. With larger dimensions of the housing 14, or smaller dimensions of the solenoid valve 6, the two longitudinal axes 114 and 116 can also match. The connection 104 in the control body 78 is omitted in this case.

2, 3a, 3b and 3c is located between the front side 118 of the control piston 38 and the underside 120 of the control body 78 an annular relief chamber 122 Control piston 38 has an annular web 124 which is not interrupted on the circumference. 3a, 3b and 3c, the two annular leak gaps 126 (between the control sleeve 94 and control piston 38) and 128 (between control piston 38 and middle part 18) for clarification the operation of the fuel injector 1 shown exaggerated.

The mode of operation of the fuel injection valve 1 is now based on FIGS. 1, 2, 3a, 3b and 3c as follows: when the solenoid valve 6 is energized with a current pulse, the control valve shaft moves 72 after a short time away from the flat seat 108 and gives the second control bore 106 free. The fuel control pressure in the connection 104, in the control chamber 102 and in the relief chamber 122 drops. On the one hand, this enables injection by lifting the control piston 38 and the nozzle needle 32 start away from the nozzle needle seat 28. The control piston moves 38 relative to the middle part 18 and the stationary control sleeve 94 upwards. on the other hand flows because of the now low control pressure through the first control bore 100 and through the Leakage gaps 126 and 128 fuel in the control room 102 because the fuel pressure in the Longitudinal bore 98, in the bore 88 and in the groove 84 significantly higher than the control pressure is. All of the fuel flowing into the control chamber 102 flows through the second control bore 106 onwards. This phase is shown in Fig. 3b.

It is advantageous if the fuel flow through the leakage gaps 128 and 126 is quantitative is smaller than that through the first control bore 100. This is achieved by realizing a tight sliding fit (with, for example, 1 to 3 micrometers of play) between the parts.

When the stroke of the nozzle needle 32 increases, the web 124 of the control piston 38 approaches the underside 120 of the control body 78. This means that the fuel flow from the relief chamber 122 throttled via the web 124 into the control chamber 102 and with a full stroke of the nozzle needle 32 greatly reduced. The pressure in the relief chamber 122 increases practically without a time delay and accordingly the fuel flow of the leakage gap 128 is also reduced. This full opening phase is shown in Fig. 3c. In the limit case, the web 124 forms the mechanical one Stroke stop of nozzle needle 32 and control piston 38. By selecting the outside and Internal diameter and the height of the web 124 can be a desired damping End of the opening movement can be achieved. In particular, the height of the web 124 can only amount to a few hundredths of a millimeter (for example 2 to 10 hundredths). That was realized causes very small volume of the relief space 122, despite the small inflow amount through the leakage gap 124, an instantaneous increase in the pressure in the relief space 122nd

Due to the design according to the invention with the web 124 at the upper end of the control piston 38 the free end of the spool of earlier designs no longer exists. On Swinging of this free end disappears with it. Since the pressure in the relief chamber 122 at End of the opening movement due to the throttling action of the web 124 and the leakage gap flow Rise over the leakage gap 128 without a time delay, a pressure equalization of force of control piston 38 and nozzle needle 32 guaranteed immediately. It also becomes a safe start of the closing movement possible. This happens when the current pulse to the Solenoid valve 6 is interrupted and the control valve stem 72, the second control bore 106 concludes. The disadvantages of the previous solutions are avoided.

Fig. 4 shows a partial longitudinal section of a second embodiment of a fuel injector 2. The elements not shown can be the same as those of the fuel injector 1 according to Fig. 1. Same elements as in Figs. 1 to 3c or those which are the exact perform the same function have been given the same numbers in FIG. 4.

The control valve stem 72 is located in the fuel injector 2 (and therefore not shown solenoid valve 6) on the same longitudinal axis 116 as the control piston 130 and the Nozzle needle 32. The control body 132 is in the middle part 18 in an analogous manner to the Fuel injector 1 installed. The control sleeve 94 of the fuel injector 1 is omitted in the fuel injector 2. A short bore 142 connects the groove 84 with the first Control bore 100. The control bore 100 opens into a made in the control piston 130 Longitudinal bore 136, which together with the bore 134 in the control body 132 and the Disk space 138 forms the control space 140. The needle spring 144 is in the lower tapered portion 146 of spool 130 in a region with low fuel pressure level. Two elements 148a and 148b position and tension the needle spring 144. The tapered one Section 146 presses on the end face of the nozzle needle 32.

By omitting the control sleeve 94, this area of the fuel injection valve 2 becomes simplified. Attaching the needle spring 144 outside the high pressure spool area enables a freer design of the volume of the control room 140 and the radial dimensioning of the web 124. On the other hand, a longer version of the middle part 18 are accepted. How the fuel injector works 2 is analogous to that of the fuel injection valve 1.

In an alternative, not shown embodiment of FIG. 4, the middle part 18 in the a lower thread on which the union nut 16 is screwed. With another The middle part 18 is screwed onto the housing 14. The middle part 18 points in this top a waistband. This embodiment is cheap if a long one Fuel injector must be used.

Fig. 5 shows a partial longitudinal section of a third embodiment of a fuel injector 3. Again, the elements not shown are the same as those of the fuel injector 1 according to Fig. 1. The same elements as in the preceding figures or those which perform exactly the same function, were also in Fig. 5 with the same digits as in the preceding Figures.

As in FIG. 4, the control valve stem 72 is located on the longitudinal axis 116. A disk-shaped one Intermediate plate 150 is located between the lower end of the housing 14 and the nozzle body 22. As in FIG. 1, the intermediate plate 150 and the nozzle body 22 held together by the union nut 16 in a sealed manner by means of the two sealing surfaces 20 and 24. The fuel supply bore 44 opens into a bore 152 in the intermediate plate 150. With a recess 154 and an oblique bore 156 is in the intermediate plate 150 the first control bore 100 is connected to the bore 152. On the other hand, the first control bore 100 in a on the longitudinal axis 116 in the intermediate plate 150 Bore 158. Bore 158 is with the second control bore 106 and with an in Control piston 160 connected bore 162 connected.

In an embodiment not shown in detail, a pressed-in can be used instead of the intermediate plate 150 Part, similar to the control body 78 of FIG. 2 or the control body 132 of FIG. 4, be used.

In contrast to fuel injection valves 1 and 2, control piston 160 is now one piece with the nozzle needle 32. A needle spring 164 is located together with the spring tensioning element 166, in the bore 162. The spring tensioning element 166 has a nose 167, which as Filler piece is used. Without the nose 167, the total volume of the control room consists of the fuel volume in the bores 158 and 162 depending on the dimensioning of these Elements unfavorably large. With the nose 167 it can be reduced. That being said the function of these elements the same as before.

The relief chamber 122 is in turn between that at the upper end of the control piston 160 existing web 124 and the needle guide bore 34. The leak fuel now flows during the injection process from the annular space 52 in the nozzle body 22 over the Leakage gap between control piston 160 and needle guide bore 34 in the relief chamber 122. The mode of operation of the fuel injection valve 3 is again analogous to that of the previous one Versions. The design of the fuel injector 3 is particularly simple.

A throttle bore 168 may be between bore 152 and bore 48, however after the inlet to the bore 156. This throttle bore 168 causes during the injection process a pressure drop of, for example, 5-10% of the standing pressure and causes a faster closing movement of the nozzle needle 32 in a known manner.

FIG. 6 shows an alternative embodiment of the fuel injection valve 3 from FIG. 5 6, the needle spring 164 was in a bore 170 of the Intermediate plate 150 installed. 5 has been omitted, although it is also in Fig. 6 either on the bottom or on the top of the needle spring 164 could be installed. The throttle bore 168 is now part of the intermediate plate 150. The operation of the fuel injector 3a is the same as that of the fuel injector Third

In further, not shown embodiments of the fuel injection valves 3 and 3a can a control body, analogous to the control body 78 of the fuel injector 1 or like that Control body 132 of the fuel injector 2, either in the housing 14 or in the Intermediate plate 150 can be installed. This control body can either only be the second Have control bore 106 or the first control bore 100.

If a control body with both control bores 100 and 106 is installed in the housing 14, the intermediate plate 150 of the fuel injector 3a can be shown with a dashed line Separation line 172 shown level are ended. in this case, the needle spring 164 of the side of the dividing line 172. Then the force of the needle spring 164 with transfer a narrow pin attached to the underside of the spring onto the needle piston 160, the underside 120 of the intermediate plate 150 facing the web 124 can be covered with a smaller bore than the bore 170 through which only the narrow pin protrudes. In this way you get, analogous to the design of the fuel injector 2 of FIG. 4, greater freedom in the radial dimensioning of the web 124.

The solenoid valve 6 can also be operated with the control valve stem 72 either as in FIGS. 5 and 6 on the longitudinal axis 116 or, as in the case of the fuel injector 1, out of alignment become.

Claims (14)

1. A fuel injection valve (1; 2; 3; 3a) for intermittent fuel injection into the combustion chamber of an internal combustion engine, with a housing (14), with a valve seat element (26) provided with injection apertures (30), with a longitudinally adjustable injection valve member (32) for closing or opening the injection apertures (30), with a control device for controlling the adjusting movement of the injection valve member (32), the control device having a longitudinally displaceable control piston (38; 130; 160) at least operatively connected to the injection valve member (32), which piston is acted upon by the fuel system pressure from a high-pressure feed line (42, 44, 46, 48) on the one hand and by the fuel control pressure in a control chamber (102, 104; 140; 158, 162; 170) on the other, the control chamber (102, 104; 140; 158, 162; 170) being connected by way of at least one first control aperture (100) to the high pressure feed line (42, 44, 46, 48), and the control pressure in the control chamber (102, 104; 140; 158, 162; 170) being controllable by opening or closing of at least one second control aperture (106), for which purpose an electrically controllable actuating element (6) is assigned to the control device, which element has an axially adjustable control valve element (72), which in its closed position seals off the second control aperture (106) and the opening movement of which, on activation of the actuating element (6), opens the second control aperture (106), and the control piston (38; 130; 160) is guided at its circumference by a tight sliding fit in a piston guide bore (40; 34) characterized in that the end of the control piston (38; 130; 160) facing the control chamber (102, 104; 140; 158, 162; 170) has an annular land (124), the control piston (38; 130; 160) is connected to the high-pressure feed line (42, 44, 46, 48) by way of the tight sliding fit in the piston guide bore (40; 34), and the tight sliding fit forms a leak gap (128), a relief chamber (122) is formed between the outlet side of the leak gap (128) and the land (124), and in that with the injection valve member (32) open, the land (124) reduces the flow of fuel from the relief chamber (122) into the control chamber (102, 104; 140; 158, 162; 170) by reducing the passage cross section, as a result of which the fuel pressure in the relief chamber (122) rises compared to the fuel pressure in the control chamber (102, 104; 140; 158, 162; 170).
2. The fuel injection valve (1; 2) as claimed in claim 1, characterized in that the control piston (38; 130) is fitted in a middle part (18), which is situated between housing (14) and nozzle body (22) and is pressed tightly against the housing (14) and the nozzle body (22) by at least one retaining part (16).
3. The fuel injection valve (1; 2) as claimed in claim 2, characterized in that the middle part (18) is provided with at least one high-pressure bore (46), which carries the fuel from the high-pressure bore (44) in the housing (14) to the high-pressure bore (48) in the nozzle body (22) and to the first control bore (100).
4. The fuel injection valve (1; 2) as claimed in claim 2, characterized in that the middle part (18) has passages (112), in order to drain off leakage fuel, which collects in an annular chamber (110) below the control piston (38; 130), at low pressure from the annular chamber (110).
5. The fuel injection valve (1; 2) as claimed in claims 1 or 2, characterized in that a control body (78; 132) is tightly fitted in the housing (14) or in the middle part (18), the control body (78; 132) is provided with an underside (120), which together with the land (124) forms the stroke limit of the control piston (38; 130).
6. The fuel injection valve (1; 2) as claimed in claim 5, characterized in that the control body (78; 132) is provided with the second control bore (106).
7. The fuel injection valve (1) as claimed in claim 1, characterized in that the actuating element (6) is axially offset in relation to a longitudinal axis (116) common to the control piston (38) and the injection valve member (32).
8. The fuel injection valve (3, 3a) as claimed in claim 1, characterized in that the control piston (160) is integral with the nozzle needle (32) and is guided in a guide bore (34) with tight slide fit in the nozzle body (22).
9. The fuel injection valve (3) as claimed in claim 8, characterized in that the control piston (160) is provided with a bore (162) containing a spring (164), acting in the closing direction of the injection valve member, and a spring tensioning element (166) for setting the required spring loading.
10. The fuel injection valve (3, 3a) as claimed in claim 1, characterized in that a restriction (168) is situated between the high-pressure bore (44) and the high-pressure bore (48), but downstream of the admission inlet (156) to the first control bore (100).
11. The fuel injection valve (3, 3a) as claimed in claim 1, characterized in that an intermediate plate (150) is located between housing (14) and nozzle body (22) and is tightly pressed against the housing (14) and the nozzle body (22) by a retaining part (16), the intermediate plate (150) has at least one fuel passage (152) from the high-pressure bore (44) to the high-pressure bore (48) and the second control bore (106).
12. The fuel injection valve (3, 3a) as claimed in claims 10 and 11, characterized in that the restriction (168) is situated in the intermediate plate (150).
13. The fuel injection valve (3, 3a) as claimed in claim 11, characterized in that the intermediate plate (150) has the first control bore (100).
14. The fuel injection valve as claimed in claim 11, characterized in that an underside (120) of the intermediate plate (150) forms the stroke limit of the control piston (160).

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